Star formation properties of sub-mJy radio sources

Bonzini, M.; Mainieri, V.; Padovani, P.; Andreani, P.; Berta, S.; Béthermin, M.; Lutz, D.; Rodighiero, G.; Rosario, D. J.; Tozzi, P.; Vattakunnel, S.

doi:10.1093/mnras/stv1675

Cited by 72 publications

(93 citation statements)

References 90 publications

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“…On the other hand, radio emission in our sample of MLAGN is predominantly arising from non-thermal radiation likely ascribed to AGN activity, rather than star formation in their hosts. These results agree with the conclusions presented by Padovani et al (2015) and Bonzini et al (2015) for a sample of RQ-AGN and RL-AGN, supporting the composite nature of the sub-mJy radio source population (e.g. Smolčić et al 2008;Padovani et al 2011;Baldi et al 2014).…”

Section: Radio Emission In Hlagn and Mlagnsupporting

confidence: 90%

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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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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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Section: Radio Emission In Hlagn and Mlagnsupporting

confidence: 90%

“…For example, Bonzini et al (2015) and Padovani et al (2015) investigated the origin of radio emission in RQ and RL AGN in the E-CDFS down to 37 µJy (5σ). They found a mixture of AGN and SFGs contributing to the sub-mJy radio population, where RQ AGN is predominantly powered by star formation.…”

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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“…Recently, Bonzini et al (2015) revisited the FIR SFR estimates of the ECDFS sample using the Herschel PACS data. This allowed them to obtain more reliable estimates of the source radio excess than those that were based on the q 24 parameter alone .…”

Section: Discussionmentioning

confidence: 99%

“…For RQ851 and RQ76, 5 GHz information is lacking, and we adopted the value of −0.75 (e.g., Kukula et al 1998 may indicate that compact radio cores are a common component of RQ AGNs, at least for those lying below the radio/FIR correlation. Bonzini et al (2015) discussed the larger dispersion of RQ AGNs around the radio/FIR correlation with respect to the dispersion of SFGs and hypothesised that it might be due to contamination by AGN emission. Here we provide direct evidence that this is the case.…”

Section: Discussionmentioning

confidence: 99%

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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“…The presence of emission from stronger sources within a few arcmin does not allow us to fully discard the possibility of a small spurios contamination, at least for SDP.9. The conversion of the SFR, as estimated form the Herschel maps, into radio signal at this frequency using the Bonzini et al (2015) relation after scaling for the magnification fac-1 http://sundog.stsci.edu/index.html 3. Chandra X-ray observations SDP.9 and SDP.11 were observed by Chandra in Cycle 16, with the ACIS-S3 CCD at the aimpoint, for a total exposure time of 55.3 ks (on January 10 th , 2015) and 19.8 ks (on February 28 th and March 23 rd , 2015), respectively.…”

Section: Introductionmentioning

confidence: 99%

Chandra and ALMA observations of the nuclear activity in two strongly lensed star-forming galaxies

Massardi

Enia

Negrello

et al. 2018

A&A

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Aims. According to coevolutionary scenarios, nuclear activity and star formation play relevant roles in the early stages of galaxy formation. We aim at identifying them in high redshift galaxies by exploiting high-resolution and sensitivity X-ray and millimetre-wavelength data to confirm the presence or absence of star formation and nuclear activity and their relative role in shaping their SEDs and contributing to their energy budget. Methods. In the current paper we present the data, model and analysis in the X-ray and mm bands for two strongly lensed galaxies, SDP.9 (HATLAS J090740.0-004200) and SDP.11 (HATLAS J091043.1-000322) that we selected in the Herschel-ATLAS catalogues as having an excess emission in the mid-IR regime at redshift > ∼ 1.5, suggesting the presence of a nuclear activity in the early stages of galaxy formation. We observed both of them with Chandra ACIS-S in the X-ray regime and analyzed the high resolution mm data available in the ALMA Science Archive for SDP9, and, by combining the information available in mm, optical and X-ray bands we reconstructed the source morphology.Results. Both the targets were detected in the X-ray, strongly indicating the presence of highly obscured nuclear activity. ALMA observations for SDP9 for continuum and CO(6-5) spectral line with high resolution (0.02arcsec corresponding to ∼ 65 pc at galaxy distance) allowed us to estimate the lensed galaxy redshift to a better accuracy than pre-ALMA estimates (1.5753±0.0003) and to model the emission of the optical, millimetric, and X-ray band emission for this galaxy. We demonstrated that the X-ray emission is generated in the nuclear environment and it strongly support the presence of nuclear activity in this object. On the basis of the X-ray data, we attempted an estimate of the BH properties in these galaxies. Conclusions. By taking advantage of the lensing magnification we identified weak nuclear activity associated with high-z galaxies with large star formation rates, useful to extend the investigation of the relationship between star formation and nuclear activity to two intrinsically less luminous, high-z star forming galaxies than was possible so far. Given our results only for two objects, they solely cannot constrain the evolutionary models, but provide us with interesting hints and set an observational path towards addressing the role of star formation and nuclear activity in forming galaxies.

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Star formation properties of sub-mJy radio sources

Cited by 72 publications

References 90 publications

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

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

Compact radio cores in radio-quiet active galactic nuclei

Chandra and ALMA observations of the nuclear activity in two strongly lensed star-forming galaxies

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