Blog posts tagged with spectroscopy

Posts in the past four weeks

Jul 08 2015
22:23 UTC

GALAH data!

Today I got an unexpected treat when Melissa Ness showed me some new GALAH data from the HERMES instrument. The project is intending to take R 28000 spectra of about a million stars, and determine up to 30 element abundances, or something insane like that. Ness and I are looking at whether The Cannon could be used for basic parameter estimation and to assist in the long-run goals of the project. The data look absolutely beautiful and the first attempts with the data make it look like The Cann

Posted by Hogg's Research

Jul 04 2015
15:54 UTC

the probabilistic properties of The Cannon

... wrote text in the “Methods and data” section of the mass-and-age paper I am writing with Ness. I emphasized particularly the point that The Cannon is a probabilistic model: It is a likelihood function, which is optimized at training time, and then again at test time. The only difference between training and test is which parameters are varied. In the former, it is the spectral expectation and variance parameters, at fixed label values. In the latter, it is the label values, at

Posted by Hogg's Research

Jul 03 2015
03:59 UTC

writing about ages

... wrote a paragraph in the paper Ness and I are writing about inferring stellar ages from spetroscopy.

Posted by Hogg's Research

Jun 18 2015
03:59 UTC

Conroy's stars, and kernel learning

We had a star-studded group meeting today. It kicked off with Charlie Conroy (Harvard) talking about some of his recent projects. In one, he looks at the time dependence of pixel brightnesses in M87, because the long-period variables in the stellar population lead to long-period variations in brightness. In principle these variations are a function of stellar population age and density. He showed data from a huge but under-exploited HST program. In another project, he is working on varying

Posted by Hogg's Research

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