publications
Publications by categories in reversed chronological order. Generated by jekyll-scholar.
2019
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ALMA 26 arcmin^2 Survey of GOODS-S at 1 mm (ASAGAO): Near-infrared-dark Faint ALMA Sources Yamaguchi, Yuki, Kohno, Kotaro, Hatsukade, Bunyo, Wang, Tao, Yoshimura, Yuki, Ao, Yiping, Caputi, Karina I., Dunlop, James S., Egami, Eiichi, Espada, Daniel, Fujimoto, Seiji, Hayatsu, Natsuki H., Ivison, Rob J., Kodama, Tadayuki, Kusakabe, Haruka, Nagao, Tohru, Ouchi, Masami, Rujopakarn, Wiphu, Tadaki, Ken-ichi, Tamura, Yoichi, Ueda, Yoshihiro, Umehata, Hideki, Wang, Wei-Hao, and Yun, Min S. \apj 2019 [Abs] [ads] [arXiv]
We report detections of two 1.2 mm continuum sources (S _1.2 mm \ensuremath∼ 0.6 mJy) without any counterparts in the deep H- and/or K-band image (i.e., K-band magnitude \ensuremath≳26 mag). These near-infrared-dark faint millimeter sources are uncovered by ASAGAO, a deep and wide- field (≃26 arcmin^2) Atacama Large Millimeter/submillimeter Array (ALMA) 1.2 mm survey. One has a red IRAC (3.6 and 4.5 \ensuremathμm) counterpart, and the other has been independently detected at 850 and 870 \ensuremathμm using SCUBA2 and ALMA Band 7, respectively. Their optical-to-radio spectral energy distributions indicate that they can lie at z \ensuremath≳ 3─5 and can be in the early phase of massive galaxy formation. Their contribution to the cosmic star formation rate density is estimated to be \ensuremath∼1 \texttimes 10^\ensuremath-3 M _☉ yr^\ensuremath-1 Mpc^\ensuremath-3 if they lie somewhere in the redshift range of z \ensuremath∼ 3─5. This value can be consistent with, or greater than, that of bright submillimeter galaxies (S _870 \ensuremathμm > 4.2 mJy) at z \ensuremath∼ 3─5. We also uncover three more candidate near-infrared-dark faint ALMA sources without any counterparts (S _1.2 mm \ensuremath∼ 0.45─0.86 mJy). These results show that an unbiased ALMA survey can reveal the dust-obscured star formation activities, which were missed in previous deep optical/near-infrared surveys.
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Color Dependence of Clustering of Massive Galaxies at 0.5 \ensuremath≤z \ensuremath≤2.5: Similar Spatial Distributions between Green Valley Galaxies and AGNs Lin, Xiaozhi, Fang, Guanwen, Cai, Zhen-Yi, Wang, Tao, Fan, Lulu, and Kong, Xu \apj 2019 [Abs] [ads]
We present a measurement of the spatial clustering of rest-frame UV- selected massive galaxies at 0.5 \ensuremath≤ z \ensuremath≤ 2.5 in the COSMOS/UltraVISTA field. Considering four separate redshift bins with \ensuremath∆z = 0.5, we construct three galaxy populations, i.e., red sequence (RS), blue cloud (BC), and green valley (GV) galaxies, according to their rest-frame extinction- corrected UV colors. The correlation lengths of these populations are confirmed to be dependent on their rest-frame UV color and redshift: UV redder galaxies are found to be more clustered. In all redshift bins, the GV galaxies generally have medium clustering amplitudes and are hosted within dark matter halos whose masses are more or less between those of RS and BC galaxies; and the clustering amplitude of GV galaxies is close to that of active galactic nuclei (AGNs) in the same redshift bin, suggesting that AGN activity may be responsible for transforming galaxy colors. After carefully examining their stellar masses, we find that the clustering amplitudes of galaxy samples with different colors are all similar once they have a similar median stellar mass and that the median stellar mass alone may be a good predictor of galaxy clustering.
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ALMA 200-parsec Resolution Imaging of Smooth Cold Dusty Disks in Typical z ∼3 Star-Forming Galaxies Rujopakarn, W., Daddi, E., Rieke, G. H., Puglisi, A., Schramm, M., Pérez-González, P. G., Magdis, G. E., Alberts, S., Bournaud, F., Elbaz, D., Franco, M., Ivison, R. J., Kawinwanichakij, L., Kohno, K., Narayanan, D., Silverman, J. D., Wang, T., and Williams, C. C. arXiv e-prints 2019 [Abs] [ads] [arXiv]
We present high-fidelity, 30 milliarcsecond (200-pc) resolution ALMA rest-frame 240 \mum observations of cold dust emission in three typical z ∼3 star-forming galaxies in the Hubble Ultra-Deep Field (HUDF). The cold dust is distributed within the smooth disk-like central regions of star formation (SF) 1 - 3 kpc in diameter, despite their complex and disturbed rest-frame UV and optical morphologies. No dust substructures or clumps are seen down to ≃1- 3 M_\odotyr^-1 (1σ) per 200-pc beam. No dust emission is observed at the locations of UV-emitting clumps, which lie ≃2-10 kpc from the bulk of SF. Clumpy substructures can contribute no more than 1-8 % (3σupper limits) of the total SF in these galaxies. The lack of SF substructures in our HUDF galaxies is to be contrasted with the multiple substructures characteristic of submillimeter-selected galaxies (SMGs) at the same cosmic epoch, each containing ∼10-30 % of their total SF. We find that individual substructures of SMGs are often as bright in the far- infrared as (or in some cases brighter than) our HUDF galaxies, suggesting that these SMGs originate from a class of disruptive event involving multiple objects at the scale of our HUDF galaxies. The scale of the disruptive event found in our HUDF galaxies, characterized by the lack of star-forming substructures at our resolution and sensitivity, could be less violent, e.g., gas-rich disk instability or minor mergers.
2018
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ALMA 26 arcmin^2 Survey of GOODS-S at One-millimeter (ASAGAO): X-Ray AGN Properties of Millimeter-selected Galaxies Ueda, Y., Hatsukade, B., Kohno, K., Yamaguchi, Y., Tamura, Y., Umehata, H., Akiyama, M., Ao, Y., Aretxaga, I., Caputi, K., Dunlop, J. S., Espada, D., Fujimoto, S., Hayatsu, N. H., Imanishi, M., Inoue, A. K., Ivison, R. J., Kodama, T., Lee, M. M., Matsuoka, K., Miyaji, T., Morokuma-Matsui, K., Nagao, T., Nakanishi, K., Nyland, K., Ohta, K., Ouchi, M., Rujopakarn, W., Saito, T., Tadaki, K., Tanaka, I., Taniguchi, Y., Wang, T., Wang, W. -H., Yoshimura, Y., and Yun, M. S. \apj 2018 [Abs] [ads] [arXiv]
We investigate the X-ray active galactic nucleus (AGN) properties of millimeter galaxies in the Great Observatories Origins Deep Survey South (GOODS-S) field detected with the Atacama Large Millimeter/submillimeter Array (ALMA), by utilizing the Chandra 7-Ms data, the deepest X-ray survey to date. Our millimeter galaxy sample comes from the ASAGAO survey covering 26 arcmin^2 (12 sources at a 1.2 mm flux-density limit of \ensuremath≈ 0.6 mJy), supplemented by the deeper but narrower 1.3 mm survey of a part of the ASAGAO field by Dunlop et al. Ofthe 25 total millimeter galaxies, 14 have Chandra counterparts. The observed AGN fractions at z=1.5{–}3 are found to be {90}_-19^+8% and {57}_-25^+23% for the ultra-luminous and luminous infrared galaxies with log {L}_{IR}/{L}_☉ = 12-12.8 and log {L}_{IR}/{L}_☉ = 11.5-12, respectively. The majority (̃2/3) of the ALMA and/or Herschel detected X-ray AGNs at z = 1.5-3 appear to be star-formation-dominant populations, having {L}_/ {L}_{IR} ratios smaller than the “simultaneous evolution” value expected from the local black-hole-mass-to-stellar-mass ({M}_{BH}-M _*) relation. On the basis of the {L}_ and stellar mass relation, we infer that a large fraction of star-forming galaxies at z=1.5{–}3 have black hole masses that are smaller than those expected from the local {M}_{BH}-M _* relation. This contrasts previous reports on luminous AGNs at the same redshifts detected in wider and shallower surveys, which are subject to selection biases against lower luminosity AGNs. Our results are consistent with an evolutionary scenario in which star formation occurs first, and an AGN-dominant phase follows later, in objects that finally evolve into galaxies with classical bulges.
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The [C II] emission as a molecular gas mass tracer in galaxies at low and high redshifts Zanella, A., Daddi, E., Magdis, G., Diaz Santos, T., Cormier, D., Liu, D., Cibinel, A., Gobat, R., Dickinson, M., Sargent, M., Popping, G., Madden, S. C., Bethermin, M., Hughes, T. M., Valentino, F., Rujopakarn, W., Pannella, M., Bournaud, F., Walter, F., Wang, T., Elbaz, D., and Coogan, R. T. \mnras 2018 [Abs] [ads] [arXiv]
We present ALMA Band 9 observations of the [C II]158 \ensuremathμm emission for a sample of 10 main-sequence galaxies at redshift z ̃ 2, with typical stellar masses (log M_\ensuremath⋆/M_☉ ̃ 10.0-10.9) and star formation rates (̃35-115 M_☉ yr^-1). Given the strong and well-understood evolution of the interstellar medium from the present to z = 2, we investigate the behaviour of the [C II] emission and empirically identify its primary driver. We detect [C II] from six galaxies (four secure and two tentative) and estimate ensemble averages including non-detections. The [C II ]-to-infrared luminosity ratio ([C II]/L_IR) of our sample is similar to that of local main-sequence galaxies (̃2 \texttimes 10^-3), and ̃10 times higher than that of starbursts. The [C II] emission has an average spatial extent of 4-7 kpc, consistent with the optical size. Complementing our sample with literature data, we find that the [C II] luminosity correlates with galaxies’ molecular gas mass, with a mean absolute deviation of 0.2 dex and without evident systematics: the [C II]-to-H_2 conversion factor (\ensuremathα _[C II] ̃ 30 M_☉/L_☉) is largely independent of galaxies’ depletion time, metallicity, and redshift. [C II] seems therefore a convenient tracer to estimate galaxies’ molecular gas content regardless of their starburst or main- sequence nature, and extending to metal-poor galaxies at low and high redshifts. The dearth of [C II] emission reported for z > 6-7 galaxies might suggest either a high star formation efficiency or a small fraction of ultraviolet light from star formation reprocessed by dust.
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GOODS-ALMA: 1.1 mm galaxy survey. I. Source catalog and optically dark galaxies Franco, M., Elbaz, D., Béthermin, M., Magnelli, B., Schreiber, C., Ciesla, L., Dickinson, M., Nagar, N., Silverman, J., Daddi, E., Alexander, D. M., Wang, T., Pannella, M., Le Floc’h, E., Pope, A., Giavalisco, M., Maury, A. J., Bournaud, F., Chary, R., Demarco, R., Ferguson, H., Finkelstein, S. L., Inami, H., Iono, D., Juneau, S., Lagache, G., Leiton, R., Lin, L., Magdis, G., Messias, H., Motohara, K., Mullaney, J., Okumura, K., Papovich, C., Pforr, J., Rujopakarn, W., Sargent, M., Shu, X., and Zhou, L. \aap 2018 [Abs] [ads] [arXiv]
Aims: We present a 69 arcmin^2 ALMA survey at 1.1 mm, GOODS- ALMA, matching the deepest HST-WFC3 H-band part of the GOODS- South field.
Methods: We tapered the 0″24 original image with a homogeneous and circular synthesized beam of 0″60 to reduce the number of independent beams - thus reducing the number of purely statistical spurious detections - and optimize the sensitivity to point sources. We extracted a catalog of galaxies purely selected by ALMA and identified sources with and without HST counterparts down to a 5\ensuremathσ limiting depth of H = 28.2 AB (HST/WFC3 F160W).
