Yutaka (

NA

KoOJmi)

yama

Galaxypr

&ov

Loedca bl y UnHSivC

erse

I nt roduction

Hyper Suprime-Cam

• Hyper Suprime-Cam (HSC)– Next generation wide-field CCD Camera – 1.5~2 degree FoV covered with 100-180 red-sensitive CCDs– Conceptual design in progress– Target First Light: 2011

• Subaru will have much wider FoV

among 8m class telescopes – Local objects: apparent size is

large (e.g. M31 ~3deg Dia. )– HSC: Ultimate imaging instrument

for exploring the local universe

M31 covered by 180 CCDs of Hyper Suprime-Cam

Mt. Fuji viewed from Mauna KeaMt. Fuji viewed from Tokyo

What can be done with HSC

21 22 23 24 25 26 27 28 29 30

Limiting Magnitude (mag)

Sur

vey

Are

a (s

q.de

g)

0.1

1

10

1

00

10

00

1000

0

SDSS

Suprime-Cam

HSC Survey

Typical Surveys

fainter, more distant objects

rare objects, statistics

What can be done with HSC

• Structure of nearby galaxies (M31 to nearby groups)• Structure of the Galaxy• Ultra-faint dwarf galaxies• Low surface brightness universe

Many thanks to Collaborators !M. Tanaka, M. Chiba, P. Guhathakurta, T. Morokuma,M. Yagi, M. Yoshida, N. Kashikawa

S tr uc ture of Galaxies

Why care about stellar halos?

• Laboratory to test hierarchical galaxy formation– Tidal debris of merging galaxies survive for several Gyrs in the halo

since the dynamical timescale is long there – Orbit of stream structure strong constraint for the gravitational p

otential of the galaxy– How frequent do merging events occur?

Bullock & Johnston. 2005.

Substructures in M31’s halo

Ibata et al. 2007

NW

SE

Suprime-Cam M31 Survey(WASSHABI)

Tanaka+ 　 2008

Surface Brightness Profile

Inner halo ＋ Outer halo ＋ Substructures

Red: [Fe/H] > － 1.1Blue: [Fe/H] < － 1.1

V < 25I < 24

Tanaka+ 　 2008

Color-Magnitude Diagram

North-West

Tanaka+ 　 2008

• The width of RGB gets narrower as it goes outkirts– indicating metallicity gradient exists

• Our survey goes well below Red Clump

Features in Color-Magnitude Diagram

• AGB bump (AGBb): Clustered feature of AGB stars at the beginning of He shell-burning evolution

• Red Clump: Clustered feature of red HB (He core-burning) stars being metal-rich / young age

age indicator of stellar population (once metallicity is determined)• Suprime-Cam data enable us to investigate the properties of stellar population

AGB bump

Red clump

Tanaka+ 　 2007b

AGBbRGBb

HB

Alves & Sarajedini 1999

Mean Age ～ 9.6 Gyr

HSC M31 Halo Ultimate Imaging Survey

• HSC can image as deep as below HB/RC in 1 hour under moderate seeing condition (~0”.7)

• 81 HSC (2deg case) pointings are required to cover 254 sqrdeg (x2 the field size of Ibata et al. 2007 survey)

• Total: 20 nights required– 2 color bands (V, I)

• With DDO51 filter, M31 RGB

stars are easily discriminated

from Galactic dwarf stars.

DDO51 filter

giants

dwarfs

giants

dwarfs

Toward Nearby Groups

• Similar investigation can be applied for galaxies in nearby groups. HSC is suitable for such observations; – 1.5deg corresponds to 130kpc @ 5Mpc– TRBG ~ 24 mag, HB ~ 28 mag @ 5Mpc

• Structure of nearby galaxies

(M31 to nearby groups)– More sample galaxies– Dependence on morphology– Dependence on environment

LGSculpter

MaffeiM81

Canes1

N5128

5Mpc

The Galaxy

“Field of Streams” in SDSS data (Belokurov+ 2006)

SDSS

Tidal Structure in the Galactic Halo• Palomer 5: tidally elongated GC (extended over 10 deg) @d=25kpc

(Odenkirchen+ 2003)• NGC5466: another elongated GC (extended over 4 deg) @d=16kpc

(Belokurov+ 2006)• Stream structures constrain the gravitational potential of the Galaxy

SDSS

leading

trailing

SDSS

Odenkirchen+ 2003Belokurov+ 2006

HSC probe the Galactic halo in deep (beyond 100kpc) for wide area

RR Lyrae ~ Galactic structure ~

Vivas & Zinn (2006): QUEST (~400deg2)

Sesar et al. (2007): SDSS (~300deg2)

RR Lyrae: old stellar population (~>8Gyr) Galactic halo (sub)structure large amplitude (~0.5-1.0mag) and rapid (T=0.3-0.5days) variable stars

