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GOODS-Herschel: radio-excess signature of hidden AGN activity in distant star-forming galaxies

journal contribution
posted on 2023-06-08, 17:22 authored by A. Del Moro, D M Alexander, J R Mullaney, E Daddi, M Pannella, F E Bauer, A Pope, M Dickinson, D Elbaz, P D Barthel, M A Garrett, W N Brandt, V Charmandaris, R R Chary, K Dasyra, R Gilli, R C Hickox, H S Hwang, R J Ivison, S Juneau, E Le Floc'h, B Luo, G E Morrison, E Rovilos, Mark Sargent, Y Q Xue
We present here a new spectral energy distribution (SED) fitting approach that we adopt to select radio-excess sources amongst distant star-forming galaxies in the GOODS-Herschel (North) field and to reveal the presence of hidden, highly obscured AGN. Through extensive SED analysis of 458 galaxies with radio 1.4 GHz and mid-IR 24 um detections using some of the deepest Chandra X-ray, Spitzer and Herschel infrared, and VLA radio data available to date, we have robustly identified a sample of 51 radio-excess AGN (~1300 deg^-2) out to redshift z~3. These radio-excess AGN have a significantly lower far-IR/radio ratio (q<1.68) than the typical relation observed for star-forming galaxies (q~2.2). We find that ~45% of these radio-excess sources have a dominant AGN component in the mid-IR band, while for the remainders the excess radio emission is the only indicator of AGN activity. The fraction of radio-excess AGN increases with X-ray luminosity reaching ~60% at Lx~10^44-10^45 erg/s, making these sources an important part of the total AGN population. However, almost half (24/51) of these radio-excess AGN are not detected in the deep Chandra X-ray data, suggesting that some of these sources might be heavily obscured. We also find that the specific star formation rates (sSFRs) of the radio-excess AGN are on average lower that those observed for X-ray selected AGN hosts, indicating that our sources are forming stars more slowly than typical AGN hosts, and possibly their star formation is progressively quenching.

History

Publication status

  • Published

File Version

  • Published version

Journal

Astronomy and Astrophysics

ISSN

0004-6361

Publisher

EDP Sciences

Issue

A59

Volume

549

Page range

1-28

Department affiliated with

  • Physics and Astronomy Publications

Full text available

  • No

Peer reviewed?

  • Yes

Legacy Posted Date

2014-05-21

First Compliant Deposit (FCD) Date

2014-05-21

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