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ABSTRACT The relevance of some galactic feedback mechanisms, in particular cosmic-ray (CR) feedback and the hydrogen ionizing radiation field, has been challenging to definitively describe in a galactic context, especially far outside the galaxy in the circumgalactic medium (CGM). Theoretical and observational uncertainties prevent conclusive interpretations of multiphase CGM properties derived from ultraviolet (UV) diagnostics. We conduct three-dimensional magnetohydrodynamic simulations of a section of a galactic disc with star formation and feedback, including radiative heating from stars, a UV background, and CR feedback. We utilize the temperature phases present in our simulations to generate Cloudy models to derive spatially and temporally varying synthetic UV diagnostics. We find that radiative effects without additional heating mechanisms are not able to produce synthetic diagnostics in the observed ranges. For low CR diffusivity $$\kappa _{\rm {cr}}=10^{28} \rm {cm}^2 \rm {s}^{-1}$$, CR streaming heating in the outflow helps our synthetic line ratios roughly match observed ranges by producing transitional temperature gas (T ∼ 105–106 K). High CR diffusivity $$\kappa _{\rm {cr}}=10^{29} \rm {cm}^2 \rm {s}^{-1}$$, with or without CR streaming heating, produced transitional temperature gas. The key parameter controlling the production of this gas phase remains unclear, as the different star formation history and outflow evolution itself influences these diagnostics. Our work demonstrates the use of UV plasma diagnostics to differentiate between galactic/circumgalactic feedback models. 

e present a sample of 305 QSO candidates having |b| < 30◦, the majority with GALEX magnitudes NUV < 18.75. To generate this sample, we apply UV-IR color selection criteria to photometric data from the Ultraviolet GAlactic Plane Survey (UVGAPS) as part of GALEX-CAUSE, the Million Quasars Catalog, Gaia DR2, and Pan-STARRS DR1. 165 of these 305 candidate UV-bright AGN (54%) have published spectroscopic redshifts from 45 different surveys, confirming them as AGN. We further obtained low-dispersion, optical, longslit spectra with the APO 3.5-m, MDM 2.4-m, and MDM 1.3-m telescopes for 84 of the candidates, and confirm 86% (N = 72) as AGN, generally with z < 0.6. These sources fill a gap in the Galactic latitude coverage of the available samples of known UV-bright QSO background probes. Along with a description of the confirmed QSO properties, we provide the fully-reduced, flux and wavelength-calibrated spectra of 84 low-latitude QSOs through the Mikulski Archive for Space Telescopes. Future HST/COS spectroscopy of these low-Galactic-latitude QSOs has the potential to transform our view of the Milky Way and Local Group circumgalactic medium. 

Abstract In this study, we investigate interstellar absorption lines along the line of sight toward the galactic low-mass X-ray binary Cygnus X-2. We combine absorption line data obtained from high-resolution X-ray spectra collected with the Chandra and XMM-Newton satellites, along with far-UV absorption lines observed by the Hubble Space Telescope’s (HST) Cosmic Origins Spectrograph (COS) instrument. Our primary objective is to understand the abundance and depletion of oxygen, iron, sulfur, and carbon. To achieve this, we have developed an analysis pipeline that simultaneously fits both the UV and X-ray data sets. This novel approach takes into account the line-spread function of HST/COS, enhancing the precision of our results. We examine the absorption lines of Feii, Sii, Cii, and Cipresent in the far-UV spectrum of Cygnus X-2, revealing the presence of at least two distinct absorbers characterized by different velocities. Additionally, we employCloudysimulations to compare our findings concerning the ionic ratios for the studied elements. We find that gaseous iron and sulfur exist in their singly ionized forms, Feiiand Sii, respectively, while the abundances of Ciiand Cido not agree with the Cloudy simulations of the neutral ISM. Finally, we explore discrepancies in the X-ray atomic data of iron and discuss their impact on the overall abundance and depletion of iron.