From FOCAS to WFMOS???for deep galaxy studies

Youichi OhyamaASIAA (Taiwan)

Abstract• I was asked by SOC to give my comments.• This is a “WFMOS business” session.

– WFMOS is great. No doubt.• Judging from all previous talks.

• WFMOS の決断をする（？）前に、頭のストレッチ。• Diversity?

– Noted by Sutou san.– Then, what kind?

• Which way to go for diversity?– World’s ideas– YO’s idea (?)

• The talk is biased for “ 田舎のネズミ” .• 悲劇の繰り返しは WFMOS で本当に回避されるか？

WFMOS era?

• Target years: 2016– 7 years from now– FOCAS: 16(?) year old.

• Already retired.• HDS also retired?• No optical spectrograph of our own for some years?

– GMOS will also retire.• May be no direct replacement

– JWST: 3 year old.– TMT has just arrived.

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WFMOS

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Perspective of Future Subaru Instrument UsageGEMINI

w/o GMOS

File from “Subaru’s decision for 2020” conf.

What shall I do with WFMOS? 1

• WFMOS: the Monster Spectroscopy Surveyor– >1500 fibers, 1.5deg fai FOV!

• How shall this monster fit my science?– AKARI NEP survey?

• DEEP: ~<1 deg fai, WIDE: ~3 deg fai– Too small to fit the WFMOS FOV and its survey size.

– AKARI all-sky survey?• FIR (FIS) bright sources: 4E4 sources/4pi

– Only a few sources in a WFMOS FOV– Too sparse (and probably too bright) for WFMOS

What shall I do with WFMOS? 2

• To Improve/extend existent FOCAS science• From my works:

– Z=3.1 LyA blob, long slit (LS)– Z=3.6 LyA nebula around RG, LS– Z=4.7 QSO companion at LyA, LS (2 slit PA)

• Compact but slightly extended (~several arcsec)• Medium-deep spectroscopy (Texp=1~6 h).• Rather rare objects

• Demands– Spatial information and good sky sub.

• Need slits

What shall WE (FOCAS users) do with WFMOS?

• From other FOCAS science highlights (for high-z studies):– Z>6.6-6.9 LAEs

• Z-band sensitivities, good sky sub., rather rare.– Z~6.6 HIMIKO (extended LAE or high-z blob)

• spatial info., good sky sub., rather rare.– Z>6 GRB

• Timing (ToO), Z-band sensitivity, accurate sky sub.– Z~5.7 LAE Clumps

• I~Z sensitivity, good sky sub.– Z~5 LBGs (absorption)

• R~Z sensitivity, accurate sky sub.– Z~3.1 LABs

• FOV, spatial info.– Z~>1 SNe for cosmology

• Timing (ToO)– Z~1.0 clusters

• FOV– …

Blue: WFMOS will fit the projectRed: WFMOS might have some troublesGreen: WFMOS seems OK,

but too much powerful/not optimized

What has been MISSing so far with FOCAS science

• Big survey (due to smaller FOV)• Analyses of stellar spectra (absorption) for hihg-z so

urces (z>3)– Not just LyA emission between OH lines,– But with narrow absorptions beneath SKY.

• Second-line science for high-z emitters– HeII from extreme LyA emitters (PopIII candidate)– LyA blobs seen in other lines

• excitation, true velocity field

• This is partly due to 10000A wall.

What shall we do to EXTEND FOCAS success

An example of LAE search• Why not go beyond the IOK-1?

– Search for LAEs beyond z>7– Search for very ‘first light’ in the universe

• Many teams were inspired by Subaru’s success, and have been moving forward.– Examples…

DAZLEDark Ages Redshift ‘Z’ Lyman Explorer

• Dedicated NB NIR imager for VLT– Search for Blank-field LyA emitters at z=7.7– 1056nm and 1063nm NBs, FWHM=1nm

F2T2Flamingos-2 Tandem Tunable Filter

• Fully-tunable across YJ• Tandem etalons for better OH blocking• Narrow FOV for targeted cluster lenses• Option: With AO• JWST TFI prototyping

FBG: Fiber Bragg Grating• Optical fibers to eliminate only OH lines

– OH suppression over 98%– While keeping 90% throughput at JH

• Proposed for TMT instrument R&D

FBG simulation• The case with 30m

– But improvement with 8m is also expected• Amazing…

FLEX: First Light Explorer

• IFU with bundled FBGs• Ultimate sensitivity for first-light source

s, at JH, though small FOV– Z=6~13– 1”X1”, 91 element IFU– With AO at VLT

• But first to install existing spectrograph

Common keywords

• Dedicated instruments– Fully-tuned for a single purpose

• Innovative OH suppression device– ‘Photonics’, tandem Etalon

• Prototyping new technology for even future instruments– Space application, TMT

• Niche?

