Search for Optical Identifications in the 5C3‐Radio Survey II. Statistical Treatment and Results

Richter, G. A.

doi:10.1002/asna.19752960203

Cited by 71 publications

(45 citation statements)

References 10 publications

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“…While there is an obvious reason to expect galaxies that are intrinsically brighter at 24 μm to be, on average, intrinsically brighter in the FIR, there exists no other sufficiently deep dataset in the CFHTLS-D1 field where a similar correlation is expected 10 . In the absence of an astrophysical motivation, we chose to adopt a statistical approach relying on the SWIRE/IRAC photometry and a well-established methodology of matching sources between images of significantly different PSFs (Richter 1975;Sutherland & Sanders 1992). This method, described in detail in Kocevski et al (2009a) and Rumbaugh et al (2012), uses a likelihood radio statistic of the form…”

Section: Herschel Counterpartsmentioning

confidence: 99%

Hidden starbursts and active galactic nuclei at 0 < z < 4 from theHerschel-VVDS-CFHTLS-D1 field: Inferences on coevolution and feedback

Lemaux

Floc’h

Fèvre

et al. 2014

A&A

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We investigate of the properties of ∼2000 Herschel/SPIRE far-infrared-selected galaxies from 0 < z < 4 in the CFHTLS-D1 field. Using a combination of extensive spectroscopy from the VVDS and ORELSE surveys, deep multiwavelength imaging from CFHT, VLA, Spitzer, XMM-Newton, and Herschel, and well-calibrated spectral energy distribution fitting, Herschel-bright galaxies are compared to optically-selected galaxies at a variety of redshifts. Herschel-selected galaxies are observed to span a range of stellar masses, colors, and absolute magnitudes equivalent to galaxies undetected in SPIRE. Though many Herschel galaxies appear to be in transition, such galaxies are largely consistent with normal star-forming galaxies when rest-frame colors are utilized. The nature of the star-forming "main sequence" is studied and we warn against adopting this framework unless the main sequence is determined precisely. Herschel galaxies at different total infrared luminosities (L TIR ) are compared. Bluer optical colors, larger nebular extinctions, and larger contributions from younger stellar populations are observed for galaxies with larger L TIR , suggesting that low-L TIR galaxies are undergoing rejuvenated starbursts while galaxies with higher L TIR are forming a larger percentage of their stellar mass. A variety of methods are used to select powerful active galactic nuclei (AGN). Galaxies hosting all types of AGN are observed to be undergoing starbursts more commonly and vigorously than a matched sample of galaxies without powerful AGN and, additionally, the fraction of galaxies with an AGN increases with increasing star formation rate at all redshifts. At all redshifts (0 < z < 4) the most prodigious star-forming galaxies are found to contain the highest fraction of powerful AGN. For redshift bins that allow a comparison (z > 0.5), the highest L TIR galaxies in a given redshift bin are unobserved by SPIRE at subsequently lower redshifts, a trend linked to downsizing. In conjunction with other results, this evidence is used to argue for prevalent AGN-driven quenching in starburst galaxies across cosmic time.

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Section: Herschel Counterpartsmentioning

confidence: 99%

Hidden starbursts and active galactic nuclei at 0 < z < 4 from theHerschel-VVDS-CFHTLS-D1 field: Inferences on coevolution and feedback

Lemaux

Floc’h

Fèvre

et al. 2014

A&A

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“…We quantify the probability of an i -band optical object being the true host of a given X-ray point-like source by using a modified version of the likelihood ratio method, first described by Richter (1975) and subsequently modified by de Ruiter et al (1977), Prestage & Peacock (1983), Benn (1983), Wolstencroft et al (1986) and Sutherland & Saunders (1992). The Sutherland & Saunders (1992) version of the likelihood ratio technique used here allows us to derive, for each X-ray point-like source, a probability of association with any optical object that potentially takes into account its position offset, magnitude, colour, etc.…”

