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High-Redshift Galaxies from HSC Deep Surveys Kazuhiro Shimasaku (University of Tokyo)

High-Redshift Galaxies from HSC Deep Surveys Kazuhiro Shimasaku (University of Tokyo) 1. Galaxy Evolution 2. Dropout Galaxies and Lyman α Emitters 3. Observing Plan 4. Discussion The aim of my talk is practical: To give some idea to refine currently proposed two deep surveys

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High-Redshift Galaxies from HSC Deep Surveys Kazuhiro Shimasaku (University of Tokyo)

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  1. High-Redshift Galaxies from HSC Deep Surveys Kazuhiro Shimasaku (University of Tokyo) 1. Galaxy Evolution 2. Dropout Galaxies and Lyman α Emitters 3. Observing Plan 4. Discussion The aim of my talk is practical: To give some idea to refine currently proposed two deep surveys Apologize to those who are not involved in HSC…

  2. High-Redshift Galaxy Sciences based on the HSC Deep Survey and Ultra Deep Survey • Early galaxy evolution • - Census of LBGs (z~2-9) and LAEs (z~2-7) [DS, UDS] • - Primeval galaxies with large EW(Lyα) and/or extended • Lyα emission (z~3-7) [DS, UDS] • - Escape fraction of Ly continuum from galaxies (z~2-5) [UDS] • Reionization process • - Large-scale ionizing bubbles with LAEs (z~6-7) [DS] • - LF of LAEs and LBGs [DS, UDS] • - Ionizing sources [DS, UDS] • Faint AGN/QSOs (SWANS-Deep, z<6.5) [DS] • Stellar population evolution of galaxies at z<4 [UDS]

  3. 1. Galaxy Evolution

  4. High-z Sciences in This Talk Galaxy Evolution (1) star formation (2) dark-halo growth Far UV LF clustering - Combination of LF and SCF tells us when, what amount of, and in what haloes star formation occurred - Tests for cosmological galaxy formation models - Bases of detailed studies morphology, internal structure, stellar mass, metallicity, gas mass, SMBH, … Reionization When? How? What is the source? Influence on galaxies?

  5. Two Most Important Galaxy Populations (1) Dropout Galaxies (LBGs) Major contributor of cosmic SFR Major ionizing sources at high redshift (2) Lyman α Emitters (LAEs) Youngest and least massive population Probe of reionization - Both are detected in observed-frame optical - HSC and WFS are thus the most powerful instruments to study the fundamental aspects in galaxy evolution near the reionization era

  6. Previous Measurements of LF LBGs LAEs z=4 z=5 z=6 z=7 Bouwens+08 Ouchi+08

  7. Previous Measurements of Clustering LBGs at z~4 LAEs at z~5 large cosmic variance one-halo term z=4.86 z=4.79 KS+04 ~100 objects Ouchi+05 17000 objects

  8. LAEs may not trace the dark-halo distribution Distribution of LBGs and LAEs around a QSO at z~5 blue: LBGs red: LAEs QSO Kashikawa+07

  9. Frontier of LF(LBG) is now at z~7 Ouchi, KS et al. 2009, astro-ph/0908.3191 (ApJ in press) Suprime-Cam y-band surveys detect 22 z-dropouts in 2 FoVs, and constrain the bright end of z=7 LF M* and φ* HST/ WFC3 our data LF continues to decrease at z~7, mainly due to dimming of M*

  10. Some Implications Cosmic SFR Density Ionizing Photon Budget cannot ionize SF activity at z=7 is lower than 1/10 of the peak LBGs can ionize IGM only if Ly continuum escape fraction is higher than ~0.2

  11. Frontier of LF(LAE) is now at z~7 KS+06 (z=5.7) Kashikawa+06 (z=6.5) Ota+08 (z=7.0) Number density decreases with increasing redshift, which may imply increase in neutral fraction. A survey for z=7.3 LAEs is on-going by our group. z=5.7 z=6.5 z=7.0

