Seds: The Spitzer Extended Deep Survey. Survey Design, Photometry, and Deep Irac Source Counts

Ashby, M. L. N.; Willner, S. P.; Fazio, G. G.; Huang, Jia-Sheng; Arendt, Richard G.; Barmby, P.; Barro, Guillermo; Bell, Eric F.; Bouwens, Rychard; Cattaneo, Andrea; Croton, Darren J.; Davé, Romeel; Dunlop, James; Egami, Eiichi; Faber, S. M.; Finlator, Kristian; Grogin, Norman A.; Guhathakurta, Puragra; Hernquist, L.; Hora, J. L.; Illingworth, G. D.; Kashlinsky, A.; Koekemoer, Anton M.; Koo, David C.; Labbé, Ivo; Li, Yuexing; Lin, Lihwai; Moseley, H.; Nandra, K.; Newman, Jeffrey A.; Noeske, K. G.; Ouchi, Masami; Peth, Michael; Rigopoulou, D.; Robertson, Brant; Sarajedini, Vicki L.; Simard, Luc; Smith, H. A.; Wang, Z.; Wechsler, Risa H.; Weiner, Benjamin J.; Wilson, Gillian; Wuyts, Stijn; Yamada, Tōru; Yan, Haojing

doi:10.1088/0004-637x/769/1/80

Cited by 248 publications

(172 citation statements)

References 67 publications

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“…redshifts. For identification of counterparts, the J/K/H-band positions from the CANDELS (Koekemoer et al 2011;Grogin et al 2012) CDFS field (Guo et al 2013;Hsieh et al 2012) are used in combination with midinfrared positions from IRAC (Damen et al 2011;Ashby et al 2013). A Bayesian method was developed that matches X-ray positions to mid-and near-infrared counterparts simultaneously (Budavári & Szalay 2008;Salvato et al in prep).…”

Section: Observational Datamentioning

confidence: 99%

X-ray spectral modelling of the AGN obscuring region in the CDFS: Bayesian model selection and catalogue

Buchner

Georgakakis

Nandra

et al. 2014

A&A

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1,452

1,263

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Aims. Active galactic nuclei are known to have complex X-ray spectra that depend on both the properties of the accreting super-massive black hole (e.g. mass, accretion rate) and the distribution of obscuring material in its vicinity (i.e. the "torus"). Often however, simple and even unphysical models are adopted to represent the X-ray spectra of AGN, which do not capture the complexity and diversity of the observations. In the case of blank field surveys in particular, this should have an impact on e.g. the determination of the AGN luminosity function, the inferred accretion history of the Universe and also on our understanding of the relation between AGN and their host galaxies. Methods. We develop a Bayesian framework for model comparison and parameter estimation of X-ray spectra. We take into account uncertainties associated with both the Poisson nature of X-ray data and the determination of source redshift using photometric methods. We also demonstrate how Bayesian model comparison can be used to select among ten different physically motivated X-ray spectral models the one that provides a better representation of the observations. This methodology is applied to X-ray AGN in the 4 Ms Chandra Deep Field South. Results. For the ∼350 AGN in that field, our analysis identifies four components needed to represent the diversity of the observed X-ray spectra: (1) an intrinsic power law; (2) a cold obscurer which reprocesses the radiation due to photo-electric absorption, Compton scattering and Fe-K fluorescence; (3) an unabsorbed power law associated with Thomson scattering off ionised clouds; and (4) Compton reflection, most noticeable from a stronger-than-expected Fe-K line. Simpler models, such as a photo-electrically absorbed power law with a Thomson scattering component, are ruled out with decisive evidence (B > 100). We also find that ignoring the Thomson scattering component results in underestimation of the inferred column density, N H , of the obscurer. Regarding the geometry of the obscurer, there is strong evidence against both a completely closed (e.g. sphere), or entirely open (e.g. blob of material along the line of sight), toroidal geometry in favour of an intermediate case.Conclusions. Despite the use of low-count spectra, our methodology is able to draw strong inferences on the geometry of the torus. Simpler models are ruled out in favour of a geometrically extended structure with significant Compton scattering. We confirm the presence of a soft component, possibly associated with Thomson scattering off ionised clouds in the opening angle of the torus. The additional Compton reflection required by data over that predicted by toroidal geometry models, may be a sign of a density gradient in the torus or reflection off the accretion disk. Finally, we release a catalogue of AGN in the CDFS with estimated parameters such as the accretion luminosity in the 2−10 keV band and the column density, N H , of the obscurer.