Results: ALMA detects 20 sources brighter than 0.7 mJy at 1.1 mm in the 0″60 tapered mosaic (rms sensitivity \ensuremathσ ≃ 0.18 mJy beam^-1) with a purity greater than 80%. Among these detections, we identify three sources with no HST nor Spitzer-IRAC counterpart, consistent with the expected number of spurious galaxies from the analysis of the inverted image; their definitive status will require additional investigation. We detect additional three sources with HST counterparts either at high significance in the higher resolution map, or with different detection-algorithm parameters ensuring a purity greater than 80%. Hence we identify in total 20 robust detections.
Conclusions: Our wide contiguous survey allows us to push further in redshift the blind detection of massive galaxies with ALMA with a median redshift of z = 2.92 and a median stellar mass of M_\ensuremath⋆ = 1.1 \texttimes 10^11 M_☉. Our sample includes 20% HST- dark galaxies (4 out of 20), all detected in the mid-infrared with Spitzer-IRAC. The near-infrared based photometric redshifts of two of them (z ̃ 4.3 and 4.8) suggest that these sources have redshifts z > 4. At least 40% of the ALMA sources host an X-ray AGN, compared to ̃14% for other galaxies of similar mass and redshift. The wide area of our ALMA survey provides lower values at the bright end of number counts than single-dish telescopes affected by confusion. -
A unique distant submillimeter galaxy with an X-ray-obscured radio-luminous active galactic nucleus Shu, X. W., Xue, Y. Q., Liu, D. Z., Wang, T., Han, Y. K., Chang, Y. Y., Liu, T., Huang, X. X., Wang, J. X., Zheng, X. Z., da Cunha, E., Daddi, E., and Elbaz, D. \aap 2018 [Abs] [ads] [arXiv]
Aims: We present a multiwavelength study of an atypical submillimeter galaxy, GH500.30, in the GOODS-North field, with the aim to understand its physical properties of stellar and dust emission, as well as the central active galactic nucleus (AGN) activity. Although it is shown that the source is likely an extremely dusty galaxy at high redshift, its exact position of submillimeter emission is unknown.
Methods: We use NOEMA observation at 1.2 mm with subarcsecond resolution to resolve the dust emission, and precisely localize the counterparts at other wavelengths, which allows us to better constrain its stellar and dust spectral energy distribution (SED) as well as redshift. We carry out the new near-infrared (NIR) photometry of GH500.30 observed with HST, and perform panchromatic SED modelling from ultraviolet (UV)/optical to submillimeter. We derive the photometric redshift using both NIR and far-infrared (FIR) SED modeling, and place constraints on the stellar and dust properties such as stellar mass, age, dust attenuation, IR luminosity, and star-formation rate (SFR). The AGN properties are inferred from the X-ray spectral analysis and radio observations, and its contribution to the total IR luminosity is estimated from the broadband SED fittings using MAGPHYS.
Results: With the new NOEMA interferometric imaging, we confirm that the source is a unique dusty galaxy. It has no obvious counterpart in the optical and even NIR images observed with HST at \ensuremathλ \ensuremath≲ 1.4 \ensuremathμm. Photometric- redshift analyses from both stellar and dust SED suggest it to likely be at z \ensuremath≳ 4, though a lower redshift at z \ensuremath≳ 3.1 cannot be fully ruled out (at 90% confidence interval). Explaining its unusual optical-to-NIR properties requires an old stellar population (̃0.67 Gyr), coexisting with a very dusty ongoing starburst component. The latter is contributing to the FIR emission, with its rest-frame UV and optical light being largely obscured along our line of sight. If the observed fluxes at the rest-frame optical/NIR wavelengths were mainly contributed by old stars, a total stellar mass of ̃3.5 \texttimes 10^11 M_☉ would be obtained. An X-ray spectral analysis suggests that this galaxy harbors a heavily obscured AGN with N_H = 3.3^+2.0_-1.7 \texttimes 10^23 cm^-2 and an intrinsic 2-10 keV luminosity of L_x ̃ 2.6 \texttimes 10^44 erg s^-1, which places this object among distant type 2 quasars. The radio emission of the source is extremely bright, which is an order of magnitude higher than the star- formation-powered emission, making it one of the most distant radio-luminous dusty galaxies.
Conclusions: The combined characteristics of the galaxy suggest that the source appears to have been caught in a rare but critical transition stage in the evolution of submillimeter galaxies, where we are witnessing the birth of a young AGN and possibly the earliest stage of its jet formation and feedback. -
Revealing the Environmental Dependence of Molecular Gas Content in a Distant X-Ray Cluster at z = 2.51 Wang, Tao, Elbaz, David, Daddi, Emanuele, Liu, Daizhong, Kodama, Tadayuki, Tanaka, Ichi, Schreiber, Corentin, Zanella, Anita, Valentino, Francesco, Sargent, Mark, Kohno, Kotaro, Xiao, Mengyuan, Pannella, Maurilio, Ciesla, Laure, Gobat, Raphael, and Koyama, Yusei \apjl 2018 [Abs] [ads] [arXiv]
We present a census of the molecular gas properties of galaxies in the most distant known X-ray cluster, CLJ1001, at z = 2.51, using deep observations of CO(1-0) with the Karl G. Jansky Very Large Array. In total, 14 cluster members with M _* > 10^10.5 M _☉ are detected, including all of the massive star-forming members within the virial radius, providing the largest galaxy sample in a single cluster at z > 2 with CO(1-0) measurements. We find a large variety in the gas content of these cluster galaxies, which is correlated with their relative positions (or accretion states), with those closer to the cluster core being increasingly gas-poor. Moreover, despite their low gas content, the galaxies in the cluster center exhibit an elevated star formation efficiency (SFE; SFE = SFR/M _gas) compared to field galaxies, suggesting that the suppression on the SFR is likely delayed compared to that on the gas content. Their gas depletion time is around t _dep ̃ 400 Myr, which is comparable to the cluster dynamical time. This implies that they will consume all of their gas within a single orbit around the cluster center, and form a passive cluster core by z ̃ 2. This result is one of the first direct pieces of evidence for the influence of environment on the gas reservoirs and SFE of z > 2 cluster galaxies, thereby providing new insights into the rapid formation and quenching of the most massive galaxies in the early universe.
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Starbursts in and out of the star-formation main sequence Elbaz, D., Leiton, R., Nagar, N., Okumura, K., Franco, M., Schreiber, C., Pannella, M., Wang, T., Dickinson, M., Dı́az-Santos, T., Ciesla, L., Daddi, E., Bournaud, F., Magdis, G., Zhou, L., and Rujopakarn, W. \aap 2018 [Abs] [ads] [arXiv]
Aims: We use high-resolution continuum images obtained with the Atacama Large Millimeter Array (ALMA) to probe the surface density of star formation in z 2 galaxies and study the different physical properties between galaxies within and above the star-formation main sequence of galaxies.
Methods: We use ALMA images at 870 \ensuremathμm with 0.2 arcsec resolution in order to resolve star formation in a sample of eight star-forming galaxies at z 2 selected among the most massive Herschel galaxies in the GOODS-South field. This sample is supplemented with eleven galaxies from the public data of the 1.3 mm survey of the Hubble Ultra-Deep Field, HUDF. We derive dust and gas masses for the galaxies, compute their depletion times and gas fractions, and study the relative distributions of rest-frame ultraviolet (UV) and far-infrared (FIR) light.
Results: ALMA reveals systematically dense concentrations of dusty star formation close to the center of the stellar component of the galaxies. We identify two different starburst regimes: (i) the classical population of starbursts located above the SFR-M_\ensuremath⋆ main sequence, with enhanced gas fractions and short depletion times and (ii) a sub- population of galaxies located within the scatter of the main sequence that experience compact star formation with depletion timescales typical of starbursts of 150 Myr. In both starburst populations, the FIR and UV are distributed in distinct regions and dust-corrected star formation rates (SFRs) estimated using UV-optical-near-infrared data alone underestimate the total SFR. Starbursts hidden in the main sequence show instead the lowest gas fractions of our sample and could represent the last stage of star formation prior to passivization. Being Herschel- selected, these main sequence galaxies are located in the high- mass end of the main sequence, hence we do not know whether these “starbursts hidden in the main sequence” also exist below 10^11 M_☉. Active galactic nuclei (AGNs) are found to be ubiquitous in these compact starbursts, suggesting that the triggering mechanism also feeds the central black hole or that the active nucleus triggers star formation. -
ALMA 26 Arcmin^2 Survey of GOODS-S at One Millimeter (ASAGAO): Average Morphology of High-z Dusty Star-forming Galaxies in an Exponential Disk (n ≃ 1) Fujimoto, Seiji, Ouchi, Masami, Kohno, Kotaro, Yamaguchi, Yuki, Hatsukade, Bunyo, Ueda, Yoshihiro, Shibuya, Takatoshi, Inoue, Shigeki, Oogi, Taira, Toft, Sune, Gómez-Guijarro, Carlos, Wang, Tao, Espada, Daniel, Nagao, Tohru, Tanaka, Ichi, Ao, Yiping, Umehata, Hideki, Taniguchi, Yoshiaki, Nakanishi, Kouichiro, Rujopakarn, Wiphu, Ivison, R. J., Wang, Wei-hao, Lee, Minju M., Tadaki, Ken-ichi, Tamura, Yoichi, and Dunlop, J. S. \apj 2018 [Abs] [ads] [arXiv]
We present morphological properties of dusty star-forming galaxies at z = 1-3 determined with the high-resolution (FWHM ̃ 0.″19) Atacama Large Milllimeter/submillimeter Array (ALMA) 1 mm map of our ASAGAO survey covering a 26 arcmin^2 area in GOODS-S. In conjunction with the ALMA archival data, our sample consists of 45 ALMA sources with infrared luminosity (L _IR) range of ̃10^11-10^13 L _☉. To obtain an average rest- frame far-infrared (FIR) profile, we perform individual measurements and careful stacking of the ALMA sources using the uv-visibility method that includes positional-uncertainty and smoothing-effect evaluations through Monte Carlo simulations. We find that our sample has an average FIR-wavelength Sérsic index and effective radius of n _FIR = 1.2 \ensuremath\pm 0.2 and R _e,FIR = 1.0-1.3 kpc, respectively, additionally with a point-source component at the center, indicative of the existence of active galactic nuclei. The average FIR profile agrees with a morphology of an exponential disk clearly distinguished from a de Vaucouleurs spheroidal profile (Sérsic index of 4). We also examine the rest-frame optical Sérsic index n _opt and effective radius R _e,opt with deep Hubble Space Telescope (HST) images. Interestingly, we obtain n _opt = 0.9 \ensuremath\pm 0.3 (≃n _FIR) and R _e,opt = 3.2 \ensuremath\pm 0.6 kpc (>R _e,FIR), suggesting that the dusty disk-like structure is embedded within a larger stellar disk. The rest-frame UV and FIR data of HST and ALMA provide us with a radial profile of the total star formation rate (SFR), where the infrared SFR dominates over the UV SFR at the center. Under the assumption of a constant SFR, a compact stellar distribution in z ̃ 1-2 compact quiescent galaxies (cQGs) is well reproduced, while a spheroidal stellar morphology of cQGs (n _opt = 4) is not, suggestive of other important mechanism(s) such as dynamical dissipation.
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Identification of galaxies that experienced a recent major drop of star formation Ciesla, L., Elbaz, D., Schreiber, C., Daddi, E., and Wang, T. \aap 2018 [Abs] [ads] [arXiv]
Variations of star formation activity may happen on a large range of timescales and some of them are expected to be short, that is, a few hundred million years. The study of the physical processes linked to these rapid variations requires large statistical samples to pinpoint galaxies undergoing such transformations. Building upon a previous study, we define a method to blindly identify galaxies that have undergone, and may still be undergoing, a fast downfall of their star formation activity, that is, a more than 80% drop in star formation rate (SFR) occurring in less than 500 Myr. Modeling galaxies’ spectral energy distribution (SED) with a delayed-\ensuremathτ star formation history, with and without allowing an instantaneous SFR drop within the last hundred million years, we isolate 102 candidates out of a subsample of 6680 galaxies classified as “star forming” from the UVJ criterion in the ZFOURGE catalogs. These galaxies are mostly located in the lower part of the SFR-M_* main sequence (MS) and extend up to a factor 100 below it. They also lie close to the limit between the passive and active regions on the UVJ diagram, indicating that they are in a transition phase. We show that the selected candidates have different physical properties compared to galaxies with similar UVJ colors, namely, lower SFRs and different stellar masses. The morphology of the candidates shows no preference for a particular type. Among the 102 candidates, only 4 show signs of a active galactic nucleus (AGN) activity (from X-ray luminosity or ultraviolet-infrared (UV-IR) SED fitting decomposition). This low fraction of AGNs among the candidates implies that AGN activity may not be the main driver of the recent downfall, although timescale differences and duty cycle must be taken into account. We finally attempt to recover the past position of these galaxies on the SFR-M_* plane, before the downfall of their star formation and show that some of them were in the starburst region before, and are now back on the MS. These candidates constitute a promising sample that needs more investigation in order to understand the different mechanisms at the origin of the star formation decrease of the Universe since z 2.
