CENSORS: A Combined EIS-NVSS Survey of Radio Sources - II. Infrared imaging and the K-z relation

Brookes, M. H.; Rengelink, R.; Röttgering, H. J. A.

doi:10.1111/j.1365-2966.2005.09916.x

Cited by 29 publications

(46 citation statements)

References 19 publications

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“…), which we refer to hereafter as the MRCR-SUMSS sample. The other is the sample of radio galaxies within the fields of the ESO imaging survey (EIS) by Best et al (2003) and Brookes et al (2006Brookes et al ( , 2008, which we call the "CENSORS" sample ("Combined EIS-NVSS Survey Of Radio Sources").…”

Section: Samplementioning

confidence: 99%

Kinematic signatures of AGN feedback in moderately powerful radio galaxies atz~ 2 observed with SINFONI

Collet

Nesvadba

Breuck

et al. 2016

A&A

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Most successful galaxy formation scenarios now postulate that the intense star formation in massive, high-redshift galaxies during their major growth period was truncated when powerful AGNs launched galaxy-wide outflows of gas that removed large parts of the interstellar medium. SINFONI imaging spectroscopy of the most powerful radio galaxies at z ∼ 2 show clear signatures of such winds, but are too rare to be good representatives of a generic phase in the evolution of all massive galaxies at high redshift. Here we present SINFONI imaging spectroscopy of the rest-frame optical emission-line gas in 12 radio galaxies at redshifts ∼2. Our sample spans a range in radio power that is intermediate between the most powerful radio galaxies with known wind signatures at these redshifts and vigorous starburst galaxies, and are about two orders of magnitude more common than the most powerful radio galaxies. Thus, if AGN feedback is a generic phase of massive galaxy evolution for reasonable values of the AGN duty cycle, these are just the sources where AGN feedback should be most important. Our sources show a diverse set of gas kinematics ranging from regular velocity gradients with amplitudes of Δv = 200−400 km s −1 consistent with rotating disks to very irregular kinematics with multiple velocity jumps of a few 100 km s −1 . Line widths are generally high, typically around FWHM = 800 km s −1 , more similar to the more powerful high-z radio galaxies than mass-selected samples of massive high-z galaxies without bright AGNs, and consistent with the velocity range expected from recent hydrodynamic models. A broad Hα line in one target implies a black hole mass of a few 10 9 M . Velocity offsets of putative satellite galaxies near a few targets suggest dynamical masses of a few 10 11 M for our sources, akin to the most powerful high-z radio galaxies. Ionized gas masses are 1−2 orders of magnitude lower than in the most powerful radio galaxies, and the extinction in the gas is relatively low, up to A V ∼ 2 mag. The ratio of line widths, σ, to bulk velocity, v, is so large that even the gas in galaxies with regular velocity fields is unlikely to be gravitationally bound. It is unclear, however, whether the large line widths are due to turbulence or unresolved, local outflows as are sometimes observed at low redshifts. We compare our sources with sets of radio galaxies at low and high redshift, finding that they may have more in common with gas-rich nearby radio galaxies with similar jet power than with the most powerful high-z radio galaxies. Comparison of the kinetic energy with the energy supply from the AGNs through jet and radiation pressure suggests that the radio source still plays a dominant role for feedback, consistent with low-redshift radio-loud quasars.

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Section: Samplementioning

confidence: 99%

Kinematic signatures of AGN feedback in moderately powerful radio galaxies atz~ 2 observed with SINFONI

Collet

Nesvadba

Breuck

et al. 2016

A&A

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“…The fit for 7C alone, which Brookes et al (2006) claim is similar to the fit they obtain for the CEN-SORS survey, is also plotted. A fit to our data, given by K=(17.9±0.1)+(4.3±0.3)log 10 z, is the line at faintest magnitudes.…”

Section: The K-z Relationmentioning

confidence: 72%

“…6 The K-band magnitude versus redshift for FIRST-NDWFS matches. The upper line gives our fit to the FIRST data, the more curved line is the fit to 7C sources, similar to that obtained by Brookes et al (2006) for the CENSORS survey, and the third line is the fit to the 3CRR, 6C and 7C combination Willott et al (2003).…”

Section: Photometric Redshift Distributionmentioning

confidence: 73%

“…This study has allowed the redshift distribution and nature of 1.4GHz sources with S>1mJy to be studied fairly well but the area of sky is small and may not represent a fair sample. The Combined EIS-NVSS Survey of Radio Sources (CENSORS) survey (Best et al 2003, Brookes et al 2006) matches sources in the ESO Imaging Survey to 150 sources in the NRAO VLA Sky Survey (Condon et al 1998) and is complete to 7.8mJy. Complete spectroscopic data from this survey will provide further information on the nature and redshift distribution of faint radio sources.…”

Section: Introductionmentioning

confidence: 99%

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Identifications of FIRST radio sources in the NOAO Deep Wide‐Field Survey

