Browsing by Author "Garnavich, PM"
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- ItemHubble Space Telescope observations of nine high-redshift essence supernovae(2005) Krisciunas, K; Garnavich, PM; Challis, P; Prieto, JL; Riess, AG; Barris, B; Aguilera, C; Becker, AC; Blondin, S; Chornock, R; Clocchiatti, A; Covarrubias, R; Filippenko, AV; Foley, RJ; Hicken, M; Jha, S; Kirshner, RP; Leibundgut, B; Li, WD; Matheson, T; Miceli, A; Miknaitis, G; Rest, A; Salvo, ME; Schmidt, BP; Smith, RC; Sollerman, J; Spyromilio, J; Stubbs, CW; Suntzeff, NB; Tonry, JL; Wood-Vasey, WMWe present broadband light curves of nine supernovae ranging in redshift from 0.5 to 0.8. The supernovae were discovered as part of the ESSENCE project, and the light curves are a combination of Cerro Tololo 4 m and Hubble Space Telescope (HST) photometry. On the basis of spectra and/or light-curve fitting, eight of these objects are definitely Type Ia supernovae, while the classification of one is problematic. The ESSENCE project is a 5 yr endeavor to discover about 200 high-redshift Type Ia supernovae, with the goal of tightly constraining the time average of the equation-of-state parameter [w = p/(rho c(2))] of the "dark energy." To help minimize our systematic errors, all of our ground-based photometry is obtained with the same telescope and instrument. In 2003 the highest redshift subset of ESSENCE supernovae was selected for detailed study with HST. Here we present the first photometric results of the survey. We find that all but one of the ESSENCE supernovae have slowly declining light curves and that the sample is not representative of the low-redshift set of ESSENCE Type Ia supernovae. This is unlikely to be a sign of evolution in the population. We attribute the decline-rate distribution of HST events to a selection bias at the high-redshift edge of our sample and find that such a bias will infect other magnitude-limited Type Ia supernova searches unless appropriate precautions are taken.
- ItemOptical spectra of Type Ia supernovae at z=0.46 and z=1.2(2000) Coil, AL; Matheson, T; Filippenko, AV; Leonard, DC; Tonry, J; Riess, AG; Challis, P; Clocchiatti, A; Garnavich, PM; Hogan, CJ; Jha, S; Kirshner, RP; Leibundgut, B; Phillips, MM; Schmidt, BP; Schommer, RA; Smith, RC; Soderberg, AM; Spyromilio, J; Stubbs, C; Suntzeff, NB; Woudt, PWe present optical spectra, obtained with the Keck 10 m telescope, of two high-redshift Type Ia supernovae (SNe Ia) discovered by the High-z Supernova Search Team: SN 1999ff at z = 0.455 and SN 1999fv at z similar to 1.2, the highest redshift published SN Ia spectrum. Both SNe were at maximum light when the spectra were taken. We compare our high-z spectra with low-z normal and peculiar SNe Ia as well as with SNe Ic, Ib, and II. There are no significant differences between SN 1999ff and normal SNe Ia at low redshift. SN 1999fv appears to be an SN Ia and does not resemble the most peculiar nearby SNe Ia.
- ItemTests of the accelerating universe with near-infrared observations of a high-redshift type Ia supernova(2000) Riess, AG; Filippenko, AV; Liu, MC; Challis, P; Clocchiatti, A; Diercks, A; Garnavich, PM; Hogan, CJ; Jha, S; Kirshner, RP; Leibundgut, B; Phillips, MM; Reiss, D; Schmidt, BP; Schommer, RA; Smith, RC; Spyromilio, J; Stubbs, C; Suntzeff, NB; Tonry, J; Woudt, P; Brunner, RJ; Dey, A; Gal, R; Graham, J; Larkin, J; Odewahn, SC; Oppenheimer, BWe have measured the rest-frame B-, V-, and I-band light curves of a high-redshift type Ia supernova (SN 1a), SN 1999Q (z = 0.46), using the Hubble Space Telescope (HST) and ground-based near-infrared detectors. A goal of this study is the measurement of the color excess, EB-I, 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 grayer dust (grain size > 0.1 mu m, rejected at the 2.3-2.6 sigma confidence level) as proposed by Aguirre. The rest-frame I-band light curve shows the secondary maximum 1 month after the B maximum typical of nearby SNe fa of normal luminosity, providing no indication of evolution as a function of redshift out to z approximate to 0.5. An expanded set of similar observations could improve the constraints on any contribution of extragalactic dust to the dimming of high-redshift SNe Ia.
- ItemThe optical afterglow of the gamma-ray burst GRB 012111(2002) Holland, ST; Soszynski, I; Gladders, MD; Barrientos, LF; Berlind, P; Bersier, D; Garnavich, PM; Jha, S; Stanek, KZWe present early-time optical photometry and spectroscopy of the optical afterglow of the gamma-ray burst GRB 011211. The spectrum of the optical afterglow contains several narrow metal lines that are consistent with the burst's occurring at a redshift of 2.14 +/- 0.001. The optical afterglow decays as a power law with a slope of alpha = 0.83 +/- 0.04 for the first approximate to2 days after the burst, at which time there is evidence of a break. The slope after the break is greater than or equal to 1.4. There is evidence of rapid variations in the R-band light approximately 0.5 days after the burst. These variations suggest that there are density fluctuations near the gamma-ray burst on spatial scales of approximately 40-125 AU. The magnitude of the break in the light curve, the spectral slope, and the rate of decay in the optical suggest that the burst expanded into an ambient medium that is homogeneous on large scales. We estimate that the local particle density is between approximately 0.1 and 10 cm(-3) and that the total gamma-ray energy in the burst was (1.2-1.9) x 10(50) ergs. This energy is smaller than, but consistent with, the "standard" value of (5 +/- 2) x 10(50) ergs. Comparing the observed color of the optical afterglow with predictions of the standard beaming model suggests that the rest-frame V-band extinction in the host galaxy is less than or similar to0.03 mag.