Galaxies and Cosmology Seminar
Apr
6
2026
Apr
6
2026
Description
Probing the Circumgalactic Medium at the Peak of Star Formation with HETDEX
The circumgalactic medium (CGM) regulates gas accretion, feedback, and recycling, yet at high redshift it is usually studied through rare quasar sightlines that probe only tiny portions of galaxy halos. In this talk, I present a new statistical method for probing neutral gas in the CGM of HETDEX Lyα emitters (LAEs), using spectral stacking and diffuse background light. By stacking annular spectra around 88,000 LAEs, we measure the radial Lyα absorption equivalent-width (W_Lyα) profile and find that the average LAE at z~2.5 resides in extended reservoirs of neutral gas reaching out to 350 kpc. I will discuss the physical picture that motivates this method, comparisons to ASTRID simulations, and preliminary evidence that the radial W_Lyα profile may depend on the environment of these LAEs.
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