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Title: Light and Color Curve Properties of Type Ia Supernovae: Theory Versus Observations

Abstract

We study the optical light curve (LC) relations of Type Ia supernovae (SNe Ia) for their use in cosmology using high-quality photometry published by the Carnegie Supernova Project (CSP-I). We revisit the classical luminosity decline rate (Δ m {sub 15}) relation and the Lira relation, as well as investigate the time evolution of the ( B − V ) color and B ( B − V ), which serves as the basis of the color–stretch relation and Color–MAgnitude Intercept Calibrations (CMAGIC). Our analysis is based on explosion and radiation transport simulations for spherically symmetric delayed-detonation models (DDT) producing normal-bright and subluminous SNe Ia. Empirical LC relations can be understood as having the same physical underpinnings, i.e., opacities, ionization balances in the photosphere, and radioactive energy deposition changing with time from below to above the photosphere. Some three to four weeks past maximum, the photosphere recedes to {sup 56}Ni-rich layers of similar density structure, leading to a similar color evolution. An important secondary parameter is the central density ρ {sub c} of the WD because at higher densities, more electron-capture elements are produced at the expense of {sup 56}Ni production. This results in a Δ m {sub 15} spread of 0.1more » mag in normal-bright and 0.7 mag in subluminous SNe Ia and ≈0.2 mag in the Lira relation. We show why color–magnitude diagrams emphasize the transition between physical regimes and enable the construction of templates that depend mostly on Δ m {sub 15} with little dispersion in both the CSP-I sample and our DDT models. This allows intrinsic SN Ia variations to be separated from the interstellar reddening characterized by E ( B − V ) and R {sub B}. Invoking different scenarios causes a wide spread in empirical relations, which may suggest one dominant scenario.« less

Authors:
;  [1];  [2];  [3];  [4];  [5];  [6];  [7]; ; ;  [8]; ;  [9]
  1. Department of Physics, Florida State University, Tallahassee, FL 32306 (United States)
  2. Astrophysics Research Institute, Liverpool John Moore University, 146 Brownlow Hill, Liverpool L3 5RF (United Kingdom)
  3. Observatories of the Carnegie Institution for Science, 813 Santa Barbara St., Pasadena, CA 91101 (United States)
  4. NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States)
  5. Carnegie Observatories, Las Campanas Observatory, Casilla 601 La Serena (Chile)
  6. Physics and Astronomy Department, Texas Tech University, Box 41051, Lubbock, TX 79409-1051 (United States)
  7. Department of Physics and Astronomy, Aarhus University, Ny Munkegade 120, DK-8000, Aarhus (Denmark)
  8. The G.P. and C. Woods Mitchell Institute for Fundamental Physics and Astronomy, Texas A and M University, Department of Physics and Astronomy, 4242 TAMU, College Station, TX 77843 (United States)
  9. Departamento de Física, Universidad Técnica Federico Santa Maria, Ava España 1680, Casilla 110-V, Valparaiso (Chile)
Publication Date:
OSTI Identifier:
22663171
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 846; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; COSMOLOGY; DENSITY; DISPERSIONS; ELECTRON CAPTURE; ELECTRONS; ENERGY ABSORPTION; ENERGY LOSSES; IONIZATION; LAYERS; LUMINOSITY; NICKEL 56; OPACITY; PHOTOMETRY; PHOTOSPHERE; RADIANT HEAT TRANSFER; RADIATION TRANSPORT; SIMULATION; SYMMETRY; TYPE I SUPERNOVAE

