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The Type Ia Supernova Color-Magnitude Relation and Host Galaxy Dust: A Simple Hierarchical Bayesian Model

Publication ,  Journal Article
Mandel, KS; Scolnic, DM; Shariff, H; Foley, RJ; Kirshner, RP
Published in: Astrophysical Journal
June 20, 2017

Conventional Type Ia supernova (SN Ia) cosmology analyses currently use a simplistic linear regression of magnitude versus color and light curve shape, which does not model intrinsic SN Ia variations and host galaxy dust as physically distinct effects, resulting in low color-magnitude slopes. We construct a probabilistic generative model for the dusty distribution of extinguished absolute magnitudes and apparent colors as the convolution of an intrinsic SN Ia color-magnitude distribution and a host galaxy dust reddening-extinction distribution. If the intrinsic color-magnitude (M B versus B - V) slope βint differs from the host galaxy dust law R B, this convolution results in a specific curve of mean extinguished absolute magnitude versus apparent color. The derivative of this curve smoothly transitions from βint in the blue tail to R B in the red tail of the apparent color distribution. The conventional linear fit approximates this effective curve near the average apparent color, resulting in an apparent slope βapp between βint and R B. We incorporate these effects into a hierarchical Bayesian statistical model for SN Ia light curve measurements, and analyze a data set of SALT2 optical light curve fits of 248 nearby SNe Ia at z < 0.10. The conventional linear fit gives βapp ≈ 3. Our model finds βint = 2.3 ± 0.3 and a distinct dust law of RB = 3.8 ± 0.3, consistent with the average for Milky Way dust, while correcting a systematic distance bias of ∼0.10 mag in the tails of the apparent color distribution. Finally, we extend our model to examine the SN Ia luminosity-host mass dependence in terms of intrinsic and dust components.

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Published In

Astrophysical Journal

DOI

EISSN

1538-4357

ISSN

0004-637X

Publication Date

June 20, 2017

Volume

842

Issue

2

Related Subject Headings

  • Astronomy & Astrophysics
  • 5109 Space sciences
  • 5107 Particle and high energy physics
  • 5101 Astronomical sciences
  • 0306 Physical Chemistry (incl. Structural)
  • 0202 Atomic, Molecular, Nuclear, Particle and Plasma Physics
  • 0201 Astronomical and Space Sciences
 

Citation

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Mandel, K. S., Scolnic, D. M., Shariff, H., Foley, R. J., & Kirshner, R. P. (2017). The Type Ia Supernova Color-Magnitude Relation and Host Galaxy Dust: A Simple Hierarchical Bayesian Model. Astrophysical Journal, 842(2). https://doi.org/10.3847/1538-4357/aa6038
Mandel, K. S., D. M. Scolnic, H. Shariff, R. J. Foley, and R. P. Kirshner. “The Type Ia Supernova Color-Magnitude Relation and Host Galaxy Dust: A Simple Hierarchical Bayesian Model.” Astrophysical Journal 842, no. 2 (June 20, 2017). https://doi.org/10.3847/1538-4357/aa6038.
Mandel KS, Scolnic DM, Shariff H, Foley RJ, Kirshner RP. The Type Ia Supernova Color-Magnitude Relation and Host Galaxy Dust: A Simple Hierarchical Bayesian Model. Astrophysical Journal. 2017 Jun 20;842(2).
Mandel, K. S., et al. “The Type Ia Supernova Color-Magnitude Relation and Host Galaxy Dust: A Simple Hierarchical Bayesian Model.” Astrophysical Journal, vol. 842, no. 2, June 2017. Scopus, doi:10.3847/1538-4357/aa6038.
Mandel KS, Scolnic DM, Shariff H, Foley RJ, Kirshner RP. The Type Ia Supernova Color-Magnitude Relation and Host Galaxy Dust: A Simple Hierarchical Bayesian Model. Astrophysical Journal. 2017 Jun 20;842(2).
Journal cover image

Published In

Astrophysical Journal

DOI

EISSN

1538-4357

ISSN

0004-637X

Publication Date

June 20, 2017

Volume

842

Issue

2

Related Subject Headings

  • Astronomy & Astrophysics
  • 5109 Space sciences
  • 5107 Particle and high energy physics
  • 5101 Astronomical sciences
  • 0306 Physical Chemistry (incl. Structural)
  • 0202 Atomic, Molecular, Nuclear, Particle and Plasma Physics
  • 0201 Astronomical and Space Sciences