Plan of the talk: Density-Morphology relation Discovery of a post-starburst galaxy at z ~7 Photometric redshift estimates Evolution of LF of galaxies to z~2 Narrow-band searches for high-z galaxies with Subaru
AIMS (COSMOS) • evolution of galaxy morphology, SFR, merging, LF, correlation function as a function of LSS and redshift • Assembly of galaxies, clusters and dark matter up to 1014 Msun scales • Reconstruction of dark matter distribution up to z >1
AIMS (UDF) • Search for galaxies out to re-ionization epoch • Extend study of star formation rate in galaxies to z ~ 6 • Study rest-frame optical properties of galaxies to high redshifts • Estimate the luminosity function of galaxies at z ~ 6
AIMS (GOODS) • Study of the mass assembly rate and star formation in galaxies • Explore rest-frame morphologies of galaxies and their evolution with redshift • Provide multi-waveband data to address fundamental questions regarding the formation and evolution of galaxies
COSMOS: Morphology-Density Relation Bahram Mobasher Capak, Mobasher, Ellis, Scoville, Sheth, Abraham, ApJL 2005
Morphology-Density Relation: Progress & Issues Motivation: Role of environment in shaping Hubble sequence 0<z<1 Ingredients: ACS morphologies (+ proxies from photo-z/spectra) Photometric redshifts (for slices) Density estimates ( gals. Mpc-2 , lensing ….) Stellar masses (requires deeper K-band) Progress/issues: Auto/visual morphologies & photo-z tested in 3 x 3 inner field Robustness of 2-D as a tracer of 3-D density is an issue
Evolution of the T- relation 0 < z < 1 Smith et al 2004 (astro-ph/0403455) fE/S0 fE/S0 Environmental density plays key role in governing morphological mix: - Continued growth in high but delay for lower regions - Slower conversion of spirals to S0s with only Es at z > 1?
Evolution of the T- relation ACS clusters Holland et al 2004 (astro-ph/0408165) COSMOS fE/S0 Explores the high end in more detail via GTO cluster sample (N=7, E:S0) Illustrates the advantage of combining COSMOS with cluster datasets?
Morphological Catalog (Abraham, Sheth + RSE) Morph-cat (RGA): • based on earlier MDS, HDF precepts to I(AB)=24 • Asymm, Conc, Gini-C, • N ~ ? Reality check (RSE/KS): • visual catalog I(AB)=22.5 in inner 33 g+I zone • typed according to precepts used in MDS, HDF, GOODS - N~700 Extension to full area: N(tot) ~ ?
What limit for automated morphologies? Robustness of “classic” parameters (A-C test): I(AB)=22.5 (COSMOS) is broadly equivalent to I(AB)=24 (HDF)
But how reliable is a projected 2-D density? True spatial density / Measured in a photo-z slice Fidelity of using will depend on photo-z z, error and <z> itself (Benson VIRGO simulations)
Results • Density-morphology relation was already in place at z~1 • We see a steady increase in the fraction of elliptical galaxies with decreasing redshift from z=1.2 to present • The strength of this trend depends on the local density
Merging Photo-z & Morph-cats in the inner region V-I Photo-z Independent demonstration of robustness of photo-z’s
Search for the highest redshift galaxies B. Mobasher, M. Dickinson, H. C. Ferguson, M. Giavalisco, T. Wiklind, R. S. Ellis, M. Fall N. Grogin, L. Moustakas, N. Panagia D. Stark, M. Sossy, M. Stiavelli E. Bergeron, S. Casertano, A. Koekemoer, M. Livio, C. Scaralata Mobasher et al (2005) submitted
Hubble Ultra-Deep Field A sub-area of the GOODS-S (CDF-S) ACS Area: 3’ x 3’ mAB (z850LP) = 28.4 mag (10s for extended source over 0.2 arcsec2 aperture) NICMOS Area: 2.5’ x 2.5’ mAB(F160W) = 25.1 mag. (10s for extended source)
HUDF is fully covered By Spitzer GOODS-South
HUDF+GOODS-S ACS: B435V606 i775 z850LP NICMOS: J110H160 ISAAC: Ks Spitzer: IRAC (3.6-8.0 micron) MIPS: 24 micron Radio 1.4 GHz (ATCA, VLA) X-ray (Chandra) Ground-based UBVRIJHK images Photometric Redshifts -10% accurate
High-z selection Sources with (J – H)AB > 1.3 and no detection in optical-ACS bands were selected. Two sources were identified. One close to an X-ray source (likely an AGN) while the other is not associated with any X-ray (or radio) source- UDF033238.7-274839
Spectral Energy Distributions Simultaneously optimizing model parameters consisting of redshift (z), extinction (E(B-V)), starburst age (tsb) and metallicity (Z) Population synthesis models: STARBURST99 (Vazquez & Leitherer 2005) Bruzual & Charlot 2003
Model Parameters Parameter range: Redshift 0 < z < 12 Extinction 0 < E(B-V) < 1 Starburst age 0.1 < tsb < 5 Gyrs Metallicity 0.004, 0.008, 0.02, 0.04 Calzetti extinction law Salpeter IMF 0.1 < M < 100 Msun
Star formation laws Continuous SF mode Instantaneous SF- single SF burst follwed by a decrease for tsb yrs Exponentially decreasing SFR with e-folding time scale t=0,100,200,300,400 Myrs
Best SED Fits STARBURST99 Instantaneous star formation burst z=7.2; EB-V =0.05; tsb=600 Myrs Z=0.004 Bruzual & Charlot Exponentially decreasing SFR with t=0 z=7.0; E B-V =0.15; tsb=400 Myrs Z=0.008
Degeneracies It is possible that different combinations of parameters could Produce equally acceptable fits. low metallicity SED and high age or extinction could mimic an SED with higher metallicity and lower age/extinction
Every single combination of age (0.1-5 Gyrs) Metallicity (0.2-2.5 solar) Extinction (0 < E(B-V) < 1) Redshift (0 < z < 12) e-folding SFR (t=0-500) is considered
It is possible that the observed SED is caused by: • Contribution from old stellar population at z ~ 2-4 • heavily obscured starburst at lower redshifts • Complicated degeneracy between redshift, extinction, metallicity, age
An old population SED was simulated by fixing the age to 1-2 Gyr and fitting the rest of the parameters- no acceptable fit to the observed SED (at the > 5s level) was found at any redshift. • To fit the observed SED with a heavily reddened object, one needs E(B-V) > 0.5 and a MUCH reduced likelihood.
Spectroscopic Campaign Keck vs. Gemini Gemini vs. VLT VLT vs. Keck