Abstract
We have measured the rest-frame B,V, and I-band light curves of a high-redshift type Ia supernova (SN Ia), SN 1999Q (z=0.46), using HST and ground-based near-infrared detectors. A goal of this study is the measurement of the color excess, E_{B-I}, which is a sensitive indicator of interstellar or intergalactic dust which could affect recent cosmological measurements from high-redshift SNe Ia. Our observations disfavor a 30% opacity of SN Ia visual light by dust as an alternative to an accelerating Universe. This statement applies to both Galactic-type dust (rejected at the 3.4 sigma confidence level) and greyer dust (grain size > 0.1 microns; rejected at the 2.3 to 2.6 sigma confidence level) as proposed by Aguirre (1999). The rest-frame $I$-band light cur ve shows the secondary maximum a month after B maximum typical of nearby SNe Ia of normal luminosi ty, providing no indication of evolution as a function of redshift out to z~0.5. A n expanded set of similar observations could improve the constraints on any contribution of extragalactic dust to the dimming of high-redshift SNe Ia.
Highlights
Recent observations of high-redshift (z [ 0.3) Type Ia supernovae (SNe Ia) provide the backbone of the body of evidence that we live in an accelerating universe whose content is dominated by vacuum energy (Riess et al 1998 ; Perlmutter et al 1999)
Care was taken to maintain a detected sky Ñux level of D10,000 counts, a regime in which both Son of Isaac (SOFI) and Near-Infrared Camera (NIRC) exhibit less than 0.5% nonlinearity
The amount of gray dust needed to supplant the cosmological constant as the cause of the dimming 0.14 mag ofof rhiaghco-zmSpNoesiItiaownoouflgdrraepshuiltteinorangrEaBp~hIit\e/s0il.1ic7atoer, respectively (Aguirre 1999a, 1999b)
Summary
Recent observations of high-redshift (z [ 0.3) Type Ia supernovae (SNe Ia) provide the backbone of the body of evidence that we live in an accelerating universe whose content is dominated by vacuum energy (Riess et al 1998 ; Perlmutter et al 1999). A physical model of dust composed of larger grains ([0.1 km) has been posited by Aguirre (1999a, 1999b) to provide a noncosmological source of extinction with less reddening. Filippenko et al, in preparation ; but see Riess et al 1999a ; Drell, Loredo, & Wassermann 2000) It is not known what kind or degree of change in the observable properties of SNe Ia would indicate a change in the expected peak luminosity by 30%. A physical model of gray intergalactic dust, such as that proposed by Aguirre (1999a, 1999b), still induces some reddening of SN light, which can be detected in the wavelength range between optical and near-IR light. In ° 2 we describe our observations, in ° 3 we give an analysis, and in ° 4 we interpret them
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