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Radio spectral properties of star-forming galaxies in the MIGHTEE-COSMOS field and their impact on the far-infrared-radio correlation

An, Fangxia; Vaccari, M; Smail, Ian; Jarvis, MJ; Whittam, IH; Hale, CL; Jin, S; Collier, JD; Daddi, E; Delhaize, J; Frank, B; Murphy, EJ; Prescott, M; Sekhar, S; Taylor, AR; Ao, Y; Knowles, K; Marchetti, L; Randriamampandry, SM; Randriamanakoto, Z

Radio spectral properties of star-forming galaxies in the MIGHTEE-COSMOS field and their impact on the far-infrared-radio correlation Thumbnail


Authors

Fangxia An

M Vaccari

MJ Jarvis

IH Whittam

CL Hale

S Jin

JD Collier

E Daddi

J Delhaize

B Frank

EJ Murphy

M Prescott

S Sekhar

AR Taylor

Y Ao

K Knowles

L Marchetti

SM Randriamampandry

Z Randriamanakoto



Abstract

We study the radio spectral properties of 2094 star-forming galaxies (SFGs) by combining our early science data from the MeerKAT International GHz Tiered Extragalactic Exploration (MIGHTEE) survey with VLA, GMRT radio data, and rich ancillary data in the COSMOS field. These SFGs are selected at VLA 3 GHz, and their flux densities from MeerKAT 1.3 GHz and GMRT 325 MHz imaging data are extracted using the ‘superdeblending’ technique. The median radio spectral index is α3GHz1.3GHz=−0.80±0.01 without significant variation across the rest-frame frequencies ∼1.3–10 GHz, indicating radio spectra dominated by synchrotron radiation. On average, the radio spectrum at observer-frame 1.3–3 GHz slightly steepens with increasing stellar mass with a linear fitted slope of β = −0.08 ± 0.01, which could be explained by age-related synchrotron losses. Due to the sensitivity of GMRT 325 MHz data, we apply a further flux density cut at 3 GHz (⁠S3GHz≥50μJy) and obtain a sample of 166 SFGs with measured flux densities at 325 MHz, 1.3 GHz, and 3 GHz. On average, the radio spectrum of SFGs flattens at low frequency with the median spectral indices of α1.3GHz325MHz=−0.59+0.02−0.03 and α3.0GHz1.3GHz=−0.74+0.01−0.02⁠. At low frequency, our stacking analyses show that the radio spectrum also slightly steepens with increasing stellar mass. By comparing the far-infrared-radio correlations of SFGs based on different radio spectral indices, we find that adopting α3GHz1.3GHz for k-corrections will significantly underestimate the infrared-to-radio luminosity ratio (qIR) for >17 per cent of the SFGs with measured flux density at the three radio frequencies in our sample, because their radio spectra are significantly flatter at low frequency (0.33–1.3 GHz).

Citation

An, F., Vaccari, M., Smail, I., Jarvis, M., Whittam, I., Hale, C., …Randriamanakoto, Z. (2021). Radio spectral properties of star-forming galaxies in the MIGHTEE-COSMOS field and their impact on the far-infrared-radio correlation. Monthly Notices of the Royal Astronomical Society, 507(2), 2643-2658. https://doi.org/10.1093/mnras/stab2290

Journal Article Type Article
Acceptance Date Aug 4, 2021
Online Publication Date Aug 9, 2021
Publication Date 2021-10
Deposit Date Oct 8, 2021
Publicly Available Date Mar 29, 2024
Journal Monthly Notices of the Royal Astronomical Society
Print ISSN 0035-8711
Electronic ISSN 1365-2966
Publisher Royal Astronomical Society
Peer Reviewed Peer Reviewed
Volume 507
Issue 2
Pages 2643-2658
DOI https://doi.org/10.1093/mnras/stab2290

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Copyright Statement
This article has been accepted for publication in Monthly notices of the Royal Astronomical Society. ©: 2021 The Author(s). Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.





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