Discovery of a Dark, Massive, ALMA-only Galaxy at z ∼ 5–6 in a Tiny 3 mm Survey
AuthorWilliams, Christina C.
AffiliationUniv Arizona, Steward Observ
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PublisherIOP PUBLISHING LTD
CitationChristina C. Williams et al 2019 ApJ 884 154
RightsCopyright © 2019. The American Astronomical Society. All rights reserved.
Collection InformationThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at firstname.lastname@example.org.
AbstractWe report the serendipitous detection of two 3 mm continuum sources found in deep ALMA Band 3 observations to study intermediate-redshift galaxies in the COSMOS field. One is near a foreground galaxy at 1 3, but is a previously unknown dust-obscured star-forming galaxy (DSFG) at probable z(CO) = 3.329, illustrating the risk of misidentifying shorter wavelength counterparts. The optical-to-millimeter spectral energy distribution (SED) favors a gray lambda(-0.4) attenuation curve and results in significantly larger stellar mass and SFR compared to a Calzetti starburst law, suggesting caution when relating progenitors and descendants based on these quantities. The other source is missing from all previous optical/near-infrared/submillimeter/radio catalogs ("ALMA-only"), and remains undetected even in stacked ultradeep optical (>29.6 AB) and near-infrared (>27.9 AB) images. Using the ALMA position as a prior reveals faint signal-to-noise ratio similar to 3 measurements in stacked IRAC 3.6+4.5, ultradeep SCUBA2 850 mu m, and VLA 3 GHz, indicating the source is real. The SED is robustly reproduced by a massive M* = 10(10.8)M(circle dot) and M-gas= 10(11)M(circle dot), highly obscured AV similar to 4, star-forming SFR similar to 300 M-circle dot yr(-1) galaxy at redshift z = 5.5 +/- 1.1 The ultrasmall 8 arcmin(2) survey area implies a large yet uncertain contribution to the cosmic star formation rate density CSFRD(z = 5) similar to 0.9 x 10(-2) Me yr(-1) Mpc(-3), comparable to all ultraviolet-selected galaxies combined. These results indicate the existence of a prominent population of DSFGs at z > 4, below the typical detection limit of bright galaxies found in single-dish submillimeter surveys, but with larger space densities similar to 3 x 10(-5) Mpc(-3), higher duty cycles of 50%-100%, contributing more to the CSFRD, and potentially dominating the high-mass galaxy stellar mass function.
VersionFinal published version
SponsorsNational Science Foundation Astronomy and Astrophysics Fellowship [AST-1701546]; NSF Astronomy and Astrophysics Postdoctoral FellowshipNational Science Foundation (NSF) [AST-1701487]