Formation and evolution of early-type galaxies

Formation and evolution ofearly-type galaxies

Pieter van Dokkum (Yale)

Testing theories of galaxy formation

• Early-type galaxies have highest halo/stellar masses: provide strong constraints on galaxy formation models

or ?

Early-type galaxies at 0<z<1.5

• Can be identified out to z~1.5 (ACS/z)

• Make up sizable fraction of “Extremely Red Objects”

Moustakaset al 2003

Early-type galaxies at 0<z<1.5

• Can be identified out to z~1.5 (ACS/z)• Until recently, mostly studied in clusters

RXJ0848; z=1.27vD & Stanford 03

Early-type galaxies at 0<z<1.5

• Can be identified out to z~1.5 (ACS/z)• Until recently, mostly studied in clusters• Studies of colors, line strengths, Fundamental

Plane: stars formed at high redshifte.g., Ellis et al. 1997, Bernardi et al 98, Stanford et al 95/98, van Dokkum et al 98,01, Treu et al 99,02, …

Early-type galaxies at 0<z<1.5

• Can be identified out to z~1.5 (ACS/z)• Until recently, mostly studied in clusters• Studies of colors, line strengths, Fundamental

Plane: stars formed at high redshifte.g., Ellis et al. 1997, Bernardi et al 98, Stanford et al 95/98, van Dokkum et al 98,01, Treu et al 99,02, …

• Only small differences between field and cluster galaxies – contrary to expectations

Cluster versus field early-types

Datapoints: vD et al 98,01, vD & Ellis 03; see also Treu et al 99,02; van der Wel et al 03Models: Diaferio et al. 01

Early-type galaxies at 0<z<1.5

• Remarkable agreement observationally: early-type galaxies seem to have formed very early

• Caveats:– Results depend on IMF, metallicity, models– Progenitor bias: may miss youngest

progenitors– Assembly time may be (much) later than mean

star formation epoch• Solution: look for massive galaxies at z>2

(vD&Franx 01)

• L* Sb/c galaxy at z=3: K 23, R 28• Would not be selected by any current method

Typical Lyman-break galaxyand typical nearby spiral

Selecting optically-red z>2 galaxies

• Adopted criterion: J-K > 2.3– Models: selects galaxies at z > 2, ages larger

than ~500 Myr (in absense of dust)– Corresponds to U-V > 0.1 in the rest-frame for

galaxy at z = 3: would select most nearby gals

• Also expected:

– Dusty galaxies at z > 2 (enhances break)

– Extremely dusty galaxies at z < 2

Franx et al. 03, van Dokkum et al. 03, Daddi et al. 03

FIRES – VLT+ISAAC176 hours J,H,K imaging

MS 1054-03Foerster-Schreiber et al. 045.4’ x 5.4’, seeing 0’’45

HDF SouthLabbe et al. 032.4’ x 2.4’, seeing 0’’45

Optically-red galaxies at z>2

• Substantial surface density:~ 0.8/arcmin to K=21 (from both fields)~ 2/arcmin to K=22 (from HDF-S)~ 3/arcmin to K=23 (from HDF-S)

2

2

2

2

Optically-red galaxies at z>2

• Substantial surface density: ~ 0.8/arcmin to K=21 (from both fields)~ 2/arcmin to K=22 (from HDF-S)~ 3/arcmin to K=23 (from HDF-S)

• SEDs very different from Lyman breaks

2

2

2

Foerster Schreiber et al., in prep

Optically-red galaxies at z>2

• Substantial surface density: ~ 0.8/arcmin to K=21 (from both fields)~ 2/arcmin to K=22 (from HDF-S)~ 3/arcmin to K=23 (from HDF-S)

• SEDs very different from Lyman breaks• Spectroscopic redshifts tough - 11 so far

2

2

2

vD et al 03, Wuyts et al, in prep

Optically-red galaxy at z=2.43

Keck/NIRSPEC, 1½ hrsvD et al, ApJ, submitted

Optically-red galaxies at z>2

• Substantial surface density: ~ 0.8/arcmin to K=21 (from both fields)~ 2/arcmin to K=22 (from HDF-S)~ 3/arcmin to K=23 (from HDF-S)

• SEDs very different from Lyman breaks• Spectroscopic redshifts for 11 so far

• Rest-frame optical spectroscopy + SED fits: massive, dusty, star-forming galaxies

2

2

2

vD et al 03, Wuyts et al, in prep

vD et al, ApJ, submitted; Foerster Schreiber et al, in prep

• Best constrained parameter: stellar (and dyn) mass

vD et al, ApJ, submitted

Comparison to other star forming galaxies

LIRGSArmus et al 1989

normal nearby galaxiesJansen et al 2000

Solar

Comparison to other star forming galaxies

Correlations with linewidth

• Combining z=3 LBGs and z=2.6 ORGs: linewidth correlates with color and stellar mass

vD et al, ApJ, submitted

Kinematics of massive galaxies at 0<z<3

vD et al, ApJ, submitted

Kinematics of massive galaxies at 0<z<3

?

ERO

Early-type

ORG?

Spiral

LBG

Kinematics of massive galaxies at 0<z<3

ERO

Early-type

ORG

Spiral

LBG

Progenitors of early-type galaxies

• Substantial population of massive galaxies at z>2 with rest-optical colors similar to normal nearby galaxies

• Ideas have evolved rapidly .. not settled at all !– <1996: Radio galaxies, EROs– 1996: Lyman breaks– 2000: Scuba sources, hard X-ray sources– 2003: “K20” objects, ORGs (J-K>2.3)– 2004: Gemini Deep Deep Field galaxies

Franx et al 03, vD et al 03,04, Daddi et al 03, Foerster Schreiber et al 04

Progenitors of early-type galaxies

• Galaxies have optical breaks, and probably familiar metal lines in their rest-optical spectra– Absorption line studies: stellar kinematics,

masses– Presence of dynamically cold & hot

components– Diagnostics of stellar populations

• Not possible with current instruments/telescopes– Keck: 12 hrs to measure kinematics at z=1.27– At z=3: requires NIR capability (J/H sufficient)– JWST too small