The 'shook up' galaxy NGC 3079 : the complex interplay between H I, activity and environment

We present deep neutral hydrogen (H i) observations of the starburst/Seyfert galaxy NGC 3079 and its environment, obtained with the Westerbork Synthesis Radio Telescope. Our observations reveal previously unknown components, both in Hi emission and in absorption, that show that NGC 3079 is going through a hectic phase in its evolution. The Hi disk appears much more extended than previously observed and is morphologically and kinematically lopsided on all scales with evidence for strong non-circular motions in the central regions. Our data reveal prominent gas streams encircling the entire galaxy suggesting strong interaction with its neighbours. A 33-kpc long Hi bridge is detected between NGC 3079 and MCG 9-17- 9, likely caused by ram-pressure stripping of MGC 9-17-9 by the halo of hot gas of NGC 3079. The cometary Hi tail of the companion NGC 3073, earlier discovered by Irwin et al., extends about twice as long in our data, while a shorter, second tail is also found. This tail is likely caused by ram-pressure stripping by the strong, starburst driven wind coming from NGC 3079. We also detect, in absorption, a nuclear Hi outflow extending to velocities well outside what expected for gravitational motion. This is likely an atomic counterpart of the well-studied outflow of ionised gas present in this galaxy. This may indicate that also large amounts of cold gas are blown out of NGC 3079 by the starburst/AGN. Our estimates of the jet energy and kinetic power suggest that both the AGN and the starburst in NGC 3079 are powerful enough to drive the atomic outflow.The WSRT is operated by ASTRON, the Netherlands Institute for Radio Astronomy, with the support from the Netherlands Foundation for Scientific Research (NWO). N.S. acknowledges support by the Square Kilometre Array (SKA) and the Hartebeesthoek Radio Astronomy Observatory (HartRAO). S.C. acknowledges support by the South African Research Chairs Initiative of the Department of Science and Technology and National Research Foundation and SKA. R.M. gratefully acknowledge support from the European Research Council under the European Union’s Seventh Framework Programme (FP/2007-2013)/ERC Advanced Grant RADIOLIFE- 320745.http://mnras.oxfordjournals.orgam201

Probing multi-phase outflows and AGN feedback in compact radio galaxies: the case of PKSB 1934-63

Young radio AGN are pivotal for our understanding of many of the still-debated aspects of AGN feedback. In this paper we present a study of the interstellar medium (ISM) in the compact, peaked-spectrum radio galaxy PKS B1934-63 using X-shooter observations. Most of the warm ionized gas resides within a circum-nuclear disk with a radius of about 200 pc that is likely to constitute the gas reservoir from which the central black hole feeds. On the other hand, we find a biconical outflow of warm ionized gas with an estimated radius of 59±12 pc. This matches the radial extent of the radio source and suggests that the outflow is jet driven. Thanks to the superior wavelength coverage of the data, we can estimate the density of the warm ionized gas using the trans-auroral line technique, and we find that the outflowing gas has remarkably high density, up to logne (cm−3) ' 5.5. The estimated mass outflow rate is low ( ˙ M =10−3-10−1 Mo yr−1), and the AGN feedback operates at relatively low efficiency ( ˙ E/Lbol ∼10−4-10−3%). In addition,optical and near-IR line ratios show that the expansion of the radio source drives fast shocks (with velocities vs & 500 kms−1) that ionize and accelerate the outflowing gas. Atoddswiththepropertiesofothercompact,peaked-spectrumradiosourceshostingwarmionizedgasoutflows,wedonotfindsigns ofkinematicallydisturbedoroutflowinggasinphasescolderthanthewarmionizedgas.Wearguethatthisisduetotheyoungageof our source and thus to the recent nature of the AGN-ISM interaction, and suggest that cold gas forms within the outflowing material and the shock-ionized outflowing gas of PKS B1934-63 did not have enough time to cool down and accumulate in a colder phase. This scenario is also supported by the multi-phase outflows of other compact and young radio sources in the literature

Large-scale H I in nearby radio galaxies - II. The nature of classical low-power radio sources

An important aspect of solving the long-standing question as to what triggers various types of active galactic nuclei (AGN) involves a thorough understanding of the overall properties and formation history of their host galaxies. This is the second in a series of papers that systematically study the large-scale properties of cold neutral hydrogen (H I) gas in nearby radio galaxies. The main goal is to investigate the importance of gas-rich galaxy mergers and interactions among radio-loud AGN. In this paper, we present results of a complete sample of classical low-power radio galaxies. We find that extended Fanaroff & Riley type-I radio sources are generally not associated with gas-rich galaxy mergers or ongoing violent interactions, but occur in early-type galaxies without large (>rsim 108 M⊙) amounts of extended neutral hydrogen gas. In contrast, enormous discs/rings of H I gas (with sizes up to 190 kpc and masses up to 2 × 1010 M⊙) are detected around the host galaxies of a significant fraction of the compact radio sources in our sample. This segregation in H I mass with radio-source size likely indicates that either these compact radio sources are confined by large amounts of gas in the central region or that their fuelling is inefficient and different from the fuelling process of classical FR I radio sources. To first order, the overall H I properties of our complete sample (detection rate, mass and morphology) appear similar to those of radio-quiet early-type galaxies. If confirmed by better statistics, this would imply that low-power radio-AGN activity may be a short and recurrent phase that occurs at some point during the lifetime of many early-type galaxies

