Large Disklike Galaxies at High Redshift
Abstract
Using deep near-infrared imaging of the Hubble Deep Field-South with the Infrared Spectrometer and Array Camera on the Very Large Telescope, we find six large disklike galaxies at redshifts z=1.4-3.0. The galaxies, selected in Ks (2.2 μm), are regular and surprisingly large in the near-infrared (rest-frame optical), with face-on effective radii re=0.65"-0.9" or 5.0-7.5 h-170 kpc in a Λ cold dark matter cosmology, comparable to the Milky Way. The surface brightness profiles are consistent with an exponential law over 2-3 effective radii. The Wide Field Planetary Camera 2 morphologies in Hubble Space Telescope imaging (rest-frame UV) are irregular and show complex aggregates of star-forming regions ~2" (~15 h-170 kpc) across, symmetrically distributed around the Ks-band centers. The spectral energy distributions show clear breaks in the rest-frame optical. The breaks are strongest in the central regions of the galaxies and can be identified as the age-sensitive Balmer/4000 Å break. The most straightforward interpretation is that these galaxies are large disk galaxies; deep near-infrared data are indispensable for this classification. The candidate disks constitute 50% of galaxies with LV>~6×1010 h-270 Lsolar at z=1.4-3.0. This discovery was not expected on the basis of previously studied samples. In particular, the Hubble Deep Field-North is deficient in large galaxies with the morphologies and profiles we report here.
Based on service mode observations collected at the European Southern Observatory, Paranal, Chile (ESO programme 164.O-0612) and also based on observations with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by AURA, Inc., under NASA contract NAS5-26555.- Publication:
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The Astrophysical Journal
- Pub Date:
- July 2003
- DOI:
- 10.1086/377149
- arXiv:
- arXiv:astro-ph/0306062
- Bibcode:
- 2003ApJ...591L..95L
- Keywords:
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- Galaxies: Evolution;
- Galaxies: High-Redshift;
- Infrared: Galaxies;
- Astrophysics
- E-Print:
- LaTeX, 5 pages, 2 figures, 1 table. Accepted for publication in the Astrophysical Journal Letters