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Swift Logo, Credit: NASA EPO, Sonoma State University, Aurore Simonnet WASHINGTON -- Astronomers using data from an ongoing survey by NASA's Swift satellite discussed findings on the active black holes in nearby galaxies during a news conference on May 26.

Swift's Hard X-ray Survey detects feeding supermassive black holes in the hearts of nearby galaxies. The study confirms theoretical ideas that black holes "light up" when galaxies collide.

› NASA press release

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Briefing Speakers

› Neil Gehrels, Swift Principal Investigator, Goddard Space Flight Center, Greenbelt, Md.
› Michael Koss, graduate student, University of Maryland, College Park, Md.
› Meg Urry, professor, Yale University, New Haven, Conn.
› Joel Bregman, professor, University of Michigan, Ann Arbor, Mich.

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Images and Multimedia in Support of the News Conference

Presenter: Neil Gehrels, Swift Principal Investigator, NASA's Goddard Space Flight Center

	Figure 1: Title Slide: The Swift BAT Hard X-ray Survey, Neil Gehrels, PI Credit: NASA/Swift/Neil Gehrels, GSFC › View larger
	Figure 2: The Swift BAT Hard X-ray Telescope: The Swift Burst Alert Telescope (BAT) finds supermassive black holes in active galaxies. The Swift BAT is not like a normal telescope. It has a very wide field of view (about 1/10th of the sky) and observes in energetic (“hard”) X-rays. Credit: NASA/Swift/Neil Gehrels, GSFC › View larger
	Figure 3: Hard X-rays vs. Visible Light: The black hole’s optical emission is blocked by gas and dust but its high-energy X-rays are not. X-rays directly detect the energetic black hole that can be hidden in other bands. Credit: NASA/Swift/Neil Gehrels, GSFC › View larger
	Figure 4: BAT Hard X-ray Survey Sources: The survey is limited to the nearby universe (out to about 650 million light-years, or redshift <0.05). Future X-ray satellites, such as NuSTAR, launching in 2012, will enhance our understanding of how active galaxies are powered at greater distances. Credit: NASA/Swift/Neil Gehrels, GSFC › View larger

› Presenter's slides in PDF format (205 KB)

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Presenter: Michael Koss, graduate student, University of Maryland, College Park, Md.

	Figure 1: Title Slide: Triggering Active Galaxies: Swift Finds the Smoking Gun, Michael Koss, Univ. of Maryland Credit: NASA/Swift/Michael Koss (Univ. of Maryland) › View larger
	Figure 2: Active Galaxies in the Swift BAT Survey: • Swift has detected 260 active galactic nuclei (AGN) in the BAT Hard X-ray Survey. • For the first time, we see about 25% of AGN in the process of merging with other galaxies. •This is very different from the approximately 2% of AGN found in merging galaxies by other surveys. • Approximately 60% of the active galaxies will undergo a galaxy merger in the next billion years. This indicates that mergers play an important role in powering AGN. Credit: NASA/Swift/Michael Koss (Univ. of Maryland) and NOAO/SDSS › View larger
	Figure 3: Supermassive Black Holes: • Most big galaxies host big black holes (millions of times the sun's mass) • About 1% emit enormous amounts of energy (as much as 10 billion suns) • These are called active galactic nuclei (AGN). • Why is this fraction so small? What makes them “light up” anyhow? Credit: NASA/Swift/Michael Koss (Univ. of Maryland) › View larger Image Caption: Active galaxies collide, feeding matter to the central black holes that power quasars Image Credit: Don Dixon › View image larger
This simulation follows the collision of two spiral galaxies that harbor giant black holes. The merger stirs up gas in both galaxies. Infalling gas "switches on" the black holes and creates bright active galactic nuclei (AGN). Video Credit: Volker Springel and Tiziana Di Matteo (Max Planck Institute for Astrophysics), Lars Hernquist (Harvard Univ.) › Download Video
	Figure 4: How Do We Know a Merger is Occurring?: • Shape: Severe distortion of the galaxy shapes as they tear each other apart and feed the black hole. • Proximity: These galaxies will merge in an astronomically short time (less than 500 million years). Credit: NASA/Swift/Michael Koss (Univ. of Maryland) and NOAO/SDSS › View larger
	Figure 5: Some merging AGN found by Swift: The optical counterparts of many active galactic nuclei (circled) detected by the Swift BAT Hard X-ray Survey clearly show galaxies in the process of merging. These images, taken with the 2.1-meter telescope at Kitt Peak National Observatory in Arizona, show galaxy shapes that are either physically intertwined or distorted by the gravity of nearby neighbors. These AGN were known prior to the Swift survey, but Swift has found dozens of new ones in more distant galaxies. Credit: NASA/Swift/NOAO/Michael Koss and Richard Mushotzky (Univ. of Maryland) › View image larger › View image larger unannotated
	Figure 6: Conclusions: • The Swift BAT has opened up a fundamentally new way of finding feeding supermassiveblack holes. Hard X-rays penetrate gas and dust to directly image the AGN. • About 25% of AGN are in the process of merging. • This is a much higher percentage than found by other surveys. • The finding indicates that a majority (60%) of active galaxies will completely merge in the next billion years. Mergers play an important role in powering AGN. Credit: NASA/Swift/Michael Koss (Univ. of Maryland) › View larger

› Presenter's slides in PDF format (491 KB)

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Related Links

› Galaxy Collisions Awaken Dormant Black Holes