The Deep X‐Ray Radio Blazar Survey. III. Radio Number Counts, Evolutionary Properties, and Luminosity Function of Blazars

Padovani, P.; Giommi, P.; Landt, Hermine; Perlman, Eric S.

doi:10.1086/516815

Cited by 113 publications

(199 citation statements)

References 60 publications

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“…The mean redshift is calculated taking into account the effect of the sky coverage, that is each object is weighted by the inverse of the area accessible at the flux density of the source (e.g. Padovani et al 2007). …”

Section: Ve/va Analysismentioning

confidence: 99%

Radio-faint AGN: a tale of two populations

Padovani

Bonzini

Kellermann

et al. 2015

Mon. Not. R. Astron. Soc.

128

167

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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%

Radio-faint AGN: a tale of two populations

Padovani

Bonzini

Kellermann

et al. 2015

Mon. Not. R. Astron. Soc.

128

167

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“…Giommi et al 1999;Padovani et al 2007). Studies performed by Massaro et al (2011b) andD'Abrusco et al (2012), based on data from the Wide-field Infrared Survey Explorer (WISE, Wright et al 2010), have shown that blazars tend to concentrate in a distinct region of the IR colour-colour diagram, known as the WISE blazar strip.…”

Section: Building a Large Sample Of Hsp Blazarsmentioning

confidence: 99%

1WHSP: An IR-based sample of ~1000 VHEγ-ray blazar candidates

Arsioli

Fraga

Giommi

et al. 2015

A&A

103

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Context. Blazars are the dominant type of extragalactic sources at microwave and at γ-ray energies. In the most energetic part of the electromagnetic spectrum (E > ∼ 100 GeV) a high fraction of high Galactic latitude sources are blazars of the high synchrotron peaked (HSP) type, that is BL Lac objects with synchrotron power peaking in the UV or in the X-ray band. Building new large samples of HSP blazars is key to understand the properties of jets under extreme conditions, and to study the demographics and the peculiar cosmological evolution of these sources. Aims. High synchrotron peaked blazars are remarkably rare, with only a few hundreds of them expected to be above the sensitivity limits of currently available surveys, some of which include hundreds of millions of sources. To find these very uncommon objects, we have devised a method that combines ALLWISE survey data with multi-frequency selection criteria. Methods. The sample was defined starting from a primary list of infrared colour-colour selected sources from the ALLWISE all sky survey database, and applying further restrictions on IR-radio and IR-X-ray flux ratios. Using a polynomial fit to the multi-frequency data (radio to X-ray), we estimated synchrotron peak frequencies and fluxes of each object. Results. We assembled a sample including 992 sources, which is currently the largest existing list of confirmed and candidates HSP blazars. All objects are expected to radiate up to the highest γ-ray photon energies. In fact, 299 of these are confirmed emitters of GeV γ-ray photons (based on Fermi-LAT catalogues), and 36 have already been detected in the TeV band. The majority of sources in the sample are within reach of the upcoming Cherenkov Telescope Array (CTA), and many may be detectable even by the current generation of Cherenkov telescopes during flaring episodes. The sample includes 425 previously known blazars, 151 new identifications, and 416 HSP candidates (mostly faint sources) for which no optical spectra is available yet. The full 1WHSP catalogue is online at http://www.asdc.asi.it/1whsp/, providing a direct link to the SED building tool where multi-frequency data for each source can be easily visualised.

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“…For this elusive class of objects the adopted selection criteria can affect the redshift distributions of the BL Lac objects and cause different cosmological evolution scenarios (see, e.g., the discussions in Bade et al 1998 andGiommi et al 2012). Radioselected BL Lac objects seem to display a positive evolution (i.e., either the number density or the luminosity shows a decrease with cosmic time), while a negative evolution or no evolution at all was proposed for X-ray-selected objects (Rector et al 2000;Rector & Stocke 2001;Caccianiga et al 2002;Beckmann et al 2003;Padovani et al 2007;Ajello et al 2009;Giommi et al 2009Giommi et al , 2012, and references therein). A continuum trend from slightly positive-evolution low-peaked BL Lac objects to strong negative-evolution high-peaked BL Lac objects was proposed (Rector et al 2000), and was thought to be related to the X-ray to radio flux ratio (Giommi et al 1999(Giommi et al , 2012.…”

Section: Introductionmentioning

confidence: 99%

SPECTROSCOPY OF OPTICALLY SELECTED BL LAC OBJECTS AND THEIR Γ-Ray EMISSION

Sandrinelli

Treves

Falomo

et al. 2013

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We present Very Large Telescope optical spectroscopy of nine BL Lac objects of unknown redshift belonging to the list of optically selected radio-loud BL Lac candidates. We explore their spectroscopic properties and possible link with gamma-ray emission. From the new observations we determine the redshifts of four objects from faint emission lines or from absorption features of their host galaxies. In three cases we find narrow intervening absorptions from which a lower limit to the redshift is inferred. For the remaining two featureless sources, lower limits to the redshift are deduced from the absence of spectral lines. A search for γ counterpart emission shows that six out of the nine candidates are Fermi γ -ray emitters and we find two new detections. Our analysis suggests that most of the BL Lac objects still lacking redshift information are most likely located at high redshifts.

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The Deep X‐Ray Radio Blazar Survey. III. Radio Number Counts, Evolutionary Properties, and Luminosity Function of Blazars

Cited by 113 publications

References 60 publications

Radio-faint AGN: a tale of two populations

Radio-faint AGN: a tale of two populations

1WHSP: An IR-based sample of ~1000 VHEγ-ray blazar candidates

SPECTROSCOPY OF OPTICALLY SELECTED BL LAC OBJECTS AND THEIR Γ-Ray EMISSION

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