Astronomy Tea Talk

Speaker 1: Lordrick Kahinga

We leverage Fast Radio Bursts (FRBs) to study the gas mass fraction of the circumgalactic medium (CGM) of the Andromeda Galaxy (M31). Previous studies using quasar absorption lines and the Sunyaev-Zeldovich effect have constrained the cool (T < 10^5 K) and warm (10^5 K < T < 10^6K) phases of the CGM. However, the distribution of baryons in the hot phase (T > 10^6K) – which is expected to contain the majority of the mass - remains poorly understood due to the low sensitivity of X-ray observations. However, these may be detected in the dispersion measure (DM), which is sensitive to ionized gas in all phases. Using CHIME/FRB Catalog 2, we statistically compare the DMs of sightlines of FRBs intersecting the M31 halo with those that do not. We perform a Kolmogorov-Smirnov test comparing the two samples, yielding a p-value of 0.24, indicating no statistically significant detection of the M31 halo using DMs without weighting. We then employ a weighted mean difference approach to isolate the DM attributable to M31, finding that the M31 halo likely contributes on average 21-64 pc/cc between 0-150kpc and 30-62 pc/cc between 150 - 300 kpc from the projected center of its halo. We model the DM M31 contribution within a parametric framework based on a modified NFW profile and constrain the baryonic mass of the M31 halo to ~ 2 x 10^11 M⊙. This finding provides evidence at a 99.4% confidence level for a significant hot gas component in the galaxy.

Speaker 2: Barak Zackay

In this talk, I will review the recent efforts in my group to enhance the community's ability to detect complex and detail-rich signals. First, I will present a novel algorithm that utilizes time-of-arrival data to determine the periodicity of pulsars in gamma-ray data, employing algorithms for identifying the shortest vector in a lattice, adapted from cryptography and enhanced by our team. Second, I will present a novel algorithm for searching pulsars in binary systems, which can coherently explore the entire phase space of binary orbits with the same sensitivity as brute-force enumeration, yet many orders of magnitude more efficiently, making it feasible.