References of "Tacconi, L"
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See detailThe role of host galaxy for the environmental dependence of active nuclei in local galaxies
Davies, R. I.; Hicks, E. K. S.; Erwin, P. et al

in Monthly Notices of the Royal Astronomical Society (2017), 466

We discuss the environment of local hard X-ray selected active galaxies, with reference to two independent group catalogues. We find that the fraction of these AGN in S0 host galaxies decreases strongly ... [more ▼]

We discuss the environment of local hard X-ray selected active galaxies, with reference to two independent group catalogues. We find that the fraction of these AGN in S0 host galaxies decreases strongly as a function of galaxy group size (halo mass) - which contrasts with the increasing fraction of galaxies of S0 type in denser environments. However, there is no evidence for an environmental dependence of AGN in spiral galaxies. Because most AGN are found in spiral galaxies, this dilutes the signature of environmental dependence for the population as a whole. We argue that the differing results for AGN in disc-dominated and bulge-dominated galaxies are related to the source of the gas fuelling the AGN, and so may also impact the luminosity function, duty cycle and obscuration. We find that there is a significant difference in the luminosity function for AGN in spiral and S0 galaxies, and tentative evidence for some difference in the fraction of obscured AGN. [less ▲]

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See detailThick discs, and an outflow, of dense gas in the nuclei of nearby Seyfert galaxies
Lin, M.-Y.; Davies, R. I.; Burtscher, L. et al

in Monthly Notices of the Royal Astronomical Society (2016), 458

We discuss the dense molecular gas in central regions of nearby Seyfert galaxies, and report new arcsec resolution observations of HCN (1-0) and HCO+ (1-0) for three objects. In NGC 3079, the lines show ... [more ▼]

We discuss the dense molecular gas in central regions of nearby Seyfert galaxies, and report new arcsec resolution observations of HCN (1-0) and HCO+ (1-0) for three objects. In NGC 3079, the lines show complex profiles as a result of self-absorption and saturated continuum absorption. H13CN reveals the continuum absorption profile, with a peak close to the galaxy's systemic velocity that traces disc rotation, and a second feature with a blue wing extending to -350 km s-1 that most likely traces a nuclear outflow. The morphological and spectral properties of the emission lines allow us to constrain the dense gas dynamics. We combine our kinematic analysis for these three objects, as well as another with archival data, with a previous comparable analysis of four other objects, to create a sample of eight Seyferts. In seven of these, the emission line kinematics imply thick disc structures on radial scales of ˜100 pc, suggesting such structures are a common occurrence. We find a relation between the circum-nuclear LHCN and Mdyn that can be explained by a gas fraction of 10 per cent and a conversion factor αHCN ˜ 10 between gas mass and HCN luminosity. Finally, adopting a different perspective to probe the physical properties of the gas around active galactic nuclei, we report on an analysis of molecular line ratios which indicates that the clouds in this region are not self-gravitating. [less ▲]

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See detailConstraints on the broad-line region properties and extinction in local Seyferts
Schnorr-Müller, A.; Davies, R. I.; Korista, K. T. et al

in Monthly Notices of the Royal Astronomical Society (2016), 462

We use high-spectral resolution (R > 8000) data covering 3800-13 000 Å to study the physical conditions of the broad-line region (BLR) of nine nearby Seyfert 1 galaxies. Up to six broad H I lines are ... [more ▼]

We use high-spectral resolution (R > 8000) data covering 3800-13 000 Å to study the physical conditions of the broad-line region (BLR) of nine nearby Seyfert 1 galaxies. Up to six broad H I lines are present in each spectrum. A comparison - for the first time using simultaneous optical to near-infrared observations - to photoionization calculations with our devised simple scheme yields the extinction to the BLR at the same time as determining the density and photon flux, and hence distance from the nucleus, of the emitting gas. This points to a typical density for the H I emitting gas of 1011 cm-3 and shows that a significant amount of this gas lies at regions near the dust sublimation radius, consistent with theoretical predictions. We also confirm that in many objects, the line ratios are far from case B, the best-fitting intrinsic broad-line Hα/H β ratios being in the range 2.5-6.6 as derived with our photoionization modelling scheme. The extinction to the BLR, based on independent estimates from H I and He II lines, is AV ≤ 3 for Seyfert 1-1.5s, while Seyfert 1.8-1.9s have AV in the range 4-8. A comparison of the extinction towards the BLR and narrow-line region (NLR) indicates that the structure obscuring the BLR exists on scales smaller than the NLR. This could be the dusty torus, but dusty nuclear spirals or filaments could also be responsible. The ratios between the X-ray absorbing column NH and the extinction to the BLR are consistent with the Galactic gas-to-dust ratio if NH variations are considered. [less ▲]

