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Title: PROBING POPULATION III STARS IN GALAXY IOK-1 AT z = 6.96 THROUGH He II EMISSION

Abstract

The He II {lambda}1640 emission line has been suggested as a direct probe of Population III (Pop III) 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 {lambda}1640 emission in galaxy IOK-1 at z = 6.96. The sensitivity of this measurement is {approx}>5x 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) x 10{sup -18} erg s{sup -1} cm{sup -2}, corresponding to a 1{sigma} upper limit on the Pop III star formation rate (SFR) of {approx}0.5 M{sub sun} yr{sup -1} for the case of a Salpeter initial mass function (IMF) with 50 {approx}< M/M{sub sun} {approx}< 1000 and mass loss. Given that the broadband measurements can be fit with a UV-continuum spectral flux density of {approx}4.85 x 10{sup -10} x {lambda}{sup -2.46} erg s{sup -1} cm{sup -2} A{sup -1}, which corresponds to an overall SFR of {approx}16{sup +2.6}{sub -2.6} M{sub sun} yr{sup -1}, massive Pop III stars represent {approx}< 6% of the total star formation.more » This measurement places the strongest limit yet on metal-free star formation at high redshift, although the exact conversion from He II luminosity to Pop III SFR is highly uncertain due to the unknown IMF, stellar evolution, and photoionization effects. Although we have not detected He II {lambda}1640 at more than the 1.2{sigma} level, our work suggests that a {approx}> 3{sigma} level detection is possible with the James Webb Space Telescope.« less

Authors:
; ; ; ; ; ; ;  [1];  [2];  [3]
  1. Steward Observatory, University of Arizona, Tucson, AZ 85721 (United States)
  2. Max-Planck-Institut fuer Astronomie, Koenigstuhl 17, D-69117, Heidelberg (Germany)
  3. Department of Physics, University of California, Santa Barbara, CA 93106 (United States)
Publication Date:
OSTI Identifier:
21562510
Resource Type:
Journal Article
Journal Name:
Astrophysical Journal Letters
Additional Journal Information:
Journal Volume: 736; Journal Issue: 2; Other Information: DOI: 10.1088/2041-8205/736/2/L28; Journal ID: ISSN 2041-8205
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; EMISSION; GALAXIES; PHOTOIONIZATION; PHOTOMETRY; RED SHIFT; STAR EVOLUTION; STARS; EVOLUTION; IONIZATION

Citation Formats

Cai Zheng, Fan Xiaohui, Jiang Linhua, Bian Fuyan, McGreer, Ian, Dave, Romeel, Egami, Eiichi, Zabludoff, Ann, Yang Yujin, and Oh, S. Peng, E-mail: caiz@email.arizona.edu. PROBING POPULATION III STARS IN GALAXY IOK-1 AT z = 6.96 THROUGH He II EMISSION. United States: N. p., 2011. Web. doi:10.1088/2041-8205/736/2/L28.
Cai Zheng, Fan Xiaohui, Jiang Linhua, Bian Fuyan, McGreer, Ian, Dave, Romeel, Egami, Eiichi, Zabludoff, Ann, Yang Yujin, & Oh, S. Peng, E-mail: caiz@email.arizona.edu. PROBING POPULATION III STARS IN GALAXY IOK-1 AT z = 6.96 THROUGH He II EMISSION. United States. doi:10.1088/2041-8205/736/2/L28.
Cai Zheng, Fan Xiaohui, Jiang Linhua, Bian Fuyan, McGreer, Ian, Dave, Romeel, Egami, Eiichi, Zabludoff, Ann, Yang Yujin, and Oh, S. Peng, E-mail: caiz@email.arizona.edu. Mon . "PROBING POPULATION III STARS IN GALAXY IOK-1 AT z = 6.96 THROUGH He II EMISSION". United States. doi:10.1088/2041-8205/736/2/L28.
@article{osti_21562510,
title = {PROBING POPULATION III STARS IN GALAXY IOK-1 AT z = 6.96 THROUGH He II EMISSION},
author = {Cai Zheng and Fan Xiaohui and Jiang Linhua and Bian Fuyan and McGreer, Ian and Dave, Romeel and Egami, Eiichi and Zabludoff, Ann and Yang Yujin and Oh, S. Peng, E-mail: caiz@email.arizona.edu},
abstractNote = {The He II {lambda}1640 emission line has been suggested as a direct probe of Population III (Pop III) 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 {lambda}1640 emission in galaxy IOK-1 at z = 6.96. The sensitivity of this measurement is {approx}>5x 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) x 10{sup -18} erg s{sup -1} cm{sup -2}, corresponding to a 1{sigma} upper limit on the Pop III star formation rate (SFR) of {approx}0.5 M{sub sun} yr{sup -1} for the case of a Salpeter initial mass function (IMF) with 50 {approx}< M/M{sub sun} {approx}< 1000 and mass loss. Given that the broadband measurements can be fit with a UV-continuum spectral flux density of {approx}4.85 x 10{sup -10} x {lambda}{sup -2.46} erg s{sup -1} cm{sup -2} A{sup -1}, which corresponds to an overall SFR of {approx}16{sup +2.6}{sub -2.6} M{sub sun} yr{sup -1}, massive Pop III stars represent {approx}< 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 Pop III SFR is highly uncertain due to the unknown IMF, stellar evolution, and photoionization effects. Although we have not detected He II {lambda}1640 at more than the 1.2{sigma} level, our work suggests that a {approx}> 3{sigma} level detection is possible with the James Webb Space Telescope.},
doi = {10.1088/2041-8205/736/2/L28},
journal = {Astrophysical Journal Letters},
issn = {2041-8205},
number = 2,
volume = 736,
place = {United States},
year = {2011},
month = {8}
}