0 Assigned ID: 2957 ----- Attempting Submission 1 (Thu Mar 24 09:55:54 GMT 2022) ----- HST Phase I Proposal 2957 successfully submitted. Receipt: # 2957-1 ----- Attempting Submission 2 (Fri Mar 25 21:33:44 GMT 2022) ----- HST Phase I Proposal 2957 successfully submitted. Receipt: # 2957-2 ----- Attempting Submission 3 (Fri Mar 25 23:14:01 GMT 2022) ----- The interface layers between hot and cool gas play a critical role in regulating the physical processes in galaxies and are crucial to theories of galaxy formation and evolution. The high ions OVI, NV, CIV, SiIV are the best probes of these interfaces. Yet their core properties are still poorly constrained because we have little direct observations of their dependence on the physical environments and metallicities. We propose to use the ULLYSES UV spectra of 239 hot stars to produce the first comprehensive analysis of the highly ionized gas in the LMC and SMC galaxies with a metallicity of 0.50 and 0.25 solar. The ULLYSES dataset is uniquely suited for this analysis owing to its uniformly high quality spectra. In addition, there is a wealth of ancillary data in the LMC and SMC, allowing for the characterization of the physical galactic environments at an unprecedented level of detail. Our program will enable the following key science goals: 1) we will characterize unambiguously for the first time the microphysics properties of the highly ionized gas in interface layers; 2) we will determine variations in these properties as a function of galactic environment and metallicity; and 3) we will help interpret low-resolution spectra of high ions in high-redshift objects by creating equivalent spectra by means of stacking and smoothing ULLYSES spectra covering prominent structures. We will release high-level data products, including a new classification scheme of the interstellar environment probed by each ULLYSES LMC/SMC target. Our program will pave a new path to understanding how the highly ionized gas in interface layers shapes galaxies. We have designed our team to bring the required observational and theoretical expertise in gas and stellar properties of the LMC and SMC and the physics of interface layers between the hot and cold gas. The proposed research program will be principally overseen by PI Lehner and co-led with a TBD postdoc. They will both lead the basic data reduction as well as the bulk of the analysis and interpretation of the results. The PI has led large surveys or similarly large efforts as the one proposed here in a timely manner. Each member has been the PI of several GO, archival/theory HST programs. Our team has published several tens of papers on these topics over the last 20+ years in major scientific journals, including Science and Nature, and is therefore well suited to successfully accomplish the proposed program. The PI Lehner and CoI Howk at the University of Notre Dame have over 2 decades of experience analyzing HST UV and FUSE spectra, including from the instrument STIS E140H/M, E230M/H and COS G130M/G160M/G185M. Of particular relevance, they are experts in analyzing interstellar absorption in stellar spectra, including supergiant early-type stars. The PI has led several large programs in the Milky disk, halo, and in the LMC that have used as UV background objects hot stars of all types, including one of the key STIS programs in the Milky Way that motivated in part this program. CoI Howk has led the first survey of the OVI in the LMC and was a key collaborator on a similar survey in the SMC. They are both specialist of the high ions and multiple gas-phases in the Milky Way, Magellanic Clouds, and in the low and high redshift universe. CoI Howk has also experience with stacking of spectra as he led spectral stacking experiments to detect faint spectral features in our Milky Way halo. CoI Tuli, a graduate student in the Howk-Lehner group, has working experience analyzing low and high ions stellar spectra observed with HST STIS and COS. CoI Barger is a specialist of the UV spectra and led a key study in the LMC using HST STIS observations that demonstrated the LMC has some large-scale outflows. She is an expert in optical spectral observations of the Magellanic System and she is one of the lead scientists of the WHAM instrument. She is the PI of the HST Legacy survey to study the large-scale outflows from the LMC using high-velocity absorption features observed at velocities intermediate between the Milky Way and the LMC. CoI Benjamin is a theorist of the physics of interstellar matter between stars, particularly the low density, hot gas and its interaction with cooler gas. He has developed non-equilibrium absorption line diagnostics for radiatively cooling gas. His expertise will be invaluable for the interpretations of the microphysics and macro-physics of the high ions as well to determine new observational diagnostics to test simulations. CoI You-Hua Chu is a leading expert of the stellar environments in the LMC and SMC. She has used multi-wavelength observations from radio to x-ray to study the formation of massive stars, energy feedback, and physics of interfaces and shocks in these galaxies. She has led the first survey of the high ions in the LMC using IUE to determine the impact of stellar regions on the high ion absorption. Her expertise of the LMC and SMC stellar regions will be critical to reliably and systematically classify the stellar regions in these galaxies. CoI Chu will also provide long-slit echelle spectra that Halpha and [N II] velocities of the ionized gas around the stars for most of the targets that were observed with FUSE. CoI Ting-Wen Lan has expertise in galaxy evolution and metal absorption line measurements. He has been working on exploring the properties of gas around high-redshift galaxies. In addition, he has experience with stacking analysis to reveal weak spectral features from large spectroscopic datasets. His experience will be extremely useful for the impact of our results for high redshift galaxies. CoI Sameer (future postdoc in the Howk-Lehner group at Notre Dame) has significant experience in handling UV spectra. He has expertise in extracting properties from absorption profiles using physically motivated models, which will help us for the characterization of the ionization properties of the interface layers in the LMC and SMC. CoI Savage has been a pioneer in UV spectroscopy instrumentation and the physics of the high ions in the Milky Way, Large Magellanic Clouds, and beyond. He has led many large-scale surveys of the OVI, CIV, SiIV, and NV in galactic and extragalalactic environments. His expertise will be invaluable for the interpretations of the microphysics of the high ions. CoI Shelton is a leading expert in modeling the interface layers between the hot and cold gas and understanding the properties of the high ions in interface layers. She uses computer clusters to simulate the hydrodynamic interaction between cold and hot gas to determine how mixing between cloud gas and hot gas occurs, predicting the amount of the high ions in and outside the interface layers. Her expertise will be invaluable for the interpretations of the microphysics of the high ions. As part of this program, CoI Shelton will calculate the line widths and ion ratios for the high and intermediate ions at different evolution times from her simulations of interface layers for a direct comparison with the empirical constraints from our proposed program. This will produce a new set of diagnostic tests to compare simulations and observations. CoI Wakker has an extensive background in studies of the interstellar and intergalactic medium, using data from ground-based radio and optical telescopes, as well as many of the UV space instruments. He is a member of the GASKAP team; GASKAP has surveyed the LMC in great detail in HI (0.1 km/s spectra resolution and 10 arcsec spatial resolution) and will produce a similar survey of the SMC in less than 2 years within the timeframe of this program. While the data from this program are public, as a member, CoI Wakker will have access to all the tools and infrastructure to use these data and further characterize the physical environments. Stellar Populations and the Interstellar Medium Galaxies 0 Regular false false false false false false SUPPORTED