A Radio Continuum Search for Twelve Low Surface Brightness Dwarf Galaxies

Details A Radio Continuum Search for Twelve Low Surface Brightness Dwarf Galaxies A Radio Continuum Search for Twelve Low Surface Brightness Dwarf Galaxies

Dec 1992

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1992aas...181.6511h&link_type=abstract

American Astronomical Society, 181st AAS Meeting, #65.11; Bulletin of the American Astronomical Society, Vol. 24, p.1223

Astronomy and Astrophysics

Astronomy

Scientific paper

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.

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