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Register a new userSNe Ia host galaxy properties from Sloan Digital Sky Survey-II spectroscopy
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We study the stellar populations of SNe Ia host galaxies using SDSS-II spectroscopy. We focus on the relationships of SNe Ia properties with stellar velocity dispersion and the stellar population parameters age, metallicity and element abundance ratios derived by fitting absorption line indices to stellar population models. We concentrate on a sub-sample of 84 SNe Ia from the SDSS-II Supernova Survey. In agreement with previous findings, we find that SALT2 stretch factor values show the strongest dependence on stellar population age. Hence, SNe Ia peak-luminosity is closely related to the age of the stellar progenitor systems, where more luminous SNe Ia appear in younger stellar populations. We find no statistically significant trends in the Hubble residual with any of the stellar population parameters studied, including age and metallicity contrary to the literature, as well as with stellar velocity dispersion. Moreover, we find that the method of stellar mass derivation is affecting the Hubble residual-mass relationship when lower number statistics are used. We extend the sample to also include SNe Ia with available SDSS host galaxy photometry only. For this larger sample (247 objects) the reported Hubble residual-mass relation is strongly dependent on the stellar mass range studied and behaves as a step function. In the high mass regime, probed by our host spectroscopy sample, the relation between Hubble residual and stellar mass is flat. Below a stellar mass of ~2x10^10 Msun, i.e. close to the evolutionary transition mass of low-redshift galaxies reported in the literature, the trend changes dramatically such that lower mass galaxies possess lower luminosity SNe Ia after light-curve corrections. This non-linear behaviour of the Hubble residual-mass relationship should be accounted for when using stellar mass as a further parameter for minimising the Hubble residuals.
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The sample of 137 low-redshift type Ia supernovae with 0.05 < z < 0.3 obtained from the SDSS-II Supernova Survey for the southern equatorial stripe of 300 square degrees is used to derive the luminosity functions of type Ia supernovae and of their host galaxies in the gri passbands. We show that the luminosity function of type Ia supernova host galaxies matches well with that of galaxies in the general field, suggesting that the occurrence of type Ia supernovae does not favour a particular type of galaxies but is predominantly proportional to the luminosity of galaxies. The only evidence that points to possible correlation between the supernova rate and star formation activity is that the supernova rate in late-type galaxies is higher than that in early-type galaxies by 31+/-35%. The sample contains 8 type Ia supernovae whose host galaxies were not identified, but it is shown that their occurrence is consistent with them occurred in low luminous galaxies beyond the survey. The luminosity function of type Ia supernovae is approximately Gaussian with the full-width half maximum being a factor of 1.4 in luminosity. The Gaussian distribution becomes tighter if the ratio of extinction to reddening, R_V, is lower than the characteristic value for the Milky Way and if luminosity is corrected for the light curve shape. The colour excess is ~0.07 mag which is significantly smaller than reddening expected for field galaxies. This colour excess does not vary with the distance of the supernovae from the centre of the host galaxy to 15 kpc. This suggests that the major part of the colour excess appears to be either intrinsic or reddening that arises in the immediate environment of supernova, rather than interstellar reddening in host galaxies.
This paper describes the data release of the Sloan Digital Sky Survey-II (SDSS-II) Supernova Survey conducted between 2005 and 2007. Light curves, spectra, classifications, and ancillary data are presented for 10,258 variable and transient sources discovered through repeat ugriz imaging of SDSS Stripe 82, a 300 deg2 area along the celestial equator. This data release is comprised of all transient sources brighter than r~22.5 mag with no history of variability prior to 2004. Dedicated spectroscopic observations were performed on a subset of 889 transients, as well as spectra for thousands of transient host galaxies using the SDSS-III BOSS spectrographs. Photometric classifications are provided for the candidates with good multi-color light curves that were not observed spectroscopically. From these observations, 4607 transients are either spectroscopically confirmed, or likely to be, supernovae, making this the largest sample of supernova candidates ever compiled. We present a new method for SN host-galaxy identification and derive host-galaxy properties including stellar masses, star-formation rates, and the average stellar population ages from our SDSS multi-band photometry. We derive SALT2 distance moduli for a total of 1443 SN Ia with spectroscopic redshifts as well as photometric redshifts for a further 677 purely-photometric SN Ia candidates. Using the spectroscopically confirmed subset of the three-year SDSS-II SN Ia sample and assuming a flat Lambda-CDM cosmology, we determine Omega_M = 0.315 +/- 0.093 (statistical error only) and detect a non-zero cosmological constant at 5.7 sigmas.
Previous studies have shown the filamentary structures in the cosmic web influence the alignments of nearby galaxies. We study this effect in the LOWZ sample of the Sloan Digital Sky Survey using the Cosmic Web Reconstruction filament catalogue. We find that LOWZ galaxies exhibit a small but statistically significant alignment in the direction parallel to the orientation of nearby filaments. This effect is detectable even in the absence of nearby galaxy clusters, which suggests it is an effect from the matter distribution in the filament. A nonparametric regression model suggests that the alignment effect with filaments extends over separations of 30-40 Mpc. We find that galaxies that are bright and early-forming align more strongly with the directions of nearby filaments than those that are faint and late-forming; however, trends with stellar mass are less statistically significant, within the narrow range of stellar mass of this sample.
Supernova rates are directly coupled to high mass stellar birth and evolution. As such, they are one of the few direct measures of the history of cosmic stellar evolution. In this paper we describe an probabilistic technique for identifying supernovae within spectroscopic samples of galaxies. We present a study of 52 type Ia supernovae ranging in age from -14 days to +40 days extracted from a parent sample of simeq 50,000 spectra from the SDSS DR5. We find a Supernova Rate (SNR) of 0.472^{+0.048}_{-0.039}(Systematic)^{+0.081}_{-0.071}(Statistical)SNu at a redshift of <z> = 0.1. This value is higher than other values at low redshift at the 1{sigma}, but is consistent at the 3{sigma} level. The 52 supernova candidates used in this study comprise the third largest sample of supernovae used in a type Ia rate determination to date. In this paper we demonstrate the potential for the described approach for detecting supernovae in future spectroscopic surveys.
The Baryon Acoustic Oscillation (BAO) feature in the power spectrum of galaxies provides a standard ruler to probe the accelerated expansion of the Universe. The current surveys covering a comoving volume sufficient to unveil the BAO scale are limited to redshift $z lesssim 0.7$. In this paper, we study several galaxy selection schemes aiming at building an emission-line-galaxy (ELG) sample in the redshift range $0.6<z<1.7$, that would be suitable for future BAO studies using the Baryonic Oscillation Spectroscopic Survey (BOSS) spectrograph on the Sloan Digital Sky Survey (SDSS) telescope. We explore two different colour selections using both the SDSS and the Canada France Hawai Telescope Legacy Survey (CFHT-LS) photometry in the u, g, r, and i bands and evaluate their performance selecting luminous ELG. From about 2,000 ELG, we identified a selection scheme that has a 75 percent redshift measurement efficiency. This result confirms the feasibility of massive ELG surveys using the BOSS spectrograph on the SDSS telescope for a BAO detection at redshift $zsim1$, in particular the proposed eBOSS experiment, which plans to use the SDSS telescope to combine the use of the BAO ruler with redshift space distortions using emission line galaxies and quasars in the redshift $0.6<z<2.2$.
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