SN Ia Host Research Articles

Dust content of core-collapse supernova hosts

We study a small sample of z=0.1-0.6 core-collapse supernova (CCSN) host galaxies. Continuum observations at 250GHz have been performed with MAMBO at the IRAM-30m telescope. None of these sources has been detected and the error-weighted mean flux is 0.25+/-0.32 mJy. Upper limits on their dust masses are derived and the corresponding sample mean corresponds to 1.4 +/- 2.2 x 10^8 Msol. These results are comparable with previous submillimetre observations of SN-Ia hosts performed by Farrah et al. and by Clements et al. We conclude that CCSN hosts are not extreme at millimetre wavelengths, and as confirmed with the optical luminosities of a subset of our sample, they are typical of the local galaxy population.

TYPE Ia SUPERNOVAE RATES AND GALAXY CLUSTERING FROM THE CFHT SUPERNOVA LEGACY SURVEY

The Canada-France-Hawaii Telescope Supernova Legacy Survey (SNLS) has created a large homogeneous database of intermediate redshift (0.2 < z < 1.0) type Ia supernovae (SNe Ia). The SNLS team has shown that correlations exist between SN Ia rates, properties, and host galaxy star formation rates. The SNLS SN Ia database has now been combined with a photometric redshift galaxy catalog and an optical galaxy cluster catalog to investigate the possible influence of galaxy clustering on the SN Ia rate, over and above the expected effect due to the dependence of SFR on clustering through the morphology-density relation. We identify three cluster SNe Ia, plus three additional possible cluster SNe Ia, and find the SN Ia rate per unit mass in clusters at intermediate redshifts is consistent with the rate per unit mass in field early-type galaxies and the SN Ia cluster rate from low redshift cluster targeted surveys. We also find the number of SNe Ia in cluster environments to be within a factor of two of expectations from the two component SNIa rate model.

Improved Distances to Type Ia Supernovae with Multicolor Light‐Curve Shapes: MLCS2k2

We present an updated version of the multicolor light-curve shape method to measure distances to Type Ia supernovae (SNe 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 SNe Ia, including 95 objects in the Hubble flow (cz ≥ 2500 km s-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 SNe Ia, is the largest ever presented with homogeneous distances. We find that the Hubble flow SNe with H0dSN ≥ 7400 km s-1 yield an expansion rate that is 6.5% ± 1.8% lower than the rate determined from SNe within that distance, and this can have a large effect on measurements of the dark energy equation of state with SNe 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 SNe Ia that are significantly reddened by dust in their host galaxies suggest that their mean extinction law may be described by RV 2.7, but optical colors alone provide weak constraints on RV.

Extinction Curves of Lensing Galaxies out toz= 1

We present a survey of the extinction properties of ten lensing galaxies, in the redshift range z = 0.04 - 1.01, using multiply lensed quasars imaged with the ESO VLT in the optical and near infrared. The multiple images act as 'standard light sources' shining through different parts of the lensing galaxy, allowing for extinction studies by comparison of pairs of images. We explore the effects of systematics in the extinction curve analysis, including extinction along both lines of sight and microlensing, using theoretical analysis and simulations. In the sample, we see variation in both the amount and type of extinction. Of the ten systems, seven are consistent with extinction along at least one line of sight. The mean differential extinction for the most extinguished image pair for each lens is A(V) = 0.56 +- 0.04, using Galactic extinction law parametrization. The corresponding mean R_V = 2.8 +- 0.4 is consistent with that of the Milky Way at R_V = 3.1, where R_V = A(V)/E(B-V). We do not see any strong evidence for evolution of extinction properties with redshift. Of the ten systems, B1152+199 shows the strongest extinction signal of A(V) = 2.43 +- 0.09 and is consistent with a Galactic extinction law with R_V = 2.1 +- 0.1. Given the similar redshift distribution of SN Ia hosts and lensing galaxies, a large space based study of multiply imaged quasars would be a useful complement to future dark energy SN Ia surveys, providing independent constraints on the statistical extinction properties of galaxies up to z~1.