Bouchefry

Cress

2007

Astron Nachr

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In this paper we present the results of an optical and near infrared identification of 514 radio sources from the FIRST survey (Faint Images of the Radio Sky Survey at Twenty centimetres) with a flux-density limit of 1 mJy in the NOAO Deep-Wide Field Survey (NDWFS) Boötes field. Using optical (Bw, R, I) and K band data with approximate limits of Bw∼ 25.5 mag, R∼25.8 mag, I∼ 25.5 mag and K∼19.4 mag, optical counterparts have been identified for 378 of 514 FIRST radio sources. This corresponds to an identification rate of 34% in four bands (BwRIK), 60% in optical bands (BwRI) and 74% in I band. Photometric redshifts for these sources have been computed using the hyperz code. The inclusion of quasar template spectra in hyperz is investigated. We note that the photometric data are, in many cases, best matched to templates with very short star-formation timescales and the inferred ages of identified galaxies depend strongly on the assumptions about the star-formation timescale. The redshifts obtained are fairly consistent with those expected from the K-z relation for brighter radio sources but there is more scatter in the K-z diagram at z<1.

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“…In the literature, many studies of the USS samples have also used additional selection criteria such as small angular size and faint infrared magnitude to select high-z sources (De Breuck et al 2004;De Breuck et al 2006;Cruz et al 2006). According to the K−z relation, HzRGs are expected to be faint in K-band and indeed, several HzRGs have been discovered by pre-selecting them in K-band (Jarvis et al 2001b;Brookes et al 2006;Jarvis et al 2009). The second highest redshift known radio galaxy identified by Jarvis et al (2009) was selected for follow-up based purely on its faint K-band magnitude, and it is not a USS source (α = −0.75).…”

Section: High-z Radio Sources In Faint Uss Samplementioning

confidence: 99%

Multiwavelength characterization of faint ultra steep spectrum radio sources: A search for high-redshift radio galaxies

Singh

Beelen

Wadadekar

et al. 2014

A&A

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Context. Ultra steep spectrum (USS) radio sources are one of the efficient tracers of powerful high-z radio galaxies (HzRGs). In contrast to searches for powerful HzRGs from radio surveys of moderate depths, fainter USS samples derived from deeper radio surveys can be useful in finding HzRGs at even higher redshifts and in unveiling a population of obscured weaker radio-loud AGN at moderate redshifts. Aims. Using our 325 MHz GMRT observations (5σ ∼ 800 μJy) and 1.4 GHz VLA observations (5σ ∼ 80−100 μJy) available in two subfields (VLA-VIMOS VLT Deep Survey (VLA-VVDS) and Subaru X-ray Deep Field (SXDF)) of the XMM-LSS field, we derive a large sample of 160 faint USS radio sources and characterize their nature. Methods. The optical and IR counterparts of our USS sample sources are searched using existing deep surveys, at respective wavelengths. We attempt to unveil the nature of our faint USS sources using diagnostic techniques based on mid-IR colors, flux ratios of radio to mid-IR, and radio luminosities. Results. Redshift estimates are available for 86/116 (∼74%) USS sources in the VLA-VVDS field and for 39/44 (∼87%) USS sources in the SXDF fields with median values (z median ) ∼1.18 and ∼1.57, respectively, which are higher than estimates for non-USS radio sources (z median non−USS ∼ 0.99 and ∼0.96), in the two subfields. The MIR color-color diagnostic and radio luminosities are consistent with most of our USS sample sources at higher redshifts (z > 0.5) being AGN. The flux ratio of radio to mid-IR (S 1.4 GHz /S 3.6 μm ) versus redshift diagnostic plot suggests that more than half of our USS sample sources distributed over z ∼ 0.5 to 3.8 are likely to be hosted in obscured environments. A significant fraction (∼26% in the VLA-VVDS and ∼13% in the SXDF) of our USS sources without redshift estimates mostly remain unidentified in the existing optical, IR surveys, and exhibit high radio to mid-IR flux ratio limits similar to HzRGs, and so, can be considered as potential HzRG candidates. Conclusions. Our study shows that the criterion of ultra steep spectral index remains a reasonably efficient method to select high-z sources even at sub-mJy flux densities. In addition to powerful HzRG candidates, our faint USS sample also contains populations of weaker radio-loud AGNs potentially hosted in obscured environments.

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CENSORS: A Combined EIS-NVSS Survey of Radio Sources - II. Infrared imaging and the K-z relation

Cited by 29 publications

References 19 publications

Kinematic signatures of AGN feedback in moderately powerful radio galaxies atz~ 2 observed with SINFONI

Kinematic signatures of AGN feedback in moderately powerful radio galaxies atz~ 2 observed with SINFONI

Identifications of FIRST radio sources in the NOAO Deep Wide‐Field Survey

Multiwavelength characterization of faint ultra steep spectrum radio sources: A search for high-redshift radio galaxies

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