We present a comprehensive analysis of z {gt} 8 galaxies based on ultra-deep WFC3/IR data. We exploit all the WFC3/IR imaging over the Hubble Ultra-Deep Field from the HUDF09 and the new HUDF12... Show moreWe present a comprehensive analysis of z {gt} 8 galaxies based on ultra-deep WFC3/IR data. We exploit all the WFC3/IR imaging over the Hubble Ultra-Deep Field from the HUDF09 and the new HUDF12 program, in addition to the HUDF09 parallel field data, as well as wider area imaging over GOODS-South. Galaxies are selected based on the Lyman break technique in three samples centered around z ~{} 9, z ~{} 10, and z ~{} 11, with seven z ~{} 9 galaxy candidates, and one each at z ~{} 10 and z ~{} 11. We confirm a new z ~{} 10 candidate (with z = 9.8 {plusmn} 0.6) that was not convincingly identified in our first z ~{} 10 sample. Using these candidates, we perform one of the first estimates of the z ~{} 9 UV luminosity function (LF) and improve our previous constraints at z ~{} 10. Extrapolating the lower redshift UV LF evolution should have revealed 17 z ~{} 9 and 9 z ~{} 10 sources, i.e., a factor ~{}3 { imes} and 9{ imes} larger than observed. The inferred star formation rate density (SFRD) in galaxies above 0.7 M $_{⊙}$ yr$^{-1}$ decreases by 0.6 {plusmn} 0.2 dex from z ~{} 8 to z ~{} 9, in excellent agreement with previous estimates. From a combination of all current measurements, we find a best estimate of a factor 10{ imes} decrease in the SFRD from z ~{} 8 to z ~{} 10, following (1 + z)$^{-11.4 ± 3.1}$. Our measurements thus confirm our previous finding of an accelerated evolution beyond z ~{} 8, and signify a very rapid build-up of galaxies with M $_{UV}$ {lt} -17.7 mag within only ~{}200 Myr from z ~{} 10 to z ~{} 8, in the heart of cosmic reionization. Based on data obtained with the Hubble Space Telescope operated by AURA, Inc., for NASA under contract NAS5-26555. Show less
Oesch, P.A.; Labbé, I.; Bouwens, R.J.; Illingworth, G.D.; Gonzalez, V.; Franx, M.; ... ; Magee, D. 2013
We present a study of rest-frame UV-to-optical color distributions for z ~{} 4 galaxies based on the combination of deep HST/ACS+WFC3/IR data with Spitzer/IRAC imaging. In particular, we use new,... Show moreWe present a study of rest-frame UV-to-optical color distributions for z ~{} 4 galaxies based on the combination of deep HST/ACS+WFC3/IR data with Spitzer/IRAC imaging. In particular, we use new, ultra-deep data from the IRAC Ultradeep Field program (IUDF10), together with previous, public IRAC data over the GOODS fields. Our sample contains a total of ~{}2600 galaxies selected as B-dropout Lyman-break Galaxies in the HUDF and its deep parallel field HUDF09-2, as well as GOODS-North/South. This sample is used to investigate the UV continuum slopes {$β$} and Balmer break colors (J $_{125}$ - [4.5]) as a function of rest-frame optical luminosity (using [4.5] to avoid optical emission lines). We find that galaxies at M$_z$ {lt} -21.5 (roughly corresponding to L^{}*_${$z$ackslash$sim 4$}$) are significantly redder than their lower luminosity counterparts. The UV continuum slopes and the J $_{125}$ - [4.5] colors are well correlated, indicating that the dust reddening at these redshifts is better described by an SMC-like extinction curve, rather than the typically assumed Calzetti reddening. After dust correction, we find that the galaxy population shows mean stellar population ages in the range 10$^{8.5}$ to 10$^{9}$ yr, with a dispersion of ~{}0.5 dex, and only weak trends as a function of luminosity. Only a small fraction of galaxies shows Balmer break colors consistent with extremely young ages, younger than 100 Myr. Under the assumption of smooth star-formation histories, this fraction is 12%-19% for galaxies at M$_z$ {lt} -19.75. Our results are consistent with a gradual build-up of stars and dust in galaxies at z {gt} 4 with only a small fraction of stars being formed in short, intense bursts of star-formation. Based on data obtained with the Hubble Space Telescope operated by AURA, Inc. for NASA under contract NAS5-26555. Based on observations with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, California Institute of Technology under NASA contract 1407. Show less
![Rest-frame Optical Emission Lines in z ~ 3.5 Lyman-break-selected Galaxies: The Ubiquity of Unusually High [OIII]/Hβ Ratios at 2 Gyr](/sites/all/modules/custom/islandora_solr_search/images/defaultimg.png?solr_nav%5Bid%5D=78215327204ae1d35c01&solr_nav%5Bpage%5D=3&solr_nav%5Boffset%5D=4)
