FLASH Talks: Detection of a 100,000 Msun black hole at the center of the most massive globular cluster in M31 & External Calibrator for Hydrogen Observatories (ECHO)

Friday, 28 January 2022 noon — 1 p.m. MST

Renuka Pechetti (Liverpool) & Mrudula Gopal Krishna (ASU)

Renuka Pechetti (Liverpool) 

TItle: Detection of a 100,000 Msun black hole at the center of the most massive globular cluster in M31
Intermediate-mass black holes (IMBHs) are the connection between stellar-mass black holes and super-massive black holes. Finding these black holes can help us understand the evolution of the galaxies along with their black holes. But, IMBHs are extremely difficult to find as their effect on the surrounding stars is much weaker than a super-massive black hole. Hence, they require high-resolution measurements of the nearest possible targets. While no robust measurements exist till date, the possible IMBH candidates can provide key information on the formation of the initial seeds of supermassive black holes and the origin of the galaxy--black hole scaling relations.
I will present the detection of an IMBH at the center of the most massive globular cluster (B023-G078) in the nearest galaxy M31. We derived the mass models using HST observations for the globular cluster and combined these with adaptive optics high spatial resolution kinematics derived from GEMINI/NIFS IFU observations. We then used Jeans' anisotropic modeling to combine the mass models and kinematics to measure the black hole mass. This object is likely the stripped nucleus of a dwarf galaxy and this detection is more robust than any previous IMBH detection, including those in G1 or Omega Cen.

Mrudala Gopalkrishna, ASU

Title: External Calibrator for Hydrogen Observatories (ECHO)
Several low-frequency radio arrays with a large number of low-cost dipoles are being developed to probe the early universe through observations of the 21cm spin-flip transition of hydrogen. Telescopes in his regime include the LWA, MWA, LOFAR and HERA. The accuracy of their primary beams has been found to be a key limiting factor in mitigating confusion with foregrounds which are 10,000 times brighter than the cosmological signal. Current radio array models assume ideal radiation patterns however, due to manufacturing defects and installment tolerances, no two dipoles are completely alike. These as-built variations limit the precision to which foreground sources can be subtracted from the measured sky spectra. Traditional beam mapping methods like the use of electromagnetic models, astronomical sources, anechoic chambers and satellites have been employed to good effect but have fundamental limitations. A promising alternative is the use of drone-based calibrators. I will be talking about our progress toward development of a drone mounted calibrator which specifically addresses the 21cm instrument needs, results from integration with an operating LWA array and also note challenges of drone-based calibration in this low-frequency regime.


FLASH Talks are scientific talks for the staff at NOIRLab and the University of Arizona's Steward Observatory.