Closed farr closed 7 years ago
More From ilya:
Finally, some more minor points:
Given my concerns above, which I think may be difficult to address promptly, I re-iterate my suggestion regarding Section 8 from some time ago. Let’s just add a caveat along these lines:
“The details of how well \chi_eff will be measured depends on the source properties, including the component masses and spins, source orientation and SNR, and detector and network properties which will vary in time [ref to Observing Scenarios document]. Therefore, the predictions regarding the expected number of observations required to reach confident conclusions about the distribution of spin-orbit misalignment angles may change, but we do not expect our qualitative conclusions to be affected.”
Ben had some responses and made some changes to text (including fixing the large/small q typo).
From Ilya:
Just to be clear: I have no doubt that the actual source parameters, including mass ratios and spins, can impact the accuracy of parameter estimation. And I agree that such a caveat is worth including.
My concern is with the statements we currently make: are they (A) correct and (B) relevant for this particular paper. I agree that relevance is in the eyes of the beholder, so if Will agrees that they are, I have no objection in principle. Regarding correctness, however, there are still some conclusions which, intuitively, I don’t find convincing, and I wonder if they are a consequence of some of the specific choices made, particularly using inspiral-only waveforms with an fixed cutoff. [Aside: was the same frequency cutoff used to estimate the SNR for detectability calculations?]
I do expect that higher \chi_eff will lead to better \chi_eff measurements, as more cycles are spent in the high v/c regime where higher-order pN effects, including spin-orbit coupling, are important. But I don’t see why high q should make it easier to measure \chi_eff; on the contrary, I expect that when q is low, more cycles will be spent near ISCO, and ultimately the test-particle inspiral is the best way to probe the more massive BH’s parameter space. In fact, we did not see the decrease in \chi_eff accuracy at more extreme mass ratios that you find when we analyzed IMRIs with IMR waveforms in arXiv:1511.01431 .
So my preference would be to omit these details, unless we are 100% certain about them, and just include a general caveat.
I'm happy to leave the section in (sorry, Ilya). Neither 1511.01431 nor this study correspond precisely to the mass range of interest (this study is too low, 1511.01431 too high); nor do they correspond to the optimal inference (truncated likelihood integral, approximate waveforms, etc). However, I think it is worth reminding people with a concrete example that chi_eff accuracy varies quite a bit over the parameter space, and we may well see large differences in future events.
From Ilya: