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Event Number 4660

  Thursday, October 12th, 2017

Astronomy Colloquium
"Observing gas in the circumgalactic medium and the Cosmic Web"
Time: 3:30 pm
Place: 4421 Sterling Hall, Coffee and Cookies 3:30 PM. Talk begins at 3:45 PM
Speaker: Bart Wakker, UW Madison Astronomy Dept
Abstract: Using HST spectra of AGN we study the gas inside and outside galaxy halos. We find that galaxies have extended (300 kpc radius) halos, which blend into the general intergalactic medium. We study properties of the gas as function of location in the galaxy halos. We also have constructed the first 3-D view of a 30x6 Mpc filament at cz~3500 km/s, This filamentis defined using a new catalogue of nearby galaxies, which is mostly complete down to a luminosity of about 0.05 L* and includes homogenized diameters and luminosities. The baryonic mass of the filament galaxies is 1.4x10^13 Msun, while the mass of filament gas outside galaxy halos is found to be 5.2x10^13 Msun. We find that simulations overpredict the detection rate of gas in the filament between 2.1 and 5 Mpc from the axis. The width of the Lya lines correlates with filament impact parameter and four BLAs in our sample all occur within 400 kpc of the filament axis, indicating increased temperature and/or turbulence. We further find that the recent Haardt & Madau (2012) extragalactic ionizing background predicts a factor 3-5 too few ionizing photons.
Host: Astronomy Department
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