Showing papers by "I. M. Hook published in 2008"

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

Abstract: The Canada-France-Hawaii Telescope Supernova Legacy Survey (CFHT 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 (SFRs). 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 2 of expectations from the two-component SN Ia rate model.

Light curves of five type Ia supernovae at intermediate redshift

Abstract: Aims. We present multi-band light curves and distances for five type Ia supernovae at intermediate redshifts, 0.18 < z < 0.27. Methods. Three telescopes on the Canary Island of La Palma, INT, NOT, and JKT, were used for discovery and follow-up of type Ia supernovae in the g' and r' filters. Supernova fluxes were measured by simultaneously fitting a supernova and host galaxy model to the data, and then calibrated using star catalogues from the Sloan Digital Sky Survey. Results. The light curve shape and colour corrected peak luminosities are consistent with the expectations of a flat ΛCDM universe at the 1.5σ level. One supernova in the sample, SN1999dr, shows surprisingly large reddening, considering both that it is located at a significant distance from the core of its host (~4 times the fitted exponential radius) and that the galaxy can be spectroscopically classified as early-type with no signs of ongoing star formation.

Looking Beyond Lambda with the Union Supernova Compilation

Abstract: The recent robust and homogeneous analysis of the world's supernova distance-redshift data, together with cosmic microwave background and baryon acoustic oscillation data, provides a powerful tool for constraining cosmological models. Here we examine particular classes of scalar field, modified gravity, and phenomenological models to assess whether they are consistent with observations even when their behavior deviates from the cosmological constant Lambda. Some models have tension with the data, while others survive only by approaching the cosmological constant, and a couple are statistically favored over LCDM. Dark energy described by two equation of state parameters has considerable phase space to avoid Lambda and next generation data will be required to constrain such physics.

CLUSTERING OF SUPERNOVA Ia HOST GALAXIES

Abstract: For the first time the cross-correlation between Type Ia supernova host galaxies and surrounding field galaxies is measured using the Supernova Legacy Survey sample. Over the z = 0.2–0.9 redshift range we find that supernova hosts are correlated an average of 60% more strongly than similarly selected field galaxies over the 3''-100'' range and about a factor of 3 more strongly below 10''. The correlation errors are empirically established with a jackknife analysis of the four SNLS fields. The hosts are more correlated than the field at a significance of 99% in the fitted amplitude and slope, with the point-by-point difference of the two correlation functions having a reduced χ2 for 8 degrees of freedom of 4.3, which has a probability of random occurrence of less than 3 × 10−5. The correlation angle is 1.5'' ± 0.5'', which deprojects to a fixed comoving correlation length of approximately 6.5 ± 2 h−1 Mpc . Weighting the field galaxies with the mass and star formation rate supernova frequencies of the simple A + B model produces good agreement with the observed clustering. We conclude that these supernova clustering differences are primarily the expected outcome of the dependence of supernova rates on galaxy masses and stellar populations with their clustering environment.

Type Ia Supernovae Rates and Galaxy Clustering from the CFHT Supernova Legacy Survey

Abstract: 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.