the 21-cm signal from reionization

Adrian Liu (Berkeley) gave today's Astro Seminar. He spoke about the radio instruments PAPER and HERA, which are trying to see the 21-cm signal from reionization. He showed reasonable evidence that this signal will be strongest at around redshift 8. HERA is being built as a pre-cursor mission to the SKA. PAPER is done, and although the final data analyses are not complete, Liu claims that it has the best limits on the 21-cm emission from reionization, and they are a factor of tens higher than the expected signal. So there is work to do. He admitted that they are not doing the best they can on foregrounds: They are avoiding rather than modeling the foregrounds. After the talk we discussed this a bit; it connects to the things I am interested in regarding stage-four cosmology.

Late in the day, Megan Bedell (Chicago) pointed out to me that there are hundreds of stars with reduced, high resolution, high signal-to-noise spectra in the HARPS archive. Almost no-one (to our knowledge) is doing anything with these data. Crazy! We discussed plans to exploit this amazing data set.

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