Resolving the Radio Source Background: Deeper Understanding Through Confusion

Condon, J. J.; Cotton, W. D.; Fomalont, Edward B.; Kellermann, K. I.; Miller, Neal A.; Perley, R. A.; Scott, D.; Vernstrom, Tessa; Wall, J. V.

doi:10.1088/0004-637x/758/1/23

Cited by 246 publications

(382 citation statements)

References 54 publications

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“…Published deep radio source counts are widely discrepant, even when made with the same instrument, and even with different investigators using the same instrument in the same field (Condon et al 2012). Since source detection depends on the peak flux density, the effects of resolution cause two problems.…”

Section: The Sub-mjy Number Countsmentioning

confidence: 99%

Radio-faint AGN: a tale of two populations

Padovani

Bonzini

Kellermann

et al. 2015

Mon. Not. R. Astron. Soc.

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127

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: The Sub-mjy Number Countsmentioning

confidence: 99%

Radio-faint AGN: a tale of two populations

Padovani

Bonzini

Kellermann

et al. 2015

Mon. Not. R. Astron. Soc.

Self Cite

127

167

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“…Finally, the mosaics produced from each sub-band can be recombined with appropriate weights to obtain a sensitive wide-band mosaic (e.g. Condon et al 2012). …”

Section: Imaging and Mosaicingmentioning

confidence: 99%

“…Several works suggest that star-formation related processes can, at least partly, produce the observed radio emission in RE-AGN (e.g. Kimball et al 2011;Padovani et al 2011;Condon et al 2012;Bonzini et al 2013). Others point towards composite star-formation and AGN emission (e.g.…”

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confidence: 99%

The eMERGE Survey – I: Very Large Array 5.5 GHz observations of the GOODS-North Field

Guidetti

Bondì

Prandoni

et al. 2017

Monthly Notices of the Royal Astronomical Society

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We present new observations of the GOODS-N field obtained at 5.5 GHz with the Karl G. Jansky Very Large Array (VLA). The central region of the field was imaged to a median r.m.s. of 3 µJy beam −1 with a resolution of 0.5 arcsec. From a 14-arcmin diameter region we extracted a sample of 94 radio sources with signal-to-noise ratio greater than 5. Near-IR identifications are available for about ∼88 percent of the radio sources. We used different multi-band diagnostics to separate active galactic nuclei (AGN), both radiatively efficient and inefficient, from star-forming galaxies. From our analysis, we find that about 80 percent of our radio-selected sample is AGNdominated, with the fraction raising to 92 percent when considering only the radio sources with redshift > 1.5. This large fraction of AGN-dominated radio sources at very low flux densities (the median flux density at 5.5 GHz is 42 µJy), where star-forming galaxies are expected to dominate, is somewhat surprising and at odds with other results. Our interpretation is that both the frequency and angular resolution of our radio observations strongly select against radio sources whose brightness distribution is diffuse on scale of several kpc. Indeed, we find that the median angular sizes of the AGN-dominated sources is around 0.2-0.3 arcsec against 0.8 arcsec for star-forming galaxies. This highlights the key role that high frequency radio observations can play in pinpointing AGN-driven radio emission at µJy levels. This work is part of the eMERGE legacy project.

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“…The second estimate is from Condon et al (2012), who used deep VLA C-configuration observations at S -band (2−4 GHz) to derive…”

Section: Setup Of Msss-lbamentioning

confidence: 99%

The LOFAR Multifrequency Snapshot Sky Survey (MSSS)

Heald

Pizzo

Orrù

et al. 2015

A&A

104

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We present the Multifrequency Snapshot Sky Survey (MSSS), the first northern-sky Low Frequency Array (LOFAR) imaging survey. In this introductory paper, we first describe in detail the motivation and design of the survey. Compared to previous radio surveys, MSSS is exceptional due to its intrinsic multifrequency nature providing information about the spectral properties of the detected sources over more than two octaves (from 30 to 160 MHz). The broadband frequency coverage, together with the fast survey speed generated by LOFAR's multibeaming capabilities, make MSSS the first survey of the sort anticipated to be carried out with the forthcoming Square Kilometre Array (SKA). Two of the sixteen frequency bands included in the survey were chosen to exactly overlap the frequency coverage of large-area Very Large Array (VLA) and Giant Metrewave Radio Telescope (GMRT) surveys at 74 MHz and 151 MHz respectively. The survey performance is illustrated within the MSSS Verification Field (MVF), a region of 100 square degrees centered at (α, δ) J2000 = (15 h , 69 • ). The MSSS results from the MVF are compared with previous radio survey catalogs. We assess the flux and astrometric uncertainties in the catalog, as well as the completeness and reliability considering our source finding strategy. We determine the 90% completeness levels within the MVF to be 100 mJy at 135 MHz with 108 resolution, and 550 mJy at 50 MHz with 166 resolution. Images and catalogs for the full survey, expected to contain 150 000-200 000 sources, will be released to a public web server. We outline the plans for the ongoing production of the final survey products, and the ultimate public release of images and source catalogs.

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Resolving the Radio Source Background: Deeper Understanding Through Confusion

Cited by 246 publications

References 54 publications

Radio-faint AGN: a tale of two populations

Radio-faint AGN: a tale of two populations

The eMERGE Survey – I: Very Large Array 5.5 GHz observations of the GOODS-North Field

The LOFAR Multifrequency Snapshot Sky Survey (MSSS)

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