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© 2012 The Authors. © 2012 Monthly Notices of the Royal Astronomical Society © 2012 RAS. We thank the anonymous referee for a careful and constructive reading of the manuscript that helped us to improve the quality of the paper. We are grateful to Lulu Liu for providing us with their measurements of the fraction of galaxies with satellites obtained from the SDSS, used here as a local (z = 0) comparison. We thank Juan Betancort for his valuable input on several aspects of the statistical analysis in this paper. We are grateful to Sergio Pascual for his very useful help with programming questions. We would like also to acknowledge fruitful discussions with Javier Cenarro, Luis Díaz, Rosa Domínguez, César González, Carlos López San Juan, José Onorbe, Thorsten Naab and Vicent Quilis. IT is a Ramón y Cajal Fellow of the Spanish Ministry of Science and Innovation. This work has been supported by the 'Programa Nacional de Astronomía y Astrofísica' of the Spanish Ministry of Science and Innovation under grant AYA2010-21322-C03-02. PGP and GB acknowledge support from the Spanish Programa Nacional de Astronomía y Astrofísica under grants AYA2009-10368 and AYA2009-07723-E. This work has made use of the Rainbow Cosmological Surveys Data base, which is operated by the Universidad Complutense de Madrid (UCM)., The accretion of minor satellites has been postulated as the most likely mechanism to explain the significant size evolution of massive galaxies over cosmic time. Using a sample of 629 massive (M_star~ 10^11 M_⊙) galaxies from the near-infrared Palomar/DEEP-2 survey, we explore what fraction of these objects have satellites with 0.01 < M_sat/M_central < 1 (1:100) up to z= 1 and what fraction have satellites with 0.1 < M_sat/M_central < 1 (1:10) up to z= 2 within a projected radial distance of 100 kpc. We find that the fraction of massive galaxies with satellites, after background correction, remains basically constant and close to 30 per cent for satellites with a mass ratio down to 1:100 up to z= 1, and close to 15 per cent for satellites with a 1:10 mass ratio up to z= 2. The family of spheroid-like massive galaxies presents a 2–3 times larger fraction of objects with satellites than the group of disc-like massive galaxies. A crude estimation of the number of 1:3 mergers a massive spheroid-like galaxy has experienced since z~2 is around 2. For a disc-like galaxy this number decreases to ~1., Ministerio de Ciencia e Innovación (MICINN), Programa Nacional de Astronomía y Astrofísica (PNAyA), España, Depto. de Física de la Tierra y Astrofísica, Fac. de Ciencias Físicas, TRUE, pub

© 2015 RAS. We thank the referee for helpful comments that have improved this paper. We also thank Johannes Buchner for helpful discussions and providing machine-readable results. We acknowledge helpful discussions with Ranjan Vasudevan. The scientific results reported in this article are based to a significant degree on observations made by the Chandra X-ray Observatory. This work has made use of the Rainbow Cosmological Surveys Database, which is operated by the Universidad Complutense de Madrid (UCM). This study makes use of data from AEGIS, a multiwavelength sky survey conducted with the Chandra, GALEX, Hubble, Keck, CFHT, MMT, Subaru, Palomar, Spitzer, VLA, and other telescopes and supported in part by the National Science Foundation (NSF), NASA, and the STFC. Funding for the DEEP2 Galaxy Redshift Survey has been provided by NSF grants AST-95-09298, AST-0071048, AST-0507428, and AST-0507483 as well as NASA LTSA grant NNG04GC89G. Funding for the DEEP3 Galaxy Redshift Survey has been provided by NSF grants AST-0808133, AST-0807630, and AST-0806732. This work made use of images and/or data products provided by the NDWFS (Jannuzi & Dey 1999), which is supported by the National Optical Astronomy Observatory (NOAO). NOAO is operated by AURA, Inc., under a cooperative agreement with the NSF. Funding for SDSS-III has been provided by the Alfred P. Sloan Foundation, the Participating Institutions, the NSF, and the US Department of Energy Office of Science. The SDSS-III web site is http://www.sdss3.org/. SDSS-III is managed by the