Six-Color Photometry of Stars. V. Infrared Radiation from the Region of the Galactic Center.
Abstract
A search for the nucleus of our galaxy has been made in a band of infrared radiation at effective wave length 10,300 A. With a photocell and suitable filter on the 60-inch reflector, the sky was allowed to drift with the diurnal motion across the field of a focal diaphragm 8 6 in diameter. As the intensity along each sweep was recorded, the star clouds and individual stars interfered somewhat, but not entirely, with the penetration to the background. The area of the search extended about 2° on each side of the galactic equator from longitude 321° to 331°, with intensive coverage within 10 of the equator and with supple-. mentary sweeps of greater extent at selected points. The sweeps at successive longitudes usually gave maxima near the galactic circle, outlining a bulge extending about 8° in longitude and 4° or 50 in lati- tude, with center near 326~5. Concurrent sweeps in the red at wave length 7190 A gave a color excess on the red-infrared scale of +1.5 mag., equal to that of the most strongly reddened B stars in the sky. It is shown that the radiation cannot come from a mixture of star clouds and absorbing material like that within 1 or 2 kpc of the sun but must come from a more luminous object behind absorbing material. The light of the bulge, with maximum apparent photographic surface brightness of 25.4 mag/sq sec, adds up, when corrected for absorption, to a total quite comparable with the light of an equal section of the Andromeda nebula. That the observed bulge is probably near the galactic center is shown by its position, form, color, and total light
- Publication:
-
The Astrophysical Journal
- Pub Date:
- September 1947
- DOI:
- 10.1086/144954
- Bibcode:
- 1947ApJ...106..235S