THE CARNEGIE SUPERNOVA PROJECT: ANALYSIS OF THE FIRST SAMPLE OF LOW-REDSHIFT TYPE-Ia SUPERNOVAE (original) (raw)
Related papers
The Carnegie Supernova Project: first photometry data release of low-redshift type Ia supernovae
The Astronomical …, 2011
The Carnegie Supernova Project is a five-year survey being carried out at the Las Campanas Observatory to obtain high-quality light curves of ∼100 low-redshift Type Ia supernovae in a well-defined photometric system. Here we present the first release of photometric data that contains the optical light curves of 35 Type Ia supernovae, and near-infrared light curves for a subset of 25 events. The data comprise 5559 optical (ugriBV ) and 1043 near-infrared (Y JHK s ) data points in the natural system of the Swope telescope. Twenty-eight supernovae have pre-maximum data, and for 15 of these, the observations begin at least 5 days before B maximum. This is one of the most accurate datasets of low-redshift Type Ia supernovae published to date. When completed, the CSP dataset will constitute a fundamental reference for precise determinations of cosmological parameters, and serve as a rich resource for comparison with models of Type Ia supernovae. Subject headings: galaxies: distances and redshifts -supernovae: general 1 This paper includes data gathered with the 6.5-m Magellan Telescopes located at Las Campanas Observatory, Chile. under cooperative agreement with the National Science Foundation. J CSP − J 2MASS = 0.010 ± 0.003 mag, H CSP − H 2MASS = 0.043 ± 0.003 mag. To determine if there are any significant color terms, we looked for possible correlations of J CSP − J 2MASS and H CSP − H 2MASS vs. (J − H) CSP . Over the range of color covered by the stars [0.2 < (J − H) CSP < 0.7 mag], we obtained the following fits: J CSP − J 2MASS = (−0.045 ± 0.008) × (J − H) CSP + (0.035 ± 0.067) H CSP − H 2MASS = (0.005 ± 0.006) × (J − H) CSP + (0.038 ± 0.080).
The Astrophysical Journal, 2000
From an analysis of SNe 1972E, 1980N, 1981B, 1981D, 1983R, 1998bu, 1999cl, and 1999cp we find that the intrinsic V−K colors of Type Ia SNe of typical luminosity (i.e. with multi-color light curve shape (MLCS) parameter −0.4 ∼ < ∆ ∼ < +0.2 mag) suggest a uniform color curve. V−K colors become bluer linearly with time from roughly one week before B-band maximum until one week after maximum, after which they redden linearly until four weeks after maximum. V−H colors exhibit very similar color evolution. V−J colors exhibit slightly more complex evolution, with greater scatter. The existence of V minus near infrared color relations allows the construction of near infrared light curve templates that are an improvement on those of .
A New Method to Calibrate the Magnitudes of Type Ia Supernovae at Maximum Light
Astrophysical Journal, 2006
We present a new empirical method for fitting multicolor light curves of Type Ia supernovae. Our method combines elements from two widely used techniques in the literature: the delta_m15 template fitting method and the Multicolor Light-Curve Shape method. An advantage of our technique is the ease of adding new colors, templates, or parameters to the fitting procedure. We use a large sample of published light curves to calibrate the relations between the absolute magnitudes at maximum and delta_m15 in BVRI filters. We find that individual subsamples from a given survey or publication have significantly tighter relationships between light curve shape and luminosity than the relationship derived from the sum of all the samples, pointing to uncorrected systematic errors in the photometry, mainly in BV filters. Using our method, we calculate luminosity distances and host galaxy reddening to 89 SNe in the Hubble flow and construct a low-z Hubble diagram. The dispersion of the SNe in the Hubble diagram is 0.20 mag, or an error of ~9% in distance to a single SN. Our technique produces similar or smaller dispersion in the low-z Hubble diagram than other techniques in the literature.
Astronomy and Astrophysics, 2001
We present a distance to NGC 4527, the host galaxy of the type Ia SN 1991T, measured by surface brightness fluctuations. This supernova has been labelled "peculiar" both on the grounds of its spectroscopic behaviour and its apparent overluminosity with respect to other supernovae. The distance modulus to NGC 4527 and thus to SN 1991T is 30.26 ± 0.09. This relatively short distance largely removes the discrepancy with other Ia supernovae having similar light-curve characteristics and also removes the motivation for interpreting SN 1991T as a super-Chandrasekhar explosion. However, the reddening uncertainty results in significant uncertainty of the absolute magnitudes.
The Astronomical Journal, 2004
We present optical and/or infrared photometry of the Type Ia supernovae SN 1991T, SN 1991bg, SN 1999ek, SN 2001bt, SN 2001cn, SN 2001cz, and SN 2002bo. All but one of these supernovae have decline rate parameters ∆m 15 (B) close to the median value of 1.1 for the whole class of Type Ia supernovae. The addition of these supernovae to the relationship between the near-infrared absolute magnitudes and ∆m 15 (B) strengthens the previous relationships we have found, in that the maximum light absolute magnitudes are essentially independent of the decline rate parameter. (SN 1991bg, the prototype of the subclass of fast declining Type Ia supernovae, is a special case.) The dispersion in the Hubble diagram in JHK is only ∼0.15 mag. The near-infrared properties of Type Ia supernovae continue to be excellent measures of the luminosity distances to the supernova host galaxies, due to the need for only small corrections from the epoch of observation to maximum light, low dispersion in absolute magnitudes at maximum light, and the minimal reddening effects in the near-infrared.
