GASKAP Pilot Survey Science. II. ASKAP Zoom Observations of Galactic 21 cm Absorption - INSU - Institut national des sciences de l'Univers Access content directly
Journal Articles The Astrophysical Journal Year : 2022

GASKAP Pilot Survey Science. II. ASKAP Zoom Observations of Galactic 21 cm Absorption

John M. Dickey
  • Function : Author
J. M. Dempsey
  • Function : Author
N. M. Pingel
  • Function : Author
N. M. Mcclure-Griffiths
  • Function : Author
K. Jameson
  • Function : Author
J. R. Dawson
  • Function : Author
H. Dénes
  • Function : Author
S. E. Clark
  • Function : Author
G. Joncas
  • Function : Author
D. Leahy
  • Function : Author
Min-Young Lee
  • Function : Author
S. Stanimirović
  • Function : Author
C. D. Tremblay
  • Function : Author
J. Th. van Loon
  • Function : Author

Abstract

Using the Australian Square Kilometre Array Pathfinder to measure 21 cm absorption spectra toward continuum background sources, we study the cool phase of the neutral atomic gas in the far outer disk, and in the inner Galaxy near the end of the Galactic bar at longitude 340°. In the inner Galaxy, the cool atomic gas has a smaller scale height than in the solar neighborhood, similar to the molecular gas and the super-thin stellar population in the bar. In the outer Galaxy, the cool atomic gas is mixed with the warm, neutral medium, with the cool fraction staying roughly constant with the Galactic radius. The ratio of the emission brightness temperature to the absorption, i.e., 1 - e , is roughly constant for velocities corresponding to Galactic radius greater than about twice the solar circle radius. The ratio has a value of about 300 K, but this does not correspond to a physical temperature in the gas. If the gas causing the absorption has kinetic temperature of about 100 K, as in the solar neighborhood, then the value 300 K indicates that the fraction of the gas mass in this phase is one-third of the total H I mass.
Fichier principal
Vignette du fichier
Dickey_2022_ApJ_926_186.pdf (1.83 Mo) Télécharger le fichier
Origin : Publisher files allowed on an open archive

Dates and versions

insu-03745336 , version 1 (04-08-2022)

Licence

Attribution

Identifiers

Cite

John M. Dickey, J. M. Dempsey, N. M. Pingel, N. M. Mcclure-Griffiths, K. Jameson, et al.. GASKAP Pilot Survey Science. II. ASKAP Zoom Observations of Galactic 21 cm Absorption. The Astrophysical Journal, 2022, 926, ⟨10.3847/1538-4357/ac3a89⟩. ⟨insu-03745336⟩
8 View
18 Download

Altmetric

Share

Gmail Facebook X LinkedIn More