First stars and

Near Infrared Extragalactic Background Light

Sapporo, March 1, 2005

T. Matsumoto (ISAS/JAXA)

1. Impact of WMAP 2. First stars (pop.III) ?3. Near Infrared Extragalactic Light(NIR EBL)4. Future observations

　 Recent topics on Cosmology　 WMAP(Wilkinson Microwave Anisotropy Probe）

Launched on June, 2001Orbit 　 S-E L2

Frequency 　 23,33,41,61,94 　 GHzPolarization can be observedAngular resolution 　 0.2 degree

（ cf. COBE:7 degree ）

First data was opened on Feb.2003

Fluctuation of CMB observed by WMAP

Consistent with COBEFiner structure is detected

Power spectrum of CMB fluctuation

Positions, heights of peaks providecosmological parameters

Geometry of the UniverseLife of the UniverseBaryon, dark matter, dark energyHubble constant

Douspis et al.

~0.17 +/- 0.04z_rei ~ 20 +/- 8

-----------

Summary of WMAP resultssuggesting inflation universe

● 　 Flat universe 　　 Ω=1.04 ± 0.04

● 　 Life of the Universe 134±3 108 yr

● 　 Baryon density Ωm=0.046 ± 0..02

● 　 Dark matter density Ωdm=0.23 ± 0.04

● 　 Hubble constant 　 h=0.72 ± 0.05

● 　 Dark energy 　 ΩΛ=0.71 ± 0.07

● 　 Optical depth for CMB τ=0.17 ± 0.04　　 Constraint on the re-ionization epoch: z 〜 17 　　

Gunn-Peterson troughs -> Absorption by neutral Hydrogen

Reionization of the Universe

)/(10GP

5~ HHI nn

From Gunn-Peterson troughs in Sloan quasars: 1. Small neutral fractions at z ~ 6 (1% neutral) 2. Sharp transition at z~6 (end of reionization?)

Fan et al. 2001

Reionization epoch is earlier than previously thought

What caused reionization?

Super novae

AGNmini black holes

First stars (Pop.III stars) Integrated light of first stars can be observed

as near infrared background!

First stars (pop.III stars)?

After the recombination era, universe was neutralizedNo metal, H and He onlyCooling through hydrogen molecules

⇨　 massive star formation

Luminosity (Eddington limit):4G mc2 M/T ~1.3x1038 M/M○ 　 erg/sec

Temperature T~104.8-5 K

Life timetL~Mc2/L~3x106 yr (~0.007)

Final stage of the evolution M< 40M○ type II super nova 40M○<M< 130M○ black hole 130M○ <M<260M○ pair instability super nova M>260M○ black hole

Can we detect the signature of first stars directly?

A 300 M○

first star at z~15,K-band mag 33(unlikey to be detectable)

First proto-galaxiescan contain as many as 105 stars.(Still not detectable)

(Scherrer 2002; Bromm et al. 2002; Santos et al. 2001)

Interesting wavelength range is 1 to 3 microns!!

Infrared Extragalactic Background Light (IREBL) Cosmic Infrared Background (CIB)

integrated light of distant galaxies and stars

UV and optical radiation can be observed at nearInfrared wavelengths due to redshift

A key observation to delineate the dark age of the Universe

Complementary to galaxy deep survey

Space observation is inevitable!Several rocket flightsCOBE/DIRBEIRTS/NIRS

COBE(COsmic Background Explorer)

• FIRAS

• DMR

• DIRBE(Diffuse Infrared Background Experiment) Absolute photometry of the sky brightness at 1.25, 2.2, 3.5, 4.9, 12, 25, 60, 100, 140, 240 m beam size ~0.7 degree

COBE was launched on 1989 and attained all sky survey.

As for the CIB,COBR team reported detections at far infrared bands

upper limits for other bands

Several authors obtained significant detections at J, K, L bands using COBE data

IRTS(Infrared Telescope in Space)

NIRS(Near Infrared Spectrometer)One of 4 focal plane instruments of IRTS

wavelength coverage 1.4-4.0 m spectral resolution 0.13 mbeam size 8 arcmin. x 8 arcmin.

