Physical Characterization of an Unlensed, Dusty Star-forming Galaxy at z = 5.85
Journal article, 2019
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 o˙ yr-1 and 220 M o˙ yr-1, total molecular hydrogen gas mass of (1.7 ± 0.4) × 1011 M o˙, dust mass of (1.3 ± 0.3) × 109 M o˙, and stellar mass of (3.2-1.5+1.0) × 109 M o˙. The total halo mass, (3.3 ± 0.8) × 1012 M o˙, is predicted to exceed 1015 M o˙ 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).
Author
Caitlin M. Casey
University of Texas
J. A. Zavala
University of Texas
Manuel Aravena
Diego Portales University
Matthieu Béthermin
Laboratoire d'Astrophysique de Marseille
Karina I. Caputi
University of Groningen
University of Copenhagen
Jaclyn B. Champagne
University of Texas
D. L. Clements
Imperial College London
E. Da Cunha
ARC Centre of Excellence for All Sky Astrophysics in 3 Dimensions (ASTRO 3D)
University of Western Australia
Australian National University
Patrick Drew
University of Texas
Steven L. Finkelstein
University of Texas
Christopher C. Hayward
Flatiron Institute
Jeyhan S. Kartaltepe
Rochester Institute of Technology
Kirsten Kraiberg Knudsen
Chalmers, Space, Earth and Environment, Astronomy and Plasmaphysics
Anton M. Koekemoer
Space Telescope Science Institute (STScI)
Georgios E. Magdis
University of Copenhagen
Niels Bohr Institute
Allison Man
University of Toronto
Sinclaire M. Manning
University of Texas
N. Z. Scoville
California Institute of Technology (Caltech)
K. Sheth
National Aeronautics and Space Administration (NASA)
Justin Spilker
University of Texas
Johannes Staguhn
National Aeronautics and Space Administration (NASA)
Johns Hopkins University
Margherita Talia
University of Bologna
Yoshiaki Taniguchi
The Open University of Japan
Sune Toft
Niels Bohr Institute
University of Copenhagen
E. Treister
Pontificia Universidad Catolica de Chile
Min Yun
University of Massachusetts
Astrophysical Journal
0004-637X (ISSN) 1538-4357 (eISSN)
Vol. 887 1 55Subject Categories (SSIF 2011)
Analytical Chemistry
Astronomy, Astrophysics and Cosmology
Chemical Process Engineering
DOI
10.3847/1538-4357/ab52ff