Search for Galaxies at z>~7 in the GOODS-N field

Masami Ouchi(STScI)

Figure credit: Kajisawa

Overview1) Motivation & background of our z>7 galaxy search:I highlight some results from our deep and wide-field sur

vey of Subaru for z=5-6 galaxies.

2) On-going Search for Galaxies at z>~7 in the GOODS-N field with Subaru and GOODS/ACS+IRAC datai) z-dropout galaxy search in a 900 arcmin2 area with an deep

Subaru/Suprime-Cam z' and 1micro-m band (zR) images

ii) z-dropout galaxy search in a 100 arcmin2 area with deep Subaru/MOIRCS J and K and HST/ACS z' images

Terrible (record-breaking?) weather in Hawaii this spring...

• Galaxy formation:z>~5: Epoch of mass assembly

Evolution of neutral fraction of IGM (Fan et al. 2006)

Motivation & BackgroundWhy are Studies of z>5 Galaxies Important?

Evolution of mass function predicted by the CDM model (Sheth & Tormen 1999)

• Reionization:z~6:Epoch of transition

z= 9 7 5 3 1 0

Galaxy

Motivation & BackgroundEvolution of luminosity function and SFRD for dropout galaxies up to z=6

• Number density of bright dropout galaxies significantly decreases from z=3 to 6. • The contribution of UV-bright galaxies to cosmic SFR density drops by an order of mag.

Shimasaku, Ouchi et al. (2005)

Motivation & BackgroundEvolution of Luminosity Function for Ly

α Emitters (LAEs) from z=5.7 to 6.5• Luminosity function of LAEs at z=

5.7 and 6.5, i.e., the transition epoch of reioniztion (z~6)

• Assuming no evolution of intrinsic LF, Lyα luminosity decreases by a factor of 0.4-0.6.

• → XHII<~0.45 at z=6.5 (Kashikawa et al. 2006)

• But, is the assumption correct? (Recall the evolution of LF of dro

pout galaxies from z=3-6.)

• The evolution of LF for star-forming galaxies should be investigated to test the validity of this assumption.

Evolution of luminosity function for Lyα emitters (Kashikawa et al. 2006; c.f. Malhotra & Rhoads 2004)

Motivation & Background Large-Scale Structures of z=5.7 LAEs

Ouchi et al. (2005)

z=5.7±0.05

~40Mpc in line of sight

- Galaxy concentrations connected with filaments

-10-40 Mpc scale voids

Significant clustering of high-z galaxies.

N= 515

Voids

z=5.7 LAEz=6.5 LAE

z=5-6 drop

bias

Angular Correlation

• No significant change in LAE clustering from z=5.7 to 6.5.

• At z~6.5 (preliminary)– Large-scale bias

• b(LAE)=4.54±1.32 b(Drop)=4.23±2.02

DH mass ~1x1011 Mo (c.f. 1012Mo for L>L* LBG at z=3-4)

Model prediction of Furlanetto et al. (2006)

→neutral fraction: xHI<~0.7 Characteristic bubble size: Rc

>~10Mpc

b(z6.6LAE)=4.5±1.3b(z6Drop)=4.2±2.0

Ouchi et al. in prep

Motivation & Background Angular Correlation Function of

z~6 LAEs and Dropouts

2) On-Going Search for Galaxies at z>7

Study of Bouwens et al. (2004)z=7-8 Galaxies Obtained in the HUDF

• Three to five candidates of z=7-8 galaxies are identified in the HUDF • Small in number (3-5) and in area (~6arcmin2) :

– It cannot give a strong constraint on LF. A Larger sample is needed!!

Bouwens et al. (2004)

Our On-going Search (1) Wide-Field (900 arcmin2) z’-dropout search

• We use Subaru/Suprime-Cam and custom zR(1μm) filter to search z’-dropout (galaxies. (Note that Suprime-Cam has red-sensitive CCDs.)

• z’-zR colors discriminate (z=6.6-7.2) galaxies from low-z galaxies and Galactic stars.

• Our target field is a 900 arcmin2 area centered at GOODS-N

Suprime-Cam

Our On-going Search (1) Wide-Field (900 arcmin2) z-dropout search

Area of Subaru/HST z-dropout seach

• Five nights are allocated to take deep zR(1μm)~26.0 (30 hours; Ouchi, Mobasher, Shimasaku, Ferguson et al. )　

• Plan: About 1 magnitude shallower than the NICMOS J image of HUDF, but 150 times larger area.→ ~50 dropouts at z~7 (LF, as well as stellar mass + CF constraints.)

• Fact: These observations were carried out in March 30-April 4, but we could got only 20% of the data because of the poor weather... We will wait for the data until next year.

2) MOIRCS J and Ks imaging• MOIRCS: The new NIR wide-fi

eld camera of Subaru (FoV=28arcmin2)

• In March-April 2006, the MOIRCS team took 100 arcmin2 J and Ks images

• Plan in 2006 – Ultra-deep field with 1 FoV (30 hr

s each for J and Ks) = x7 FIRES (Labbe et al. 2003)

– Deep field with 3 FoVs (5 hrs each for J and Ks)

=slightly deeper than ISSAC GOODS-S

We expect 5 z-dropout candidates.Figure: Kajisawa

2) MOIRCS J and Ks imaging

• We have obtained ~40% of planned data, but about a half of the data were taken under the poor weather conditions. We will continue the observations in the spring of 2007.

1/8 of MOIRCS field (KAB~25.5 at 5sigma; Tanaka et al.)

Summary1) As for the backgrounds of our z>7 galaxy search,

I have highlighted some results from our studies of z=5-6 galaxies, luminosity function and correlation function of dropout galaxies and Lyα Emitters obtained in the Subaru Fields.

2) I have introduced our two on-going efforts of studies of z>7 galaxies in the GOODS-N field.i) z-dropout search in a 900 arcmin2 area with a deep Subaru/Suprime-Cam z' and 1micro-m band (zR) images ii) z-dropout search in 100 arcmin2 area with deep Subaru/MOIRCS J and K and HST/ACS z' images