Issue |
Astron. Astrophys. Suppl. Ser.
Volume 137, Number 2, June I 1999
|
|
---|---|---|
Page(s) | 337 - 350 | |
DOI | https://doi.org/10.1051/aas:1999486 | |
Published online | 15 June 1999 |
Structure and stellar content of dwarf galaxies*
III. B and R photometry of dwarf galaxies in the M 101 group and the nearby field
1
Astronomical Institute, University of Basel, Venusstrasse 7, CH-4102 Binningen, Switzerland
2
Observatoire de Lyon, F-64561 St. Genis-Laval Cedex, France
Send offprint request to: T. Bremnes
Received:
4
January
1999
Accepted:
26
March
1999
We have carried out CCD photometry in the Cousins B and R bands of
21 dwarf galaxies in and around the M101 group. Eleven are
members and suspected members of the group and ten are field galaxies
in the projected vicinity of the group. We have derived total
magnitudes, effective radii, effective surface brightnesses, as well
as galaxy diameters at various isophotal levels in both colours.
Best-fitting exponential parameters and colour gradients are also
given for these galaxies. Some of the galaxies show a pronounced
luminosity excess above the best-fitting exponential at large radii,
or surface brightnesses fainter than in R. This feature, while non-significant
for a single case and technically difficult to interpret,
might be an indication of the existence of an extended
old stellar halo in dwarf irregulars. The photometric parameters of the
galaxies presented here will be combined with previously published
data for nearby dwarf galaxies and statistically analysed in a
forthcoming paper.
Key words: galaxies: general / galaxies: fundamental parameters / galaxies: photometry / galaxies: irregular / galaxies: structure / galaxies: luminosity function
© European Southern Observatory (ESO), 1999