Bertin, McCracken, Wu

I spent an enjoyable day at the IAP in Paris, chatting with the local luminaries. It was great to see the man himself Bertin (IAP), with whom I talked about extreme deconvolution, the Tractor, and modeling point-spread functions. On the former, he strongly encouraged us to work on photometric redshifts for galaxies (we have already done quasars); he expressed a strong conviction that most methods being developed were not properly taking into account the photometric uncertainties or noise, and therefore doomed to underperform. We could do this easily; the way Bovy set up XDQSO, it is an easy swap-in replacement of training data. Does anyone out there want to do this? I would be very happy to consult, and I bet we could convince Bovy too. A successful project could have a big impact on next-generation weak lensing projects.

McCracken (IAP) and I talked about calibration and catalog generation in huge new surveys. McCracken made a nice point (preaching to the converted I should say) that the generation of catalogs is very closely related to the calibration and reduction of the data. You can't really separate these, in part because if the catalog is an approximation to the parameters of a maximum-likelihood model, its creation depends sensitively on understandings of the noise. McCracken asked me to distinguish the Tractor from the next generation of SExtractor and I think the key point is that in the Tractor we see all the information as parameters; we make no distinction between catalog quantities and calibration quantities. We can also very flexibly freeze or fit parameters as our knowledge or confidence changes. That said, we are also vapor-ware right now!

My ex-student Ronin Wu is now at CEA, so we met at IAP. We talked about getting her most interesting thesis chapter—a measurement of the molecular-hydrogen mass function using Spitzer IRS spectroscopic data—ready for publication. It is very close, but we have some strange results that suggest that different radiation-hardness indicators don't correlate well, and that the star-formation rate is not a strong function of molecular gas mass. Those need to be tracked down or understood.