Radio AGNs with intermediate radio powers are capable of driving multi-phase outflows in galaxy bulges, and are also more common than their high-radio-power counterparts. In-depth characterisation of ...the typical host galaxies and likely triggering mechanisms for this population is therefore required in order to better understand the role of radio AGN feedback in galaxy evolution. Here, we use deep optical imaging data to study the detailed host morphologies of a complete sample of 30 local radio AGNs with high-excitation optical emission (HERG) spectra and intermediate radio powers (z \(<\) 0.1; 22.5 \(<\) log(L\(_{\rm 1.4GHz}\)) \(<\) 24.0 WHz\(^{-1}\)). The fraction of hosts with morphological signatures of mergers and interactions is greatly reduced compared to the 2 Jy radio-powerful galaxies (log(L\(_{\rm 1.4GHz}\)) \(>\) 25.0 WHz\(^{-1}\)) with strong optical emission lines: 53 \(\pm\) 9 per cent and 94 \(\pm\) 4 per cent, respectively. In addition, the most radio-powerful half of the sample has a higher frequency of morphological disturbance than the least radio-powerful half (67 \(\pm\) 12 per cent and 40 \(\pm\) 13 per cent, respectively), including the eight most highly-disturbed galaxies. This suggests that the importance of triggering nuclear activity in HERGs through mergers and interactions reduces with radio power. Both visual inspection and detailed light profile modelling reveal a mixed population of early-type and late-type morphologies, contrary to the massive elliptical galaxy hosts of radio-powerful AGNs. The prevalence of late-type hosts could suggest that triggering via secular, disk-based processes has increased importance for HERGs with lower radio powers (e.g. disk instabilities, large scale bars).
We present near-infrared integral field spectroscopy data obtained with VLT/SINFONI of "the Teacup galaxy". The nuclear K-band (1.95-2.45 micron) spectrum of this radio-quiet type-2 quasar reveals a ...blueshifted broad component of FWHM~1600-1800 km/s in the hydrogen recombination lines (Pa\(\alpha\), Br\(\delta\), and Br\(\gamma\)) and also in the coronal line Si VI\(\lambda\)1.963 micron. Thus the data confirm the presence of the nuclear ionized outflow previously detected in the optical and reveal its coronal counterpart. Both the ionized and coronal nuclear outflows are resolved, with seeing-deconvolved full widths at half maximum of 1.1\(\pm\)0.1 and 0.9\(\pm\)0.1 kpc along PA\(\sim\)72-74 deg. This orientation is almost coincident with the radio axis (PA=77 deg), suggesting that the radio jet could have triggered the nuclear outflow. In the case of the H\(_2\) lines we do not require a broad component to reproduce the profiles, but the narrow lines are blueshifted by ~50 km/s on average from the galaxy systemic velocity. This could be an indication of the presence of a nuclear molecular outflow, although the bulk of the H\(_2\) emission in the inner ~2 arcsec (~3 kpc) of the galaxy follows a rotation pattern. We find evidence for kinematically disrupted gas (FWHM>250 km/s) at up to 5.6 kpc from the AGN, which can be naturally explained by the action of the outflow. The narrow component of Si VI is redshifted with respect to the systemic velocity, unlike any other emission line in the K-band spectrum. This indicates that the region where the coronal lines are produced is not co-spatial with the narrow line region.
