The origin of the Kennicutt-Schmidt Relation in star forming galactic disks
Alex Gurvich (Northwestern University)
Abstract: How star formation rates are regulated in disk galaxies is a key question in galaxy evolution. Stellar feedback regulated models of galactic star formation posit that star forming galactic disks are governed by vertical equilibrium between gravity and pressure generated from stellar feedback. These models naturally predict Kennicutt-Schmidt (KS)-like relations with slopes that vary with galaxy composition, and thus provide a compelling origin story if the underlying assumptions of the models hold true. To test whether and how vertical pressure balance is achieved in Milky Way-mass star forming disk galaxies (and consequently whether/how the KS-relation is realized) we use the FIRE hydrodynamic cosmological zoom-in simulations to partition the ISM pressure between different gas phases (cold, warm, and hot) and types of pressure (thermal, turbulent, and bulk flow). We find that a dynamical equilibrium with steady-state inflows and outflows (vs. a hydrostatic equilibrium) is achieved with pressure near the midplane provided primarily from turbulence in the warm phase. We also confirm that the scaling relations used in deriving the KS relation hold in our sample, giving further evidence that vertical pressure balance is the mechanism by which star forming disk galaxies regulate their star formation rates to values consistent with the KS relation.
Astronomical spectrographs on a chip – Getting ready for the next-generation telescopes
Pradip Gatkine (CalTech)
Abstract: Astrophotonics is the application of versatile photonic technologies to channel, manipulate, and disperse guided light from one or more telescopes to achieve scientific objectives in astronomy in an efficient and cost-effective way. The photonic platform of guided light in fibers and waveguides has opened the doors to next-generation instrumentation for both ground- and space-based telescopes in optical and near/mid-IR bands, particularly for the large and extremely large telescopes (ELTs). Utilizing photonic advantage for astronomical spectroscopy is a promising approach to miniaturize the next generation of spectrometers for large telescopes and space-based telescopes. In this talk, I will discuss some of the recent results from our efforts to design and fabricate high-throughput on-chip spectrometers based on Arrayed Waveguide Gratings (AWG). These devices are ideally suited for capturing the AO-corrected light and enabling new and exciting science such as large-scale near-IR galaxy surveys to map the cosmic filaments or characterizing exoplanet atmospheres. I will also discuss specific approaches to make this technology science-ready for the ELT era.