VV124 (UGC4879): a new transitional dwarf galaxy in the periphery of the Local Group

Kopylov, A. I.; Tikhonov, N. A.; Fabrika, S.; Drozdovsky, I.; Valeev, A. F.
Bibliographical reference

Monthly Notices of the Royal Astronomical Society: Letters, Volume 387, Issue 1, pp. L45-L49.

Advertised on:
6
2008
Number of authors
5
IAC number of authors
1
Citations
21
Refereed citations
19
Description
We present the first photometry of individual stars within VV124 (UGC4879) and find that this is the most isolated dwarf galaxy in the periphery of the Local Group. This work is based on imaging and spectroscopic follow-up observations with the 6-m BTA telescope; we resolve VV124 into 1560 stars down to the limiting magnitude levels of V ~= 25.6 and I ~= 23.9. Young blue stellar populations and ionized gas are found near the core, but notably displaced from the centre of the galaxy as traced by dominant evolved red stars. The mean heliocentric radial velocity derived from the spectra of two blue supergiant stars and unresolved continuum sources is -70 +/- 15kms-1. The evolved `red tangle' stellar populations, which contain the red giant branch (RGB), are identified at large galactocentric radii. We use the I-band luminosity function to determine the distance based on the Tip of RGB method, 1.1 +/- 0.1Mpc. This is ~10 times closer than the values usually assumed in the literature, and we provide revised distance-dependent parameters. From the mean (V - I) colour of the RGB, we estimate the mean metallicity as [Fe/H] ~= -1.37 dex. Despite its isolated location, the properties of VV124 are clearly not those of a galaxy in formation, but rather similar to a transitional dIrr/dSph type.
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NGC 2808 Globular Cluster
Milky Way and Nearby Galaxies
The general aim of the project is to research the structure, evolutionary history and formation of galaxies through the study of their resolved stellar populations, both from photometry and spectroscopy. The group research concentrates in the most nearby objects, namely the Local Group galaxies including the Milky Way and M33 under the hypothesis