Special FLASH Talks: Yashvi Sharma (Caltech) & Shri Kulkarni (OVRO, Caltech)

Tuesday, 02 May 2023 noon — 1 p.m. MST

NOIRLab Headquarters | 950 North Cherry Ave., Tucson, AZ 85719

Yashvi Sharma (Caltech) & Shri Kulkarni (OVRO, Caltech)

Yashvi Sharma, Caltech
Kitt Peak 84-inch - Rejuvenated & Ready
Time domain astronomy surveys are booming with identification of extragalactic transient candidates. The limiting step is spectral classification (the infamous "bottleneck"). Fully automated spectrographs on robotic telescopes are the way forward to tackle this issue, as already shown by SEDM on Palomar 60-in. In this talk, I’ll present SEDMv2 -- an improved second version of the very successful ultra-low resolution (R~100) IFU spectrograph mounted on the Kitt Peak 84-in telescope. Building on Caltech’s heritage with KP84 and KPED, i.e. robotocization (Robo-AO era) and remotely operable (KPED era), we have installed SEDMv2. I’ll talk about the improvements made on the telescope, the instrument’s dual capabilities (spectrograph as well as fast cadence imaging with EMCCD), expected improvements in instrument throughput over SEDM and data reduction pipelines. The telescope is now ready for LVK run O4. As we are still amidst the commissioning process, I’ll end the talk with planned necessary upgrades for better performance (i.e. mirror recoating) and our timeline for science operations.

Shri Kulkarni, OVRO, Caltech
(Newish) Diagnostics of the Galactic Warm Ionized Medium
The Galactic Warm Ionized Medium (WIM) is one of the four atomic phases of the Galaxy, containing most of the ionized gas (and not HII regions).  The traditional probes of the WIM are H-alpha (degree scale; Fabry-Perot) and pulsar dispersion measure (point measurement). Fabry-Perot observations have been conducted in a few optical nebular and auroral lines of metals.  The spectrum of the diffuse ionizing radiation field is fundamental to the physical modeling of the WIM. This can be determined by the ionization fraction of major elements. Here, I discuss the diagnostic power of  IFUs on large space- (JWST) & ground-based (Keck, VLT and Local Volume Mapper of SDSS-V) optical telescopes that allow us to study the WIM on scales of arcseconds. I fortify this conclusion by presenting detections of the Galactic diffuse medium via mid-IR fine structure lines with the MIRI-MRS IFU on JWST. Next, I argue that the nebular lines of [NI] are, in practice, a better proxy for ionization of hydrogen in the WIM, relative to the traditional [OI]6300 line.  I end the talk by reviewing an old but important topic: the ionization fraction of He in the WIM.