Cosmic Reionization On Computers: Biases and Uncertainties in the Measured Mean Free Path at the End Stage of Reionization
Recent observations and analyses of absorption in quasar spectra suggest a rapid drop in the mean free path (MFP) at the late stage of reionization at $z\sim6$. We use the Cosmic Reionization on Computers simulation to examine potential biases in observed measurements of the MFP at the late stage of...
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Maynooth Academic Publishing
2025-06-01
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| Series: | The Open Journal of Astrophysics |
| Online Access: | https://doi.org/10.33232/001c.141394 |
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| author | Huanqing Chen Jiawen Fan Camille Avestruz |
| author_facet | Huanqing Chen Jiawen Fan Camille Avestruz |
| author_sort | Huanqing Chen |
| collection | DOAJ |
| description | Recent observations and analyses of absorption in quasar spectra suggest a rapid drop in the mean free path (MFP) at the late stage of reionization at $z\sim6$. We use the Cosmic Reionization on Computers simulation to examine potential biases in observed measurements of the MFP at the late stage of reionization, particularly in the presence of a quasar. We analyze three snapshots surrounding the 'ankle' point of reionization history, when extended neutral patches of the intergalactic medium disappeared in the simulation box. Specifically, these are $z=6.8$ (true MFP $\approx 0.4$~pMpc), in addition to $z=6.1$ (true MFP $\approx 2$~pMpc) and $z=5.4$ (true MFP $\approx 6$~pMpc). We compare the inferred MFP $\lambda_{\rm mfp}$ from synthetic spectra fits to the true MFP. We find that the mean Lyman continuum (LyC) profile at $z=6.8$ changes significantly with quasar lifetime $t_Q$. We attribute this sensitivity to $t_Q$ to a combination of extended neutral IGM patches and the prevalence of small-scale dense clumps. Consequently, the inferred MFP can be biased by a factor of few depending on $t_Q$. On the other hand, for the $z=6.1$ and $z=5.4$ snapshots, the mean LyC profile shows minimal sensitivity to variation in $t_Q\gtrsim 1$ Myr. The inferred MFP in these two cases is accurate to the $\lesssim 30\%$ level. Our results highlight how modeling systematics can affect the inferred MFP, particularly in the regime of small true MFP ($\lesssim 0.5$ pMpc). We also discuss the potential of this regime to provide a testing ground for constraining quasar lifetimes from LyC profiles. |
| format | Article |
| id | doaj-art-c9dc84e403b543499cdd75cc45502b11 |
| institution | Kabale University |
| issn | 2565-6120 |
| language | English |
| publishDate | 2025-06-01 |
| publisher | Maynooth Academic Publishing |
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| series | The Open Journal of Astrophysics |
| spelling | doaj-art-c9dc84e403b543499cdd75cc45502b112025-08-20T03:27:43ZengMaynooth Academic PublishingThe Open Journal of Astrophysics2565-61202025-06-01810.33232/001c.141394Cosmic Reionization On Computers: Biases and Uncertainties in the Measured Mean Free Path at the End Stage of ReionizationHuanqing ChenJiawen FanCamille AvestruzRecent observations and analyses of absorption in quasar spectra suggest a rapid drop in the mean free path (MFP) at the late stage of reionization at $z\sim6$. We use the Cosmic Reionization on Computers simulation to examine potential biases in observed measurements of the MFP at the late stage of reionization, particularly in the presence of a quasar. We analyze three snapshots surrounding the 'ankle' point of reionization history, when extended neutral patches of the intergalactic medium disappeared in the simulation box. Specifically, these are $z=6.8$ (true MFP $\approx 0.4$~pMpc), in addition to $z=6.1$ (true MFP $\approx 2$~pMpc) and $z=5.4$ (true MFP $\approx 6$~pMpc). We compare the inferred MFP $\lambda_{\rm mfp}$ from synthetic spectra fits to the true MFP. We find that the mean Lyman continuum (LyC) profile at $z=6.8$ changes significantly with quasar lifetime $t_Q$. We attribute this sensitivity to $t_Q$ to a combination of extended neutral IGM patches and the prevalence of small-scale dense clumps. Consequently, the inferred MFP can be biased by a factor of few depending on $t_Q$. On the other hand, for the $z=6.1$ and $z=5.4$ snapshots, the mean LyC profile shows minimal sensitivity to variation in $t_Q\gtrsim 1$ Myr. The inferred MFP in these two cases is accurate to the $\lesssim 30\%$ level. Our results highlight how modeling systematics can affect the inferred MFP, particularly in the regime of small true MFP ($\lesssim 0.5$ pMpc). We also discuss the potential of this regime to provide a testing ground for constraining quasar lifetimes from LyC profiles.https://doi.org/10.33232/001c.141394 |
| spellingShingle | Huanqing Chen Jiawen Fan Camille Avestruz Cosmic Reionization On Computers: Biases and Uncertainties in the Measured Mean Free Path at the End Stage of Reionization The Open Journal of Astrophysics |
| title | Cosmic Reionization On Computers: Biases and Uncertainties in the Measured Mean Free Path at the End Stage of Reionization |
| title_full | Cosmic Reionization On Computers: Biases and Uncertainties in the Measured Mean Free Path at the End Stage of Reionization |
| title_fullStr | Cosmic Reionization On Computers: Biases and Uncertainties in the Measured Mean Free Path at the End Stage of Reionization |
| title_full_unstemmed | Cosmic Reionization On Computers: Biases and Uncertainties in the Measured Mean Free Path at the End Stage of Reionization |
| title_short | Cosmic Reionization On Computers: Biases and Uncertainties in the Measured Mean Free Path at the End Stage of Reionization |
| title_sort | cosmic reionization on computers biases and uncertainties in the measured mean free path at the end stage of reionization |
| url | https://doi.org/10.33232/001c.141394 |
| work_keys_str_mv | AT huanqingchen cosmicreionizationoncomputersbiasesanduncertaintiesinthemeasuredmeanfreepathattheendstageofreionization AT jiawenfan cosmicreionizationoncomputersbiasesanduncertaintiesinthemeasuredmeanfreepathattheendstageofreionization AT camilleavestruz cosmicreionizationoncomputersbiasesanduncertaintiesinthemeasuredmeanfreepathattheendstageofreionization |