The ATLAS3D project - XXVI : H I discs in real and simulated fast and slow rotators

One quarter of all nearby early-type galaxies (ETGs) outside Virgo host a disc/ring of H I with size from a few to tens of kpc and mass up to ∼109 M⊙. Here we investigate whether this H I is related to the presence of a stellar disc within the host making use of the classification of ETGs in fast and slow rotators (FR/SR). We find a large diversity of H I masses and morphologies within both families. Surprisingly, SRs are detected as often, host as much H I and have a similar rate of H I discs/rings as FRs. Accretion of H I is therefore not always linked to the growth of an inner stellar disc. The weak relation between H I and stellar disc is confirmed by their frequent kinematical misalignment in FRs, including cases of polar and counterrotating gas. In SRs the H I is usually polar. This complex picture highlights a diversity of ETG formation histories which may be lost in the relative simplicity of their inner structure and emerges when studying their outer regions. We find that Λ CDM hydrodynamical simulations have difficulties reproducing the H I properties of ETGs. The gas discs formed in simulations are either too massive or too small depending on the star formation feedback implementation. Kinematical misalignments match the observations only qualitatively. The main point of conflict is that nearly all simulated FRs and a large fraction of all simulated SRs host corotating H I. This establishes the H I properties of ETGs as a novel challenge to simulationsPeer reviewedFinal Accepted Versio

The MeerKAT Fornax Survey

We present the science case and observations plan of the MeerKAT Fornax Survey, an HI and radio continuum survey of the Fornax galaxy cluster to be carried out with the SKA precursor MeerKAT. Fornax is the second most massive cluster within 20 Mpc and the largest nearby cluster in the southern hemisphere. Its low X-ray luminosity makes it representative of the environment where most galaxies live and where substantial galaxy evolution takes place. Fornax's ongoing growth makes it an excellent laboratory for studying the assembly of clusters, the physics of gas accretion and stripping in galaxies falling in the cluster, and the connection between these processes and the neutral medium in the cosmic web. We will observe a region of 12 deg2 reaching a projected distance of 1.5 Mpc from the cluster centre. This will cover a wide range of environment density out to the outskirts of the cluster, where gas-rich in-falling groups are found. We will: study the HI morphology of resolved galaxies down to a column density of a few times 1e+19 cm−2 at a resolution of 1 kpc; measure the slope of the HI mass function down to M(HI) 5e+5 M(sun); and attempt to detect HI in the cosmic web reaching a column density of 1e+18 cm−2 at a resolution of 10 kpc

AGN feeding and feedback in fornax a : kinematical analysis of the multi-phase ISM

We present a multi-wavelength study of the gaseous medium surrounding the nearby active galactic nucleus (AGN), Fornax A. Using MeerKAT, ALMA, and MUSE observations, we reveal a complex distribution of the atomic (H i), molecular (CO), and ionised gas in its centre and along the radio jets. By studying the multi-scale kinematics of the multi-phase gas, we reveal the presence of concurrent AGN feeding and feedback phenomena. Several clouds and an extended 3 kpc filament – perpendicular to the radio jets and the inner disk (r . 4:5 kpc) – show highly-turbulent kinematics, which likely induces non-linear condensation and subsequent chaotic cold accretion (CCA) onto the AGN. In the wake of the radio jets and in an external (r & 4:5 kpc) ring, we identify an entrained massive ( 107 M ) multi-phase outflow (vOUT 2000 km s1). The rapid flickering of the nuclear activity of Fornax A ( 3 Myr) and the gas experiencing turbulent condensation raining onto the AGN provide quantitative evidence that a recurrent, tight feeding and feedback cycle may be self-regulating the activity of Fornax A, in agreement with CCA simulations. To date, this is one of the most in-depth probes of such a mechanism, paving the way to apply these precise diagnostics to a larger sample of nearby AGN hosts and their multi-phase inter stellar medium.The European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme; Montage is funded by the National Science Foundation; the Department of Science and Technology and National Research Foundation.http://www.hanspub.org/Journal/AAS.htmlam2022Physic

A bright, high rotation-measure FRB that skewers the M33 halo

We report the detection of a bright fast radio burst, FRB\,191108, with Apertif on the Westerbork Synthesis Radio Telescope (WSRT). The interferometer allows us to localise the FRB to a narrow 5\arcsec\times7\arcmin ellipse by employing both multibeam information within the Apertif phased-array feed (PAF) beam pattern, and across different tied-array beams. The resulting sight line passes close to Local Group galaxy M33, with an impact parameter of only 18\,kpc with respect to the core. It also traverses the much larger circumgalactic medium of M31, the Andromeda Galaxy. We find that the shared plasma of the Local Group galaxies could contribute $\sim$10\% of its dispersion measure of 588\,pc\,cm$^{-3}$. FRB\,191108 has a Faraday rotation measure of +474\,$\pm\,3$\,rad\,m$^{-2}$, which is too large to be explained by either the Milky Way or the intergalactic medium. Based on the more moderate RMs of other extragalactic sources that traverse the halo of M33, we conclude that the dense magnetised plasma resides in the host galaxy. The FRB exhibits frequency structure on two scales, one that is consistent with quenched Galactic scintillation and broader spectral structure with $\Delta\nu\approx40$\,MHz. If the latter is due to scattering in the shared M33/M31 CGM, our results constrain the Local Group plasma environment. We found no accompanying persistent radio sources in the Apertif imaging survey data