Radio-quiet quasars in the VIDEO survey: evidence for AGN-powered radio emission at S1.4 GHz &lt; 1 mJy

We present a series of results from a clustering analysis of the first data release of the Visible and Infrared Survey Telescope for Astronomy (VISTA) Deep Extragalactic Observations (VIDEO) survey. VIDEO is the only survey currently capable of probing the bulk of stellar mass in galaxies at redshifts corresponding to the peak of star formation on degree scales. Galaxy clustering is measured with the two-point correlation function, which is calculated using a non parametric kernel based density estimator. We use our measurements to investigate the connection between the galaxies and the host dark matter halo using a halo occupation distribution methodology, deriving bias, satellite fractions, and typical host halo masses for stellar masses between 10 9.35 M and 10 10.85 M , at redshifts 0.5 < z < 1.7. Our results show typical halo mass increasing with stellar mass (with moderate scatter) and bias increasing with stellar mass and redshift consistent with previous studies. We find the satellite fraction increased towards low redshifts, from ∼ 5% at z ∼ 1.5, to ∼ 20% at z ∼ 0.6. We combine our results to derive the stellar mass to halo mass ratio for both satellites and centrals over a range of halo masses and find the peak corresponding to the halo mass with maximum star formation efficiency to be ∼ 2×10 12 M , finding no evidence for evolution.

Section: Video and Cfhtlsmentioning

confidence: 99%

Section: Final Samplementioning

confidence: 99%

The galaxy–halo connection in the VIDEO survey at 0.5 <z< 1.7

Hatfield

Lindsay

Jarvis

et al. 2016

“…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%

Radio-faint AGN: a tale of two populations

Padovani

Bonzini

Kellermann

et al. 2015

130

167

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.

“…It is now widely accepted that the inflection in the differential source counts observed at S 1.4 GHz ∼ 1 mJy is due to the emergence of star-forming galaxies and radio-quiet AGN, which begin to contribute significantly to the radio sky below S 1.4 GHz ∼ 1 mJy (e.g. Jarvis & Rawlings 2004;Seymour et al 2008;Smolčić et al 2008;Padovani et al 2009;White et al 2015). An in-depth review of radio source counts and their implications is given by de Zotti et al (2010).…”

Section: Introductionmentioning

confidence: 99%

GMRT 610-MHz observations of the faint radio source population – and what these tell us about the higher radio-frequency sky

Whittam

Green

Jarvis

et al. 2016

We present 610-MHz Giant Metrewave Radio Telescope observations of 0.84 deg 2 of the AMI001 field (centred on 00 h 23 m 10 s , +31• 53 ) with an r.m.s. noise of 18 µJy beam −1 in the centre of the field. 955 sources are detected, and 814 are included in the source count analysis. The source counts from these observations are consistent with previous work. We have used these data to study the spectral index distribution of a sample of sources selected at 15.7 GHz from the recent deep extension to the Tenth Cambridge (10C) survey. The median spectral index, α, (where S ∝ ν −α ) between 0.08 < S 15.7 GHz /mJy < 0.2 is 0.32 ± 0.14, showing that star-forming galaxies, which have much steeper spectra, are not contributing significantly to this population. This is in contrast to several models, but in agreement with the results from the 10C ultra-deep source counts; the high-frequency sky therefore continues to be dominated by radio galaxies down to S 15.7 GHz = 0.1 mJy.