H I, galaxy counts, and reddening: Variation in the gas-to-dust ratio, the extinction at high galactic latitudes, and a new method for determining galactic reddening

Journal Article · Sun Oct 01 04:00:00 EDT 1978 · Astrophys. J.; (United States)

DOI:https://doi.org/10.1086/156466· OSTI ID:6855424

Burstein, D; Heiles, C

We reanalyze the interrelationships among Shane-Wirtanen galaxy counts, H I column densities, and reddenings, and resolve many of the problems raised by Heiles. These problems were caused by two factors: subtle biases in the reddening data and a variable gas-to-dust ratio in the galaxy. We present a compilation of reddenings for RR Lyrae stars and globular clusters which are on the same system and which we believe to be relatively free of biases. The extinction at the galactic poles, as determined by galaxy counts, is reexamined by using a new method to analyze galaxy counts. This new method partially accounts for the nonrandom clustering of galaxies and permits a reasonable estimate of the error in log N/sub gal/ as a function of latitude. The analysis shows that the galaxy counts (or galaxy cluster counts) are too noisy to allow direct determination of the extinction, or variation in extinction, near the galactic poles. From all available data, we conclude that the reddening at the poles is small (< or =0.02 mag in E (B--V) over much of the north galactic pole) and irregularly distributed. We find that there are zero offsets in the relations between E (B--V) and H I, and between galaxy counts and H I, which are at least partly the result of an instrumental effect in the radio data. We also show that the gas-to-dust ratio can vary by a factor of 2 from the average, and we present two methods for correcting for this variability in predicting the reddening of objects which are located outside of the galactic absorbing layer. We present a prescription for predicting these reddenings; in the area of sky covered by the Shane-Wirtanen galaxy counts, the error in these predictions is, on average, less than 0.03 mag in E (B--V).

• Research Organization: Board of Studies, Astronomy and Astrophysics, University of California, Santa Cruz
• OSTI ID: 6855424
• Journal Information: Astrophys. J.; (United States), Journal Name: Astrophys. J.; (United States) Vol. 225:1; ISSN ASJOA
• Country of Publication: United States
• Language: English

Related Subjects

640105* -- Astrophysics &amp; Cosmology-- Galaxies
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
COSMIC DUST
COSMIC GASES
COSMIC RADIO SOURCES
DUSTS
FLUIDS
GALAXIES
GALAXY CLUSTERS
GASES
H1 REGIONS
INTERSTELLAR SPACE
SPACE
STAR CLUSTERS
STARS
VARIABLE STARS