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Massive UV-Selected Galaxies at z~2

Massive UV-Selected Galaxies at z~2. Dawn Erb (Caltech) Chuck Steidel (Caltech), Alice Shapley (Berkeley), Max Pettini (IoA), Kurt Adelberger (OCIW), Naveen Reddy (Caltech). Overview.

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Massive UV-Selected Galaxies at z~2

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  1. Massive UV-Selected Galaxies at z~2 Dawn Erb (Caltech) Chuck Steidel (Caltech), Alice Shapley (Berkeley), Max Pettini (IoA), Kurt Adelberger (OCIW), Naveen Reddy (Caltech)

  2. Overview • Masses, kinematics, metallicities and star-formation histories of UV-selected galaxies at z~2, from optical and near-IR spectroscopy, optical through mid-IR imaging • ~8% of total sample has M*>1011 M, K<20, J-K>2.3 • Why z~2? • Large fraction of today’s stars formed in this era • Bridge gap between z~1 and z~3 • Much diagnostic info available, in rest-UV and optical

  3. Optical Photometric Pre-Selection • Green/yellow (LBGs): z=2.960.26 • Cyan (BX): z=2.260.32 • Magenta (BM): z=1.700.34 • Total surface density of BX+BM galaxies is ~9 arcmin-2 to R=25.5, ~25% of R-band surface density to R=25.5 Steidel et al 2004

  4. Spectroscopic Sample • Confirm redshifts in rest-frame UV • BM, z=1.70: 170 galaxies • BX, z=2.20: 780 galaxies • LBG, z=2.96: 950 galaxies • ~75 z~2 galaxies with M*>1011 M Steidel et al 2004

  5. IR, Mid-IR Observations • Deep J, K imaging with WIRC, Palomar 5-m, to Ks~22.5, J~23.8 • 4 fields, ~420 galaxies with zsp> 1.4 • Spitzer IRAC data in Q1700 field, 3.6, 4.5, 5.4, 8 m • Use for modeling stellar populations, masses

  6. IR, Mid-IR Observations • Deep J, K imaging with WIRC, Palomar 5-m, to Ks~22.5, J~23.8 • 4 fields, ~420 galaxies with zsp> 1.4 • Spitzer IRAC data in Q1700 field, 3.6, 4.5, 5.4, 8 m • Use for modeling stellar populations, masses

  7. UV to mid-IR Model SEDs • 72 galaxies detected in IRAC bands • ~8% (6/72) have M*>1011 M • 4/6 have J-K>2.3 • Same 4/6 have K<20 • 5/6 have ages of 2-3 Gyr • Best-fit  implies already massive at z~3 K=20.1 K=20.6

  8. Stellar masses, with and without IRAC data • Optical + IR + IRAC: log M* = 10.280.50; median 10.4 • Optical + IR only: log M* = 10.350.54; median 10.4 • Good news for ~300 galaxies without IRAC data • Usually no evidence from IRAC points for underlying old populations Steidel et al 2004, in prep

  9. Stellar mass vs. restframe near-IR, optical luminosity • At z~2, even mid-IR observations not direct tracers of stellar mass • Inferred stellar mass can differ by factor of ~10 at a given 4.5 m luminosity, ~70 at K-band Steidel et al 2004, in prep

  10. Massive galaxies and R-K color Circles=K<20

  11. Near-IR Spectroscopy M*=41011 M K=19.3, J-K=2.3 M*=5109 M • H spectra of 101 z~2 galaxies with NIRSPEC, Keck II • Kinematics: line widths, dynamical masses, some spatially resolved lines • [NII]/H ratios  metallicities • H fluxes  SFRs; compare UV, models • Outflows: offsets between nebular, UV absorption and Ly redshifts

  12. Stellar vs. Dynamical Masses • 63 galaxies, z=2.280.14 • Dynamical masses from H line widths, stellar masses from UGRJK modeling • M*=71010 M • Mdyn=41010 M for r=0.2˝ • Mdyn=11011 M for r=0.5˝ Erb et al 2004, in prep

  13. Morphologies and Sizes Erb et al 2004

  14. Metallicities and Stellar Masses • [NII]/H ratios for 30 galaxies in which [NII] detected • Point from composite spectrum of 14 galaxies (more to come…) • Mass-metallicity relation • Scatter expected when galaxies still forming • Large uncertainties • Galaxies with K~20 and M*~1011M have ~solar metallicities (Shapley et al 2004) AGN Erb et al 2004, in prep

  15. Metallicity Evolution Blaizot et al 2004; cosmological simulations + semi-analytic recipes • Galaxies with ~solar metallicity at z~2 will have super-solar metallicity at z=0 • Ellipticals and bulges

  16. Galactic-scale winds z~2 • Supernova-driven winds ubiquitous at z~2 and z~3 • Threshold > 0.1 M yr-1 kpc-2 easily met • Velocities ~200-400 km s-1 with respect to nebular line redshifts • Difference between Ly and interstellar absorption lines is ~500-1000 km s-1 • Winds enrich IGM, regulate star formation z~3 Steidel et al 2004

  17. Clustering • 26,000 galaxies • 21 fields • ~1500 spectroscopic redshifts • R=23.5-25.5 • Correlation lengths • z=2.9 (LBG): r0=4.00.6 h-1 Mpc • z=2.2 (BX): r0=4.20.5 h-1 Mpc • z=1.7 (BM): r0=4.50.6 h-1 Mpc • Implied halo masses ~1012 M (from comparison with GIF-LCDM numerical simulation) Adelberger et al 2004

  18. Evolution of clustering to z~1 and z~0.2 • Follow evolution of halo clustering in simulation • Matches early-type absorption line DEEP2 galaxies at z~1 (Coil et al. 2003) • Matches SDSS ellipticals at z~0.2 (Budavari et al. 2003) • Typical galaxy will evolve into elliptical by z=0 Adelberger et al 2004

  19. Number density and clustering strength at z~0.2 Bright LBGs Typical LBGs Galaxy populations In SDSS Adelberger et al 2004

  20. Clustering strength vs. K • Clustering vs. K mag (1.8<z<2.6) • Ks<20.5: r0=103 h-1 Mpc • Ks>20.5: r0=40.4 h-1 Mpc • Compare IR surveys • Caveat! Uncertainty because field choices not random, chosen to have QSOs Adelberger et al 2004, in prep

  21. Comparisons with z~3 Erb et al 2004, in prep Steidel et al 2004 • Average velocity dispersion, R-K color larger at z~2 • Most massive z~2 galaxies have likely progenitors among LBGs, and were already massive at z~3 • More to come…

  22. BzK colors of UV-selected galaxies • Works very well for K<21, misses ~half with K>21 • Missed galaxies have M*=7109 M, mean age 100 Myr • But UV selection misses reddest galaxies • Joint UV+BzK promising

  23. UV-selected star-forming galaxies at z~2: Summary

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