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/

Zendy Plus

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

Zendy Tools

Zendy Open

We report the discovery of two remarkable high-opacity HI 21cm absorbersagainst low-luminosity active galactic nuclei (AGNs), at $z = 1.2166$ towardsJ0229+0044 and at $z=1.1630$ towards J0229+0053. The absorbers were detected inan unbiased Giant Metrewave Radio Telescope survey for HI 21cm absorptionagainst radio sources in the DEEP2 survey fields, covering $z \approx0.73-1.53$, and including sources without known redshifts. Thevelocity-integrated HI 21cm optical depths are $(74.2 \pm 7.8)$ km s$^{-1}$(J0229+0044) and $(78.41 \pm 0.81)$ km s$^{-1}$ (J0229+0053), higher than thatof any known redshifted HI 21cm absorber at $z > 0.12$, and implying high H{\sci} column densities, $> 10^{22}$ cm$^{-2}$. The emission redshift of J0229+0044is consistent with the HI 21cm absorption redshift, while the strength andvelocity spread of the absorption against J0229+0053 suggest that it too arisesfrom gas in the AGN environment: both absorbers are thus likely to be"associated" systems. The two AGNs have low rest-frame 1.4 GHz radio and 1215Angstrom ultraviolet luminosities ($\lesssim 10^{26.1}$ W Hz$^{-1}$ and$\lesssim 10^{21.7}$ W Hz$^{-1}$, respectively), both significantly lower thanthe typical luminosities of AGNs against which HI 21cm searches have hithertobeen carried out at $z \gtrsim 1$. The paucity of HI 21cm absorbers at $z\gtrsim 1$ may be due to a luminosity bias in high-$z$ AGN samples that havebeen searched for HI 21cm absorption, where the high AGN ultraviolet luminosityaffects physical conditions in its environment, ionizing the neutral hydrogen.

Giant Metrewave Radio Telescope detections of two high-opacity HI 21cm absorbers at $z \approx 1.2$