Publications of the Astronomical Society of the Pacific, 2012
We analyze the standardizability of Type Ia supernovae (SNe Ia) in the near-infrared (NIR) by investigating the correlation between observed peak NIR (Y JH) absolute magnitude and post-maximum B-band decline-rate [∆m 15 (B)]. A sample of 27 low-redshift SNe Ia with well-observed NIR light-curves observed by the Carnegie Supernova Project (CSP) between 2004 and 2007 is used. All 27 objects have pre-maximum coverage in optical bands, with a subset of 13 having pre-maximum NIR observations as well; coverage of the other 14 begins shortly after NIR maximum brightness. We describe the methods used to derive light-curve parameters (absolute peak magnitudes and decline-rates) from both spline and template fitting procedures, and confirm prior findings that fitting templates to SNe Ia light-curves in the NIR is problematic due to the diversity of post-maximum behavior of objects that are characterized by similar ∆m 15 (B) values, especially at high decline-rates. Nevertheless, we show that NIR lightcurves can be reasonably fit with a template, especially if the observations begin within 5 days after NIR maximum. SNe Ia appear to be better "standardizable candles" in the NIR bands than in the optical bands. For the subset of 13 objects in our data set that excludes the highly reddened and fast-declining SNe Ia, and includes only those objects for which NIR observations began prior to 5 days after maximum light, we find modest (1.7σ) evidence for a peak luminosity vs. decline-rate relation in Y , and stronger evidence (2.8σ) in J and H. Using R V values differing from the canonical value (R V = 3.1) is shown to have little effect on the results. A Hubble diagram is presented for the NIR bands and the Bband. The resulting scatter for the combined NIR bands is 0.13 mag, while the B-band produces a scatter of 0.22 mag. Finally, we find evidence for a bimodal distribution in the NIR absolute magnitudes of fast-declining SNe Ia [∆m 15 (B) > 1.7]. These data suggest that applying a correction to SNe Ia peak luminosities for decline-rate is likely to be beneficial in the J-and H-bands to make SNe Ia more precise distance indicators, but of only marginal importance in the Y-band.
Light curves of five type Ia supernovae at intermediate redshift
2008
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.
D ec 2 00 4 Optical and Infrared Photometry of the Type Ia Supernovae 1991 T , 1991 bg
2008
We present optical and/or infrared photometry of the Type Ia supernovae SN 1991T, SN 1991bg, SN 1999ek, SN 2001bt, SN 2001cn, SN 2001cz, and SN 2002bo. All but one of these supernovae have decline rate parameters ∆m15(B) close to the median value of 1.1 for the whole class of Type Ia supernovae. The addition of these supernovae to the relationship between the near-infrared absolute magnitudes and ∆m15(B) strengthens the previous relationships we have found, in that the maximum light absolute magnitudes are essentially independent of the decline rate parameter. (SN 1991bg, the prototype of the subclass of fast declining Type Ia supernovae, is a special case.) The dispersion in the Hubble diagram in JHK is only ∼0.15 mag. The near-infrared properties of Type Ia supernovae continue to be excellent measures of the luminosity distances to the supernova host galaxies, due to the need for only small corrections from the epoch of observation to maximum light, low dispersion in absolute magn...
The ESO/VLT 3rd year Type Ia supernova data set from the supernova legacy survey
Astronomy and Astrophysics, 2009
Aims. We present 139 spectra of 124 Type Ia supernovae (SNe Ia) that were observed at the ESO/VLT during the first three years of the Canada-France-Hawaï Telescope (CFHT) Supernova Legacy Survey (SNLS). This homogeneous data set is used to test for redshift evolution of SN Ia spectra, and will be used in the SNLS 3rd year cosmological analyses. Methods. Spectra have been reduced and extracted with a dedicated pipeline that uses photometric information from deep CFHT Legacy Survey (CFHT-LS) reference images to trace, at sub-pixel accuracy, the position of the supernova on the spectrogram as a function of wavelength. It also separates the supernova and its host light in ∼60% of cases. The identification of the supernova candidates is performed using a spectrophotometric SN Ia model. Results. A total of 124 SNe Ia, roughly 50% of the overall SNLS spectroscopic sample, have been identified using the ESO/VLT during the first three years of the survey. Their redshifts range from z = 0.149 to z = 1.031. The average redshift of the sample is z = 0.63 ± 0.02. This constitutes the largest SN Ia spectral set to date in this redshift range. The spectra are presented along with their best-fit spectral SN Ia model and a host model where relevant. In the latter case, a host subtracted spectrum is also presented. We produce average spectra for pre-maximum, maximum and post-maximum epochs for both z < 0.5 and z ≥ 0.5 SNe Ia. We find that z < 0.5 spectra have deeper intermediate mass element absorptions than z ≥ 0.5 spectra. The differences with redshift are consistent with the selection of brighter and bluer supernovae at higher redshift.
The Carnegie Supernova Project I
Astronomy & Astrophysics, 2018
We aim to improve upon contemporary methods to estimate host-galaxy reddening of stripped-envelope (SE) supernovae (SNe). To this end the Carnegie Supernova Project (CSP-I) SE SN photometry data release, consisting of nearly three dozen objects, is used to identify a minimally reddened sub-sample for each traditionally defined spectroscopic sub-type (i.e., SNe IIb, SNe Ib, SNe Ic). Inspection of the optical and near-infrared (NIR) colors and color evolution of the minimally reddened sub-samples reveals a high degree of homogeneity, particularly between 0 d to +20 d relative to B-band maximum. This motivated the construction of intrinsic color-curve templates, which when compared to the colors of reddened SE SNe, yields an entire suite of optical and NIR color excess measurements. Comparison of optical/optical vs. optical/NIR color excess measurements indicates the majority of the CSP-I SE SNe suffer relatively low amounts of reddening (i.e., E(B−V)host< 0.20 mag) and we find evid...