Keck observations of the young metal-poor host galaxy of the super-chandrasekhar-mass type Ia supernova SN 2007if

Abstract

We present Keck LRIS spectroscopy and g-band photometry of the metal-poor, low-luminosity host galaxy of the super-Chandrasekhar-mass Type Ia supernova SN 2007if. Deep imaging of the host reveals its apparent magnitude to be m g = 23.15±0.06, which at the spectroscopically measured redshift of z helio = 0.07450±0.00015 corresponds to an absolute magnitude of Mg = -14.45±u0.06. Galaxy g - r color constrains the mass-to-light ratio, giving a host stellar mass estimate of log(M */M⊙) = 7.32±0.17. Balmer absorption in the stellar continuum, along with the strength of the 4000 Å break, constrains the age of the dominant starburst in the galaxy to be t burst = 123+165 -77 Myr, corresponding to a main-sequence turnoff mass of M/M⊙ = 4.6+2.6 -1.4. Using the R 23 method of calculating metallicity from the fluxes of strong emission lines, we determine the host oxygen abundance to be 12 + log(O/H)KK04 = 8.01±0.09, significantly lower than any previously reported spectroscopically measured Type Ia supernova host galaxy metallicity. Our data show that SN 2007if is very likely to have originated from a young, metal-poor progenitor. Show more