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FastSound A BAO Survey in NIR using Subaru/FMOS

FastSound A BAO Survey in NIR using Subaru/FMOS. 戸谷 友則 TOTANI, Tomonori (Kyoto University, Dept. Astronomy) Decrypting the Universe Large Surveys for Cosmology Royal Observatory of Edinburgh, UK, 2007, Oct 24-26. KYOTO FMOS. Subaru/FMOS. F iber- M ulti- O bject S pectrograph NIR

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FastSound A BAO Survey in NIR using Subaru/FMOS

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  1. FastSoundA BAO Survey in NIR using Subaru/FMOS 戸谷 友則 TOTANI, Tomonori (Kyoto University, Dept. Astronomy) Decrypting the Universe Large Surveys for Cosmology Royal Observatory of Edinburgh, UK, 2007, Oct 24-26

  2. KYOTO FMOS Subaru/FMOS • Fiber-Multi-Object Spectrograph • NIR • 400 fibers in 30’ diameter • A Second Generation Common Use Instrument for the Subaru Telescope • Collaboration with:Japan (Kyoto) UK(Oxford, Durham, RAL) Australia(AAO) • Schedule • Engineering F.L.: Jan 2008 • Guaranteed Time Obs starts from mid 2008

  3. Specification of FMOS • 400 fibres in circular FOV (30’ Φ) • Each fiber (1.25”) covers 1’ radius FOV • wavelength coverage: 0.9um - 1.8um • fully covered in a low resolution mode • Spectral resolution • Low resolution mode: R=500 • High resolution mode: R=2200 • Limiting magnitude (1 hr, S/N=5) • J ~ 22.0 • H ~ 20.0 • Line ~ 6 x 10-17 erg/s/cm2 (Latest number from M. Tamura) • OH airglow suppression system

  4. Quick Look of FastSound • BAO search by Subaru/FMOS with NIR spectroscopy • Hα emitting galaxies、z~0.5-1.7 • planned parameters: • ~600,000 galaxies • ~300 deg2 • O(100) Subaru nights • The name stands for ... • FAST: FMOS 暗黒振動探査 (FMOS Ankoku Shindou Tansa = FMOS dark oscillation survey) • SOUND: Subaru Observation Understanding Nature of Dark Energy • Status: • Survey design and plan now under study • Recognized as important the potential largest program in the FMOS team • final survey design by using real FMOS data (next year) • Proposal to be submitted to Subaru after that

  5. Unique/Good Points of FastSound • BAO survey in NIR with a 8m telescope • Unique redshift range by Hα in NIR (z~0.5-1.7) • redshift desert of 1.3 < z < 2.5 in optical spectroscopy • 0.5 < z < 1.3 by [O II] • 2.5 < z < 3.5 by Lyα • Targeting the first detection of BAO at z>1 by galaxy surveys • would remain as important BAO data even in WFMOS era • Hα is a better tracer of SFR than [OII] or Lyα • Photometric target selection likely easier • Instrument available soon!

  6. BAO Search by FMOS. 1 • Required Survey Area to achieve V~ 1Gpc3 • 300 deg2 ⇔ ~ 1 Gpc3 for z~1-1.5 • 1500 pointings required for FMOS-FOV (0.2 deg2) • Required number of galaxies • ~20,000 galaxies per deg2 and unit z for the cosmic variance to dominate shot noise (nP >~ 1) • ~1,800,000 galaxies in 300 deg2 • 1,200 galaxies for 0.2 deg2 (FMOS-FOV) and Δz=0.3 • should be compared the 400 fibers of FMOS

  7. BAO Search by FMOS. 2 • Necessary number of nights: ~O(100) • 1500 (FOVs) / 10 (FOVs/night) = 150 nights • Sensitivity to the Hα Flux: • FMOS S/N=5 (1hr)  F(Hα) ~ 6 x 10-17 erg/s/cm2 • L(Hα) = 9.1 x 1041 erg/s • galaxy with SFR = 6.9 Msun/yr @ z=1.5

  8. Effective Volume:Comparison with Other Surveys BAO peaks ~200 nights ~20 nights Eisenstein+ ‘05 σP/P~(4πk2dk Veff)-1/2

  9. FMOS Survey Simulation (1) 300 deg2, 600,000 galaxies (400 galaxies per FMOS FOV) b=2

  10. Scientific Goals • Stage 1: • ~50 nights (not very difficult to get as a Subaru large program) • may not clearly detect BAO, but may see some evidence • precise measurement of P(k) at z~1 • P(k) measurement is important for cosmological parameters, even without BAO • Use P(k) shape to derive cosmological constraints (c.f. WMAP+2dF, WMAP+SDSS, …) • z~1 is important for dark energy • Stage 2: • ~a few hundreds nights • clear detection of BAO • more robust constraint on dark energy than Stage 1 • Ancillary sciences: • Properties of z~1 star formation galaxies • A small fraction of fibers for spectroscopic survey of rare objects

  11. Key Questions • Do we have enough number density of galaxies with sufficiently strong Hα flux? • Can we select them efficiently by photometric information? • Do we have sufficient photometric data, or can we obtain them in the near future?

  12. Some Tests for Target Selections • Estimate Hα flux from photo-z by using SDF/SXDF data (~1deg2) • BVRizJK+Spitzer • There are sufficent number of Hα bright galaxies at z<1.4 • z>1.5 galaxies may not be sufficient enough FMOS line sensitivity (1hr, SN=5)

  13. A Candidate Imaging Catalog for Target Selection:CFHT-Wide Synoptic Survey -almost correct area -deep enough for Fast Sound -five band photometries for target selection

  14. The Most Crucial Question • Can we get such a large observing time of Subaru?

  15. The Future of Subaru Large Programs • So far: • Maximum 20 nights for open use • A new opportunity: The Subaru Strategic Observation Programs • Two categories • A historical survey program • A systematic project with a clear scientific objective • <~60 nights / yr, up to ~5 yrs  maximally 300 nights • Responding to the commission of a new instrument • the first call for proposal (for HiCiao+AO) now under review process • “Subaru Strategic Exploration of Exoplanets and Disks with HICIAO/AO188”, PI: M. Tamura • Next call will be for FMOS

  16. The Roadmap (almost) certainly • Stage 0: pilot survey using a fraction of FMOS GTO (2008) • test of target selection criteria • optimization of the survey parameters • formal proposal to Subaru for a large program • Stage 1: using ~50 nights, ~60 deg2 (2009-?) • precise measurement of P(k) at z~1 • hopefully evidence for BAO • Stage 2: ~200 deg2 survey • Possible input imaging data: CFHTLS-W • a good chance for detecting BAO • Stage 3: ultimate >300 deg2 survey • clear detection of BAO • but needs another source of imaging catalog for target selection likely possibly Who knows!?

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