| Abstract |
We use PHANGS-JWST data to identify and classify 1271 compact 21 $\mu$m sources in four nearby galaxies using MIRI F2100W data. We identify sources using a dendrogram-based algorithm, and we measure the background-subtracted flux densities for JWST bands from 2 $\mu$m to 21 $\mu$m. Using the SED in JWST as well as HST bands, plus ALMA and MUSE/VLT observations, we classify the sources by eye. Then we use this classification to define regions in color-color space, and so establish a quantitative framework for classifying sources. We identify 1085 sources as belonging to the ISM of the target galaxies with the remainder being dusty stars or background galaxies. These 21 $\mu$m sources are strongly spatially associated with HII regions ($>92\%$ of sources), while 74$\%$ of sources are coincident with a stellar association defined in the HST data. Using SED fitting, we find that the stellar masses of the 21 $\mu$m sources span a range of 10$^{2}$ to 10$^{4}~M_\odot$ with mass-weighted ages down to 2 Myr. There is a tight correlation between attenuation-corrected H$\alpha$ and 21 $\mu$m luminosity for $L_{\nu,\mathrm{F2100W}}>10^{19}~\mathrm{W~Hz}^{-1}$. Young embedded source candidates selected at 21 $\mu$m are found below this threshold and have $M_\star < 10^{3}~M_\odot$. |
| Authors |
Hamid Hassani  , Erik Rosolowsky , Adam K. Leroy , M. Boquien , Janice Lee , Ashley T. Barnes , Francesco Belfiore , Frank Bigiel , Yixian Cao , Mélanie Chevance , Daniel A. Dale  , Oleg V. Egorov , Éric Emsellem , Christopher M. Faesi , Kathryn Grasha , Jaeyeon Kim , Ralf S. Klessen , Kathryn Kreckel , J. M. Diederik Kruijssen , Kirsten L. Larson , Sharon E. Meidt , Karin Sandström , E. Schinnerer , David A. Thilker , Elizabeth J. Watkins , Bradley C. Whitmore , Thomas G. Williams
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