Observational Cosmology Seminar

Filaments connecting galaxy clusters appear to contain the vast majority of the ‘missing baryons' in the form of a warm-hot intergalactic medium (WHIM) gas. The soft X-ray emission from this WHIM gas has now been detected in stacks of optically selected filaments and in a handful of individual nearby filaments, but the temperatures inferred from spectroscopic fits to these data are in general much higher than expected from simulations, in some cases by an order of magnitude. Utilizing eROSITA's sensitivity in the soft X-ray band, along with its wide field of view, raster scanning, and stable background, we are able to characterize this diffuse signal. In this analysis we utilize data from the eROSITA performance verification observations of the Abell 3391/3395 field, which have previously been analyzed to constrain the properties of three separate filamentary connections between clusters. I will present multiple improvements relative to these previous works, including the use of updated constraints on the soft X-ray background (SXRB) from other studies, accounting for spatial variation in the SXRB, and masking groups and clusters that are in projection with this system. I will also discuss future steps in this work, which includes combining the eROSITA data with thermal SZ measurements from Planck and SPT to better probe the density and temperature distributions of the filamentary gas in this system, along with applying this methodology to a larger sample of filaments with similar quality X-ray and SZ data.