From Gemini Observatory: “Elusive Intermediate Mass Black Hole Revealed by Cosmic Belch”


Gemini Observatory
From Gemini Observatory

July 9, 2018

Gemini South GMOS spectrum (black line) of the nuclear region of the host galaxy of the observed off-center tidal disruption event, believed to be caused by an intermediate mass black hole. The best-fit model of the spectrum is shown in green, with the contribution from the stars alone indicated in red. The gray areas mark regions where the spectrum was affected by atmospheric absorption and the GMOS CCD gap. This Gemini spectrum was used to extract the stellar population properties and kinematics of the galaxy in which this unusual event occurred.

Gemini Observatory GMOS on Gemini South

The frustrating search for intermediate mass black holes is advancing thanks to Gemini observations of a “belch” which escaped when a black hole devoured a star. The black hole powering the blast weighed in at a few tens of thousand solar masses and is quite possibly a missing link between supermassive and stellar mass black holes.

After 10 years of searching, an international team of astronomers used Gemini South, and space-based telescopes, to probe a luminous X-ray outburst unlike any seen before. The outburst was unusual because it appears to be the result of a “tidal disruption event” (TDE), in which a massive black hole slurps up an entire star, but this particular event did not occur within the center of a galaxy, where the most massive black holes reside.

In their investigation, the researchers measured the mass of the black hole that powered the outburst and found it was a likely Intermediate Mass Black Hole (IMBH) candidate. IMBHs are black holes with masses between that of supermassive black holes (millions of solar masses) and stellar mass black holes (a few to tens of solar masses). Astronomers continue to argue if IMBHs exist and therefore this finding will undoubtedly undergo intense scrutiny.

The paper, “A luminous X-ray outburst from an intermediate-mass black hole in an off-centre star cluster” is accepted in Nature Astronomy.

“This is a dramatic demonstration that detecting IMBHs through X-ray flares produced by tidal disruption events in star clusters is extremely effective in looking for IMBHs,” points out Rodrigo Carrasco, an astronomer at Gemini South and a co-author of the paper.

Dacheng Lin (University of New Hampshire) led the research and adds that previous strong TDE candidates were found in the centers of galaxies. “However, here we discovered a luminous X-ray outburst from a massive star cluster about 40,000 light years from the center of a large lenticular galaxy where it can be studied in relative isolation.” The host galaxy is about 780 million light years away and goes by the designation 6dFGS gJ215022.2-055059.

These circumstances allowed the team to study the X-ray flare emission as the black hole devoured a star far from the center of a galaxy and away from dense stellar regions where these events are generally found. “We had a nice clean laboratory in which to study this event,” said Carrasco. “That’s what allowed us to measure this black hole so confidently and conclude that this is very likely an IMBH revealing its secrets.”

The team used the Gemini Multi-Object Spectrograph on the Gemini South telescope in Chile with data obtained in late 2016, to determine the distance of the host galaxy and the off-centered star cluster.

IMBHs are significantly more massive than stellar black holes – produced when massive stars die – but much less massive than supermassive black holes – which are found in the centers of most massive galaxies. The existence of IMBHs continues as an ongoing debate among astronomers since they are so difficult to find and measure.

See the full article here .

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Gemini/North telescope at Maunakea, Hawaii, USA,4,207 m (13,802 ft) above sea level

Gemini South telescope, Cerro Tololo Inter-American Observatory (CTIO) campus near La Serena, Chile, at an altitude of 7200 feet


Gemini’s mission is to advance our knowledge of the Universe by providing the international Gemini Community with forefront access to the entire sky.

The Gemini Observatory is an international collaboration with two identical 8-meter telescopes. The Frederick C. Gillett Gemini Telescope is located on Mauna Kea, Hawai’i (Gemini North) and the other telescope on Cerro Pachón in central Chile (Gemini South); together the twin telescopes provide full coverage over both hemispheres of the sky. The telescopes incorporate technologies that allow large, relatively thin mirrors, under active control, to collect and focus both visible and infrared radiation from space.

The Gemini Observatory provides the astronomical communities in six partner countries with state-of-the-art astronomical facilities that allocate observing time in proportion to each country’s contribution. In addition to financial support, each country also contributes significant scientific and technical resources. The national research agencies that form the Gemini partnership include: the US National Science Foundation (NSF), the Canadian National Research Council (NRC), the Chilean Comisión Nacional de Investigación Cientifica y Tecnológica (CONICYT), the Australian Research Council (ARC), the Argentinean Ministerio de Ciencia, Tecnología e Innovación Productiva, and the Brazilian Ministério da Ciência, Tecnologia e Inovação. The observatory is managed by the Association of Universities for Research in Astronomy, Inc. (AURA) under a cooperative agreement with the NSF. The NSF also serves as the executive agency for the international partnership.