N. D. Vagshette, M. B. Pandge, M. K. Patil
We present spectral properties of 996 X-ray binary sources resolved in a sample of 23 dusty early-type galaxies selected from different environments. The combined X-ray luminosity function of all the 996 sources within optical D25 region of sample galaxies is well described by a broken power law, with a break at the Eddington luminosity for a 1.4 Msun neutron star. Out of the 996 discrete sources, about 33% of sources have their X-ray luminosities < few \times10^{37} erg/s; about 63% between few \times 10^{37} to 10^{39} erg/s; while the remainder 4% have luminosities greater than 10^{39} erg/s. All the sources with luminosities greater than few \times 10^{39} erg/s are defined as ULXs and host intermediate mass black holes as their accreting source. The difference in X-ray colors of the resolved sources in the sample galaxies were used to classify them in different classes, like, SNR, LMXBs, HMXBs and heavily absorbed AGNs. Comparison of the X-ray color plots for the resolved sources in elliptical and lenticular galaxies exhibit a significant difference in nature of the X-ray emitting sources, in the sense that, elliptical galaxies host an additional population of soft X-ray sources, while no such sources were evident in the lenticular galaxies. The composite X-ray spectra of the resolved sources within D25 region of each of the galaxy are best represented by a power law with the average photon spectral index close to 1.65. Contribution of the resolved sources to the total X-ray luminosity of their host is found to vary greatly in the sense that in galaxies like NGC 3379 XRB contribution is about 81%while for NGC 5846 it is only 2%. The combined X-ray luminosity of the resolved sources in a galaxy is found to correlated with star formation rate as well as Ks band luminosity and IR luminosity of the target galaxies.
View original:
http://arxiv.org/abs/1205.6057
No comments:
Post a Comment