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Collaborators: Chuck Steidel (Caltech), Max Pettini (IoA), Alice Shapley (UCLA),

Naveen Reddy (Hubble Fellow, NOAO). Dust Obscuration and Metallicity at z~2: Implications for the Selection and Stellar Populations of High-Redshift Galaxies. Collaborators: Chuck Steidel (Caltech), Max Pettini (IoA), Alice Shapley (UCLA), Dawn Erb (UCSB).

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Collaborators: Chuck Steidel (Caltech), Max Pettini (IoA), Alice Shapley (UCLA),

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  1. Naveen Reddy (Hubble Fellow, NOAO) Dust Obscuration and Metallicity at z~2: Implications for the Selection and Stellar Populations of High-Redshift Galaxies Collaborators: Chuck Steidel (Caltech), Max Pettini (IoA), Alice Shapley (UCLA), Dawn Erb (UCSB) Hubble Fellows Symposium, STScI, Baltimore, MD, March 09, 2010

  2. Why z~2-3 is Interesting >50% of the stars in the present-day universe formed in the interval 3.5 > z > 1.5; peak of quasar activity Can watch all of the effects that shaped the present-day universe while they were happening Galaxies still bright enough for spectroscopic study on 8-10 m class telescopes Reddy et al 2008a Cosmologically interesting epoch where we also have access to a wealth of multi-wavelength indicators of star formation (UV, H-alpha, 24 micron, X-ray, radio)

  3. 0.1L* Advantages of our analysis • > 2000 spectroscopic redshifts at the bright-end • modeling of systematic effects • maximum-likelihood constraints on LF that are robust to non-uniform sources of scatter • - 31000 LBGs in 31 independent fields 0.07L* Results on the UV LF at z~2-3 Steep faint-end slope of  ~ -1.73, similar to that measured at z~4-6 Reddy et al 2009 Sub-L* Galaxies Dominate the UV Luminosity Density at z>2

  4. Dust Extinction in Typical High Redshift Galaxies L(8)  L(Ha)  L(IR) • Tight correlation between observed 24 micron (rest-frame 8 micron) dust luminosity and H luminosity • Correlation between UV slope and dust attenuation in L* galaxies at z~2 What about UV-faint galaxies?

  5. Correlation between Bolometric Luminosity and Dust Extinction at z~2 Saturation of UV luminosity around L*(UV) Log[L(bol)]=(0.69±0.03)log[L(IR)/L(UV)]+(10.91 ±0.04)

  6. Redshift Evolution of Dust Extinction • Tight correlation between bolometric luminosity and dust attenuation • But, typical z~2 galaxies are less dusty than local galaxies *at a give bolometric luminosity* • Evolution in extinction per unit SFR due to increasing dust-to-gas ratio? In practice, this means that UV selection probes a larger dynamic range at high redshift than one would infer from local observations

  7. Comparison of Metallicities: Oxygen Abundance vs. Dust Obscuration

  8. Systematics with Stellar Population Age Do younger galaxies at high redshift exhibit evidence for a steeper dust extinction curve?

  9. External Constraints on Stellar Populations

  10. Implications for High Redshift Galaxy Selection… SFRD • Redshift evolution of luminosity-obscuration/luminosity-metallicity relations implies an increasing UV transparency with larger look back time (missing dusty galaxies from UV-dropout surveys not as severe as one would have predicted from local observations) • Luminosity dependence of dust at any given epoch implies lower SFRDs; a more rapid rise in the SFRD to z~2; does it match the evolution of quasars? • Youngest galaxies (<100 Myr) at high-z consistent with steeper extinction law implying lower dust / bolometric SFR; even lower SFRDs at high redshift? • Adopting a common luminosity limit (accounting for L* evolution) and the luminosity/redshift dependence of dust allows us to recover the measured SMD from the integrated SFRD AGN LD Aird et al. (2010)

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