SNLS : Spectroscopy of Supernovae with the VLT (status) Grégory Sainton LPNHE, CNRS/in2p3 University Paris VI & VII Paris, France On behalf of the SNLS collaboration

Moriond 2004 : Exploring the Universe G. Sainton : SNLS, SN identification with VLT 2 Contents Overview of the VLT observations Spectroscopy analysis First (preliminary) results

Moriond 2004 : Exploring the Universe G. Sainton : SNLS, SN identification with VLT 3 Overview of the VLT observations

Moriond 2004 : Exploring the Universe G. Sainton : SNLS, SN identification with VLT 4 SNLS observations with the VLT 240 hours for 2 years (VLT large programme) on FORS-1 (longslit spectrograph) to identify SNe of the CFHTLS SN programme. Target of opportunity mode : –No precise observation date provided in advance. –Observations are submitted, as soon as a candidate is discovered at CFHT. – Our observations have first priority and are conducted in Service Mode.

Moriond 2004 : Exploring the Universe G. Sainton : SNLS, SN identification with VLT 5 Observing at VLT

Moriond 2004 : Exploring the Universe G. Sainton : SNLS, SN identification with VLT 6 Data processing Data available in Garching about 12 hours after the observations. Preprocessing of the data done with the FORS pipeline, customized for the SNLS use. Extraction of the spectra performed with our own tools, based on a minimum variance estimation (Horne, 1986). It produces the spectrum and its associated error. The host spectrum is extracted when possible.

Moriond 2004 : Exploring the Universe G. Sainton : SNLS, SN identification with VLT 7 Spectroscopy analysis

Moriond 2004 : Exploring the Universe G. Sainton : SNLS, SN identification with VLT 8 Two goals for the spectroscopy : –Identify the SN (Ia, or non Ia). –Measure of the redshift. (host galaxy lines or from the SN if no host galaxy) –The age (with respect to the restframe B band maximum of the LC). –The contamination of the SN spectrum by the host galaxy. –The type of the host. SN Identification Enough to built the Hubble diagram (d L,z) To cross-check the results

Moriond 2004 : Exploring the Universe G. Sainton : SNLS, SN identification with VLT 9 SN Identification (cont.) SNIa = no H + strong Si II

Moriond 2004 : Exploring the Universe G. Sainton : SNLS, SN identification with VLT 10 It’s based on the  2 fitting of our spectrum with a model (local SNe + local galaxy). All the local spectra are into a database. These local spectra are from different type and different age (in the restframe) : 87 spectra from 8 SNIa 56 spectra from 5 peculiar SNIa 9 spectra from 2 SNIc 11 spectra from 1 IIP The database also contains a sample of galaxy spectra in case the host galaxy spectrum is not available. SN Identification (cont.) The quality of the identification is limited by the diversity of the database

Moriond 2004 : Exploring the Universe G. Sainton : SNLS, SN identification with VLT 11 S obs ( obs ) – (  S sn ( rest [1+z])+  S gal ( rest [1+z])) SN Identification (cont.)  obs )    2 Loop over all the selected combinations of galaxie/SNe. Robustified fit (outliers like bad sky lines are discarded). One can fit on a given region only (eg. reject telluric absorptions). Sort the result by ascending  2. Model with a galaxy template

Moriond 2004 : Exploring the Universe G. Sainton : SNLS, SN identification with VLT 12 First (preliminary) results

Moriond 2004 : Exploring the Universe G. Sainton : SNLS, SN identification with VLT 13 A bit of statistics for SNIa is about 3 per bin of ~3 Angstroms. Redshift distribution ~ 3A distribution 27 SNIa =0.55

Moriond 2004 : Exploring the Universe G. Sainton : SNLS, SN identification with VLT 14 Example (Typical SNIa) Best fit with -2 days z = Texp = 2150s ; =5.95 Fit with host galaxy No LC yet to check verify the age fitted.

Moriond 2004 : Exploring the Universe G. Sainton : SNLS, SN identification with VLT 15 Example (Another SNIa) Best fit with sn1994d +2 days To date, the farthest SN of the SNLS programme. Database very poor in SNe with UV coverage. z=0.95 ; No host galaxy T exp = 2150s with Grism 300V (optic) T exp = 2150s with Grism 300I (near IR) 2.66A =4.46 Preliminary

Moriond 2004 : Exploring the Universe G. Sainton : SNLS, SN identification with VLT 16 Example (Peculiar SNIa) z=0.285 ; T exp = 2150s Best fit with -7days sn1999aa is a peculiar SNIa, overluminous. Good agreement with the LC Preliminary 36% of peculiar SNIa expected (Li et al, 2000). One of the farthest SNIa peculiar never observed. SNLS will estimate the SNIa peculiar rate at large redshift. 2.66A =12.6

Moriond 2004 : Exploring the Universe G. Sainton : SNLS, SN identification with VLT 17 Example (non Ia SN) Best fit with +2 days sn1994i is a SNIc. Max of the LC 2 magnitudes weaker than a normal SNIa. Ic identification is difficult, very few SNIc spectra available in the litterature. Only one Ic in the SNLS sample, so far. z=0.167 ; T exp = 2150s 2.66A =11.0 Preliminary

Moriond 2004 : Exploring the Universe G. Sainton : SNLS, SN identification with VLT 18 Conclusion After 6 months, more than 50 candidates spectroed. Already about 30 SNIa found between z~0.17 and z~0.95 with VLT (38 with the other telescopes). Beyond ID and redshift, VLT observations will allow us to do systematic and quantitative comparison of low z and high SNIa (evolution, rate of peculiars Ia...). This software gives quantitative tools to identify spectra. Thank you !

Moriond 2004 : Exploring the Universe G. Sainton : SNLS, SN identification with VLT 19 Back up slides

Moriond 2004 : Exploring the Universe G. Sainton : SNLS, SN identification with VLT 20 Details of this analysis 1.To discriminate between the first best solutions 2. To discriminate between different type of SN

Moriond 2004 : Exploring the Universe G. Sainton : SNLS, SN identification with VLT 21 T exp calculation : How does it work ? The request is to get a minimum signal to noise ratio of 5, for a 10A binning, in the region from the calcium H&K and the magnesium MgII. Ca H&K MgII zT exp (s)

Moriond 2004 : Exploring the Universe G. Sainton : SNLS, SN identification with VLT 22 Constraining the parameters GUI in Tcl/Tk