Abell 644 and SDSS J1021+131: How Often do Giant Black Holes Become Hyperactive?

Abell 644 and DSS J1021+1312

Credit X-ray: NASA/CXC/Univ of Washington/D.Haggard et al, Optical: SDSS
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This two-panel graphic contains two composite images of galaxies used in a recent study of supermassive black holes. In each of the galaxies, data from NASA's Chandra X-ray Observatory are blue, and optical data from the Sloan Digital Sky survey are shown in red, yellow and white. The galaxy on the left, Abell 644, is in the center of a galaxy cluster that lies about 1.1 billion light years from Earth. On the right is an isolated, or "field," galaxy named SDSS J1021+1312, which is located about 900 million light years away. At the center of both of these galaxies is a growing supermassive black hole, called an active galactic nucleus (AGN) by astronomers, which is pulling in large quantities of gas.

A newly published study from Chandra tells scientists how often the biggest black holes in field galaxies like SDSS J1021+1312 have been active over the last few billion years. This has important implications for how environment affects black hole growth. The scientists found that only about one percent of field galaxies with masses similar to the Milky Way contain supermassive black holes in their most active phase. They also found that the most massive galaxies are the most likely to host these AGN, and that there is a gradual decline in the AGN fraction with cosmic time. Finally, the AGN fraction for field galaxies was found to be indistinguishable from that for galaxies in dense clusters, like Abell 644.

This study involves a survey called the Chandra Multiwavelength Project, or ChaMP, which covers 30 square degrees on the sky, the largest area covered of any Chandra survey to date. Combining Chandra's X-ray images with optical images from the Sloan Digital Sky Survey, about 100,000 galaxies were analyzed. Out of those, about 1,600 were bright in X-ray light, signaling possible AGN activity.

Fast Facts for Abell 644:

Scale: Image is 13.2 arcmin across. (36.7 million light years across)
Category: Groups & Clusters of Galaxies Quasars & Active Galaxies
Coordinates: (J2000) RA 08h 17m 25.6s | Dec -7° 30' 45''
Constellation: Hydra
Observation Dates: 3/26/2001
Observation Time: 8 hours 20 min
Obs. IDs: 2211
Color Code: X-ray (Blue), Optical (Red, Yellow, White)
Instrument: ACIS
References: Haggard, D. et al, 2010 ApJ 723:1447-1468
Distance Estimate: 9.55 billion light years (z=0.0701)

Fast Facts for SDSS J1021+1312:

Scale: Image is 3.2 arcmin across. (8.92 million light years across)
Category: Normal Galaxies & Starburst Galaxies Quasars & Active Galaxies
Coordinates: (J2000) RA 10h 21m 47.86s | Dec +13° 12' 28.19''
Constellation: Leo
Observation Dates: 1/31/2003
Observation Time: 2 hours 47 min
Obs. IDs/: 4107
Color Code: X-ray (Blue), Optical (Red, Yellow, White)
Instrument: ACIS
References: Haggard, D. et al, 2010 ApJ 723:1447-1468
Distance Estimate: 9.582 billion light years (z=0.085)