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Starcounts in the Hubble Deep Field: Constraining Galactic Structure Models

R. A. Mendez·D. Minniti·G. de Marchi·A. Baker·W. J. Couch
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Abstract

Stellar sources are identified in the Hubble Deep Field, and accurate colours and magnitudes are presented. The predictions of a Galactic starcounts model are compared with the faint stellar counts in this field. The model reproduces the observations very well in the magnitude range 21.0 < V < 26.4, while it overpredicts the counts by a factor of four in the range 26.4 < V < 30.0. The luminosity function for halo objects must be a factor of two smaller than that predicted by an extrapolation of the solar-neighborhood luminosity function for disc stars (with 95% confidence level). This result, seen before in deep Hubble Space Telescope images of globular clusters, is therefore confirmed for the halo field population. The possible nature of a group of faint-blue objects is also investigated, concluding that they are most likely non-stellar. The possibility that they are QSOs is ruled out. If we insist upon their stellar nature, they would be halo white dwarfs, with either a very steep halo white dwarf luminosity function for Mv > +11.0, or a stellar density 0.4 times that of the disc white dwarfs in the solar-neighborhood.

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R. A. Mendez, D. Minniti, G. de Marchi, A. Baker, W. J. Couch. 1996-11-06. Starcounts in the Hubble Deep Field: Constraining Galactic Structure Models. https://doi.org/10.1093/mnras%2F283.2.666

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