Compared with COBE/DIRBEsmaller beam capability of the spectroscopysmaller spatial coverage ~7% of the sky

One of mission instruments of small space platform, SFU

launched on March 15, 1995

15cm cold telescope Optimized for diffuse Extended sources Mission life ~ 1 month

Near Infrared Sky

Foreground emission sources

• zodiacal light scattered sunlight by interplanetary dust (IPD)

• zodiacal emission thermal emission from IPD >3.5m

• Milky Way, integrated star light・ It is important to resolve and remove as 　 faint stars as possible.・ Smaller beam is better to avoid confusion

IRTS/NIRS: 8 arcminCOBE/DIRBE: 0.7 degree

Subtraction of foreground emissionIs a critical issue to detect EBL

IRTS observations

7% of the sky was surveyed during IRTS observation period (4 weeks)The data for 5 days before liq. He ran out were used to avoid contaminationThe data at high galactic latitudes are sampled 40<b<58 degree, 10<<70 degree

spectra of 1010 blank skies where no stars are detectedeffective beam size is 8’x20’ due to scanning effect

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Integrated light of faint stars

Constructed logN/logS model based on the NIRS observation (M.Cohen)

Obtained magnitudes of stars that correspond to the noises→ cut off magnitudes for all wavelength bands cf. 10.4 mag. at 2.24 m

Calculated integrated light of stars fainter than cut off magnitudesfor b=42, b=45, b=48 and applied cosec(b) law

The result is consistent with 2MASSFor the H and K bands

10

15

20

25

30

35

40

45

50

1.3 1.35 1.4 1.45 1.5 1.55

cosec(b)

2MASS(H) and model(1.63 )m

2 (MASS K) (and model2.14 )m

Zodiacal light and emission

Apply physical model by Kelsall et al. (ApJ, 508, 44 1998) to NIRS bands.

Model is based on the annual variationof the zodiacal light observed by DIRBE/COBE.

Calculate the brightness of zodiacal light/emission for all NIRS bands andobserved points.

After subtracting the star light and zodiacal light/emission

Significant isotropic emission was detected for all bands !

-100

0

100

200

300

400

500

600

700

10 20 30 40 50 60 70 80

Ch22,1,63m

, ( )ecliptic latitude degree

_ - _observed sky star light

zodiacal light

residual emission

Residual emission shows no dependence on the galactic plane

Breakdown to emission components

10-8

10-7

10-6

2 3 4

Wavelength ( )m

Observed sky brightness at high ecliptic latitude

Zodiacal light/emission

Isotropic emission ~20 % of dark sky

Integrated light of faint stars

COBE/DIRBE and star countsComparison with other observation

J-band K-band L-band

Dwek & Arendt (1998) 9.9 ±2.9

Gorjian et al. (2000) 22.4±6 11.0 ±3.3 30.7±6 15.4 ±3.3

Wright and Reese (2000) 23.1±5.9 16.8 ± 3.2　　　 　　 　　 31.4±5.9

Wright (2001) 28.9 ±16.3 20.2±6.3 61.9 ±16.3 28.5 ±6.3

Cambresy 　 　　　　 54 ±16 27 ±6.7

IRTS/NIRS 　　　　　　　　　　　　　　　　　　 　 27±5　　　　　　　　　　　　　　　　　　　　　　　 　（ 2.24 m)

In unit of nW.m-2.sr-1 Red numbers are based on "very strong no-zodi principle" (VSNZP)All observations are consistent if same zodi model is used!

Spectrum of the observed isotropic emission

Stellar like spectrum was found.

Main error is uncertainty of the zodiacal light model

Consistent with COBE/DIRBE

Significantly brighter than theintegrated light of galaxies !

