Introducing Gourav Khullar

Gourav Khullar (@isskywalker, Pronouns: he/him) is a PhD Candidate at the University of Chicago, affiliated with the Dept. of Astronomy and Astrophysics, and the Kavli Institute of Cosmological Physics. An Indian national, he has been in Chicago since 2015, having moved to the US from the University of Cambridge with a masters degree in Astrophysics, and the Indian Institute of Technology, Delhi with a bachelors degree in Engineering Physics.
Gourav’s research focuses on the astrophysics of member galaxies of high-redshift galaxy clusters, which he studies via tools like optical-infrared spectroscopy and strong gravitational lensing. Gourav is part of the South Pole Telescope (SPT) Clusters collaboration, and is also affiliated with the Dark Energy Survey (DES). Counting himself as an observer and an analyst, Gourav is a frequent user of the Magellan Telescopes and the Cerro Tololo Inter-American Observatory (CTIO) in Chile for his research. His past work as an undergraduate and masters student includes an analysis of host galaxy properties in DES-discovered active galactic nuclei (AGN), understanding chemical enrichment in galaxy environments via simulations and observations, spectroscopic studies of Type Ib supernovae, and building stellar speckle interferometric apparatus in a laboratory that mimic adaptive optics systems on telescopes.
Outside astrophysics research, Gourav has also been a part of the Astrobites collaboration since 2015, both as a science communication writer-editor and an education researcher. Gourav also works on issues of social justice, having co-founded initiatives like the Diversity, Equity and Inclusion Journal Club (DEIJC) at UChicago, a platform that helps early-career astrophysicists create an equitable and inclusive local community through peer education. He is an organizer and officer with Graduate Students United – UChicago’s graduate worker union – which has been fighting for labor rights for graduate members of the UChicago community. On a light day, you would find Gourav reading non-fiction books, listening to Punjabi music, or at a movie theatre checking out the latest superhero flick!
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Introducing James Matthews

James Matthews is postdoctoral researcher at University of Oxford where he tries to understand where the highest energy cosmic rays come from. Cosmic rays are particles with energies up to 100 billion billion electron volts (that’s a lot of energy!) that strike our atmosphere and produce showers of secondary particles, which we can detect at places like the Pierre Auger observatory. Although they were discovered at the start of the 20th century, we still don’t really know where the highest energy cosmic rays come from.
James’ work is mostly theoretical; I do hydrodynamics simulations of outflows from active galactic nuclei (AGN) to see if they produce the observed cosmic rays. AGN are supermassive black holes that shine brightly due to the gas that is falling onto them, meaning they are interesting for all sorts of reasons — not just for cosmic ray astrophysicists! So, he also works on trying to generally understand the outflows and accretion discs that form part of their sometimes confusing behaviour. James’ PhD thesis, completed at the University of Southampton, focused on this topic. Outside of academia James plays guitar and keyboards in a band called Waking Aida and enjoy football, squash and good pubs!

Introducing Héctor Vives-Arias

Héctor Vives-Arias (@DarkSapiens) obtained his PhD in Physics at the University of Valencia, Spain, using gravitational lenses to study both the structure of quasars and the distribution of dark matter subhaloes. He is currently a postdoc at the Instituto de Astrofísica de Canarias (IAC), where he works with ALMA observations of the active galactic nucleus in NGC 1068 to try to understand the structure and kinematics of the dust and molecular gas surrounding its center.
In his last year as an undergrad he got a summer grant at the IAC, where he analyzed the distribution and velocity of the gas in several nearby active galactic nuclei by working with near infrared integral field spectroscopy data from the SINFONI instrument at the VLT. For his Master’s thesis in Valencia, however, he switched to gravitational lens systems in which quasars were multiply imaged by foreground galaxies. Continuing this work on this PhD thesis, he used observations of the Einstein Cross in the optical and mid infrared (from the CanariCam instrument at the Gran Telescopio Canarias) to determine the size and temperature profile of the accretion disk of the quasar by studying the gravitational microlensing in the system, and also to estimate the amount of substructure in the dark matter halo of the lens galaxy that would produce the non-microlensed flux ratios between the quasar images. He also stayed for about a year at the University of Manchester, where he learned to work with radio interferometry data. There, he processed VLA observations of another lens system in order to measure the flux ratios between the multiple images, and to also determine the size of the radio emitting region.
He is currently working on a study of a dozen quadruply lensed systems to estimate the abundance of dark matter subhaloes from the flux ratios between the quasar images in observations of their narrow line regions, radio cores, and dusty tori, while also analyzing ALMA data of nearby active galactic nuclei to study those dusty tori directly in his recently started postdoc at the IAC.
Despite his research focus on active galaxies and dark matter, his scientific interests are much broader than that, and he always tries to keep learning as much as he can about many different fields. He has a passion for science communication that has helped him remain motivated in the low moments of academic life, and he regularly enjoys explaining science on Twitter, blog articles, radio programs, podcasts, and public talks. Other hobbies include archery, drawing, and 3D animation and rendering.