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 carried out deep mapping observations of the atomic hydrogen (HI) 21 cmline emission in a field centered on the famous galaxy group Stephan's Quintet(SQ), using the Five-hundred-meter Aperture Spherical Telescope (FAST) equippedwith the 19-Beam Receiver. The final data cube reaches an HI column densitysensitivity of $5 \sigma = 2.1\times 10^{17}$ cm$^{-2}$ per 20 km s$^{-1}$channel with an angular resolution of $4'.0$. The discovery of a large diffusefeature of the HI emission in the outskirt of the intragroup medium of SQ wasreported in a previous paper (Xu et al. 2022). Here we present a new study ofthe total HI emission of SQ and the detection of several neighboring galaxies,exploiting the high sensitivity and the large sky coverage of the FASTobservations. A total HI mass of $M_{\rm HI} = 3.48 \pm 0.35 \times 10^{10}\;M_\odot$ is found for SQ, which is significantly higher than previousmeasurements in the literature. This indicates that, contrary to earlierclaims, SQ is not HI deficient. The excessive HI gas is mainly found in thevelocity ranges of 6200 - 6400 km s$^{-1}$ and 6800 - 7000 km s$^{-1}$, whichwas undetected in previous observations that are less sensitive than ours. Ourresults suggest that the ``missing HI" in compact groups may be hidden in thelow-density diffuse neutral gas instead of in the ionized gas.

Deep HI Mapping of Stephan's Quintet and Its Neighborhood