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.
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