yutaka ( na ko oj mi ) yama gala xy pr & ov lo ed ca b lyly un hs iv c erse
TRANSCRIPT
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Yutaka (
NA
KoOJmi)
yama
Galaxypr
&ov
Loedca bl y UnHSivC
erse
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I nt roduction
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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
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M31 covered by 180 CCDs of Hyper Suprime-Cam
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Mt. Fuji viewed from Mauna KeaMt. Fuji viewed from Tokyo
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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
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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
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S tr uc ture of Galaxies
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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.
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Substructures in M31’s halo
Ibata et al. 2007
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NW
SE
Suprime-Cam M31 Survey(WASSHABI)
Tanaka+ 2008
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Surface Brightness Profile
Inner halo + Outer halo + Substructures
Red: [Fe/H] > - 1.1Blue: [Fe/H] < - 1.1
V < 25I < 24
Tanaka+ 2008
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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
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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
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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)
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• With DDO51 filter, M31 RGB
stars are easily discriminated
from Galactic dwarf stars.
DDO51 filter
giants
dwarfs
giants
dwarfs
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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
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The Galaxy
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“Field of Streams” in SDSS data (Belokurov+ 2006)
SDSS
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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
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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
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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
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U lt ra Fai nt
Dw arf Galaxies
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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
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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
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L ow Sur fa ce
Universe Bri gh tn ess
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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
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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
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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
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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
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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
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Mrk60(D100) H cloud
B,NB,i composite.(B, R, NB composite is on Subaru WWW)
D100
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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
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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
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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.