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Register a new userThe MURALES survey. IV. Searching for nuclear outflows in 3C radio galaxies at z < 0.3 with MUSE observations
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We analyze VLT/MUSE observations of 37 radio galaxies from the Third Cambridge catalogue (3C) with redshift $<$0.3 searching for nuclear outflows of ionized gas. These observations are part of the MURALES project (a MUse RAdio Loud Emission line Snapshot survey), whose main goal is to explore the feedback process in the most powerful radio-loud AGN. We applied a nonparametric analysis to the [O~III] $lambda$5007 emission line, whose asymmetries and high-velocity wings reveal signatures of outflows. We find evidence of nuclear outflows in 21 sources, with velocities between $sim$400 - 1000 km s$^{-1}$, outflowing masses of $sim 10^5-10^7$ M$_odot$, and a kinetic energy in the range $sim 10^{53} - 10^{56}$ erg. In addition, evidence for extended outflows is found in the 2D gas velocity maps of 13 sources of the subclasses of high-excitation (HEG) and broad-line (BLO) radio galaxies, with sizes between 0.4 and 20 kpc. We estimate a mass outflow rate in the range 0.4 - 30 M$_odot$ yr$^{-1}$ and an energy deposition rate of ${dot E}_{kin} sim 10^{42}-10^{45} $ erg s$^{-1}$. Comparing the jet power, the nuclear luminosity of the active galactic nucleus, and the outflow kinetic energy rate, we find that outflows of HEGs and BLOs are likely radiatively powered, while jets likely only play a dominant role in galaxies with low excitation. The low loading factors we measured suggest that these outflows are driven by momentum and not by energy. Based on the gas masses, velocities, and energetics involved, we conclude that the observed ionized outflows have a limited effect on the gas content or the star formation in the host. In order to obtain a complete view of the feedback process, observations exploring the complex multiphase structure of outflows are required.
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We present the final observations of a complete sample of 37 radio galaxies from the Third Cambridge Catalog (3C) with redshift <0.3 and declination <20 degrees obtained with the VLT/MUSE optical integral field spectrograph. These data were obtained as part of the MURALES survey (a MUse RAdio Loud Emission line Snapshot survey) with the main goal of exploring the AGN feedback process in the most powerful radio sources. We present the data analysis and, for each source, the resulting emission line images and the 2D gas velocity field. Thanks to such an unprecedented depth these observations reveal emission line regions (ELRs) extending several tens of kiloparsec in most objects. The gas velocity shows ordered rotation in 25 galaxies, but in several sources it is highly complex. We find that the 3C sources show a connection between radio morphology and emission line properties. In the ten FRI sources the line emission region is generally compact, only a few kpc in size, and only in one case it exceeds the size of the host. Conversely, all but two of the FRII galaxies show large-scale structures of ionized gas. The median extent is 16 kpc with the maximum reaching a size of ~80 kpc. There are no apparent differences in extent or strength between the ELR properties of the FRII sources of high and low gas excitation. We confirm that the previous optical identification of 3C258 is incorrect: this radio source is likely associated with a QSO at z~ 1.54.
We present observations of a complete sub-sample of 20 radio galaxies from the Third Cambridge Catalog (3C) with redshift <0.3 obtained from VLT/MUSE optical integral field spectrograph. These data have been obtained as part of the survey MURALES (a MUse RAdio Loud Emission line Snapshot survey) with the main goal of exploring the Active Galactic Nuclei (AGN) feedback process in a sizeable sample of the most powerful radio sources at low redshift. We present the data analysis and, for each source, the resulting emission line images and the 2D gas velocity field. Thanks to their unprecedented depth (the median 3 sigma surface brightness limit in the emission line maps is 6X10^-18 erg s-1 cm-2 arcsec-2, these observations reveal emission line structures extending to several tens of kiloparsec in most objects. In nine sources the gas velocity shows ordered rotation, but in the other cases it is highly complex. 3C sources show a connection between radio morphology and emission line properties. Whereas, in three of the four Fanaroff and Riley Class I radio galaxies (FRIs), the line emission regions are compact, ~1 kpc in size; in all but one of the Class II radiogalaxies FRIIs, we detected large scale structures of ionized gas with a median extent of 17 kpc. Among the FRIIs, those of high and low excitation show extended gas structures with similar morphological properties, suggesting that they both inhabit regions characterized by a rich gaseous environment on kpc scale.
