Theoretical Strategy forHigh-Redshift Galaxy Survey

　　　 Hiroyuki Hirashita (ASIAA, Taiwan)

1. First Metal and Dust Production2. Theoretical Framework and Perspecti

ves for ALMA3. Nearby “Laboratories” of Primeval G

alaxies4. Summary of Strategy

Topics

H, He, Li

C, N, O, …, FeMetal Production History

1. First Metal and Dust Production

Big Bangビッグバン

First Objects inthe Universe

Galaxy Evolution

Stars

Planets

CMB

Cosmic Reionization

0.4 Myr

0.1 Gyr

1 Gyr

13.7 Gyr

Black Holes

Dark Age

Beginning of Metal (dust) ProductionGrasp of “primeval galaxies” in the Universe＝ Understanding of the initial metal enrichment

Subaru

FIRST Project Homepageat Univ. of Tsukuba

Dust already existed atz ~ 6 (Mambo-2:Bertoldi et al. 2003).

Radiative Processes

Dust grains emit far-infrared (FIR) light.

UV, optical, NIR

FIRdust grainsa < 1 mconsidered to be composedby silicate, graphite, etc.

absorption of stellar light

reemission M33: Hinz et al. (2004)

Luminous FIR Emission

Sanders & Mirabel (1996)

Active “starbursts” tend to have dominated FIR emission.

FIR

optical

Important to trace FIR emission in understanding the cosmic star formation history.

Arp 220 at Various Redshifts

SED model by Totani & Takeuchi (2002)Tdust = 42 KLIR = 1.4×1012 L

Detection limits:100 arcmin2 surveywith 500 h (Tamura).Galaxies with 1011 L can be detected (redshift-independent).

Long wavelengths (~ 220 GHz band) are suitable for very high-z.(The field-of-view is also large.)

Fundamental Problems I(1)Understand the first (primeval) stage of galaxy evolutio

n:a. A frontier of galactic astronomyb. First dust (and metal) production (→ origin of the pr

esent metal-rich universe)(2)Quantify the hidden star formation:

a. Importance of FIR seems to be enhanced up to z ~ 1 (Takeuchi et al. 2005).

b. Statistical studies up to z ~ 3 have been made possible by SCUBA (e.g., Chapman et al. 2005), ASTE (Tamura et al. 2008), etc.

⇒ Important to trace the cosmic star formation history.

Theoretical Importance of Dust in Star Formation Scenario

Scenario of Star Formation on Galaxy Scale

Gas pressure ( Temperature) ∝should be kept low.

GravitationalContraction

InterstellarGas

MolecularClouds Cooling by

molecules and dust

Stars

Dust blocks UV radiation.Dust (surface) also helps the molecular cloud formation.

⇒ Dust helps heating and cooling of the interstellar gas.

UV heatingDust supply

Fundamental Problems II(1) Investigate the role of dust in star formation

a. Absorption of UV and emission in FIR UV ⇒heating is suppressed. favorable for star ⇒formation

b. Promotion of molecule formation favorable ⇒for star formation

Transition

molecular clouds

Dust supply

Primeval ISM Evolved ISM

Hirashita & Ferrara (2002); Hirashita & Hunt (2004)

Aim of this Talk(1)Provide a basic simple theoretical tool to construct

a strategy for ALMA high-z survey. ⇒ N-body + Dust enrichment.

(2) Indicate an example what to do until ALMA starts. Analysis and interpretation of AKARI and ⇒

Spitzer data of nearby template of primeval galaxies (blue compact dwarf galaxies).

An aim of ALMA: Detection of the first dust enrichmentin the Universe

2. Theoretical Strategy and Perspectives for ALMA

• N-body Simulation (Suwa et al. 2006)– CDM model Cosmological Simulation– Box Size: (150Mpc/h)3 ⇔ 104 arcmin2

0.6 Gyr 0.9 Gyr

1.2 Gyr

0,3 Gyr

1.5 Gyr 2.2 Gyr

FIRST (Univ. Tsukuba)

Distribution ofdark halos in the Universe.

