CEERS: Spatially Resolved UV and mid-IR Star Formation in Galaxies at 0.2 < z < 2.5: The Picture from the Hubble and James Webb Space Telescopes

Abstract

We present the mid-IR (MIR) morphologies for 64 star-forming galaxies at $0.2<z<2.5$ with stellar mass ${\mathrm{M}}_{\ast }>10^9{\mathrm{M}}_{\odot }$ using JWST MIRI observations from the Cosmic Evolution Early Release Science survey (CEERS). The MIRI bands span the MIR (7.7--21~$\hat{I}¼$m), enabling us to measure the effective radii ($R_{\mathrm{eff}}$) and Sérsic indexes of these SFGs at rest-frame 6.2 and 7.7 $\hat{I}¼$m, which contains strong emission from Polycyclic aromatic hydrocarbon (PAH) features, a well-established tracer of star formation in galaxies. We define a ``PAH-band'' as the MIRI bandpass that contains these features at the redshift of the galaxy. We then compare the galaxy morphologies in the PAH-bands to those in rest-frame Near-UV (NUV) using HST ACS/F435W or ACS/F606W and optical/near-IR using HST WFC3/F160W imaging from UVCANDELS and CANDELS, where the NUV-band and F160W trace the profile of (unobscured) massive stars and the stellar continuum, respectively. The $R_{\mathrm{eff}}$ of galaxies in the PAH-band are slightly smaller ($\sim$10\%) than those in F160W for galaxies with ${\mathrm{M}}_{\ast }\gtrsim 10^{9.5}{\mathrm{M}}_{\odot }$ at $z\le 1.2$, but the PAH-band and F160W have a similar fractions of light within 1 kpc. In contrast, the $R_{\mathrm{eff}}$ of galaxies in the NUV-band are larger, with lower fractions of light within 1 kpc compared to F160W for galaxies at $z\le 1.2$. Using the MIRI data to estimate the $\mathrm{SF}{\mathrm{R}}_{\mathrm{IR}}$ surface density, we find the correlation between the $\mathrm{SF}{\mathrm{R}}_{\mathrm{IR}}$ surface density and stellar mass has a steeper slope than that of the $\mathrm{SF}{\mathrm{R}}_{\mathrm{UV}}$ surface density and stellar mass, suggesting more massive galaxies having increasing amounts of obscured fraction of star formation in their inner regions. This paper demonstrates how the high-angular resolution data from JWST/MIRI can reveal new information about the morphology of obscured-star formation.

28 pages, 11 figures, Accepted by ApJ