HeII Ly$\alpha$ Transmission Spikes and Absorption Troughs in Eight High-resolution Spectra Probing the End of HeII Reionization

Autor: Makan, Kirill, Worseck, Gábor, Davies, Frederick B., Hennawi, Joseph F., Prochaska, J. Xavier, Richter, Philipp
Rok vydání: 2021
Předmět:
Druh dokumentu: Working Paper
DOI: 10.3847/1538-4357/ac524a
Popis: We present statistics of HeII Lya transmission spikes and large-scale absorption troughs using archival high-resolution ($R=\lambda /\Delta \lambda \simeq 12,500$-$18,000$) far-UV spectra of eight HeII-transparent quasars obtained with the Cosmic Origins Spectrograph on the Hubble Space Telescope. The sample covers the redshift range 2.5100cMpc at z>3 to L~30cMpc at z~2.7, signaling a significant progression of HeII reionization at these redshifts. Furthermore, unexpectedly long L~65cMpc troughs detected at z~2.9 suggest that the UV background fluctuates at larger scales than predicted by current models. By comparing the measured incidence of transmission spikes to predictions from forward-modeled mock spectra created from the outputs of a (146cMpc)^3 optically thin Nyx hydrodynamical simulation employing different UV background models, we infer the redshift evolution of the HeII photoionization rate $\Gamma_\mathrm{He\,II}(z)$. The photoionization rate decreases with increasing redshift from $\simeq 4.6\times 10^{-15}\mathrm{\,s^{-1}}$ at z~2.6 to $\simeq 1.2 \times 10^{-15}\mathrm{\,s^{-1}}$ at z~3.2, in agreement with previous inferences from the HeII effective optical depth, and following expected trends of current models of a fluctuating HeII-ionizing background.
Comment: Accepted for publication in ApJ following minor revision (added 2 new figures); 16 pages, 14 figures
Databáze: arXiv
Externí odkaz: