Fitting Together the HI Absorption and Emission in the SGPS

Details Fitting Together the HI Absorption and Emission in the SGPS Fitting Together the HI Absorption and Emission in the SGPS

2002-11-13

arxiv.org/abs/astro-ph/0211298v1

Astrophys.J. 585 (2003) 801-822

Astronomy and Astrophysics

Astrophysics

50 pages, 20 figures

Scientific paper

10.1086/346081

In this paper we study 21-cm absorption spectra and the corresponding emission spectra toward bright continuum sources in the test region (326deg< l < 333 deg) of the Southern Galactic Plane Survey. This survey combines the high resolution of the Australia Telescope Compact Array with the full brightness temperature information of the Parkes single dish telescope. In particular, we focus on the abundance and temperature of the cool atomic clouds in the inner galaxy. The resulting mean opacity of the HI, , is measured as a function of Galactic radius; it increases going in from the solar circle, to a peak in the molecular ring of about four times its local value. This suggests that the cool phase is more abundant there, and colder, than it is locally. The distribution of cool phase temperatures is derived in three different ways. The naive, ``spin temperature'' technique overestimates the cloud temperatures, as expected. Using two alternative approaches we get good agreement on a histogram of the cloud temperatures, T(cool), corrected for blending with warm phase gas. The median temperature is about 65 K, but there is a long tail reaching down to temperatures below 20 K. Clouds with temperatures below 40 K are common, though not as common as warmer clouds (40 to 100 K). Using these results we discuss two related quantities, the peak brightness temperature seen in emission surveys, and the incidence of clouds seen in HI self-absorption. Both phenomena match what would be expected based on our measurements of and T(cool).

Affiliated with

Also associated with

No associations

Rating

Fitting Together the HI Absorption and Emission in the SGPS 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 Fitting Together the HI Absorption and Emission in the SGPS, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Fitting Together the HI Absorption and Emission in the SGPS will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFWR-SCP-O-293598