Issue |
Astron. Astrophys. Suppl. Ser.
Volume 127, Number 2, January II 1998
|
|
---|---|---|
Page(s) | 327 - 333 | |
DOI | https://doi.org/10.1051/aas:1998354 | |
Published online | 15 January 1998 |
Crowded-field photometry from HST-imaging*
Institut for Fysik og Astronomi, Aarhus Universitet, Ny Munkegade, DK-8000 Århus C, Denmark
Received:
31
January
1997
Accepted:
9
May
1997
We present a thorough investigation of stellar photometry based
on HST imaging of crowded fields at and
from the centre of the high-surface brightness elliptical galaxy M 32.
The Principal Investigators of the present archive data have elsewhere
presented an impressive colour-magnitude diagram of the field at
.
Based on the same data we enlarge on their photometric analysis
and supplement with error estimators that more clearly show the
implications of severe image crowding on the stellar photometry.
We show that the faintest stars (
,
) are found too
bright by several tens of a magnitude.
For the field at
we conclude that
it is not possible to obtain reliable stellar photometry,
standard deviations being larger than 0.4 mag.
Artificial-star experiments show that only very few of the brightest stars
of the luminosity function can be expected to represent single objects,
the majority being either spurious or not as bright as measured.
The paper as such introduces and demonstrates
basic guide lines which may be used when dealing with stellar photometry of
severely crowded fields.
Key words: methods: data analysis / galaxies: elliptical / galaxies: individual: M 32 / galaxies: stellar content
© European Southern Observatory (ESO), 1998