Galactic Cannibalism - late lunch for hungry black hole?
5 Dec 2014: An international team of scientists including Liverpool John Moores University's Astrophysics Research Institute and the NASA Herschel Science Center (NHSC) at the California Institute of Technology, have used a suite of NASA and European Space Agency satellites, to study a galactic train wreck 50 million light years from Earth, dubbed Arp94, in which two galaxies are colliding and ripping one another apart via their gravitational forces. The research, published in the Astrophysical Journal, shows that dumping hydrogen gas onto a galaxy switches off its ability to form stars - a phenomenon known as quenching.
The new findings illustrate a new dimension to galaxy evolution and come courtesy of the European Space Agency's s Herschel space observatory, in which NASA plays a key role, and NASA's Spitzer and Hubble space telescopes.
Galactic 'cannibalism' is thought to play an important role in driving the evolution of galaxies through cosmic time and is particularly violent in the early Universe, when gas was plentiful and galaxy collisions were common.
A key question in galaxy studies is to understand the evolutionary path between gas-rich spiral galaxies like our own actively star-forming Milky Way galaxy and elliptical galaxies that appear to be red, dead and devoid of active star formation
The team used data from the space telescopes to record the fate of a stream of cosmic debris pouring onto one of system’s galaxies - NGC3226 – whose green colour suggested it is a possible missing link or transition galaxy between blue star-forming spiral galaxies and red, dead ellipticals.
Professor Carole Mundell from the LJMU Astrophysics Research Institute - one of the lead authors on the new study - was the first to discover the vast plumes of cold hydrogen gas stretching over 326,000 light years across the galaxy system, using a network of powerful radio telescopes in New Mexico - the Very Large Array – in 1995.
"Our new study shows that there are tiny clumps or clusters of stars forming far out in intergalactic space in the plume of cold gas that has been ripped from the largest galaxy,” she explained.
The team’s new study shows that the in-falling cold, atomic hydrogen gas settled into a disk of warm molecular hydrogen around the centre of the galaxy, some of which may ultimately feed the central black hole that lies at the heart of the galaxy, but which is not yet cool enough to condense to form new stars.
Mundell continued, "For the first time, we show a direct connection between the tidal debris and the heart of the companion galaxy, which has been caught in the act of consuming part of its neighbour."
Dr Phil Appleton, Head of NASA's Herschel Science Center at the California Institute of Technology, Pasadena, and lead author on the new study said:
"We have exploited the fantastic potential of big data archives from NASA’s Hubble, Spitzer and ESA’s Herschel observatory to pull together a picture of an elliptical galaxy that has undergone huge changes in its recent past due to violent collisions with its neighbour. These changes are modifying not only its structure and color, but also the condition of the gas that resides in it, making it hard, at the moment, for the galaxy to form many stars.”
By studying a local merging galaxy system in exquisite detail, the team say they have identified an example of a new class of nearby galaxies that are experiencing unexpectedly rapid evolution despite residing in the present-day, less violent, Universe.
Notes to editors
The preprint of the accepted article is now available at: http://arxiv.org/abs/1410.7347
Interviews:
Professor Mundell, head of Liverpool John Moores University's Gamma Ray Burst team at the Astrophysics Research Institute is available for interview on these contact details - 0797 477 9923 or C.Mundell@ljmu.ac.uk
Dr Phil Appleton, Head of NASA's Herschel Science Center at the California Institute of Technology, Pasadena, apple@ipac.caltech.edu
Herschel is a European Space Agency mission, with science instruments provided by consortia of European institutes and with important participation by NASA. While the observatory stopped making science observations in April 2013, after running out of liquid coolant, as expected, scientists continue to analyze its data. NASA's Herschel Project Office is based at NASA's Jet Propulsion Laboratory, Pasadena, California. JPL contributed mission-enabling technology for two of Herschel's three science instruments. The NASA Herschel Science Center, part of the Infrared Processing and Analysis Center at Caltech, supports the U.S. astronomical community. Caltech manages JPL for NASA.
JPL manages the Spitzer Space Telescope mission for NASA's Science Mission Directorate, Washington. Science operations are conducted at the Spitzer Science Center at Caltech. Spacecraft operations are based at Lockheed Martin Space Systems Company, Littleton, Colorado. Data are archived at the Infrared Science Archive housed at the Infrared Processing and Analysis Center at Caltech. Caltech manages JPL for NASA.
The Hubble Space Telescope is a project of international cooperation between NASA and the European Space Agency. NASA's Goddard Space Flight Center in Greenbelt, Maryland, manages the telescope. The Space Telescope Science Institute (STScI) in Baltimore conducts Hubble science operations. STScI is operated for NASA by the Association of Universities for Research in Astronomy, Inc., in Washington.
Fore more information about NASA's role in Herschel, visit:
For more information about Spitzer, visit:
For more information about Hubble, visit:
Image for story: http://web.ipac.caltech.edu/staff/sscnews/temp/ngc3226/
Image description:
A Flood of Gas
A new feature in the evolution of galaxies has been captured in this image of galactic interactions. The two galaxies seen here -- NGC 3226 at the top, NGC 3227 at the bottom -- are awash in the remains of a departed third galaxy, cannibalized by the gravity of the surviving galaxies. The surge of warm gas flowing into NGC 3226, seen as a blue filament, appears to be shutting down this galaxy's star formation, disrupting the cool gas needed to make fresh stars.
The findings come courtesy of the European Space Agency's Herschel space observatory, in which NASA played a key role, and NASA's Spitzer and Hubble space telescopes.
Adding material to galaxies often rejuvenates them, triggering new rounds of star birth as gas and dust gel together. Yet data from the three telescopes all indicate that NGC 3226 has a very low rate of star formation.
In this instance, material falling into NGC 3226 is heating up as it collides with other galactic gas and dust, quenching star formation instead of fueling it. As this warm gas chills out in the future, though, NGC 3226 should get a second wind in its stalled-out production of new stars.
The gray scale in this image shows optical starlight captured by the MegaCam instrument at the Canada France Hawaii Telescope (CFHT) telescope on Mauna Kea in Hawaii, and reveals loops of stars flung about by the galactic cannibalism. The blue color represents cool hydrogen gas seen in radio waves by the Very Large Array near Socorro, New Mexico. The big plume of gas above NGC 3226 is being drawn into the galaxy by its gravity. The red color shows infrared light emissions, captured by Spitzer, from warm gas and dust at the tip of the plume's infalling stream of material into NGC 3226, as well as from features within NGC 3227.
Other Spitzer observations reveal a disk of warm molecular gas at the core of NGC 3226, fed by the plume. Herschel observations, not shown in the image, were used to create a galactic star-formation model, which confirms NGC 3226's very low star-formation rate.
The interacting galaxies are located 49 million light-years away in the constellation Leo.
Visible starlight at wavelengths of 550 to 700 nanometers is shown in gray scale. The infrared glow of dust at 8 microns, as seen by Spitzer, is displayed in red, while the radio glow of hydrogen gas at 21 centimeters, from the VLA, is shown in blue.
Photo Credit: NASA/CFHT/NRAO/JPL-Caltech/Duc/Cuillandre/Mundell
