HI 21cm and OH 18cm absorption search with the GBT

DOI

We present the results of a large search for intrinsic HI 21cm and OH 18cm absorption in 145 compact radio sources in the redshift range 0.02<z<3.8 with the Green Bank Telescope. We redetect HI 21cm absorption toward six known absorption systems, but detect no new HI or OH absorption in 102 interference-free sources. Seventy-nine sources have not previously been observed for HI 21cm absorption. We recover a mean optical depth limit of {tau}3{sigma}<0.023 for all the nondetections in the survey. Our results do not support the high intrinsic absorption rates found by previous studies in compact radio sources at low redshift. Our results do, however, support the hypothesis proposed by Curran+ (2019MNRAS.484.1182C) that high ultraviolet (UV) luminosity active galactic nuclei do not show intrinsic HI 21cm absorption, confirming a threshold of L_UV_=10^23^W/Hz, above which our intrinsic absorption fraction is zero (54 sources). The exact nature of the UV luminosity effect on HI absorption systems remains ambiguous. We additionally find no statistical correlation between the 1.4GHz radio luminosity or the source size and the 21cm absorption detection rate. We attribute the lack of intrinsic absorption in our survey to the UV luminosity effect caused by an optical selection bias and a decreased column density sensitivity with increasing redshift due to lower radio continuum flux densities, high radio frequency interference, and higher telescope system temperatures at low frequencies.

Cone search capability for table J/ApJS/245/3/table1 (Observations of intrinsic HI and OH lines toward compact radio sources)

Identifier
DOI http://doi.org/10.26093/cds/vizier.22450003
Source https://dc.g-vo.org/rr/q/lp/custom/CDS.VizieR/J/ApJS/245/3
Related Identifier https://cdsarc.cds.unistra.fr/viz-bin/cat/J/ApJS/245/3
Related Identifier http://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/ApJS/245/3
Metadata Access http://dc.g-vo.org/rr/q/pmh/pubreg.xml?verb=GetRecord&metadataPrefix=oai_b2find&identifier=ivo://CDS.VizieR/J/ApJS/245/3
Provenance
Creator Grasha K.; Darling J.; Bolatto A.; Leroy A.K.; Stocke J.T.
Publisher CDS
Publication Year 2020
Rights https://cds.unistra.fr/vizier-org/licences_vizier.html
OpenAccess true
Contact CDS support team <cds-question(at)unistra.fr>
Representation
Resource Type Dataset; AstroObjects
Discipline Astrophysics and Astronomy; Cosmology; Galactic and extragalactic Astronomy; High Energy Astrophysics; Interstellar medium; Natural Sciences; Observational Astronomy; Physics