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Title: Toward Astrometric Constraints on a Supermassive Black Hole Binary in the Early-type Galaxy NGC 4472
Abstract The merger of two galaxies, each hosting a supermassive black hole (SMBH) of mass 10 6 M ⊙ or more, could yield a bound SMBH binary. For the early-type galaxy NGC 4472, we study how astrometry with a next-generation Very Large Array could be used to monitor the reflex motion of the primary SMBH of mass M pri , as it is tugged on by the secondary SMBH of mass M sec . Casting the orbit of the putative SMBH binary in terms of its period P , semimajor axis a bin , and mass ratio q = M sec / M pri ≤ 1 , we find the following: (1) Orbits with fiducial periods of P = 4 yr and 40 yr could be spatially resolved and monitored. (2) For a 95% accuracy of 2 μ as per monitoring epoch, subparsec values of a bin could be accessed over a range of mass ratios notionally encompassing major q > 1 4 and minor q < 1 4 galaxy mergers. (3) If no reflex motion is detected for M pri after 1 (10) yr of monitoring, an SMBH binary with period P = 4 (40) yr and mass ratio q > 0.01 (0.003) could be excluded. This would suggest no present-day evidence for a past major merger like that recently simulated, where scouring by a q ∼ 1 SMBH binary formed a stellar core with kinematic traits like those of NGC 4472. (4) Astrometric monitoring could independently check the upper limits on q from searches for continuous gravitational waves from NGC 4472.  more » « less
Award ID(s):
2020265
PAR ID:
10405775
Author(s) / Creator(s):
;
Date Published:
Journal Name:
The Astrophysical Journal
Volume:
931
Issue:
1
ISSN:
0004-637X
Page Range / eLocation ID:
12
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
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