  12. Importance of z>5 Galaxy formation era - LF decreases rapidly (both LBGs and LAEs) - Cosmic SFRD decreases rapidly - Galaxies with primordial nature Reionization era - Reionization may not complete at z<7

  13. The current measurements lack: Luminosity Function - statistics of bright galaxies at z>5 - overall shape - reliable measurements at z~7 and beyond Clustering (two point CF) - reliable measurements for LAEs - reliable measurements at z>5 - luminosity-dependent clustering (incl. small scale) - mapping of inhomogeneous ionization These can be addressed with the Deep Survey and the Ultra Deep Survey

  14. 3. Observing Plan

  15. LF and SCF Related Science Cases Star formation in young dark haloes - first measurement at z>5 - drastic improvement at z<5 - possible deviation from DH model (esp. LAEs) Reionization process - mapping inhomogeneous ionization with LAEs - ionizing photon budget at z>6 *Unique sample of bright galaxies at z~7-8 Minimum sample sizes requested: precision measurement of LF: 1K precision measurement of ACF: 10K first reliable measurement of LF: 100

  16. Two Deep Surveys with HSC Sky areas should have deep NIR data Cf. SDSS main sample: 0.1 Gpc3, 0.5 million bright (L>L*) galaxies

  17. Expected Numbers (blue:DS, red:UDS) (by M. Ouchi) LBGs LAEs prevous studies prevous studies 10K – 1M objects up to z=6 (DS, UDS) 100 objects at z>6 (UDS) 10K objects up to z=6.5 (DS, UDS) 100 objects at z>7 (UDS)

  18. LBGs LAEs

  19. DS and UDS are complementary Deep Survey: - L>L* galaxies - large-scale clustering Ultra Deep Survey: - L<L* galaxies - z~7 and beyond LF and ACF shapes can be precisely determined from DS + UDS DS is necessary to collect bright objects UDS is necessary to find faint and most distant objects

  20. 4. Discussion

  21. Roles of the two surveys: Only the Ultra Deep Survey can reach z~7 universe. The Ultra Deep Survey can collect similarly large numbers of objects, but it cannot substitute for the Deep Survey, because its area is too small to collect bright objects and to map spatial distribution (esp. for LAEs). Depth and area of each survey: Difficult to justify with factor two precision. Such precision may not fit legacy surveys. But we should do our best to quantify our science cases to win telescope time. Bandpass selection: Must include red filters to make best use of high red sensitivity of CCDs. Also must include narrow-band filters to do unique sciences.

  22. Follow-up observations: LF and SCF just describe the ‘distributions’ of galaxies. Follow-up observations of our huge samples are essential to do astrophysics. DS and UDS provide excellent targets for WFS and next generation telescopes. Importance of spectroscopy: Remove contamination from photometric samples, which is crucial at z>5. 3D distribution - accurate measurement of correlation length - LAE-LBG correlation - Mapping inhomogeneous ionization Sciences with line spectra

  23. How to convince other people of the importance of DS and UDS: DS and UDS are very unique in their depths and widths: they are deep enough to probe reionization era and, at the same time, wide enough to survey cosmological volumes. Only HSC can do such surveys. Thus, rather than trying to quantify sciences and justify the survey parameters precisely, it may be better to emphasize the survey parameters themselves, just as the SDSS did, because the galaxy samples from DS and UDS are overwhelming: 1 million galaxies over 2<z<8 – a high-z version of the SDSS which found 0.5 million L>L* galaxies in 0.1Gpc3. No one can imagine outputs from such huge samples.

  24. Tokyo Atacama Observatory (TAO) 6.5m Infrared Telescope

  25. Excellent IR performance at 5640m above sea level NIR camera and multi-slit spectrograph of ~9’φ Telescope first light is 2016 at earliest but the camera may be attached to Subaru at ~2013 Good for NIR follow-up of HSC surveys - spec identification of z>7 galaxies - line properties such as HeII, CIV - targeted observations (rare objects, primordial clusters) - z>8 LAE survey with help of deep HSC optical images

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