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Publication Details
AFRICAN RESEARCH NEXUS
SHINING A SPOTLIGHT ON AFRICAN RESEARCH
Probing population III stars in galaxy IOK-1 at z = 6.96 through He II emission
Astrophysical Journal Letters, Volume 736, No. 2, Article L28, Year 2011
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Description
The He II λ1640 emission line has been suggested as a direct probe of Population III (PopIII) stars at high redshift, since it can arise from highly energetic ionizing photons associated with hot, metal-free stars. We use the Hubble Space Telescope WFC3/F130N IR narrowband filter to probe He II λ1640 emission in galaxy IOK-1 at z = 6.96. The sensitivity of this measurement is ≳5× deeper than for previous measurements. From this deep narrowband imaging, combined with broadband observations in the F125W and F160W filters, we find the He II flux to be (1.2 ± 1.0) × 10 -18 erg s-1 cm-2, corresponding to a 1σ upper limit on the PopIII star formation rate (SFR) of ∼0.5 M ⊙ yr-1 for the case of a Salpeter initial mass function (IMF) with 50 ≲ M/M⊙ ≲ 1000 and mass loss. Given that the broadband measurements can be fit with a UV-continuum spectral flux density of ∼4.85 × 10-10 × λ -2.46 erg Ås-1 cm-2 -1, which corresponds to an overall SFR of ∼16+2.6 - 2.6 M ⊙ yr-1, massive PopIII stars represent ≲ 6% of the total star formation. This measurement places the strongest limit yet on metal-free star formation at high redshift, although the exact conversion from He II luminosity to PopIII SFR is highly uncertain due to the unknown IMF, stellar evolution, and photoionization effects. Although we have not detected He II λ1640 at more than the 1.2σ level, our work suggests that a ≳ 3σ level detection is possible with the James Webb Space Telescope. © 2011. The American Astronomical Society. All rights reserved.
Authors & Co-Authors
Cai, Zheng
United States, Tucson
The University of Arizona
Fan, Xiaohui
United States, Tucson
The University of Arizona
Jiang, Linhua
United States, Tucson
The University of Arizona
Bian, Fuyan
United States, Tucson
The University of Arizona
McGreer, Ian D.
United States, Tucson
The University of Arizona
Dav́e, Romeel
United States, Tucson
The University of Arizona
Egami, Eiichi E.
United States, Tucson
The University of Arizona
Zabludoff, Ann I.
United States, Tucson
The University of Arizona
Yang, Yujin
Germany, Heidelberg
Max Planck Institute for Astronomy
Peng Oh, Siang Peng
United States, Santa Barbara
University of California, Santa Barbara
Statistics
Citations: 28
Authors: 10
Affiliations: 3
Identifiers
Doi:
10.1088/2041-8205/736/2/L28
ISSN:
20418213
Research Areas
Environmental
Study Design
Cross Sectional Study