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Title: Improved Distances to Type Ia Supernovae withMulticolor Light Curve Shapes: MLCS2k2

Abstract

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. The 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 Cosmicmore » 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

Authors:
; ; ; ; ;
Publication Date:
Research Org.:
Stanford Linear Accelerator Center (SLAC)
Sponsoring Org.:
USDOE
OSTI Identifier:
896923
Report Number(s):
SLAC-PUB-12273
TRN: US200705%%69
DOE Contract Number:
AC02-76SF00515
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; COLOR; DIPOLES; DUSTS; GALAXIES; RELICT RADIATION; SHAPE; SUPERNOVAE; ASTROPHYSICS; Astrophysics,ASTRO

Citation Formats

Jha, Saurabh, /KIPAC, Menlo Park, Riess, Adam G., /Baltimore, Space Telescope Sci., Kirshner, Robert P., and /Harvard-Smithsonian Ctr. Astrophys. Improved Distances to Type Ia Supernovae withMulticolor Light Curve Shapes: MLCS2k2. United States: N. p., 2007. Web. doi:10.1086/512054.
Jha, Saurabh, /KIPAC, Menlo Park, Riess, Adam G., /Baltimore, Space Telescope Sci., Kirshner, Robert P., & /Harvard-Smithsonian Ctr. Astrophys. Improved Distances to Type Ia Supernovae withMulticolor Light Curve Shapes: MLCS2k2. United States. doi:10.1086/512054.
Jha, Saurabh, /KIPAC, Menlo Park, Riess, Adam G., /Baltimore, Space Telescope Sci., Kirshner, Robert P., and /Harvard-Smithsonian Ctr. Astrophys. Fri . "Improved Distances to Type Ia Supernovae withMulticolor Light Curve Shapes: MLCS2k2". United States. doi:10.1086/512054. https://www.osti.gov/servlets/purl/896923.
@article{osti_896923,
title = {Improved Distances to Type Ia Supernovae withMulticolor Light Curve Shapes: MLCS2k2},
author = {Jha, Saurabh and /KIPAC, Menlo Park and Riess, Adam G. and /Baltimore, Space Telescope Sci. and Kirshner, Robert P. and /Harvard-Smithsonian Ctr. Astrophys.},
abstractNote = {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. The 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}.},
doi = {10.1086/512054},
journal = {Astrophysical Journal},
number = ,
volume = ,
place = {United States},
year = {Fri Jan 05 00:00:00 EST 2007},
month = {Fri Jan 05 00:00:00 EST 2007}
}
  • We study the observables of 158 relatively normal Type Ia supernovae (SNe Ia) by dividing them into two groups in terms of the expansion velocity inferred from the absorption minimum of the Si II {lambda}6355 line in their spectra near B-band maximum brightness. One group ('Normal') consists of normal SNe Ia populating a narrow strip in the Si II velocity distribution, with an average expansion velocity (v) = 10, 600 {+-} 400 km s{sup -1} near B maximum; the other group ('HV') consists of objects with higher velocities, v {approx}> 11, 800 km s{sup -1}. Compared with the Normal group,more » the HV one shows a narrower distribution in both the peak luminosity and the luminosity decline rate {delta}m {sub 15}. In particular, their B-V colors at maximum brightness are found to be on average redder by {approx} 0.1 mag, suggesting that they either are associated with dusty environments or have intrinsically red B-V colors. The HV SNe Ia are also found to prefer a lower extinction ratio R{sub V} {approx} 1.6 (versus {approx} 2.4 for the Normal ones). Applying such an absorption-correction dichotomy to SNe Ia of these two groups remarkably reduces the dispersion in their peak luminosity from 0.178 mag to only 0.125 mag.« 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 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 andmore » 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.« less
  • We present an empirical method that measures the distance to a Type Ia supernova (SN Ia) with a precision of {approximately}10{percent} from a single night`s data. This method measures the supernova`s age and luminosity/light-curve parameter from a spectrum and the extinction and distance from an apparent magnitude and color. We are able to verify the precision of this method from error propagation calculations, Monte Carlo simulations of well-sampled SNe Ia, and the Hubble diagram of sparsely observed supernovae. With the reduction in telescope time needed, this method is 3{endash}4 times more efficient for measuring cosmological parameters than conventional light-curve{endash}based distancemore » estimates. {copyright} {ital {copyright} 1998.} {ital The American Astronomical Society}« less
  • No abstract prepared.