Two Massive, Compact, and Dust-obscured Candidate z ≃ 8 Galaxies Discovered by JWST

October 2023 • 2023ApJ...956...61A

Authors • Akins, Hollis B. • Casey, Caitlin M. • Allen, Natalie • Bagley, Micaela B. • Dickinson, Mark • Finkelstein, Steven L. • Franco, Maximilien • Harish, Santosh • Arrabal Haro, Pablo • Ilbert, Olivier • Kartaltepe, Jeyhan S. • Koekemoer, Anton M. • Liu, Daizhong • Long, Arianna S. • McCracken, Henry Joy • Paquereau, Louise • Papovich, Casey • Pirzkal, Nor • Rhodes, Jason • Robertson, Brant E. • Shuntov, Marko • Toft, Sune • Yang, Guang • Barro, Guillermo • Bisigello, Laura • Buat, Véronique • Champagne, Jaclyn B. • Cooper, Olivia • Costantin, Luca • de La Vega, Alexander • Drakos, Nicole E. • Faisst, Andreas • Fontana, Adriano • Fujimoto, Seiji • Gillman, Steven • Gómez-Guijarro, Carlos • Gozaliasl, Ghassem • Hathi, Nimish P. • Hayward, Christopher C. • Hirschmann, Michaela • Holwerda, Benne W. • Jin, Shuowen • Kocevski, Dale D. • Kokorev, Vasily • Lambrides, Erini • Lucas, Ray A. • Magdis, Georgios E. • Magnelli, Benjamin • McKinney, Jed • Mobasher, Bahram • Pérez-González, Pablo G. • Rich, R. Michael • Seillé, Lise-Marie • Talia, Margherita • Urry, C. Megan • Valentino, Francesco • Whitaker, Katherine E. • Yung, L. Y. Aaron • Zavala, Jorge • Cosmos-Web Team • Ceers Team

Abstract • We present a search for extremely red, dust-obscured, z > 7 galaxies with JWST/NIRCam+MIRI imaging over the first 20 arcmin² of publicly available Cycle 1 data from the COSMOS-Web, CEERS, and PRIMER surveys. Based on their red color in F277W-F444W (~2.5 mag) and detection in MIRI/F770W (~25 mag), we identify two galaxies, COS-z8M1 and CEERS-z7M1, that have best-fit photometric redshifts of $z={8.4}_{-0.4}^{+0.3}$ and ${7.6}_{-0.1}^{+0.1}$ , respectively. We perform spectral energy distribution fitting with a variety of codes (including BAGPIPES, PROSPECTOR, BEAGLE, and CIGALE) and find a >95% probability that these indeed lie at z > 7. Both sources are compact (R _eff ≲ 200 pc) and highly obscured (A _V ~ 1.5-2.5) and, at our best-fit redshift estimates, likely have strong [O III]+Hβ emission contributing to their 4.4 μm photometry. We estimate stellar masses of ~10¹⁰ M _⊙ for both sources; by virtue of detection in MIRI at 7.7 μm, these measurements are robust to the inclusion of bright emission lines, for example, from an active galactic nucleus. We identify a marginal (2.9σ) Atacama Large Millimeter/submillimeter Array detection at 2 mm within 0.″5 of COS-z8M1, which, if real, would suggest a remarkably high IR luminosity of ~10¹² L _⊙. These two galaxies, if confirmed at z ~ 8, would be extreme in their stellar and dust masses and may be representative of a substantial population of highly dust-obscured galaxies at cosmic dawn.

Links

• SIMBAD http://simbad.u-strasbg.fr/simbo.pl?bibcode=2023ApJ...956...61A
• PREPRINT http://arxiv.org/abs/2304.12347
• DATA http://archive.eso.org/bin/ads2eso?2023ApJ...956...61A
• DATA https://archive.stsci.edu/mastbibref.php?bibcode=2023ApJ...956...61A
• DATA https://doi.org/10.17909/4eps-dc89
• DATA https://hst.esac.esa.int/ehst/#/pages/search;bibcode=2023ApJ...956...61A
• DATA https://irsa.ipac.caltech.edu/bibdata/2023/A/2023ApJ...956...61A.html
• ELECTR https://doi.org/10.3847%2F1538-4357%2Facef21