SUBLUMINOUS TYPE Ia SUPERNOVAE AT HIGH REDSHIFT FROM THE SUPERNOVA LEGACY SURVEY (original) (raw)
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2010
We present a measurement of the volumetric Type Ia supernova (SN Ia) rate based on data from the Sloan Digital Sky Survey II (SDSS-II) Supernova Survey. The adopted sample of supernovae (SNe) includes 516 SNe Ia at redshift z 0.3, of which 270(52%) are spectroscopically identified as SNe Ia. The remaining 246 SNe Ia were identified through their light curves; 113 of these objects have spectroscopic redshifts from spectra of their host galaxy, and 133 have photometric redshifts estimated from the SN light curves. Based on consideration of 87 spectroscopically confirmed non-Ia SNe discovered by the SDSS-II SN Survey, we estimate that 2.04 +1.61 −0.95 % of the photometric SNe Ia may be misidentified. The sample of SNe Ia used in this measurement represents an order of magnitude increase in the statistics for SN Ia rate measurements in the redshift range covered by the SDSS-II Supernova Survey. If we assume an SN Ia rate that is constant at low redshift (z < 0.15), then the SN observations can be used to infer a value of the SN rate of r V = (2.69 +0.34+0.21 −0.30−0.01)×10 −5 SNe yr −1 Mpc −3 (H 0 /(70 km s −1 Mpc −1)) 3 at a mean redshift of ∼0.12, based on 79 SNe Ia of which 72 are spectroscopically confirmed. However, the large sample of SNe Ia included in this study allows us to place constraints on the redshift dependence of the SN Ia rate based on the SDSS-II Supernova Survey data alone. Fitting a power-law model of the SN rate evolution, r V (z) = A p × ((1 + z)/(1 + z 0)) ν , over the redshift range 0.0 < z < 0.3 with z 0 = 0.21, results in A p = (3.43 +0.15 −0.15) × 10 −5 SNe yr −1 Mpc −3 (H 0 /(70 km s −1 Mpc −1)) 3 and ν = 2.04 +0.90 −0.89 .
The Astrophysical …, 2010
We present a measurement of the volumetric Type Ia supernova (SN Ia) rate based on data from the Sloan Digital Sky Survey II (SDSS-II) Supernova Survey. The adopted sample of supernovae (SNe) includes 516 SNe Ia at redshift z 0.3, of which 270 (52%) are spectroscopically identified as SNe Ia. The remaining 246 SNe Ia were identified through their light curves; 113 of these objects have spectroscopic redshifts from spectra of their host galaxy, and 133 have photometric redshifts estimated from the SN light curves. Based on consideration of 87 spectroscopically confirmed non-Ia SNe discovered by the SDSS-II SN Survey, we estimate that 2.04 +1.61 −0.95 % of the photometric SNe Ia may be misidentified. The sample of SNe Ia used in this measurement represents an order of magnitude increase in the statistics for SN Ia rate measurements in the redshift range covered by the SDSS-II Supernova Survey. If we assume a SN Ia rate that is constant at low redshift (z < 0.15), then the SN observations can be used to infer a value of the SN rate of r V = (2.69 +0.34+0.21 −0.30−0.01 ) ×10 −5 SNe yr −1 Mpc −3 (H 0 /(70 km s −1 Mpc −1 )) 3 at a mean redshift of ∼ 0.12, based on 79 SNe Ia of which 72 are spectroscopically confirmed. However, the large sample of SNe Ia included in this study allows us to place constraints on the redshift dependence of the SN Ia rate based on the SDSS-II Supernova Survey data alone. Fitting a power-law model of the SN rate evolution, r V (z) = A p × ((1 + z)/(1 + z 0 )) ν , over the redshift range 0.0 < z < 0.3 with z 0 = 0.21, results in A p = (3.43 +0.15 −0.15 ) × 10 −5 SNe yr −1 Mpc −3 (H 0 /(70 km s −1 Mpc −1 )) 3 and ν = 2.04 +0.90 −0.89 .
