The infrared-radio correlation of star-forming galaxies is strongly M⋆-dependent but nearly redshift-invariant since z ∼ 4

I. Delvecchio (1, 2) , E. Daddi (1) , M. T. Sargent (3) , M. J. Jarvis (4, 5) , D. Elbaz (1) , S. Jin (6, 7) , D. Liu (8) , I. H. Whittam (4, 5) , H. Algera (9) , R. Carraro (10) , C. D’eugenio (1) , J. Delhaize (11) , B. S. Kalita (1) , S. Leslie (9) , D. Cs. Molnár (12) , M. Novak (8) , I. Prandoni (13) , V. Smolčić (14) , Y. Ao , M. Aravena , F. Bournaud (1) , J. D. Collier , S. M. Randriamampandry , Z. Randriamanakoto , G. Rodighiero (15) , J. Schober (16) , S. V. White (17) , G. Zamorani (18)

1 AIM (UMR7158 / UMR_E_9005 / UM_112) - Astrophysique Interprétation Modélisation
2 OAM - INAF - Osservatorio Astronomico di Milano
3 Astronomy Centre, University of Sussex
4 Oxford Astrophysics
5 UWC - University of the Western Cape
6 IAC - Instituto de Astrofisica de Canarias
7 Departamento de Astrofísica [La laguna]
8 MPIA - Max-Planck-Institut für Astronomie
9 Leiden Observatory [Leiden]
10 Universidad de Valparaiso [Chile]
11 University of Cape Town
12 OAC - INAF - Osservatorio Astronomico di Cagliari
13 IRA - Istituto di Radioastronomia [Bologna]
14 University of Zagreb
15 Unipd - Università degli Studi di Padova = University of Padua
16 EPFL Laboratoire d’astrophysique
17 Rhodes University, Grahamstown
18 OABO - INAF - Osservatorio Astronomico di Bologna

Over the past decade, several works have used the ratio between total (rest 8−1000 μm) infrared and radio (rest 1.4 GHz) luminosity in star-forming galaxies (qIR), often referred to as the infrared-radio correlation (IRRC), to calibrate the radio emission as a star formation rate (SFR) indicator. Previous studies constrained the evolution of qIR with redshift, finding a mild but significant decline that is yet to be understood. Here, for the first time, we calibrate qIR as a function of both stellar mass (M⋆) and redshift, starting from an M⋆-selected sample of > 400 000 star-forming galaxies in the COSMOS field, identified via (NUV − r)/(r − J) colours, at redshifts of 0.1 < z < 4.5. Within each (M⋆,z) bin, we stacked the deepest available infrared/sub-mm and radio images. We fit the stacked IR spectral energy distributions with typical star-forming galaxy and IR-AGN templates. We then carefully removed the radio AGN candidates via a recursive approach. We find that the IRRC evolves primarily with M⋆, with more massive galaxies displaying a systematically lower qIR. A secondary, weaker dependence on redshift is also observed. The best-fit analytical expression is the following: qIR(M⋆, z) = (2.646 ± 0.024) × (1 + z)( − 0.023 ± 0.008)–(0.148 ± 0.013) × (log M⋆/M⊙ − 10). Adding the UV dust-uncorrected contribution to the IR as a proxy for the total SFR would further steepen the qIR dependence on M⋆. We interpret the apparent redshift decline reported in previous works as due to low-M⋆ galaxies being progressively under-represented at high redshift, as a consequence of binning only in redshift and using either infrared or radio-detected samples. The lower IR/radio ratios seen in more massive galaxies are well described by their higher observed SFR surface densities. Our findings highlight the fact that using radio-synchrotron emission as a proxy for SFR requires novel M⋆-dependent recipes that will enable us to convert detections from future ultra-deep radio surveys into accurate SFR measurements down to low-M⋆ galaxies with low SFR.

Mots clés: galaxies: star formation; radio continuum: galaxies; infrared: galaxies; galaxies: active; galaxies: evolution

Domaines: Astrophysique [astro-ph]

I. Delvecchio, E. Daddi, M. T. Sargent, M. J. Jarvis, D. Elbaz, et al.. The infrared-radio correlation of star-forming galaxies is strongly M⋆-dependent but nearly redshift-invariant since z ∼ 4. Astronomy and Astrophysics - A&A, 2021, 647, pp.A123. ⟨10.1051/0004-6361/202039647⟩. ⟨cea-03174102⟩