Spectral gap around 1m

In-band energy flux is ~ 35 nW.m-2.sr-1

10

100

0.2 0.4 0.6 0.8 1 3 5

IRTS/NIRS

Model by Totani et al. 2001

Totani et al. 2001

Bernstein et al. 2002

COBE/DIRBE

Wright and Reese 2000, Kelsall model Fazio et al. 2004

Madau and Pozettti 2000

Cambrecy 2001

Wavelength ( )m

Spectrum of excess emission over ILG can be explained well

by integrated light of first stars!Sarvaterra and Ferrara (MN 339, 973 (2003) zend~8.8, redshifted Ly J band f★=10 〜 50 ％ massive star formation -> produced metals were confined in black holesz=17 2.2x108 yrz=8.8 5.5x108 yr

10

100

0.5 0.6 0.7 0.8 0.9 1 2 3 4

Model by Salvaterra and Ferrara

NIRS/IRTS Cambresy et al. 2001

Wright and Reese 2000

Bernstein et al. 2002

Wavelength ( )m

Another evidence of NIR EBL

Inverse process of pair anihiration

~TeV) + ~eV -> e+ + e-

when E>(mc2)1/2

Cross section is maximized when the soft phton energy is

e~2(mc2)2/E=0.5(1 TeV/E) eV ~2m

Absorption of TeV- blazer!

BL Lac object H1426+428z=0.129 ■ CAT(1998-2000) ▲ Whipple(2001) ● HEGRA(2002) ○ HEGRA(2002)

lines:model byMapelli and Ferrara

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Fluctuation of the sky -1rms fluctuation

Stellar fluctuation is estimated by using the model, but consistent with 2MASS

Fluctuation of zodiacal emission at 12m is less than 1% (IRAS, COBE, ISO)!⇨ Zodiacal light can not explain observed sky fluctuation!

1

10

2 3 4

2MASS stars

b>47, observed_fluc

Read out noisephoton noise

SL_nominal

Wavelength ( )m

Fluctuation of the sky -2Correlation between wavelength bands

-4 10-8

-3 10-8

-2 10-8

-1 10-8

0

1 10-8

2 10-8

3 10-8

4 10-8

-6 10-8 -4 10-8 -2 10-8 0 2 10-8 4 10-8 6 10-8

y = 4.5368e-12 + 0.51344x R= 0.74258

Surface brightness at 2.24

( .m W m

-2.sr

-1)

1.83 Surface brightness at ( .m W m-2 .sr

-1 )

Clear correlation between wavelength bands was detected.Spectrum (color) of fluctuation component is similar to that of isotropic emission

⇨ Isotropic emission is spatially fluctuating

Spectrum of fluctuation

⇨ Excess emission is fluctuating keeping the similar spectrum!

Observed rms fluctuation: ~5% of the sky brightness, ~6% of the zodiacal light, ~20% of the isotropic emission

Nearest pop.III stars (z~8.8) are responsible for the fluctuation!1

10

1

10

2 3 4

Wavelength (

Excess skyfluctuation

Excess emission over ILG

color of flutuatingcomponent

DIRBE/COBE

What causes NIREBL fluctuation?

1. Stellar fluctuation? Model is fairly consistent with 2MASS data!

2. Zodiacal light and/or emission?IRAS, COBE, ISO

3. Faint galaxies?

4. Pop.III stars?

Zodiacal emission is very isotropic!

10-7

10-6

10-5

1 10

Wavelength ( )m

NIRS

MIRS

280Kblackbody

solar spectrum

Spectrum of the zodiacal light and emission (<10 )degree

IRAS: 0.5 degree beam at 15 and 25 mCOBE: 0.7 degree beam at 12, 25 and 60 m

Residual from smooth distribution is less than 1% of peak brightness!

ISO: 3’x3’ pixel, 45’x45’ frame5 fields at different were observed at 25 m

rms fluctuation in one field is ± 0.2% !

Observed fluctuation is 6% of ZLIt is unlikely there exists big difference between scattering and emission

Observations (DIRBE, IRTS/NIRS and NITE) and theory (Cooray et al. 2004)

z-dependence of the model brightness(Salvaterra and Ferrara 2004)

1

10

100

2 3 4

model brightness9<z<1010<z<1111<z<1212<z<1313<z<14

Wavelength ( )m

Can pop.III explain observedFluctuation?

