1. INTRODUCTION

• Supernovae Type Ia (SNeIa)• Good candidate for standard candle to the high-z Universe

(redshift <1.7, at present)• Prime source of chemical enrichment in the Universe

• Optical light curve and spectrum

• Diversity have been studied.

• Lower luminosity SNeIa show faster decline rate m⊿ 15. (e.g. Phillips 1993)• Some EW features are related to m⊿ 15. (e.g. Nugent 1995)• EW dependence on epoch shows dispersion among SNeIa. (e.g. Folatelli 2004)• Vabs dependence on epoch shows dispersion among SNeIa. (e.g. Blondin+ 2006)

Here we explore the correlations in the intermediate redshift range using SDSSSN Survey data and compare our results with the Local (z<0.05) and the high-z (ESSENCE, SNLS and SCP)data. We show interesting trends of all the lines shown above in Section 4-6.

SDSS 超新星サーベイで発見された Ia 型超新星の多様性 Diversity of Supernova Type Ia Discovered by

SDSS Supernova Survey

Kohki Konishi1, Naoki Yasuda1, Mamoru Doi1, Tomoki Morokuma2, Naohiro Takanashi1, Kouichi Tokita1, Yutaka Ihara1 and SDSS Collaboration

1 Univ. of Tokyo, 2 NAOJ

3. TECHNIQUE

• Supernova Extraction • Light contamination of the host galaxy on SNIa generally becomes larger at higer redshift.• SN component should be extracted.

• Overview of our Supernova Extraction Code

2. DATA

• Sloan Digital Sky Survey Supernova Survey (SDSSSN Survey)• This survey observes more than 450 SNeIa at 0.1<z<0.4.

• SDSS 2.5m telescope• Sep-Nov 2005-2007• 300 sq. deg. , every 2 night• 5-band photometry (u,g,r,i,z)• Spectroscopic followup using telescopes around the world

• Our followup spectroscopy • Subaru/FOCAS (71objects)

• wavelength range (R=500)• 4000-9000 Ang (300B+L600 & 300R+Y47) for 2005yr• 3600-9000 Ang (300B+L550 & 300R+Y47) for 2006yr

• The redshift distribution and epoch distribution are shown at the figures below.

7. SUMMARY

• We developed the Supernova Spectrum Extraction Code to eliminate the contamination of its host galaxy accurately.

• We measured equivalent widths and line velocities of absorption lines to explore the diversity of Supernova Type Ia.

• We found new spectral luminosity indicators for independent checks of the decline rate. The equivalent width of “CaII3945” line at the “max” epoch is found to be positively correlated with ⊿m15. The equivalent widths of “SiII4000” lines at the “post-max” epoch also show positive correlations with the decline rate.

• We found that absorption features overall do not change with redshift.

1 “CaII 3945”2 “SiII 4000”3 “MgII 4300”4 “FeII 4800”5 “SII W”6 “SiII 5972”7 “SiII 6355”8 “CaII IR”

(Garavini+ 2007)

early: epoch < -3max: -3 < epoch < 3post-max: 3 < epoch < 10

8. FUTURE WORKS

• How metallicity of host galaxy is related to SNIa spectroscopic properties?• How maximum brightness and color are related to SNIa spectroscopic properties?• How SNIa’s properties affect the determination of cosmological parameters?

6. LINE VELOCITY vs EPOCH

• We show the line velocities of “CaII3945” and “SiII6355” dependence on epoch, with higher-z results (ESSENCE) overlapped.

• Vabs(CaII3945) and Vabs(SiII6355) both decrease gradually with increasing epoch, showing that the kinematical energy becomes smaller with increasing epoch. • These trends are consistent to the results from high-z ESSENCE samples (Blondin+ 2006).

4. EQUIVALENT WIDTH vs m⊿ 15

• We show the equivalent widths of “CaII3945” and “SiII4000” dependence on m⊿ 15, which can be used as new spectral luminosity indicators.

• EW(CaII3945) is found to be increasing monotonously with m⊿ 15 at the “max” epoch for the first time. • EW(SiII4000) is found to be increasing monotonously with m⊿ 15 not only at the “max” but also at the “post-max” epoch for the first time. • The point at the left edge of both figures are from SNIa that shows an unusually broad light curve.

5. EQUIVALENT WIDTHS vs EPOCH

• We show the equivalent widths of “CaII3945” and “FeII4800” dependence on epoch, with higher-z results (SNLS and SCP) overlapped. We discriminate the SNeIa appeared near the center of its host (○) because the contamination of galaxy still may exist in their spectra.

• EW(CaII3945) is found to decrease with increasing epoch.• EW(FeII4800) is found to increase with increasing epoch.

• These trends from the “early” to the “post-max” are consistent to the results from high-z SNLS & SCP samples (Bronder+ 07, Garavini+ 07).

SNhost (b) Separate SN/galaxy flux

by fitting each spatial profile with Gaussians for every wavelength.

SN SN

Wav

elen

gth

2D host

(a) Prepare flux calibrated 2D spectrum.

Wav

elen

gth

SN

host

Blueshift

SN Epoch• the elapsed time from the maximum brightness• epoch = (tobs - tmax)/(1+z)

Spectroscopic property• Absorption features

• Equivalent Width (EW)• Line Velocity (Vabs)from blueshifted wavelength of lines

Photometric property• Decline rate of brightness during 15 days from its peak( m15) [mag]⊿

Absorption features• Photons emitted from the photosphere are absorbed by expanding atmospheric layersof ejected materials (e.g. Ca, Si, Fe)