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2004MNRAS.353..221N - Mon. Not. R. Astron. Soc., 353, 221-242 (2004/September-1)
XMM-Newton observations of the merger-remnant galaxies NGC 3921 and 7252.
NOLAN L.A., PONMAN T.J., READ A.M. and SCHWEIZER F.
Abstract (from CDS):
We detect three candidate ultraluminous X-ray point sources (ULXs) in NGC 3921 and at least six in NGC 7252, for which we have high spatial resolution Chandra data. These have luminosities ranging from ∼1.4x1039-1040 erg/s (for H0= 75 km/s/Mpc). We expect these ULXs to be high-mass X-ray binaries, associated with the recent star formation in these two galaxies.
Extended hot gas is observed in both galaxies. We have sufficient counts in the XMM-Newton data to fit two-component hot plasma models to their X-ray spectra, and estimate the X-ray luminosities of the hot diffuse gas components to be 2.75x1040 erg/s and 2.09 x1040 erg/s in NGC 3921 and 7252, respectively. These luminosities are low compared with the luminosities observed in typical mature elliptical galaxies (LX∼ 1041-1042 erg/s), into which these merger remnants are expected to evolve. We do not see evidence that the X-ray haloes of these galaxies are currently being regenerated to the masses and luminosities seen in typical elliptical galaxies. The mass of atomic gas available to fall back into the main bodies of these galaxies and shock-heat to X-ray temperatures is insufficient for this to be the sole halo regeneration mechanism. We conclude that halo regeneration is most likely a long-term (>10 Gyr) process, occurring predominantly via mass loss from evolving stars, in a subsonic outflow stage commencing ∼2 Gyr after the merging event.
Abstract Copyright: 2004 RAS
Journal keyword(s): galaxies: evolution - galaxies: individual: NGC 3921 - galaxies: individual: NGC 7252 - X-rays: binaries - X-rays: galaxies - X-rays: ISM
Nomenclature: Fig.3, Table 3: [NPR2004] NGC 3921 X-N (Nos X-1 to X-4). Fig.12, Table 7: [NPR2004] NGC 7252 X-NN (Nos X-1 to X-14).
CDS comments: In table 12, A 127 = [SMW96] 127, A 128 = [SMW96] 128.
Simbad objects: 33
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