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The Frequency of Faint M Giant Stars at High Galactic Latitudes

Published online by Cambridge University Press:  30 March 2016

N. Sanduleak
N. Sanduleak*
Affiliation:
Case Western Reserve University-Warner and Swasey Observatory

Extract

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Based on the observations of M giant stars in the north galactic polar objective-prism survey of Upgren (1960) and the data summarized by Blanco (1965) the overall space density of all M-type giants as a function of distance from the galactic plane at the position of the sun can be approximated by,

where z is in kpc and ρ(z) is the number of stars per 106 pc3. This relationship is derived from the observed fall-off in space densities up to a distance of about 2 kpc.

The question arises as to the validity of extrapolation equation (1) to larger z distances so as to predict the number of faint M giants expected per unit area near the galactic poles. Adopting for the M giants a mean visual absolute magnitude of −1.0 (Blanco 1965), one finds that equation (1) predicts that less than one giant fainter than V~12 should be expected in a region of 200 square degrees. This expectation formed the hypothesis of a thesis study (Sanduleak 1965) in which it was assumed that the very faint M stars detected in a deep, infrared objective-prism survey at the NGP were main-sequence stars, since this could not be ascertained spectroscopically on the very low-dispersion plates used.

Type
Joint Discussions
Information
Highlights of Astronomy , Volume 4 , Issue 2: Highlights of Astronomy. As presented at the XVIth General Assembly of the IAU, 1976 (Part II) , 1977 , pp. 35 - 36
Copyright
Copyright © Reidel 1977

References

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Luyten, W. J.: 1976, Proper Motion Survey with the 48-Inch Schmidt Telescope XLVI, Univ. of Minnesota Press, Minneapolis.Google Scholar
Sanduleak, N.: 1965, “The Luminosity Function of the M Dwarf Stars”, Case Institute of Technology, Cleveland (Ph.D. Thesis).Google Scholar
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Upgren, A. R.: 1960, Astron. J. 65, 644.CrossRefGoogle Scholar