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Starcounts in the Hubble Deep Field: Fewer Than Expected, More Than Expected The Halo Main-Sequence & Halo White-Dwarf Luminosity Functions

Published online by Cambridge University Press:  25 May 2016

R. A. Méndez ,
G. de Marchi ,
D. Minniti ,
A. Baker  and
W. J. Couch
R. A. Méndez
Affiliation:
European Southern Observatory
G. de Marchi
Affiliation:
European Southern Observatory
D. Minniti
Affiliation:
Lawrence Livermore National Laboratory
A. Baker
Affiliation:
Institute of Astronomy
W. J. Couch
Affiliation:
School of Physics, University of New South Wales

Extract

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The Hubble Deep Field (HDF, Williams et al. 1996), recently acquired with the Hubble Space Telescope, is the deepest, most detailed optical view of the Universe. Even though intended primarily for the study of the high-redshift Universe, the HDF provides a unique opportunity to find faint stellar objects in our Galaxy, set constraints on number of low-mass Halo stars, estimate the contribution of baryonic matter to the dark Halo, investigate the nature of microlensing sources, and to calibrate Galactic Structure models. The HDF has been an STScI initiative to provide the deepest exposures yet acquired with HST on a non-proprietary basis. Observations of an ‘anonymous field’ located at l = 125.9°, b = 54.8° were performed on the continuous viewing zone, for a total of 150 orbits (10 consecutive days) in the four HST passbands F300W, F450W, F606W and F814W. These observations reached 5σ magnitude limits (for Galaxies) of roughly (STMAG) 30th mag in all these passbands (except F300W which reaches 27th mag). We have used a novel software detection & classification algorithm to create a sample of point-like objects in the HDF. We have also compared the observed stellar counts to constrain the faint end of the Halo field luminosity function by using a recent Galactic Structure model. The unexpected appearance of a faint-blue group of very compact objects is discussed as well.

Type
Part 4. Galactic Structure
Information
Symposium - International Astronomical Union , Volume 179: New Horizons from Multi-Wavelength Sky Surveys , 1998 , pp. 234 - 236
Copyright
Copyright © Kluwer 1998 

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