The Astrophysical …, 2008
We present a measurement of the rate of type Ia supernovae (SNe Ia) from the first of three seasons of data from the SDSS-II Supernova Survey. For this measurement, we include 17 SNe Ia at redshift z ≤ 0.12. Assuming a flat cosmology with Ω m = 0.3 = 1 − Ω Λ , we find a volumetric SN Ia rate of [2.93 +0.17 −0.04 (systematic) +0.90 −0.71 (statistical)]×10 −5 SNe Mpc −3 h 3 70 year −1 , at a volumeweighted mean redshift of 0.09. This result is consistent with previous measurements of the SN Ia rate in a similar redshift range. The systematic errors are well controlled, resulting in the most precise measurement of the SN Ia rate in this redshift range. We use a maximum likelihood method to fit SN rate models to the SDSS-II Supernova Survey data in combination with other rate measurements, thereby constraining models for the redshift-evolution of the SN Ia rate. Fitting the combined data to a simple power-law evolution of the volumetric SN Ia rate, r V ∝ (1 + z) β , we obtain a value of β = 1.5 ± 0.6, i.e. the SN Ia rate is determined to be an increasing function of redshift at the ∼ 2.5σ level. Fitting the results to a model in which the volumetric SN rate, r V = Aρ(t) + Bρ(t), where ρ(t) is the stellar mass density andρ(t) is the star formation rate, we find A = (2.8 ± 1.2) × 10 −14 SNe M −1 ⊙ year −1 , B = (9.3 +3.4 −3.1 ) × 10 −4 SNe M −1 ⊙ .
The Type Ia Supernova Rate at z ≈ 0.5 from the Supernova Legacy Survey
The Astronomical Journal, 2006
We present a measurement of the distant Type Ia supernova rate derived from the first two years of the Canada -France -Hawaii Telescope Supernova Legacy Survey. We observed four one-square degree fields with a typical temporal frequency of ∆t ∼ 4 observer-frame days over time spans of from 158 to 211 days per season for each field, with breaks during full moon. We used 8-10 meter-class -2telescopes for spectroscopic followup to confirm our candidates and determine their redshifts. Our starting sample consists of 73 spectroscopically verified Type Ia supernovae in the redshift range 0.2 < z < 0.6. We derive a volumetric SN Ia rate of r V ( z = 0.47) = 0.42 +0.13 −0.09 (systematic) ±0.06 (statistical) ×10 −4 yr −1 Mpc 3 , assuming h = 0.7, Ω m = 0.3 and a flat cosmology. Using recently published galaxy luminosity functions derived in our redshift range, we derive a SN Ia rate per unit luminosity of r L ( z = 0.47) = 0.154 +0.048 −0.033 (systematic) +0.039 −0.031 (statistical) SNu. Using our rate alone, we place an upper limit on the component of SN Ia production that tracks the cosmic star formation history of 1 SN Ia per 10 3 M ⊙ of stars formed. Our rate and other rates from surveys using spectroscopic sample confirmation display only a modest evolution out to z = 0.55.