2-point correlation function

Correlation amplitude,

, Angular distanceθ [ ]degree

-20-100102030 IRTS / NIRS

-20-100102030 2MASS

-20-100102030

0 2 4 6 8 10

Random simulation

40

45

50

55

60

60 80 100 120 140 160 180 200

l (galactic longitude, degre)

Å™

Observed sky

Analysis is made for wide band brightness (integrated brightness for 1.43-2.14m)Read out noise is negligibleFluctuation is celestial origin

Data points lie along the belt↓

One dimensional analysis

Power spectrum

1

10

100

0.1 1

IRTS / NIRS2MASSRandom simulation1 upper limit

Angular frequency, q [1/deg]

Specific feature at 1 〜 2 deg.

This scale is,

20 Mpc at z=8.8200 Mps at present

First peak of CMB (l~220, 0.8 deg) corresponds to1.45 deg. at z~8.8

Power spectrum

for subsections

1

10

0.1 1

A (l < 134)

B (l > 134)

Spatial frequency, q [1/deg]

Expected fluctuation and detection capability of IRC/ASTRO-F(Cooray et al. 2004, Ap.J, 606, 611)

⌒Theory:Based on the fluctuation of dark matter.

Observation:Much larger fluctuationSharp peak at 2 deg.

Radiation of pop.III stars do not follow dark matter?

Underlying fluctuation may exists.

Future observations:Subtraction of foreground galaxies is essentail.ASTRO-F is powerful

Theoretical estimation of fluctuation

Kashlinsky et al. 2004

Future observationsIssues to be observed

• Spectral shape Confirmation of the spectral gap at ~1m real? Other spectral features?

• Fluctuation Spatial correlation over the wide range of angular scale Confirmation of 2 degree feature in 2 dimensional imageObserve underlying large scale structure

• Absolute measurements Observation free from ambiguity of the model ZL

ASTRO-F: image at K and L

CIBER (Rocket experiment): spectral observation, image at I and H

Out of zodiacal cloud mission: zodi free observation

10

100

0.2 0.4 0.6 0.8 1 3 5

Wavelength ( )m

1

10

2 3 4

2MASS starsb>47, observed_flucRead out noisePhoton noiseStar light, model

Wavelength ( )m

1

10

100

0.1 1

IRTS / NIRS2MASSRandom simulation1 upper limit

Angular frequency, q [1/deg]

ASTRO-F Formation and evolution of galaxies, stars, and

planets

First dedicated infrared mission of ISAS 70cm cooled infrared telescope Advanced Infrared Survey 50 times higher sensitivity, 10 times better spatial resolution, has longer wavelength band,

than IRAS Instruments IRC(Infrared Camera)

512x412 InSb array camera, 1.5”/pixel band imaging: K, L, and M bands low resolution spectroscopy: R-30 slit 2x50 pixel, R-15 4x50 pixel256x256 SiAs array

FIS(Far Infrared Surveyor)Launch target : January, 2006Orbit : sun synchronous orbit, 750km altitudeMission life: ~1.5 year (liq. He holding time) + 2 years (dedicated to NIR Observations)

Observation of NIREBL with ASTRO-F

Advantages of IRC/ASTRO-F observation

• Point-source rejection by high-resolution imaging observation Limiting magnitude at the K band is ~20 mag. for one pointing observation (~10 min.)　 This corresponds to ~30 nW m-2 sr-1 for 1 pixel (5) Almost all galactic stars and faint galaxies can be identified

• Discrimination of the fluctuation of the zodiacal light Observation of the same field at the different time epoch

• Spitzer does not have K band

Observation plans

1. Detection of the NIREBLfluctuation over the wide range of angular scale Wide area survey towards north ecliptic pole (NEP) is being proposed. Coordination with galaxy deep survey group

2. Detailed study of the spectrum of IREBL Low resolution spectroscopy at different ecliptic latitudes (2~5m) Spectrum without contamination of stars and galaxies can be obtained

