Bibcode
Trujillo, I.; Roman, J.; Filho, M.; Sánchez Almeida, J.
Bibliographical reference
The Astrophysical Journal, Volume 836, Issue 2, article id. 191, 6 pp. (2017).
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2
2017
Journal
Citations
81
Refereed citations
76
Description
We describe the structural, stellar population and gas properties of the
nearest ultra diffuse galaxy discovered so far: UGC 2162 (z = 0.00392
{R}e,g=1.7(+/- 0.2) kpc; {μ }g(0) = 24.4
± 0.1 mag arcsec‑2 g-i = 0.33 ± 0.02).
This galaxy, located at a distance of 12.3(±1.7) Mpc, is a member
of the M77 group. UGC 2162 has a stellar mass of ∼
2{(}-1+2) × 107 {M}ȯ
and is embedded within a cloud of HI gas ∼10 times more
massive: ∼1.9(±0.6) × 108 {M}ȯ
. Using the width of its HI line as a dynamical proxy, the
enclosed mass within the inner R ∼ 5 kpc is ∼4.6(±0.8)
× 109 {M}ȯ (i.e., M/L ∼ 200). The
estimated virial mass from the cumulative mass curve is
∼8(±2)×1010 M ⊙. Ultra-deep
imaging from the IAC Stripe82 Legacy Project show that the galaxy is
irregular and has many star-forming knots, with a gas-phase metallicity
around one-third of the solar value. Its estimated star-formation rate
is ∼0.01 {M}ȯ yr‑1. This SFR would
double the stellar mass of the object in ∼2 Gyr. If the object were
to stop forming stars at this moment, after a passive evolution, its
surface brightness would become extremely faint: {μ }g(0)
∼ 27 mag arcsec‑2 and its size would remain large
{R}e,g ∼ 1.8 kpc. Such faintness would make it almost
undetectable to most present-day surveys. This suggests that there could
be an important population of {M}\star ∼ 107
{M}ȯ “dark galaxies” in rich environments
(depleted of HI gas) waiting to be discovered by current and future
ultra-deep surveys.
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