Host Galaxy Mass Combined with Local Stellar Age Improve Type Ia Supernovae Distances

Abstract

Type Ia supernovae (SNe Ia) are standardizable candles, but for over a decade, there has been a debate on how to properly account for their correlations with host galaxy properties. Using the Bayesian hierarchical model UNITY, we simultaneously fit for the SN Ia light curve and host galaxy standardization parameters on a set of 103 Sloan Digital Sky Survey II SNe Ia. We investigate the influences of host stellar mass, along with both localized ($r<3$ kpc) and host-integrated average stellar ages, derived from stellar population synthesis modeling. We find that the standardization for the light-curve shape ($\alpha$) is correlated with host galaxy standardization terms (${\gamma }_i$) requiring simultaneous fitting. In addition, we find that these correlations themselves are dependent on host galaxy stellar mass that includes a shift in the color term ($\beta$) of $0.8\mathrm{mag}$, only significant at $1.2\sigma$ due to the small sample. We find a linear host mass standardization term at the $3.7\sigma$ level, that by itself does not significantly improve the precision of an individual SN Ia distance. However, a standardization that uses both stellar mass and average local stellar age is found to be significant at $>3\sigma$ in the two-dimensional posterior space. In addition, the unexplained scatter of SNe Ia absolute magnitude post standardization, is reduced from $0.122_{-0.018}^{+0.019}$ to $0.109\pm 0.017$ mag, or $\sim 10\%$. We do not see similar improvements when using global ages. This combination is consistent with either metallicity or line-of-sight dust affecting the observed luminosity of SNe Ia.

13 pages, 6 figures, submitted to ApJ

References in corpus (12)

• The NumPy array: a structure for efficient numerical computation
• The propagation of uncertainties in stellar population synthesis modeling I: The relevance of uncertain aspects of stellar evolution and the IMF to the derived physical properties of galaxies
• Some Aspects of Measurement Error in Linear Regression of Astronomical Data
• Improved Distances to Type Ia Supernovae with Multicolor Light Curve Shapes: MLCS2k2
• The Sloan Digital Sky Survey-II Supernova Survey: Search Algorithm and Follow-up Observations
• Ages of Type Ia Supernovae Over Cosmic Time
• Early-type Host Galaxies of Type Ia Supernovae. II. Evidence for Luminosity Evolution in Supernova Cosmology
• Is the expansion of the universe accelerating? All signs point to yes
• Think Global, Act Local: The Influence of Environment Age and Host Mass on Type Ia Supernova Light Curves
• The influence of Host Galaxies in Type Ia Supernova Cosmology
• Delay Time Distributions of Type Ia Supernovae From Galaxy and Cosmic Star Formation Histories
• Initial Evaluation of SNEMO2 and SNEMO7 Standardization Derived From Current Light Curves of Type Ia Supernovae

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