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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)
Formation of massive ellipticals,
S0’s and galaxy spheroids
Formation of large disks
- 100%
- 10%
log ρ(>z)
- 1%
The cumulative Stellar Mass Density vs. Star Formation Rate
z=1.27
1 Gyr
3 Gyr
5 Gyr
7 Gyr
t=9 Gyr
Photometric estimates of the stellar mass in high-z galaxies
MASSES of E/S0
galaxies in the HDFs
vs. 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 1
Continuous: Model 2
Salpeter IMF with
0.15<M<100 Mo
Redshift distribution for E/S0 in the HDFs & NICMOS
vs. predictions for different zF
Model 1
Typical SEDs of morphologicallyclassified E/S0 galaxies
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)
"Colors of
high-z cluster
galaxies"
Solid line: zF=5, dashed line: zF=2
Evidence for a different star-formation history in high-density
environments [accelerated with cosmic time wrt. the field]?
Spatial clustering of
EROs (high-z ellipticals
and dusty starbursts)
[Daddi et al. 2000, 2001]
z=1.27
z=2.5
IRAC will sample low-mass stellar populations in high-z gals
and measure baryonic mass to high-z (JHK become unreliable at z>1.5)
z-distributions
of Sp's in HDFN
Evolutionary rate
of Star-Formation
The case of spirals
galaxies
Generation of stellar mass
ISO 6.7 μ
Elliptical galaxy in the HDF North
Current situation about deep mid-IR surevys:
few tens of square arcmins sampled by ISO to the
relevant depths
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
M82
M51
K=19.2
SWIRE/IRAC
sensitivity limits
ESIS limits
ISO-selected IR starburst in the HDFS, template for SIRTF sources
SWIRE sensitivity ˜
K=21 for
moderately red galaxies
Modelling the expected
performances of SWIRE
in the IRAC bands
[model with zF=3]
Expected z-distributions
in a 10 sq.deg. area
sampled at the SWIRE
flux limit
Typical
spectra
Photometric
redshifts from
purely the IRAC
band fluxes
M82
M51
K=19.2
SWIRE/IRAC
sensitivity limits
ESIS limits
ISO-selected IR starburst in the HDFS, template for SIRTF sources
z=1.27
z=2.5
IRAC will sample low-mass stellar populations in high-z gals
and measure baryonic mass to high-z (JHK become unreliable at z>1.5)
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