1. A photometric method to classify high-z supernovae found with HSC
Institute of Astronomy, School of Science,
The University of Tokyo
Yutaka Ihara
Mamoru Doi, Tomoki Morokuma,
Naohiro Takanashi, Naoki Yasuda,
SCP collaborations, and SDSS Collaborations

2. Abstract ★ Our goal SN Ia rate at high redshift ( 0.8 < z < 1.4)
★ Method
Classification of SNe → SNe Ia or CC SNe (Ib/c or II)
→Using only Light curves and colors
★ 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.

3. Classification of SNe × × ○ ○ ○ Binary (WD) Ia Si line Core CollapseIb ×
He line
H line Ic × ○
Line shape
IIn
Narrow
Plateau
IIP
Light curve
Linear
IIL

4. Motivation ★ Using only photometric information
★ 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.

5. SN Ia rate SN 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)
※ Delay time is between star formation and SN explosion.
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
We aim at accurate high-z SN Ia rate.
Prompt
Tardy
(Sullivan+2006)

6. Method Type Ia supernovae are detected ! ① Select SN-like light curves
Remove AGN, variable stars
② Classify by LC fittings
Remove Type II supernovae
③ Classify by colors
Remove Type Ib/c supernovae
Type Ia supernovae are detected !

7. LC fitting Method ★ We classify SNe into SNe Ia and core collapse SNe
by fitting observed LCs with template LCs.
Obs. – Temp.
【 χ2 fitting 】　Reduced χ2= ∑n ( )2
/ (n － 3)
error
( n :The number of observing days )
(2) Day of Maximum light
z=0.921, Spec-Ia (SXDF)
(1) Magnitude
Magnitude (i’)
(3) (1+z)×sf
・ Observing data
－Best fitted template (Ia)
Observing date

8. Template(1 of Ia and 12 of II)
II (SDSS-II)
IIP (1999em, 1999gi)
IIn (1998S)
IIL (1979C, 1980K)
Ia (Takanashi+2008)
※ With intrinsic diversity
※ LCs of SNe II at rising phase
corrected by Nugent+2002 (model)

9. 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 observations
are also needed.
→ 1 epoch per month
※ This figure is made from spectral templates of Nugent+2002.

10. 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 (spec-Ia )
z= i’ max = 24.16
Ex (spec-Ia* )
z= i’ max = 23.72
Fitting result = Ia
sf*(1+z)=2.04 i’ max=24.2
Fitting result = Ia
sf*(1+z)=1.76 i’ max=23.7
Fitted very well !!

11. SNe in SXDF (preliminary)
○ Not identified by spectroscopy
○ No spectrum
Ex ( ? )
z= i’ max = 24.01
Ex ( ? )
z= ? i’ max = 24.47 ※
Fitting result = Ia
sf*(1+z)=2.00 i’ max=24.0
Fitting result = Ia
sf*(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)

12. 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

13. Simulation for HSC Obs. Test 2 observing mode for 3 months
(1) 2 epochs per month 30 60 -3 +3
(2) 5 epochs per month -5 -3 +3 +5
★ Various mag at peak & day of peak on observing days
Ex.) 2epoch mode
Peak mag = 24.0
and
Day of peak = 0
= 20
= 40
= 60 24 26 28
(Days)

14. Completeness Contamination 2epochs 5epochs Great! >90%
i’-mag
>1.4
Good >80%
1.2
Good >80%
1.0
Redshift
0.8
Great! >90%
Great! >90%
0.7
0.6
Observing date
Observing date
Contamination
2epochs
5epochs
i’-mag
>1.4
Good <20%
1.2
1.0
Good <20%
Redshift
0.8
Great! <10%
Great! <10%
0.7
0.6
Observing date
Observing date

15. Summary of Observations
1000 SNe Ia will be identified in our HSC observations !
(1) 5 epochs per month for 3 months +1 half night as reference
High-z SNe (z~1.2) with >90% completeness
Highest 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

16. Expected results ? Delay time distribution of SNe Ia can be resolved
by high-z SN Ia rate (z>1).
HSC → 1000 SNe Ia
(z=0.6~1.4 ⊿z=0.2)
~200 SNe Ia of each bin ?
SNLS (z=0.47)
73 spec-Ia samples (0.2<z<0.6)

17. Fin