How probable is the Lyman-$α$ damping wing in the spectrum of the redshift z = 5.9896 quasar ULAS J0148+0600?
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| Format: | Preprint |
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2025
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| _version_ | 1866908383978717184 |
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| author | Sawyer, Fiona Bolton, James S. Becker, George D. Conaboy, Luke Haehnelt, Martin G. Keating, Laura Kulkarni, Girish Puchwein, Ewald |
| author_facet | Sawyer, Fiona Bolton, James S. Becker, George D. Conaboy, Luke Haehnelt, Martin G. Keating, Laura Kulkarni, Girish Puchwein, Ewald |
| contents | The shape of the Ly-$α$ transmission in the near zone of the redshift $z=5.9896$ quasar ULAS J0148$+$0600 (hereafter J0148) is consistent with a damping wing arising from an extended neutral hydrogen island in the diffuse intergalactic medium (IGM). Here we use simulations of late-ending reionisation from Sherwood-Relics to assess the expected incidence of quasars with Ly-$α$ and Ly-$β$ absorption similar to the observed J0148 spectrum. We find a late end to reionisation at $z=5.3$ is a necessary requirement for reproducing a Ly-$α$ damping wing consistent with J0148. This occurs in $\sim3$ per cent of our simulated spectra for an IGM neutral fraction $\langle x_{\rm HI}\rangle=0.14$ at $z=6$. However, using standard assumptions for the ionising photon output of J0148, the a priori probability of drawing a simulated quasar spectrum with a Ly-$α$ damping wing profile \emph{and} Ly-$α$ near zone size that simultaneously match J0148 is low, $p<10^{-2}$. This may indicate that the ionising emission from J0148 is variable on timescales $t<10^{5}\rm\,yr$, or alternatively that the Ly-$α$ transmission in the J0148 near zone is impacted by the transverse proximity effect from nearby star-forming galaxies or undetected quasars. We also predict the IGM temperature should be $T\sim 4\times 10^{4}\rm\,K$ within a few proper Mpc of the Ly-$α$ near zone edge due to recent H$\,\rm \scriptstyle I$ and He$\,\rm \scriptstyle II$ photo-heating. Evidence for enhanced thermal broadening in the Ly-$α$ absorption near the damping wing edge would provide further evidence that the final stages of reionisation are occurring at $z<6$. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2502_03085 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | How probable is the Lyman-$α$ damping wing in the spectrum of the redshift z = 5.9896 quasar ULAS J0148+0600? Sawyer, Fiona Bolton, James S. Becker, George D. Conaboy, Luke Haehnelt, Martin G. Keating, Laura Kulkarni, Girish Puchwein, Ewald Cosmology and Nongalactic Astrophysics The shape of the Ly-$α$ transmission in the near zone of the redshift $z=5.9896$ quasar ULAS J0148$+$0600 (hereafter J0148) is consistent with a damping wing arising from an extended neutral hydrogen island in the diffuse intergalactic medium (IGM). Here we use simulations of late-ending reionisation from Sherwood-Relics to assess the expected incidence of quasars with Ly-$α$ and Ly-$β$ absorption similar to the observed J0148 spectrum. We find a late end to reionisation at $z=5.3$ is a necessary requirement for reproducing a Ly-$α$ damping wing consistent with J0148. This occurs in $\sim3$ per cent of our simulated spectra for an IGM neutral fraction $\langle x_{\rm HI}\rangle=0.14$ at $z=6$. However, using standard assumptions for the ionising photon output of J0148, the a priori probability of drawing a simulated quasar spectrum with a Ly-$α$ damping wing profile \emph{and} Ly-$α$ near zone size that simultaneously match J0148 is low, $p<10^{-2}$. This may indicate that the ionising emission from J0148 is variable on timescales $t<10^{5}\rm\,yr$, or alternatively that the Ly-$α$ transmission in the J0148 near zone is impacted by the transverse proximity effect from nearby star-forming galaxies or undetected quasars. We also predict the IGM temperature should be $T\sim 4\times 10^{4}\rm\,K$ within a few proper Mpc of the Ly-$α$ near zone edge due to recent H$\,\rm \scriptstyle I$ and He$\,\rm \scriptstyle II$ photo-heating. Evidence for enhanced thermal broadening in the Ly-$α$ absorption near the damping wing edge would provide further evidence that the final stages of reionisation are occurring at $z<6$. |
| title | How probable is the Lyman-$α$ damping wing in the spectrum of the redshift z = 5.9896 quasar ULAS J0148+0600? |
| topic | Cosmology and Nongalactic Astrophysics |
| url | https://arxiv.org/abs/2502.03085 |