UTas ePrintsTracking the Outer Spiral Arms of the Galaxy in H I AbsorptionSTStrasserauthorNMMcClure-GriffithsauthorTARothwellauthorJMStilauthorJMDickeyauthorARTaylorauthorAIBoothroydauthorBMGaenslerauthorAJGreenauthorDWKavarsauthorFJLockmanauthorPGMartinauthorWe have analyzed 793 atomic hydrogen emission and absorption spectrum pairs toward continuum background sources in the northern and southern Galactic plane. In this paper we focus on absorption features from cold gas in the outermost arms of the Galaxy. We find H I absorption associated on a global scale with the outer spiral arm (first and second Galactic quadrants). To a lesser extent we also see absorption associated with the most distant spiral arm in the third and fourth Galactic quadrants. In total, 236 spectra contain clear absorption features associated with the outermost spiral arms. Cool-phase gas therefore exists throughout these spiral arms. The mean distances between absorbing clouds are on the order of 90-220 pc. We identify a number of striking H I structures with masses on the order of 105-106 M containing cool H I gas with temperatures below 100 K. These clouds are only marginally stable against gravitational collapse.240101 Astronomy and Astrophysics2007University of Chicago PressArticle

Permissions, Copyright and Authorship Statement
I grant the University of Tasmania permission to copy, store and communicate this work I declare that I either own the copyright in the work or I am submitting this work with permission of the copyright owner or under licence from the copyright owner. I declare that the metadata regarding authorship are true and correct and that it complies with the authorship requirements set down in the Joint NHMRC/AVCC Guidelines on Research and Practice.

Clicking on the deposit button indicates your agreement to these terms.