Hi everyone, I've returned from a long weekend to find what seems to be a pretty reasonable review of our paper. Some good suggestions for additional calculations/analysis. I'll likely be in direct contact with some of you for some more detailed thoughts on certain arguments.
Cheers, Jonnie ---------- Forwarded message ---------- From: <[email protected]> Date: Sat, Mar 21, 2015 at 3:02 PM Subject: Your ApJ Submission MS#ApJ98277 To: [email protected] Cc: [email protected] March 21, 2015 Dr. Jonathan C. Pober University of Washington Department of Physics Seattle, WA Title: PAPER-64 Constraints On Reionization II: The Temperature Of The z=8.4 Intergalactic Medium Dear Dr. Pober, I have received the referee's report on your above submission to The Astrophysical Journal, and appended it below. As you will see, the referee thinks that your article is interesting and that it will merit publication once you have addressed the issues raised in the report. When you resubmit the manuscript, please include a detailed cover letter containing the (mandatory) listing of the changes you've made to the text and your responses to the report. 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Vishniac Editor-in-Chief The Astrophysical Journal University of Saskatchewan ---------------------------------------------------------------------- Referee Report Reviewer's Comments: This paper presents a first interpretation of the recent PAPER-64 measurement of the HI 21 cm line power spectrum from z=8.4. This is an important result and, albeit still far from being a conclusive one, is very much in need of an in-depth exploration of its physical implications. The authors aim at doing so by using a simplified approach based on the choice of two main parameters, the mass-averaged spin temperature and neutral fraction of the intergalactic medium, and the use of the semi-numerical code 21CMFAST. I like the spirit of the study, in that it tries to preserve a physically transparent approach appropriate to a first-order investigation of the problem. At this stage, the approximations made are justified (I appreciate the several caveats on various neglected effects that might affect the final conclusions). However, there are a few tests and improvements that the authors could add which could make the paper more solid. These are listed below. The paper is clearly written and at the same time concise, a combination that I appreciate considerably. All in all, I would recommend the paper for publications after consideration of the following points by the authors. 1. Clearly, the major approximation made in the study is that the morphology of the spin temperature field is the same independently on the total intensity of the heating. This is a rather crude assumption, and it is necessary to quantify its impact on the final result with some tests in which such approximation is not made. The authors should at least provide an order of magnitude estimate of the expected error. 2. An aspect that can be also improved is the treatment of the absorbed fraction as a function of the photon energy and ionization fraction for which the authors use a range of constant values. As robust and detailed calculations based on Monte-Carlo simulations of the particle energy cascade provide simple but accurate fits (see e.g. eqs. 4-7 of Valdes & Ferrara 2008MNRAS.387L...8V, a relevant result that the authors have missed) at least a test should be performed with this more realistic physical modeling. 3. In Sec. 3.3 it is stated that "ionization histories and their associated power spectra for a large number of \zeta_X values". How many values have been explored and in what range? Also, what is the accuracy of the interpolation? 4. The meaning of the term "morphology", widely used in the paper, might not be immediately transparent to non-experts in the field. It would be very useful to define it clearly, e.g. at the beginning of Sec. 3. 5. Fig. 2: The rounded shape of the power spectrum contours is physically rich and deserves a few lines of physical interpretation when discussing such Figure. 6. Sec. 5.1 in the f_abs section: "The resultant hot electron" > "The resultant fast electron" (temperature for a single particle does not make sense). 7. Intro and Conclusions: "it has been determined that the observed high-redshift galaxy population cannot produce enough ionizing photons to complete the reionization of the Universe before z = 6". This point was made considerably earlier than the Finkelstein+12 and Robertson+15 studies, and at least the papers by Kuhlen+2012MNRAS.423..862K, and Choudhury+2008MNRAS.385L..58C must be added in this context.
