Is the Dust Obscuring Supernovae in Distant Galaxies the Same as Dust in the Milky Way?

Adam G. Riess,William H. Press,Robert P. Kirshner

doi:10.1086/178174

Adam G. Riess, William H. Press + Show 1 more

Open Access

https://doi.org/10.1086/178174

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Abstract

Previous attempts to correct type Ia supernovae (SN Ia's) for host galaxy extinction have given strange results: increased dispersion on the Hubble diagram or impossibly low values of the reddening ratio for dust in distant galaxies. The cause is the incorrect assumption that SN Ia's have a uniform intrinsic luminosity and color at maximum light. Our multicolor light-curve shape (MLCS) method establishes the relation between intrinsic luminosity and color for SN Ia's using information in light-curve shapes. Here we estimate the B - V, V - R, and V - I color excess for 20 SN Ia's using MLCS and estimate the reddening ratios of dust in distant galaxies. The ratios of selective to total absorption from dust in distant galaxies hosting SN Ia's are consistent with the galactic extinction law. The SN Ia's in late-type galaxies are often obscured by dust, while those in early-type galaxies are dust free. This suggests that SN Ia extinction is caused by interstellar (not circumstellar) dust, with similar optical properties as the dust in the Milky Way.

Highlights

Previous attempts to measure the extinction of Type Ia supernovae (SN IaÏs) have resulted in increased dispersion on the Hubble diagram and extreme properties for dust in distant galaxies
IaÏs that the problem lies with past assumptions that SN IaÏs were standard candles with a uniform luminosity and uniform intrinsic color at maximum light
SN IaÏs have intrinsic variations in color at maximum light that are correlated with variations in peak absolute magnitude

Summary

Introduction

Previous attempts to measure the extinction of Type Ia supernovae (SN IaÏs) have resulted in increased dispersion on the Hubble diagram and extreme properties for dust in distant galaxies. SN IaÏs have intrinsic variations in color at maximum light that are correlated with variations in peak absolute magnitude. When these e†ects are understood, SN IaÏs provide a way to evaluate the properties of interstellar dust in other galaxies. One can solve for the reddening dust obscuring SN IaÏs, if one assumes ratio, that. Bdi[†eVrecnocleorbgetivweeseRnBt.hFeorapSpNarIeanÏst brightness and the apparent brightness predicted by the ermexdectsehhsosifdtisrdgeiiqvvuiedinreedbsykbEnyBo~twhVlee\dcgo(emlooBrf[SexNmceVIs)as[ign(itBvrei[nssViRc)B0c..oTlTohhriesthlcaaottltoeinrr the past has often been taken as the color of the bluest (and presumably most reddened) SN IaÏs observed.

Results

Discussion

Conclusion