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The Morphological Evolution, AGN Fractions, Dust Content, Environments, and Downsizing of Massive Green Valley Galaxies at 0.5 < z < 2.5 in 3D-HST/CANDELS Gu, Yizhou, Fang, Guanwen, Yuan, Qirong, Cai, Zhenyi, and Wang, Tao \apj 2018 [Abs] [ads] [arXiv]
To explore the evolutionary connection among red, green, and blue galaxy populations, based on a sample of massive ({M}_* > {10}^10 {M}_☉ ) galaxies at 0.5 < z < 2.5 in five 3D-HST/CANDELS fields, we investigate the dust content, morphologies, structures, active galactic nucleus (AGN) fractions, and environments of these three populations. Green valley galaxies are found to have intermediate dust attenuation and reside in the middle of the regions occupied by quiescent and star-forming galaxies in the UVJ diagram. Compared with blue and red galaxy populations at z < 2, green galaxies have intermediate compactness and morphological parameters. The above findings seem to favor the scenario that green galaxies are at a transitional phase when star-forming galaxies are being quenched into quiescent status. The green galaxies at z < 2 show the highest AGN fraction, suggesting that AGN feedback may have played an important role in star formation quenching. For the massive galaxies at 2 < z < 2.5, both red and green galaxies are found to have a similarly higher AGN fraction than the blue ones, which implies that AGN feedback may help to keep quiescence of red galaxies at z > 2. A significant environmental difference is found between green and red galaxies at z < 1.5. Green and blue galaxies at z > 0.5 seem to have similar local density distributions, suggesting that environment quenching is not the major mechanism to cease star formation at z > 0.5. The fractions of three populations as functions of mass support a “downsizing” quenching picture that the bulk of star formation in more massive galaxies is completed earlier than that of lower-mass galaxies.
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Jekyll & Hyde: quiescence and extreme obscuration in a pair of massive galaxies 1.5 Gyr after the Big Bang Schreiber, C., Labbé, I., Glazebrook, K., Bekiaris, G., Papovich, C., Costa, T., Elbaz, D., Kacprzak, G. G., Nanayakkara, T., Oesch, P., Pannella, M., Spitler, L., Straatman, C., Tran, K. -V., and Wang, T. \aap 2018 [Abs] [ads] [arXiv]
We obtained ALMA spectroscopy and deep imaging to investigate the origin of the unexpected sub-millimeter emission toward the most distant quiescent galaxy known to date, ZF-COSMOS-20115 at z = 3.717. We show here that this sub-millimeter emission is produced by another massive (M_* 10^11 M_☉), compact (r_1/2 = 0.67 \ensuremath\pm 0.14 kpc) and extremely obscured galaxy (A_V 3.5), located only 0.43“ (3.1 kpc) away from the quiescent galaxy. We dub the quiescent and dusty galaxies Jekyll and Hyde, respectively. No dust emission is detected at the location of the quiescent galaxy, implying SFR < 13 M_☉ yr^-1 which is the most stringent upper limit ever obtained for a quiescent galaxy at these redshifts. The two sources are spectroscopically confirmed to lie at the same redshift thanks to the detection of [C II]_158 in Hyde (z = 3.709), which provides one the few robust redshifts for a highly-obscured ”H-dropout“ galaxy (H - [4.5] = 5.1 \ensuremath\pm 0.8). The [C II] line shows a clear rotating-disk velocity profile which is blueshifted compared to the Balmer lines of Jekyll by 549 \ensuremath\pm 60 km s^-1, demonstrating that it is produced by another galaxy. Careful de-blending of the Spitzer imaging confirms the existence of this new massive galaxy, and its non-detection in the Hubble images requires extremely red colors and strong attenuation by dust. Full modeling of the UV-to-far-IR emission of both galaxies shows that Jekyll has fully quenched at least 200Myr prior to observation and still presents a challenge for models, while Hyde only harbors moderate star-formation with SFR \ensuremath≲ 120 M_☉ yr^-1, and is located at least a factor 1.4 below the z 4 main sequence. Hyde could also have stopped forming stars less than 200 Myr before being observed; this interpretation is also suggested by its compactness comparable to that of z 4 quiescent galaxies and its low [C II]/FIR ratio, but significant on-going star-formation cannot be ruled out. Lastly, we find that despite its moderate SFR, Hyde hosts a dense reservoir of gas comparable to that of the most extreme starbursts. This suggests that whatever mechanism has stopped or reduced its star-formation must have done so without expelling the gas outside of the galaxy. Because of their surprisingly similar mass, compactness, environment and star-formation history, we argue that Jekyll and Hyde can be seen as two stages of the same quenching process, and provide a unique laboratory to study this poorly understood phenomenon. The reduced ALMA image, spectrum, and data cube are available in electronic form at the CDS via anonymous ftp to <A href=”http:/ /cdsarc.u-strasbg.fr“>http://cdsarc.u-strasbg.fr</A> (<A href=”http://cdsarc.u-strasbg.fr“>http://<IP_ADDRESS></A>) or via <A href=”http://cdsarc.u-strasbg.fr/viz- bin/qcat?J/A+A/611/A22”>http://cdsarc.u-strasbg.fr/viz- bin/qcat?J/A+A/611/A22</A>
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Cospatial Star Formation and Supermassive Black Hole Growth in z ̃ 3 Galaxies: Evidence for In Situ Co-evolution Rujopakarn, W., Nyland, K., Rieke, G. H., Barro, G., Elbaz, D., Ivison, R. J., Jagannathan, P., Silverman, J. D., Smolčić, V., and Wang, T. \apjl 2018 [Abs] [ads] [arXiv]
We present a sub-kiloparsec localization of the sites of supermassive black hole (SMBH) growth in three active galactic nuclei (AGNs) at z ̃ 3 in relation to the regions of intense star formation in their hosts. These AGNs are selected from Karl G. Jansky Very Large Array (VLA) and Atacama Large Millimeter/submillimeter Array (ALMA) observations in the Hubble Ultra-Deep Field and COSMOS, with the centimetric radio emission tracing both star formation and AGN, and the sub/millimeter emission by dust tracing nearly pure star formation. We require radio emission to be \ensuremath≥slant 5\texttimes more luminous than the level associated with the sub/millimeter star formation to ensure that the radio emission is AGN-dominated, thereby allowing localization of the AGN and star formation independently. In all three galaxies, the AGNs are located within the compact regions of gas-rich, heavily obscured, intense nuclear star formation, with R _ e = 0.4-1.1 kpc and average star formation rates of ≃100-1200 M _☉ yr^-1. If the current episode of star formation continues at such a rate over the stellar mass doubling time of their hosts, ≃0.2 Gyr, the newly formed stellar mass will be of the order of 10^11 M _☉ within the central kiloparsec region, concurrently and cospatially with significant growth of the SMBH. This is consistent with a picture of in situ galactic bulge and SMBH formation. This work demonstrates the unique complementarity of VLA and ALMA observations to unambiguously pinpoint the locations of AGNs and star formation down to ≃30 mas, corresponding to ≃230 pc at z = 3.
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“Super-deblended” Dust Emission in Galaxies. I. The GOODS-North Catalog and the Cosmic Star Formation Rate Density out to Redshift 6 Liu, Daizhong, Daddi, Emanuele, Dickinson, Mark, Owen, Frazer, Pannella, Maurilio, Sargent, Mark, Béthermin, Matthieu, Magdis, Georgios, Gao, Yu, Shu, Xinwen, Wang, Tao, Jin, Shuowen, and Inami, Hanae \apj 2018 [Abs] [ads] [arXiv]
We present a new technique to measure multi-wavelength “super-deblended” photometry from highly confused images, which we apply to Herschel and ground-based far-infrared (FIR) and (sub-)millimeter (mm) data in the northern field of the Great Observatories Origins Deep Survey. There are two key novelties. First, starting with a large database of deep Spitzer 24 \ensuremathμm and VLA 20 cm detections that are used to define prior positions for fitting the FIR/submm data, we perform an active selection of useful priors independently at each frequency band, moving from less to more confused bands. Exploiting knowledge of redshift and all available photometry, we identify hopelessly faint priors that we remove from the fitting pool. This approach significantly reduces blending degeneracies and allows reliable photometry to be obtained for galaxies in FIR+mm bands. Second, we obtain well-behaved, nearly Gaussian flux density uncertainties, individually tailored to all fitted priors for each band. This is done by exploiting extensive simulations that allow us to calibrate the conversion of formal fitting uncertainties to realistic uncertainties, depending on directly measurable quantities. We achieve deeper detection limits with high fidelity measurements and uncertainties at FIR+mm bands. As an illustration of the utility of these measurements, we identify 70 galaxies with z\ensuremath≥slant 3 and reliable FIR+mm detections. We present new constraints on the cosmic star formation rate density at 3< z< 6, finding a significant contribution from z\ensuremath≥slant 3 dusty galaxies that are missed by optical-to-near-infrared color selection. Photometric measurements for 3306 priors, including more than 1000 FIR+mm detections, are released publicly with our catalog.
