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Star Formation Rates, Ages and Masses of Massive Galaxies in the FORS Deep and GOODS South fields. R. Bender, A. Bauer, N. Drory, G. Feulner, A. Gabasch, U. Hopp, M. Pannella, R.P. Saglia, M. Salvato

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slide1

Star Formation Rates, Ages and Masses

of Massive Galaxies in the

FORS Deep and GOODS South fields

R. Bender, A. Bauer, N. Drory, G. Feulner, A. Gabasch, U. Hopp, M. Pannella, R.P. Saglia, M. Salvato

(Universitäts-Sternwarte München, Max-Planck Institut für Extraterrestrische Physik, University of Texas)

Map out galaxy assembly: Luminosity functions

Stellar mass functions, Star formation rates as a function of mass.

slide2

Star Formation Rates, Ages and Masses

of Massive Galaxies in the

FORS Deep and GOODS South fields

  • Study evolution of galaxies with broadband deep U to K surveys.
  • LFs, Mass Functions, SFRs do not require spectroscopy but can
  • be derived with accurate photometric redshifts.
  • Advantage of photo z: no color selection bias, fainter luminosities,
  • larger sample (~10000 galaxies in FDF and GOODS S sub-sample)
  • FORS Deep Field (IAB=26.8): 98% of all galaxies with dz/(1+z)<0.03;
  • GOODS S (KAB=25.4): dz/(1+z)<0.055
  • Deep I-selection misses only a small fraction of deep K selected
  • objects. Surveys to IAB=27 also cover a large fraction of submm gals.
  • Derive masses from broadband SEDs by fitting exponential SFH +
  • bursts (with extinction); exp. SFHs only do NOT work for large
  • l-range (check via comparison with local SDSS+2MASS sample).
  • Further check: compare FDF I-selected with GOODS K-selected.
slide3

The FORS Deep Field (FDF, GTO project)

  • FDF goals: evolution of galaxies: their luminosity functions, star formation rates, morphologies, chemical abundances, dark halo properties, Tully-Fisher , FP relations etc...
  • Imaging in U,B,g,R,I,z,J,K (to AB ~ 27 in optical).
  • Depths within 0.5 ... 1 mag of Hubble Deep Fields.
  • Area ~5 times HDFs together (6.8‘ x 6.8‘).
  • 8000 objects with photometric z and type.
  • Spectroscopy available for ~360 galaxies.
  • HST Advanced Camera observations obtained.
  • FORS partners: Observatories in Heidelberg, Göttingen and Munich built two FORS spectrographs for the VLT.
  • FDF science team: Appenzeller, Bender, Böhm, Drory, Gabasch, Heidt, Hopp, Mehlert, Noll, Saglia, Seitz, Ziegler et al.
slide4

FDF field selection: DSS image

QSO 0103-260

z=3.36

FDF

Criteria: z>3 QSO in field, minimize foreground of stars and (z<0.2)

galaxies, high Galactic latitude, good accessibility from VLT

slide5

FORS Deep Field

FDF BRI real color image

FWHM = 0.45”

QSO 0103-260

z=3.36

slide7

HST ACS

FDF BRI

~1’x1’ enlargements

the goods south field
The Goods-South Field
  • J, H, K VLT images, 50 arcmin2, (8 tiles),

seeing 0.4-0.5”

  • K-selected catalog: 3297 galaxies to KAB=25.4
  • U, I: GOODS/EIS public survey
  • B, V, R: Garching/ Bonn deep survey

Salvato et al. 2006,

A&A, submitted

K-band 2.5’x2.5’

slide10

Global galaxy parameters from photometric redshifts

  • Advantages:
  • - large samples of ‘normal’ galaxies
  • - redshifts for faint objects
  • - full spectral energy distribution
  • - ‘cheap’ in telescope time
  • - modest amount of spectroscopy
  • needed to test reliability
  • Potential problems:
  • - accurate photometry needed
  • - calibrating galaxies are bright
  • - larger errors in redshift
  • - catastrophic failures in z
slide12

Semi-empirical SEDsderived from broad-band fluxes of galaxies with spectroscopic z by fitting them with SEDs of Bruzual&Charlot, Maraston and spectra from FDF, Kinney&Calzetti, Manucci

=> used as templates to determine photometric redshifts

slide15

check:

photo z

vs.

spec z

180 galaxies used to derive semi- empirical SEDs

180 galaxies in the control sample

QSO

Only ~ 1% catastrophic failures on normal galaxies! (mostly

very blue, faint dwarf objects with almost power-law SEDs)

slide16

check:

photo z

vs.

spec z

for

MB > -20

Photometric z for faint objects: o.k.!!

slide18

FDF redshift distribution: extends to z ~ 6 (similar to HDFs)

another check:

peaks in photometric

z distribution

well consistent

with peaks in

spectroscopic

z distribution

at: 0.22, 0.33,

0.39, 0.45,

0.77, 2.35,

3.38 (QSO)

slide19

MB distribution in FDF vs z

completeness

limits in FDF:

red massive

galaxies to

z ~ 2

blue star-

forming

galaxies to

z ~ 6

Most luminous

galaxies in

optical bands

tend to have

oldest SEDs

clustering in

redshift space

very obvious!

