A Giant Metrewave Radio Telescope search for associated H i 21 cm absorption in GHz-peaked-spectrum sources

Aditya, J. N. H. S.; Kanekar, Nissim

doi:10.1093/mnras/stx2325

Cited by 44 publications

(52 citation statements)

References 65 publications

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“…Further, the absorption null extends up to ≈ 700 km s −1 on the blue side, implying that a significant fraction of the gas mass that has negative velocities, is also outflowing relative to the AGN. Curiously, the detection towards TXS 1245-197 at z = 1.275, reported recently by Aditya & Kanekar (2018a), has a similar looking blueshifted absorption wing, that extends up to ≈ −800 km s −1 . The absorption peak is also coincident with the AGN redshift, as in the current case.…”

Section: Resultssupporting

confidence: 64%

uGMRT detections of H i 21-cm absorption associated with intermediate redshift galaxies

Aditya

2018

Monthly Notices of the Royal Astronomical Society

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I report detections of four new Hi 21-cm absorbers associated with sources at intermediate redshifts, 0.7 < z < 1.0. The sources are part of a sample of 11 radio-loud galaxies, all at 0.7 < z < 1.0, that were searched for associated Hi 21-cm absorption using uGMRT. Previously, just four such absorbers were known in the literature at these redshifts; the current observations have increased the total to eight. The results indicate that the detection fraction at intermediate redshifts could be as high as that at lower redshifts, ≈ 30%, on contrary to a much lower detection fraction observed in samples at z > 1. Three detections show strong blueshifted features, indicating cold gas outflows. These three sources also tentatively show excess [O ii] line luminosity compared to a bulk of the remaining sample, possibly suggesting that the hosts of these AGNs harbour different environments, either due to interaction with the radio jets or due to excess star formation in the host galaxy. Further, a cold Hi mass outflow rate of ≈ 78 M ⊙ yr −1 , assuming T s = 1000 K, is estimated for the detection towards SDSS J014652.79-015721.2, at z = 0.95904, which is the highest till date in comparison to similar estimates available in the literature.

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Section: Resultssupporting

confidence: 64%

uGMRT detections of H i 21-cm absorption associated with intermediate redshift galaxies

Aditya

2018

Monthly Notices of the Royal Astronomical Society

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“…They suggest that a critical UV luminosity of L UV ∼ 10 23 W Hz −1 exists above which these effects occur. Interestingly, the GPS at redshift 1.275 where recently H I absorption was detected by Aditya et al (2018) has a high UV luminosity (> 10 23 ) as well as an H I outflow with properties similar to found for objects at low redshift. If the evidence for redshift evolution in the strength of associated H I absorption is confirmed, alternative effects should also be considered as discussed by Aditya et al (2016).…”

Section: Evolution With Redshift Effect Of Uv Radiationsupporting

confidence: 58%

“…This is expected given the small sizes of such radio sources and their dense ISM. Interestingly, the highest redshift outflow observed so far (from Aditya et al (2018), see Fig. 16) is also found in a GPS source.…”

Section: Occurrence Of Fast H I Outflowsmentioning

confidence: 63%

“…The few published studies of small samples of objects at high redshift use a variety of selection criteria for the targets. Observed targets include compact radio sources and GPS (Gupta et al 2006;Aditya et al 2018), radio quasars and flat spectrum sources (Curran et al 2008;Aditya et al 2016), and radio sources selected for their blue magnitude or optical faintness (Curran et al 2013b,c). The heterogeneity of the samples, and the limited number of objects, makes it particularly difficult to derive strong conclusions about the properties of H I absorption at z > 1.…”

Section: Evolution With Redshift Effect Of Uv Radiationmentioning

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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“…A number of cases have been found where a component of H I (identify by blueshifted wings seen in H I absorption) is associated with jet-driven outflows, see e.g. Morganti et al (2003Morganti et al ( , 2005a; Aditya & Kanekar (2018); Morganti & Oosterloo (2018) and refs therein.…”

Section: Jet-driven Outflows Of Cold Gas: Hi Componentmentioning

confidence: 99%

Radio jets: Properties, life and impact

Morganti

2019

Proc. IAU

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Our view of the properties of extragalactic radio jets and the impact they have on the host galaxy has expanded in the recent years. This has been possible thanks to the data from new or upgraded radio telescopes. This review briefly summarises the current status of the field and describes some of the exciting recent results and the surprises they have brought. In particular, the physical properties of radio jets as function of their radio power will be discussed together with the advance made in understanding the life-cycle of radio sources. The evolutionary stage (e.g. newly born, dying, restarted) of the radio AGN can be derived from their morphology and properties of the radio spectra. The possibilities offered by the new generation of low-frequency radio telescopes make it possible to derive (at least to first order) the time-scale spent in each phase. The presence of a cycle of activity ensures a recurrent impact of the radio jets on their surrounding inter-stellar and inter-galactic medium and, therefore, their relevance for AGN feedback. The last part is dedicated to the recent results showing the effect of jets on the surrounding galactic medium. The predictions made by numerical simulations on the impact of a radio jet (and in particular a newly born jet) on a clumpy medium describe well what is seen by the observations. The high resolution studies of jet-driven outflows of cold gas (and molecular) has provided new important addition both in term of quantifying the impact of the outflows and their relevance for feedback as well as for providing an unexpected view of the physical conditions of the gas under these extreme conditions.

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A Giant Metrewave Radio Telescope search for associated H i 21 cm absorption in GHz-peaked-spectrum sources

Cited by 44 publications

References 65 publications

uGMRT detections of H i 21-cm absorption associated with intermediate redshift galaxies

uGMRT detections of H i 21-cm absorption associated with intermediate redshift galaxies

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

Radio jets: Properties, life and impact

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