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Dust temperature and mid-to-total infrared color distributions for star-forming galaxies at 0 < z < 4 Schreiber, C., Elbaz, D., Pannella, M., Ciesla, L., Wang, T., and Franco, M. \aap 2018 [Abs] [ads] [arXiv]
We present a new, publicly available library of dust spectral energy distributions (SEDs). These SEDs are characterized by only three parameters: the dust mass (M_dust), the dust temperature (T_dust), and the mid-to-total infrared color (IR8 \ensuremath≡ L_IR/L_8). The latter measures the relative contribution of polycyclic aromatic hydrocarbon (PAH) molecules to the total infrared luminosity. We used this library to model star-forming galaxies at 0.5 < z < 4 in the deep CANDELS fields, using both individual detections and stacks of Herschel and ALMA imaging, and extending this sample to z = 0 using the Herschel Reference Survey. At first order, the dust SED of a galaxy was observed to be independent of stellar mass, but evolving with redshift. We found trends of increasing T_dust and IR8 with redshift and distance from the SFR-M_\ensuremath* main sequence, and quantified for the first time their intrinsic scatter. Half of the observed variations of these parameters was captured by the above empirical relations, and after subtracting the measurement errors we found residual scatters of \ensuremath∆T_dust/T_dust = 12% and \ensuremath∆log IR8 = 0.18 dex. We observed second order variations with stellar mass: massive galaxies (M_\ensuremath* > 10^11M_☉) at z \ensuremath≤ 1 have slightly lower temperatures indicative of a reduced star formation efficiency, while low mass galaxies (M_\ensuremath* < 10^10M_☉) at z \ensuremath≥ 1 showed reduced PAH emission, possibly linked to their lower metallicities. Building on these results, we constructed high-fidelity mock galaxy catalogs to predict the accuracy of infrared luminosities and dust masses determined using a single broadband measurement. Using a single James Webb Space Telescope (JWST) MIRI band, we found that L_IR is typically uncertain by 0.15 dex, with a maximum of 0.25 dex when probing the rest-frame 8 \ensuremathμm, and this is not significantly impacted by typical redshift uncertainties. On the other hand, we found that ALMA bands 8 to 7 and 6 to 3 measured the dust mass at better than 0.2 and 0.15 dex, respectively, and independently of redshift, while bands 9 to 6 only measured L_IR at better than 0.2 dex at z > 1, 3.2, 3.8, and 5.7, respectively. Starburst galaxies had their L_IR significantly underestimated when measured by a single JWST or ALMA band, while their dust mass from a single ALMA band were moderately overestimated. This dust library and the results of this paper can be used immediately to improve the design of observing proposals, and interpret more accurately the large amount of archival data from Spitzer, Herschel and ALMA. The dust library described in this paper is available publicly at <A href=“http://cschreib.github.io/s17-irlib/”>http://cschreib.gi thub.io/s17-irlib/</A>Tables A.1-A.3 are also available at the CDS via anonymous ftp to <A href=“http://cdsarc.u-strasbg.fr”> http://cdsarc.u-strasbg.fr</A> (<A href=“http://<IP_ADDRESS>”>http://<IP_ADDRESS></A>) or via <A href=“http://cdsarc.u-strasbg.fr/viz- bin/qcat?J/A+A/609/A30”>http://cdsarc.u-strasbg.fr/viz- bin/qcat?J/A+A/609/A30</A>
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Chasing passive galaxies in the early Universe: a critical analysis in CANDELS GOODS-South Merlin, E., Fontana, A., Castellano, M., Santini, P., Torelli, M., Boutsia, K., Wang, T., Grazian, A., Pentericci, L., Schreiber, C., Ciesla, L., McLure, R., Derriere, S., Dunlop, J. S., and Elbaz, D. \mnras 2018 [Abs] [ads] [arXiv]
We search for passive galaxies at z > 3 in the GOODS-South field, using different techniques based on photometric data, and paying attention to develop methods that are sensitive to objects that have become passive shortly before the epoch of observation. We use CANDELS HST catalogues, ultra-deep Ks data and new IRAC photometry, performing spectral energy distribution fitting using models with abruptly quenched star formation histories. We then single out galaxies which are best fitted by a passively evolving model, and having only low probability (<5 per cent) star-forming solutions. We verify the effects of including nebular lines emission, and we consider possible solutions at different redshifts. The number of selected sources dramatically depends on the models used in the spectral energy distribution (SED) fitting. Without including emission lines and with photometric redshifts fixed at the CANDELS estimate, we single out 30 candidates; the inclusion of nebular lines emission reduces the sample to 10 objects; allowing for solutions at different redshifts, only two galaxies survive as robust candidates. Most of the candidates are not far-infrared emitters, corroborating their association with passive galaxies. Our results translate into an upper limit in the number density of ̃0.173 arcmin^2 above the detection limit. However, we conclude that the selection of passive galaxies at z > 3 is still subject to significant uncertainties, being sensitive to assumptions in the SED modelling adopted and to the relatively low S/N of the objects. By means of dedicated simulations, we show that JWST will greatly enhance the accuracy, allowing for a much more robust classification.
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ALMA twenty-six arcmin^2 survey of GOODS-S at one millimeter (ASAGAO): Source catalog and number counts Hatsukade, Bunyo, Kohno, Kotaro, Yamaguchi, Yuki, Umehata, Hideki, Ao, Yiping, Aretxaga, Itziar, Caputi, Karina I., Dunlop, James S., Egami, Eiichi, Espada, Daniel, Fujimoto, Seiji, Hayatsu, Natsuki H., Hughes, David H., Ikarashi, Soh, Iono, Daisuke, Ivison, Rob J., Kawabe, Ryohei, Kodama, Tadayuki, Lee, Minju, Matsuda, Yuichi, Nakanishi, Kouichiro, Ohta, Kouji, Ouchi, Masami, Rujopakarn, Wiphu, Suzuki, Tomoko, Tamura, Yoichi, Ueda, Yoshihiro, Wang, Tao, Wang, Wei-Hao, Wilson, Grant W., Yoshimura, Yuki, and Yun, Min S. \pasj 2018 [Abs] [ads] [arXiv]
We present the survey design, data reduction, construction of images, and source catalog of the Atacama Large Millimeter/submillimeter Array (ALMA) twenty-six arcmin^2 survey of GOODS-S at one millimeter (ASAGAO). ASAGAO is a deep (1 \ensuremathσ depth ̃ 61 \ensuremathμJy beam^-1 for a 250 k\ensuremathλ-tapered map with a synthesized beam size of 0{\^“_.}51 \texttimes 0{\^”_.}45) and wide area (26 arcmin^2) survey on a contiguous field at 1.2 mm. By combining with ALMA archival data in the GOODS-South field, we obtained a deeper map in the same region (1 \ensuremathσ depth ̃ 30 \ensuremathμJy beam^-1 for a deep region with a 250 k\ensuremathλ-taper, and a synthesized beam size of 0{\^“_.}59 \texttimes 0{\^”_.}53), providing the largest sample of sources (25 sources at \ensuremath≥5.0 \ensuremathσ, 45 sources at \ensuremath≥4.5 \ensuremathσ) among ALMA blank-field surveys to date. The number counts show that 52\^{+11}_{-8}% of the extragalactic background light at 1.2 mm is resolved into discrete sources at S_1.2 mm > 135 \ensuremathμJy. We create infrared (IR) luminosity functions (LFs) in the redshift range of z = 1-3 from the ASAGAO sources with K_s-band counterparts, and constrain the faintest luminosity of the LF at 2.0 < z < 3.0. The LFs are consistent with previous results based on other ALMA and SCUBA-2 observations, which suggest a positive luminosity evolution and negative density evolution with increasing redshift. We find that obscured star-formation of sources with IR luminosities of log (L_IR/L_☉) \ensuremath≳ 11.8 account for \ensuremath≈60%-90% of the z ̃ 2 cosmic star- formation rate density.
2017
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Radio Selection of the Most Distant Galaxy Clusters Daddi, E., Jin, S., Strazzullo, V., Sargent, M. T., Wang, T., Ferrari, C., Schinnerer, E., Smolčić, V., Calabró, A., Coogan, R., Delhaize, J., Delvecchio, I., Elbaz, D., Gobat, R., Gu, Q., Liu, D., Novak, M., and Valentino, F. \apjl 2017 [Abs] [ads] [arXiv]
We show that the most distant X-ray-detected cluster known to date, Cl J1001 at {z}_{spec}=2.506, hosts a strong overdensity of radio sources. Six of them are individually detected (within 10^\textbackslashprime\textbackslashprime ) in deep 0\textba ckslashbuildrel{\textbackslashprime\textbackslashprime}\textba ckslashover{.} 75 resolution VLA 3 GHz imaging, with {S}_3{GHz}> 8 \ensuremathμ {Jy}. Of the six, an active galactic nucleus (AGN) likely affects the radio emission in two galaxies, while star formation is the dominant source powering the remaining four. We searched for cluster candidates over the full COSMOS 2 deg^2 field using radio- detected 3 GHz sources and looking for peaks in }_5 density maps. Cl J1001 is the strongest overdensity by far with > 10\ensuremathσ , with a simple {z}_{phot}> 1.5 preselection. A cruder photometric rejection of z< 1 radio foregrounds leaves Cl J1001 as the second strongest overdensity, while even using all radio sources Cl J1001 remains among the four strongest projected overdensities. We conclude that there are great prospects for future deep and wide-area radio surveys to discover large samples of the first generation of forming galaxy clusters. In these remarkable structures, widespread star formation and AGN activity of massive galaxy cluster members, residing within the inner cluster core, will ultimately lead to radio continuum as one of the most effective means for their identification, with detection rates expected in the ballpark of 0.1-1 per square degree at z\ensuremath≳ 2.5. Samples of hundreds such high- redshift clusters could potentially constrain cosmological parameters and test cluster and galaxy formation models.
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EGG: hatching a mock Universe from empirical prescriptions\ensuremath⋆ Schreiber, C., Elbaz, D., Pannella, M., Merlin, E., Castellano, M., Fontana, A., Bourne, N., Boutsia, K., Cullen, F., Dunlop, J., Ferguson, H. C., Michałowski, M. J., Okumura, K., Santini, P., Shu, X. W., Wang, T., and White, C. \aap 2017 [Abs] [ads] [arXiv]
This paper introduces EGG, the Empirical Galaxy Generator, a tool designed within the ASTRODEEP collaboration to generate mock galaxy catalogs for deep fields with realistic fluxes and simple morphologies. The simulation procedure is based exclusively on empirical prescriptions - rather than first principles - to provide the most accurate match with current observations at 0 <z< 7. We considered that galaxies can be either quiescent or star-forming, and used their stellar mass (M_\ensuremath*) and redshift (z) as the fundamental properties from which all the other observables can be statistically derived. Drawing z and M_\ensuremath* from the observed galaxy stellar mass functions, a star-formation rate (SFR) is attributed to each galaxy from the tight SFR-M_\ensuremath* main sequence, while dust attenuation, optical colors and simple disk plus bulge morphologies are obtained from empirical relations that we established from the high quality Hubble and Herschel observations from the CANDELS fields. Random scatter was introduced in each step to reproduce the observed distributions of each parameter. Based on these observables, an adequate panchromatic spectral energy distribution (SED) is selected for each galaxy and synthetic photometry is produced by integrating the redshifted SED in common broad-band filters. Finally, the mock galaxies are placed on the sky at random positions with a fixed angular two-point correlation function to implement basic clustering. The resulting flux catalogs reproduce accurately the observed number counts in all broad bands from the ultraviolet up to the sub-millimeter, and can be directly fed to image simulators such as SkyMaker. The images can then be used to test source extraction softwares and image-based techniques such as stacking. EGG is open-source, and is made available to the community on behalf of the ASTRODEEP collaboration, together with a set of pre-generated catalogs and images. <A href=“http: //cschreib.github.io/egg/”>http://cschreib.github.io/egg/</A> Full Table C.1 is only available at the CDS via anonymous ftp to <A href=“http://cdsarc.u-strasbg.fr”>http://cdsarc.u-strasbg.f r</A> (<A href=“http://<IP_ADDRESS>”>http://<IP_ADDRESS></A>) or via <A href=“http://cdsarc.u-strasbg.fr/viz- bin/qcat?J/A+A/602/A96”>http://cdsarc.u-strasbg.fr/viz- bin/qcat?J/A+A/602/A96</A>
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AGN-host connection at 0.5 < z < 2.5: A rapid evolution of AGN fraction in red galaxies during the last 10 Gyr Wang, Tao, Elbaz, D., Alexander, D. M., Xue, Y. Q., Gabor, J. M., Juneau, S., Schreiber, C., Zheng, X. -Z., Wuyts, S., Shi, Y., Daddi, E., Shu, X. -W., Fang, G. -W., Huang, J. -S., Luo, B., and Gu, Q. -S. \aap 2017 [Abs] [ads] [arXiv]
We explore the dependence of the incidence of moderate-luminosity (L_0.5-8 keV = 10^41.9-43.7 erg s^-1) active galactic nuclei (AGNs) and the distribution of their accretion rates on host color at 0.5 <z < 2.5. Based on the deepest X-ray and UV-to-far-infrared data in the two The Great Observatories Origins Deep Survey (GOODS) fields, we identify 221 AGNs within a mass-complete parent galaxy sample down to M_\ensuremath* > 10^10 M_☉. We use extinction-corrected rest-frame U-V colors to divide both AGN hosts and non-AGN galaxies into red sequence (red), green valley (green), and blue cloud (blue) populations. We find that the fraction of galaxies hosting an AGN at fixed X-ray luminosity increases with stellar mass and redshift for all the three galaxy populations, independent of their colors. However, both the AGN fraction at fixed stellar mass and its evolution with redshift are clearly dependent on host colors. Most notably, red galaxies have the lowest AGN fraction ( 5%) at z 1 yet with most rapid evolution with redshift, increasing by a factor of 5 (24%) at z 2. Green galaxies exhibit the highest AGN fraction across all redshifts, which is most pronounced at z 2 with more than half of them hosting an AGN at M_\ensuremath* > 10^10.6 M_☉. Together with the high AGN fraction in red galaxies at z 2, this indicates that (X-ray) AGNs could be important in both transforming (quenching) star-forming galaxies into quiescent ones and subsequently maintaining their quiescence at high redshift. Furthermore, consistent with previous studies at lower redshifts, we show that the probability of hosting an AGN for the total galaxy population can be characterized by a universal Eddington ratio (as approximated by L_X/M_\ensuremath*) distribution (p(\ensuremathλ_Edd) \ensuremathλ_Edd^-0.4), which is independent on host mass. Yet consistent with their different AGN fractions, galaxies with different colors appear to also have different p(\ensuremathλ_Edd) with red galaxies exhibiting more rapid redshift evolution compared with that for green and blue galaxies. Evidence for a steeper power-law distribution of p(\ensuremathλ_Edd) in red galaxies (p(\ensuremathλ_Edd) \ensuremathλ_Edd^-0.6) is also presented, though larger samples are needed to confirm. These results suggest that the AGN accretion or the growth of supermassive black holes is related to their host properties, and may also influence their hosts in a different mode dependent on the host color.