Astrophysical Research Consortium for the Participating Institutions of the SDSS-III Collaboration. Based in part on data collected at Subaru Telescope, which is operated by the National Astronomical Observatory of Japan. This work is based in part on observations made with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, California Institute of Technology under a contract with NASA. Some of the data used in this, We present new measurements of the evolution of the X-ray luminosity functions (XLFs) of unabsorbed and absorbed active galactic nuclei (AGNs) out to z ~ 5. We construct samples containing 2957 sources detected at hard (2-7 keV) X-ray energies and 4351 sources detected at soft (0.5-2 keV) energies from a compilation of Chandra surveys supplemented by wide-area surveys from ASCA and ROSAT. We consider the hard and soft X-ray samples separately and find that the XLF based on either (initially neglecting absorption effects) is best described by a new flexible model parametrization where the break luminosity, normalization, and faint-end slope all evolve with redshift. We then incorporate absorption effects, separately-modelling the evolution of the XLFs of unabsorbed (20 < log N_H < 22) and absorbed (22 < log N_H < 24) AGNs, seeking a model that can reconcile both the hard-and soft-band samples. We find that the absorbed AGN XLF has a lower break luminosity, a higher normalization, and a steeper faint-end slope than the unabsorbed AGN XLF out to z ~ 2. Hence, absorbed AGNs dominate at low luminosities, with the absorbed fraction falling rapidly as luminosity increases. Both XLFs undergo strong luminosity evolution which shifts the transition in the absorbed fraction to higher luminosities at higher redshifts. The evolution in the shape of the total XLF is primarily driven by the changing mix of unabsorbed and absorbed populations., Unión Europea (UE), Ministerio de Economía y Competitividad (MINECO), España, National Science Foundation (NSF), National Aeronautics and Space Administration (NASA), EE.UU., Science and Technology Facilities Council (STFC), Long Term Space Astrophysics Program (LTSA-NASA), National Optical Astronomy Observatory (NOAO), Alfred P. Sloan Foundation, US Department of Energy Office of Science, NASA Office of Space Science, COFUND Junior Research Fellowship from the Institute of Advanced Study, Durham University, ERC Advanced Grant FEEDBACK at the University of Cambridge, NSF CAREER, Greek Government, Depto. de Física de la Tierra y Astrofísica, Fac. de Ciencias Físicas, TRUE, pub

© 2013 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society. The authors acknowledge the referee's comments, which led to improvements in this work. They also thank Carlos Hernández Monteagudo for his very useful advice. LADG acknowledges support from the 'Caja Rural de Teruel' to develop this research. AJC is a Ramón y Cajal Fellow of the Spanish Ministry of Economy and Competitiveness. This work was supported by the 'Programa Nacional de Astronomía y Astrofísica' of the Spanish Ministry of Economy and Competitiveness under grants AYA2012-30789, AYA2010-21322-C03-02, AYA2009-10368 and AYA2009-07723-E. This work made use of the Rainbow Cosmological Surveys Database, which is operated by the Universidad Complutense de Madrid (UCM)., Using a compilation of 379 massive (stellar mass M ≳ 10^11 M_⊙) spheroid-like galaxies from the near-infrared Palomar/DEEP-2 survey, we investigated, up to z ∼ 1, whether the presence of companions depends on the size of the host galaxy. We explored the presence of companions for mass ratios with respect to the central massive galaxy down to 1 : 10 and 1 : 100, and within projected distances of 30, 50 and 100 kpc of these objects. We found evidence that these companions are equally distributed around both compact and extended massive spheroid-like galaxies. This suggests that, at least since z ∼ 1, the merger activity in these objects is nearly homogeneous across the whole population and that the merger history is not affected by the size of the host galaxy. Our results could indicate that compact and extended massive spheroid-like galaxies are increasing in size at the same rate., Ministerio de Economía y Competitividad (MINECO), Caja Rural de Teruel, Programa Nacional de Astronomía y Astrofísica (PNAyA), España, Depto. de Física de la Tierra y Astrofísica, Fac. de Ciencias Físicas, TRUE, pub

