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Abstract Among the many different pieces of physics that go into simulations of the circumgalactic medium (CGM), the metagalactic ultraviolet background (UVB) plays a significant role in determining the ionization state of different metal species. However, the UVB is uncertain, with multiple models having been developed by various research groups over the past several decades. In this work, we examine how different UVB models influence the ionic column densities of CGM absorbers. We use these UVB models to infer ion number densities in the Figuring Out Gas and Galaxies In Enzo (FOGGIE) galaxy simulations atz= 2.5 and use the Synthetic Absorption Line Surveyor Application package to identify absorbers. Absorbers are then matched across UVB models based on their line-of-sight position so that their column densities can be compared. From our analysis, we find that changing the UVB model produces significant changes in ionization, specifically at lower gas densities and higher temperatures where photoionization dominates over collisional ionization. We also find that the scatter of column density differences between models tends to increase with increasing ionization energy, with the exception of Hi, which has the highest scatter of all species we examined.
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This content will become publicly available on May 30, 2026
Metagalactic Ultraviolet Background Tables for Calculating Diffuse Astrophysical Plasma Properties
Abstract In developing a deeper understanding of the Circumgalactic Medium, one feature that is poorly understood is the nature of the ultraviolet background (UVB) and its impact on observed column densities. A wide array of UVB models have been created over the years by many different authors, each based on the latest observational data available at the time. In addition to having a large variance between model properties, the formatting between released models is also inconsistent. This data release provides reformatted versions of several widely used ultraviolet background models—Faucher-Giguère et al., Haardt & Madau, Puchwein et al., and Faucher-Giguère 2020—such that each model is in the same units and thus can be utilized to directly compare these models over a wide redshift range. This release also includes code to run acloudy_cooling_toolspipeline to generate ionization tables for different UVB models.
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- Award ID(s):
- 1908109
- PAR ID:
- 10649353
- Publisher / Repository:
- American Astronomical Society
- Date Published:
- Journal Name:
- Research Notes of the AAS
- Volume:
- 9
- Issue:
- 5
- ISSN:
- 2515-5172
- Page Range / eLocation ID:
- 129
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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