SNLS Third Year VLT Spectra Release

September 15th, 2009

This is the release of the 139 spectra of 124 Type Ia supernovae obtained in LSS mode with FORS1 and FORS2 at the VLT during the first three years of the CFHT Supernova Legacy Survey (June 1st, 2003 to July 31st, 2006). Most spectra have been obtained using grism 300V with a few exceptions obtained with grism 300I. Eight SNe Ia were observed in MOS mode in this period and are not included in the present sample.

The spectra have been extracted using a dedicated extraction pipeline (PHASE: PHotometric Assisted Spectral Extraction) presented in Baumont et al., A&A 491, 567-585 (2008). The spectra are published in Balland et al., A&A (2009). (see the paper for a detailed description of the analysis).


Title : PHotometry Assisted Spectral Extraction (PHASE) and identiÞcation of SNLS supernovae

Authors : S. Baumont, C. Balland, P. Astier, J. Guy, D. Hardin, D. A. Howell, C. Lidman, M. Mouchet, R. Pain, and N. Regnault

Reference : Baumont et al., A&A 491, 567-585 (2009)

Grab a copy here : Baumont_etal_2008.pdf
Title : The ESO/VLT 3rd year Type Ia supernova data set from the Supernova Legacy Survey

Authors : C. Balland , S. Baumont , S. Basa , M. Mouchet, D. A. Howell, P. Astier, R. G. Carlberg, A. Conley, D. Fouchez, J. Guy, D. Hardin, I. M. Hook, R. Pain, K. Perrett, C. J. Pritchet, N. Regnault, J. Rich, M. Sullivan, P. Antilogus, V. Arsenijevic, J. Le Du, S. Fabbro, C. Lidman, A. Mourao, N. Palanque-Delabrouille, E. Pécontal and V. Ruhlmann-Kleider

Reference : Balland et al., A&A (2009)

Grab a copy here : Balland_etal_2009.pdf


Download the tar files :


The release contains two sets of spectra:

  1. The PHASE extracted spectra. In some cases, a separate extraction of the SN component from its host was not possible and the full (SN+host) spectrum is given.
  2. The spectra of the SN alone. Either a separate extraction was possible, or a host template was subtracted to the full spectrum (see Section 'About host subtraction' below for details). The spectra are rebinned in 15 Å bins.
Each tar file contains a spectrum file for each of the 139 VLT-SNLS Type Ia supernova presented in the paper. Information on individual spectra can be found in Table 1 and 2 of Balland etal (2009).

Spectra files

There is one ASCII file for each spectrum.
- 1st column, Pixel numer
- 2nd column, Wavelength: Lambda in angstroems
- 3rd column, SN Flux: supernova flux in physical units (erg/s/cm2/A/1e-16)
- 4th column, SN Fluxerr: statistical error for the flux measurement
Example (03D1ar: PHASE_03D1ar_270_Balland_etal_09.dat):
@REFERENCE Balland etal (2009)
@SPECTRUM spectrum_03D1ar_270.dat
@SN-NAME 03D1ar
@UNITS 1e-16
@PHASE 5.305
# XPIX :
# WAVE :
# SN_ERR :
0 4150.871 0.00000 0.58504
1 4153.345 0.00000 0.77762
2 4155.819 0.00000 0.56942
3 4158.294 0.00000 1.01251
4 4160.770 0.00000 0.62394
5 4163.246 0.00000 0.79905
6 4165.722 0.00000 0.56884
7 4168.199 0.00000 0.64997
8 4170.676 0.00000 1.27027
9 4173.154 0.00330 0.57286
10 4175.632 -0.10600 0.43863
11 4178.110 0.22680 0.39882
12 4180.589 0.02250 0.34042
13 4183.068 -0.56660 0.34925
14 4185.548 -0.02140 0.26088
15 4188.028 0.20310 0.22628
16 4190.509 -0.14180 0.19956
17 4192.990 0.34030 0.18711
18 4195.471 0.16640 0.15898
19 4197.953 0.08010 0.13442
20 4200.435 -0.24900 0.12054

About host subtraction

All spectra in snonly_spec_Balland09.tar.gz are host subtracted. When possible, host subtraction is performed at the stage of extraction using a photometric host profile measured on deep reference images in three MEGACAM photometric bands (g', r', i' for grism 300V, r', i', z' for grism 300I) - see Baumont et al. (2008) for details. Where a separate extraction is not possible, host subtraction is performed at the stage of identification. A SALT2 model (Guy et al. 2007) including a host component template is fitted to the full (host+SN) spectrum. The best-fit host template is subtracted to get the host-free SN spectrum. Host templates include Kinney et al. (1996) templates and synthetic PEGASE templates (Elliptical to Sd types with ages ranging from 1 to 13 Gyrs). Emission lines are not modeled in the PEGASE templates we use.

About re-calibration

To take into account flux calibration errors and/or slit losses, the SALT2 model includes a 'recalibration' function in the minimization procedure (Guy et al. 2007). The 'recalibration' function is parametrized with the exponential of a polynomial of coefficients γi (i∈ [ 1...n ]): fcal(λ)=exp(-&sum γiΛi).f(λ) with Λ=(λ(Å)/4400-1). Most of the time, only γ1 is used. In a few cases, γ2 is added. The following table gives γ1 and γ2 for each spectrum: recalib.dat.

Please reference to Balland et al. [SNLS Collaboration] A&A (2009) when using this data set.
For more information about this page and the content of the tar file, contact Christophe Balland