Searching High-z Supernovae

with HSC and WFMOS

Yutaka Ihara (U. Tokyo/IOA)

Mamoru Doi, Naoki Yasuda,

Tomoki Morokuma, Kohki Konishi, Kouich Tokita

Subaru User’s Meeting 2009/01/14-16 @ Mitaka

AbstractWe will search Type Ia supernovae with HSC and WFMOS.

(1)HSC (Imaging observations)Detect variable objects in high-z galaxies(5-10 nights (epochs) observations give SN light curves. )→~1000 SNe Ia will be obtained for one year (two terms) survey. (2) WFMOS・ ~500 spectra of SNe Ia will be obtained for one year.・ ~1000 spectra of host galaxies of the detected SNe Ia

Our Goal(1) For SN Ia properties

① SN rate study → Progenitor of SNe Ia ② SN Ia spectra → Diversity

(2) For Cosmology・ Resolve the time variation of “Dark Energy”・ Obtain more accurate cosmological parameters (ΩM, ΩΛ, w)

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○

×○

×

How to detect SNe ?(1) Detect variable objects with repeat imaging observations

Example of a SN Ia at z=0.606 (Morokuma+2008)

Reference Another Image Subtracted Image

(2) Classify SNe

① From Spectra (Confirmed method) ② From Light Curves (with Uncertainty)

Ia

II

Filippenko 1997

Why do SNe Ia are important?

© NASA / HST

SN1994D

　　　　 SNe Ia 　　　　　　　　　↓Standard candle in the universe

・ Constant Maximum brightness・ Uniform Light curves and spectra

Measure the expansion of the universe using SNe Ia.

On the contrary…Large systematic errors still exist on the cosmological parameter fit.

Diversity of SNe Iacaused by Progenitors?, Metallicity of Host Galaxies?, Time evolution? or…→ Need more spectra of SNe Ia from low-z to high-z

Very bright (MV~-19.3 mag)

・ Observable at cosmological distances (z~1.5)

Mid-z survey・ SNLS (0.2<z<0.9) ~700 SNe Ia obtained in 2003-07.Imaging: CFHT 4m・ SDSS-II SN survey (0.1<z<0.4)~500 SNe Ia obtained in 2005-07.Imaging: SDSS 2.5m・ ESSENCE (0.2<z<0.9)~200 SNe Ia obtained in 2002-07.Imaging: CTIO 4mHigh-z survey・ SCP (0.3<z<1.4)~30 SNe Ia obtained in 2002 and 2005,6.Imaging: Subaru 8m and HST・ High-z Team (0.2<z<1.6)~30 SNe Ia obtained in 2002-04Imaging: HST

HSC+WFMOS

SN Ia survey

If using HSC (imaging) + WFMOS (spectroscopy), We will get ~1000 SNe Ia for one year survey. Out of them, ~500 SNe Ia are high-z SNe (z>1.0).

Science with SNe Ia

SN Ia rate study→ Many SNe Ia samples are very useful.

MotivationSN Ia rate is the clue of progenitors of SNe Ia

Recently, large delay time distribution of SNe Ia are shown by rate studies.

( “Delay time” → time interval between star formation and SN explosion )

Prompt Tardy

Neill+06(SNLS work)

Nearby results(e.g. Cappellaro+99)

Sullivan+06 ★ Two populations of SNe Ia ? (Mannucci+2005, 2006)

“Prompt” : Short delay time (~0.1-1Gyr) “Tardy” : Long delay time (~1-10Gyr)

High-z rate is important!!It is difficult to measure that from current SN surveys

→ HSC+WFMOS survey

Results of our work and the others

Ihara+09 (SXDS)Dahlen+08(GOODS)Poznanski+07(SDF)Neill+06 (73)(SNLS) z=0.47 Dilday+08 (17)(SDSS) z=0.12

Ihara+09 showsincreasing rates toward z~1.2

At highest-z (z>1.4), very large errors due to small statistics

( Detailed results will be shown in Joint Subaru/Gemini Science Conference)

Expecting Results

?

?

If a major fraction of SNe Ia is “prompt”, SN Ia rates increase toward z~2 (SFR peak), else SN Ia rates decrease.

HSC+WFMOS resolve SN Ia population!!

Diversity of SNe

-0.8 -0.4 0.0 0.4

-0.2

0

.0 0

.2 0

.4 0

.6

U-B

B-V

Though SNe Ia should have uniformed property, diversities of colors, light curves, or spectra are found by large surveys.

→ These diversities affect measuring cosmological parameters.

Ex.1) Color-Color diagram of mid-z SNe Ia

Conley et al. 2008

Kim et al.

Ex.2) Diversity of Light curves

Diversity of SNe

Red 　sample

Blue sample

Tokita 2009 PhD thesis

Corrected diversities with stretch factor, epoch, and MW extinction→ But the diversities still remain…→ Extinction of host galaxies? Metallicity of hosts? Other unknown reasons?

→ Resolve that by large statistic samples of SN Ia spectra( Need large amounts of SNe at each epoch and stretch factor)

Diversity of SNeCorrelation of EW(FeII) and Color of SNe Ia (?) (see detail on Konishi’s Poster)→ SN spectra may be useful to decide color terms of SNe

SALT2 (Light curve fitting method) (Guy+2007)

Color term

● Subaru(SDSS)● SuspectAt max

A few spectra of SNe…Large statistical samples with WFMOSwill find distinct correlations.

Konishi+09 in prep

CosmologyKowalski’s work → Using all SNe Ia obtained by SN surveys or the other works → 307 SNe Ia (after selection cuts)

Enough statistics Errors depend on systematic

Small statistics at z>1 Need more samples

Cosmology• Redshift should be determined well below 1% level

– Difficult only with photometric information

★ Need spectroscopic information– Combine with photo-z of host galaxies?

• Different error properties are expected– Spectroscopy of host galaxies

• Need large observing time

Using WFMOS, Get ~50 SNe Ia spectra at once!!And, get spectra of their host galaxies at the same time.

Cosmology○ Errors on ΩM and w reduce by a factor of 2

Contour : 1σ

Kowalski et al. 2008

HSC+WFMOS

○ The time variation of Dark Energy will be constrained

Summary HSC → Detect ~1000 SNe Ia at z<1.5 WFMOS → Spectra of ~500 SNe Ia and all of the ~1000 host galaxies

This survey will be the largest and the deepest SN survey for the next five years.

① Nature of SNe Ia and their evolution can be explored with large sample.→ SN Ia rate study ( for progenitors)→ Diversities

② Measure cosmological parameters→ ΩM, ΩΛ, w→ The time variation of Dark Energy (?)

~ Fin ~