Sub-millijansky 1.4 GHz source counts and multicolor studies of weak radio galaxy populations

Windhorst, Rogier A.; Miley, G. K.; Owen, F. N.; Krön, Richard G.; Koo, David C.

doi:10.1086/162911

Cited by 208 publications

(211 citation statements)

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“…We therefore weight each source by the inverse of the area in which it can be detected (e.g. Windhorst et al 1985), which also accounts for the varying detection area within a given flux density bin. Accurate derivation of the source counts is complicated by a number of effects.…”

Section: Source Countsmentioning

confidence: 99%

T-RaMiSu: the Two-meter Radio Mini Survey

Williams

Intema

Röttgering

2012

A&A

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We present wide area, deep, high-resolution 153 MHz GMRT observations of the NOAO Boötes field, adding to the extensive, multiwavelength data of this region. The observations, data reduction, and catalogue construction and description are described here. The seven pointings produced a final mosaic covering 30 square degrees with a resolution of 25 . The rms noise is 2 mJy beam −1 in the centre of the image, rising to 4-5 mJy beam −1 on the edges, with an average of 3 mJy beam −1 . Seventy-five per cent of the area has an rms < 4 mJy beam −1 . The extracted source catalogue contains 1289 sources detected at 5σ, of which 453 are resolved. We estimate the catalogue to be 92 per cent reliable and 95 per cent complete at an integrated flux density limit of 14 mJy. The flux densities and astrometry have been corrected for systematic errors. We calculate the differential source counts, which are in good agreement with those in the literature and provide an important step forward in quantifying the source counts at these low frequencies and low flux densities. The GMRT 153 MHz sources have been matched to the 1.4 GHz NVSS and 327 MHz WENSS catalogues and spectral indices were derived.

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Section: Source Countsmentioning

confidence: 99%

T-RaMiSu: the Two-meter Radio Mini Survey

Williams

Intema

Röttgering

2012

A&A

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“…It has been known since long that a population of faint radio sources associated with faint blue galaxies was emerging at radio fluxes below ∼1 mJy (Windhorst et al 1985;Fomalont et al 1991;Richards et al 1998;Richards 2000). In recent years, it has been shown that a sizable fraction (about 50%) of this sub-mJy population is actually made up of AGN (Gruppioni et al 1999;Ciliegi et al 2003;Seymour et al 2008;Smolčić et al 2008;Padovani et al 2009;Strazzullo et al 2010).…”

Section: Introductionmentioning

confidence: 99%

X-ray properties of radio-selected star forming galaxies in theChandra-COSMOS survey

Ranalli

Comastri

Zamorani

et al. 2012

A&A

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X-ray surveys contain sizable numbers of star forming galaxies, beyond the AGN which usually make the majority of detections. Many methods to separate the two populations are used in the literature, based on X-ray and multiwavelength properties. We aim at a detailed test of the classification schemes and to study the X-ray properties of the resulting samples. We build on a sample of galaxies selected at 1.4 GHz in the VLA-COSMOS survey, classified by Smolčić et al. (2008, ApJS, 177, 14) according to their optical colours and observed with Chandra. A similarly selected control sample of AGN is also used for comparison. We review some X-ray based classification criteria and check how they affect the sample composition. The efficiency of the classification scheme devised by Smolčić et al. is such that ∼30% of composite/misclassified objects are expected because of the higher X-ray brightness of AGN with respect to galaxies. The latter fraction is actually 50% in the X-ray detected sources, while it is expected to be much lower among X-ray undetected sources. Indeed, the analysis of the stacked spectrum of undetected sources shows, consistently, strongly different properties between the AGN and galaxy samples. X-ray based selection criteria are then used to refine both samples. The radio/X-ray luminosity correlation for star forming galaxies is found to hold with the same X-ray/radio ratio valid for nearby galaxies. Some evolution of the ratio may be possible for sources at high redshift or high luminosity, tough it is likely explained by a bias arising from the radio selection. Finally, we discuss the X-ray number counts of star forming galaxies from the VLA-and C-COSMOS surveys according to different selection criteria, and compare them to the similar determination from the Chandra deep fields. The classification scheme proposed here may find application in future works and surveys.

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“…The source counts above 10 mJy are dominated by giant radio galaxies and QSOs (powered by accretion onto black holes, commonly joined together in the literature under the generic term AGN). Radio loud sources dominate the source counts down to levels of ∼1 mJy, however, at the sub-mJy level the normalised source counts flatten as a new population of faint radio sources emerge (Windhorst et al 1985). The dominance of starburst galaxies in the sub-mJy population is already well established (Gruppioni et al 2008), where the number of blue galaxies with star-forming spectral signatures is seen to increase strongly.…”

Section: Differential Countsmentioning

confidence: 95%

A deep survey of the AKARI north ecliptic pole field

White

Pearson

Braun

et al. 2010

A&A

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Aims. The Westerbork Radio Synthesis Telescope, WSRT, has been used to make a deep radio survey of an ∼1.7 degree 2 field coinciding with the AKARI north ecliptic pole deep field. The observations, data reduction and source count analysis are presented, along with a description of the overall scientific objectives. Methods. The survey consisted of 10 pointings, mosaiced with enough overlap to maintain a similar sensitivity across the central region that reached as low as 21 μJy beam −1 at 1.4 GHz. Results. A catalogue containing 462 sources detected with a resolution of 17.0 × 15.5 is presented. The differential source counts calculated from the WSRT data have been compared with those from the shallow VLA − NEP survey of Kollgaard et al. 1994, and show a pronounced excess for sources fainter than ∼1 mJy, consistent with the presence of a population of star forming galaxies at sub-mJy flux levels. Conclusions. The AKARI north ecliptic pole deep field is the focus of a major observing campaign conducted across the entire spectral region. The combination of these data sets, along with the deep nature of the radio observations will allow unique studies of a large range of topics including the redshift evolution of the luminosity function of radio sources, the clustering environment of radio galaxies, the nature of obscured radio-loud active galactic nuclei, and the radio/far-infrared correlation for distant galaxies. This catalogue provides the basic data set for a future series of paper dealing with source identifications, morphologies, and the associated properties of the identified radio sources.

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Sub-millijansky 1.4 GHz source counts and multicolor studies of weak radio galaxy populations

Cited by 208 publications

References 0 publications

T-RaMiSu: the Two-meter Radio Mini Survey

T-RaMiSu: the Two-meter Radio Mini Survey

X-ray properties of radio-selected star forming galaxies in theChandra-COSMOS survey

A deep survey of the AKARI north ecliptic pole field

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