Bibcode
Bellazzini, M.; Beccari, G.; Oosterloo, T. A.; Galleti, S.; Sollima, A.; Correnti, M.; Testa, V.; Mayer, L.; Cignoni, M.; Fraternali, F.; Gallozzi, S.
Referencia bibliográfica
Astronomy and Astrophysics, Volume 527, id.A58
Fecha de publicación:
3
2011
Revista
Número de citas
29
Número de citas referidas
26
Descripción
We present a detailed study of the dwarf galaxy VV124 (UGC4879),
recently recognized as a remarkably isolated member of the Local Group.
We have obtained deep (r ≃ 26.5) wide-field (23' × 23') g,r
photometry of individual stars with the LBC camera at the Large
Binocular Telescope under sub-arcsec seeing conditions. The
color-magnitude diagram suggests that the stellar content of the galaxy
is dominated by an old, metal-poor population, with a significant
metallicity spread. A very clean detection of the RGB tip allows us to
derive an accurate distance of D = 1.3 ± 0.1 Mpc. Combining
surface photometry with star counts, we are able to trace the surface
brightness profile of VV124 out to ~5' ≃ 1.9 kpc radius (where
μr ≃ 30 mag/arcsec2), showing that it is
much more extended than previously believed. Moreover, the surface
density map reveals the presence of two symmetric flattened wings
emanating from the central elongated spheroid and aligned with its major
axis, resembling a stellar disk seen nearly edge-on. We also present H i
observations obtained with the Westerbork Synthesis Radio Telescope
(WSRT), the first ever of this object. A total amount of ≃
106 M&sun; of H i gas is detected in VV124.
Compared to the total luminosity, this gives a value of
MHI/LV = 0.11, which is particularly low for
isolated Local Group dwarfs. The spatial distribution of the gas does
not correlate with the observed stellar wings. The systemic velocity of
the H i in the region superposed to the stellar main body of the galaxy
is Vh = -25 km s-1. The velocity field shows
substructures typical of galaxies of this size but no sign of rotation.
The H i spectra indicates the presence of a two-phase interstellar
medium, again typical of many dwarf galaxies.