656 research outputs found
Unveiling the nature of bright z ~ 7 galaxies with the Hubble Space Telescope
We present new Hubble Space Telescope/Wide Field Camera 3 imaging of 25
extremely luminous (-23.2 < M_ UV < -21.2) Lyman-break galaxies (LBGs) at z ~
7. The sample was initially selected from 1.65 deg^2 of ground-based imaging in
the UltraVISTA/COSMOS and UDS/SXDS fields, and includes the extreme Lyman-alpha
emitters, `Himiko' and `CR7'. A deconfusion analysis of the deep Spitzer
photometry available suggests that these galaxies exhibit strong rest-frame
optical nebular emission lines (EW_0(H_beta + [OIII]) > 600A). We find that
irregular, multiple-component morphologies suggestive of clumpy or merging
systems are common (f_multi > 0.4) in bright z ~ 7 galaxies, and ubiquitous at
the very bright end (M_UV < -22.5). The galaxies have half-light radii in the
range r_1/2 ~ 0.5-3 kpc. The size measurements provide the first determination
of the size-luminosity relation at z ~ 7 that extends to M_UV ~ -23. We find
the relation to be steep with r_1/2 ~ L^1/2. Excluding clumpy, multi-component
galaxies however, we find a shallower relation that implies an increased
star-formation rate surface density in bright LBGs. Using the new, independent,
HST/WFC3 data we confirm that the rest-frame UV luminosity function at z ~ 7
favours a power-law decline at the bright-end, compared to an exponential
Schechter function drop-off. Finally, these results have important implications
for the Euclid mission, which we predict will detect > 1000 similarly bright
galaxies at z ~ 7. Our new HST imaging suggests that the vast majority of these
galaxies will be spatially resolved by Euclid, mitigating concerns over dwarf
star contamination.Comment: 26 pages, 11 figures and 5 tables. Updated to match MNRAS accepted
versio
Morphology and Redshifts of Extremely Red Galaxies in the GOODS/CDFS deep ISAAC field
We present the photometric redshift distribution of a sample of 198 Extremely
Red Galaxies (ERGs) with Ks3.92 (Vega), selected by Roche et al.
in 50.4 sq. arcmin of the Chandra Deep Field South (CDFS). The sample has been
obtained using ISAAC-VLT and ACS-HST GOODS public data. We also show the
results of a morphological study of the 72 brightest ERGs in the z band (z<25,
AB).Comment: 2 pages, 2 figures. To appear in the proceedings of the ESO/USM/MPE
Workshop "Multiwavelength Mapping of Galaxy Formation and Evolution", Venice,
October 13-16, 200
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