Citation Formats

Hoeflich, P., Hsiao, E. Y., Ashall, C., Burns, C. R., Diamond, T. R., Phillips, M. M., Sand, D., Stritzinger, M. D., Suntzeff, N., Krisciunas, K., Wang, L., Contreras, C., and Morrell, N., E-mail: phoeflich77@gmail.com. Light and Color Curve Properties of Type Ia Supernovae: Theory Versus Observations. United States: N. p., 2017. Web. doi:10.3847/1538-4357/AA84B2.
Hoeflich, P., Hsiao, E. Y., Ashall, C., Burns, C. R., Diamond, T. R., Phillips, M. M., Sand, D., Stritzinger, M. D., Suntzeff, N., Krisciunas, K., Wang, L., Contreras, C., & Morrell, N., E-mail: phoeflich77@gmail.com. Light and Color Curve Properties of Type Ia Supernovae: Theory Versus Observations. United States. doi:10.3847/1538-4357/AA84B2.
Hoeflich, P., Hsiao, E. Y., Ashall, C., Burns, C. R., Diamond, T. R., Phillips, M. M., Sand, D., Stritzinger, M. D., Suntzeff, N., Krisciunas, K., Wang, L., Contreras, C., and Morrell, N., E-mail: phoeflich77@gmail.com. Fri . "Light and Color Curve Properties of Type Ia Supernovae: Theory Versus Observations". United States. doi:10.3847/1538-4357/AA84B2.
@article{osti_22663171,
title = {Light and Color Curve Properties of Type Ia Supernovae: Theory Versus Observations},
author = {Hoeflich, P. and Hsiao, E. Y. and Ashall, C. and Burns, C. R. and Diamond, T. R. and Phillips, M. M. and Sand, D. and Stritzinger, M. D. and Suntzeff, N. and Krisciunas, K. and Wang, L. and Contreras, C. and Morrell, N., E-mail: phoeflich77@gmail.com},
abstractNote = {We study the optical light curve (LC) relations of Type Ia supernovae (SNe Ia) for their use in cosmology using high-quality photometry published by the Carnegie Supernova Project (CSP-I). We revisit the classical luminosity decline rate (Δ m {sub 15}) relation and the Lira relation, as well as investigate the time evolution of the ( B − V ) color and B ( B − V ), which serves as the basis of the color–stretch relation and Color–MAgnitude Intercept Calibrations (CMAGIC). Our analysis is based on explosion and radiation transport simulations for spherically symmetric delayed-detonation models (DDT) producing normal-bright and subluminous SNe Ia. Empirical LC relations can be understood as having the same physical underpinnings, i.e., opacities, ionization balances in the photosphere, and radioactive energy deposition changing with time from below to above the photosphere. Some three to four weeks past maximum, the photosphere recedes to {sup 56}Ni-rich layers of similar density structure, leading to a similar color evolution. An important secondary parameter is the central density ρ {sub c} of the WD because at higher densities, more electron-capture elements are produced at the expense of {sup 56}Ni production. This results in a Δ m {sub 15} spread of 0.1 mag in normal-bright and 0.7 mag in subluminous SNe Ia and ≈0.2 mag in the Lira relation. We show why color–magnitude diagrams emphasize the transition between physical regimes and enable the construction of templates that depend mostly on Δ m {sub 15} with little dispersion in both the CSP-I sample and our DDT models. This allows intrinsic SN Ia variations to be separated from the interstellar reddening characterized by E ( B − V ) and R {sub B}. Invoking different scenarios causes a wide spread in empirical relations, which may suggest one dominant scenario.},
doi = {10.3847/1538-4357/AA84B2},
journal = {Astrophysical Journal},
number = 1,
volume = 846,
place = {United States},
year = {Fri Sep 01 00:00:00 EDT 2017},
month = {Fri Sep 01 00:00:00 EDT 2017}
}
  • We present an updated version of the Multicolor Light Curve Shape method to measure distances to type Ia supernovae (SN Ia), incorporating new procedures for K-correction and extinction corrections. We also develop a simple model to disentangle intrinsic color variations and reddening by dust, and expand the method to incorporate U-band light curves and to more easily accommodate prior constraints on any of the model parameters. We apply this method to 133 nearby SN Ia, including 95 objects in the Hubble flow (cz {ge} 2500 km s{sup -1}), which give an intrinsic dispersion of less than 7% in distance. Themore » Hubble flow sample, which is of critical importance to all cosmological uses of SN Ia, is the largest ever presented with homogeneous distances. We find the Hubble flow supernovae with H{sub 0}d{sub SN} {ge} 7400 km s{sup -1} yield an expansion rate that is 6.5 {+-} 1.8% lower than the rate determined from supernovae within that distance, and this can have a large effect on measurements of the dark energy equation of state with SN Ia. Peculiar velocities of SN Ia host galaxies in the rest frame of the Local Group are consistent with the dipole measured in the Cosmic Microwave Background. Direct fits of SN Ia that are significantly reddened by dust in their host galaxies suggest their mean extinction law may be described by R{sub V} {approx_equal} 2.7, but optical colors alone provide weak constraints on R{sub V}.« less