Despite the emerging morphological evidence that luminous quasar-like AGN are triggered in galaxy mergers, the natures of the triggering mergers and the order of events in the triggering sequence ...remain uncertain. In this work, we present a detailed study of the stellar populations of the host galaxies of 21 type II quasars, with the aim of understanding the sequence of events between the onset of the merger, the triggering of the associated starburst and the initiation of the quasar activity. To this end, we model high quality, wide spectral coverage, intermediate resolution optical spectra of the type II quasars. We find that of the 21 objects, the higher-order Balmer absorption lines, characteristic of young stellar populations (YSP) , are directly detected in ~62% of the sample. We also fit these spectra using a number of combinations of stellar and/or power-law components, representative of viable formation histories, as well as including the possibility of scattered AGN light. We find that 90 % of the type II quasar host galaxies require the inclusion of a YSP to adequately model their spectra, whilst 71 % of the sample require the inclusion of a YSP with age < 100 Myr. Since the ages of the YSP in most type II quasar host galaxies are comparable with the expected lifetimes of the AGN activity, these results provide strong evidence that the quasars are triggered close to the peaks of the merger-induced starbursts.
We report the discovery of a radio quiet type 2 quasar (SDSS J165315.06+234943.0 nicknamed the "Beetle" at z=0.103) with unambiguous evidence for active galactic nucleus (AGN) radio induced feedback ...acting across a total extension of ~46 kpc and up to ~26 kpc from the AGN. To the best of our knowledge, this is the first radio quiet system where radio induced feedback has been securely identified at >>several kpc from the AGN. Turbulent gas is also found far from the radio axis, ~25 kpc in the perpendicular direction. We propose a scenario in which the radio structures have perforated the interstellar medium of the galaxy and escaped into the circumgalactic medium. While advancing, they have interacted with in-situ gas modifying its properties. Our results show that jets of modest power can be the dominant feedback mechanism acting across huge volumes in radio quiet systems, including highly accreting luminous AGN, where radiative mode feedback may be expected.
We investigate the presence of extended ionized outflows in 18 luminous type 2 AGNs (11 quasars and 7 high luminosity Seyfert 2s) at 0.3<z<0.6 based on VLT-FORS2 spectroscopy. We infer typical lower ...limits on the radial sizes of the outflows R>=severalx100 pc and upper limits R<1-2 kpc. Our results are inconsistent with related studies which suggest that large scale R~several-15 kpc are ubiquitous in QSO2. We study the possible causes of discrepancy and propose that seeing smearing is the cause of the large inferred sizes. The implications in our understanding of the feedback phenomenon are important since the mass M (through the density), mass injection M(dot) and energy injection rates E(dot) of the outflows become highly uncertain. One conclusion seems unavoidable: M, M(dot), E(dot) are modest or low compared with previous estimations. No evidence is found supporting that typical outflows can affect the interstellar medium of the host galaxies accross spatial scales >~1-2 kpc.
Fast outflows of gas, driven by the interaction between the radio-jets and ISM of the host galaxy, are being observed in an increasing number of galaxies. One such example is the nearby radio galaxy ...3C293. In this paper we present Integral Field Unit (IFU) observations taken with OASIS on the William Herschel Telescope (WHT), enabling us to map the spatial extent of the ionised gas outflows across the central regions of the galaxy. The jet-driven outflow in 3C293 is detected along the inner radio lobes with a mass outflow rate ranging from \(\sim 0.05-0.17\) solar masses/yr (in ionised gas) and corresponding kinetic power of \(\sim 0.5-3.5\times 10^{40}\) erg/s. Investigating the kinematics of the gas surrounding the radio jets (i.e. not directly associated with the outflow), we find line-widths broader than \(300\) km/s up to 5 kpc in the radial direction from the nucleus (corresponding to 3.5 kpc in the direction perpendicular to the radio axis at maximum extent). Along the axis of the radio jet line-widths \(>400\) km/s are detected out to 7 kpc from the nucleus and line-widths of \(>500\) km/s at a distance of 12 kpc from the nucleus, indicating that the disturbed kinematics clearly extend well beyond the high surface brightness radio structures of the jets. This is suggestive of the cocoon structure seen in simulations of jet-ISM interaction and implies that the radio jets are capable of disturbing the gas throughout the central regions of the host galaxy in all directions.
