Unveiling the origin of the radio emission in radio-quiet quasars

Ruiz, N. Herrera; Middelberg, E.; Norris, R. P.; Maini, Alessandro

doi:10.1051/0004-6361/201628302

Cited by 56 publications

(54 citation statements)

References 39 publications

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“…Such cores can account for a significant fraction of the total radio emission (up to ∼70% in RQ76). Although limited in a statistical sense, our findings are supported by similar results by Herrera Ruiz et al (2016), who found VLBI cores in RQ QSOs in the COSMOS field. Further support comes from the 12 RQQ sources (according to the classification of Bonzini et al 2013) observed by Chi et al (2013), four of which were detected with VLBI.…”

Section: Discussionsupporting

confidence: 91%

Compact radio cores in radio-quiet active galactic nuclei

Maini

Prandoni

Norris

et al. 2016

A&A

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Context. The mechanism of radio emission in radio-quiet (RQ) active galactic nuclei (AGNs) is still debated and might arise from the central AGN, from star formation activity in the host, or from either of these sources. A direct detection of compact and bright radio cores embedded in sources that are classified as RQ can unambiguously determine whether a central AGN significantly contributes to the radio emission. Aims. We search for compact, high-surface-brightness radio cores in RQ AGNs that are caused unambiguously by AGN activity. Methods. We used the Australian Long Baseline Array to search for compact radio cores in four RQ AGNs located in the Extended Chandra Deep Field South (ECDFS). We also targeted four radio-loud (RL) AGNs as a control sample. Results. We detected compact and bright radio cores in two AGNs that are classified as RQ and in one that is classified as RL. Two RL AGNs were not imaged because the quality of the observations was too poor. Conclusions. We report on a first direct evidence of radio cores in RQ AGNs at cosmological redshifts. Our detections show that some of the sources that are classified as RQ contain an active AGN that can contribute significantly (∼50% or more) to the total radio emission.

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Section: Discussionsupporting

confidence: 91%

Compact radio cores in radio-quiet active galactic nuclei

Maini

Prandoni

Norris

et al. 2016

A&A

Self Cite

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“…Recent studies based on interferometric radio observations of sub-mJy radio sources have the potential to shed light on this issue. For example, Herrera Ruiz et al (2016) analysed in detail the interferometric images of three RQ-AGN obtained with VLBI in the COSMOS field, which are part of the sample described in Sect. 4.3.1.…”

Section: Radio Emission In Hlagn and Mlagnmentioning

confidence: 99%

The VLA-COSMOS 3 GHz Large Project: AGN and host-galaxy properties out toz ≲ 6

Delvecchio

Smolčić

Zamorani

et al. 2017

A&A

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150

138

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We explore the multiwavelength properties of AGN host galaxies for different classes of radio-selected AGN out to z 6 via a multiwavelength analysis of about 7 700 radio sources in the COSMOS field. The sources were selected with the Very Large Array (VLA) at 3 GHz (10 cm) within the VLA-COSMOS 3 GHz Large Project, and cross-matched with multiwavelength ancillary data. This is the largest sample of highredshift (z 6) radio sources with exquisite photometric coverage and redshift measurements available. We constructed a sample of moderate-tohigh radiative luminosity AGN (HLAGN) via spectral energy distribution (SED) decomposition combined with standard X-ray and mid-infrared diagnostics. Within the remainder of the sample we further identified low-to-moderate radiative luminosity AGN (MLAGN) via excess in radio emission relative to the star formation rates in their host galaxies. We show that at each redshift our HLAGN have systematically higher radiative luminosities than MLAGN and that their AGN power occurs predominantly in radiative form, while MLAGN display a substantial mechanical AGN luminosity component. We found significant differences in the host properties of the two AGN classes, as a function of redshift. At z<1.5, MLAGN appear to reside in significantly more massive and less star-forming galaxies compared to HLAGN. At z>1.5, we observed a reversal in the behaviour of the stellar mass distributions with the HLAGN populating the higher stellar mass tail. We interpret this finding as a possible hint of the downsizing of galaxies hosting HLAGN, with the most massive galaxies triggering AGN activity earlier than less massive galaxies, and then fading to MLAGN at lower redshifts. Our conclusion is that HLAGN and MLAGN samples trace two distinct galaxy and AGN populations in a wide range of redshifts, possibly resembling the radio AGN types often referred to as radiative-and jet-mode (or high-and low-excitation), respectively, whose properties might depend on the different availability of cold gas supplies.

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“…High-resolution (milli-arcsec) radio observations by Jackson et al (2015), Maini et al (2016) and Herrera-Ruiz et al (2016) have revealed that RQ AGNs can contain nuclear radio cores significantly contributing to the total radio emission. On a larger statistical ground, deep sub-arcsec resolution radio observations of the GOODS-N field have revealed that RQ AGNs are preferentially associated to more compact radio emission than starforming galaxies (Guidetti et al 2017).…”

Section: Introductionmentioning

confidence: 99%

Galaxy Evolution in the Radio Band: The Role of Star-forming Galaxies and Active Galactic Nuclei

Mancuso

Lapi

Prandoni

et al. 2017

ApJ

105

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We investigate the astrophysics of radio-emitting star-forming galaxies and active galactic nuclei (AGNs), and elucidate their statistical properties in the radio band including luminosity functions, redshift distributions, and number counts at sub-mJy flux levels, that will be crucially probed by next-generation radio continuum surveys. Specifically, we exploit the model-independent approach by Mancuso et al. (2016a,b) to compute the star formation rate functions, the AGN duty cycles and the conditional probability of a star-forming galaxy to host an AGN with given bolometric luminosity. Coupling these ingredients with the radio emission properties associated to star formation and nuclear activity, we compute relevant statistics at different radio frequencies, and disentangle the relative contribution of star-forming galaxies and AGNs in different radio luminosity, radio flux, and redshift ranges. Finally, we highlight that radio-emitting star-forming galaxies and AGNs are expected to host supermassive black holes accreting with different Eddington ratio distributions, and to occupy different loci in the galaxy main sequence diagrams. These specific predictions are consistent with current datasets, but need to be tested with larger statistics via future radio data with multi-band coverage on wide areas, as it will become routinely achievable with the advent of the SKA and its precursors.

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Unveiling the origin of the radio emission in radio-quiet quasars

Cited by 56 publications

References 39 publications

Compact radio cores in radio-quiet active galactic nuclei

Compact radio cores in radio-quiet active galactic nuclei

The VLA-COSMOS 3 GHz Large Project: AGN and host-galaxy properties out toz ≲ 6

Galaxy Evolution in the Radio Band: The Role of Star-forming Galaxies and Active Galactic Nuclei

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