The Milky way at the Junction of Gemini, Monoceros, and Orion.

Abstract

view Abstract Citations (8) References (2) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The Milky Way at the Junction of Gemini, Monoceros, and Orion. Bok, Bart J. ; Olmsted, Margaret ; Boutelle, Betty D. Abstract The, present study is based largely on photographically determined color indices and magnitudes of stars in the Henry Draper Extension for the section between galactic `ongitudes 160° and 173°, `atitudes _30 and +9°. The structural features of the region are surveyed, and an attempt is made to determine what is the greatest well-determined distance for ~n object in this section of the Milky Way. The conclusion is reached that no known clusters or nebulae, 0 stars, c stars, or B stars are found at distances greater than 3000 parsecs and that the only known objects that are possibly at greater distances from the sun are three cepheid variables, one of which may be as distant as 5000 parsecs. It seems unlikely that, in the anticenter direction, the Milky Way system stretches more than 4000-5000 parsecs beyond our sun. The space reddening is highly variable over the section. For Field 1, at 1 = 171°, b = 00, we find relative freedom from overlying obscuration, with a value of Apg ~ 0.5 mag/kpc to a liniit of 3000 parsecs indicated. For Field 2, at 1 = 166°, b = 00, we find, however, Apg = 1.2-1.5 mag/kpc to a limit of 1500 parsecs, in agreement with an independent spectrum-color survey (Ap. J., 109, 139, 1949) by McCuskey. Fields 3 and 4, at galactic latitudes +3° and - 2°, adjacent to Field 2, yield space reddening comparable to that found for Field 2. Fields 5, 6, and 7, with 1 = 1640_1700 and b = +7°, are all relatively free from ob- scuration, with Apg = 0.5 mag/kpc to a limit of 2000 parsecs representing a fair average result. Incomplete color data for three fields with galactic latitudes -3° to -7° give evidence for the presence of strong near-by overlying absorption, presumably caused by extensions of the Taurus-Orion complex of dark nebulae. One field, No. 11, is reserved for subsequent and more detailed study; it is located near = 171°, b +3°, and falls in the region of clusters and bright nebulosity south of Wolf's great dark nebula. The space reddening appears to be quite irregular. In the preliminary analysis of the star densities, considerable stress is laid upon a comparison with the results obtained previously for a region at 1 = 185°, b = 00. Negative density gradients, with an average density 0.5 0 at a distance of 1000 parsecs, are found for the B8-A0 stars; the A1-A7 and FO-F8 stars yield average densities equal to 0.5 0 at distances of 500 parsecs or less. For the late-type giants the average space densities are fairly constant over the first 500 parsecs from the sun Publication: The Astrophysical Journal Pub Date: July 1949 DOI: 10.1086/145174 Bibcode: 1949ApJ...110...21B full text sources ADS |