THE CARNEGIE SUPERNOVA PROJECT: ANALYSIS OF THE FIRST SAMPLE OF LOW-REDSHIFT TYPE-Ia SUPERNOVAE

By G. Folatelli, M. Phillips, C. Burns, C. Contreras, M. Hamuy, W. Freedman, S. E. Persson, M. Stritzinger, N. Suntzeff, K. Krisciunas and 12 more. 2009

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An analysis of the first set of low-redshift (z < 0.08) Type Ia supernovae (SNe Ia) 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; YJHKs) 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 SN Ia data in the ugriBVYJH bands. The intrinsic colors at maximum light are calibrated using a subsample of supernovae (SNe) 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, RV ≈ 1.7, is derived when using the entire sample of SNe. However, when the two highly reddened SNe (SN 2005A and SN 2006X) in the sample are excluded, a value RV ≈ 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 SNe are studied in all bands using a two-parameter linear fit to the decline rates and the colors at maximum light, or alternatively, the color excesses. In both cases, similar results are obtained with dispersions in absolute magnitudes of 0.12–0.16 mag, depending on the specific filter–color combination. In contrast to the results obtained from the comparison of the color excesses, these fits of absolute magnitude give RV≈ 1–2 when the dispersion is minimized, even when the two highly reddened SNe are excluded. This discrepancy suggests that, beyond the “normal” interstellar reddening produced in the host galaxies, there is an intrinsic dispersion in the colors of SNe Ia which is correlated with luminosity but independent of the decline rate. Finally, a Hubble diagram for the best-observed subsample of SNe is produced by combining the results of the fits of absolute magnitude versus decline rate and color excess for each filter. The resulting scatter of 0.12 mag appears to be limited by the peculiar velocities of the host galaxies as evidenced by the strong correlation between the distance-modulus residuals observed in the individual filters. The implication is that the actual precision of SNe Ia distances is 3%–4%.

Subfields: Astronomy and Astrophysics, Instrumentation, Nuclear and High Energy Physics

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Citations in the corpus

Cosmological parameters from the comparison of peculiar velocities with predictions from the 2M++ density field (2014, background): “A1 is composed of SNe within 200 h−1Mpc and draws 34 SNe from Jha et al. (2007), 185 from Hicken et al. (2009) and 26 from Folatelli et al. (2010).”
COSMOLOGICAL CONSTRAINTS FROM MEASUREMENTS OF TYPE Ia SUPERNOVAE DISCOVERED DURING THE FIRST 1.5 yr OF THE Pan-STARRS1 SURVEY (2013, background): “SN Ia are more nearly standard candles when observed in restframe near-infrared bands and extinction is significantly lower at these wavelengths (Krisciunas et al. 2004; WoodVasey et al. 2008; Mandel et al. 2009; Folatelli et al. 2010; Barone-Nugent et al. 2012; Kattner et al. 2012).”
Spectrophotometric time series of SN 2011fe from the Nearby Supernova Factory (2013, methodology): “Folatelli et al. (2010) reapplied the procedure used by Lira (1996) and Phillips et al. (1999) and derived an intrinsic color law for the “tail” of SN Ia light curves, and for maximum light using pseudocolors (the difference between the magnitudes of two bands at each band’s date of maximum).”
ON THE SOURCE OF THE DUST EXTINCTION IN TYPE Ia SUPERNOVAE AND THE DISCOVERY OF ANOMALOUSLY STRONG Na i ABSORPTION (2013, background): “…for individual SNe Ia indicate that while most heavily-reddened events have RV < 2, the color excesses of many SNe Ia with E(B − V ) < 0.3 are consistent with the standard Galactic value of RV ∼ 3 (Folatelli et al. 2010; Mandel et al. 2011; Phillips 2012; C. Burns et al. 2013, in preparation).”
The dependence of Type Ia Supernovae luminosities on their host galaxies (2010, methodology): “We note that Folatelli et al. (2010) actually find an decrease in RV (RV = RB−1) in a sample of low-redshift SNe Ia when including very red SNe Ia, though these events with (B − V ) ∼ 1 are much redder than any SNLS SN considered in this paper.”
Measuring the Hubble constant with Type Ia supernovae as near-infrared standard candles (2017, methodology): “Fitting template NIR light-curves (e.g. Wood-Vasey et al. 2008; Folatelli et al. 2010; Burns et al. 2011; Kattner et al. 4 Because Riess et al. (2016) used flow corrections for the Hubble flow sample, perhaps the best comparison is our flow-corrected redshifts value (Table 4), which coincidentally…”
THE CARNEGIE SUPERNOVA PROJECT: LIGHT-CURVE FITTING WITH SNooPy (2010, background): “The details of the observations, data reduction, and photometric systems are described in detail in Hamuy et al. (2006), Contreras et al. (2010), and Folatelli et al. (2010).”
Carnegie Supernova Project: Observations of Type IIn supernovae ⋆ (2013, background): “We note that SN 2008fq was corrected for a substantial amount of extinction(AV = 1.6 mag), which is derived from NaI D absorption that is known to provide poor constraints on reddening (Blondin et al. 2009; Folatelli et al. 2010; Poznanski et al. 2011).”
The Electromagnetic Counterpart of the Binary Neutron Star Merger LIGO/Virgo GW170817. II. UV, Optical, and Near-infrared Light Curves and Comparison to Kilonova Models (2017, background): “These colors are significantly redder than those of known supernovae near explosion (e.g., Folatelli et al. 2010; Bianco et al. 2014; Galbany et al. 2016).”
TYPE Ia SUPERNOVA LIGHT CURVE INFERENCE: HIERARCHICAL MODELS IN THE OPTICAL AND NEAR-INFRARED (2010, methodology): “Folatelli et al. (2010) compared the apparent colors of the SN to a subset suspected of having no contamination by dust, and found a dust law slope RV ≈ 1.7 best fit the SN sample, assuming a global value of RV .”
CHARACTERIZING THE V-BAND LIGHT-CURVES OF HYDROGEN-RICH TYPE II SUPERNOVAE (2014, methodology): “…of Contreras et al. (2010) as applied to the CSP SN Ia sample, where further discussion can be found on the extent of possible systematic errors incurred from the procedure (which were found to be less than 0.01 mag, and are not included in the photometric errors, also see Folatelli et al. 2010).”