We present deep, intermediate resolution, long slit Gemini GMOS-S optical spectra of the SDSS type II quasar J002531-104022, which is a highly disturbed system currently undergoing a major merger ...event. We use these data to model the ages and reddenings of the stellar populations in three distinct spatial regions and find a remarkable uniformity in the properties of the young stellar populations (YSP) that dominate the optical spectra. The YSPs are all found to have relatively young ages (tysp < 40$ Myr), strongly implying that the latest episode of star formation and quasar activity have been triggered quasi-simultaneously. The lack of reddening deduced from both continuum modelling and the measured Balmer decrements (E(B-V) <0.3) suggests that starburst and/or AGN induced outflows have already effectively removed a substantial proportion of the gas and dust from the central region. These findings starkly contrast with model predictions which suggest an offset of a few 100 Myr between the peak of merger induced star formation and the emergence of the optically visible quasar activity. Based on our stellar population fits we also show that the total stellar mass is in the range (4 - 17) X 10^10 solar masses, lower than typically found for quasar host galaxies.
We present deep Gemini GMOS-S optical broad-band images for a complete sample of 20 SDSS selected type II quasars with redshifts 0.3 < z < 0.41 and OIII emission line luminosities greater than 10^8.5 ...solar luminosities. We use these images to determine the significance of galaxy interactions in triggering nuclear activity, finding that 15 (75%) show evidence for interaction in the form of tails, shells, double nuclei etc. The median surface brightness of the features is 23.4 mag arcsec sq and the range is 20.9-24.7 mag arcsec sq. We find a similar rate of interaction in the type II quasars as in a comparison sample of quiescent early-type galaxies at similar redshift (67 +/- 14%). However the surface brightness of the detected features is up to 2 magnitudes brighter for the type II quasars than for the quiescent early-types, which have surface brightnesses in the range 22.1-26.1 mag arcsec sq and a median surface brightness 24.3 mag arcsec sq. This may indicate that the mergers witnessed in the comparison sample galaxies could have different progenitors, or we may be viewing the interactions at different stages. We also compare our results with a sample of radio-loud AGN and find a higher rate of interaction signatures (95 +/- 21%) than in the type II quasars, but a very similar range of surface brightnesses for the morphological features (20.9-24.8 mag arcsec sq), possibly indicating a similarity in the types of triggering interactions. The range of features detected in the type II quasars suggests that AGN activity can be triggered before, during or after the coalescence of the black holes. Overall, our results are consistent with the idea that galaxy interaction plays an important role in the triggering of quasar activity.
We present a compilation of HST images of 58 luminous SDSS type 2 AGNs at 0.3<z<0.4. 42 of them are type 2 quasars, which are a good representation of all optically selected SDSS type 2 quasars in ...this range. We find that the majority of the host galaxies are ellipticals (30/42 or 71%). This is consistent with studies of radio loud and radio quiet type 1 quasars which show that their host galaxies are in general ellipticals. A significant fraction of type 2 quasars (>25/42 or >59%) show clear signatures of morphological disturbance which are in most cases identified with merger/interaction processes. We discuss this in the context of related works on type 2 quasars and powerful radio galaxies. We study in detail the particular case of the radio quiet type 2 quasar SDSS J143027.66-005614.8 at z=0.32 based on VLT, HST and SDSS imaging and spectroscopic data. We discuss the global properties of the object in the context of theoretical and observational studies of galaxy mergers/interactions and their role in the triggering of the nuclear and star formation activities in the most luminous active galaxies.
Global constraints are an essential component in the efficiency of centralized constraint programming. We propose to include global constraints in distributed constraint satisfaction problem (DisCSP) ...and distributed constraint optimization problem (DCOP). We detail how this inclusion can be done, considering different representations for global constraints (direct, nested, binary). We explore the relation of global constraints with local consistency (both in the hard and soft cases), in particular, for generalized arc consistency (GAC). We provide experimental evidence of the benefits of global constraints on several benchmarks, both for distributed constraint satisfaction and for distributed constraint optimization.
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