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

Using the WSRT, we carried out shallow HI absorption observations of aflux-selected (S > 50 mJy) sample of 93 radio AGN with available SDSS redshiftsbetween 0.02 < z < 0.23. We study the gas properties of radio AGN down tofluxes not systematically explored before using, for the first time, stackingof extragalactic HI absorption. Despite the shallow observations, we obtained adirect detection rate of ~29%, comparable with deeper studies. Detections arefound at every flux level, showing that HI absorption detections are not biasedtoward brighter sources. The stacks of detections and non-detections reveal aclear dichotomy in the presence of HI, with the 27 detections showing anaverage peak {\tau} = 0.02, while the 66 non-detections remain undetected withan upper limit {\tau} < 0.002. Separating the sample into compact and extendedAGN increases the detection rate, {\tau}, and FWHM for the compact sample. Thedichotomy for the stacked profiles of detections and non-detections still holdsbetween these two groups. We argue that orientation effects connected to adisk-like distribution of HI can be partly responsible for the dichotomy,however some of our galaxies must be genuinely depleted of cold gas. A fractionof the compact sources are confirmed by previous studies as likely young radiosources. These show an even higher detection rate of 55%. Along with their highintegrated optical depth and wider profile, this reinforces the idea that youngradio AGN are particularly rich in atomic gas. Part of our motivation is toprobe for the presence of HI outflows. However, the stacked profiles do notreveal any significant blueshifted wing. Our results are particularly relevantfor future surveys. The lack of bias toward bright sources is encouraging forthe search of HI at lower radio fluxes. The results also represent a referencepoint for search for HI absorption at higher redshifts.

Probing the gas content of radio galaxies through HI absorption stacking