PASJ: Publ. Astron. Soc. Japan 62, 723-733, 2010 June 25
(C) 2010. Astronomical Society of Japan

X-Ray Spectroscopy of Galactic Hot Gas along the PKS 2155$-$304 Sight Line

Toshishige HAGIHARA,¹ Yangsen YAO,² Noriko Y. YAMASAKI,¹ Kazuhisa MITSUDA,¹ Q. Daniel WANG,³ Yoh TAKEI,¹ Tomotaka YOSHINO,¹ and Dan MCCAMMON^4
1Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, 3-1-1 Yoshinodai, Chuo, Sagamihara 252-5210
hagihara@astro.isas.jaxa.jp, yamasaki@astro.isas.jaxa.jp
²University of Colorado, CASA, 389 UCB, Boulder, CO 80309, USA
³Department of Astronomy, University of Massachusetts, Amherst, MA 01003, USA
⁴Department of Physics, University of Wisconsin, Madison, 1150 University Avenue, Madison, WI 53706, USA

(Received 2009 December 16; accepted 2010 March 29)

Abstract:

We present a detailed spectroscopic study of the hot gas in the Galactic halo toward the direction of a blazer PKS 2155$-$304 ($z$ $=$ 0.117). The OVII and OVIII absorption lines were measured with the Low and High Energy Transmission Grating Spectrographs aboard Chandra, and the OVII, OVIII, and NeIX emission lines produced in an adjacent field of the PKS 2155$-$304 direction were observed with the X-ray Imaging Spectrometer aboard Suzaku. Assuming vertically exponential distributions of the gas temperature and the density, we performed a combined analysis of the absorption and emission data. The gas temperature and the density at the galactic plane were determined to be (2.5 $^{+0.6}_{ -0.3}$) $imes$ 10$^{6}$K and ($1.4^{+0.5}_{ -0.4}$) $imes$ 10$^{-3}$cm$^{-3}$, and the scale heights of the gas temperature and density were 5.6 $^{+7.4}_{ -4.2}$ kpc and 2.3 $^{+0.9}_{ -0.8}$ kpc, respectively. These values are consistent with those obtained in the LMC X-3 direction.

Key Words: Galaxy: disk — Galaxy: halo — X-rays: diffuse background — X-rays: ISM

Footnotes

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Present Address is NEC corporation, Nisshin-cho 1-10, Fuchu, Tokyo 183- 8551.

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