Determination of the Hubble Constant, the Intrinsic Scatter of Luminosities of Type Ia Supernovae, and Evidence for Nonstandard Dust in Other Galaxies

Abstract

A sample of 109 Type Ia supernovae (SNe Ia) with recession velocity P30,000 km s À1 is compiled from published SN Ia light curves to explore the expansion rate of the local universe. Based on the color parameter ÁC 12 and the decline rate Ám 15 , we found that the average absorption-to-reddening ratios for SN Ia host galaxies are R UBVI ¼ 4:37 AE 0:25, 3:33 AE 0:11, 2:30 AE 0:11, and 1:18 AE 0:11, which are systematically lower than the standard values in the Galaxy. We investigated the correlations of the intrinsic luminosity with light-curve decline rate, color index, and SN environmental parameters. In particular, we found that SNe Ia in E/S0 galaxies close to the central region are brighter than those in the outer region, which may suggest a possible metallicity effect on SN luminosity. The dependence of SN luminosity on galactic environment disappears after corrections for the extinction and ÁC 12 . The Hubble diagrams constructed using 73 Hubble flow SNe Ia yield a 1 scatter of P0.12 mag in BVI bands and $0.16 mag in U band. The luminosity difference between normal SNe Ia and peculiar objects (including SN 1991bg-like and SN 1991T-like events) has now been reduced to within 0.15 mag via ÁC 12 correction. We use the same precepts to correct the nearby SNe Ia with Cepheid distances and found that the fully corrected absolute magnitudes of SNe Ia are M B ¼ À19:33 AE 0:06 and M V ¼ À19:27 AE 0:05. We deduced a value for the Hubble constant of H 0 ¼ 72 AE 6 (total) km s À1 Mpc À1 .

Photometric properties of intermediate-redshift Type Ia supernovae observed by the Sloan Digital Sky Survey-II Supernova Survey

“…These results are consistent with previous studies (e.g. RB ∼ 3.5, Phillips et al 1999;Knop et al 2003;Altavilla et al 2004; RB ∼ 3.3, Wang et al 2006; RV = 1.75 ± 0.27, Nobili and Goobar 2008; RV = 2.2, Kessler et al 2010), which find values of R are smaller than the standard Galactic value.…”

The slowly declining type Ia supernova 2008fv and the near-infrared second maximum

“…Thus, owing to systematic effects, the intrinsic dispersion in the peak brightness remains smaller than ∼0.2 mag depending on the specific filter. As a consequence, the distance measurement uncertainty is at most 10% (Wang et al 2006). Being less affected by interstellar absorption, the nearinfrared observations show that SNe Ia are generally quite homogeneous in this wavelength range at the level of ∼0.15 mag (Meikle 2000;Krisciunas et al 2004a;Wood-Vasey et al 2008;Folatelli et al 2010), leading to distance estimates with an accuracy higher than 7%.We note that the scatter in the Hubble diagram indicated that very precise relative distances can be obtained by means of SNe Ia.…”

“…The inspection of the absolute magnitudes at peak in the optical bands leads to the conclusion that the corrected peak luminosity of SN 2008fv is indistinguishable, within the uncertainties, from that of the mean of the normal SNe Ia (Wang et al 2006). We also note that SN 2008fv is less luminous of ∼0.1 mag than SN 2000E.…”

The envelope mass of red giant donors in type Ia supernova progenitors

“…We checked the types of their host galaxies and found that apart from the host galaxy of SN 2005cl (MCG-01-39-003), which is a S0 galaxy (Wang et al 2009a;Bufano et al 2009), they are both spiral galaxies, i.e. the host galaxy of SN 2001el (NGC 1448) is a Scd galaxy (Wang et al 2003(Wang et al , 2006 and the host galaxy of SN 2001am (NGC 2811) is a Sa galaxy (Bufano et al 2009). The progenitor of SN 2005cl may therefore belong to an old population, but we are unable to infer any information about the population of the other SNe Ia.…”