DISCOVERY OF z {approx} 8 GALAXIES IN THE HUBBLE ULTRA DEEP FIELD FROM ULTRA-DEEP WFC3/IR OBSERVATIONS

Journal Article · Mon Feb 01 04:00:00 EST 2010 · Astrophysical Journal Letters

DOI:https://doi.org/10.1088/2041-8205/709/2/L133; COUNTRY OF INPUT: INTERNATIONAL ATOMIC ENERGY AGENCY (IAEA)· OSTI ID:21301365

Bouwens, R J; Illingworth, G D; Magee, D; Gonzalez, V ^[1]; Oesch, P A; Carollo, C M ^[2]; Stiavelli, M ^[3]; Van Dokkum, P ^[4]; Trenti, M ^[5]; Labbe, I ^[6]; Franx, M ^[7]

---

1. UCO/Lick Observatory, University of California, Santa Cruz, CA 95064 (United States)
2. Institute for Astronomy, ETH Zurich, 8092 Zurich (Switzerland)
3. Space Telescope Science Institute, Baltimore, MD 21218 (United States)
4. Department of Astronomy, Yale University, New Haven, CT 06520 (United States)
5. University of Colorado, Center for Astrophysics and Space Astronomy, 389-UCB, Boulder, CO 80309 (United States)
6. Carnegie Observatories, Pasadena, CA 91101 (United States)
7. Leiden Observatory, Leiden University, NL-2300 RA Leiden (Netherlands)

We utilize the newly acquired, ultra-deep WFC3/IR observations over the Hubble Ultra Deep Field (HUDF) to search for star-forming galaxies at z {approx} 8-8.5, only 600 million years from recombination, using a Y {sub 105}-dropout selection. The new 4.7 arcmin{sup 2} WFC3/IR observations reach to {approx}28.8 AB mag (5{sigma}) in the Y {sub 105} J {sub 125} H {sub 160} bands. These remarkable data reach {approx}1.5 AB mag deeper than the previous data over the HUDF, and now are an excellent match to the HUDF optical ACS data. For our search criteria, we use a two-color Lyman break selection technique to identify z {approx} 8-8.5Y {sub 105}-dropouts. We find five likely z {approx} 8-8.5 candidates. The sources have H {sub 160}-band magnitudes of {approx}28.3 AB mag and very blue UV-continuum slopes, with a median estimated {beta} of {approx}<-2.5 (where f {sub {lambda}} {proportional_to} {lambda}{sup {beta}}). This suggests that z {approx} 8 galaxies are not only essentially dust free but also may have very young ages or low metallicities. The observed number of Y {sub 105}-dropout candidates is smaller than the 20 {+-} 6 sources expected assuming no evolution from z {approx} 6, but is consistent with the five expected extrapolating the Bouwens et al. luminosity function (LF) results to z {approx} 8. These results provide evidence that the evolution in the LF seen from z {approx} 7 to z {approx} 3 continues to z {approx} 8. The remarkable improvement in the sensitivity of WFC3/IR has enabled Hubble Space Telescope to cross a threshold, revealing star-forming galaxies at z{approx} 8-9.

• OSTI ID: 21301365
• Journal Information: Astrophysical Journal Letters, Journal Name: Astrophysical Journal Letters Journal Issue: 2 Vol. 709; ISSN 2041-8205
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
99 GENERAL AND MISCELLANEOUS
COLOR
DUSTS
GALACTIC EVOLUTION
GALAXIES
LUMINOSITY
RECOMBINATION
RED SHIFT
STARS
TELESCOPES