Niche?:driver of new technology for future!• “Niche” as explained in WIKIPEDIA.jpニッチ（ Niche ）とは直訳すれば「隙間」や「くぼみ」の事

であり、もともとは生物学で生態的地位を表す用語である。様々な生態的地位がある中、主に哺乳類の進化に伴って起きた事柄がニッチ市場の概念の元になったとされる。中生代に恐竜・首長竜などの爬虫類が陸海空問わず栄えていた頃、哺乳類はネズミのような姿で目立たず、活動も夜行・雑食など隙間的なものを主としていた。約 6500 万年前に恐竜などが滅びると絶滅で空白になったニッチ（生態的地位）を埋めるために様々な生物が進出し、哺乳類が最も成功を収めたといわれる（空は鳥類）。この生物を企業などに擬して「ニッチを開拓する」などとも言う。なお同種の現象は過去何回かの大量絶滅の後にも現れた

Naive idea from our(?) demands

Faint Spectrographoptimized for High-Z Studies

• Optimized for deep zYJ spectroscopy– for 2nd line science– stellar feature analyses

• Faint Object zYJ Spectrograph (FOCAS-zYJ)– Last frontier(?) accessible without innovative device– Concepts

• Optimized for zYJ– 8000-13000AA– + 4000A room at redward of current limit for new science

• Better sensitivity and S/N at zYJ– to achieve FOCAS- and/or DEIMOS quality

» Sky-sub conscious» NIR chips

A bit more on Spec.• To maximize sensitivity at zYJ

– NIR chips (Hawaii-II?)• to be more red sensitive than Hamamatsu’s CCDs

– Simple optics and thought-put oriented design– Medium-resolution (R>~5000) for OH software suppression

• Very low readout noise NIR chip (~6e RMS)– To be read-out limited even beyond 10000A

• Flexure compensation to ensure good OH subtraction.

• Simple fabrication– No needs for optics cooling

• Options– AO (GLAO) or MOS (room temp), NBs (room temp)– Optimization for Keck

• To achieve DEIMOS FOV

People’s opinion:• “Pushing the VLT spectroscopy of Distant Galaxies

to the Limits and Future Prospects”, Andrea Cimatti (2009), In “Science with the VLT in the ELT era”

“Although this is very challenging from the observational point of view, 8m-class telescopes could still play a role before the advent of JWST and Extremely Large Telescopes (ELTs) if equipped with appropriate instrumentation. For instance, a multi-slit spectrograph with performances and sensitivity optimized in the zYJ spectral region (possibly extended to the H-band) would provide competitive results.”

Replace “VLT” -> “Subaru”, “ELT” -> “TMT”

One last thing…J-HSC

• Just to search for z>7 LAEs• HSC with NIR detectors for (Y)J

– Replace Hamamatsu CCDs to NIR chips• New dewer for J-HSC

– exchangeable to HSC (optical) dewer• No need to dense-pack the chips

– Series of NB filters + broad (Y)J– (hopefully) use only infrastructures for HSC

• corrector optics• NO optics cooling• Etc…

• Need spec. follow up? Use FOCAS-zYJ!

– Inspired by W-H Wang (ASIAA)

Summary• WFMOS --- great （すばらしい） . No doubt.• Want to continue/extend FOCAS high-z science? ---

WFMOS may not be the best instrument.– Right instrument for the right science （適材適所）

• Why not pursue more options?– Many ground-based astronomers in the world are actually p

ursuing their ways.– Could be niche, but could be revolutionary in near future.

• There might be another great ( すばるしい ) instrument to fit our other demands.– WFMOS for BAO and GA (+ alpha)– NEW faint spectrograph for high-z science (and other scien

ce)• BUT I AM NOT SURE if FOCAS-zYJ and/or HSC-J are すばるしい