Dwarf galaxies, containing up to a few billion stars, are challenging to identify because of their low luminosity, low mass, and small size. Astronomers ordinarily discover them as companions to larger galaxies. It is expected that large galaxies observed today are formed either by collisions of dwarf galaxies or by larger galaxies attracting material away from these dwarfs.
Using an amateur 0.14-m aperture telescope, astronomers have observed a nearby spiral galaxy known as M63 (or NGC 5055). The observations identified five faint dwarf galaxies around M63 and allowed the researchers to determine their basic parameters.
Until now, astronomers have detected numerous dwarf galaxies in the neighborhood of M63 that may be satellites of this galaxy.
A team of astronomers led by Igor Karachentsev of the Special Astrophysical Observatory (SAO) in Russia has added more objects to this list. By inspecting an image obtained with the 0.14-m aperture refractor TEC140ED APO at f/7 focal ratio using a Moravian G3-16200 Monochrom CCD (KAF-16200) camera, they found five new candidates for M63 satellites of very low surface brightness.
Astronomers noted, “We present a deep (50 hours exposed) image of the nearby spiral galaxy M63 (NGC 5055), taken with a 0.14-m aperture telescope. (…) We found five very low-surface-brightness dwarf galaxies around M63.”
The newly found dwarf galaxies received designations TBGdw3 to TBGdw7. The median absolute B-magnitude of these galaxies is –8.8 mag, and they have a median surface brightness of about 27.8 mag/sq. arcsec.
Two objects TBGdw7 and TBGdw3, are the largest- they have maximum angular diameters of approximately 21.7 and 21.6 arcmin. TBGdw6 is the smallest one- it has a maximum angular diameter of some 18.5 arcmins. The status of TBGdw6 needs further confirmation as there is a possibility that it may be a patch of reflecting nebulae.
TBGdw5 is the nearest dwarf to M63, with a linear projected separation of about 283,600 light-years from this galaxy. The most distant from M63 was found to be TBGdw4 – the separation is approximately 394,500 light-years.
- Karachentsev et al., New dwarfs around the curly spiral galaxy M63, arXiv:2011.04984 [astro-ph.GA] arxiv.org/abs/2011.04984