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Search for Galaxies at z>~7 in the GOODS-N field. Masami Ouchi (STScI). Figure credit: Kajisawa. Overview. 1) Motivation & background of our z>7 galaxy search: I highlight some results from our deep and wide-field survey of Subaru for z=5-6 galaxies.
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Search for Galaxies at z>~7 in the GOODS-N field Masami Ouchi (STScI) Figure credit: Kajisawa
Overview 1) Motivation & background of our z>7 galaxy search: I highlight some results from our deep and wide-field survey 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 data i) 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...
Motivation & BackgroundWhy are Studies of z>5 Galaxies Important? Galaxy • Galaxy formation: z>~5: Epoch of mass assembly z=9 75 3 1 0 Evolution of mass function predicted by the CDM model (Sheth & Tormen 1999) Evolution of neutral fraction of IGM (Fan et al. 2006) • Reionization: z~6:Epoch of transition
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 Lyα 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 dropout 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 & BackgroundLarge-Scale Structures of z=5.7 LAEs z=5.7±0.05 ~40Mpc in line of sight Voids N= 515 • - Galaxy concentrations connected with filaments • 10-40 Mpc scale voids • Significant clustering of high-z galaxies. Ouchi et al. (2005)
Motivation & BackgroundAngular Correlation Function of z~6 LAEs and Dropouts • 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 Angular Correlation z=5.7 LAE z=6.5 LAE z=5-6 drop bias b(z6.6LAE)=4.5±1.3 b(z6Drop)=4.2±2.0 Ouchi et al. in prep
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 Suprime-Cam • 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
Our On-going Search (1) Wide-Field (900 arcmin2) z-dropout search • 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. Area of Subaru/HST z-dropout seach
2) MOIRCS J and Ks imaging • MOIRCS: The new NIR wide-field 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 hrs 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.)
Summary • 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. • 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
