STRUCTURE AND MORPHOLOGIES OF z {approx} 7-8 GALAXIES FROM ULTRA-DEEP WFC3/IR IMAGING OF THE HUBBLE ULTRA-DEEP FIELD

Journal Article · Wed Jan 20 04:00:00 EST 2010 · Astrophysical Journal Letters

DOI:https://doi.org/10.1088/2041-8205/709/1/L21; COUNTRY OF INPUT: INTERNATIONAL ATOMIC ENERGY AGENCY (IAEA)· OSTI ID:21301400

Oesch, P A; Carollo, C M ^[1]; Bouwens, R J; Illingworth, G D; Magee, D ^[2]; Trenti, M ^[3]; Stiavelli, M ^[4]; Labbe, I ^[5]

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1. Institute for Astronomy, ETH Zurich, 8092 Zurich (Switzerland)
2. UCO/Lick Observatory, University of California, Santa Cruz, CA 95064 (United States)
3. Center for Astrophysics and Space Astronomy, University of Colorado, 389-UCB, Boulder, CO 80309 (United States)
4. Space Telescope Science Institute, Baltimore, MD 21218 (United States)
5. Carnegie Observatories, Pasadena, CA 91101 (United States)

We present a first morphological study of z {approx} 7-8 Lyman break galaxies (LBGs) from Oesch et al. and Bouwens et al. detected in ultra-deep near-infrared imaging of the Hubble Ultra-Deep Field (HUDF) by the HUDF09 program. With an average intrinsic size of 0.7 {+-} 0.3 kpc, these galaxies are found to be extremely compact, having an average observed surface brightness of {mu} {sub J} {approx_equal} 26 mag arcsec{sup -2}, and only two out of the full sample of 16 z {approx} 7 galaxies show extended features with resolved double cores. By comparison to lower redshift LBGs, it is found that only little size evolution takes place from z {approx} 7 to z {approx} 6, while galaxies between z {approx} 4-5 show more extended wings in their apparent profiles. The average size scales as (1 + z){sup -m} with m = 1.12 {+-} 0.17 for galaxies with luminosities in the range (0.3-1)L* {sub z=3} and with m = 1.32 {+-} 0.52 for (0.12-0.3)L* {sub z=3}, consistent with galaxies having constant comoving sizes. The peak of the size distribution changes only slowly from z {approx} 7 to z {approx} 4. However, a tail of larger galaxies ({approx}>1.2 kpc) is gradually built up toward later cosmic times, possibly via hierarchical build-up or via enhanced accretion of cold gas. Additionally, the average star formation surface density of LBGs with luminosities (0.3-1)L* {sub z=3} is nearly constant at {sigma}{sub SFR} = 1.9 M {sub sun} yr{sup -1} kpc{sup -2} over the entire redshift range z {approx} 4-7 suggesting similar star formation efficiencies at these early epochs. The above evolutionary trends seem to hold out to z {approx} 8 though the sample is still small and possibly incomplete.

• OSTI ID: 21301400
• Journal Information: Astrophysical Journal Letters, Journal Name: Astrophysical Journal Letters Journal Issue: 1 Vol. 709; ISSN 2041-8205
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
99 GENERAL AND MISCELLANEOUS
BRIGHTNESS
GALACTIC EVOLUTION
GALAXIES
LUMINOSITY
MORPHOLOGY
RED SHIFT
STARS