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 Plus annual

Presents the access of premium content as premium feature

Premium Content

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 Plus monthly

Global: Zendy Tools annual

Global: Zendy Tools monthly

Global: Zendy Free Plan

We show that it is now possible to image optically thick $\lya$ clouds influorescent $\lya$ emission with a relatively long ($\sim 20 $hr) integrationon a large ($\sim 10 $m) telescope. For a broad range of column densities($N\gsim 10^{18.5} \cm^{-2}$), the flux of $\lya$ photons from recombinationcascades is equal to $\sim 0.6$ times the flux of ionizing photons, independentof the geometry of the cloud. Additional $\lya$ photons are produced bycollisional excitations when these are the cloud's primary cooling mechanism.For typical physical conditions expected in optically thick clouds, thesemechanisms together lead to a $\lya$ emission flux that is $\sim (2/3)\VEV{\nu}/\nu_0$ times the flux of ionizing photons, where $\VEV{\nu}$ is themean frequency of ionizing background photons and $\nu_0$ is the Lyman limitfrequency. Hence, measurement of the surface brightness from an optically thickcloud (known to exist, e.g., from a quasar absorption line) gives a directmeasure of the energy in the ionizing radiation background. Moreover, in thesame long slit spectrum one could hope to detect emission from $\sim 200$ other$\lya$ systems. Such detections would allow one to make a 2-dimensional map ofthe $\lya$ forest. By taking a series of such spectra, one could map the forestin three dimensions, revealing structure in the high-redshift universe.Comment: Minor numerical change in abstract, no change in text, 23 page

Imaging the Forest of Lyman Limit Systems