“NEP-Deep & Wide” : SummaryNEP-Deep Field, 50 pointing/FOV 0.5 deg2

2.8 deg

NEP-Wide Field, 4 pointing/ FOV

Area: 2.8 deg2

N2 N3 or N4

2 2

S7 S11

2 2

L15 L24

2 2

Revised on 28th Oct. 2004

ASTRO-F detection limit

Wide(1pixel) 5

Deep(1pixel) 5

Wide(100pixels) 5

• IRC imaging observations at NEP are enough sensitive to detect the CNIRB fluctuation seen by IRTS• Spectroscopic measurement of the CNIRB mean level avoiding the contamination by normal galaxies

Spectroscopy (100pixels x 10sky) 5

K >20mag Integrated flux of galaxies

Expected fluctuation and detection capability of IRC/ASTRO-F

(Cooray et al., submitted to Ap.J.)

CIBER: Cosmic Background Explorer

ObjectivesSounding rocket observations at the wavelengths below the K band!NASA’s Black Brandt rocket

1. Spectrometer: Confirmation of spectral gap at ~1m low resolution spectroscopy, 0.8m<<2.0m

2. Imager: Observation of sky fluctuations at the I and H bands 2-dimension analysis

10

100

0.2 0.4 0.6 0.8 1 3 5

Wavelength ( )m

1

10

100

0.1 1

IRTS / NIRS2MASSRandom simulation1 upper limit

Angular frequency, q [1/deg]

Instrumentation of CIBER

Spectrometer7.3 cm dia. Telescope1 arcmin./pixel, 4 degree frame low resolution spectroscopy

0.8-2.0m, R~10

Imager15 cm dia. Telescope x210 arcsec/pixel, 2.8 degree frame I and H

Optical design of the spectrometer

Optics 13 lenses & 1 prism

linear dispersion

multiple slits (4 apertures)

Aperture 73.3 mmφ-F number /2F

FOV 4 4x degrees

Pixel FOV 1 1x arcmin

Slit size 1 256x arcmin

Wavelength = 0.85~2.00 m

Spectral resolution /Δ = 21~23 Optical efficiency 0.8

Focal plane array 256 256 x HgCdTe

Operating temperature 77 K

Quantum efficiency 0.5 Dark current < 0.1 -/e s

( )Readout noise CDS 10 -e

( )Photo current dark sky 10~20 -/e s

(Photon noise=15 )s 12~17 -e

(15 , 3Limiting mag s) = 15.0J

Imager Optics

Aperture 15 cm

Pixel size 10 arcsec

FOV 2.8 x 2.8 degrees

0 .95 ( )I 1 .6 ( )H m

Δ/ 0 .5 0 .5

Optical

efficiency

0 .3 0 .5

Photo

current

23 32 -/e s

Dark current < 0 .03 < 0 .03 -/e s

RN (CD )S < 10 < 10 -e

νIν (sky) 800 390 nW m-2 sr-1

δνIν in .st 18/p ix (1 ) 7/p ix (1 ) nW m-2 sr-1

δνIν conf. 8/p ix (1 ) 5/p ix (1) nW m-2 sr-1

δνIν total 20/p ix (1 ) 9/p ix (1 ) nW m-2 sr-1

galaxy cut 1 3e

0 .8 %

6 3e

5 %

# / sq degree

pixe l loss

δFν total 140 (5)

18 .0 (5)

120 (5)

17 .5 (5)

J y

Mag

Detection limit of the spectrometer

1

10

100

0.5 0.6 0.7 0.8 0.9 1 2 3 4

Wavelength [ ]m

1 , 15 , 1pixel s

HST

IREB brightness

ZL

ZE

1σ fluctuation

4 x 4 pixels, 50s, 1σ

400 pixels, 15s, 1σ

Simulated spectrum of the sky

0 100

2 102

4 102

6 102

8 102

1 103

1.2 103

1.4 103

0.8 1 1.2 1.4 1.6 1.8 2

EBL fit

ZL(10)+EBL

ZL(90)+EBL

IRTS

HST

Wavelength [um]