© 2010 The Authors. Journal compilation, © 2010 RAS. The authors wish to thank the anonymous referee for constructive suggestions that improved the paper and Alison Coil for useful comments. AG acknowledges financial support from the Marie-Curie Reintegration Grant PERG03-GA-2008-230644. PGP-G acknowledges support from the Spanish Ministry of Science and Innovation under grants AYA 2006-02358, AYA 2006-15698-C02-02 and CSD2006-100070, and from the Ramón y Cajal Program financed by the Spanish Government and the European Union. This study makes use of data from AEGIS, a multiwavelength sky survey conducted with the Chandra, GALEX, Hubble, Keck, CFHT, MMT, Subaru, Palomar, Spitzer, VLA and other telescopes and supported in part by the NSF, NASA and the STFC., We explore the nature of Infrared Excess sources (IRX), which are proposed as candidates for luminous [L_X(2–10 keV) > 10^43 erg s^−1] Compton thick (NH > 2 × 1024 cm−2) QSOs at z≈ 2. Lower redshift, z≈ 1, analogues of the distant IRX population are identified by first redshifting to z= 2 the spectral energy distributions (SEDs) of all sources with secure spectroscopic redshifts in the AEGIS (6488) and the GOODS-North (1784) surveys and then selecting those that qualify as IRX sources at that redshift. A total of 19 galaxies are selected. The mean redshift of the sample is z≈ 1. We do not find strong evidence for Compton thick QSOs in the sample. For nine sources with X-ray counterparts, the X-ray spectra are consistent with Compton thin active galactic nucleus (AGN). Only three of them show tentative evidence for Compton thick obscuration. The SEDs of the X-ray undetected population are consistent with starburst activity. There is no evidence for a hot dust component at the mid-infrared associated with AGN heated dust. If the X-ray undetected sources host AGN, an upper limit of L_X(2–10 keV) = 10^43 erg s^−1 is estimated for their intrinsic luminosity. We propose that a large fraction of the z≈ 2 IRX population is not Compton thick quasi-stellar objects (QSOs) but low-luminosity [L_X(2–10 keV) < 10^43 erg s^−1], possibly Compton thin, AGN or dusty starbursts. It is shown that the decomposition of the AGN and starburst contribution to the mid-IR is essential for interpreting the nature of this population, as star formation may dominate this wavelength regime., Unión Europea. FP7, Ministerio de Ciencia e Innovación (MICINN), Acciones Marie Skłodowska-Curie (UE), Gobierno de España, National Science Foundation (NSF), EE.UU., National Aeronautics and Space Administration (NASA), Science and Technology Facilities Council (STFC), Reino Unido, Depto. de Física de la Tierra y Astrofísica, Fac. de Ciencias Físicas, TRUE, pub

© 2016 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society. Thanks to R. Sheth for comments on an early draft. Thanks to the anonymous referee for a constructive and quick report., We quantify the evolution of the stellar mass functions (SMFs) of star-forming and quiescent galaxies as a function of morphology from z ∼ 3 to the present. Our sample consists of ∼50 000 galaxies in the CANDELS fields (∼880 arcmin^2), which we divide into four main morphological types, i.e. pure bulge-dominated systems, pure spiral disc-dominated, intermediate two-component bulge+disc systems and irregular disturbed galaxies. At z ∼ 2, 80 per cent of the stellar mass density of star-forming galaxies is in irregular systems. However, by z ∼ 0.5, irregular objects only dominate at stellar masses below 10^9 M_⊙. A majority of the star-forming irregulars present at z ∼ 2 undergo a gradual transformation from disturbed to normal spiral disc morphologies by z ∼ 1 without significant interruption to their star formation. Rejuvenation after a quenching event does not seem to be common except perhaps for the most massive objects, because the fraction of bulge-dominated star-forming galaxies with M^*/M_⊙ > 10^10.7 reaches 40 per cent at z < 1. Quenching implies the presence of a bulge: the abundance of massive