Two Methods of Investigating the Nature of the Nebular Redshift

Abstract

view Abstract Citations (105) References Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Two Methods of Investigating the Nature of the Nebular Redshift Hubble, Edwin ; Tolman, Richard C. Abstract Two theoretically possible methods of investigating the nature of the nebular red- shift have been known for some time. These two methods depend on the relations con- necting either nebular dimensions with observed luminosities or nebular counts with observed luminosities, which might be expected to hold under the alternative assump- tions of mutual recession or some other cause for the red-shift. The main purpose of the present article is to study in detail the procedure that must be adopted in applying these methods to actual observations in view of such factors as the indefiniteness of nebular diameters resulting from their gradual decrease in surface brightness from the center outward, the necessity for relating apparent bolometric luminosities to observed photo- graphic magnitudes, and the effect on nebular counts produced by a wide spread in the values of absolute nebular magnitudes. In addition to this study, preliminary statements are made as to the present status of the observational findings. In the case of the relation between nebular dimensions and luminosities, the observations are such as to confirm our general ideas as to the extra-galactic character of the objects in question, but are not yet sufficient to permit a decision between recessional or other causes for the red-shift. In the case of the relation between nebular counts and luminosities, the observations now available show a rate of increase in counts with distance which seems rather large compared with what would be expected for a homogeneous distribution of nebulae on the basis of either a recessional or a non-recessional theory. Nevertheless, by assuming no appreciable absorption of light on the path from the nebulae and by ascribing a rather high effective temperature to the nebulae, it might be possible to explain the counts on the basis of either a static homogeneous model with some unknown cause for the red-shift or an expanding homo- geneous model having a positive spatial curvature which introduces effects that seem unexpectedly large but may not be impossible. This conclusion must be considered as tentative, however, and may need serious modification as a result of further work Publication: The Astrophysical Journal Pub Date: November 1935 DOI: 10.1086/143682 Bibcode: 1935ApJ....82..302H full text sources ADS | Related Materials (1) Reprint: 1935CMWCI.527....1H