Neutral hydrogen emission-absorption observations of high-velocity clouds

Abstract

view Abstract Citations (34) References (30) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Neutral hydrogen emission-absorption observations of high-velocity clouds. Payne, H. E. ; Salpeter, E. E. ; Terzian, Y. Abstract Neutral hydrogen emission-absorption studies were carried out at Arecibo Observatory for some 'high-velocity clouds' with velocity absolute value of v greater than 50 km/s. Conspicuous, narrow absorption features are rare but were found in a few cases. In addition to these few confirmed features, statistical tests indicate the presence of more widespread weak absorption. Harmonic mean spin temperatures of a few hundred K are obtained from averages over velocity and sky position for the high-velocity material, comparable to spin temperatures for low-velocity local clouds of equally small column density. Narrow absorption features are correlated with strong emission variations over angular scales of 4 arcmin, suggesting a two-component model for high-velocity material: (1) warm ('not strongly absorbing') neutral hydrogen smoothly distributed over a whole 'high-velocity cloud complex,' and (2) a patchy distribution of cooler cloudlets, possibly below 100 K. Publication: The Astrophysical Journal Pub Date: September 1980 DOI: 10.1086/158255 Bibcode: 1980ApJ...240..499P Keywords: Absorption Spectra; Emission Spectra; Hydrogen Clouds; Interstellar Gas; Radio Sources (Astronomy); Astrophysics; Centimeter Waves; Neutral Gases; Astrophysics full text sources ADS | data products SIMBAD (8)