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

Using a sample of nearly half million galaxies, intersected by over 7 millionlines of sight from the Sloan Digital Sky Survey Data Release 12, we traceH$\alpha$ + [N{\small II}] emission from a galactocentric projected radius,$r_p$, of 5 kpc to more than 100 kpc. The emission flux surface brightness is$\propto r_p^{-1.9 \pm 0.4}$. We obtain consistent results using only theH$\alpha$ or [N{\small II}] flux. We measure a stronger signal for the bluerhalf of the target sample than for the redder half on small scales, $r_p <$ 20kpc. We obtain a $3\sigma$ detection of H$\alpha$ + [N{\small II}] emission inthe 50 to 100 kpc $r_p$ bin. The mean emission flux within this bin is $(1.10\pm 0.35) \times 10^{-20}$ erg cm$^{-2}$ s$^{-1}$ \AA$^{-1}$, which correspondsto $1.87 \times 10^{-20}$ erg cm$^{-2}$ s$^{-1}$ arcsec$^{-2}$ or 0.0033Rayleigh. This detection is 34 times fainter than a previous strict limitobtained using deep narrow-band imaging. The faintness of the signaldemonstrates why it has been so difficult to trace recombination radiation outto large radii around galaxies. This signal, combined with published estimatesof n$_{\rm H}$, lead us to estimate the temperature of the gas to be 12,000 K,consistent with independent empirical estimates based on metal ion absorptionlines and expectations from numerical simulations.

Hydrogen Emission from the Ionized Gaseous Halos of Low Redshift Galaxies