Model of Dust Enrichment to be applied to individual halos

(1) Dust is supplied by Type II SNe (m* > 8 Msun).(2) Dust per SN = 0.4Msun (Todini & Ferrara 2001; Nozaw

a et al. 2003): initial Mdust = 0(3) Galaxies are treated as one zone.

SFR (t) SN II rate (⇒ t) ⇒ Mdust (t): t: Age of the dark halo

　　　　　　　　　 (Salpeter IMF)

Hirashita & Ferrara (2002); Hirashita & Hunt (2004)

We concentrate on young (t < 1 Gyr) galaxies.

• SFR(t) = t/ Mgas

exp(– t /) : Star formation timescale (= R/vcir)– ~ 0.3 (t <) ~ 0.1 (t > )

LUV and LIR

Estimation

Massive stars3 ～ 100MO

UV radiation

Dust grains(~0.1m)

Absorb UVRadiate IR

IR radiation

Observer

• LUV

= [1-exp(-dust

)]/dust

LUV* (LUV* SFR)∝• L

IR = (1-[1-exp(-

dust)]/

dust) L

UV*

dust

: Optical depth of dust, ∝ Mdust

/R2

Comparison at z ~ 3

Our prediction at z ~ 3

z ~ 2.5

z ~ 1Chapman et al. (2005)

The highest-z statistical sub-mm sample

Further Test (Ongoing)Tamura et al. (2008)Cross correlation between sub-mm (ASTE) galaxies and Ly emitters.If young halos are selected as Ly emitters, we can reproduce the correlation also theoretically.

Comparison with known optical/UV sample may be usefulto test our model.

497 galaxies (L

IR>1011L

O) are found

in (150Mpc/h)3.

Detectable with ALMA.Correlation with clustering of optical sources is good.

Prediction for ALMA Galaxies (L

IR>1011L

O) at z = 6

Results (LIR

>1011LO) at z = 10

30 galaxies (L

IR>1011L

O) are

found in (50Mpc/h)3 ~1000arcmin2

3. Nearby “Laboratories” of Primeval Galaxies

BCDs are nearby “laboratories” of high-z primeval galaxies.

BCD = Blue Compact DwarfsBCD = Blue Compact DwarfsStar formation (blue)Small (compact)Low metallicity ⇒ early stage of evolution

SBS 0335–052 (Z/41) is genuinely young 　 (< 5 Myr).

Vanzi et al. (2000)

D = 53 Mpc

300 pc

Observational Constraints from SBS 0335–052

Vanzi et al. (2000) Vanzi et al. (2000)

Dust is concentrated⇒large

Evolution of dust mass Evolution of FIR lum.

AKARI Observations of BCDs

9 BCDs at = 65, 90, 140 m.

II Zw 40

3 kpc

Mrk 71

3 kpc

= 90 m = 90 m

Hirashita, Kaneda, & Onaka (2008)

This kind of observations are important before ALMA!!

（ Hibi et al. 2007 ）

Dust Temperature

FIR Color-Color Diagram

)m100(/)m140( νν II

main

sub

BCDs are on the same sequence as the MW and the MCstoward the high T extension (30 - 40 K ~ high-z LBGs).

Milky Way

Ichikawa & Hirashita (2008)

4. Summary of Strategy Dust optical depth at z ~ 6 is lower but we can detect a

few tens of galaxies with 100 arcmin2 (Tamura et al.) survey. ←We should observe a known clustered region if we want a statistical sample of galaxies.

We could also detect a few z ~ 10 galaxies. (We should construct a deep (as deep as possible) 220 GHz sample. + A MIR pre-survey may be useful to select extremely high-z galaxies efficiently. Where???)

Nearby BCDs can be used as a scale-down version of high-z star formation. (intense radiation field in low metallicity environment)