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The Galactic Central Diffuse X-Ray Enhancement: A Differential Absorption/Emission Analysis

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dc.contributor.authorYao, Y
dc.contributor.authorWang, QD
dc.contributor.departmentUniversity of Massachusetts - Amherst
dc.date2023-09-23T03:42:37.000
dc.date.accessioned2024-04-26T08:25:41Z
dc.date.available2024-04-26T08:25:41Z
dc.date.issued2007-01-01
dc.description<p>This is the pre-published version harvested from ArXiv. The published version is located at <a href="http://iopscience.iop.org/0004-637X/666/1/242?v_showaffiliations=no">http://iopscience.iop.org/0004-637X/666/1/242?v_showaffiliations=no</a></p>
dc.description.abstractThe soft X-ray background shows a general enhancement toward the inner region of the Galaxy. But whether this enhancement is a local feature (e.g., a superbubble within a distance of 200 pc) and/or a phenomenon related to energetic outflows from the Galactic center/bulge remains unclear. Here we report a comparative X-ray emission and absorption study of diffuse hot gas along the sight lines toward 3C 273 and Mrk 421, on and off the enhancement, but at similar Galactic latitudes. The diffuse 3/4 keV emission intensity, as estimated from the ROSAT All Sky Survey, is about 3 times higher toward 3C 273 than toward Mrk 421. Based on archival Chandra grating observations of these two AGNs, we detect X-ray absorption lines (e.g., O VII Kα, Kβ, and O VIII Kα transitions at z ~ 0) and find that the mean hot gas thermal and kinematic properties along the two sight lines are significantly different. By subtracting the foreground and background contribution, as determined along the Mrk 421 sight line, we isolate the net X-ray absorption and emission produced by the hot gas associated with the enhancement in the direction of 3C 273. From a joint analysis of these differential data sets, we obtain the temperature, dispersion velocity, and hydrogen column density as 2.0(1.6,2.3) × 106 K, 216(104, 480) km s-1, and 2.2(1.4,4.1) × 1019 cm-2, respectively (90% confidence intervals), assuming that the gas is approximately isothermal, solar in metal abundances, and equilibrium in collisional ionization. We also constrain the effective line-of-sight extent of the gas to be 3.4(1.0, 10.1) kpc, strongly suggesting that the enhancement most likely represents a Galactic central phenomenon.
dc.description.pages242-
dc.identifier.doihttps://doi.org/10.1086/519825
dc.identifier.urihttps://hdl.handle.net/20.500.14394/2709
dc.relation.ispartofThe Astrophysical Journal
dc.relation.urlhttps://scholarworks.umass.edu/cgi/viewcontent.cgi?article=2066&amp;context=astro_faculty_pubs&amp;unstamped=1
dc.source.issue1
dc.source.issue666
dc.source.statuspublished
dc.subjectGalaxy: structure; X-rays: individual (3C 273
dc.subjectMrk 421); X-rays: ISM
dc.subjectAstrophysics and Astronomy
dc.titleThe Galactic Central Diffuse X-Ray Enhancement: A Differential Absorption/Emission Analysis
dc.typearticle
dc.typearticle
digcom.contributor.authorYao, Y
digcom.contributor.authorisAuthorOfPublication|email:wqd@astro.umass.edu|institution:University of Massachusetts - Amherst|Wang, QD
digcom.identifierastro_faculty_pubs/1088
digcom.identifier.contextkey1949927
digcom.identifier.submissionpathastro_faculty_pubs/1088
dspace.entity.typePublication
relation.isAuthorOfPublication702446e9-94cf-40bd-9d01-6802ee56ee93
relation.isAuthorOfPublication.latestForDiscovery702446e9-94cf-40bd-9d01-6802ee56ee93
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