Title: The Far Ultraviolet Background

Speaker: Professor Shrinivas R. Kulkarni

Time: 15:30, May 28（Wednesday）

Location: Room 215, No. 8 Hainayuan Building

Abstract:

Historically, the search for the inter-galactic medium (IGM) motivated the search for the Far Ultraviolet (<0.2 micron; FUV) background which in turn led to a number of experiments and missions.  Decades later the focus shifted to FUV as the primary heating and ionizing agent of the atomic phases (warm and cold neutral medium).  On the observational side, it was realized that at high Galactic latitudes, the diffuse FUV has three components: FUV light from hot stars in the Galactic plane reflected by dust grains (diffuse galactic light or DGL), FUV from other galaxies (extra-galactic background light, EBL) and a component of unknown origin.  This view has been amply confirmed by later GALEX observations.

During the eighties, there was considerable discussion that decaying dark matter particles produced FUV radiation.  In my talk I systematically investigate production of FUV photons from all major processes and sites of FUV production: the Galactic Hot Ionized Medium (line emission), two photon emission from the Warm Ionized Medium, fluorescence of molecular hydrogen, low velocity shocks in the Galaxy and Lyman fluorescence in the Solar System (the interplanetary medium and the exosphere of Earth). I will end the talk introducing the Ultraviolet Explorer (UVEX).

Biography:

Shrinivas R. Kulkarni, George Ellery Hale Professor of Astronomy and Planetary Science at Caltech. He received an MS in Physics from the Indian Institute of Technology, Delhi In 1978 and a Ph. D. in Astronomy from University of California Berkeley (UCB) in December 1983. Following a post-doctoral fellowship at Berkeley and a Millikan Fellowship, he joined Caltech faculty in 1987. He led or participated in the following discoveries: the first pulsar in a globular cluster, the first brown dwarf, suggesting a Galactic origin for soft gamma-ray repeaters and establishing the extra-galactic nature of gamma-ray bursts. He has received many awards with the most notable being the NSF Waterman Award, the Dan David Prize, and 2024 Shaw Prize in Astronomy. He is a fellow of the Royal Society of London, the US National Academy of Sciences, the Indian Academy of Sciences and the Royal Netherlands Society of Arts & Sciences.