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Physical Characterization of an Unlensed, Dusty Star-forming Galaxy at z = 5.85

Abstract : We present a physical characterization of MM J100026.36+021527.9 (a.k.a. “MAMBO-9”), a dusty star-forming galaxy (DSFG) at z = 5.850 ± 0.001. This is the highest-redshift unlensed DSFG (and fourth most distant overall) found to date and is the first source identified in a new 2 mm blank-field map in the COSMOS field. Though identified in prior samples of DSFGs at 850 μm to 1.2 mm with unknown redshift, the detection at 2 mm prompted further follow-up as it indicated a much higher probability that the source was likely to sit at z > 4. Deep observations from the Atacama Large Millimeter and submillimeter Array (ALMA) presented here confirm the redshift through the secure detection of 12CO(J = 6→5) and p-H2O (21,1 → 20,2). MAMBO-9 is composed of a pair of galaxies separated by 6 kpc with corresponding star formation rates of 590 M yr-1 and 220 M yr-1, total molecular hydrogen gas mass of (1.7 ± 0.4) × 1011 M , dust mass of (1.3 ± 0.3) × 109 M , and stellar mass of ({3.2}-1.5+1.0) × 109 M . The total halo mass, (3.3 ± 0.8) × 1012 M , is predicted to exceed 1015 M by z = 0. The system is undergoing a merger-driven starburst that will increase the stellar mass of the system tenfold in τ depl = 40-80 Myr, converting its large molecular gas reservoir (gas fraction of {96}-2+1 % ) into stars. MAMBO-9 evaded firm spectroscopic identification for a decade, following a pattern that has emerged for some of the highest-redshift DSFGs found. And yet, the systematic identification of unlensed DSFGs like MAMBO-9 is key to measuring the global contribution of obscured star formation to the star formation rate density at z ≳ 4, the formation of the first massive galaxies, and the formation of interstellar dust at early times (≲1 Gyr).
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Contributor : Nathalie Pothier Connect in order to contact the contributor
Submitted on : Thursday, May 12, 2022 - 4:44:49 PM
Last modification on : Saturday, May 14, 2022 - 3:03:48 AM

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Caitlin M. Casey, Jorge A. Zavala, Manuel Aravena, Matthieu Béthermin, Karina I. Caputi, et al.. Physical Characterization of an Unlensed, Dusty Star-forming Galaxy at z = 5.85. The Astrophysical Journal, 2019, 887, ⟨10.3847/1538-4357/ab52ff⟩. ⟨insu-03666701⟩



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