Characterizing dw1335-29, a recently discovered dwarf satellite of M83
  The number, distribution, and properties of dwarf satellites are crucial
probes of the physics of galaxy formation at low masses and the response of
satellite galaxies to the tidal and gas dynamical effects of their more massive
parent.To make progress, it is necessary to augment and solidify the census of
dwarf satellites of galaxies outside the Local Group. M\"uller et al. (2015)
presented 16 dwarf galaxy candidates near M83, but lacking reliable distances,
it is unclear which candidates are M83 satellites. Using red giant branch stars
from the HST/GHOSTS survey in conjunction with ground-based images from
VLT/VIMOS, we confirm that one of the candidates, dw1335-29-- with a projected
distance of 26 kpc from M83 and a distance modulus of $(m - M)_0 =
28.5^{+0.3}_{-0.1}$ -- is a satellite of M83. We estimate an absolute magnitude
$M_V = -10.1 \pm{0.4}$, an ellipticity of $0.40^{+0.14}_{-0.22}$, a half light
radius of $656^{+121}_{-170 }$ pc, and [Fe/H] = $-1.3^{+0.3}_{-0.4}$. Owing to
dw1335-29's somewhat irregular shape and possible young stars, we classify this
galaxy as a dwarf irregular or transition dwarf. This is curious, as with a
projected distance of 26 kpc from M83, dw1335-29 is expected to lack recent
star formation. Further study of M83's dwarf population will reveal if star
formation in its satellites is commonplace (suggesting a lack of a hot gas
envelope for M83 that would quench star formation) or rare (suggesting that
dw1335-29 has a larger M83-centric distance, and is fortuitously projected to
small radii).
