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SWIRE view on the "Passive Universe":
Studying the evolutionary mass function and clustering of galaxies
with the SIRTF Wide-Area IR Extragalactic Survey (SWIRE)
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Formation of massive ellipticals, S0’s and galaxy spheroids
Formation of large disks
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log ρ(>z)
- 100%
- 10%
The cumulative Stellar Mass Density vs. Star Formation Rate
- 1%
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Photometric estimates of the stellar mass in high-z galaxies
t=9 Gyr7 Gyr
5 Gyr
1 Gyr
3 Gyr
z=1.27
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MASSES of E/S0galaxies in the HDFsvs. redshift
(Rodighiero, Franceschini & Fasano 2001)
Sample of 69 E/S0's to K=20.2 morphologically selected over 11 sq.arcmin in HDFN, HDFS & NICMOS
Dotted: Model 1Continuous: Model 2
Salpeter IMF with 0.15<M<100 Mo
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Redshift distribution for E/S0 in the HDFs & NICMOS vs. predictions for different zF
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Typical SEDs of morphologically-classified E/S0 galaxies
Model 1
Model 2
Franceschini et al. (1998)
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Rest-frame colours for early-type galaxies compared with model SSPs
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Passive Ellipticals
Dusty Starbursts
Sample of 45 ERO's selected K<19.2 over 52 sq.arcmin(Cimatti et al. 2001)
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Moriondo et al. (2000): study of Extremely Red Objects selected in K
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Stanford et al. (1998)
Evidence for a different star-formation history in high-density environments [accelerated with cosmic time wrt. the field]?
Solid line: zF=5, dashed line: zF=2
"Colors ofhigh-z cluster galaxies"
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Spatial clustering of EROs (high-z ellipticals and dusty starbursts)[Daddi et al. 2000, 2001]
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IRAC will sample low-mass stellar populations in high-z galsand measure baryonic mass to high-z (JHK become unreliable at z>1.5)
z=2.5
z=1.27
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The case of spiralsgalaxies
z-distributionsof Sp's in HDFN
Evolutionary rateof Star-Formation
Generation of stellar mass
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Current situation about deep mid-IR surevys: few tens of square arcmins sampled by ISO to the relevant depths
Elliptical galaxy in the HDF North
ISO 6.7 μ
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The case for SWIRE• SIRTF will offer a unique chance to sample a
largely unexplored waveband at 3 <λ<10 μm
• This will allow photometric measurements of the baryonic mass in stars for an enormous number of distant and high-z galaxies
• This is one of the main targets of our Legacy Program, SWIRE
• SWIRE will devote 500 hours to survey with IRAC a very large area (70 sq.deg.) to moderate depths (+ 400 hours with MIPS at longer-λ)
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The SIRTF "SWIRE" Survey
SIRTF Wide-area IR Extragalactic Survey, Legacy Programme (Lonsdale et al.), ~ 70 sq. deg. at all SIRTF photometric bands
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ISO-selected IR starburst in the HDFS, template for SIRTF sources
SWIRE/IRAC sensitivity limits
ESIS limits
M82
K=19.2M51
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SWIRE sensitivity ˜ K=21 for moderately red galaxies
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Expected z-distributions in a 10 sq.deg. area sampled at the SWIRE flux limit
Modelling the expected performances of SWIRE in the IRAC bands[model with zF=3]
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Typical spectra
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Photometric redshifts from purely the IRAC band fluxes
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ISO-selected IR starburst in the HDFS, template for SIRTF sources
SWIRE/IRAC sensitivity limits
ESIS limits
M82
K=19.2M51
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IRAC will sample low-mass stellar populations in high-z galsand measure baryonic mass to high-z (JHK become unreliable at z>1.5)
z=2.5
z=1.27
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CONCLUSIONS
• A dramatic step forward allowed by SWIRE in the investigation of both the "Active" and "Passive" Universe at high redshifts
• SWIRE will allow to match current sensitivity limits for the study of IR source populations (red type-II QSOs, starbursts, forming E/S0, passively evolving spheroids) on areas >100 times larger at λ's currently unaccessible