English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Tools annual

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools monthly

Global: Zendy Plus monthly

Presents the access of premium content as premium feature

Premium Content

Global: Zendy Plus annual

Global: Zendy Free Plan

Quantitative estimates of the basic properties of the circumgalacticmedium(CGM), such as its density and metallicity, depend on the spectrum ofincident UV background radiation. Models of UV background are known to havelarge variations, mainly because they are synthesized using poorly constrainedparameters, which introduce uncertainty in the inferred properties of the CGM.Here, we quantify this uncertainty using a large set of new UV backgroundmodels with physically motivated toy models of metal-enriched CGM. We findthat, the inferred density and metallicity of low-density ($10^{-5}$ cm$^{-3}$)gas is uncertain by factors of 6.3 and 3.2, whereas high density ($10^{-3}$cm$^{-3}$) gas by factors of 4 and 1.6, respectively. The variation in theshape of the UV background models is entirely responsible for such a variationin the metallicity while variation in the density arises from bothnormalization and shape of the UV background. Moreover, we find a harder(softer) UV background infers higher (lower) density and metallicity. We alsostudy warm-hot gas at $T= 10^{5.5}$ K and find that metallicity is robustlyestimated but the inferred density is uncertain by a factor of 3 to 5.4 for lowto high-density gas. Such large uncertainties in density and metallicity mayseverely limit the studies of the CGM and demand better observationalconstraints on the input parameters used in synthesizing UV background.

How Robust are the Inferred Density and Metallicity of the Circumgalactic Medium?