2012ApJ...758...65B


Query : 2012ApJ...758...65B

2012ApJ...758...65B - Astrophys. J., 758, 65 (2012/October-2)

The diverse hot gas content and dynamics of optically similar low-mass elliptical galaxies.

BOGDAN A., DAVID L.P., JONES C., FORMAN W.R. and KRAFT R.P.

Abstract (from CDS):

The presence of hot X-ray-emitting gas is ubiquitous in massive early-type galaxies. However, much less is known about the content and physical status of the hot X-ray gas in low-mass ellipticals. In the present paper, we study the X-ray gas content of four low-mass elliptical galaxies using archival Chandra X-ray observations. The sample galaxies, NGC 821, NGC 3379, NGC 4278, and NGC 4697, have approximately identical K-band luminosities, and hence stellar masses, yet their X-ray appearance is strikingly different. We conclude that the unresolved emission in NGC 821 and NGC 3379 is built up from a multitude of faint compact objects, such as coronally active binaries and cataclysmic variables. Despite the non-detection of X-ray gas, these galaxies may host low density, and hence low luminosity, X-ray gas components, which undergo an outflow driven by a Type Ia supernova (SN Ia). We detect hot X-ray gas with a temperature of kT ∼ 0.35 keV in NGC 4278, the component of which has a steeper surface brightness distribution than the stellar light. Within the central 50'' (∼3.9 kpc), the estimated gas mass is ∼3x107 M, implying a gas mass fraction of ∼0.06%. We demonstrate that the X-ray gas exhibits a bipolar morphology in the northeast-southwest direction, indicating that it may be outflowing from the galaxy. The mass and energy budget of the outflow can be maintained by evolved stars and SNe Ia, respectively. The X-ray gas in NGC 4697 has an average temperature of kT ∼ 0.3 keV and a significantly broader distribution than the stellar light. The total gas mass within 90'' (∼5.1 kpc) is ∼2.1x108 M, hence the gas mass fraction is ∼0.4%. Based on the distribution and physical parameters of the X-ray gas, we conclude that it is most likely in hydrostatic equilibrium, although a subsonic outflow may be present.

Abstract Copyright:

Journal keyword(s): galaxies: elliptical and lenticular, cD - galaxies: individual (NGC 821, NGC 3379, NGC 4278, NGC 4697) - galaxies: ISM - X-rays: galaxies - X-rays: general - X-rays: ISM

Simbad objects: 7

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Number of rows : 7
N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2021
#notes
1 M 32 IG 00 42 41.825 +40 51 54.61 9.51 9.03 8.08     ~ 2049 2
2 M 31 G 00 42 44.330 +41 16 07.50 4.86 4.36 3.44     ~ 11440 1
3 NGC 821 G 02 08 21.150 +10 59 41.53   12.210 11.310 10.739 9.744 ~ 546 0
4 M 105 LIN 10 47 49.600 +12 34 53.87   10.56 9.76 9.12 8.18 ~ 1400 0
5 NGC 4278 LIN 12 20 06.8253868 +29 16 50.713486 11.54 11.09 10.16     ~ 903 2
6 M 104 LIN 12 39 59.43185 -11 37 22.9954 9.51 9.55 8.00 8.05   ~ 1304 3
7 NGC 4697 GiG 12 48 35.8992791099 -05 48 02.497675635   10.97   9.83   ~ 818 0

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2021.09.17-15:45:05

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