Feedback from low-luminosity radio galaxies: B2 0258+35

Tadhunter

et al. 2019

A&A

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We present CO(1-0) and CO(3-2) Atacama Large Millimeter/submillimeter Array observations of the molecular gas in PKS 1549−79, as well as mm and very long baseline interferometry 2.3-GHz continuum observations of its radio jet. PKS 1549−79 is one of the closest young, radio-loud quasars caught in an on-going merger in which the active galactic nucleus (AGN) is in the first phases of its evolution. We detect three structures tracing the accretion and the outflow of molecular gas: kpc-scale tails of gas accreting onto PKS 1549−79 from a merger, a circumnuclear disc in the inner few hundred parsec, and a very broad (>2300 km s −1 ) component detected in CO(1-0) at the position of the AGN. Thus, in PKS 1549−79 we see the co-existence of accretion and the ejection of gas. The line ratio CO(3-2)/CO(1-0) suggests that the gas in the circumnuclear-disc has both high densities and high kinetic temperatures. We estimate a mass outflow rate of at least 650 M yr −1 . This massive outflow is confined to the inner region (r < 120 pc) of the galaxy, which suggests that the AGN drives the outflow. Considering the amount of molecular gas available in the central nuclear disc and the observed outflow rate, we estimate a time scale of ∼10 5 yr over which the AGN would be able to destroy the circumnuclear disc, although gas from the merger may come in from larger radii, rebuilding this disc at the same time. The AGN appears to self-regulate gas accretion to the centre and onto the super-massive black hole. Surprisingly, from a comparison with Hubble Space Telescope data, we find that the ionised gas outflow is more extended. Nevertheless, the warm outflow is about two orders of magnitude less massive than the molecular outflow. PKS 1549−79 does not seem to follow the scaling relation between bolometric luminosity and the relative importance of warm ionised and molecular outflows claimed to exist for other AGN. We argue that, although PKS 1549−79 hosts a powerful quasar nucleus and an ultra-fast outflow, the radio jet plays a significant role in producing the outflow, which creates a cocoon of disturbed gas that expands into the circumnuclear disc.

Section: Possible Scenarios For the Outflowmentioning

confidence: 82%

ALMA observations of PKS 1549–79: a case of feeding and feedback in a young radio quasar

Oosterloo

Tadhunter

et al. 2019

A&A

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“…This is also confirmed by detailed studies of single, radio-quiet objects e.g. Seyfert galaxies like NGC 1068, IC 5063, Mrk 6 (see García-Burillo et al 2014;Morganti et al 2015;Kharb et al 2014, and refs therein) and LLAGN (Alatalo et al 2011;Combes et al 2013;Riffel et al 2014;Rodríguez-Ardila et al 2017;Fabbiano et al 2018;Maksym et al 2019;Murthy et al 2019;Husemann et al 2019a). Thus, the radio jets observed in these objects, despite their low power, can have an impact on the surrounding gas, disturb the kinematics and, in some cases, influence the physical properties (e.g.…”

Section: Jets As Function Of the Radio Powermentioning

confidence: 65%

Radio jets: Properties, life and impact

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.

“…A relatively small fraction of the outflowing gas may actually Giroletti et al (2005). Right: H I absorption profile (green) from VLA observations with superposed (red) the model from the H I disc observed in emission in this object by Struve et al (2010) and in blue the model adding a component of turbulence due to the interaction of the jet with the H I in the disk (Murthy et al 2019).…”

Section: Discussionmentioning

confidence: 99%

“…The width of the absorption (∼ 400 km s −1 ) is too large to be explained by the rotation of the large scale H I disk known to be present in this object. The most likely hypothesis is that the jet enters the disk and, being trapped there, disturbs the kinematics of the gas without being able to produce a fast outflow, but injects energy increases the turbulence of the gas (Murthy et al 2019). As already suggested for the low-power radio source NGC 1266 (Alatalo et al 2015), jet-induced turbulence may play a role in preventing star formation despite the large reservoir of cold gas observed in these objects.…”

Section: Do the Low Power Jets Have Also An Impact?mentioning

confidence: 91%

The parsec-scale structure of jet-driven H I out ows in radio galaxies

Schulz²,

Nyland

et al. 2018

Proc. IAU

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Radio jets can play multiple roles in the feedback loop by regulating the accretion of the gas, by enhancing gas turbulence, and by driving gas outflows. Numerical simulations are beginning to make detailed predictions about these processes. Using high resolution VLBI observations we test these predictions by studying how radio jets of different power and in different phases of evolution affect the properties and kinematics of the surrounding H I gas. Consistent with predictions, we find that young (or recently restarted) radio jets have stronger impact as shown by the presence of H I outflows. The outflowing medium is clumpy with clouds of with sizes up to a few tens of pc and mass ∼ 10 4 M ) already in the region close to the nucleus (< 100 pc), making the jet interact strongly and shock the surrounding gas. We present a case of a low-power jet where, as suggested by the simulations, the injection of energy may produce an increase in the turbulence of the medium instead of an outflow.