Astrophys. J., 722, 302-310 (2010/October-2)
Hot gas in the galactic thick disk and halo near the Draco cloud.
SHELTON R.L., HENLEY D.B. and DIXON W.V.
Abstract (from CDS):
This paper examines the ultraviolet and X-ray photons generated by hot gas in the Galactic thick disk or halo in the Draco region of the northern hemisphere. Our analysis uses the intensities from four ions, C IV, O VI, O VII, and O VIII, sampling temperatures of ∼105 to ∼3x106 K. We measured the O VI, O VII, and O VIII intensities from FUSE and XMM-Newton data and subtracted off the local contributions in order to deduce the thick disk/halo contributions. These were supplemented with published C IV intensity and O VI column density measurements. Our estimate of the thermal pressure in the O VI-rich thick disk/halo gas, pth/k = 6500+2500–2600 K/cm3, suggests that the thick disk/halo is more highly pressurized than would be expected from theoretical analyses. The ratios of C IV to O VI to O VII to O VIII intensities were compared with those predicted by theoretical models. Gas which was heated to 3x106 K then allowed to cool radiatively cannot produce enough C IV or O VI-generated photons per O VII or O VIII-generated photon. Producing enough C IV and O VI emission requires heating additional gas to 105 K < T < 106 K. However, shock heating, which provides heating across this temperature range, overproduces O VI relative to the others. Obtaining the observed mix may require a combination of several processes, including some amount of shock heating, heat conduction, and mixing, as well as radiative cooling of very hot gas.
Galaxy: general - Galaxy: halo - ISM: general - ISM: individual objects: Draco - ultraviolet: ISM - X-rays: diffuse background
View the reference in ADS
To bookmark this query, right click on this link: simbad:2010ApJ...722..302S and select 'bookmark this link' or equivalent in the popup menu