SWIRE view on the "Passive Universe":

Studying the evolutionary mass function and clustering of galaxies

with the SIRTF Wide-Area IR Extragalactic Survey (SWIRE)

Formation of massive ellipticals, S0’s and galaxy spheroids

Formation of large disks

log ρ(>z)

- 100%

- 10%

The cumulative Stellar Mass Density vs. Star Formation Rate

- 1%

Photometric estimates of the stellar mass in high-z galaxies

t=9 Gyr7 Gyr

5 Gyr

1 Gyr

3 Gyr

z=1.27

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

Redshift distribution for E/S0 in the HDFs & NICMOS vs. predictions for different zF

Typical SEDs of morphologically-classified E/S0 galaxies

Model 1

Model 2

Franceschini et al. (1998)

Rest-frame colours for early-type galaxies compared with model SSPs

Passive Ellipticals

Dusty Starbursts

Sample of 45 ERO's selected K<19.2 over 52 sq.arcmin(Cimatti et al. 2001)

Moriondo et al. (2000): study of Extremely Red Objects selected in K

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"

Spatial clustering of EROs (high-z ellipticals and dusty starbursts)[Daddi et al. 2000, 2001]

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

The case of spiralsgalaxies

z-distributionsof Sp's in HDFN

Evolutionary rateof Star-Formation

Generation of stellar mass

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

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)

The SIRTF "SWIRE" Survey

SIRTF Wide-area IR Extragalactic Survey, Legacy Programme (Lonsdale et al.), ~ 70 sq. deg. at all SIRTF photometric bands

ISO-selected IR starburst in the HDFS, template for SIRTF sources

SWIRE/IRAC sensitivity limits

ESIS limits

M82

K=19.2M51

SWIRE sensitivity ˜ K=21 for moderately red galaxies

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]

Typical spectra

Photometric redshifts from purely the IRAC band fluxes

ISO-selected IR starburst in the HDFS, template for SIRTF sources

SWIRE/IRAC sensitivity limits

ESIS limits

M82

K=19.2M51

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

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