Section: Optical Identificationmentioning

confidence: 99%

The dependence of X-ray AGN activity on host galaxy properties and environment

Tasse

Röttgering

Best

2010

A&A

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There is mounting evidence that active galactic nuclei (AGN) selected through optical emission lines or radio luminosities comprise two distinct AGN populations, whose activity is triggered by different processes. In two previous papers, we studied the host galaxies and environment of radio-loud AGN. In this third paper we study the properties of a sample of Type-2 AGN that were selected on the basis of their [2-10] keV X-ray luminosity. We find that the X-ray luminosity function is in good agreement with previous studies and that the fraction of galaxies hosting an X-ray AGN is a strong function of the stellar mass of the host galaxy. The shape of this fraction-mass relation is similar to the fraction of galaxies that are emission-line AGN, while it differs significantly from the relation observed for radio-selected AGN. The AGN in our sample tend to be located in underdense environments where galaxy mergers and interactions are likely to occur. For all host galaxy masses, the Type-2 AGN display a strong infrared excess at short (∼3.5 μm) wavelengths, suggesting the presence of hot dust possibly associated with a hot dusty torus. These results add weight to the belief that the X-ray selection criteria identifies a population of AGN similar to the emission-line selected population but distinct from the radio population at high masses.

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“…For the optical identification of these 973 radio sources, we used the likelihood ratio technique, first used in this context by Richter (1975) and in modified form by de Ruiter et al (1977), Prestage & Peacock (1983), Sutherland & Saunders (1992) and Ciliegi et al (2003). The mean off-set between the radio and optical positions estimated in the previous section has been removed from the radio positions to compute the positional offset.…”

Section: Optical Identification Of the Radio Sourcesmentioning

confidence: 99%

The VVDS-VLA deep field

Ciliegi¹,

Zamorani²,

Bondì³

et al. 2005

A&A

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In this paper we present the optical and near-infrared identifications of the 1054 radio sources detected in the 20 cm deep radio survey down to a 5σ flux limit of ∼80 µJy obtained with the VLA in the VIMOS VLT Deep Survey VVDS-02h deep field. Using U, B, V, R, I and K data, with limiting magnitudes of U AB ∼ 25.4, B AB ∼ 26.5, V AB ∼ 26.2, R AB ∼ 25.9 I AB ∼ 25.0, J AB ∼ 24.2, K AB ∼ 23.9 (50% completeness) we identified 718 radio sources (∼74% of the whole sample). The photometric redshift analysis shows that, in each magnitude bin, the radio sample has a higher median photometric redshift than the whole optical sample, while the median (V − I) AB color of the radio sources is redder than the median color of the whole optical sample. These results suggest that radio detection is preferentially selecting galaxies with higher intrinsic optical luminosity. From the analysis of the optical properties of the radio sources as function of the radio flux, we found that while about 35% of the radio sources are optically unidentified in the higher radio flux bin (S > 1.0 mJy), the percentage of unidentified sources decreases to about 25% in the faintest bins (S < 0.5 mJy). The median I AB magnitude for the total sample of radio sources, i.e. including also the unidentified ones, is brighter in the faintest radio bins than in the bin with higher radio flux. This suggests that most of the faintest radio sources are likely to be associated to relatively lower radio luminosity objects at relatively modest redshift, rather than radio-powerful, AGN type objects at high redshift. Using a classification in early-type and late-type galaxies based on the (B − I) AB color and the photometric redshift, we found that the majority of the radio sources below ∼0.15 mJy are indeed late-type star forming galaxies. Finally, the radio sources without optical counterpart in our deep imaging have a median radio flux of 0.15 mJy, equal to that of identified sources. Given the very faint optical limits, these unidentified radio sources probably contain a significant fraction of obscured and/or high redshift galaxies.Key words. cosmology: observations -galaxies: general -galaxies: starburst -radio continuum: galaxies Article published by EDP Sciences and available at http://www.edpsciences.org/aa or http://dx

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Search for Optical Identifications in the 5C3‐Radio Survey II. Statistical Treatment and Results

Cited by 71 publications

References 10 publications

Hidden starbursts and active galactic nuclei at 0 < z < 4 from theHerschel-VVDS-CFHTLS-D1 field: Inferences on coevolution and feedback

Hidden starbursts and active galactic nuclei at 0 < z < 4 from theHerschel-VVDS-CFHTLS-D1 field: Inferences on coevolution and feedback

The dependence of X-ray AGN activity on host galaxy properties and environment

The VVDS-VLA deep field

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