2017A&A...602A...4D


Query : 2017A&A...602A...4D

2017A&A...602A...4D - Astronomy and Astrophysics, volume 602A, 4-4 (2017/6-1)

The VLA-COSMOS 3 GHz Large Project: The infrared-radio correlation of star-forming galaxies and AGN to z ≤ 6.

DELHAIZE J., SMOLCIC V., DELVECCHIO I., NOVAK M., SARGENT M., BARAN N., MAGNELLI B., ZAMORANI G., SCHINNERER E., MURPHY E.J., ARAVENA M., BERTA S., BONDI M., CAPAK P., CARILLI C., CILIEGI P., CIVANO F., ILBERT O., KARIM A., LAIGLE C., LE FEVRE O., MARCHESI S., McCRACKEN H.J., SALVATO M., SEYMOUR N. and TASCA L.

Abstract (from CDS):

We examine the behaviour of the infrared-radio correlation (IRRC) over the range 0<z≤6 using new, highly sensitive 3GHz observations with the Karl G. Jansky Very Large Array (VLA) and infrared data from the Herschel Space Observatory in the 2deg2 COSMOS field. We distinguish between objects where emission is believed to arise solely from star-formation, and those where an active galactic nucleus (AGN) is thought to be present. We account for non-detections in the radio or in the infrared using a doubly-censored survival analysis. We find that the IRRC of star-forming galaxies, quantified by the infrared-to-1.4GHz radio luminosity ratio (qTIR), decreases with increasing redshift: qTIR(z)=(2.88±0.03)(1+z)–0.19±0.01. This is consistent with several previous results from the literature. Moderate-to-high radiative luminosity AGN do not follow the same qTIR(z) trend as star-forming galaxies, having a lower normalisation and steeper decrease with redshift. We cannot rule out the possibility that unidentified AGN contributions only to the radio regime may be steepening the observed qTIR(z) trend of the star-forming galaxy population. We demonstrate that the choice of the average radio spectral index directly affects the normalisation, as well as the derived trend with redshift of the IRRC. An increasing fractional contribution to the observed 3GHz flux by free-free emission of star-forming galaxies may also affect the derived evolution. However, we find that the standard (M82-based) assumption of the typical radio spectral energy distribution (SED) for star-forming galaxies is inconsistent with our results. This suggests a more complex shape of the typical radio SED for star-forming galaxies, and that imperfect K corrections in the radio may govern the derived trend of decreasing qTIR with increasing redshift. A more detailed understanding of the radio spectrum is therefore required for robust K corrections in the radio and to fully understand the cosmic evolution of the IRRC. Lastly, we present a redshift-dependent relation between rest-frame 1.4GHz radio luminosity and star formation rate taking the derived redshift trend into account.

Abstract Copyright: © ESO, 2017

Journal keyword(s): galaxies: evolution - galaxies: star formation - radio continuum: galaxies - infrared: galaxies - infrared: galaxies

Simbad objects: 4

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Number of rows : 4
N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2022
#notes
1 NAME COSMOS Field reg 10 00 28.60 +02 12 21.0           ~ 2503 0
2 NGC 4038 GiP 12 01 53.002 -18 52 03.32   10.91   9.74 11.0 ~ 1296 1
3 NGC 4039 GiP 12 01 53.8 -18 53 06   11.08   9.77   ~ 1145 1
4 NAME GOODS-N Field reg 12 36 55.0 +62 14 15           ~ 1022 1

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2022.05.26-01:33:48

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