ALMA Observations Show Major Mergers Among the Host Galaxies of Fast-growing, High-redshift, Supermassive Black Holes

Journal Article · Fri Feb 10 04:00:00 EST 2017 · Astrophysical Journal

DOI:https://doi.org/10.3847/1538-4357/836/1/8· OSTI ID:22869477

Trakhtenbrot, Benny; Cicone, Claudia ^[1]; Lira, Paulina ^[2]; Netzer, Hagai ^[3]; Maiolino, Roberto ^[4]; Shemmer, Ohad ^[5]

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1. Institute for Astronomy, Department of Physics, ETH Zurich, Wolfgang-Pauli-Strasse 27, CH-8093 Zurich (Switzerland)
2. Departamento de Astronomia, Universidad de Chile, Camino del Observatorio 1515, Santiago (Chile)
3. School of Physics and Astronomy and the Wise Observatory, The Raymond and Beverly Sackler Faculty of Exact Sciences, Tel-Aviv University, Tel-Aviv 69978 (Israel)
4. Cavendish Laboratory, University of Cambridge, 19 J. J. Thomson Avenue, Cambridge CB3 0HE (United Kingdom)
5. Department of Physics, University of North Texas, Denton, TX 76203 (United States)

We present new ALMA band-7 data for a sample of six luminous quasars at z≃4.8, powered by fast-growing supermassive black holes (SMBHs) with rather uniform properties: the typical accretion rates and black hole masses are L/L{sub Edd}≃0.7 and M{sub BH}≃10{sup 9} M{sub ⊙}. Our sample consists of three “FIR-bright” sources, which were individually detected in previous Herschel/SPIRE observations, with star formation rates of SFR>1000 M{sub ⊙} yr{sup −1}, and three “FIR-faint” sources for which Herschel stacking analysis implies a typical SFR of ∼400 M{sub ⊙} yr{sup −1}. The dusty interstellar medium in the hosts of all six quasars is clearly detected in the ALMA data and resolved on scales of ∼2 kpc, in both continuum (λ{sub rest}∼150 μm) and [C II] λ157.74 μm line emission. The continuum emission is in good agreement with the expectations from the Herschel data, confirming the intense SF activity in the quasar hosts. Importantly, we detect companion sub-millimeter galaxies (SMGs) for three sources—one FIR-bright and two FIR-faint, separated by ∼14--45 kpc and <450 km s{sup −1} from the quasar hosts. The [C II]-based dynamical mass estimates for the interacting SMGs are within a factor of ∼3 of the quasar hosts’ masses, while the continuum emission implies SFR{sub quasar}∼(2--11)×SFR{sub SMG}. Our ALMA data therefore clearly support the idea that major mergers are important drivers for rapid early SMBH growth. However, the fact that not all high-SFR quasar hosts are accompanied by interacting SMGs and the gas kinematics as observed by ALMA suggest that other processes may be fueling these systems. Our analysis thus demonstrates the diversity of host galaxy properties and gas accretion mechanisms associated with early and rapid SMBH growth.

• OSTI ID: 22869477
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 1 Vol. 836; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
BLACK HOLES
EMISSION
GALAXIES
MASS
QUASARS
RED SHIFT
STAR EVOLUTION
STARS