Ho = 70 km s-1 Mpc-1

Wm= 0.3, WL = 0.7

slide25

Estimating Schechter parameters F*, M*, a:

parameter coupling in luminosity function fits

V/Vmax and completeness

corrections applied

slide27

FDF

constraints

on aand M*between

z ~ 0.6

(low M*)

and

z ~ 3.5

(high M*)

(some low z bins have large errors because

scaling with c2

was applied)

2800 A

1500 A

z

g’

u’

slide28

What about Steidel et al. 1999: a ~ –1.6 ?

(galaxies selected by drop outtechnique)

FDF

Steidel et al. 1999

FDF

The faint end slope at 1700A:

z~3

z~4.1

slide29

FDF

FDF

Steidel et al. 1999

FDF:

z ~ 3

z ~ 4

  • cannot be settled definitely yet,

but a~ –1.6 pretty unlikely

slide31

Evolution of LF

in g’ band:

z = 0.3

to

z = 5.5

slide32

Evolution of LF

at 2800 A:

z = 0.3

to

z = 5.5

slide33

1500 A

2800 A

F*

vs.

M*

for

z = 0.6

to

z = 4.5

u’

g’

slide34

Evolution of M* and F* for fixed a

Fits based on FDF alone predict SDSS values reasonably well.

slide35

same B-band

evolution as

observed for

bright cluster

ellipticals:

DB ~ z

provides

SF history

consistent

with Madau

diagram

a and b values for 1500 A and

2800 A imply SFR ~ constant

the uv luminosity density and sfr
The UV-luminosity density and SFR

For the FDF, the extrapolation to L=0 in the calculation

of Ltot amounts to only 2%-20%, depending on redshift.

(no correction for dust)

slide37

Adelberger & Steidel (2000)

dust corrected

  • Evolution
  • of Star
  • Formation
  • Rate
  • Cosmic variance
  • between FDF and
  • GOODS <0.1dex
  • Luminous galaxies
  • immune to wave-
  • length dependent
  • selection effects.
  • Luminous galaxies
  • (B- to K-selected,
  • L>L*) contribute
  • only ~1/3 to total
  • star formation rate
  • at all redshifts.
  • Gabasch et al. 2004b,
  • ApJ Lett. in press

a= -1.6

a= -1.1

GALEX

slide38

Broadband galaxy masses from SED-fits: I. check by

application to combined SDSS+2MASS data set (exp.SFH+bursts)

Drory, Bender, & Hopp, ApJL, 616, 103

slide39

… and by

comparison

with masses

from spectral

analysis of

SDSS data

by Kauffmann

et al. (2003)

(17000 obj.):

o.k.!

Kauffmann + 2003

SDSS spectral feature mass

Mass from SED fitting

Drory + 2004

slide40

Residuals of photometric and spectroscopic masses

against a dynamical mass indicator: o.k.!

slide41

Evolution of

the galaxy

mass

function

at low z:

MUNICS

(photo z)

and

K20

(mostly

spectra)

slide42

Stellar

masses of

galaxies in

FDF and

GOODS S:

red=old

blue=young

at all z,

massive

galaxies

are older

than low

mass

objects!

Drory et al. 2005, ApJL, 619, 131

slide43

Evolution of the galaxy stellar mass function

with redshift:

Drory et al. 2005, ApJL, 619, 131

See poster by Pannella et al. for MF as function of morphology

slide44

Evolution of total stellar mass density.

Drory et al. 2005, ApJL, 619, 131

slide45

Number density evolution of massive galaxies.

Drory et al. 2005, ApJL, 619, 131

slide46

Specific star formation rates (from [OII]) to z ~ 1.5:

Bauer et al. 2005, ApJL, 621, 89

Bauer et al. 2006

Study star formation as a function of mass and

redshift.

slide47

Specific star formation rates (from UV cont.) z ~ 4.5:

Feulner et al. 2005, ApJL, 633, 9

Study star formation as a function of mass and

redshift: strong constraints on models of galaxy formation.

slide48

Specific star formation rates (from UV cont.) z ~ 4.5:

  • More massive galaxies
  • form their stars earlier.
  • Stars are formed by z~2
  • More massive galaxies
  • show a steeper decline
  • in SSFR.
slide49

Summary:

  • faint end slope of luminosity function is shallow at high z
  • LF evolution stronger at shorter wavelength
  • F* decreases, L* increases with redshift in all bands
  • analysis of cosmic SFH not very sensitive to l-selection
  • at all z, L>L* galaxies contribute ~1/3 to total SFR, but less to SSFR
  • at all z, massive galaxies are older than low mass galaxies
  • high mass galaxies form their stars earlier and faster
  • Papers: FDF+GOODS LFs, SFH: Gabasch et al. 2004, 2005
  • FDF+GOODS+MUNICS+SDSS+2MASS masses:
  • Drory et al. 2001, 2003, 2004, 2005
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