The hidden H i-massive luminous infrared galaxy HIZOA J0836-43: inside-out galaxy formation.
CLUVER M.E., JARRETT T.H., APPLETON P.N., KRAAN-KORTEWEG R.C., WOUDT P.A., KORIBALSKI B.S., DONLEY J.L., WAKAMATSU K. and NAGAYAMA T.
Abstract (from CDS):
HIZOA J0836-43 is an extreme gas-rich (M_HI_= 7.5x1010M☉) disk galaxy which lies hidden behind the strongly obscuring Vela region of the Milky Way. Utilizing observations from the Spitzer Space Telescope, we have found it to be a luminous infrared starburst galaxy with a star formation rate of ∼21 M☉/yr, arising from exceptionally strong molecular PAH emission (L7.7µm=1.50x109 L☉) and far-infrared emission from cold dust. The galaxy exhibits a weak mid-infrared continuum compared to other star-forming galaxies and U/LIRGs. This relative lack of emission from small grains suggests atypical interstellar medium conditions compared to other starbursts. We do not detect significant [Ne V] or [O IV], which implies an absent or very weak AGN. The galaxy possesses a prominent bulge of evolved stars and a stellar mass of 4.4(±1.4)x1010M☉. With its plentiful gas supply and current star formation rate, a doubling of stellar mass would occur on a timescale of ∼2 Gyr. Compared to local galaxies, HIZOA J0836-43 appears to be a ``scaled up'' spiral undergoing inside-out formation, possibly resembling stellar disk building processes at intermediate redshifts.