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Section: Observational Datamentioning

confidence: 99%

X-ray spectral modelling of the AGN obscuring region in the CDFS: Bayesian model selection and catalogue

Buchner

Georgakakis

Nandra

et al. 2014

A&A

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1,452

1,263

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“…In particular, they include very deep imaging with the IRAC instrument aboard the Spitzer Space Telescope from the Spitzer Extended Deep Survey (SEDS; Ashby et al 2013), covering the CANDELS fields to a 3σ depth of 26 AB mag at both 3.6 and 4.5 μm, that are crucial for sampling the rest-frame optical bands at z > 4.…”

Section: The Photometric Data Setmentioning

confidence: 99%

“…Moreover, the physical properties of high-redshift galaxies, such as their star formation rates (SFR) and stellar masses, can now be determined with meaningful accuracy up to z 7−8 (Labbé et al 2010(Labbé et al , 2013, thanks to the combined power of deep space-based (HST, Spitzer) and ground-based (VLT) near-mid infrared imaging (Retzlaff et al 2010;Fontana et al 2014;Ashby et al 2013).…”

Section: Introductionmentioning

confidence: 99%

The galaxy stellar mass function at 3.5 ≤z≤ 7.5 in the CANDELS/UDS, GOODS-South, and HUDF fields

Grazian

Fontana

Santini

et al. 2015

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Context. The form and evolution of the galaxy stellar mass function (GSMF) at high redshifts provide crucial information on star formation history and mass assembly in the young Universe, close or even prior to the epoch of reionization. Aims. We used the unique combination of deep optical/near-infrared/mid-infrared imaging provided by HST, Spitzer, and the VLT in the CANDELS-UDS, GOODS-South, and HUDF fields to determine the GSMF over the redshift range 3.5 ≤ z ≤ 7.5. Methods. We used the HST WFC3/IR near-infrared imaging from CANDELS and HUDF09, reaching H 27−28.5 over a total area of 369 arcmin 2 , in combination with associated deep HST ACS optical data, deep Spitzer IRAC imaging from the SEDS programme, and deep Y and K-band VLT Hawk-I images from the HUGS programme, to select a galaxy sample with high-quality photometric redshifts. These have been calibrated with more than 150 spectroscopic redshifts in the range 3.5 ≤ z ≤ 7.5, resulting in an overall precision of σ z /(1 + z) ∼ 0.037. With this database we have determined the low-mass end of the high-redshift GSMF with unprecedented precision, reaching down to masses as low as M * ∼ 10 9 M at z = 4 and ∼6 × 10 9 M at z = 7. Results. We find that the GSMF at 3.5 ≤ z ≤ 7.5 depends only slightly on the recipes adopted to measure the stellar masses, namely the photometric redshifts, the star formation histories, the nebular contribution, or the presence of AGN in the parent sample. The low-mass end of the GSMF is steeper than has been found at lower redshifts, but appears to be unchanged over the redshift range probed here. Meanwhile the high-mass end of the GSMF appears to evolve primarily in density, although there is also some evidence of evolution in characteristic mass. Our results are very different from previous mass function estimates based on converting UV galaxy luminosity functions into mass functions via tight mass-to-light relations. Integrating our evolving GSMF over mass, we find that the growth of stellar mass density is barely consistent with the time-integral of the star formation rate density over cosmic time at z > 4. Conclusions. These results confirm the unique synergy of the CANDELS+HUDF, HUGS, and SEDS surveys for the discovery and study of moderate/low-mass galaxies at high redshifts, and reaffirm the importance of space-based infrared selection for the unbiased measurement of the evolving GSMF in the young Universe.

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“…At z = 3.1 MIR bands trace the lower mass stars which make up most of the baryonic mass in galaxies. Where available we obtained IRAC data for the HDF-N sample from Ashby et al (2013) and for the SSA22 sample from the Spitzer archive (originally from GO project 30328). Applying the Kolmogorov-Smirnov (K-S) test gave a p-value of 0.97 for [4.5] <24, (where both catalogues are approximately complete), confirming that the two samples have a statistically identical stellar mass distribution.…”

Section: Lyman-break Galaxy Sample Selectionmentioning

confidence: 99%

An enhanced merger fraction within the galaxy population of the SSA22 protocluster atz = 3.1

Hine

Geach

Alexander

et al. 2015

Mon. Not. R. Astron. Soc.

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The overdense environments of protoclusters of galaxies in the early Universe (z > 2) are expected to accelerate the evolution of galaxies, with an increased rate of stellar mass assembly and black hole accretion compared to co-eval galaxies in the average density 'field'. These galaxies are destined to form the passive population of massive galaxies that dominate the cores of rich clusters today. While signatures of the accelerated growth of galaxies in the SSA22 protocluster (z = 3.1) have been observed, the mechanism driving this remains unclear. Here we show an enhanced rate of galaxy-galaxy mergers could be responsible. We morphologically classify Lyman-break Galaxies (LBGs) in the SSA22 protocluster and compare these to those of galaxies in the field at z = 3.1 as either active mergers or non-merging using Hubble Space Telescope ACS/F814W imaging, probing the rest-frame ultraviolet stellar light. We measure a merger fraction of 48±10 per cent for LBGs in the protocluster compared to 30±6 per cent in the field. Although the excess is marginal, an enhanced rate of mergers in SSA22 hints that galaxy-galaxy mergers are one of the key channels driving accelerated star formation and AGN growth in protocluster environments.

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Seds: The Spitzer Extended Deep Survey. Survey Design, Photometry, and Deep Irac Source Counts

Cited by 248 publications

References 67 publications

X-ray spectral modelling of the AGN obscuring region in the CDFS: Bayesian model selection and catalogue

X-ray spectral modelling of the AGN obscuring region in the CDFS: Bayesian model selection and catalogue

The galaxy stellar mass function at 3.5 ≤z≤ 7.5 in the CANDELS/UDS, GOODS-South, and HUDF fields

An enhanced merger fraction within the galaxy population of the SSA22 protocluster atz = 3.1

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