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Formation and evolution of early-type galaxies Pieter van Dokkum (Yale)
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Testing theories of galaxy formation Early-type galaxies have highest halo/stellar masses: provide strong constraints on galaxy formation models or ?
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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” Moustakas et al 2003
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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=1.27 vD & Stanford 03
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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 redshift e.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, …
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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 redshift e.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
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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 03 Models: Diaferio et al. 01
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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)
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L* Sb/c galaxy at z=3: K 23, R 28 Would not be selected by any current method Typical Lyman-break galaxy and typical nearby spiral
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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
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FIRES – VLT+ISAAC 176 hours J,H,K imaging MS 1054-03 Foerster-Schreiber et al. 04 5.4’ x 5.4’, seeing 0’’45 HDF South Labbe et al. 03 2.4’ x 2.4’, seeing 0’’45
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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
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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
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Foerster Schreiber et al., in prep
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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 vD et al 03, Wuyts et al, in prep
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Optically-red galaxy at z=2.43 Keck/NIRSPEC, 1½ hrs vD et al, ApJ, submitted
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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 vD et al 03, Wuyts et al, in prep vD et al, ApJ, submitted; Foerster Schreiber et al, in prep
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Best constrained parameter: stellar (and dyn) mass vD et al, ApJ, submitted
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Comparison to other star forming galaxies LIRGS Armus et al 1989 normal nearby galaxies Jansen et al 2000 Solar
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Comparison to other star forming galaxies
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Correlations with linewidth Combining z=3 LBGs and z=2.6 ORGs: linewidth correlates with color and stellar mass vD et al, ApJ, submitted
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Kinematics of massive galaxies at 0<z<3 vD et al, ApJ, submitted
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Kinematics of massive galaxies at 0<z<3 ? ERO Early-type ORG ? Spiral LBG
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Kinematics of massive galaxies at 0<z<3 ERO Early-type ORG Spiral LBG
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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
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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
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