20 mars 2006visions en astronomie infrarouge instrumental prospects in infrared and submillimeter...

20 Mars 2006 Visions en Astronomie Infrarouge

INSTRUMENTAL PROSPECTS IN INFRARED AND SUBMILLIMETER ASTRONOMY

Jean-Loup Puget Institut d'Astrophysique Spatiale, Université Paris Sud,

Orsay


Specificities of thermal infrared astronomy

• the earth atmosphere is opaque from 13 µm to 350 µm (and still mostly opaque up 800 µm)

• thermal emission of the atmosphere and of the telescope is a severe limitation to sensitivity increasing very steeply beyond 2 µm

• in the range 10 µm to 1mm the diffraction limit is from 20 to 2000 times what it is in the V band: CONFUSION limits the sensitivity

• detector array technology progress have been slower than in the optical and near infrared (although major progress were made on individual detectors and related technology like cryogenic systems)


how to overcome these limitations• observing from space allow your telescope:

– to be above the atmosphere– to be cooled

• uses large telescopes and interferometers• near and thermal IR adaptive optics and

interferometry• on the long wavelengths side

– in atmospheric windows– in very high altitude sites (JCMT, CSO, IRAM,

ALMA)

• the far infrared remains the most difficult; space interferomers still require a lot of developments and will not be available before a long time

20 Mars 2006 Visions en Astronomie Infrarouge(D. Scott)

Cosmic background from radio to gamma rays

CMB

CIB


The HDF seen by ISO (7 and 15 m)

ISOCAM team

Orange: 15 mGreen: 7 m


Fast progress in mid IR detectors and cryogenic telescopes: SPITZER

• the Si-As BIB arrays used in MIPS allow to get– deep surveys comparable to optical ones– spectra of galaxies at redshifts beyond 3 with an 85

cm telescope !

• very efficient He cryostat in space have been built through very efficient passive cooling

• large telescopes (2 to 3.5 m) for Herschel-Planck can be cooled down below 50 K also with passive cooling


Typical galaxy spectrum


Source Counts

Lagache, Dole, Puget, 2003, MNRAS


z < 0.3

z < 2

z < 1.3

z < 1

z < 0.8

Predictions for Redshifts

Lagache, Dole, Puget et al, 2004, ApJS, 154

For S24 < 0.2 mJy: ~30% of z > 2 galaxies

bimodal contribution:

• 0.3 < z < 1 (11 to 13 µm features) peaks at 0.5 mJy

•1.6 < z < 2.5 (6 to 9 µm features) peaks at 0.2 mJy

•min contribution 1.1 < z < 1.6


PAH at z~2

Normalized Redshift Distribution in GOODS CDFS :

-Ks sample of ~3000 sources (black)

-MIPS 24um sample (red), identified at 94% in Ks: ~730 sources:

-36% spectroscopic-21% COMBO-17-43% photo-z

-~30% of Spitzer sources are at z>1.5

8.6 m PAH Redshiftedat z~2 and Observed at

24 m !

K. Caputi et al., 2005b, submitted

20 Mars 2006 Visions en Astronomie Infrarouge Lutz et al, 2005, ApJ

PAHs at z~2.8

-2 Submm Galaxies at z~2.8 observed w/ IRS -~2hrs of integration-6.2 & 7.7 (& 8.6) PAHs-Luminosities: 1.3 to 2 1013Lo-SFR>2000Mo/yr

6.2@23

7.7@29

M82+linear AGN continuum

8.6@33


ISO 170 m surveys

The FIRBACK survey


Confusion

• two types: if you detect sources S>Smin • keep the probability to have not separable sources

directly linked to N(S>Smin)

• keep good signal to noise in you beam due to fluctuations of the weaker sources

• the far infrared and submillimeter is a special case: the second criteria is often coming from sources much weaker than Smin


•Deep cosmological surveys reveal 8 104 in K band (K<21.5)

•MIPS-24µm reveal about 2 104 galaxies per sq deg

•10 per Herschel beam at 550 µm

•250 gal per PLANCK beam !

Stacking 24 µm sources in long wavelengths maps

•possible if you have excellent/stable pointing and effective PSF

•limited by number of sources and clustering of sources (cannot do stacking when your angular resolution gets smaller than the correlation scale of the source population you study)


Stacking Analysis 160Not physicallyrelevant but illustrative:

80<S24<83Jy

330 sourcesCDFS

[z>1.5 ?]

Dole, Lagache, Puget, 2005, astro-ph/0503017


beat the confusion: future steps in the stacking game

• if you can get photometric redshifts for your mid infrared sources such that– galaxies in a redshift and mid IR flux band (typically dz/z~10-

20%) have a long wavelength distribution symetrical with respect to the mean you get from stacking

– a large enough number of sources per long wavelength beam such that statistical fluctuations are getting small enough

• you can then remove these galaxies from the long wavelength maps and be left with a CIB containing only the structures associated with the redshift >2.5

• for example in a Planck map at 550 µm with 250 24 µm galaxies per beam, the error in the removal is the dispersion of the colors divided by about 15


Instrumentation: other coming steps • at millimeter and submillimeter wavelengths

detectors close to quantum limits are being built – for Herschel

– Planck

• arrays in the far infrared are still being developped– Si detectors are very successful up to 35 µm

– Ge photoconductors have met many problems

– bolometer arrays will fly on Herschel-PACS

– arrays of TES (transition edge supra-conductor detectors) multiplexed, planar antenna detection


