THE VERY LARGE ARRAY SURVEY OF THE<i>CHANDRA</i>DEEP FIELD SOUTH. IV. SOURCE POPULATION

Padovani, P.; Mainieri, V.; Tozzi, P.; Kellermann, K. I.; Fomalont, Edward B.; Miller, Neal A.; Rosati, P.; Shaver, P. A.

doi:10.1088/0004-637x/694/1/235

Cited by 114 publications

(174 citation statements)

References 55 publications

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“…More details on this and other 2 A preliminary version of this figure has been shown by Padovani et al (2014). 3 Due to a small numerical error, the number counts in Kellermann et al (2008) and, consequently, also those in Padovani et al (2009) and Padovani et al (2011), were too high by ∼ 5%. statistical techniques used in this paper can be found in Padovani et al (2011).…”

Section: Ve/va Analysismentioning

confidence: 99%

“…6.2). Furthermore, as discussed by Padovani et al (2009) and Padovani (2011), R is useful for quasar samples, where it is related to the jet/disk ratio, but loses its meaning for radio galaxies.…”

Section: The Intrinsic Fraction Of Radiative-mode Rl Agnmentioning

confidence: 99%

“…This has been possible only recently (e.g. Padovani et al 2009Padovani et al , 2011Simpson et al 2012;White et al 2015, and references therein).…”

Section: Introductionmentioning

confidence: 99%

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Radio-faint AGN: a tale of two populations

Padovani

Bonzini

Kellermann

et al. 2015

Mon. Not. R. Astron. Soc.

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We study the Extended Chandra Deep Field South (E-CDFS) Very Large Array sample, which reaches a flux density limit at 1.4 GHz of 32.5 µJy at the field centre and redshift ∼ 4, and covers ∼ 0.3 deg 2 . Number counts are presented for the whole sample while the evolutionary properties and luminosity functions are derived for active galactic nuclei (AGN). The faint radio sky contains two totally distinct AGN populations, characterised by very different evolutions, luminosity functions, and Eddington ratios: radio-quiet (RQ)/radiative-mode, and radioloud/jet-mode AGN. The radio power of RQ AGN evolves ∼ ∝ (1 + z) 2.5 , similarly to star-forming galaxies, while the number density of radio-loud ones has a peak at z ∼ 0.5 and then declines at higher redshifts. The number density of radioselected RQ AGN is consistent with that of X-ray selected AGN, which shows that we are sampling the same population. The unbiased fraction of radiativemode RL AGN, derived from our own and previously published data, is a strong function of radio power, decreasing from ∼ 0.5 at P 1.4GHz ∼ 10 24 W Hz −1 to ∼ 0.04 at P 1.4GHz ∼ 10 22 W Hz −1 . Thanks to our enlarged sample, which now includes ∼ 700 radio sources, we also confirm and strengthen our previous results on the source population of the faint radio sky: star-forming galaxies start to dominate the radio sky only below ∼ 0.1 mJy, which is also where radio-quiet AGN overtake radio-loud ones.

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Section: Ve/va Analysismentioning

confidence: 99%

Section: The Intrinsic Fraction Of Radiative-mode Rl Agnmentioning

confidence: 99%

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Radio-faint AGN: a tale of two populations

Padovani

Bonzini

Kellermann

et al. 2015

Mon. Not. R. Astron. Soc.

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128

167

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“…Hopkins et al 1998). However, a growing number of studies are finding that lower luminosity AGN, both radio-loud and weakly radio emitting sources (radio-loud and radio-quiet AGN respectively), make a significant contribution to the sub-mJy population (Jarvis & Rawlings 2004;Huynh et al 2008;Seymour et al 2008;Smolčić et al 2008;Padovani et al 2009Padovani et al , 2011Bonzini et al 2013).…”

Section: Introductionmentioning

confidence: 99%

The ATLAS 5.5 GHz survey of the extendedChandraDeep Field South: the second data release

Huynh¹,

Bell²,

Hopkins³

et al. 2015

Mon. Not. R. Astron. Soc.

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We present a new image of the 5.5 GHz radio emission from the extended Chandra Deep Field South. Deep radio observations at 5.5 GHz were obtained in 2010 and presented in the first data release. A further 76 hours of integration has since been obtained, nearly doubling the integration time. This paper presents a new analysis of all the data. The new image reaches 8.6 µJy rms, an improvement of about 40% in sensitivity. We present a new catalogue of 5.5 GHz sources, identifying 212 source components, roughly 50% more than were detected in the first data release. Source counts derived from this sample are consistent with those reported in the literature for S 5.5GHz > 0.1 mJy but significantly lower than published values in the lowest flux density bins (S 5.5GHz < 0.1 mJy), where we have more detected sources and improved statistical reliability. The 5.5 GHz radio sources were matched to 1.4 GHz sources in the literature and we find a mean spectral index of −0.35 ± 0.10 for S 5.5GHz > 0.5 mJy, consistent with the flattening of the spectral index observed in 5 GHz sub-mJy samples. The median spectral index of the whole sample is α med = −0.58, indicating that these observations may be starting to probe the star forming population. However, even at the faintest levels (0.05 < S 5.5GHz < 0.1 mJy), 39% of the 5.5 GHz sources have flat or inverted radio spectra. Four flux density measurements from our data, across the full 4.5 to 6.5 GHz bandwidth, are combined with those from literature and we find 10% of sources (S 5.5GHz 0.1 mJy) show significant curvature in their radio spectral energy distribution spanning 1.4 to 9 GHz.

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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). This means that an accurate screening is needed also for radio-selected faint galaxies.…”

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 VERY LARGE ARRAY SURVEY OF THECHANDRADEEP FIELD SOUTH. IV. SOURCE POPULATION

Cited by 114 publications

References 55 publications

Radio-faint AGN: a tale of two populations

Radio-faint AGN: a tale of two populations

The ATLAS 5.5 GHz survey of the extendedChandraDeep Field South: the second data release

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

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