Characterizing Transition Temperature Gas in the Galactic Corona

Details Characterizing Transition Temperature Gas in the Galactic Corona Characterizing Transition Temperature Gas in the Galactic Corona

2012-02-27

arxiv.org/abs/1202.5973v1

Astronomy and Astrophysics

Astrophysics

Galaxy Astrophysics

99 pages, 11 figures, with appendix on Cooling Flow model; only a sample of 5 subfigures of figure 2 included - full set of 69

Scientific paper

We present a study of the properties of the transition temperature (T~10^5 K) gas in the Milky Way corona, based on measurements of OVI, NV, CIV, SiIV and FeIII absorption lines seen in the far ultraviolet spectra of 58 sightlines to extragalactic targets, obtained with Far-Ultraviolet Spectroscopic Explorer (FUSE) and Space Telescope Imaging Spectrograph. In many sightlines the Galactic absorption profiles show multiple components, which are analyzed separately. We find that the highly-ionized atoms are distributed irregularly in a layer with a scaleheight of about 3 kpc, which rotates along with the gas in the disk, without an obvious gradient in the rotation velocity away from the Galactic plane. Within this layer the gas has randomly oriented velocities with a dispersion of 40-60 km/s. On average the integrated column densities are log N(OVI)=14.3, log N(NV)=13.5, log N(CIV)=14.2, log N(SiIV)=13.6 and log N(FeIII)=14.2, with a dispersion of just 0.2 dex in each case. In sightlines around the Galactic Center and Galactic North Pole all column densities are enhanced by a factor ~2, while at intermediate latitudes in the southern sky there is a deficit in N(OVI) of about a factor 2, but no deficit for the other ions. We compare the column densities and ionic ratios to a series of theoretical predictions: collisional ionization equilibrium, shock ionization, conductive interfaces, turbulent mixing, thick disk supernovae, static non-equilibrium ionization (NIE) radiative cooling and an NIE radiative cooling model in which the gas flows through the cooling zone. None of these models can fully reproduce the data, but it is clear that non-equilibrium ionization radiative cooling is important in generating the transition temperature gas.

Affiliated with

Also associated with

No associations

Rating

Characterizing Transition Temperature Gas in the Galactic Corona does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.

If you have personal experience with Characterizing Transition Temperature Gas in the Galactic Corona, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Characterizing Transition Temperature Gas in the Galactic Corona will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFWR-SCP-O-263795