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The ALMA Redshift 4 Survey (AR4S). I. The massive end of the z = 4 main sequence of galaxies Schreiber, C., Pannella, M., Leiton, R., Elbaz, D., Wang, T., Okumura, K., and Labbé, I. \aap 2017 [Abs] [ads] [arXiv]
We introduce the ALMA Redshift 4 Survey (AR4S), a systematic ALMA survey of all the known galaxies with stellar mass (M_\ensuremath*) larger than 5 \texttimes 10^10M_☉ at 3.5 <z< 4.7 in the GOODS-south, UDS and COSMOS CANDELS fields. The sample we have analyzed in this paper is composed of 96 galaxies observed with ALMA at 890 \ensuremathμm (180 \ensuremathμm rest-frame) with an on-source integration time of 1.3 min per galaxy. We detected 32% of the sample at more than 3\ensuremathσ significance. Using the stacked ALMA and Herschel photometry, we derived an average dust temperature of 40 \ensuremath\pm 2 K for the whole sample, and extrapolate the L_IR and SFR for all our galaxies based on their ALMA flux. We then used a forward modeling approach to estimate their intrinsic sSFR distribution, deconvolved of measurement errors and selection effects: we find a linear relation between SFR and M_\ensuremath*, with a median sSFR = 2.8 \ensuremath\pm 0.8 Gyr and a dispersion around that relation of 0.28 \ensuremath\pm 0.13 dex. This latter value is consistent with that measured at lower redshifts, which is proof that the main sequence of star-forming galaxies was already in place at z = 4, at least among massive galaxies. These new constraints on the properties of the main sequence are in good agreement with the latest predictions from numerical simulations, and suggest that the bulk of star formation in galaxies is driven by the same mechanism from z = 4 to the present day, that is, over at least 90% of the cosmic history. We also discuss the consequences of our results on the population of early quiescent galaxies. This paper is part of a series that will employ these new ALMA observations to explore the star formation and dust properties of the massive end of the z = 4 galaxy population.
2016
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Identification of z \ensuremath≳ 2 Herschel 500 \ensuremathμM Sources Using Color Deconfusion Shu, X. W., Elbaz, D., Bourne, N., Schreiber, C., Wang, T., Dunlop, J. S., Fontana, A., Leiton, R., Pannella, M., Okumura, K., Michałowski, M. J., Santini, P., Merlin, E., Buitrago, F., Bruce, V. A., Amorin, R., Castellano, M., Derriere, S., Comastri, A., Cappelluti, N., Wang, J. X., and Ferguson, H. C. \apjs 2016 [Abs] [ads] [arXiv]
We present a new method to search for candidate z \ensuremath≳ 2 Herschel 500 \ensuremathμm sources in the Great Observatories Origins Deep Survey-North field using a S_500 \ensuremathμm/S_24 \ensuremathμm “color deconfusion” technique. Potential high-z sources are selected against low- redshift ones from their large 500 to 24 \ensuremathμm flux density ratios. By effectively reducing the contribution from low-redshift populations to the observed 500 \ensuremathμm emission, we are able to identify counterparts to high-z 500 \ensuremathμm sources whose 24 \ensuremathμm fluxes are relatively faint. The recovery of known z \ensuremath≳ 4 starbursts confirms the efficiency of this approach in selecting high-z Herschel sources. The resulting sample consists of 34 dusty star-forming galaxies at z \ensuremath≳ 2. The inferred infrared luminosities are in the range 1.5 \texttimes 10^12-1.8 \texttimes 10^13 L_☉, corresponding to dust-obscured star formation rates (SFRs) of ̃260-3100 M_☉ yr^-1 for a Salpeter initial mass function. Comparison with previous SCUBA 850 \ensuremathμ -selected galaxy samples shows that our method is more efficient at selecting high-z dusty galaxies, with a median redshift of z=3.07+/- 0.83 and with 10 of the sources at z \ensuremath≳ 4. We find that at a fixed luminosity, the dust temperature is ̃5 K cooler than that expected from the {T}_d-{L}_ relation at z\textbackslashquad \ensuremath≲ 1, though different temperature selection effects should be taken into account. The radio-detected subsample (excluding three strong active galactic nucleus) follows the far-infrared (far-IR)/radio correlation at lower redshifts, and no evolution with redshift is observed out to z̃ 5, suggesting that the far-IR emission is star formation dominated. The contribution of the high-z Herschel 500 \ensuremathμm sources to the cosmic SFR density is comparable to that of (sub)millimeter galaxy populations at z̃ 2.5 and at least 40% of the extinction-corrected UV samples at z̃ 4. Further investigation into the nature of these high-z dusty galaxies will be crucial for our understanding of the star formation histories and the buildup of stellar mass at the earliest cosmic epochs.
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Discovery of a Galaxy Cluster with a Violently Starbursting Core at z = 2.506 Wang, Tao, Elbaz, David, Daddi, Emanuele, Finoguenov, Alexis, Liu, Daizhong, Schreiber, Corentin, Martı́n, Sergio, Strazzullo, Veronica, Valentino, Francesco, van der Burg, Remco, Zanella, Anita, Ciesla, Laure, Gobat, Raphael, Le Brun, Amandine, Pannella, Maurilio, Sargent, Mark, Shu, Xinwen, Tan, Qinghua, Cappelluti, Nico, and Li, Yanxia \apj 2016 [Abs] [ads] [arXiv]
We report the discovery of a remarkable concentration of massive galaxies with extended X-ray emission at z _spec = 2.506, which contains 11 massive (M _* \ensuremath≳ 10^11 M _☉) galaxies in the central 80 kpc region (11.6\ensuremathσ overdensity). We have spectroscopically confirmed 17 member galaxies with 11 from CO and the remaining ones from H\ensuremathα. The X-ray luminosity, stellar mass content, and velocity dispersion all point to a collapsed, cluster-sized dark matter halo with mass M _200c = 10^13.9\ensuremath\pm0.2 M _☉, making it the most distant X-ray-detected cluster known to date. Unlike other clusters discovered so far, this structure is dominated by star-forming galaxies (SFGs) in the core with only 2 out of the 11 massive galaxies classified as quiescent. The star formation rate (SFR) in the 80 kpc core reaches ̃3400 M _☉ yr^-1 with a gas depletion time of ̃200 Myr, suggesting that we caught this cluster in rapid build-up of a dense core. The high SFR is driven by both a high abundance of SFGs and a higher starburst fraction (̃25%, compared to 3%-5% in the field). The presence of both a collapsed, cluster-sized halo and a predominant population of massive SFGs suggests that this structure could represent an important transition phase between protoclusters and mature clusters. It provides evidence that the main phase of massive galaxy passivization will take place after galaxies accrete onto the cluster, providing new insights into massive cluster formation at early epochs. The large integrated stellar mass at such high redshift challenges our understanding of massive cluster formation.
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Chandra Counterparts of CANDELS GOODS-S Sources Cappelluti, N., Comastri, A., Fontana, A., Zamorani, G., Amorin, R., Castellano, M., Merlin, E., Santini, P., Elbaz, D., Schreiber, C., Shu, X., Wang, T., Dunlop, J. S., Bourne, N., Bruce, V. A., Buitrago, F., Michałowski, Michał J., Derriere, S., Ferguson, H. C., Faber, S. M., and Vito, F. \apj 2016 [Abs] [ads] [arXiv]
Improving the capabilities of detecting faint X-ray sources is fundamental for increasing the statistics on faint high-z active galactic nuclei (AGNs) and star-forming galaxies (SFGs). We performed a simultaneous maximum likelihood point-spread function fit in the [0.5-2] keV and [2-7] keV energy bands of the 4 Ms Chandra Deep Field South (CDFS) data at the position of the 34,930 CANDELS H-band selected galaxies. For each detected source we provide X-ray photometry and optical counterpart validation. We validated this technique by means of a ray- tracing simulation. We detected a total of 698 X-ray point sources with a likelihood { L }\textbackslashgt 4.98 (I.e., >2.7\ensuremathσ). We show that prior knowledge of a deep sample of optical-NIR galaxies leads to a significant increase in the detection of faint (I.e., ̃10^-17 cgs in the [0.5-2] keV band) sources with respect to “blind” X-ray detections. By including previous X-ray catalogs, this work increases the total number of X-ray sources detected in the 4 Ms CDFS, CANDELS area to 793, which represents the largest sample of extremely faint X-ray sources assembled to date. Our results suggest that a large fraction of the optical counterparts of our X-ray sources determined by likelihood ratio actually coincides with the priors used for the source detection. Most of the new detected sources are likely SFGs or faint, absorbed AGNs. We identified a few sources with putative photometric redshift z > 4. Despite the low number statistics and the uncertainties on the photo z, this sample significantly increases the number of X-ray-selected candidate high-z AGNs.
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Observational evidence of a slow downfall of star formation efficiency in massive galaxies during the past 10 Gyr Schreiber, C., Elbaz, D., Pannella, M., Ciesla, L., Wang, T., Koekemoer, A., Rafelski, M., and Daddi, E. \aap 2016 [Abs] [ads] [arXiv]
We study the causes of the reported mass-dependence in the slope of the SFR-M_\ensuremath* relation, the so-called main sequence of star-forming galaxies, and discuss its implication on the physical processes that shaped the star formation history of massive galaxies over cosmic time. We made use of the near- infrared high-resolution imaging from the Hubble Space Telescope in the CANDELS fields to perform a careful bulge-to-disk decomposition of distant galaxies and measure for the first time the slope of the SFR-M_disk relation at z = 1. We find that this relation very closely follows the shape of the nominal SFR-M_\ensuremath* correlation, still with a pronounced flattening at the high-mass end. This clearly excludes, at least at z = 1, the progressive growth of quiescent stellar bulges in star-forming galaxies as the main driver for the change of slope of the main sequence. Then, by stacking the Herschel data available in the CANDELS field, we estimated the gas mass (M_gas = M_H I + M_H2) and the star formation efficiency (SFE \ensuremath≡ SFR/M_gas) at different positions on the SFR-M_\ensuremath* relation. We find that the relatively low SFRs observed in massive galaxies (M_\ensuremath*> 5 \texttimes 10^10 M_☉) are not caused by a reduced gas content, but by a star formation efficiency that is lower by up to a factor of 3 than in galaxies with lower stellar mass. The trend at the lowest masses is probably linked to the dominance of atomic over molecular gas. We argue that this stellar-mass- dependent SFE can explain the varying slope of the main sequence since z = 1.5, hence over 70% of the Hubble time. The drop in SFE occurs at lower masses in the local Universe (M_\ensuremath*> 2 \texttimes 10^10 M_☉) and is not present at z = 2. Altogether, this provides evidence for a slow decrease in star formation efficiency in massive main sequence galaxies. The resulting loss of star formation is found to be rising starting from z = 2 to reach a level similar to the mass growth of the quiescent population by z = 1. We finally discuss the possible physical origin of this phenomenon.
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The ASTRODEEP Frontier Fields catalogues. I. Multiwavelength photometry of Abell-2744 and MACS-J0416 Merlin, E., Amorı́n, R., Castellano, M., Fontana, A., Buitrago, F., Dunlop, J. S., Elbaz, D., Boucaud, A., Bourne, N., Boutsia, K., Brammer, G., Bruce, V. A., Capak, P., Cappelluti, N., Ciesla, L., Comastri, A., Cullen, F., Derriere, S., Faber, S. M., Ferguson, H. C., Giallongo, E., Grazian, A., Lotz, J., Michałowski, M. J., Paris, D., Pentericci, L., Pilo, S., Santini, P., Schreiber, C., Shu, X., and Wang, T. \aap 2016 [Abs] [ads] [arXiv]
Context. The Frontier Fields survey is a pioneering observational program aimed at collecting photometric data, both from space (Hubble Space Telescope and Spitzer Space Telescope) and from ground-based facilities (VLT Hawk-I), for six deep fields pointing at clusters of galaxies and six nearby deep parallel fields, in a wide range of passbands. The analysis of these data is a natural outcome of the Astrodeep project, an EU collaboration aimed at developing methods and tools for extragalactic photometry and creating valuable public photometric catalogues.