red discs is negligible at all redshifts over 2 dex in stellar mass. However, the dominant quenching mechanism evolves. At z > 2, the SMF of quiescent galaxies above M^* is dominated by compact spheroids. Quenching at this early epoch destroys the disc and produces a compact remnant unless the star-forming progenitors at even higher redshifts are significantly more dense. At 1 < z < 2, the majority of newly quenched galaxies are discs with a significant central bulge. This suggests that mass quenching at this epoch starts from the inner parts and preserves the disc. At z < 1, the high-mass end of the passive SMF is globally in place and the evolution mostly happens at stellar masses below 10^10 M_⊙. These low-mass galaxies are compact, bulge-dominated systems, which were environmentally quenched: destruction of the disc through ram-pressure stripping is the likely proc, Depto. de Física de la Tierra y Astrofísica, Fac. de Ciencias Físicas, TRUE, pub

© 2011 The Authors. © 201Monthly Notices of the Royal Astronomical Society. © 2011 RAS. CRA acknowledges financial support from STFC PDRA (ST/G001758/1). CRA, PGPG and GB acknowledge the Spanish Ministry of Science and Innovation (MICINN) through project Consolider-Ingenio 2010 Program grant CSD2006-00070: First Science with the GTC (http://www.iac.es/consolider-ingenio-gtc/). PGPG and GB acknowledge support from the Spanish Programa Nacional de Astronomía y Astrofísica under grants AYA2009-10368 and AYA2009-07723-E. KJI is supported through the Emmy Noether programme of the German Science Foundation (DFG). This work has made use of the Rainbow Cosmological Surveys Data base, which is operated by the Universidad Complutense de Madrid (UCM). This work is based in part on data collected at Subaru Telescope, which is operated by the National Astronomical Observatory of Japan. This research has made use of the NED which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration. The authors specially acknowledge Tomer Tal for providing access to the OBEY images, as well as David Carter, Richard Pogge, Philip Massey, Giovanni Carraro and Carlos López SanJuan for their valuable help. We finally acknowledge useful comments from the anonymous referee., We present the results of a comparison between the optical morphologies of a complete sample of 46 southern 2 Jy radio galaxies at intermediate redshifts (0.05 < z < 0.7) and those of two control samples of quiescent early-type galaxies: 55 ellipticals at redshifts z ≤ 0.01 from the Observations of Bright Ellipticals at Yale (OBEY) survey, and 107 early-type galaxies at redshifts 0.2 < z < 0.7 in the Extended Groth Strip (EGS). Based on these comparisons, we discuss the role of galaxy interactions in the triggering of powerful radio galaxies (PRGs). We find that a significant fraction of quiescent ellipticals at low and intermediate redshifts show evidence for disturbed morphologies at relatively high surface brightness levels, which are likely the result of past or on-going galaxy interactions. However, the morphological features detected in the galaxy hosts of the PRGs (e.g. tidal tails, shells, bridges, etc.) are up to 2 mag brighter than those present in their quiescent counterparts. Indeed, if we consider the same surface brightness limits, the fraction of disturbed morphologies is considerably smaller in the quiescent population (53 per cent at z < 0.2 and 48 per cent at 0.2 ≤ z < 0.7) than in the PRGs (93 per cent at z < 0.2 and 95 per cent at 0.2 ≤ z < 0.7 considering strong-line radio galaxies only). This supports a scenario in which PRGs represent a fleeting active phase of a subset of the elliptical galaxies that have recently undergone mergers/interactions. However, we demonstrate that only a small proportion (≲20 per cent) of disturbed early-type galaxies are capable of hosting powerful radio sources., Ministerio de Ciencia e Innovación (MICINN), Science and Technology Facilities Council (STFC), Reino Unido, Programa Nacional de Astronomía y Astrofísica (PNAyA), España, Deutsche Forschungsgemeinschaft (DFG), Alemania, National Aeronautics and Space Administration (NASA), Depto. de Física de la Tierra y Astrofísica, Fac. de Ciencias Físicas, TRUE, pub