A photometric method to classify high-z supernovae found with HSC
description
Transcript of A photometric method to classify high-z supernovae found with HSC
A photometric method to classify high-z supernovae found with HSC
Institute of Astronomy, School of Science,
The University of Tokyo
Yutaka IharaMamoru Doi, Tomoki Morokuma,
Naohiro Takanashi, Naoki Yasuda, SCP collaborations, and SDSS Collaborations
Abstract
★ MethodClassification of SNe → SNe Ia or CC SNe (Ib/c or II)→Using only Light curves and colors
★ Our goalSN Ia rate at high redshift ( 0.8 < z < 1.4)
★ Previous Observations (Suprime-Cam/Doi et al. 2002)
More than 100 SNe in SXDF (Subaru/XXM-Newton Deep Field)
→ ~50 are SNe Ia ( SXDF = 5 fields of view of Suprime-Cam )
★ If we use Hyper Suprime-Cam…→ 1000 high-z SNe Ia in one observing mode.
Classification of SNe
H line
Si line
He line
Line shape
Light curve
Ia
Ib
Ic
IIn
IIP
IIL
○
Narrow
Plateau
Linear
Binary (WD)
Core Collapse○
×○
×
Motivation ★ Spectroscopy is the best method to identify SNe.
→ But, it is impossible to get all spectra of SNe.
★ Using only photometric information ( Light curves and colors )
The classification includes some incompleteness. (Some SNe Ia may regard as II, or SNe II may regard as Ia. )
SN Ia rate can be obtained by these samples with estimation of incompleteness.
SN Ia rateSN Ia rate is the clue of progenitors of SNe Ia
★ Two populations of SNe Ia ? (Mannucci+2005, 2006)・ “ Prompt” ・・・ Short delay time (~1Gyr)・ “ Tardy” ・・・ Long delay time (~10Gyr)
SNLS (Neil+2006, Sullivan+2006)73 mid-z SNe Ia → error is small
GOODS (Dahlen+2004)High-z, but ~1-10 SNe Ia → error is large
Prompt Tardy
We aim at accurate high-z SN Ia rate.
(Sullivan+2006)
※ Delay time is between star formation and SN explosion.
Method
① Select SN-like light curves
② Classify by LC fittings
Remove AGN, variable stars
Remove Type II supernovae
③ Classify by colors
Remove Type Ib/c supernovae
Type Ia supernovae are detected !
LC fitting Method ★ We classify SNe into SNe Ia and core collapse SNe
by fitting observed LCs with template LCs.
【 χ2 fitting 】 Reduced χ2= ∑n
Observing date
Mag
nitu
de (
i’)
・ Observing data- Best fitted template (Ia)
z=0.921, Spec-Ia (SXDF)
(3) (1+z)×sf
(2) Day of Maximum light
(1) Magnitude
Obs. – Temp.error / (n - 3)
( n :The number of observing days )
( )2
Template(1 of Ia and 12 of II)
Ia (Takanashi+2008) ※ With intrinsic diversity
IIL (1979C, 1980K)
IIP (1999em, 1999gi)II (SDSS-II)
※ LCs of SNe II at rising phase corrected by Nugent+2002 (model)
IIn (1998S)
Color information ★ We can classify SNe into SNe I and SNe II by light curves.
→ Light curves of SNe Ia and Ib/c are similar.
★ Excluding SNe Ib/c from SNe Ia by color (Rc – i’ vs i’ – z’)
At Max (epoch=-3~3)
Rc and z’-band observationsare also needed.
→ 1 epoch per month
※ This figure is made from spectral templates of Nugent+2002.
SNe in SXDF (preliminary)Field-1 (center) of SXDF = 1 field of view of S-cam ( 34’×27’ = 0.918deg2 )20 SNe are discovered in 2002. ( 8 epochs in 3 months )→ Out of 20 SNe, 12 are Ia, and 8 are CC.
Ex.1 1-175 (spec-Ia ) z=0.921 i’ max = 24.16
Fitting result = Iasf*(1+z)=2.04 i’ max=24.2
Ex.2 1-258 (spec-Ia* ) z=0.928 i’ max = 23.72
Fitting result = Iasf*(1+z)=1.76 i’ max=23.7
Fitted very well !!
SNe in SXDF (preliminary)○ Not identified by spectroscopy
Ex.3 1-242 ( ? ) z=0.823 i’ max = 24.01
Fitting result = Iasf*(1+z)=2.00 i’ max=24.0
○ No spectrum
Ex.4 1-018 ( ? ) z= ? i’ max = 24.47
Fitting result = Iasf*(1+z)=2.52 i’ max=24.7
They are possible Ia by LC !!
※
※ Their redshift will be estimated by phot-z of host-galaxies (Future work)
Simulation for HSC Obs. ★ Using i’-band of Hyper Suprime-Cam
・ High-z SNe Ia (z~1). → observed i’ = rest U - B ・ The limiting magnitude is 26.3 mag (Each exposure time = 3600 sec) ・ Peak magnitudes of SNe are 23.0~25.5 mag. → z=0.6~1.4
★ Make simulated ~1000 LCs of SNe Ia and II from the template LCs
★Check Completeness & Contamination
Simulation for HSC Obs.Test 2 observing mode for 3 months
(1) 2 epochs per month
-3 +3(2) 5 epochs per month
+3 +50-3-5
0 30 60
★ Various mag at peak & day of peak on observing days
-20 0 30 60 (Days)
24
26
28
Ex.) 2epoch modePeak mag = 24.0andDay of peak = 0 = 20 = 40 = 60
Completeness
Contamination
2epochs
2epochs 5epochs
5epochs
Great! >90%Great! >90%
Good >80%
Great! <10%
Good <20%
Great! <10%
Good <20%
Good >80%>1.4
1.2
1.0
0.8
0.7
0.6
>1.4
1.2
1.0
0.8
0.7
0.6
i’-mag
i’-mag
Red
shift
Red
shift
Observing date Observing date
Observing dateObserving date
Summary of Observations
(1) 5 epochs per month for 3 months +1 half night as reference
High-z SNe (z~1.2) with >90% completenessHighest SNe (z~1.4) with ~80% completeness
(2) 2 epochs per month for 3 months + 1 half nights as reference
High-z SNe (z~1.0) with >90% completeness
1000 SNe Ia will be identified in our HSC observations !
Expected resultsDelay time distribution of SNe Ia can be resolved by high-z SN Ia rate (z>1).
SNLS (z=0.47)73 spec-Ia samples (0.2<z<0.6)
HSC → 1000 SNe Ia(z=0.6~1.4 z=0.2)⊿~200 SNe Ia of each bin
?
Fin