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Astrophysical Journal 733 (2011) 3
Keck Observations of the Young Metal-Poor Host Galaxy of the Super-Chandrasekhar-Mass Type Ia Supernova SN 2007if
M. Childress, G. Aldering, C. Aragon, P. Antilogus1, S. Bailey, C. Baltay, S. Bongard1, C. Buton, A. Canto1, N. Chotard2, Y. Copin2, H. K. Fakhouri, E. Gangler2, M. Kerschhaggl, M. Kowalski, E. Y. Hsiao, S. Loken, P. Nugent, K. Paech, R. Pain1, E. Pecontal3, R. Pereira2, S. Perlmutter, D. Rabinowitz, K. Runge, R. Scalzo, R. C. Thomas, G. Smadja2, C. Tao4, B. A. Weaver, C. Wu1

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 $m_g=23.15\pm0.06$, which at the spectroscopically-measured redshift of $z_{helio}=0.07450\pm0.00015$ corresponds to an absolute magnitude of $M_g=-14.45\pm0.06$. Galaxy $g-r$ color constrains the mass-to-light ratio, giving a host stellar mass estimate of $\log(M_*/M_\odot)=7.32\pm0.17$. Balmer absorption in the stellar continuum, along with the strength of the 4000Å\ break, constrain the age of the dominant starburst in the galaxy to be $t_\mathrm{burst}=123^{+165}_{-77}$ Myr, corresponding to a main-sequence turn-off mass of $M/M_\odot=4.6^{+2.6}_{-1.4}$. Using the R$_{23}$ method of calculating metallicity from the fluxes of strong emission lines, we determine the host oxygen abundance to be $12+\log(O/H)_\mathrm{KK04}=8.01\pm0.09$, 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.
1 :  LPNHE - Laboratoire de Physique Nucléaire et de Hautes Énergies
2 :  IPNL - Institut de Physique Nucléaire de Lyon
3 :  CRAL - Centre de Recherche Astrophysique de Lyon
4 :  CPPM - Centre de Physique des Particules de Marseille
Physique/Astrophysique/Astrophysique galactique

Planète et Univers/Astrophysique/Astrophysique galactique
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