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イメージ Ia型超新星の特徴 距離指標としての問題点

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Light Curve Studies of SDSS Supernovae
with a MultiMulti-band Stretch Method
イメージ
Naohiro TAKANASHI (Univ. of Tokyo)
・D論の簡単な紹介
・距離指標としてのIa型超新星の
上手な使い方を提案する事が目標
・中遠方Ia型超新星の性質を調べた
高梨 直紘(博士課程3年)
Ia型超新星の特徴
・
・
・
・
非常に明るい
明るさが一様
光度進化が小さい
物理学的背景が明確
WD + RG or MS 連星系
チャンドラセカール限界質量にて爆発
距離指標としての問題点
・ 意外と大きな分散(~1mag)
・ 本当に進化はないのか?
・ (K-correction)
・ (減光補正)
理想的な標準光源
宇宙論パラメータの測定に利用されている
諸問題の理解が重要
光度曲線から距離指標としての資質に迫る
I. LC studies of nearby SNe
Data:
122 published nearby (z < 0.1) type Ia SNe
Method:
Multi-band Stretch Method (UBVRI template)
MultiMulti-band Stretch Method
Features:
UBVRI-band light curve fitting
without color correction
have an advantage to study
SN color and host dust extinction
Takanashi et al. (2007)
submitted to MNRAS
1
Colors vs B-band light curve shape
E or S0 galaxies
redder
colors
E only
Galactic
B-V > 0.00
-0.14 < B-V < -0.10
redder
(V - I)max
C-C plot
%
bluer
bluer
bluer
(B – V)max
redder
inverse B-band Stretch Factor
Relation between LC shape and brightness
B-band Magnitude
E or S0 galaxies
-0.14 < B-V < -0.10
narrower
broader
II. LC studies of SDSS SNe
Data:
373 SNe : u, g, r, i, z-band LC from SMP3.10
consist of confirmed, possible (SP, LC)
cf. Sako et al.(2007), Holtzman et al.(2007)
Altavilla et al. (2004)
Bmag = 1.83 * (1/Bsf) + c.
Bmag = 2.28 * (1/Bsf) + c.
Regression line
derived from bluest SN samples
narrower
broader
Method:
Multi-band Stretch Method (UBVRI template)
K-correction : Hsiao et al. (2007)
Branch Normal for all SNe
Distance modulus from recession velocity
inverse B-band Stretch Factor
Number
Redshift
stretched
Redshift
observed
stretched
observed
Day from Bmax
2
Stretch Factor
Absolute Magnitude
Reduced X2 / DOF
Fitting Result
Redshift
Redshift
Stretch vs Stretch
narrower
U
C-C plot
V
redder
narrow
wide
R
(r - i)max
extremely
wide/narrow
I
Nugent spec.
Av = 0
bluer
broader
bluer
narrower
C-C plot
redder
(g – r)max
redder
Relation between LC shape and brightness
narrow
wide
(r - i)max
extremely
wide/narrow
Nugent spec.
Av = 0
Absolute Magnitude
broader
bluer
bluer
(g – r)max
redder
broader
inverse B-band Stretch Factor
narrower
3
LC classification of SN Ia
3.0
X2
if (X2 > 2){
Abnormal LC SN
}else if (Bsf-1 < 0.9){
Broader LC SN
}else if (Bsf-1 > 1.1){
Narrower LC SN
}else{
Normal LC SN
}
Who are the abnormal SNe?
SNe?
Possibilities:
+ (fitting systematics)
+ non type Ia SNe
+ known peculiar SNe Ia (e.g. 91bg-like, 02ic-like)
+ unknown peculiar SNe Ia
broader
narrower
inverse B-band Stretch Factor
Testing on Redshift Evolution
Summary
Absolute Magnitude
・ Multi-band Stretch Method の有効性を確認
・ LCからIa超新星を3つのグループに分類
・ normal グループの超新星の進化を調べた
・ 最も有効なダストの補正方法を調査
・ 補正後の分散がもっとも小さくなる
サンプルを提案
Redshift
4
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