Galactic Archaeology with Subaru: Prospects for Wide-Field Surveys

Masashi Chiba

(Tohoku University, Sendai)with HSC and PFS science working groups

Outline

Background Wide-field photometric survey with

Hyper Suprime Cam (HSC) Wide-field, fiber-fed multi-object

spectroscopic survey with Prime Focus Spectrograph (PFS)

What do we want to know?Formation of the Galaxy in CDM theory

Bright parts arecentrally concentrated

Dark halo in the GalaxyAssembly of CDMBy Moore

Resolved stars provide fossil recordsof galaxy formation process

By Moore

Then, what data do we need?

Photometry : mag., color ( → color-mag. diagram)

Spectroscopy : metallicity , Vrad (kinematics)abundance pattern ( → SFH & chemical evol.)

Astrometry : proper motion, distance (→ 6d phase space)

⇒ galaxy formation and evolution

Subaru/PFS

Subaru/HSC

Gaia

HSC

HSC

(Hyper Suprime Cam)

FOV: 1.77 sq deg (1.5 deg diameter)Pixel scale: 0”.17/pixFilters: grizy + several NBFirst light: Jan., 2012

Prime focus

International collaboration: Japan, Princeton, Taiwan

Funded since 2006

HSC

Wide-field FoV is essential for mapping stars

Subaru Strategic Program (SSP)with HSC (to be submitted)

(dedicated to a newly commissioned instrument: max: 60 nights/year x 5 years)

1. Wide-field survey over ~ 1,500 deg2

cosmology: primary science driver weak lensing, strong lensing, galaxy clusters

other science incl. galactic archaeology

2. Deep and ultra-deep survey galaxy and QSO/AGN evolution

high-z galaxies, re-ionization, z~7 QSOs

HSC white paper(July, 2011)

Planned GA survey with HSC

1. Wide-field survey of the MW outer haloDiscovery of new ultra-faint dSphs and halo streams3 bands (g, r, i), ~ 26 mag (3 mag deeper than SDSS)~1,500 deg2 (fully utilizing weak-lensing survey data)color-magnitude diagram for old MS + RGB stars in the

outer halo (r = 30 – 250 kpc)

2. Deep and wide-field survey of the M31/M33 halo Detailed mapping of stellar halos in M31/M33Use (DDO51-type) NB515 filter centered @ 515 nm

to distinguish halo RGBs with (g, i) + NB515 imagingNB515 is fully optimized for z=3 BAO as well

(Belokurov+ 2006)

UFDs and substructures revealed by SDSS

20 < r < 22

Tollerud +08

Observed photometric properties of Galactic satellites(SDSS)

Single LSST: rlim = 24.5Co-added LSST: rlim =27.5Subaru/HSC(wide-f. survey): rlim~26

satellites

radius

(Bullock & Johnston 2005)Halo realization

Survey of the MW outer halo with HSC

HSC

HSC

HSC survey over ~1,500 deg2

• ~ 20 new UFDs @ Mv<-3• 3~4 new streams with lim~34 mag/”

Stellar halos in M31/M33using (DDO51-type) NB515 filter

CW: 5145 A, FWHM: 80 A

To separate RGBs in M31/M33 from Galactic dwarfs+ optimized for BAO science using z=3 LAEs

Requirement from BAO science(with Y. Matsuda)

Feasibility for LG science(with M.Tanaka)

giants

dwarfs

130 HSC pointings

Deep and wide-field survey of stellar halos in M31/M33 with HSC

Metallicities and RVs of substructuresand satellites with PFS (+ star clusters)

ITRGB=20.5

Ibata+

PFS

PFS

(Prime Focus Spectrograph)

FOV: 1.5 deg in diameter2400 fiber positionersλ: 380~1,300 nm(3 channels: Blue, Red, IR)R: ~3,000First light: 2016

Led by IPMU (U. of Tokyo) + NAOJ/Subaru community+ Caltech/JPL, Princeton, (JHU), LAM, UK, Brazil, Taiwan

Prime focus

Spectrograph design By Jim Gunn

Red

Blue

IR

Key science with PFS(Science white paper, 1st ver. in Jan 2011)

1. Cosmology: primary science driver BAO, lensing

2. Galaxy evolution Galaxies at z ~ 2 and beyond

3. Galactic archaeology Milky Way and Local Group

4. QSO/AGN evolution QSOs at z < 6

1st version of PFS white paper(Jan, 2011)

SuMIRe=Subaru Measurement of Images and RedshiftsThe project name using both HSC and PFS

Many fibers Merging history

GA science goals with PFS

1. Formation of Galactic structures Merging history of the Milky Way (MW)? Formation of old MW components (thick disk, halo)? Star-formation history of dwarf satellites? Formation of M31: is it different from the MW?

2. The nature of galactic dark matter How is dark matter distributed in the MW? Dark matter of dwarf satellites: is CDM correct?

GA science goals with PFS

All of these information are recorded in stars

1. Space and velocity distributions of ancient stars Past collapse and merging events

Tracer of dark matter profiles 　　　　　　　　　　　　　

2. Chemical abundance of ancient stars Star formation and chemical evolution

Phase space

Debris of building blocks

A building block

Helmi & de Zeeuw 2000

Freeman & Bland-Hawthorn 2002

Extracting past merging history: how?

Astrometry with Gaia (precise distances and proper motions) + Vrad & [Fe/H] distrib. with PFSwill resolve each of blocksand its chemical evolution

Accretion time of a satellite can be deducedfrom phase-space distribution of stars

(McMillan & Binney 2008, Gomez+ 2010)

7.9 Gyr 8.9 Gyr 7.6 Gyr

r-

Lz

r-

k

P(k)

Orbital freq.

GA survey plan with PFS

1. The Milky Way survey• Sample:

i. Gaia sample: ~ 106 stars with 18<V<20 (Halo ~55%, Thick disk ~40%, Thin disk ~5%)

ii. Faint sample: stars in 8-9 stellar streams and ~ 105 stars in the outer halo with 18<V<21.5

• Total area: 1,000 + 180 deg2 (560 + 100 pointings)• Survey time: ~30 + 20 = 50 nights

2. The M31 halo survey• Sample: RGBs, V < 21.5• Total area: ~ 230 deg2 (~130 pointings)• Survey time: ~ 30 nights

3. Dwarf galaxy survey• Sample: RGBs, V < 21.5• Survey time: ~ 8 nights (can be PI-led programs)

Summary: GA with Subaru next decade

HSC (2012~)• 1.5 deg FOV, gri+NB515, g<26• Discovery of new UFDs and halo

substructures in the MW• Detailed halo structure in M31/M33

PFS (2016~)• R=3,000, ~2,400 fibers, λ=380-1300 nm, 18<V<21.5• Discovery of kinematical substructures and

merger history in the MW • Dark matter and abundance distribution in

Local Group galaxies

TMT

(Thirty Meter Telescope)

WFOS, IRIS, IRMS,HROS, NIRES etc.R~5,000 for mV<26 magR~50,000 for mV<21 mag

Japan will join TMT

GA with TMTScience Working Group (Stars and Local Group)

led by Wako Aoki

1. Exploring stellar activities and explosions

2. Clarifying galaxy formation with resolved stars

Supernovae, GRB, Seismology, First stars,Extremely metal-poor stars, Our Galaxy,Andromeda, The Local Group and beyond …

Summarized in Science Report (2011)