• SDSS, QUEST can not effectively detect variability of RR Lyrae at the outermost region of our Galaxy (R>100kpc). • 4 RR Lyrae candidates at R>150kpc in the SXDF (~1deg2, Morokuma 2007):

10

HSC: m~26mag, Δt:any, ~100deg2

~500 RR Lyrae at R>100kpc

distance [kpc]

density[kpc-3]

0.01

0.1

10

1

100

High proper motion objects (HPMOs)

Richer et al. (2000)

- Search for Galactic halo white dwarfs- kinematics of Halo stars

reduced proper motion diagram

~20 HPMOs (>0.13arcsec) in the SDF (0.25deg2, Suprime-Cam 1 FOV, Morokuma 2007)

- Age of WD, WD LF age of our Galaxy- MACHO

HSC: V~28mag, delta-t>3yrs, ~10deg2 ~1000 HPWDs at d<1kpcshallower & wider might be better...? Good image quality of Subaru is the key

Morokuma 2007

U lt ra Fai nt

Dw arf Galaxies

Ultra Faint Dwarf Galaxies

• SDSS: discoveries of Milky Way companion dwarf “galaxies” comparable or even fainter than globular clusters!– “they might be just the first

of a vast population of ultra-faint dwarf galaxies surrounding the Milky Way system that is yet to be discovered” (van den Bergh)

Belokurov+ 2007

GlobularClusters

SDSS

Ultra Faint Dwarf Galaxies

• These galaxies are metal poor and dark matter dominated

Simon & Geha 2007

HSC :

• Search for ultra faint dwarf galaxies which are companions to M31

• Relation with missing satellite problem

L ow Sur fa ce

Universe Bri gh tn ess

LG Dwarf Irregular NGC 6822

• NGC6822– Local Group dIrr– MV = -16– 500 kpc from MW– Ongoing SF activity

• Viewed in HI– Embedded in a huge HI

envelope– Stellar population / SF

activity in the HI envelope was unknown

Suprime-Cam is the best instrument for investigating the HI envelope

HI map from deBlok&Walter 2002

1 degree1 degree

Image from DSS

画像• Subaru + Suprime-Cam

– 2 fields

– B band : 24min

– R band : 36min

– I band : 22min

– 0”.8 PSF FWHM

– Limiting Mag: B~26mag

MB~0.5mag

Komiyama et al. 2003

NGC 6822: Spatial Distribution

• Intermediate-age to old population (>1Gyr) traced by red-tangle stars

– Spherical Distribution → main component of

the galaxy

• Young population (<1Gyr) traced by main-sequence stars

– Elongate distribution

Trace the HI envelope

Reveals the low surface brightness star-formation

activity in the HI envelope for the first time

Suprime-Cam H Imaging of Galaxy Clusters

• Extended H emission line region (without stellar component) found for NGC 4388 in the Virgo cluster (Yoshida et al. 2002, 2004)

• Ram pressure stripping is the most plausible explanation– Environmental process special to galaxy clusters?

• How rare? Dependence on environment ? Morphology/Star formation property of host galaxy ?

Yoshida et al. 2002, 2004

Suprime-Cam Coma Cluster H Imaging Survey

ACS pointing

Panchromatic data are available for this region

• Narrow-band filter c=6714A, FWHM=130A– sample Hα line @ Coma r

edshift– goes as deep as 26.2 AB

mag (6.0x10-18 erg/s/cm2), corresponding to SFR of 2x10-4 Ms/yr

• 3 broad band filters: B, R, i’– Continuum subtraction– Discriminate distant galaxi

es• 3 different fields

Mrk60(D100) H cloud

B,NB,i composite.(B, R, NB composite is on Subaru WWW)

D100

Mrk60(D100) H cloud

What's this !?

NB-R imageYagi et al. 2007

60kpc

H [SII]

Subaru FOCAS MOS observationCovers H and H lines with R~700Measured redshift: 0.018Same redshift as D100 confirmed

D100

2kpc

Suprime-Cam Coma Cluster H Imaging Survey

• >10 such faint extended emission line regions are found for 3 FoV in the Coma cluster (e.g. RB199, Yoshida et al 2008)– How rare? – Dependence on environment

? – Morphology/Star formation pr

operty of host galaxy ?– Role on galaxy evolution ?

RB199 (Yoshida et al. 2008)HSC :

• HSC is a powerful tool to survey such faint emission line regions

• Understand the environmental effect on the galaxy evolution in dense clusters

Summary

• Structure of nearby galaxies– M31 and out to galaxies in nearby groups

• Structure of the Galaxy– Search substructures beyond ~100kpc– Halo structure traced by RRLyr– WDs age of the Galaxy, IMF

• Ultra faint dwarf galaxies– M>8mag dwarf galaxies around M31– Missing satellite problem

• Low surface brightness universe– Outskirts of local galaxies– Local galaxy clusters

These topics are expected based on our experiences of SDSS/Suprime-Cam.Unexpected and exciting findings will be brought by HSC.