Bibcode
Hoeppe, G.; Brinks, E.; Price, R. M.; Deeg, H. J.
Bibliographical reference
American Astronomical Society, 181st AAS Meeting, #65.11; Bulletin of the American Astronomical Society, Vol. 24, p.1223
Advertised on:
12
1992
Citations
0
Refereed citations
0
Description
The radio properties of low surface brightness (LSB) dwarf galaxies are
still largely unknown. To help remedying this situation we observed
twelve LSB dwarfs with the VLA at lambda = 3.6 cm and lambda = 20 cm.
All galaxies are included in the UGC catalog and have previously claimed
radio continuum detections at either 21 cm (Altschuler et al. 1984, AJ
89, 224; 1987, A&A 177, 22) or 6 cm (Klein 1986, A&A 168, 65;
Klein et al. 1992, A&A 255, 49). To our initial surprise we could
not find any continuum emission for the galaxies at either wavelength,
despite our considerably higher spatial resolution and sensitivity.
Typical 5sigma upper limits are 0.4 mJy at 3.6 cm and 0.7 mJy at 20 cm.
In our VLA maps we see nearby, generally unrelated background sources
around all galaxies. Due to their large FWHM beamwidths (3.3 arcmin for
Altschuler et al. and 2.5 arcmin for Klein et al.), the previous
observations were probably subject to confusion with these sources. The
actual number of background sources agrees with what can be expected
statistically as based on radio source counts (Fomalont 1984, Science,
225, 23; Windhorst et al. 1984, A&AS 58, 1). Klein et al. noted a
considerably lower detection rate for LSB dwarfs as compared to
``actively star forming'' dwarfs. Our results make this finding even
more dramatic. It is entirely possible that none of the galaxies in the
original sample of Altschuler et al. has a significant continuum flux
density, at least to the detection level of the Klein et al. survey of 2
mJy. We are currently in the process of obtaining optical broad-band
colors and Hα fluxes in order to understand better why these
galaxies are so radio quiet and to gain insights into their stellar
populations.