The fall term astroseminars start off with a WCA Grad student special!
Hunter Martin, Rashaad Reid and Neo Dizdar will tell us about their research.
Hunter Martin
Title: Detecting Weak Lensing from Voids
Abstract: Voids, the large underdense holes of the cosmic web, impart a very weak "anti-"lensing signal on the images of background source galaxies. Detecting this signal would mean measuring the distribution of total matter density within a void, opening the doors to a new source of cosmological information like constraints on modified gravity models and neutrino mass, as well as help elucidate the formation and evolution of large-scale structure. However, this signal is far weaker per void than even the percent-level effect seen with the more conventional galaxy-galaxy lensing, and as such it needs to be demonstrated that this signal is measurable from current and future generation surveys. In my talk, I will present the techniques and measurements of void lensing from the SDSS BOSS void catalog using the UNIONS catalog of background sources. Further, I will show preliminary forecasts for what we can expect to detect from the Euclid survey using the Flagship simulation.
Rashaad Reid
Title: Structural Indications of Galaxy Cluster History
Abstract: Constraints on the cosmological parameters σ8 and ΩM derived from low-redshift observations are in tension with those derived from observations of the cosmic microwave background. Our ability to investigate this tension is limited by the degeneracy between the parameters when inferred from low-redshift structure. Information about galaxy cluster formation history can break this degeneracy, enabling us to better understand the σ8 and ΩM tension. We use the IllustrisTNG suite of simulations to explore structural probes of the dynamical state of clusters and their efficacy as proxies for their mass accretion histories. We find that large centre-of-mass offsets in clusters identify disturbed systems that have undergone recent major mergers. Some similar and readily observable quantities, such as the distribution of galaxies around the brightest cluster galaxy, are potential probes of mass accretion history as well. Understanding these relationships between structural properties and growth history may greatly improve the cosmological constraining power of cluster samples in forthcoming surveys.
Neo Dizdar
Title: XRISM: The Next Step for X-Ray Spectroscopy
Abstract: Coverage on the new X-ray space mission XRISM, and the impact it’s high spectral resolution micro-calorimeter has on galaxy cluster astronomy. This is a walkthrough of simulating and modelling high resolution spectra to produce proposals for observation time with the new telescope. Real data produced by the mission and the implications of low turbulent velocities with separate motions in the hotter and cooler metals will also be discussed.