%0 Generic %1 worseck2014giant %A Worseck, Gábor %A Prochaska, J. Xavier %A O'Meara, John M. %A Becker, George D. %A Ellison, Sara %A Lopez, Sebastian %A Meiksin, Avery %A Ménard, Brice %A Murphy, Michael T. %A Fumagalli, Michele %D 2014 %K high-z mfp %T The Giant Gemini GMOS survey of z>4.4 quasars - I. Measuring the mean free path across cosmic time %U http://arxiv.org/abs/1402.4154 %X We have obtained spectra of 163 quasars at $z_em>4.4$ with the Gemini Multi Object Spectrometers on the Gemini North and South telescopes, the largest publicly available sample of high-quality, low-resolution spectra at these redshifts. From this homogeneous data set, we generated stacked quasar spectra in three redshift intervals at $z5$. We have modelled the flux below the rest-frame Lyman limit ($łambda_r<912$\AA) to assess the mean free path $łambda_mfp^912$ of the intergalactic medium to HI-ionizing radiation. At mean redshifts $z_q=4.56$, 4.86 and 5.16, we measure $łambda_mfp^912=(22.22.3, 15.11.8, 10.3\pm 1.6)h_70^-1$ proper Mpc with uncertainties dominated by sample variance. Combining our results with $łambda_mfp^912$ measurements from lower redshifts, the data are well modelled by a simple power-law $łambda_mfp^912=A(1+z)/5^\eta$ with $A=(372)h_70^-1$ Mpc and $= -5.40.4$ between $z=2.3$ and $z=5.5$. This rapid evolution requires a physical mechanism -- beyond cosmological expansion -- which reduces the cosmic effective Lyman limit opacity. We speculate that the majority of HI Lyman limit opacity manifests in gas outside galactic dark matter haloes, tracing large-scale structures (e.g. filaments) whose average density (and consequently neutral fraction) decreases with cosmic time. Our measurements of the strongly redshift-dependent mean free path shortly after the completion of HI reionization serve as a valuable boundary condition for numerical models thereof. Having measured $łambda_mfp^91210$ Mpc at $z=5.2$, we confirm that the intergalactic medium is highly ionized by that epoch and that the redshift evolution of the mean free path does not show a break that would indicate a recent end to HI reionization.

@misc{worseck2014giant, abstract = {We have obtained spectra of 163 quasars at $z_\mathrm{em}>4.4$ with the Gemini Multi Object Spectrometers on the Gemini North and South telescopes, the largest publicly available sample of high-quality, low-resolution spectra at these redshifts. From this homogeneous data set, we generated stacked quasar spectra in three redshift intervals at $z\sim 5$. We have modelled the flux below the rest-frame Lyman limit ($\lambda_\mathrm{r}<912$\AA) to assess the mean free path $\lambda_\mathrm{mfp}^{912}$ of the intergalactic medium to HI-ionizing radiation. At mean redshifts $z_\mathrm{q}=4.56$, 4.86 and 5.16, we measure $\lambda_\mathrm{mfp}^{912}=(22.2\pm 2.3, 15.1\pm 1.8, 10.3\pm 1.6)h_{70}^{-1}$ proper Mpc with uncertainties dominated by sample variance. Combining our results with $\lambda_\mathrm{mfp}^{912}$ measurements from lower redshifts, the data are well modelled by a simple power-law $\lambda_\mathrm{mfp}^{912}=A[(1+z)/5]^\eta$ with $A=(37\pm 2)h_{70}^{-1}$ Mpc and $\eta = -5.4\pm 0.4$ between $z=2.3$ and $z=5.5$. This rapid evolution requires a physical mechanism -- beyond cosmological expansion -- which reduces the cosmic effective Lyman limit opacity. We speculate that the majority of HI Lyman limit opacity manifests in gas outside galactic dark matter haloes, tracing large-scale structures (e.g. filaments) whose average density (and consequently neutral fraction) decreases with cosmic time. Our measurements of the strongly redshift-dependent mean free path shortly after the completion of HI reionization serve as a valuable boundary condition for numerical models thereof. Having measured $\lambda_\mathrm{mfp}^{912}\approx 10$ Mpc at $z=5.2$, we confirm that the intergalactic medium is highly ionized by that epoch and that the redshift evolution of the mean free path does not show a break that would indicate a recent end to HI reionization.}, added-at = {2014-02-19T09:39:54.000+0100}, author = {Worseck, Gábor and Prochaska, J. Xavier and O'Meara, John M. and Becker, George D. and Ellison, Sara and Lopez, Sebastian and Meiksin, Avery and Ménard, Brice and Murphy, Michael T. and Fumagalli, Michele}, biburl = {https://www.bibsonomy.org/bibtex/2fdf48c096f0c040e77b2e4b30fded681/miki}, description = {[1402.4154] The Giant Gemini GMOS survey of z&gt;4.4 quasars - I. Measuring the mean free path across cosmic time}, interhash = {b4d8efc0324c5bd5010c84bddb7dff5e}, intrahash = {fdf48c096f0c040e77b2e4b30fded681}, keywords = {high-z mfp}, note = {cite arxiv:1402.4154Comment: 16 pages, 11 figures, plus 20 pages of online material; submitted to MNRAS}, timestamp = {2014-02-19T09:39:54.000+0100}, title = {The Giant Gemini GMOS survey of z>4.4 quasars - I. Measuring the mean free path across cosmic time}, url = {http://arxiv.org/abs/1402.4154}, year = 2014 }