Polarization sensitive bolometersAndrew Lange, Jamie Bock,Caltech-JPL


Performances

JPL data 143 217 353 545 857 P100 P143 P217 P353

# in focal plane

4 4 4 4 4 8 8 8 8

req ms 6,3 4,4 4,4 4,4 4,4 8,4 6,3 4,4 4,4

average ms 5,2 2,5 2,3 1,2 1,9 10,3 4,5 3,2 4,2

Avg dark NEP

aW/rt Hz

11,3 13,6 11,4 29,8 30,4 9,1 10,3 14,0 12,6

NEP/BLIP 0,81 0,80 0,54 0,48 0,21 0,99 1,03 1,27 0,84

NET goal K rt s 60 92 280 13,4 8,7 102 83 134 404

Avg NET K rt s 45 70 228 8,4 5,3 82 68 111 470

(min,max) 43 50 67 751

95

258

8,0 9,4 5,0 5,8 6910

062 76 99

123

402

568

UWC data

xpol resp. 3,52% 5,96% 2,21% 5,48%

(min,max) 1,9%

5,2%

3,6%

8,9%

2,5%

3,4%

4,2%

7,0%

optical eff. 35% 32% 26% 29% 19% 32% 40% 34% 23%

(min,max) 35

%36

%31

%33%

24%

28%

27%

30%

16%

21%

25%

37%

34%

44%

31%

36%

21%

24%

Planck bolometers performances:

dark NEP below the photon noise at mm wavelengths


Stabilisation PID2 N - thermometer PID2 N

8 nK Hz-1/2

(+0.014)

30

space qualified dilution cooler (Alain Benoit CRTBT)


integrating sphere

CS2

CS1

mirror

polariser + crosstalk sourceson rocker

HFI CQM


CMB spectra: temperature, E and B polarization3 observables : T, E,

B

B polarization power spectrum is

5 orders of magnitude weaker

than T for tensor/scalar

=0.1 !

E > 0

E < 0

B > 0B < 0

WMAP

PLANCK

dedicated polarization mission


• Observatories– ISOCAM 15 µm 6 arc sec (32*32 array)– ISOPHOT 160 µm 90 arc sec (4 individual pixels)– SPITZER-MIPS

• 24 µm 5.6 arcsec (128*128 array)• 160 µm (2*20 array)

– JCMT-SCUBA 850 µm – IRAM PdB – HERSCHEL 550 µm

• All sky Surveys– IRAS 1.5 arcmin/0.5 Jy at 100 µm, 30 arcsec/0.5Jy at 12 µm – COBE 40 arc minutes – ASTRO-F – PLANCK 550 µm, 5 arc minutes


redshift ranges contributing to the CIB

Wavelength (µm) z 50% z 20% - z 80%

15 0.8 0.5 – 1.5

70 0.8 0.5 – 1.6

24 1.4 0.6 – 2.2

160 1.35 0.6 – 2.3

350 2 0.9 – 3

850 2.8 1.8 – 4

2000 3.5 2 – 5.5


CIB SED

Lagache, Dole, Puget, 2003, MNRASlong wavelengths emissivity 1.5 to 2


PAHs at z~1.8 to 2.6

Yan et al, 2005, ApJ in press

-8 24 m galaxies targetted w/ IRS (52 total)

-6 MIR features detections: 1.8 < z < 2.6

-6.2 & 7.7, 8.6, 11.3 PAHs (+Si abs)

-Luminosities: 0.6 to 4 1013Lo


Cosmic Infrared Background• 24 m

– Down to 60 Jy– 75% resolved– By integration of the source counts, CIB@24 is

2.7 +1.1-0.7 nWm-2sr-1

• 70 m– Down to 15 mJy– ~23% resolved

• 160 m– Down to 45 mJy– ~7% resolved

• References– Papovich et al., 2004– Dole et al., 2004

20 Mars 2006 Visions en Astronomie InfrarougePapovich, Dole et al, 2004, ApJS

24 m

Differential Source Counts

Dole et al, 2004a, ApJS


Planck planned capabilities


One year mission CMB performances

100 143 217 353 545 857

beam sizearcmi

n 9,5 7,1 5 5 5 5

n pixels 1,65E+06 2,95E+06 5,94E+06 5,94E+06 5,94E+06 5,94E+06

system sensitivity to T

K rt s 28,8 16,4 26,1 93,9 4,2 2,6

system sensitivity to Q,U

K rt s 43,8 38,1 58,9 262

avg time/pixel s 19,2 10,7 5,3 5,3 5,3 5,3

T/pixel K 6,6 5,0 11 40 273 11987

T/T/pixel 10-6 2,4 1,9 4,2 15,0 101 4423

T/T/pixel bluebook 10-6 2,5 2,2 4,8 14,7 147 6700

(Q,U)/pixel K 10,0 11,6 25,6 114

(Q,U)/T/pixel 10-6 3,7 4,3 9,4 41,9

(Q,U)/T/pixel bluebook 10-6 4 4,2 9,8 29,8


Comparison CIB in optical/IR

• Energy in the extragalactic background : < 6 m: 2 4.2 10 -8 W m-2 sr-1

> 6 m: 4 - 5.2 10 -8 W m-2 sr-1

=> E(Far-IR) / E(opt) ~1 – 1.25• Local Universe:

– E(Far-IR) / E(opt) = 0.4 !!!• Conclusion:

– Strong increase of the IR ouput energy with z• Questions:

– stars or massive black holes as the main energy source– role of IR galaxies in the building of galaxies as we see them today– does the emerging picture fits or not in the standard model of

hierarchical structure formation


Updated 2004 LDP Model

Lagache, Dole, Puget, et al, 2004, ApJS

7.5% 3%

20 mars 2006visions en astronomie infrarouge instrumental prospects in infrared and submillimeter...

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