Rates and Properties of Type Ia Supernovae as a Function of Mass and Star Formation in Their Host Galaxies

(ABRIDGED) We show that Type Ia supernovae (SNe Ia) are formed within both very young and old stellar populations, with observed rates that depend on the stellar mass and mean star-formation rates (SFRs) of their host galaxies. Models where the SN Ia rate depends solely on host galaxy stellar mass are ruled out with 99% confidence. Our analysis is based on 100 spectroscopically-confirmed SNe Ia, plus 24 photometrically-classified events, all from the Supernova Legacy Survey (SNLS) and distributed over 0.2<z<0.75. Using multi-band photometry, we estimate stellar masses and SFRs for the SN Ia host galaxies by fitting their broad-band spectral energy distributions with the galaxy spectral synthesis code, PEGASE.2. We show that the SN Ia rate per unit mass is proportional to the specific SFR of the parent galaxies -- more vigorously star-forming galaxies host more SNe Ia per unit stellar mass, broadly equivalent to the trend of increasing SN Ia rate in later-type galaxies seen in the local universe. Following earlier suggestions for a simple two-component model approximating the SN Ia rate, we find bivariate linear dependencies of the SN Ia rate on both the stellar masses and the mean SFRs of the host systems. We also demonstrate a dependence of distant SN Ia light-curve shapes on star-formation in the host galaxy, similar to trends observed locally. Passive galaxies, with no star-formation, preferentially host faster-declining/dimmer SNe Ia, while slower-declining/brighter events are only found in systems with ongoing star-formation. We model the light-curve width distribution in star-forming galaxies as the sum of a young component, and an old component taken from the distribution in non-star-forming galaxies.

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

A sample of 109 type Ia supernovae (SNe Ia) with recession velocity < 30,000 km s^{-1}, is compiled from published SNe Ia light curves to explore the expansion rate of the local Universe. Based on the color parameter delta C_{12} and the decline rate delta m_{15}, we found that the average absorption to reddening ratio for SN Ia host galaxies to be R_{UBVI} = 4.37+/-0.25, 3.33+/-0.11, 2.30+/-0.11, 1.18+/-0.11, which are systematically lower than the standard values in the Milky Way. We investigated the correlations of the intrinsic luminosity with light curve decline rate, color index, and supernova environmental parameters. In particular, we found SNe Ia in E/S0 galaxies to be brighter close to the central region 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 delta C_{12}. The Hubble diagrams constructed using 73 Hubble flow SNe Ia yield a 1-sigma scatter of <0.12 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 1991T-like events) has now been reduced to within 0.15 mag via delta C_{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} = -19.33+/-0.06 mag, M_{V} = -19.27+/-0.05 mag. We deduced a value for the Hubble constant of H_{0} = 72 +/- 6 (total) km s^{-1} Mpc^{-1}.

Imaging and Demography of the Host Galaxies of High-Redshift Type Ia Supernovae

We present the results of a study of the host galaxies of high-redshift Type Ia supernovae (SNe Ia). We provide a catalog of 18 hosts of SNe Ia observed with the Hubble Space Telescope (HST) by the High-z Supernova Search Team, including images, scale lengths, measurements of integrated (Hubble-equivalent) BVRIZ photometry in bands where the galaxies are brighter than m ≈ 25 mag, and galactocentric distances of the supernovae. We compare the residuals of SN Ia distance measurements from cosmological fits with measurable properties of the supernova host galaxies that might be expected to correlate with variable properties of the progenitor population, such as host-galaxy color and position of the supernova. We find mostly null results; the current data are generally consistent with no correlations of the distance residuals with host-galaxy properties in the redshift range 0.42 < z < 1.06. Although a subsample of SN hosts shows a formally significant (3 σ) correlation between apparent V-R host color and distance residuals, the correlation is not consistent with the null results from other host colors probed by our largest samples. There is also evidence for the same correlations between SN Ia properties and host type at low redshift and high redshift. These similarities support the current practice of extrapolating properties of the nearby population to high redshifts, pending more robust detections of any correlations between distance residuals from cosmological fits and host properties.