In:
Astronomy & Astrophysics, EDP Sciences, Vol. 678 ( 2023-10), p. A83-
Abstract:
Aims. We study the stellar (i.e., rest-optical) and dust-obscured star-forming (i.e., rest-mid-infrared) morphologies (i.e., sizes and Sérsic indices) of star-forming galaxies (SFGs) at 0.1 〈 z 〈 2.5. Methods. We combined Hubble Space Telescope (HST) images from the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey (CANDELS) with JWST images from the Cosmic Evolution Early Release Science (CEERS) survey to measure the stellar and dust-obscured star formation distributions of 69 SFGs. Rest-mid-infrared (rest-MIR) morphologies were determined using a Markov chain Monte Carlo (MCMC) approach applied to the sharpest Mid-InfraRed Instrument (MIRI) images (i.e., shortest wavelength) dominated by dust emission ( S ν dust / S ν total 〉 75%), as inferred for each galaxy from our optical-to-far-infrared spectral energy distribution fits with CIGALE . Rest-MIR Sérsic indices were only measured for the brightest MIRI sources, that is, with a signal-to-noise (S/N) greater than 75 (35 galaxies). At a lower S/N, simulations do indeed show that simultaneous measurements of both the size and Sérsic index become less reliable. We extended our study to fainter sources (i.e., S / N 〉 10; 69 galaxies) by restricting our structural analysis to their rest-MIR sizes ( Re MIR ) and by fixing their Sérsic index to a value of one. Results. Our MIRI-selected sample corresponds to a mass-complete sample ( 〉 80%) of SFGs down to stellar masses 10 9.5 , 10 9.5 , and 10 10 M ⊙ at z ∼ 0.3, 1, and 2, respectively. The rest-MIR Sérsic index of bright galaxies ( S / N 〉 75) has a median value of 0.7 −0.3 +0.8 (the range corresponds to the 16th and 84th percentiles), which is in good agreement with their median rest-optical Sérsic indices. The Sérsic indices as well as the distribution of the axis ratio of these galaxies suggest that they have a disk-like morphology in the rest-MIR. Galaxies above the main sequence (MS) of star formation (i.e., starbursts) have rest-MIR sizes that are, on average, a factor ∼2 smaller than their rest-optical sizes ( Re Opt. ). The median rest-optical to rest-MIR size ratio of MS galaxies increases with their stellar mass, from 1.1 −0.2 +0.4 at ∼10 9.8 M ⊙ to 1.6 −0.3 +1.0 at ∼10 11 M ⊙ . This mass-dependent trend resembles the one found in the literature between the rest-optical and rest-near-infrared sizes of SFGs, suggesting that it is primarily due to radial color gradients affecting rest-optical sizes and that the sizes of the stellar and star-forming components of SFGs are, on average, consistent at all masses. There is, however, a small population of SFGs (∼15%) with a compact star-forming component embedded in a larger stellar structure, with Re Opt. c 〉 1.8 × Re MIR . This population could be the missing link between galaxies with an extended stellar component and those with a compact stellar component, the so-called blue nuggets.
Type of Medium:
Online Resource
ISSN:
0004-6361
,
1432-0746
DOI:
10.1051/0004-6361/202347052
Language:
English
Publisher:
EDP Sciences
Publication Date:
2023
detail.hit.zdb_id:
1458466-9
SSG:
16,12
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