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

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 range (check via comparison with local SDSS+2MASS sample).

• Further check: compare FDF I-selected with GOODS K-selected.

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.

FDF

FDF field selection: DSS image

Criteria: z>3 QSO in field, minimize foreground of stars and (z<0.2) galaxies, high Galactic latitude, good accessibility from VLT

QSO 0103-260 z=3.36

FDF BRI real color image FWHM = 0.45”

QSO 0103-260 z=3.36

FORS Deep Field

~1’x1’ enlargements

~1’x1’ enlargements

HST ACSFDF BRI

K-band (26.3) selection (FIRES) vs I-band (26.8) selection (FDF)

FIRES onlyFDF as well

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’

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

Observed vs. synthetic color-color diagrams of stars used to check photometric calibration

Semi-empirical SEDs derived 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

Examples of template fits to FDF broad band photometry I

Examples of template fits to FDF broad band photometry II

QSO

180 galaxies used to derive semi- empirical SEDs

180 galaxies in the control sample

Only ~ 1% catastrophic failures on normal galaxies! (mostly very blue, faint dwarf objects with almost power-law SEDs)

check:

photo z vs.spec z

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

check:

photo z vs.spec z forMB > -20

FDF: distributions of photometric redshift errors and 2

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

another check:

peaks in photometricz distributionwell consistent with peaks inspectroscopicz distributionat: 0.22, 0.33, 0.39, 0.45, 0.77, 2.35, 3.38 (QSO)

MB distribution in FDF vs z

Ho = 70 km s-1 Mpc-1

m= 0.3,

completenesslimits in FDF:

red massive galaxies to z ~ 2

blue star-forminggalaxies toz ~ 6

Most luminousgalaxies in optical bands tend to haveoldest SEDs

clustering inredshift spacevery obvious!

Type classification: Sersic n vs. T vs. SED Type

all types

Type dependent angular clustering at 0.2 < zphot < 0.4

irregulars

early types

ellipticals

Estimating Schechter parameters *, M*, : parameter coupling in luminosity function fits

V/Vmax and completenesscorrections applied

The LF faint end slope in the FDF:

FDFconstraints on and M*between

z ~ 0.6(low M*)

and

z ~ 3.5

(high M*)

(some low z bins have large errors becausescaling with

was applied)

1500 A 2800 A

u’ g’

z

The faint end slope at 1700A:

z~3

z~4.1

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

(galaxies selected by drop out technique)FDF

Steidel et al. 1999

FDF

FDF

FDF

Steidel et al. 1999

FDF:

z ~ 3

z ~ 4

• cannot be settled definitely yet,

but ~ –1.6 pretty unlikely

Measured faint end slopes of the LFs in FDF:

adopted inthe following:

Evolution of LF

in g’ band:

z = 0.3

to

z = 5.5

Evolution of LF

at 2800 A:

z = 0.3

to

z = 5.5

1500 A 2800 A

u’ g’

*

vs.

M*

for

z = 0.6

to

z = 4.5

Evolution of M* and * for fixed

Fits based on FDF alone predict SDSS values reasonably well.

same B-bandevolution asobserved forbright cluster ellipticals: B ~ z

providesSF historyconsistentwith Madau diagram

a and b values for 1500 A and 2800 A imply SFR ~ constant

The UV-luminosity density and SFR

(no correction for dust)

Schechter Luminosity Function:

( ) exp

( ) (2 )tot

L LL

L L L

L L M dM L

φφ

φ φ

∗

∗ ∗ ∗

∗ ∗

⎛ ⎞ ⎛ ⎞= × −⎜ ⎟ ⎜ ⎟

⎝ ⎠ ⎝ ⎠

= = Γ −∫

28 1 31500 1.25 10 totSFR L M yr Mpc− − −= × e

For the FDF, the extrapolation to L=0 in the calculation of Ltot amounts to only 2%-20%, depending on redshift.

Evolutionof Star FormationRate • 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

GALEX

= -1.1

= -1.6

Adelberger & Steidel (2000)

dust corrected

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

Broadband galaxy masses from SED-fits: I. check by application to combined SDSS+2MASS data set (exp.SFH+bursts)

SD

SS

spe

ctra

l fea

ture

mas

s

Mass from SED fitting Drory + 2004

… and bycomparisonwith massesfrom spectralanalysis ofSDSS data by Kauffmannet al. (2003)(17000 obj.):

o.k.!

Kau

ffm

ann

+ 2

003

Residuals of photometric and spectroscopic massesagainst a dynamical mass indicator: o.k.!

Evolution ofthe galaxy mass functionat low z:

MUNICS(photo z)

and

K20(mostlyspectra)

Stellarmasses of galaxies inFDF andGOODS S:

red=oldblue=young

at all z,massive galaxiesare older than lowmassobjects!

Drory et al. 2005, ApJL, 619, 131

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

Evolution of total stellar mass density.

Drory et al. 2005, ApJL, 619, 131

Number density evolution of massive galaxies.

Drory et al. 2005, ApJL, 619, 131

Bauer et al. 2005, ApJL, 621, 89 Bauer et al. 2006

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

Study star formation as a function of mass andredshift.

Feulner et al. 2005, ApJL, 633, 9

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

Study star formation as a function of mass andredshift: strong constraints on models of galaxy formation.

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

• More massive galaxiesform their stars earlier.• Stars are formed by z~2• More massive galaxies show a steeper declinein SSFR.

Summary:

• faint end slope of luminosity function is shallow at high z • LF evolution stronger at shorter wavelength• * decreases, L* increases with redshift in all bands• analysis of cosmic SFH not very sensitive to -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