RIT: When Radio Galaxies Collide, Supermassive Black Holes Form Tight Pairs

[bystander]

When Radio Galaxies Collide, Supermassive Black Holes Form Tightly Bound Pairs
Rochester Institute of Technology | 2017 Sep 18

[img3="NGC 7674, seen just above the center, is a luminous spiral galaxy with a powerful active nucleus. Credit: NASA, ESA, Hubble Heritage (STScI/AURA)"]https://cdn.spacetelescope.org/archives ... 0810bp.jpg[/img3][hr][/hr]

A study using multiple radio telescopes confirms that supermassive black holes found in the centers of galaxies can form gravitationally bound pairs when galaxies merge.

The paper published in the Sept. 18 issue of Nature Astronomy sheds light on a class of black holes having a mass upwards of one million times the mass of the sun. Supermassive black holes are expected to form tightly bound pairs following the merger of two galaxies.

“The dual black hole we found has the smallest separation of any so far detected through direct imaging,” said David Merritt, professor of physics at Rochester Institute of Technology, a co-author on the paper.

The supermassive black holes are located in the spiral galaxy NGC 7674, approximately 400 million light years from earth, and are separated by a distance less than one light year. The study was led by Preeti Kharb, from the National Center for Radio Astrophysics at the Tata Institute of Fundamental Research and co-authored by Dharam Vir Lal, also at the National Center for Radio Astrophysics, and Merritt at RIT.

“The combined mass of the two black holes is roughly 40 million times the mass of the Sun, and the orbital period of the binary is about 100,000 years,” Merritt said. ...

Discovery of the Closest Binary Supermassive Black Hole System in the Galaxy NGC 7674
Tata Institute of Fundamental Research | 2017 Sep 19

A Candidate Sub-Parsec Binary Black Hole in the Seyfert Galaxy NGC 7674 - P. Kharb, D. V. Lal, D. Merritt

• Nature Astronomy (online 18 Sep 2017) DOI: 10.1038/s41550-017-0256-4
  arXiv.org > astro-ph > arXiv:1709.06258 > 19 Sep 2017

[MargaritaMc]

The RIT link returned a page not found link at the Rochester site, tho this URL is the one they give on their Twitter announcement. (I've reported the broken link to them.)

The press release is available at phys.org
https://phys.org/news/2017-09-radio-gal ... black.html

[MargaritaMc]

Sky & Telescope article
http://www.skyandtelescope.com/astronom ... tango-yet/

[Ann]

NGC 7674 looks very well-ordered. It doesn't look as if it's been through a collision and a merger. Perhaps it merged with a satellite galaxy very long ago, and the spiral structure bounced back somehow (or never got very disturbed in the first place).

Ann

[MargaritaMc]

The paper is now up on arXiv

A candidate sub-parsec binary black hole in the Seyfert galaxy NGC 7674
Preeti Kharb (NCRA-TIFR), Dharam Vir Lal (NCRA-TIFR), David Merritt (RIT)
https://arxiv.org/abs/1709.06258
Abstract:
[...]
The existence of binary supermassive black holes (SBHs) is predicted by models of hierarchical galaxy formation. To date, only a single binary SBH has been imaged, at a projected separation of 7.3 parsecs. Here we report the detection of a candidate dual SBH with projected separation of 0.35 pc in the gas-rich interacting spiral galaxy NGC 7674 (Mrk 533). This peculiar Seyfert galaxy possesses a ∼0.7 kpc Z-shaped radio jet; the leading model for the formation of such sources postulates the presence of an uncoalesced binary SBH created during the infall of a satellite galaxy. [...]