We report on the second round of Chandra observations of the 3C snapshot survey developed to observe the complete sample of 3C radio sources with z<0.3 for 8 ksec each. In the first paper, we illustrated the basic data reduction and analysis procedures performed for the 30 sources of the 3C sample observed during the Chandra Cycle 9, while here, we present the data for the remaining 27 sources observed during Cycle 12. We measured the X-ray intensity of the nuclei and of any radio hotspots and jet features with associated X-ray emission. X-ray fluxes in three energy bands: soft, medium and hard for all the sources analyzed are also reported. For the stronger nuclei, we also applied the standard spectral analysis which provides the best fit values of X-ray spectral index and absorbing column density. In addition, a detailed analysis of bright X-ray nuclei that could be affected by pileup has been performed. X-ray emission was detected for all the nuclei of the radio sources in our sample except for 3C 319. Amongst the current sample, there are two compact steep spectrum radio sources; two broad line radio galaxies; and one wide angle tail radio galaxy, 3C 89, hosted in a cluster of galaxies clearly visible in our Chandra snapshot observation. In addition, we also detected soft X-ray emission arising from the galaxy cluster surrounding 3C 196.1. Finally, X-ray emission from hotspots have been found in three FR II radio sources and, in the case of 3C 459, we also report the detection of X-ray emission associated with the eastern radio lobe and as well as that cospatial with radio jets in 3C 29 and 3C 402.
AGN-driven outflows are believed to play an important role in regulating the growth of galaxies mostly via negative feedback. However, their effects on their hosts are far from clear, especially for low and moderate luminosity Seyferts. To investigate this issue, we have obtained cold molecular gas observations, traced by the CO(2-1) transition, using the NOEMA interferometer of five nearby (distances between 19 and 58 Mpc) Seyfert galaxies. The resolution of approx. 0.3-0.8 arcsec (approx. 30-100 pc) and field of view of NOEMA allowed us to study the CO(2-1) morphology and kinematics in the nuclear regions (approx. 100 pc) and up to radial distances of approx. 900 pc. We have detected CO(2-1) emission in all five galaxies with disky or circumnuclear ring like morphologies. We derived cold molecular gas masses on nuclear (approx. 100 pc) and circumnuclear (approx. 650 pc) scales in the range from $10^6$ to $10^7$M$_{odot}$ and from $10^7$ to $10^8$ $M_{odot}$, respectively. In all of our galaxies the bulk of this gas is rotating in the plane of the galaxy. However, non-circular motions are also present. In NGC 4253, NGC 4388 and NGC 7465, we can ascribe the streaming motions to the presence of a large-scale bar. In Mrk 1066 and NGC 4388, the non-circular motions in the nuclear regions are explained as outflowing material due to the interaction of the AGN wind with molecular gas in the galaxy disk. We conclude that for an unambiguous and precise interpretation of the kinematics of the cold molecular gas we need a detailed knowledge of the host galaxy (i.e., presence of bars, interactions, etc) as well as of the ionized gas kinematics and the ionization cone geometry.
We report on our Chandra Cycle 9 program to observe half of the 60 (unobserved by Chandra) 3C radio sources at z<0.3 for 8 ksec each. Here we give the basic data: the X-ray intensity of the nuclei and any features associated with radio structures such as hot spots and knots in jets. We have measured fluxes in soft, medium and hard bands and are thus able to isolate sources with significant intrinsic column density. For the stronger nuclei, we have applied the standard spectral analysis which provides the best fit values of X-ray spectral index and column density. We find evidence for intrinsic absorption exceeding a column density of 10^{22} cm^{-2} for one third of our sources.
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