Dwarf galaxy has ‘bizarre’ Supermassive Black Hole

Two Australian astronomers are part of the international team who found a supermassive black hole inside the smallest known galaxy.

A partnership between the Australian Astronomical Observatory and Macquarie University has supported the key roles played by Dr Richard McDermid and Dr Lee Spitler in making the discovery, led by University of Utah astronomer Anil Seth.

Seth, McDermid and Spitler’s ‘star’ team discovered that an ultracompact dwarf galaxy known as M60-UCD1 harbors a supermassive black hole – and it’s the smallest galaxy known to contain such a massive light-sucking object.

“This object is bizarre – it is the smallest thing we’ve ever found to harbor such a large black hole,” said Spitler. “Even the Milky Way, which is 500 times larger than M60-UCD1, has a smaller black hole.“

“The size of a supermassive black hole usually relates to the size of the galaxy it lives in,” says McDermid, “so if small, compact galaxies like M60-UCD1 formed like other galaxies, we’d expect them to have fairly small black holes at their centres.

“Instead, in M60-UCD1 we found a supermassive black hole that is way out of proportion – about 1500 times larger than was expected.”

“What we think happened was that M60-UCD1 was once a normal galaxy, probably a little bigger than the Milky Way.” said Spitler “The old M60-UCD1 likely had a head-on collision with another, much larger galaxy called M60.

“All that is left of M60-UCD1 is just its core – the rest of it was ripped apart. So we think we found the dense stellar core of a destroyed galaxy.”

Gemini Observatory with laser guide star adaptive optics in action

As part of the international science team, the two joint Macquarie-AAO staff members contributed access to the Gemini North Observatory – an 8 metre telescope in Hawaii funded by Australia as part of an international partnership.

“Even with this huge telescope, it's a difficult measurement to make,” says McDermid. “To estimate the mass of the supermassive black hole, we required Gemini’s laser guide star adaptive optics system to correct the light from M60-UCD1 for distortions caused by Earth’s atmosphere – kind of like removing the ‘twinkle’ from the stars.”

The Hubble Space Telescope was also used in the discovery.

“There are a large number of ultracompact dwarf galaxies in the universe,” says Anil Seth, lead author of the international study of the dwarf galaxy published in the journal Nature. “Together they may contain as many supermassive black holes as there are at the centers of normal galaxies.” This would double the number of supermassive black holes in the Universe.

The study – conducted by Seth, McDermid, Spitler and 11 other astronomers – was funded by the US National Science Foundation, the German Research Foundation and the international Gemini Telescope partnership, which includes the NSF and scientific agencies in Canada, Chile, Australia, Brazil and Argentina.


"A supermassive black hole in an ultra-compact dwarf galaxy", Nature, Vol 513, September 2014, Anil C. Seth, Remco van den Bosch, Steffen Mieske, Holger Baumgardt, Mark den Brok, Jay Strader, Nadine Neumayer, Igor Chilingarian, Michael Hilker, Richard McDermid, Lee Spitler, Jean Brodie, Matthias J. Frank & Jonelle L.Walsh, doi:10.1038/nature13762 

Images and Movies

High Resolution: M60-UCD1_Labels300dpi.jpg (labels); M60-UCD1_NoLabels300dpi.jpg (no labels)

Caption: This Hubble Space telescope image shows the gargantuan galaxy M60 in the center, and the ultracompact dwarf galaxy M60-UCD1 below it and to the right, and also enlarged as an inset. A new international study led by University of Utah astronomer Anil Seth and published in the journal Nature found that M60-UCD1 is the smallest known galaxy with a supermassive black hole at its center, suggesting the dwarf galaxy originally was much larger but was stripped of its outer layers by gravity from galaxy M60 over billions of years. M60’s gravity also is pulling galaxy NGC4647, upper right, and the two eventually will collide.

Credit: NASA/Space Telescope Science Institute/European Space Agency.


High Resolution: GeminiNorthLGSmoonlight300dpi.jpg

Caption: The Gemini North observatory on Hawaii’s Mauna Kea shoots a laser beam into the night sky to create an “artificial star” that astronomers use to adjust images made by the telescope to remove the blurring effects of Earth’s atmosphere. The Gemini North telescope was used in a new University of Utah-led study that discovered the smallest galaxy yet known to harbor a supermassive black hole.

Credit: Gemini Observatory/Association of Universities for Research in Astronomy.


Computer simulation of galaxy M60’s gravity stripping M60-UCD1’s outer parts: http://vimeo.com/105370891

Caption: The video simulation shows how this small galaxy, named M60-UCD1, was formed from a larger, normal galaxy. The video begins with a background image made by the Hubble Space Telescope, with the huge elliptical galaxy M60 in the center, galaxy NGC4647 in the upper right and MC60-UCD as a small whitish spot lower right. As the video begins, a normal galaxy (yellow and red) orbits M60. During an estimated 500 million years, M60’s gravity strips stars (red material) from the orbiting galaxy, leaving as a remnant the ultracompact dwarf galaxy now known as M60-UCD1. The end of the video zooms in on the Hubble Space Telescope close-up image of M60-UCD1, which today continues to orbit M60.

Credit: Holger Baumgardt, University of Queensland.


Science Contacts

Dr. Richard McDermid, Macquarie University, Australia and Australian Astronomical Observatory, Sydney (UTC + 10)
Phone: +61 2 9850 4476
Mobile: +61 2 481 453 727
Email: richard.mcdermid@mq.edu.au

Dr. Lee Spitler, Macquarie University, Australia and Australian Astronomical Observatory, Sydney
Phone: +61 2 9850 4161
Email: lee.spitler@mq.edu.au

A/Prof. Andrew Hopkins, Australia and Australian Astronomical Observatory, Sydney
Phone: +61 2 9372 4849
Email: andrew.hopkins@aao.gov.au