  • Observational data are presented in support of the hypothesis that background galaxy contamination is present in the photometric data of Ia supernovae and that this effect can account for the observed dispersion in the light curve speeds of most of Ia supernovae. The implication is that the observed dispersion in beta is artificial and that most of Ia supernovae have nearly homogeneous light curves. The result supports the notion that Ia supernovae are good standard candles. 26 refs.
  • We show empirically that fits to the color-magnituderelation of Type Ia supernovae after optical maximum can provide accuraterelative extragalactic distances. We report the discovery of an empiricalcolor relation for Type Ia light curves: During much of the first monthpast maximum, the magnitudes of Type Ia supernovae defined at a givenvalue of color index have a very small magnitude dispersion; moreover,during this period the relation between B magnitude and B-V color (or B-Ror B-I color) is strikingly linear, to the accuracy of existingwell-measured data. These linear relations can provide robust distanceestimates, in particular, by using the magnitudes when the supernovareaches amore » given color. After correction for light curve stretch factor ordecline rate, the dispersion of the magnitudes taken at the intercept ofthe linear color-magnitude relation are found to be around 0^m .08 forthe sub-sample of supernovae with (B_max - V_max) ?= 0^m 0.5, andaround 0^m.11 for the sub-sample with (B_max - V_max) ?= 0^m .2.This small dispersion is consistent with being mostly due toobservational errors. The method presented here and the conventionallight curve fitting methods can be combined to further improvestatistical dispersions of distance estimates. It can be combined withthe magnitude at maximum to deduce dust extinction. Theslopes of thecolor-magnitude relation may also be used to identify intrinsicallydifferent SN Ia systems. The method provides a tool that is fundamentalto using SN Ia to estimate cosmological parameters such as the Hubbleconstant and the mass and dark energy content of theuniverse.« less
  • We propose a robust, quantitative method to compare the synthetic light curves of a Type Ia supernova (SN Ia) explosion model with a large set of observed SNe Ia, and derive a figure of merit for the explosion model's agreement with observations. The synthetic light curves are fit with the data-driven model SALT2 which returns values for stretch, color, and magnitude at peak brightness, as well as a goodness-of-fit parameter. Each fit is performed multiple times with different choices of filter bands and epoch range in order to quantify the systematic uncertainty on the fitted parameters. We use a parametricmore » population model for the distribution of observed SN Ia parameters from large surveys, and extend it to represent red, dim, and bright outliers found in a low-redshift SN Ia data set. We discuss the potential uncertainties of this population model and find it to be reliable given the current uncertainties on cosmological parameters. Using our population model, we assign each set of fitted parameters a likelihood of being observed in nature, and a figure of merit based on this likelihood. We define a second figure of merit based on the quality of the light curve fit, and combine the two measures into an overall figure of merit for each explosion model. We compute figures of merit for a variety of one-, two-, and three-dimensional explosion models and show that our evaluation method allows meaningful inferences across a wide range of light curve quality and fitted parameters.« less
  • By the best fitting of all available light curves of Type I supernovae an average curve, representative of the class, was drawn. Due to the strong similarity of the light curves, the dispersion of the points was relatively small. From the analysis of the average curve some general properties of the SN-I were derived. The occurrence of Type I supernovae in different types of galaxies and the possibility of a further subdivision in two groups are discussed. (auth)