The Hidden H I-Massive Luminous Infrared Galaxy HIZOA J0836–43: Inside-Out Galaxy Formation

Abstract

HIZOA J0836–43 is an extreme gas-rich (MH I = 7.5 × 10^10 M☉) 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^−1, arising from exceptionally strong molecular PAH emission (L7.7μ m = 1.50 × 10^9 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) × 10^10 M☉. 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.

Files

Additional details