Stellar population and dust extinction in an ultraluminous infrared
  galaxy at z=1.135
  We present the detailed optical to far-infrared observations of SST
J1604+4304, an ULIRG at z = 1.135. Analyzing the stellar absorption lines,
namely, the CaII H & K and Balmer H lines in the optical spectrum, we derive
the upper limits of an age for the stellar population. Given this constraint,
the minimum {chi}^2 method is used to fit the stellar population models to the
observed SED from 0.44 to 5.8um. We find the following properties. The stellar
population has an age 40 - 200 Myr with a metallicity 2.5 Z_{sun}. The
starlight is reddened by E(B-V) = 0.8. The reddening is caused by the
foreground dust screen, indicating that dust is depleted in the starburst site
and the starburst site is surrounded by a dust shell. The infrared (8-1000um)
luminosity is L_{ir} = 1.78 +/- 0.63 * 10^{12} L_{sun}. This is two times
greater than that expected from the observed starlight, suggesting either that
1/2 of the starburst site is completely obscured at UV-optical wavelengths, or
that 1/2 of L_{ir} comes from AGN emission. The inferred dust mass is 2.0 +/-
1.0 * 10^8 M_{sun}. This is sufficient to form a shell surrounding the galaxy
with an optical depth E(B-V) = 0.8. From our best stellar population model - an
instantaneous starburst with an age 40 Myr, we infer the rate of 19
supernovae(SNe) per year. Simply analytical models imply that 2.5 Z_{sun} in
stars was reached when the gas mass reduced to 30% of the galaxy mass. The gas
metallcity is 4.8 Z_{sun} at this point. The gas-to-dust mass ratio is then 120
+/- 73. The inferred dust production rate is 0.24 +/- 0.12 M_{sun} per SN. If
1/2 of L_{ir} comes from AGN emission, the rate is 0.48 +/- 0.24 M_{sun} per
SN. We discuss the evolutionary link of SST J1604+4304 to other galaxy
populations in terms of the stellar masses and the galactic winds.
