6 research outputs found
Chandra Observation of a Group of Galaxies HCG 80: Does the Spiral-Only Group Have Hot Intragroup Gas?
We present an analysis of Chandra X-ray observations of a compact group of
galaxies, HCG 80 (z=0.03). The system is a spiral-only group composed of four
late-type galaxies, and has a high-velocity dispersion of 309 km/s. With
high-sensitivity Chandra observations, we searched for diffuse X-ray emission
from the intragroup medium (IGM); however, no significant emission was
detected. We place a severe upper limit on the luminosity of the diffuse gas as
LX < 6e40 erg/s. On the other hand, significant emission from three of the four
members were detected. In particular, we discovered huge halo emission from HCG
80a that extends on a scale of ~30 kpc perpendicular to the galactic disk,
whose X-ray temperature and luminosity were measured to be ~0.6 keV and ~4e40
erg/s in the 0.5-2 keV band, respectively. It is most likely to be an outflow
powered by intense starburst activity. Based on the results, we discuss
possible reasons for the absence of diffuse X-ray emission in the HCG 80 group,
suggesting that the system is subject to galaxy interactions, and is possibly
at an early stage of IGM evolution.Comment: 12 pages, 6 figures; minor corrections. To appear in PASJ, Vol 56
No.
Detection of a Fully-resolved Compton Shoulder of the Iron K-alpha Line in the Chandra X-ray Spectrum of GX 301-2
We report the detection of a fully-resolved, Compton-scattered emission line
in the X-ray spectrum of the massive binary GX 301-2 obtained with the High
Energy Transmission Grating Spectrometer onboard the Chandra X-ray Observatory.
The iron K-alpha fluorescence line complex observed in this system consists of
an intense narrow component centered at an energy of E = 6.40 keV and a redward
shoulder that extends down to ~6.24 keV, which corresponds to an energy shift
of a Compton back-scattered iron K-alpha photon. From detailed Monte Carlo
simulations and comparisons with the observed spectra, we are able to directly
constrain the physical properties of the scattering medium, including the
electron temperature and column density, as well as an estimate for the metal
abundance.Comment: 13 pages, 4 figures, 1 table, accepted for publication in ApJ Lette