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An Observational Pursuit for Population III Stars in a Ly_alpha Emitter at z=6.33 through HeII Emission

Tohru Nagao·Kentaro Motohara·Roberto Maiolino·Alessandro Marconi·Yoshiaki Taniguchi·Kentaro Aoki·Masaru Ajiki·Yasuhiro Shioya
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Abstract

We present a very deep near-infrared spectroscopic observation of a strong Ly_alpha emitter at z=6.33, SDF J132440.6+273607, which we used to search for HeII 1640. This emission line is expected if the target hosts a significant number of population III stars. Even after 42 ksec of integration with the Subaru/OHS spectrograph, no emission-line features are detected in the JH band, which confirms that SDF J132440.6+273607 is neither an active galactic nucleus nor a low-$z$ emission-line object. We obtained a 2sigma upper-limit of 9.06e-18 ergs/s/cm^2 on the HeII 1640 emission line flux, which corresponds to a luminosity of 4.11e42 ergs/s. This upper-limit on the HeII 1640 luminosity implies that the upper limit on population III star-formation rate is in the range 4.9--41.2 M_sun/yr if population III stars suffer no mass loss, and in the range 1.8--13.2 M_sun/yr if strong mass loss is present. The non-detection of HeII in SDF J132440.6+273607 at z=6.33 may thus disfavor weak feedback models for population III stars.

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Tohru Nagao, Kentaro Motohara, Roberto Maiolino, Alessandro Marconi, Yoshiaki Taniguchi, Kentaro Aoki, Masaru Ajiki, Yasuhiro Shioya. 2005-08-21. An Observational Pursuit for Population III Stars in a Ly_alpha Emitter at z=6.33 through HeII Emission. https://doi.org/10.1086/497135

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