Far-infrared star-formation rates of six GRB host galaxies with ALMA
  Gamma-Ray Bursts (GRBs) can be a promising tracer of cosmic star-formation
rate history (CSFRH). In order to reveal the CSFRH using GRBs, it is important
to understand whether they are biased tracers or not. For this purpose, it is
crucial to understand properties of GRB host galaxies, in comparison to field
galaxies. In this work, we report ALMA far-infrared (FIR) observations of six
$z\sim2$ IR-bright GRB host galaxies, which are selected for the brightness in
IR. Among them, four host galaxies are detected for the first time in the
rest-frame FIR. In addition to the ALMA data, we collected multi-wavelength
data from previous studies for the six GRB host galaxies. Spectral energy
distribution (SED) fitting analyses were performed with \texttt{CIGALE} to
investigate physical properties of the host galaxies, and to test whether
active galactic nucleus (AGN) and radio components are required or not. Our
results indicate that the best-fit templates of five GRB host galaxies do not
require an AGN component, suggesting the absence of AGNs. One GRB host galaxy,
080207, shows a very small AGN contribution. While derived stellar masses of
the three host galaxies are mostly consistent with those in previous studies,
interestingly the value of star-formation rates (SFRs) of all six GRB hosts are
inconsistent with previous studies. Our results indicate the importance of
rest-frame FIR observations to correctly estimate SFRs by covering thermal
emission from cold dust heated by star formation.
