The Circumgalactic Medium of Submillimeter Galaxies. II. Unobscured QSOs within Dusty Starbursts and QSO Sightlines with Impact Parameters below 100 kpc

Journal Article · Tue Aug 01 04:00:00 EDT 2017 · Astrophysical Journal

DOI:https://doi.org/10.3847/1538-4357/AA7C63· OSTI ID:22875972

Fu, Hai; Isbell, Jacob ^[1]; Casey, Caitlin M. ^[2]; Cooray, Asantha ^[3]; Prochaska, J. Xavier ^[4]; Scoville, Nick ^[5]; Stockton, Alan ^[6]

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1. Department of Physics and Astronomy, University of Iowa, Iowa City, IA 52242 (United States)
2. Department of Astronomy, University of Texas at Austin, 2515 Speedway Boulevard, Stop C1400, Austin, TX 78712 (United States)
3. Department of Physics and Astronomy, University of California, Irvine, CA 92697 (United States)
4. Department of Astronomy and Astrophysics, UCO/Lick Observatory, University of California, 1156 High Street, Santa Cruz, CA 95064 (United States)
5. California Institute of Technology, MC 249-17, 1200 East California Boulevard, Pasadena, CA 91125 (United States)
6. Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822 (United States)

We present Atacama Large Millimeter/submillimeter Array (ALMA) 870 μm observations of 29 bright Herschel sources near high-redshift QSOs. The observations confirm that 20 of the Herschel sources are submillimeter-bright galaxies (SMGs) and identify 16 new SMG−QSO pairs that are useful to studies of the circumgalactic medium (CGM) of SMGs. Eight out of the 20 SMGs are blends of multiple 870 μm sources. The angular separations for six of the Herschel-QSO pairs are less than 10″, comparable to the sizes of the Herschel beam and the ALMA primary beam. We find that four of these six “pairs” are actually QSOs hosted by SMGs. No additional submillimeter companions are detected around these QSOs, and the rest-frame ultraviolet spectra of the QSOs show no evidence of significant reddening. Black hole accretion and star formation contribute almost equally in bolometric luminosity in these galaxies. The SMGs hosting QSOs show similar source sizes, dust surface densities, and star formation rate surface densities to those of other SMGs in the sample. We find that the black holes are growing ∼3× faster than the galaxies when compared to the present-day black hole/galaxy mass ratio, suggesting a QSO duty cycle of ≲30% in SMGs at z∼3. The remaining two Herschel-detected QSOs are undetected at 870 μm, but each has an SMG “companion” only 9″ and 12″ away (71 and 95 kpc at z = 3). They could be either merging or projected pairs. If the former, they would represent a rare class of “wet−dry” mergers. If the latter, the QSOs would, for the first time, probe the CGM of SMGs at impact parameters below 100 kpc.

• OSTI ID: 22875972
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 2 Vol. 844; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
BLACK HOLES
BOLOMETERS
COMPARATIVE EVALUATIONS
COSMIC DUST
DENSITY
GALAXIES
IMPACT PARAMETER
LUMINOSITY
MASS
QUASARS
RED SHIFT
STARS
ULTRAVIOLET RADIATION