EVOLUTION IN THE VOLUMETRIC TYPE Ia SUPERNOVA RATE FROM THE SUPERNOVA LEGACY SURVEY
The Astronomical Journal, 2012
We present a measurement of the volumetric Type Ia supernova (SN Ia) rate (SNR Ia) as a function of redshift for the first four years of data from the Canada-France-Hawaii Telescope (CFHT) Supernova Legacy Survey (SNLS). This analysis includes 286 spectroscopically confirmed and more than 400 additional photometrically identified SNe Ia within the redshift range 0.1 ≤ z ≤ 1.1. The volumetric SNR Ia evolution is consistent with a rise to z ∼ 1.0 that follows a power-law of the form (1+z) α , with α = 2.11 ± 0.28. This evolutionary trend in the SNLS rates is slightly shallower than that of the cosmic star-formation history over the same redshift range. We combine the SNLS rate measurements with those from other surveys that complement the SNLS redshift range, and fit various simple SN Ia delay-time distribution (DTD) models to the combined data. A simple power-law model for the DTD (i.e., ∝ t −β) yields values from β = 0.98 ± 0.05 to β = 1.15 ± 0.08 depending on the parameterization of the cosmic star formation history. A two-component model, where SNR Ia is dependent on stellar mass (M stellar) and star formation rate (SFR) as SNR Ia (z) = A× M stellar (z)+ B × SFR(z), yields the coefficients A = (1.9 ± 0.1) × 10 −14 SNe yr −1 M −1 ⊙ and B = (3.3 ± 0.2) × 10 −4 SNe yr −1 (M ⊙ yr −1) −1. More general two-component models also fit the data well, but single Gaussian or exponential DTDs provide significantly poorer matches. Finally, we split the SNLS sample into two populations by the light curve width (stretch), and show that the general behavior in the rates of faster-declining SNe Ia (0.8 ≤ s < 1.0) is similar, within our measurement errors, to that of the slower objects (1.0 ≤ s < 1.3) out to z ∼ 0.8.
Spectra of High-Redshift Type Ia Supernovae and a Comparison with Their Low-Redshift Counterparts
The Astronomical Journal, 2005
We present spectra for 14 high-redshift (0.17 < z < 0.83) supernovae, which were discovered by the Supernova Cosmology Project as part of a campaign to measure cosmological parameters. The spectra are used to determine the redshift and classify the supernova type, essential information if the supernovae are to be used for cosmological studies. Redshifts were derived either from the spectrum of the host galaxy or from the spectrum of the supernova itself. We present evidence that these supernovae are of Type Ia by matching to spectra of nearby supernovae. We find that the dates of the spectra relative to maximum light determined from this fitting process are consistent with the dates determined from the photometric light curves, and moreover the spectral time-sequence for SNe Type Ia at low and high redshift is indistinguishable. We also show that the expansion velocities measured from blueshifted Ca H&K are consistent with those measured for low-redshift Type Ia supernovae. From these first-level quantitative comparisons we find no evidence for evolution in SNIa properties between these low-and high-redshift samples. Thus even though our samples may not be complete, we conclude that there is a population of SNe Ia at high redshift whose spectral properties match those at low redshift.
Imaging and Demography of the Host Galaxies of High-Redshift Type Ia Supernovae
The Astronomical Journal, 2003
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 (HZT), 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 to 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 (3σ) 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.
The carnegie supernova project: analysis of the first sample of low-redshift type-Ia supernovae
The Astronomical …, 2010
An analysis of the first set of low-redshift (z<0.08) Type Ia supernovae monitored by the Carnegie Supernova Project between 2004 and 2006 is presented. The data consist of well-sampled, high-precision optical (ugriBV ) and near-infrared (NIR; Y JHK s ) light curves in a well-understood photometric system. Methods are described for deriving light-curve parameters, and for building template light curves which are used to fit Type Ia supernova data in the ugriBV Y JH bands. The intrinsic colors at maximum light are calibrated using a subsample of supernovae assumed to have suffered little or no reddening, enabling color excesses to be estimated for the full sample. The optical-NIR color excesses allow the properties of the reddening law in the host galaxies to be studied. A low average value of the total-to-selective absorption coefficient, R V ≈ 1.7, is derived when using the entire sample of supernovae. However, when the two highly reddened supernovae (SN 2005A and SN 2006X) in the sample are excluded, a value R V ≈ 3.2 is obtained, similar to the standard value for the Galaxy. The red colors of these two events are well matched by a model where multiple scattering of photons by circumstellar dust steepens the effective extinction law. The absolute peak magnitudes of the supernovae are studied in all bands using a two-parameter linear fit to the decline 1 This paper includes data gathered with the 6.5 m Magellan Telescopes located at Las Campanas Observatory, Chile.