My goodness Wednesdays are good research days! As per usual, I spent the day at the CCA, where the research activity was dominated by my two group meetings. Here are some notes I took at each:
Sarah Pearson (Columbia) introduced herself at the stars group meeting; she talked about stellar streams and using them to constrain the shape of the MW dark-matter halo. With Pal 5 stream morphology alone, she can show that the Law & Majewski potential (used to explain Sagittarius) must be wrong, because it would create very strong stream fanning (which happens in chaotic potentials). Pearson is also thinking about finding thin streams in external galaxies, because morphology alone is so potentially constraining.
In the cosmology group meeting, Francisco Villaescusa-Navarro (CCA) spoke about HI gas and intensity mapping, in the context of large-scale structure with the SKA. There are strong trade-offs between resolution for angular and line-of-sight measures of the BAO. We discussed how to suppress the noise and foregrounds in practice for future measurements. He gets percent-level expectations for the Hubble Law at redshifts 0.5<z<2.5, which is promising, but will it satisfy our demands? That might be beat by Euclid! But he is considering only radial modes, not transverse modes. The discussion included lots of talk about beams, foregrounds, estimators, deconvolution, calibration, ancillary data, and self-calibration, with heavy participation by Kris Sigurdson (UBC).