Evidence for an X-Ray–emitting Galactic Bulge: Shadows Cast by Distant Molecular Gas | Zendy

Sangwook Park | Zendy; J. P. Finley | Zendy; S. L. Snowden | Zendy; T. M. Dame | Zendy

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Evidence for an X-Ray–emitting Galactic Bulge: Shadows Cast by Distant Molecular Gas

Author(s) -

Sangwook Park,

J. P. Finley,

S. L. Snowden,

T. M. Dame

Publication year - 1997

Publication title -

the astrophysical journal

Language(s) - English

Resource type - Journals

SCImago Journal Rank - 2.376

H-Index - 489

eISSN - 1538-4357

pISSN - 0004-637X

DOI - 10.1086/310501

Subject(s) - rosat , astrophysics , physics , bulge , molecular cloud , galactic plane , galactic center , flux (metallurgy) , x ray , astronomy , galaxy , optics , materials science , stars , metallurgy

A mosaic of 7 ROSAT PSPC pointed observations in the direction of (l,b ~ 10,0deg) reveals deep X-ray shadows in the 0.5-2.0 keV band cast by dense moleculargas. The comparison between the observed on-cloud and off-cloud X-ray fluxesindicates that ~43% of the diffuse X-ray background in this direction in boththe 3/4 keV and 1.5 keV bands originates behind the molecular gas, which islocated at 2-4 kpc from the Sun. Given the short mean free path of X-rays inthe 3/4 keV band in the Galactic plane (~1 kpc assuming an average spacedensity of 1 cm^-3), this large percentage of the observed flux whichoriginates beyond the molecular gas most likely indicates a strong enhancementin the distribution of X-ray emitting gas in the Galactic center region,possibly associated with a Galactic X-ray bulge.Comment: 16 pages LaTex, 2 figures. Accepted for the publication in Astrophysical Journal, Letter

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