Hubble Space Telescope Captures UGC 12591: Bulge/Disk Properties, Star
  Formation and `Missing Baryons' Census in a Very Massive and Fast Spinning
  Hybrid Galaxy
  We present Hubble Space Telescope (HST) observations of the nearby (z=
0.023), very massive, highly rotating (488.4$\pm 12.5$ $\kms$) hybrid (S0-Sa)
galaxy UGC~12591, along with observations taken at other wavelengths from UV to
FIR. Deep HST data of the galaxy in V, I and H bands is used to disentangle its
bulge and disk components. The surface brightness distributions show a
dominance of the bulge component over the disk with H-band bulge-to-disc
luminosity ratio $\sim 69\%$. From spectral energy distribution (SED) fitting,
we find an extremely low global star formation rate (SFR) of $\rm \sim 0.1 -
0.2 \Msun y^{-1}$, which is unusually low for this galaxy's huge stellar mass
($\rm M_{\star} \sim 1.6 \times 10^{11} \, \Msun$), that implies a strong
quenching of it's SFR. For at least past $\rm 10^{8}$ years the galaxy has
remained in the quiescent state as a sterile, `red and dead' galaxy. The
fraction of total infra-red dust luminosity contributed by the ISM dust is as
high as $\rm \sim 90\%$, with total dust luminosity $\rm L_{dust} = (0.5-3.5)
\times 10^{10} \Lsun$, dominated by cold dust at equilibrium temperature $\rm
T_{C} \approx 15 K$. UGC~12591 is found host to a super massive black hole
(SMBH) of mass $\rm 6.18\times 10^{8} M_{\sun}$ which at the present moment is
quiescent, i.e., neither we see large ($\rm > 1 kpc$) radio jets nor is the
black hole contributing significantly to the mid-IR SED, ruling out the
presence of strong radiative feedback from a bright AGN.We have obtained a
detailed census of all observable baryons in this galaxy. The star formation
efficiency is very low ($\sim 0.02-0.06$) and within a virial radius the galaxy
has a total observed baryonic mass of $6.87\times10^{11}~\Msun$, amounting to a
baryonic deficiency of $\sim$ $80\%$ relative to the cosmological mean.