Aims: We produce multiwavelength photometric catalogues (from B to 4.5 \ensuremathμm) for the first two of the Frontier Fields, Abell-2744 and MACS-J0416 (plus their parallel fields).
Methods: To detect faint sources even in the central regions of the clusters, we develop a robust and repeatable procedure that uses the public codes Galapagos and Galfit to model and remove most of the light contribution from both the brightest cluster members, and the intra-cluster light. We perform the detection on the processed HST H160 image to obtain a pure H-selected sample, which is the primary catalogue that we publish. We also add a sample of sources which are undetected in the H160 image but appear on a stacked infrared image. Photometry on the other HST bands is obtained using SExtractor, again on processed images after the procedure for foreground light removal. Photometry on the Hawk-I and IRAC bands is obtained using our PSF-matching deconfusion code t-phot. A similar procedure, but without the need for the foreground light removal, is adopted for the Parallel fields.
Results: The procedure of foreground light subtraction allows for the detection and the photometric measurements of \raisebox-0.5ex\textasciitilde2500 sources per field. We deliver and release complete photometric H-detected catalogues, with the addition of the complementary sample of infrared- detected sources. All objects have multiwavelength coverage including B to H HST bands, plus K-band from Hawk-I, and 3.6-4.5 \ensuremathμm from Spitzer. full and detailed treatment of photometric errors is included. We perform basic sanity checks on the reliability of our results.
Conclusions: The multiwavelength photometric catalogues are available publicly and are ready to be used for scientific purposes. Our procedures allows for the detection of outshone objects near the bright galaxies, which, coupled with the magnification effect of the clusters, can reveal extremely faint high redshift sources. Full analysis on photometric redshifts is presented in Paper II. The catalogues, together with the final processed images for all HST bands (as well as some diagnostic data and images), are publicly available and can be downloaded from the Astrodeep website at <A href=“http://www.astrodeep.eu/frontier- fields/”>http://www.astrodeep.eu/frontier-fields/</A> and from a dedicated CDS webpage (<A href=“http://astrodeep.u-strasbg.fr /ff/index.html”>http://astrodeep.u-strasbg.fr/ff/index.html</A> ). The catalogues are also available at the CDS via anonymous ftp to <A href=“http://cdsarc.u-strasbg.fr”>http://cdsarc.u-st rasbg.fr</A> (<A href=“http://<IP_ADDRESS>”>http://<IP_ADDRESS></A>) or via <A href=“http://cdsarc.u-strasbg.fr/viz- bin/qcat?J/A+A/590/A31”>http://cdsarc.u-strasbg.fr/viz- bin/qcat?J/A+A/590/A31</A> -
The ASTRODEEP Frontier Fields catalogues. II. Photometric redshifts and rest frame properties in Abell-2744 and MACS-J0416 Castellano, M., Amorı́n, R., Merlin, E., Fontana, A., McLure, R. J., Mármol-Queraltó, E., Mortlock, A., Parsa, S., Dunlop, J. S., Elbaz, D., Balestra, I., Boucaud, A., Bourne, N., Boutsia, K., Brammer, G., Bruce, V. A., Buitrago, F., Capak, P., Cappelluti, N., Ciesla, L., Comastri, A., Cullen, F., Derriere, S., Faber, S. M., Giallongo, E., Grazian, A., Grillo, C., Mercurio, A., Michałowski, M. J., Nonino, M., Paris, D., Pentericci, L., Pilo, S., Rosati, P., Santini, P., Schreiber, C., Shu, X., and Wang, T. \aap 2016 [Abs] [ads] [arXiv]
Aims: We present the first public release of photometric redshifts, galaxy rest frame properties and associated magnification values in the cluster and parallel pointings of the first two Frontier Fields, Abell-2744 and MACS-J0416. The released catalogues aim to provide a reference for future investigations of extragalactic populations in these legacy fields: from lensed high-redshift galaxies to cluster members themselves.
Methods: We exploit a multiwavelength catalogue, ranging from Hubble Space Telescope (HST) to ground- based K and Spitzer IRAC, which is specifically designed to enable detection and measurement of accurate fluxes in crowded cluster regions. The multiband information is used to derive photometric redshifts and physical properties of sources detected either in the H-band image alone, or from a stack of four WFC3 bands. To minimize systematics, median photometric redshifts are assembled from six different approaches to photo-z estimates. Their reliability is assessed through a comparison with available spectroscopic samples. State-of-the-art lensing models are used to derive magnification values on an object-by- object basis by taking into account sources positions and redshifts.
Results: We show that photometric redshifts reach a remarkable \raisebox-0.5ex\textasciitilde3-5% accuracy. After accounting for magnification, the H-band number counts are found to be in agreement at bright magnitudes with number counts from the CANDELS fields, while extending the presently available samples to galaxies that, intrinsically, are as faint as H \raisebox-0.5ex~32-33, thanks to strong gravitational lensing. The Frontier Fields allow the galaxy stellar mass distribution to be probed, depending on magnification, at 0.5-1.5 dex lower masses with respect to extragalactic wide fields, including sources at M_star \raisebox-0.5ex~10^7-10^8 M_☉ at z > 5. Similarly, they allow the detection of objects with intrinsic star formation rates (SFRs) >1 dex lower than in the CANDELS fields reaching 0.1-1 M_☉/yr at z \raisebox-0.5ex~6-10. The catalogues, together with the final processed images for all HST bands (as well as some diagnostic data and images), are publicly available and can be downloaded from the Astrodeep website at <A href=“http://www.astrodeep.eu/frontier- fields/”>http://www.astrodeep.eu/frontier-fields/</A> and from a dedicated CDS webpage (<A href=“http://astrodeep.u-strasbg.fr /ff/index.html”>http://astrodeep.u-strasbg.fr/ff/index.html</A> ). The catalogues are also available at the CDS via anonymous ftp to <A href=“http://cdsarc.u-strasbg.fr”>http://cdsarc.u-st rasbg.fr</A> (<A href=“http://<IP_ADDRESS>”>http://<IP_ADDRESS></A>) or via <A href=“http://cdsarc.u-strasbg.fr/viz- bin/qcat?J/A+A/590/A31”>http://cdsarc.u-strasbg.fr/viz- bin/qcat?J/A+A/590/A31</A> -
Infrared Color Selection of Massive Galaxies at z > 3 Wang, T., Elbaz, D., Schreiber, C., Pannella, M., Shu, X., Willner, S. P., Ashby, M. L. N., Huang, J. -S., Fontana, A., Dekel, A., Daddi, E., Ferguson, H. C., Dunlop, J., Ciesla, L., Koekemoer, A. M., Giavalisco, M., Boutsia, K., Finkelstein, S., Juneau, S., Barro, G., Koo, D. C., Michałowski, M. J., Orellana, G., Lu, Y., Castellano, M., Bourne, N., Buitrago, F., Santini, P., Faber, S. M., Hathi, N., Lucas, R. A., and Pérez-González, P. G. \apj 2016 [Abs] [ads] [arXiv]
We introduce a new color selection technique to identify high-redshift, massive galaxies that are systematically missed by Lyman-break selection. The new selection is based on the H_160 (H) and Infrared Array Camera (IRAC) 4.5 \ensuremathμm bands, specifically H-[4.5]\textbackslashgt 2.25 mag. These galaxies, called “HIEROs,” include two major populations that can be separated with an additional J - H color. The populations are massive and dusty star-forming galaxies at z\textbackslashgt 3 ({JH}-{blue}) and extremely dusty galaxies at z\ensuremath≲ 3 ({JH}-{red}). The 350 arcmin^2 of the GOODS-North and GOODS-South fields with the deepest Hubble Space Telescope (HST)/Wide Field Camera 3 (WFC3) near-infrared and IRAC data contain as many as 285 HIEROs down to [4.5]\textbackslashlt 24 mag. Inclusion of the most extreme HIEROs, not even detected in the H band, makes this selection particularly complete for the identification of massive high-redshift galaxies. We focus here primarily on {JH}-{blue} (z\textbackslashgt 3) HIEROs, which have a median photometric redshift < z> ̃ 4.4 and stellar mass {M}_*̃ {10}^10.6 {M}_☉ and are much fainter in the rest-frame UV than similarly massive Lyman-break galaxies (LBGs). Their star formation rates (SFRs), derived from their stacked infrared spectral energy distributions (SEDs), reach ̃240 {M}_☉ yr^-1, leading to a specific SFR, \textbackslashequiv /{M}_*̃ 4.2 Gyr^-1, suggesting that the sSFRs for massive galaxies continue to grow at z\textbackslashgt 2 but at a lower growth rate than from z = 0 to z = 2. With a median half-light radius of 2 kpc, including ̃ 20% as compact as quiescent (QS) galaxies at similar redshifts, {JH}-{blue} HIEROs represent perfect star-forming progenitors of the most massive ({M}_*\ensuremath≳ {10}^11.2 {M}_☉ ) compact QS galaxies at z̃ 3 and have the right number density. HIEROs make up ̃ 60% of all galaxies with {M}_*\textbackslashgt {10}^10.5 {M}_☉ identified at z\textbackslashgt 3 from their photometric redshifts. This is five times more than LBGs with nearly no overlap between the two populations. While HIEROs make up 15%-25% of the total SFR density at z̃ 4-5, they completely dominate the SFR density taking place in {M}_*\textbackslashgt {10}^10.5 {M}_☉ galaxies, and HIEROs are therefore crucial to understanding the very early phase of massive galaxy formation.
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T-PHOT version 2.0: Improved algorithms for background subtraction, local convolution, kernel registration, and new options Merlin, E., Bourne, N., Castellano, M., Ferguson, H. C., Wang, T., Derriere, S., Dunlop, J. S., Elbaz, D., and Fontana, A. \aap 2016 [Abs] [ads] [arXiv]
Aims: We present the new release - version 2.0 - of t-phot, a publicly available software package developed to perform PSF- matched, prior-based, multiwavelength deconfusion photometry of extragalactic fields.
Methods: New features included in the code are presented and discussed: background estimation, fitting using position dependent kernels, flux prioring, diagnostical statistics on the residual image, exclusion of selected sources from the model and residual images, and individual registration of fitted objects.
Results: The new options improve on the performance of the code, allowing for more accurate results and providing useful aids for diagnostics.
2015
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T-PHOT: A new code for PSF-matched, prior-based, multiwavelength extragalactic deconfusion photometry Merlin, E., Fontana, A., Ferguson, H. C., Dunlop, J. S., Elbaz, D., Bourne, N., Bruce, V. A., Buitrago, F., Castellano, M., Schreiber, C., Grazian, A., McLure, R. J., Okumura, K., Shu, X., Wang, T., Amorı́n, R., Boutsia, K., Cappelluti, N., Comastri, A., Derriere, S., Faber, S. M., and Santini, P. \aap 2015 [Abs] [ads] [arXiv]
Context. The advent of deep multiwavelength extragalactic surveys has led to the necessity for advanced and fast methods for photometric analysis. In fact, codes which allow analyses of the same regions of the sky observed at different wavelengths and resolutions are becoming essential to thoroughly exploit current and future data. In this context, a key issue is the confusion (i.e. blending) of sources in low-resolution images.
Aims: We present t-phot, a publicly available software package developed within the astrodeep project. t-phot is aimed at extracting accurate photometry from low-resolution images, where the blending of sources can be a serious problem for the accurate and unbiased measurement of fluxes and colours.
