Astronomy and Astrophysics – Astronomy
Scientific paper
May 2010
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2010aas...21642404s&link_type=abstract
American Astronomical Society, AAS Meeting #216, #424.04; Bulletin of the American Astronomical Society, Vol. 41, p.836
Astronomy and Astrophysics
Astronomy
Scientific paper
The Galactic halo is permeated by gas with a temperature between 1 and 3 million K. X-rays generated by this gas contribute significantly to the diffuse X-ray background (SXRB) at high Galactic latitudes. Spectroscopy of the SXRB emission enables us to determine the physical conditions in the hot gas, providing clues to its origin and evolution.
We present an analysis of 26 high-latitude XMM-Newton observations of the SXRB. These observations were chosen from a larger set because they are expected to have the smallest levels of contamination from solar wind charge exchange X-rays. By fitting models that account for local, halo, and extragalactic contributions to the observed spectra, we found that the temperature of the halo is similar ( 2.0 to 2.5 MK) on all of our sight lines, but that the X-ray emission measure varies greatly ( 0.0005 to 0.005 cm-6 pc).
We compare our halo measurements with predictions from three hydrodynamic models for hot gas in the halo: an extended hot halo (r 10s of kpc) predicted by disk galaxy formation models, a population of isolated supernova remnants (SNRs) above the disk, and a SN-driven intersteller medium (ISM) that includes individual supernova explosions and their interactions, resulting in global circulation of gas between the disk and the halo. The extended hot halo and the population of isolated halo SNRs are at least an order of magnitude too faint in the XMM-Newton bandpass. The SN-driven ISM model provides a better match to the observations. However, this model still underpredicts the median emission measure of the 2-MK gas by 0.5 dex.
Henley David B.
Joung Minkyoo
Kwak Kyujin
Mac Low Mordecai-Mar
Shelton Robin L.
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