=10

=90

Expected performance of the imager

Spatial power spectrum of Pop III fluctuations (red curves), local galaxy fluctuations (correlations term light blue curves, shot term dashed curves) for 3 different cutoff magnitudes, and the total signal (solid blue curves). The 18.5 mag cutoff is for the rejection level from the NAME images alone; the faintest cutoff (I = 25.5 and H = 21) comes from ground-based measurements overlapping our images. The data points show the errors from NAME in a 100 s observation, including both instrument noise and sample variance. We assume there are no Pop III fluctuations detectable at I-band, following the IRB star spectrum in Fig. 3. NAME can easily detect the optimistic Pop III signal (this model produces a cumulative background of 25 nW m-2 sr-1, consistent with the missing amount in Figs. 1 and 3), clearly distinguished by its different power spectrum from local galaxies at H-band. NAME has sufficient sensitivity to detect the pessimistic Pop III signal (this model produces a background of 3 nW m -2 sr-1), although it is obscured by local galaxy fluctuations at a limiting magnitude of H = 21. Reducing the cut-off magnitude further is possible, and would allow us to positively extract even the signal of the pessimistic model.

Configuration of the telescope system

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Payload configuration

Observation plan

Fig. 17. Proposed sequence of observations superposed on the trajectory of the NITE payload. Separation from the rocket engine occurs at 85 s, followed by despin, opening of the vacuum shutter door at 95 s, and slewing the payload to the first science target. The instrument observes 5 science fields before closing the shutter door, reentry into the atmosphere, and recovery operations

Organization and scheduleOrganization

Japan: ISAS(Matsumoto, Matsuura, Wada, Matsuhara) Nagoya U. (Kawada, Watabe)

US: Caltech/JPL(J.Bock)UCSD (B.Keating)

Korea: KAO (S. Pak, D-H. Lee)

ScheduleJune, 2004 Proposal to NASA

Now approved!No-funded launch!

Spring, 2007 First launch at White SandsSpring, 2008 Second launch

Funding?

The life of an IR rocket (Jamie’s previous experiment)

Solar sail mission

Out of zodiacal cloud mission

● Free from ZL and IPD emission

● Accurate absolute measurement of E

BL

without IPD model ambiguity is possi

ble

● Observation of the mid-infrared

background is possible

Free from zodiacal light/emission

provides decisive result for the NIREBL!

Possible mission concept of out of zodiacal cloud mission!

Scientific objectives Accurate measurement of spectrum and fluctuation of IREBL

InstrumentationTelescope 5cm dia. lens systemWavelength range 0.8-2.2mPixel FOV ~10’Detector HgCdTeCooling system radiation coolingWeight 3 kg

Summary

1. CMB polarization observed by WMAP indicates that the Universe was reionized at z~17 by the first massive stars (pop.III stars).

2. Independent observations by COBE and IRTS provide detections of significant near infrared extragalactic background light. Recent observations of Tev- Blazers support its cosmological origin.

3. The near infrared extragalactic background observed by IRTS and COBE could be consistent with pop.III star scenario.

4. Spectrum observed by IRTS suggests the redshift at the end of pop.III era is ~9.

5. Fluctuation of the sky was detected (~20% of EBL) by IRTS and COBE which is too large to be explained with the standard model.

6. Near infrared background is a unique tool to investigate the pop.III stars. ASTRO-F, CIBER(Rocket experiment) and Solar-Sail missions will provide valuable information on the pop.III era.

NIREBL is a unique tool to investigate the first stars!

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CMB

z=1,000 3x105 year

?Near infrared background

z~10 5x108 year

Cosmic Microwave Background(CMB)

Most distant observable object

The Universe ~4x105 years after big bangFossil photons

COBE(COsmic Background Explorer) CMB Map(launched on 1989 by NASA)

CMB is very uniform

But

Fluctuation of ~10-5 is detected 　 　⇨

Present Universe Extremely non uniform!Large scale structure, Cluster of galaxies, galaxies, starsplanets, -------

Evolution from uniform and isotropic Universe to extremely non uniform Universe?How first stars and galaxies formed?