Methods: t-phot can be considered as the next generation to tfit, providing significant improvements over and above it and other similar codes (e.g. convphot). t-phot gathers data from a high-resolution image of a region of the sky, and uses this information (source positions and morphologies) to obtain priors for the photometric analysis of the lower resolution image of the same field. t-phot can handle different types of datasets as input priors, namely i) a list of objects that will be used to obtain cutouts from the real high-resolution image; ii) a set of analytical models (as .fits stamps); iii) a list of unresolved, point-like sources, useful for example for far-infrared (FIR) wavelength domains.
Results: By means of simulations and analysis of real datasets, we show that t-phot yields accurate estimations of fluxes within the intrinsic uncertainties of the method, when systematic errors are taken into account (which can be done thanks to a flagging code given in the output). t-phot is many times faster than similar codes like tfit and convphot (up to hundreds, depending on the problem and the method adopted), whilst at the same time being more robust and more versatile. This makes it an excellent choice for the analysis of large datasets. When used with the same parameter sets as for tfit it yields almost identical results (although in a much shorter time); in addition we show how the use of different settings and methods significantly enhances the performance.
Conclusions: t-phot proves to be a state-of-the-art tool for multiwavelength optical to far-infrared image photometry. Given its versatility and robustness, t-phot can be considered the preferred choice for combined photometric analysis of current and forthcoming extragalactic imaging surveys. t-phot is publicly available for downloading from <A href=“http://www.ast rodeep.eu/t-phot/”>http://www.astrodeep.eu/t-phot/</A> -
Satellite content and quenching of star formation in galaxy groups at z \raisebox-0.5ex~1.8 Gobat, R., Daddi, E., Béthermin, M., Pannella, M., Finoguenov, A., Gozaliasl, G., Le Floc’h, E., Schreiber, C., Strazzullo, V., Sargent, M., Wang, T., Hwang, H. S., Valentino, F., Cappelluti, N., Li, Y., and Hasinger, G. \aap 2015 [Abs] [ads] [arXiv]
We study the properties of satellites in the environment of massive star-forming galaxies at z \raisebox-0.5ex~1.8 in the COSMOS field, using a sample of 215 galaxies on the main sequence of star formation with an average mass of \raisebox-0.5ex~10^11M_☉. At z> 1.5, these galaxies typically trace halos of mass \ensuremath≳10^13M_☉. We use optical-near- infrared photometry to estimate stellar masses and star formation rates (SFR) of centrals and satellites down to \raisebox-0.5ex~6 \texttimes 10^9M_☉. We stack data around 215 central galaxies to statistically detect their satellite halos, finding an average of \raisebox-0.5ex\textasciitilde3 galaxies in excess of the background density. We fit the radial profiles of satellites with simple \ensuremathβ-models, and compare their integrated properties to model predictions. We find that the total stellar mass of satellites amounts to \raisebox-0.5ex\textasciitilde68% of the central galaxy, while spectral energy distribution modeling and far-infrared photometry consistently show their total SFR to be 25-35% of the central’s rate. We also see significant variation in the specific SFR of satellites within the halo with, in particular, a sharp decrease at <100 kpc. After considering different potential explanations, we conclude that this is likely an environmental signature of the hot inner halo. This effect can be explained in the first order by a simple free-fall scenario, suggesting that these low-mass environments can shut down star formation in satellites on relatively short timescales of \raisebox-0.5ex\textasciitilde0.3 Gyr.
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The Star Formation Main Sequence: The Dependence of Specific Star Formation Rate and Its Dispersion on Galaxy Stellar Mass Guo, Kexin, Zheng, Xian Zhong, Wang, Tao, and Fu, Hai \apjl 2015 [Abs] [ads] [arXiv]
The dispersion of the star formation main sequence (SFMS) reflects the diversity of star formation histories (SFHs) and variation in star formation rates (SFRs) in star-forming galaxies (SFGs) with similar stellar masses (M*). We examine the dispersion of the local SFMS using a complete sample of Sloan Digital Sky Survey galaxies at 0.01\textbackslashlt z\textbackslashlt 0.03 with {log}(M*/{M}_☉ ) \textbackslashgt 8.8. The SFRs are estimated from H\ensuremathα in combination with 22 \ensuremathμm observation from the Wide-field Infrared Survey Explorer. We measure the dispersion of specific SFRs (sSFRs) as a function of M*. We confirm that the dispersion increases with M* from 0.37 \ensuremath\pm 0.01 dex at {log}(M*/{M}_☉ )\textbackslashlt 9.6 to 0.51 \ensuremath\pm 0.02 dex at {log}(M*/{M}_☉ ) \textbackslashgt 10.2. Despite star formation being mostly associated with disks, the dispersion of disk sSFR still increases with M*. We conclude that the presence of bulges/bars is likely responsible for the large dispersion of sSFR in massive SFGs, while low-mass SFGs are mostly disk dominated and thus have a small dispersion. Our results suggest that star formation on galactic scales is dramatically affected by central dense structures through both enhancing and/or quenching processes, while lower-mass SFGs tend to have less bursty SFHs. However, the dispersion of the sSFR becomes significantly smaller and remains constant when only disk-dominated SFGs are counted. This finding implies that the impact of stochastic stellar feedback on star formation is likely to follow the same pattern in all disk galaxies, showing no correlation with halo potential.
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GOODS-Herschel: Star Formation, Dust Attenuation, and the FIR-radio Correlation on the Main Sequence of Star-forming Galaxies up to z ≃4 Pannella, M., Elbaz, D., Daddi, E., Dickinson, M., Hwang, H. S., Schreiber, C., Strazzullo, V., Aussel, H., Bethermin, M., Buat, V., Charmandaris, V., Cibinel, A., Juneau, S., Ivison, R. J., Le Borgne, D., Le Floc’h, E., Leiton, R., Lin, L., Magdis, G., Morrison, G. E., Mullaney, J., Onodera, M., Renzini, A., Salim, S., Sargent, M. T., Scott, D., Shu, X., and Wang, T. \apj 2015 [Abs] [ads] [arXiv]
We use deep panchromatic data sets in the GOODS-N field, from GALEX to the deepest Herschel far-infrared (FIR) and VLA radio continuum imaging, to explore the evolution of star-formation activity and dust attenuation properties of star-forming galaxies to z ≃ 4, using mass-complete samples. Our main results can be summarized as follows: (i) the slope of the star-formation rate-M_* correlation is consistent with being constant ≃0.8 up to z ≃ 1.5, while its normalization keeps increasing with redshift; (ii) for the first time we are able to explore the FIR-radio correlation for a mass-selected sample of star-forming galaxies: the correlation does not evolve up to z ≃ 4; (iii) we confirm that galaxy stellar mass is a robust proxy for UV dust attenuation in star-forming galaxies, with more massive galaxies being more dust attenuated. Strikingly, we find that this attenuation relation evolves very weakly with redshift, with the amount of dust attenuation increasing by less than 0.3 mag over the redshift range [0.5-4] for a fixed stellar mass; (iv) the correlation between dust attenuation and the UV spectral slope evolves with redshift, with the median UV slope becoming bluer with redshift. By z ≃ 3, typical UV slopes are inconsistent, given the measured dust attenuations, with the predictions of commonly used empirical laws. (v) Finally, building on existing results, we show that gas reddening is marginally larger (by a factor of around 1.3) than the stellar reddening at all redshifts probed. Our results support a scenario where the ISM conditions of typical star-forming galaxies evolve with redshift, such that at z \ensuremath≥ 1.5 Main Sequence galaxies have ISM conditions moving closer to those of local starbursts. Based on observations collected at the Herschel, Spitzer, Keck, NRAO-VLA, Subaru, KPNO, and CFHT observatories. Herschel is an European Space Agency Cornerstone Mission with science instruments provided by European-led Principal Investigator consortia and with significant participation by NASA. The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc.
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The Herschel view of the dominant mode of galaxy growth from z = 4 to the present day Schreiber, C., Pannella, M., Elbaz, D., Béthermin, M., Inami, H., Dickinson, M., Magnelli, B., Wang, T., Aussel, H., Daddi, E., Juneau, S., Shu, X., Sargent, M. T., Buat, V., Faber, S. M., Ferguson, H. C., Giavalisco, M., Koekemoer, A. M., Magdis, G., Morrison, G. E., Papovich, C., Santini, P., and Scott, D. \aap 2015 [Abs] [ads] [arXiv]
We present an analysis of the deepest Herschel images in four major extragalactic fields GOODS-North, GOODS-South, UDS, and COSMOS obtained within the GOODS-Herschel and CANDELS-Herschel key programs. The star formation picture provided by a total of 10 497 individual far-infrared detections is supplemented by the stacking analysis of a mass complete sample of 62 361 star- forming galaxies from the Hubble Space Telescope (HST) H band- selected catalogs of the CANDELS survey and from two deep ground-based K_s band-selected catalogs in the GOODS-North and the COSMOS-wide field to obtain one of the most accurate and unbiased understanding to date of the stellar mass growth over the cosmic history. We show, for the first time, that stacking also provides a powerful tool to determine the dispersion of a physical correlation and describe our method called “scatter stacking”, which may be easily generalized to other experiments. The combination of direct UV and far-infrared UV- reprocessed light provides a complete census on the star formation rates (SFRs), allowing us to demonstrate that galaxies at z = 4 to 0 of all stellar masses (M_\ensuremath*) follow a universal scaling law, the so-called main sequence of star-forming galaxies. We find a universal close-to-linear slope of the log _10(SFR)-log _10(M_\ensuremath*) relation, with evidence for a flattening of the main sequence at high masses (log _10(M_\ensuremath*/M_☉) > 10.5) that becomesless prominent with increasing redshift and almost vanishes by z ≃ 2. This flattening may be due to the parallel stellar growth of quiescent bulges in star-forming galaxies, which mostly happens over the same redshift range. Within the main sequence, we measure a nonvarying SFR dispersion of 0.3 dex: at a fixed redshift and stellar mass, about 68% of star-forming galaxies form stars at a universal rate within a factor 2. The specific SFR (sSFR = SFR/M_\ensuremath*) of star-forming galaxies is found to continuously increase from z = 0 to 4. Finally we discuss the implications of our findings on the cosmic SFR history and on the origin of present-day stars: more than two-thirds of present-day stars must have formed in a regime dominated by the “main sequence” mode. As a consequence we conclude that, although omnipresent in the distant Universe, galaxy mergers had little impact in shaping the global star formation history over the last 12.5 billion years. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.Appendices are available in electronic form at <A href=“http://www.aanda.o rg/10.1051/0004-6361/201425017/olm”>http://www.aanda.org</A>
2014
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Fast radio bursts as a cosmic probe? Zhou, Bei, Li, Xiang, Wang, Tao, Fan, Yi-Zhong, and Wei, Da-Ming \prd 2014 [Abs] [ads] [arXiv]
We discuss the possibility of using fast radio bursts (FRBs)—if cosmological—as a viable cosmic probe. We find that the contribution of the host galaxies to the detected dispersion measures can be inapparent for the FRBs that are not from galaxy centers or star-forming regions. The inhomogeneity of the intergalactic medium (IGM), however, causes significant deviation of the dispersion measure from that predicted in the simplified homogeneous IGM model for an individual event. Fortunately, with sufficient FRBs along different sightlines but within a very narrow redshift interval (e.g., \ensuremath∆z ̃0.05), the mean obtained from averaging observed dispersion measures does not suffer such a problem and hence may be used as a cosmic probe. We show that in the optimistic case (e.g., about 20 FRBs in each \ensuremath∆z have been measured; the most distant FRBs were at redshift \ensuremath≥3; the host galaxies and the FRB sources contribute little to the detected dispersion measures) and with all the uncertainties (i.e., the inhomogeneity of the IGM, the contribution and uncertainty of host galaxies, and the evolution and error of f_IGM) considered, FRBs could help constrain the equation of state of dark energy.
