Suzaku Observations of the Local and Distant Hot ISM
Abstract
Suzaku observed the molecular cloud MBM12 and a blank field less than 3 degrees away to separate the local and distant components of the diffuse soft X-ray background. Towards MBM12, a local (D< 275 pc) O VII emission line was clearly detected with an intensity of 3.5 ph cm^{-2} s^{-1} sr^{-1}$ (or line units, LU), and the O VIII flux was <0.34 LU. The origin of this O VII emission could be hot gas in the Local Hot Bubble (LHB), charge exchange between oxygen ions in the solar wind (SWCX) and geocoronal or interplanetary material, or a combination of the two. If entirely from the LHB, the implied temperature and emission measure would predict 1/4 keV emission in excess of observations. There is no evidence in the X-ray light curve or solar wind data for a significant contribution from geocoronal SWCX. In any case, the observed O VII flux represents an upper limit to both the LHB emission and interplanetary SWCX in this direction. The off-cloud observation was performed immediately following the on-cloud. The net off-cloud O VII and O VIII intensities were (respectively) 2.34\pm0.33 and 0.77\pm0.16 LU, after subtracting the on-cloud foreground emission. Assuming the LHB and SWCX components did not change, these increases can be attributed to more distant Galactic disk, halo, or extragalactic emission. If the distant O VII and O VIII emission is from a thermal plasma in collisional equilibrium beyond the Galactic disk, a temperature of (2.1\pm0.1)\times10^6 K with an emission measure of (4\pm0.6)\times10^-3} cm^{-6}pc is inferred.
Cite
@article{arxiv.astro-ph/0609832,
title = {Suzaku Observations of the Local and Distant Hot ISM},
author = {Randall K. Smith and Mark W. Bautz and Richard J. Edgar and Kenji Hamaguchi and John P. Hughes and Manabu Ishida and Richard Kelley and Caroline A. Kilbourne and K. D. Kuntz and Dan McCammon and Eric Miller and Kazuhisa Mitsuda and Koji Mukai and Paul P. Plucinsky and F. Scott Porter and Ryuichi Fujimoto and Steve Snowden and Yoh Takei and Yukikatsu Terada and Yohko Tsuboi and Noriko Yamasaki},
journal= {arXiv preprint arXiv:astro-ph/0609832},
year = {2015}
}
Comments
10 pages, 8 figures, accepted by PASJ