GMRT detection of HI 21 cm associated absorption towards thez = 1.2 red quasar 3C 190

Ishwara‐Chandra, C. H.; Dwarakanath, K. S.; Anantharamaiah, K. R.

doi:10.1007/bf03012190

Cited by 33 publications

(42 citation statements)

References 19 publications

(29 reference statements)

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“…These GPS sources are compact in linear extent and believed to be young or re-triggered in their AGN activity. We also find shallow and asymmetric Hi absorption features in our survey, as seen in Carilli et al (1998) and Ishwara-Chandra et al (2003) towards red quasars, and low redshift studies towards young radio AGN.…”

Section: Resultssupporting

confidence: 91%

An ASKAP survey for H i absorption towards dust-obscured quasars

Glowacki

Allison

Moss

et al. 2019

Monthly Notices of the Royal Astronomical Society

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Obscuration of quasars by accreted gas and dust, or dusty intervening galaxies, can cause active galactic nuclei (AGN) to be missed in optically-selected surveys. Radio observations can overcome this dust bias. In particular, radio surveys searching for Hi absorption inform us on how the AGN can impact on the cold neutral gas medium within the host galaxy, or the population of intervening galaxies through the observed line of sight gas kinematics. We present the results of a Hi absorption line survey at 0.4 < z < 1 towards 34 obscured quasars with the Australian SKA Pathfinder (ASKAP) commissioning array. We detect three Hi absorption lines, with one of these systems previously unknown. Through optical follow-up for two sources, we find that in all detections the Hi gas is associated with the AGN, and hence that these AGN are obscured by material within their host galaxies. Most of our sample are compact, and in addition, are either gigahertz peaked spectrum (GPS), or steep spectrum (CSS) sources, both thought to represent young or recently re-triggered radio AGN. The radio spectral energy distribution classifications for our sample agree with galaxy evolution models in which the obscured AGN has only recently become active. Our associated Hi detection rate for GPS and compact SS sources matches those of other surveys towards such sources. We also find shallow and asymmetric Hi absorption features, which agrees with previous findings that the cold neutral medium in compact radio galaxies is typically kinematically disturbed by the AGN.

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Section: Resultssupporting

confidence: 91%

An ASKAP survey for H i absorption towards dust-obscured quasars

Glowacki

Allison

Moss

et al. 2019

Monthly Notices of the Royal Astronomical Society

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“…Published studies have mostly used the GMRT and the GBT. In contrast to the over 150 detections at z ≤ 1, there are only 7 detections of associated H I 21-cm absorption above this redshift (Ishwara-Chandra et al 2003;Curran et al 2013c;Aditya et al 2017Aditya et al , 2018 and only two of those are at z > 2 (one of which is even a tentative detection; Uson et al 1991;Aditya et al 2016).…”

Section: Evolution With Redshift Effect Of Uv Radiationmentioning

confidence: 67%

“…Carilli et al 1998b;Yan et al 2016). In the red quasar 3C190, the detected H I absorption appears to be also broad (with a width of 600 km s −1 , Ishwara-Chandra et al 2003 suggesting an ongoing interaction between the jet and the ISM. This is not the only case where the quasars can still be embedded and interacting with a cocoon of gas perhaps originating from the event that has fuelled their central SMBH.…”

Section: Irregular H I Structuresmentioning

confidence: 99%

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The interstellar and circumnuclear medium of active nuclei traced by H i 21 cm absorption

Morganti

Oosterloo

2018

Astron Astrophys Rev

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This review summarises what we have learnt in the last two decades based on H I 21-cm absorption observations about the cold interstellar medium (ISM) in the central regions of active galaxies and about the interplay between this gas and the active nucleus (AGN). H I absorption is a powerful tracer on all scales, from the parsec-scales close to the central black hole to structures of many tens of kpc tracing interactions and mergers of galaxies. Given the strong radio continuum emission often associated with the central activity, H I absorption observations can be used to study the H I near an active nucleus out to much higher redshifts than is possible by using H I emission. In this way, H I absorption has been used to characterise in detail the general ISM in active galaxies, to trace the fuelling of radio-loud AGN, to study the feedback occurring between the energy released by the active nucleus and the ISM, and the impact of such interactions on the evolution of galaxies and of their AGN. In the last two decades, significant progress has been made in all these areas. It is now well established that many radio loud AGN are surrounded by small, regularly rotating gas disks that contain a significant fraction of H I. The structure of these disks has been traced down to parsec scales by VLBI observations. Some groups of objects, and in particular young and recently restarted radio galaxies, appear to have a particularly high detection rate of H I. This is interesting in connection with the evolution of these AGN and their impact on the surrounding ISM. This is further confirmed by an important discovery, made thanks to technical upgrades of radio telescopes, namely the presence of fast, AGN-driven outflows of cold gas which give a direct view of the impact of the energy released by AGN on the evolution of galaxies (AGN feedback). In addition, evidence has been collected that clouds of cold gas can play a role in fuelling the nuclear activity. This review ends by briefly describing the upcoming large, blind H I absorption surveys planned for the new radio telescopes which will soon become operational. These surveys will allow to significantly expand existing work, but will also allow to explore new topics, in particular the evolution of the cold ISM in AGN.

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“…References with the data used are given in square brackets. a The component with the poorest accuracy is taken from [21]. b Just one of components from [29] is considered.…”

Section: Numerical Resultsmentioning

confidence: 99%

Analysis of the absorption line profile at 21 cm for the hydrogen atom in the interstellar medium

Solovyev

2018

J. Phys. B: At. Mol. Opt. Phys.

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The paper analyzes the absorption line profile at 21 cm for the hydrogen atom in the interstellar medium. The hydrogen atom is treated as a three-level system illuminated by a powerful light source at neighboring resonances corresponding to the hyperfine splitting of the ground state and Ly α transition. The field acting upon the resonances gives rise to physical processes, which can be explained as interfering pathways between different transitions. The paper considers particular cases when the 21 cm line profile is substantially modified by the Ly α transition. A correction to the optical depth is introduced as a result of theory. It is shown that the correction can be considerable and should be taken into account when determining the column density of hydrogen atoms in the interstellar medium. The paper also deals with the effects of none-Doppler broadening and frequency shift.

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GMRT detection of HI 21 cm associated absorption towards thez = 1.2 red quasar 3C 190

Cited by 33 publications

References 19 publications

An ASKAP survey for H i absorption towards dust-obscured quasars

An ASKAP survey for H i absorption towards dust-obscured quasars

The interstellar and circumnuclear medium of active nuclei traced by H i 21 cm absorption

Analysis of the absorption line profile at 21 cm for the hydrogen atom in the interstellar medium

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