Rare encounters between cosmic heavyweights
Deep learning used to find signs were present before deadly Greenland landslide

Date:
August 27, 2020
Source:
W. M. Keck Observatory
Summary:
Astronomers have discovered three pairs of merging galaxies. Each
of the galaxies contain a supermassive black hole that's feasting
on material surrounding it, creating a phenomenon called a
quasar. These luminous dual quasars are rare; only about 0.3%
of all known quasars have two supermassive black holes that are
on a collision course with each other.



FULL STORY ==========================================================================
A cosmic dance between two merging galaxies, each one containing a
supermassive black hole that's rapidly feeding on so much material it
creates a phenomenon known as a quasar, is a rare find.


========================================================================== Astronomers have discovered several pairs of such merging galaxies, or
luminous "dual" quasars, using three Maunakea Observatories in Hawaii --
Subaru Telescope, W. M. Keck Observatory, and Gemini Observatory.

These dual quasars are so rare, a research team led by the Kavli Institute
for the Physics and Mathematics of the Universe at the University of
Tokyo estimates only 0.3% of all known quasars have two supermassive
black holes that are on a collision course with each other.

The study is published in the August 26, 2020 issue of the Astrophysical Journal.

"In spite of their rarity, they represent an important stage in the
evolution of galaxies, where the central giant is awakened, gaining mass,
and potentially impacting the growth of its host galaxy," said Shenli
Tang, a graduate student at the University of Tokyo and co-author of
the study.

Quasars are one of the most luminous, energetic objects known in the
universe, powered by supermassive black holes that are millions to
billions times more massive than our Sun. As material swirls around a
black hole at the center of a galaxy, it is heated to high temperatures, releasing so much light that the quasar can outshine its host galaxy.

This makes a merging pair of galaxies with quasar activity hard to detect;
it is difficult to separate the light from the two quasars because
they are in such close proximity to each other. Also, observing a wide
enough area of the sky to catch these rare events in sufficient numbers
is a challenge.

To overcome these obstacles, the team took advantage of a sensitive
wide survey of the sky using the Hyper Suprime-Cam (HSC) camera on the
Subaru Telescope.

"To make our job easier, we started by looking at the 34,476 known
quasars from the Sloan Digital Sky Survey with HSC imaging to identify
those having two (or more) distinct centers," said lead author John
Silverman of the Kavli Institute for the Physics and Mathematics of the Universe. "Honestly, we didn't start out looking for dual quasars. We
were examining images of these luminous quasars to determine which type
of galaxies they preferred to reside in when we started to see cases
with two optical sources in their centers where we only expected one."
The team identified 421 promising cases. However, there was still
the chance many of these were not bona-fide dual quasars but rather
chance projections such as starlight from our own galaxy. Confirmation
required detailed analysis of the light from the candidates to search
for definitive signs of two distinct quasars.

Using Keck Observatory's Low Resolution Imaging Spectrometer (LRIS)
and Gemini Observatory's Near-Infrared Integral Field Spectrometer,
Silverman and his team identified three dual quasars, two of which were previously unknown. Each object in the pair showed the signature of gas
moving at thousands of kilometers per second under the influence of a supermassive black hole.

The newly-discovered dual quasars demonstrate the promise of wide-area
imaging combined with high-resolution spectroscopic observations to
reveal these elusive objects, which are key to better understanding the
growth of galaxies and their supermassive black holes.


========================================================================== Story Source: Materials provided by W._M._Keck_Observatory. Note:
Content may be edited for style and length.


========================================================================== Journal Reference:
1. John D. Silverman, Shenli Tang, Khee-Gan Lee, Tilman Hartwig, Andy
Goulding, Michael A. Strauss, Malte Schramm, Xuheng Ding, Rogemar A.

Riffel, Seiji Fujimoto, Chiaki Hikage, Masatoshi Imanishi,
Kazushi Iwasawa, Knud Jahnke, Issha Kayo, Nobunari Kashikawa,
Toshihiro Kawaguchi, Kotaro Kohno, Wentao Luo, Yoshiki Matsuoka,
Yuichi Matsuda, Tohru Nagao, Masamune Oguri, Yoshiaki Ono, Masafusa
Onoue, Masami Ouchi, Kazuhiro Shimasaku, Hyewon Suh, Nao Suzuki,
Yoshiaki Taniguchi, Yoshiki Toba, Yoshihiro Ueda, Naoki Yasuda. Dual
Supermassive Black Holes at Close Separation Revealed by the Hyper
Suprime-Cam Subaru Strategic Program. The Astrophysical Journal,
2020; 899 (2): 154 DOI: 10.3847/1538- 4357/aba4a3 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/08/200827102120.htm

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