stars, planets, SPHEREx, and black-hole dark matter

In the last stars group meeting of the year, we had special guests John Brewer (Yale, AMNH) talking about the chemical abundances of stars hosting planets, Ellie Schwab (CUNY) talking about magnetic activity in low-mass stars and brown dwarfs, and Jackie Faherty (AMNH) talking about searches for long-period companions to solar-like stars. Brewer killed the diamond-planet hypothesis that was so cool a few years ago. Ue-Li Pen (CITA) commented to Schwab that 21-cm surveys (see yesterday's post) will and even already do have time-domain radio observations of thousands to millions of stars. And Faherty showed that searches for long-period companions have been incredibly productive, even though they haven't led to exoplanet discoveries (yet).

In the last cosmology group meeting of the year, we had special guests Roland de Putter (Caltech) talking about the observing plans for SPHEREx and Yacine Ali-Haimoud (JHU) talking about black-hole dark matter (my favorite theory of dark matter). SPHEREx performs a very cleverly designed 0.75-5 micron all-sky low-res spectral survey of every point on the sky. It will get redshifts for hundreds of millions of sources, with small photometric-redshift uncertainties. He talked about primordial non-linearity; the survey will get limits or a detection of fNL of <1. The audience was very interested in foregrounds, including Milky-Way stars, and even the zodiacal light in the Solar System.

Ali-Haimoud spoke about 2-body and 3-body effects in a black-hole theory of dark matter to get rates for LIGO. With careful re-analysis, he revises (heavily) the Ricotti et al 2008 limit on BHs as a dark-matter candidate and greatly weakens the constraints from CMB spectral distortions and anisotropies. But in the end he was very careful not to endorse black holes as a dark-matter canadidate. I'm stoked nonetheless!

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