Yutaka ( NA Ko OJ mi ) yama Gala xy pr & ov Lo ed ca b lyly Un HS iv C erse

I ntroduction

Hyper Suprime-Cam Hyper Suprime-Cam (HSC) –Next generation wide-field CCD Camera –1.5~2 degree FoV covered with 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 Limiting Magnitude (mag) Survey Area (sq.deg) 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 tructure ofGalaxies

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 potential of the galaxy –How frequent do merging events occur? Bullock & Johnston

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] > － 1.1 Blue: [Fe/H] < － 1.1 V < 25 I < 24 Tanaka+ 2008

Color-Magnitude Diagram North-West Tanaka 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 AGBb RGBb 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 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 5Mpc –TRBG ~ 24 mag, HB ~ 28 5Mpc Structure of nearby galaxies (M31 to nearby groups) –More sample galaxies –Dependence on morphology –Dependence on environment LG Sculpter Maffei M81 Canes1 N5128 5Mpc

T he Galaxy

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

Tidal Structure in the Galactic Halo Palomer 5: tidally elongated GC (extended over 10 (Odenkirchen+ 2003) NGC5466: another elongated GC (extended over 4 (Belokurov+ 2006) Stream structures constrain the gravitational potential of the Galaxy SDSS leading trailing SDSS Odenkirchen Belokurov HSC probe the Galactic halo in deep (beyond 100kpc) for wide area

RR Lyrae ~ Galactic structure ~ Vivas & Zinn (2006): QUEST (~400deg 2 ) Sesar et al. (2007): SDSS (~300deg 2 ) RR Lyrae: old stellar population (~>8Gyr)  Galactic halo (sub)structure large amplitude (~ mag) and rapid (T= days) 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 (~1deg 2, Morokuma 2007): 10 HSC: m~26mag, Δt:any, ~100deg 2  ~500 RR Lyrae at R>100kpc distance [kpc] density [kpc -3 ]

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 (0.25deg 2, 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<1kpc shallower & wider might be better...? Good image quality of Subaru is the key Morokuma 2007

U ltra Faint DwarfGalaxi es

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 Globular Clusters 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 Surface Universe Brightness

LG Dwarf Irregular NGC 6822 NGC6822 –Local Group dIrr –M V = -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 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 M B ~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 Coma redshift –goes as deep as 26.2 ABmag (6.0x erg/s/cm 2 ), corresponding to SFR of 2x10 -4 Ms/yr 3 broad band filters: B, R, i’ –Continuum subtraction –Discriminate distant galaxies 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 image Yagi et al kpc H  [SII] Subaru FOCAS MOS observation Covers H  and H  lines with R~700 Measured redshift: Same 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 property 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.