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Two discoveries from a distant quasar -- an enormous X-ray jet and an X-ray shadow cast by an intervening galaxy -- are giving astronomers using NASA's Chandra X-ray Observatory cause to be doubly excited. These two independent results reveal information about a supermassive black hole at the center of the quasar as well as the amount of oxygen in a distant galaxy billions of years ago.
In one set of Chandra observations of quasar PKS 1127-145, researchers found an X-ray jet that extends over a length of at least a million light years. The jet reveals explosive activity that occurred 10 billion years ago around the quasar's central supermassive black hole.
"The X-rays from the jet are likely due to the collision of microwave photons left over from the Big Bang with a high-energy beam of particles," said Aneta Siemiginowska of the Harvard-Smithsonian Center for Astrophysics in Cambridge, MA, lead author on a paper which will appear in the May 10, 2002, issue of the Astrophysical Journal. "The intensity of these microwaves today is much less than it was 10 billion years ago, due to the expansion of the universe."
Chandra observations of quasar PKS 1127-145 demonstrate that scientists can image these jets even though they are billions of light years away. Studies of these extraordinarily large structures will allow astronomers to test models for quasars and the supermassive black holes that power them.
The length of the jet and the prominent knots of X-ray emission observed suggest that the activity in the vicinity of the central supermassive black hole is long-lived but maybe intermittent, perhaps due to the mergers of other galaxies with the host galaxy.
In a separate result obtained by studying the same quasar, scientists found an X-ray shadow cast by an intervening galaxy. On their way to Earth, the X-rays from PKS 1127-145 pass through a galaxy located about 4 billion light years from Earth, which gives astronomers information about the amount of oxygen in the galaxy at that time.
Atoms of various elements in this galaxy absorb some of the X-rays, yielding a dimming of the quasar's X-rays. In a similar way, when our body is X-rayed, our bones produce an X-ray shadow. In this case, the quasar acts as the X-ray machine. By measuring the amount of absorption, astronomers were able to estimate that the intervening galaxy contained
The length of the jet and the prominent knots of X-ray emission observed suggest that the activity in the vicinity of the central supermassive black hole is long-lived but maybe intermittent, perhaps due to the mergers of other galaxies with the host galaxy.
In a separate result obtained by studying the same quasar, scientists found an X-ray shadow cast by an intervening galaxy. On their way to Earth, the X-rays from PKS 1127-145 pass through a galaxy located about 4 billion light years from Earth, which gives astronomers information about the amount of oxygen in the galaxy at that time.
Atoms of various elements in this galaxy absorb some of the X-rays, yielding a dimming of the quasar's X-rays. In a similar way, when our body is X-rayed, our bones produce an X-ray shadow. In this case, the quasar acts as the X-ray machine. By measuring the amount of absorption, astronomers were able to estimate that the intervening galaxy contained
"X-ray observations are especially important for this study," emphasized Bechtold. "They provide a direct measurement of the abundance of oxygen atoms without the complications of dust and other factors that make the interpretation of optical and ultraviolet observations difficult."
Other members of the research teams were Thomas Aldcroft, Martin Elvis, Dan Harris and Adam Dobrzycki (Harvard-Smithsonian Center for Astrophysics). The Advanced CCD Imaging Spectrometer (ACIS) X-ray camera, which was used in both observations, was developed for NASA by Pennsylvania State University, University Park, PA, and the Massachusetts Institute of Technology, Cambridge, MA. NASA's Marshall Space Flight Center in Huntsville, AL, manages the Chandra program. TRW, Inc., Redondo Beach, California, is the prime contractor for the spacecraft. The Smithsonian's Chandra X-ray Center controls science and flight operations from Cambridge, MA.
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Statement by R. Schild, based on a model by M. Elvis, both at the Harvard-Smithsonian Center for Astrophysics, October 3, 2001
The phenomena exibited by quasars and found from spectroscopic observation and polarimetry are so complex and varied that as yet no 'standard model' exists for them. There is a general feeling that the combination of infalling matter provides the fuel, but complex outflows, accretion disc rotation, and jet formation produce a variety of bizarre phenomena observed. Certainly the direction from which the quasar is viewed would play a role in what phenomena are observed, since the mass outflows and jets and orbiting blobs would have their radiations boosted by relativistic effects in these extraordinarily energetic regions.
The picture of quasar structure seems to be settling down to a black hole surrounded by an accretion disc that effectively shreds any incoming stellar or planetary mass fuel. The relativistic orbital speeds in this accretion disc imply relativistic emissions from the biconic outflows (that is, outflows in cones facing in opposite directions) that also seem to be observed as patterns of emission and obsorption lines, depending on the inclination angle at which a particular object is observed. The biconic outflows and jets are produced by gas pressure and radiation pressure forces, and probably twisted electromagnetic fields. All of this activity, including the black hole having the mass of an entire galaxy, seems to be confined to a region having the dimension of our inner solar system.