Title: Tests of Gravity Theories Using Supermassive Black Holes

Abstract

Scalar-tensor theories of gravity generally violate the strong equivalence principle, namely that compact objects have a suppressed coupling to the scalar force, which causes them to fall slower. A black hole is the extreme example where such a coupling vanishes, i.e., black holes have no scalar hair. We explore observational scenarios for detecting strong equivalence principle violation, focusing on galileon gravity as an example. For galaxies infalling toward galaxy clusters, the supermassive black hole can be offset from the galaxy center away from the direction of the cluster. Well-resolved images of galaxies around nearby clusters can therefore be used to identify the displaced black hole via the star cluster bound to it. We show that this signal is accessible with imaging surveys, both ongoing ones such as the Dark Energy Survey and future ground- and space-based surveys. Already, the observation of the central black hole in M 87 places new constraints on the galileon parameters, which we present here. $${\mathcal O}(1)$$ matter couplings are disfavored for a large region of the parameter space. Lastly, we also find a novel phenomenon whereby the black hole can escape the galaxy completely in less than one billion years.

Authors:

Sakstein, Jeremy ^[1]; Jain, Bhuvnesh ^[1]; Heyl, Jeremy S.  ^[2];

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• Search DOE PAGES for ORCID "0000-0001-9739-367X"

Hui, Lam ^[3]

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+ Show Author Affiliations

1. Univ. of Pennsylvania, Philadelphia, PA (United States). Dept. of Physics and Astronomy, Center for Particle Cosmology
2. Univ. of British Columbia, Vancouver, BC (Canada). Dept. of Physics and Astronomy
3. Columbia Univ., New York, NY (United States). Dept. of Physics, Center for Theoretical Physic

Publication Date:

Thu Jul 20 00:00:00 EDT 2017

Research Org.:

Univ. of Pennsylvania, Philadelphia, PA (United States); Columbia Univ., New York, NY (United States)

Sponsoring Org.:

USDOE Office of Science (SC); Natural Sciences and Engineering Research Council of Canada (NSERC); National Aeronautics and Space Administration (NASA)

OSTI Identifier:

1537200

Grant/Contract Number:  

SC0007901; SC0011941; NXX16AB27G

Resource Type:

Accepted Manuscript

Journal Name:

The Astrophysical Journal. Letters (Online)

Additional Journal Information:

Journal Name: The Astrophysical Journal. Letters (Online); Journal Volume: 844; Journal Issue: 1; Journal ID: ISSN 2041-8213

Publisher:

Institute of Physics (IOP)

Country of Publication:

United States

Language:

English

Subject:

79 ASTRONOMY AND ASTROPHYSICS; Astronomy & Astrophysics; black hole physics; dark energy; gravitation