Evolution of the Universe

Dark age of the Universe

Prepared by N. Fujishiro

Proposed Survey Field

IRC background measurements around NEP

Spectral resolution

/

Survey area [sq.degree]

Exposure time per frame

[# of pointings]

Single pixel detection limit (5) *

[nW/m2/sr]

Number of galaxies per camera frame**

Number of dark pixels per frame ***

Ultra-Wide

(Phase-3)

3 100 TBD ~ 10

(pixel binning)

- -

Wide 3 2.8 2 (500 s) 10 - -

Deep 3 0.5 25 (1.4 hrs) 3 3000 >10^5

Ultra-Deep 3 - - - - -

* in unit of surface brightness (I

** FOV of the IRC camera frame is 10’x10’*** number of pixels available for the background analysis = total number of pixels – (confusion factor) x (number of galaxies)

= 1.7x10^5 – (3pics x 3pics) x (number of galaxies)

Spectral resolution /

Survey area Exposure time Detection limit (5)

[nW/m2/sr]

Number of galaxies

Number of dark pixels

Spectroscopy 30

( 2 – 5 m)

3” x 73”

x 100 directions

(various b and )

1 pointing (500 s)

x 100 directions

30 (pixel binning)

~10 (10 sky average)

2 90

1. Wide-band deep imaging in K, L and / or M bands

2. Spectroscopy

0.9

1

1.1

1.2

1.3

1.4

1 1.5 2 2.5 3 3.5 4 4.5

Wavelength (

Lensed galaxy at z~10?

Pello et al. 2004, A&A 416, L35-L40.

SED and spectrum

IRC SURVEY STRATEGIESIRC SURVEY STRATEGIES

0.02 1 10100

1000 ?

Area (sq. deg.)

Num

ber o

f Poi

ntin

gs

100

10

1

Depth and Area

Theory to Reality: Near-IR wide-field surveys

5-sigmapoint sourcedetection(planned)

(experiments at this end are preferred)

IRC background measurements around NEP

1. Wide-band deep imaging in K, L and M bands

* in unit of surface brightness (I

** FOV of the IRC camera frame is 10’x10’*** number of pixels available for the background analysis = total number of pixels – (confusion factor) x (number of galaxies)

= 1.7x10^5 – (3pics x 3pics) x (number of galaxies)

Spectral resolution /

Survey area Exposure time Detection limit (5)

[nW/cm2/sr]

Number of galaxies

Number of dark pixels

Spectroscopy 30

( 2.0 – 5 m)

3” x 73”

x 100 directions

(various b and )

1 pointing (500 s)

x 100 directions

30 (pixel binning)

~10 (10 sky average)

2 90

2. Spectroscopy

Spectral resolution

/

Survey area [sq.degree]

Exposure time per frame

[# of pointings]

Single pixel detection limit (5) *

[nW/cm2/sr]

Number of galaxies per camera frame**

Number of dark pixels per frame ***

Wide-field Shallow（ phase-3)

3 100 1 (500 s) 30 2x10^3 >1.5x10^5

Shallow (Phase-1,2) 3 10 1 (500 s) 30 2x10^3 >1.5x10^5

Deep (Phase1,-2) 3 1 10 (1.4 hrs) 10 (3-4)x10^3 >1.3x10^5

Ultra Deep

(Phase-1, 2)

3 0.02 100 (14 hrs) 3 (0.5-1)x10^4 >8x10^4

Fluctuation of the sky-4Detection of fluctuation with 2MASS dataKashlinsky et al. ApJ 279, L53 (2002), Odenwald et al. ApJ 283, 535 (2003)

Interpretation of the 2MASS fluctuation with pop.III stars

Theoretical estimation of fluctuation I.Magliocchetti, Salvaterra and Ferrara MN, 342, L25 (20

03)

Sharp drop at ~200 arcsec 8.6 Mpc at zend=8.8

Fluctuation is dominant at the J band