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SNLS : Spectroscopy of Supernovae with the VLT (status)

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. Contents. Overview of the VLT observations Spectroscopy analysis First (preliminary) results.

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SNLS : Spectroscopy of Supernovae with the VLT (status)

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  1. 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

  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. SN Identification 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. Enough to built the Hubble diagram (dL,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. SN Identification (cont.) • It’s based on the c2 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. 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. c2=S SN Identification (cont.) 2 Sobs(lobs) – (aSsn(lrest [1+z])+bSgal(lrest [1+z])) s(lobs) Model with a galaxy template • 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 c2. 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 Redshift distribution <S/N>~  3A distribution 27 SNIa <z>=0.55 <S/N> is about 3 per bin of ~3 Angstroms. Moriond 2004 : Exploring the Universe G. Sainton : SNLS, SN identification with VLT

  14. Example (Typical SNIa) Best fit with sn1994d @ -2 days Fit with host galaxy No LC yet to check verify the age fitted. R10D1-04A @ z = 0.687 Texp = 2150s ; <S/N>=5.95 Moriond 2004 : Exploring the Universe G. Sainton : SNLS, SN identification with VLT

  15. Example (Another SNIa) R6D4-9 @ z=0.95 ; No host galaxy Texp= 2150s with Grism 300V (optic) Texp= 2150s with Grism 300I (near IR) Best fit with sn1994d (Ia) @ +2 days <S/N>2.66A=4.46 • To date, the farthest SN of the SNLS programme. • Database very poor in SNe with UV coverage. Preliminary Moriond 2004 : Exploring the Universe G. Sainton : SNLS, SN identification with VLT

  16. Example (Peculiar SNIa) SN2003ha @ z=0.285 ; Texp= 2150s Best fit with sn1999aa @ -7days sn1999aa is a peculiar SNIa, overluminous. Good agreement with the LC <S/N>2.66A=12.6 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. Preliminary Moriond 2004 : Exploring the Universe G. Sainton : SNLS, SN identification with VLT

  17. Example (non Ia SN) sn2003hb @ z=0.167 ; Texp= 2150s Best fit with sn1994i @ +2 days sn1994i is a SNIc. Max of the LC 2 magnitudes weaker than a normal SNIa. <S/N>2.66A=11.0 • Ic identification is difficult, very few SNIc spectra available in the litterature. • Only one Ic in the SNLS sample, so far. 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 • 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. MgII Ca H&K Texp 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. Moriond 2004 : Exploring the Universe G. Sainton : SNLS, SN identification with VLT

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

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