SILVERRUSH. IV. Lyα luminosity functions at z = 5.7 and 6.6 studied with ∼1300 Lyα emitters on the 14–21 deg2 sky

By A. Konno, M. Ouchi, T. Shibuya, Yoshiaki Ono, K. Shimasaku, Yoshiaki Taniguchi, Tohru Nagao, Masakazu A. R. Kobayashi, M. Kajisawa, N. Kashikawa and 11 more. 2017

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We present the Ly$\alpha$ luminosity functions (LFs) at $z=$5.7 and 6.6 derived from a new large sample of 1,266 Ly$\alpha$ emitters (LAEs) identified in total areas of 14 and 21 deg$^2$, respectively, based on the early narrowband data of the Subaru/Hyper Suprime-Cam (HSC) survey. Together with careful Monte-Carlo simulations that account for the incompleteness of the LAE selection and the flux estimate systematics in the narrowband imaging, we have determined the Ly$\alpha$ LFs with the unprecedentedly small statistical and systematic uncertainties in a wide Ly$\alpha$ luminosity range of $10^{42.8-43.8}$ erg s$^{-1}$. We obtain the best-fit Schechter parameters of $L^{*}_{{\rm Lya}}=1.6^{+2.2}_{-0.6} (1.7^{+0.3}_{-0.7}) \times10^{43}$ erg s$^{-1}$, $\phi^{*}_{{\rm Lya}}=0.85^{+1.87}_{-0.77}\ (0.47^{+1.44}_{-0.44})\times10^{-4}$ Mpc$^{-3}$, and $\alpha=-2.6^{+0.6}_{-0.4}\ (-2.5^{+0.5}_{-0.5})$ at $z=5.7$ ($6.6$). We confirm that our best-estimate Ly$\alpha$ LFs are consistent with the majority of the previous studies, but find that our Ly$\alpha$ LFs do not agree with the high number densities of LAEs recently claimed by Matthee/Santos et al.'s studies that may overcorrect the incompleteness and the flux systematics. Our Ly$\alpha$ LFs at $z=5.7$ and $6.6$ show an indication that the faint-end slope is very steep ($\alpha \simeq -2.5$), although it is also possible that the bright-end LF results are enhanced by systematic effects such as the contribution from AGNs, blended merging galaxies, and/or large ionized bubbles around bright LAEs. Comparing our Ly$\alpha$ LF measurements with four independent reionization models, we estimate the neutral hydrogen fraction of the IGM to be $x_{\rm HI}=0.3\pm0.2$ at $z=$6.6 that is consistent with the small Thomson scattering optical depth obtained by Planck 2016.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/9affed0b1722771ab660bc08d54245415d4e6c8f

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In Astronomy and Astrophysics

  1. M. Ouchi
  2. Yoshiaki Ono
  3. K. Shimasaku
  4. K. Nakajima
  5. Yoshiaki Taniguchi
  6. Y. Harikane
  7. Y. Matsuda
  8. Y. Komiyama

In Nuclear and High Energy Physics

  1. Tohru Nagao
  2. Yoshiaki Ono
  3. Yoshiaki Taniguchi
  4. Masayuki Umemura
  5. Masao Mori
  6. Y. Harikane
  7. T. Shibuya
  8. K. Hasegawa

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