Velocity Modification of HI Power Spectrum

Preprint
Publisher Website
Google Scholar
  • 19 January 1999
Abstract
The distribution of atomic hydrogen in the galactic plane is usually mapped using the Doppler shift of 21 cm emission line and this causes the modification of the observed spectrum which is frequently referred to as velocity crowding effect. We calculate HI spectrum in the velocity space and derive the observed spectrum dependence on the statistics of velocity and density fields. We show that the inversion procedure suggested in Lazarian (1995) provides 3D spectrum of HI emissivity and the shallow spectrum reported there may be the consequence of the underlying Kolmogorov-type velocity turbulence. The alternative explanation, namely, that the actual HI density spectrum is shallow, cannot be ruled out on the basis of the observational data currently available. We calculate how the spectra vary with the change of velocity slicing and claim that this variation can be used to distinguish the two cases above and to separate the velocity and density contributions to the 21 cm intensity spectrum.

This publication has 0 references indexed in Scilit: