A complete Hα image of the Andromeda Galaxy (M31) is presented allowing the first direct measurement of the total Hα luminosity which is (7.3 +/- 2.4) x 10^6^L_sun_. The Hα emission is associated with three morphologically distinct components; a large scale star- forming ring, ~1.65^deg^ in diameter, contributing 66% of the total Hα emission, a bright nucleus contributing 6% of the total Hα emission with the remaining 28% contributed by a previously unidentified component of extended and filamentary Hα emission interior to the star forming ring. The correspondence between the Hα image and the IRAS far-infrared high resolution image is striking when both are convolved to a common resolution of 105 arcsec. The close correspondence between the far-infrared and Hα images suggests a common origin for the two emissions. The star-forming ring contributes 70% of the far- infrared luminosity of M31. Evidence that the ring emission is energized by high mass stars includes the fact that peaks in the far-infrared emission coincide identically with H II regions in the Hα image. In addition, the far-infrared to Hα luminosity ratio within the star- forming ring is similar to what one would expect for H II regions powered by stars of spectral types ranging between O9 and B0. The origin of the filamentary Hα and far-infrared luminosity interior to the star- forming ring is less clear, but it is almost certainly not produced by high mass stars.
No takes yet. Share an insight, caveat, or question.
Devereux et al. (1994) studied this question.