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| Autors principals: | , , , , , , , , , , , , , , , , |
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| Format: | Preprint |
| Publicat: |
2025
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| Matèries: | |
| Accés en línia: | https://arxiv.org/abs/2509.17536 |
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| author | Peluso, Giorgia Delvecchio, Ivan Radcliffe, Jack Daddi, Emanuele Deane, Roger Jarvis, Matt Zamorani, Giovanni Prandoni, Isabella Gitti, Myriam Spingola, Cristiana Ubertosi, Francesco Sargent, Mark Smolcic, Vernesa Wang, Wuji Delhaize, Jacinta Jin, Shuowen Deller, Adam |
| author_facet | Peluso, Giorgia Delvecchio, Ivan Radcliffe, Jack Daddi, Emanuele Deane, Roger Jarvis, Matt Zamorani, Giovanni Prandoni, Isabella Gitti, Myriam Spingola, Cristiana Ubertosi, Francesco Sargent, Mark Smolcic, Vernesa Wang, Wuji Delhaize, Jacinta Jin, Shuowen Deller, Adam |
| contents | It is well-known that star-forming galaxies (SFGs) exhibit a tight correlation between their radio and infrared emissions, commonly referred to as the infrared-radio correlation (IRRC). Recent empirical studies have reported a dependence of the IRRC on the galaxy stellar mass, in which more massive galaxies tend to show lower infrared-to-radio ratios (qIR) with respect to less massive galaxies. One possible, yet unexplored, explanation is a residual contamination of the radio emission from active galactic nuclei (AGN), not captured through "radio-excess" diagnostics. To investigate this hypothesis, we aim to statistically quantify the contribution of AGN emission to the radio luminosities of SFGs located within the scatter of the IRRC. Our VLBA program "AGN-sCAN" has targeted 500 galaxies that follow the qIR distribution of the IRRC, i.e., with no prior evidence for radio-excess AGN emission based on low-resolution (~ arcsec) VLA radio imaging. Our VLBA 1.4 GHz observations reach a 5-sigma sensitivity limit of 25 microJy/beam, corresponding to a radio brightness temperature of Tb ~ 10^5 K. This classification serves as a robust AGN diagnostic, regardless of the host galaxy's star formation rate. We detect four VLBA sources in the deepest regions, which are also the faintest VLBI-detected AGN in SFGs to date. The effective AGN detection rate is 9%, when considering a control sample matched in mass and sensitivity, which is in good agreement with the extrapolation of previous radio AGN number counts. Despite the non-negligible AGN flux contamination (~ 30%) in our individual VLBA detections, we find that the peak of the qIR distribution is completely unaffected by this correction. We conclude that residual AGN contamination from non-radio-excess AGN is unlikely to be the primary driver of the M* - dependent IRRC. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2509_17536 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Investigating the influence of radio-faint AGN activity on the infrared-radio correlation of massive galaxies Peluso, Giorgia Delvecchio, Ivan Radcliffe, Jack Daddi, Emanuele Deane, Roger Jarvis, Matt Zamorani, Giovanni Prandoni, Isabella Gitti, Myriam Spingola, Cristiana Ubertosi, Francesco Sargent, Mark Smolcic, Vernesa Wang, Wuji Delhaize, Jacinta Jin, Shuowen Deller, Adam Astrophysics of Galaxies It is well-known that star-forming galaxies (SFGs) exhibit a tight correlation between their radio and infrared emissions, commonly referred to as the infrared-radio correlation (IRRC). Recent empirical studies have reported a dependence of the IRRC on the galaxy stellar mass, in which more massive galaxies tend to show lower infrared-to-radio ratios (qIR) with respect to less massive galaxies. One possible, yet unexplored, explanation is a residual contamination of the radio emission from active galactic nuclei (AGN), not captured through "radio-excess" diagnostics. To investigate this hypothesis, we aim to statistically quantify the contribution of AGN emission to the radio luminosities of SFGs located within the scatter of the IRRC. Our VLBA program "AGN-sCAN" has targeted 500 galaxies that follow the qIR distribution of the IRRC, i.e., with no prior evidence for radio-excess AGN emission based on low-resolution (~ arcsec) VLA radio imaging. Our VLBA 1.4 GHz observations reach a 5-sigma sensitivity limit of 25 microJy/beam, corresponding to a radio brightness temperature of Tb ~ 10^5 K. This classification serves as a robust AGN diagnostic, regardless of the host galaxy's star formation rate. We detect four VLBA sources in the deepest regions, which are also the faintest VLBI-detected AGN in SFGs to date. The effective AGN detection rate is 9%, when considering a control sample matched in mass and sensitivity, which is in good agreement with the extrapolation of previous radio AGN number counts. Despite the non-negligible AGN flux contamination (~ 30%) in our individual VLBA detections, we find that the peak of the qIR distribution is completely unaffected by this correction. We conclude that residual AGN contamination from non-radio-excess AGN is unlikely to be the primary driver of the M* - dependent IRRC. |
| title | Investigating the influence of radio-faint AGN activity on the infrared-radio correlation of massive galaxies |
| topic | Astrophysics of Galaxies |
| url | https://arxiv.org/abs/2509.17536 |