{ "id": "astro-ph/0107493", "version": "v2", "published": "2001-07-25T23:01:05.000Z", "updated": "2002-04-03T21:25:31.000Z", "title": "Untangling the X-ray Emission From the Sa Galaxy NGC1291 With Chandra", "authors": [ "Jimmy A. Irwin", "Craig L. Sarazin", "Joel N. Bregman" ], "comment": "13 pages in emulateapj5 style with 11 embedded Postscript figures; minor revisions since last version; accepted by ApJ", "doi": "10.1086/339734", "categories": [ "astro-ph" ], "abstract": "We present a Chandra ACIS-S observation of the nearby bulge-dominated Sa galaxy NGC1291. The X-ray emission from the bulge resembles the X-ray emission from a sub-class of elliptical and S0 galaxies with low L_X/L_B luminosity ratios. The X-ray emission is composed of a central point-like nucleus, ~50 point sources that are most likely low mass X-ray binaries (LMXBs), and diffuse gas detectable out to a radius of 120\" (5.2 kpc). The diffuse gas has a global temperature of 0.32^{+0.04}_{-0.03} keV and metallicity of 0.06 +/- 0.02 solar, and both quantities marginally decrease with increasing radius. The hot gas fills the hole in the HI distribution, and the softening of the spectrum of the X-ray gas with radius might indicate a thermal coupling of the hot and cold phases of the interstellar medium as previously suggested. The integrated X-ray luminosity of the LMXBs, once normalized by the optical luminosity, is a factor of 1.4 less than in the elliptical galaxy NGC4697 or S0 galaxy NGC1553. The difference in L_{X,stellar}/L_B between the galaxies appears to be because of a lack of very bright sources in NGC1291. No sources above 3 x 10^38 ergs/s were found in NGC1291 when ~7 were expected from scaling from NGC4697 and NGC1553. The cumulative L_{X,stellar}/L_B value including only sources below 1.0 x 10^38 ergs/s is remarkably similar between NGC1291 and NGC4697, if a recent surface brightness fluctuation-determined distance is assumed for NGC4697. If this is a common feature of the LMXB population in early-type systems, it might be used as a distance indicator. Finally, a bright, variable (1.6-3.1 x 10^39 ergs/s) source was detected at the optical center of the galaxy. Its spectrum shows excess soft emission superimposed on a highly absorbed power law component, similar to what has been found in several other low luminosity AGN (ABRIDGED).", "revisions": [ { "version": "v2", "updated": "2002-04-03T21:25:31.000Z" } ], "analyses": { "keywords": [ "x-ray emission", "absorbed power law component", "luminosity", "low mass x-ray binaries", "diffuse gas" ], "tags": [ "journal article" ], "note": { "typesetting": "TeX", "pages": 13, "language": "en", "license": "arXiv", "status": "editable", "inspire": 575777 } } }