High-Redshift Galaxies from HSC Deep Surveys

Kazuhiro Shimasaku(University of Tokyo)

1. Galaxy Evolution2. Dropout Galaxies and Lyman α Emitters

3. Observing Plan4. 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…

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]

1. Galaxy Evolution

Galaxy Evolution(1) star formation(2) dark-halo growth- 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?

Far UV LFclustering

High-z Sciences in This Talk

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

Previous Measurements of LFLBGs LAEs

Bouwens+08

z=4z=5z=6z=7

Ouchi+08

Previous Measurements of Clustering

Ouchi+05

KS+04

LBGs at z~4 LAEs at z~5

one-halo termlarge cosmic variance

z=4.86

z=4.79

17000 objects

~100 objects

LAEs may not trace the dark-halo distribution

Kashikawa+07

blue: LBGsred: LAEs

Distribution of LBGs and LAEs around a QSO at z~5

QSO

Frontier of LF(LBG) is now at z~7Ouchi, 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*

LF continues to decrease at z~7, mainly due to dimming of M*

HST/WFC3

our data

Cosmic SFR Density Ionizing Photon Budget

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

Some Implications

cannot ionize

KS+06 (z=5.7)Kashikawa+06 (z=6.5)Ota+08 (z=7.0)

Number density decreaseswith 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

Frontier of LF(LAE) is now at z~7

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

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

The current measurements lack:

3. Observing Plan

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

Two Deep Surveys with HSC

Deep Ultra Deep20 FoVs (40 deg2) 2 FoVs (4 deg2)

u, g, r, i, z, y u, g, r, i, z, yNB387, 816, 921 NB387, 526, 717, 816,

921, 101(or973)2-3 hr/pix/band 20-30 hr/pix/band

80 nights 70 nights0.3Gpc3/Δz=1 0.03Gpc3/Δz=1

0.03Gpc3/Δz=0.1 0.003Gpc3/Δz=0.1

Cf. SDSS main sample: 0.1 Gpc3, 0.5 million bright (L>L*) galaxies

Sky areas should have deep NIR data

Expected Numbers (blue:DS, red:UDS)(by M. Ouchi)

LBGs LAEs

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)

prevous studiesprevous studies

DS UDSz~2 2E+6 1E+6z~3 1E+6 4E+5z~4 5E+5 3E+5z~5 1E+5 7E+4z~6 1E+4 2E+4z~7 100z~8 30

DS UDSz~2.2 2E+4 6E+3z~3.3 8E+3z~4.9 3E+3z~5.7 1E+4 3E+3z~6.5 1E+4 4E+3z~7.0 70

LBGs LAEs

Deep Survey: - L>L* galaxies - large-scale clustering

Ultra Deep Survey: - L<L* galaxies - z~7 and beyond

DS and UDS are complementary

LF and ACF shapes can be precisely determined from DS + UDSDS is necessary to collect bright objectsUDS is necessary to find faint and most distant objects

4. Discussion

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.

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

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.

Tokyo Atacama Observatory (TAO)6.5m Infrared Telescope

Excellent IR performance at 5640m above sea levelNIR camera and multi-slit spectrograph of ~9’φTelescope 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