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Selection and Mid-infrared Spectroscopy of Ultraluminous Star-forming Galaxies at z \raisebox-0.5ex~2 Fang, Guanwen, Huang, Jia-Sheng, Willner, S. P., Kong, Xu, Wang, Tao, Chen, Yang, and Lin, Xuanbin \apj 2014 [Abs] [ads] [arXiv]
Starting from a sample of 24 \ensuremathμm sources in the Extended Groth Strip, we use 3.6-8 \ensuremathμm color criteria to select ultraluminous infrared galaxies (ULIRGs) at z \raisebox-0.5ex~2. Spectroscopy from 20-38 \ensuremathμm of 14 objects verifies their nature and gives their redshifts. Multi-wavelength data for these objects imply stellar masses >10^11 M _☉ and star formation rates >=410 M _☉ yr^-1. Four objects of this sample observed at 1.6 \ensuremathμm (rest-frame visible) with Hubble Space Telescope/WFC3 show diverse morphologies, suggesting that multiple formation processes create ULIRGs. Of the 14 objects, 4 show signs of active galactic nuclei, but the luminosity appears to be dominated by star formation in all cases.
2013
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Diffuse PeV neutrino emission from ultraluminous infrared galaxies He, Hao-Ning, Wang, Tao, Fan, Yi-Zhong, Liu, Si-Ming, and Wei, Da-Ming \prd 2013 [Abs] [ads] [arXiv]
Ultraluminous infrared galaxies (ULIRGs) are the most luminous and intense starburst galaxies in the Universe. Both their star formation rates and their gas surface mass densities are very high, implying a high supernova rate and an efficient energy conversion of energetic protons. A small fraction of these supernovae are the so-called hypernovae, with a typical kinetic energy ̃10^52erg and a shock velocity \ensuremath≥10^9cms^-1. The strong shocks driven by hypernovae are able to accelerate cosmic ray protons up to 10^17eV. These energetic protons lose a good fraction of their energy through proton-proton collision when ejected into very dense interstellar media, and as a result, produce high-energy neutrinos (\ensuremath≤5PeV). Recent deep infrared surveys provide solid constraints on the number density of ULIRGs across a wide redshift range 0\ensuremath≤z\ensuremath≤2.3, allowing us to derive the flux of diffuse neutrinos from hypernovae. We find that at PeV energies, the diffuse neutrinos contributed by ULIRGs are comparable to atmosphere neutrinos with the flux of 2\texttimes10^-9GeVcm^-2s^-1sr^-1 by assuming the injected cosmic ray spectrum to be dN_p^’/d\ensurem ath∈_p^’\ensuremath∝\ensuremath∈_ p^’-2.
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Multi-Wavelength Study of a Complete IRAC 3.6 \ensuremathμm Selected Galaxy Sample: A Fair Census of Red and Blue Populations at Redshifts 0.4-1.2 Huang, J. -S., Faber, S. M., Willmer, C. N. A., Rigopoulou, D., Koo, D., Newman, J., Shu, C., Ashby, M. L. N., Barmby, P., Coil, A., Luo, Z., Magdis, G., Wang, T., Weiner, B., Willner, S. P., Zheng, X. Z., and Fazio, G. G. \apj 2013 [Abs] [ads] [arXiv]
We present a multi-wavelength study of a 3.6 \ensuremathμm selected galaxy sample in the Extended Groth Strip (EGS). The sample is complete for galaxies with stellar mass >10^9.5 M _☉ and redshift 0.4 < z < 1.2. In this redshift range, the Infrared Array Camera 3.6 \ensuremathμm band measures the rest-frame near-infrared band, permitting nearly unbiased selection with respect to both quiescent and star-forming galaxies. The numerous spectroscopic redshifts available in the EGS are used to train an artificial neural network to estimate photometric redshifts. The distribution of photometric redshift errors is Gaussian with standard deviation \raisebox-0.5ex\textasciitilde0.025(1 + z), and the fraction of redshift failures (>3\ensuremathσ errors) is about 3.5%. A new method of validation based on pair statistics confirms the estimate of standard deviation even for galaxies lacking spectroscopic redshifts. Basic galaxy properties measured include rest-frame U - B colors, B- and K-band absolute magnitudes, and stellar masses. We divide the sample into quiescent and star-forming galaxies according to their rest- frame U - B colors and 24-3.6 \ensuremathμm flux density ratios and derive rest K-band luminosity functions and stellar mass functions for quiescent, star-forming, and all galaxies. The results show that massive, quiescent galaxies were in place by z \ensuremath≈ 1, but lower mass galaxies generally ceased their star formation at later epochs.
2012
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CANDELS: Correlations of Spectral Energy Distributions and Morphologies with Star formation Status for Massive Galaxies at z \raisebox-0.5ex~2 Wang, Tao, Huang, Jia-Sheng, Faber, S. M., Fang, Guanwen, Wuyts, Stijn, Fazio, G. G., Yan, Haojing, Dekel, Avishai, Guo, Yicheng, Ferguson, Henry C., Grogin, Norman, Lotz, Jennifer M., Weiner, Benjamin, McGrath, Elizabeth J., Kocevski, Dale, Hathi, Nimish P., Lucas, Ray A., Koekemoer, A. M., Kong, Xu, and Gu, Qiu-Sheng \apj 2012 [Abs] [ads] [arXiv]
We present a study on spectral energy distributions, morphologies, and star formation for an IRAC-selected extremely red object sample in the GOODS Chandra Deep Field-South. This work was enabled by new HST/WFC3 near-IR imaging from the CANDELS survey as well as the deepest available X-ray data from Chandra 4 Ms observations. This sample consists of 133 objects with the 3.6 \ensuremathμm limiting magnitude of [3.6] = 21.5 and is approximately complete for galaxies with M _* > 10^11 M _☉ at 1.5 <= z <= 2.5. We classify this sample into two types, quiescent and star-forming galaxies (SFGs), in the observed infrared color-color ([3.6]-[24] versus K - [3.6]) diagram. The further morphological study of this sample shows a consistent result with the observed color classification. The classified quiescent galaxies are bulge dominated and SFGs in the sample have disk or irregular morphologies. Our observed infrared color classification is also consistent with the rest-frame color (U - V versus V - J) classification. We also found that quiescent and SFGs are well separated in the nonparametric morphology parameter (Gini versus M _20) diagram measuring their concentration and clumpiness: quiescent galaxies have a Gini coefficient higher than 0.58 and SFGs have a Gini coefficient lower than 0.58. We argue that the star formation quenching process must lead to or be accompanied by the increasing galaxy concentration. One prominent morphological feature of this sample is that disks are commonly seen in this massive galaxy sample at 1.5 <= z <= 2.5: 30% of quiescent galaxies and 70% of SFGs with M _* > 10^11 M _☉ have disks in their rest-frame optical morphologies. The prevalence of these extended, relatively undisturbed disks challenges the merging scenario as the main mode of massive galaxy formation.
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On the Nature of the Progenitor of the Type Ia SN2011fe in M101 Liu, Jifeng, Di Stefano, Rosanne, Wang, Tao, and Moe, Maxwell \apj 2012 [Abs] [ads] [arXiv]
The explosion of a Type Ia supernova, SN2011fe, in the nearby Pinwheel galaxy (M101 at 6.4 Mpc) provides an opportunity to study pre- explosion images and search for the progenitor, which should consist of a white dwarf (WD), possibly surrounded by an accretion disk, in orbit with another star. We report on our use of deep Chandra observations and Hubble Space Telescope observations to limit the luminosity and temperature of the pre- explosion WD. It is found that if the spectrum was a blackbody, then pre-SN WDs with steady nuclear burning of the highest possible temperatures and luminosities are excluded assuming moderate n _H values, but values of kT between roughly 10 eV and 60 eV are permitted even if the WD was emitting at the Eddington luminosity. This allows the progenitor to be an accreting nuclear-burning WD with an expanded photosphere 4-100 times the WD itself, or a super-critically accreting WD blowing off an optically thick strong wind, or possibly a recurrent nova with luminosities an order of magnitude lower than Eddington. The observations are also consistent with a double degenerate scenario, or a spinning down WD that has been spun up by accretion from the donor.
2011
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Oxford SWIFT integral field spectrograph and multiwavelength observations of the Eagle galaxy at z= 0.77 Kassin, Susan A., Fogarty, L., Goodsall, T., Clarke, F. J., Houghton, R. W. C., Salter, G., Thatte, N., Tecza, M., Davies, Roger L., Weiner, Benjamin J., Willmer, C. N. A., Salim, Samir, Cooper, Michael C., Newman, Jeffrey A., Bundy, Kevin, Conselice, C. J., Koekemoer, A. M., Lin, Lihwai, Moustakas, Leonidas A., and Wang, Tao \mnras 2011 [Abs] [ads] [arXiv]
The ‘Eagle’ galaxy at a redshift of 0.77 is studied with the Oxford Short Wavelength Integral Field Spectrograph (SWIFT) and multiwavelength data from the All-wavelength Extended Groth strip International Survey (AEGIS). It was chosen from AEGIS because of the bright and extended emission in its slit spectrum. 3D kinematic maps of the Eagle reveal a gradient in velocity dispersion which spans 35-75 \ensuremath\pm 10 km s^-1 and a rotation velocity of 25 \ensuremath\pm 5 km s^-1 uncorrected for inclination. Hubble Space Telescope images suggest it is close to face-on. In comparison with galaxies from AEGIS at similar redshifts, the Eagle is extremely bright and blue in the rest-frame optical, highly star forming, dominated by unobscured star formation and has a low metallicity for its size. This is consistent with its selection. The Eagle is likely undergoing a major merger and is caught in the early stage of a starburst when it has not yet experienced metal enrichment or formed the mass of dust typically found in star- forming galaxies.
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Four IRAC Sources with an Extremely Red H - [3.6] Color: Passive or Dusty Galaxies at z > 4.5? Huang, J. -S., Zheng, X. Z., Rigopoulou, D., Magdis, G., Fazio, G. G., and Wang, T. \apjl 2011 [Abs] [ads] [arXiv]
We report the detection of four IRAC sources in the GOODS-South field with an extremely red color of H - [3.6] > 4.5. The four sources are not detected in the deep Hubble Space Telescope WFC3 H-band image with H _limit = 28.3 mag. We find that only three types of SED templates can produce such a red H - [3.6] color: a very dusty SED with the Calzetti extinction of A_V = 16 mag at z = 0.8; a very dusty SED with the SMC extinction of A_V = 8 mag at z = 2.0- 2.2; and an 1 Gyr SSP with A_V \raisebox-0.5ex~0.8 at z = 5.7. We argue that these sources are unlikely dusty galaxies at z <= 2.2 based on absent strong MIPS 24 \ensuremathμm emission. The old stellar population model at z > 4.5 remains a possible solution for the 4 sources. At z > 4.5, these sources have stellar masses of log(M _*/M _☉) = 10.6-11.2. One source, ERS-1, is also a type-II X-ray QSO with L _2 - 8 keV = 1.6 \texttimes 10^44 erg s^-1. One of the four sources is an X-ray QSO and another one is a HyperLIRG, suggesting a galaxy-merging scenario for the formation of these massive galaxies at high redshifts.
2009
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Photometric redshifts of galaxies from SDSS and 2MASS Wang, Tao, Huang, Jia-Sheng, and Gu, Qiu-Sheng Research in Astronomy and Astrophysics 2009 [Abs] [ads]
In order to find the physical parameters which determine the accuracy of photometric redshifts, we compare the spectroscopic and photometric redshifts (photo-z’s) for a large sample of \raisebox-0.5ex~80000 SDSS-2MASS galaxies. Photo-z’s in this paper are estimated by using the artificial neural network photometric redshift method (ANNz). For a subset of \raisebox-0.5ex\textasciitilde40000 randomly selected galaxies, we find that the photometric redshift recovers the spectroscopic redshift distribution very well with rms of 0.016. Our main results are as follows: (1) Using magnitudes directly as input parameters produces more accurate photo-z’s than using colors; (2) The inclusion of 2MASS (J, H, K_s) bands does not improve photo-z’s significantly, which indicates that near infrared data might not be important for the low-redshift sample; (3) Adding the concentration index (essentially the steepness of the galaxy brightness profile) as an extra input can improve the photo-z’s estimation up to \raisebox-0.5ex~10 percent; (4) Dividing the sample into early- and late-type galaxies by using the concentration index, normal and abnormal galaxies by using the emission line flux ratios, and red and blue galaxies by using color index (g - r), we can improve the accuracy of photo-z’s significantly; (5) Our analysis shows that the outliers (where there is a big difference between the spectroscopic and photometric redshifts) are mainly correlated with galaxy types, e.g., most outliers are late-type (blue) galaxies.