Transcript Slide 1

The Universe at Redshifts from 1 to 2
for Early-Type Galaxies
~ Unveiling “Build-up Era” with FMOS ~
Naoyuki Tamura
(University of Durham)
Outline
r To understand the histories of
early-type galaxies …
Does stellar population tell us all ?
r Galaxy population at z < 1 and z > 2
What are expected at 1 < z < 2 ?
r Extremely Red Objects
Limitation due to lack of spectrum
r Revisit the starting point :
How can the strengths of Subaru/FMOS
be exploited ?
r Summary
Stars in Elliptical Galaxies
r No active star formation is
on-going at z=0. The bulk
of stars seem to be old.
SFRNGC 3923 : E4
r Evolutions of CM relation
& Fundamental Plane up
to z ~ 1 look passive.
Star formation
stopped.
z>2?
Passive
evolution
t
Ages at z = 0 from spectroscopy
Trager et al. (2000)
Caldwell et al. (2003)
Cluster
Group
Field
Virgo
Field
100 200
s [km/s]
300
60
100
s [km/s]
180
What does “age” tell us ?
“Star formation history”
?
- when did most of the stellar content form ?
“Galaxy formation history”
- when did a galaxy become an elliptical ?
Monolithic Collapse Scenario
Starburst
Stellar Population
Gas rich
Luminosity
Function
Hierarchical Merging Scenario
Major merger
Luminosity Function of E/S0s at z < 1
COMBO-17
~ 2800 arcmin^2, R < 26 (5s), ~ 25000 galaxies
~ 5000 galaxies on the red
sequence at 0.2 < z < 1.2.
Most of them (~ 85 %) seem to
be morphologically early-type.
Evolution of
luminosity function
Rix et al. (2004)
GEMS
High resolution imaging
follow-up with ACS/HST
Luminosity Function of E/S0s at z < 1
COMBO-17
About half of the local
population were already
in place at z ~ 1 ?
Bell et al. (2003)
Luminosity Function of E/S0s at z < 1
Morphology
Im et al. (2002): DEEP Groth Strip survey
(HST/WFPC2 images)
Multi-band photometry
Chen et al. (2003): Las Campanas IR survey
Spectroscopy
Pozzetti et al. (2003): K20 survey
Suggest a mild evolution up to z ~ 1
50 ~ 80 % were already in place at z ~ 1 ?
Any “bona-fide” E/S0s at z > 2 ?
Radio galaxies
(z = 2.3)
(z = 2.4)
Rocca-Volmerange et al. (2004)
Pentericci et al. (2001)
Passive evolution prediction
12
(z f = 10, M = 10 M8)
Any “bona-fide” E/S0s at z > 2 ?
No clear Hubble sequence ?
A population of passive E/S0s have not revealed yet ?
Lyman Break Galaxies
z>3
SFR ~ 1 - 100 M8 /yr
Stellar mass ~ 1010 M 8
SCUBA Galaxies
<z> ~ 2.5 (1 < z < 4)
SFR ~ 1000 M 8/yr
Red galaxies from FIRES
J-K ~ 2 or redder
Strong clustering
z = 2 ~ 3 (?)
Starburst galaxies ?
Investigations
are on-going ...
How can they be linked at z = 1 ~ 2 ?
Star forming galaxies
Passive evolution phase
somehow
Consumption ? Environmental effect ?
Half or more of the local population
show up in this epoch ?
Through redshift survey …
Luminosity function of passive galaxies
and its evolution at z = 1 ~ 2
A number of post-starburst galaxies ?
Distant clusters are revealed ?
Extremely Red Objects (EROs)
R-K > 5 / I-K > 4
Good candidates for passive ellipticals at z > 1.
Luminosity function of EROs has been studied.
Our understandings of EROs have been
limited due to lack of spectra.
Heterogeneity
Although the colour criterion seems to work
for isolating passive ellipticals …
(Cimatti et al. 2003; Yan et al. 2004)
Colour criterion to classify EROs
Cimatti et al. (2003)
Smith et al. (2002)
Smail et al. (2002)
Mannucci et al. (2002)
Evolution of ERO LF at z > 1 ?
Miyazaki et al. (2002)
Caputi et al. (2004)
Extremely Red Objects (EROs)
R-K > 5 / I-K > 4
Good candidates for passive ellipticals at z > 1.
Luminosity function of EROs has been studied.
Our understandings of EROs have been
limited due to lack of spectra.
Heterogeneous
Although the colour criterion seems to work
for isolating passive ellipticals …
(Cimatti et al. 2003; Yan et al. 2004)
Photo-z : D z ~ 0.3 at z ~ 1.5
Too coarse to investigate evolution
at 1 < z < 2 ?
What we need to do are :
To perform deep spectroscopic
observations and to get quality data.
Absorption line
Redshift
Classification
To collect a large number of galaxies
at z > 1 from a large survey area.
Good statistics
Cosmic variance
The other word of FMOS (1)
Wide spectral coverage in the NIR
r Spectral features in the rest frame optical
are available for galaxies at z > 1.
r Optimal for redshift survey.
Combination with UKIDSS-DXS
(& Subaru/Suprime-Cam)
r Allows us to efficiently pick up candidates
for galaxies at z > 1 with colour information.
r Luminosity can be derived with the aid of
redshift.
The other word of FMOS (2)
Wide field & high multiplicity
FMOS-FOV / 400 fibres
30’
~ 200 fibres will be
available for objects
in one exposure.
Highly efficient !
Better statistics
Longer integration
Simulated Spectrum
Old stellar population (3.0 Gyr age) at z = 1.5
H = 20.5 mag
8 hr integration (1 hr x 8) & 5 pix. binning
Mgb
4000 A
Hb
G-band
Gemini Deep Deep Survey
Gemini Multi-Object Spectrograph
4 x 30 arcmin^2 field
Nod & shuffle technique
> 30 hr integration per field
???????????????? Survey
Fibre Multi-Object Spectrograph
FOV ~ 700 arcmin^2
200/200 fibres for object/sky
(+ Double beam switching obs. ?)
??? hr integration per FOV
Simulated Spectrum
Old stellar population (3.0 Gyr age) at z = 1.5
H = 22.0 mag
100 hr integration (1 hr x 100) & 5 pix. binning
Mgb
4000 A
Hb
G-band
NaD
Summary
To understand history of early-type galaxy
Luminosity Function
Bridging two epochs ?
z<1
Passive evolution
Stellar Population
2<z
Star forming galaxies
Luminosity function of passive galaxies
Evolution of LF between z = 1 and 2.
A number of post-starburst galaxies ?
Need to look at absorption lines
Wide field & high multiplicity can be
exploited for deep observation.