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See detailSocial impacts of the Forest Stewardship Council certification in the Congo basin
Cerutti, P.O.; Lescuyer, G.; Tacconi, L. et al

in International Forestry Review (2016), 18(S1), 14

We assess whether the implementation of the Forest Stewardship Council (FSC) certification scheme in the Congo basin has had positive additional impacts—as compared to existing regulatory frameworks ... [more ▼]

We assess whether the implementation of the Forest Stewardship Council (FSC) certification scheme in the Congo basin has had positive additional impacts—as compared to existing regulatory frameworks applied in noncertified Forest Management Units (FMU)—on (1) the working and living conditions of logging companies’ employees and their families, (2) the effectiveness and legitimacy of the institutions and benefit-sharing mechanisms set up to regulate relationships between logging companies and neighbouring communities, and (3) the local populations’ rights to and customary uses of forests. Results on (1) and (2) suggest that several significant differences exist between certified and noncertified FMUs. Results are instead mitigated on (3): Companies in certified FMUs tend to better enforce the law, but this may have unwanted negative impacts on customary uses. We discuss the reasons why several positive social outcomes materialised in certified vs. noncertified areas, and suggest possible improvements as well as required further research. [less ▲]

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See detailInsights on the Dusty Torus and Neutral Torus from Optical and X-Ray Obscuration in a Complete Volume Limited Hard X-Ray AGN Sample
Davies, R. I.; Burtscher, L.; Rosario, D. et al

in Astrophysical Journal (2015), 806

We describe a complete volume limited sample of nearby active galaxies selected by their 14-195 keV luminosity, and outline its rationale for studying the mechanisms regulating gas inflow and outflow. We ... [more ▼]

We describe a complete volume limited sample of nearby active galaxies selected by their 14-195 keV luminosity, and outline its rationale for studying the mechanisms regulating gas inflow and outflow. We also describe a complementary sample of inactive galaxies, selected to match the host galaxy properties. The active sample appears to have no bias in terms of active galactic nucleus (AGN) type, the only difference being the neutral absorbing column, which is two orders of magnitude greater for the Seyfert 2s. In the luminosity range spanned by the sample, log {{L}14-195 keV}[erg\{{s}-1}]=42.4-43.7, the optically obscured and X-ray absorbed fractions are 50%-65%. The similarity of these fractions to more distant spectroscopic AGN samples, although over a limited luminosity range, suggests that the torus does not strongly evolve with redshift. Our sample confirms that X-ray unabsorbed Seyfert 2s are rare, comprising not more than a few percent of the Seyfert 2 population. At higher luminosities, the optically obscured fraction decreases (as expected for the increasing dust sublimation radius), but the X-ray absorbed fraction changes little. We argue that the cold X-ray absorption in these Seyfert 1s can be accounted for by neutral gas in clouds that also contribute to the broad-line region (BLR) emission, and suggest that a geometrically thick neutral gas torus co-exists with the BLR and bridges the gap to the dusty torus. [less ▲]

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See detailObscuration in active galactic nuclei: near-infrared luminosity relations and dust colors
Burtscher, L.; Orban De Xivry, Gilles ULiege; Davies, R. I. et al

in Astronomy and Astrophysics (2015), 578

We combine two approaches to isolate the AGN luminosity at near-IR wavelengths and relate the near-IR pure AGN luminosity to other tracers of the AGN. Using integral-field spectroscopic data of an ... [more ▼]

We combine two approaches to isolate the AGN luminosity at near-IR wavelengths and relate the near-IR pure AGN luminosity to other tracers of the AGN. Using integral-field spectroscopic data of an archival sample of 51 local AGNs, we estimate the fraction of non-stellar light by comparing the nuclear equivalent width of the stellar 2.3 μm CO absorption feature with the intrinsic value for each galaxy. We compare this fraction to that derived from a spectral decomposition of the integrated light in the central arcsecond and find them to be consistent with each other. Using our estimates of the near-IR AGN light, we find a strong correlation with presumably isotropic AGN tracers. We show that a significant offset exists between type 1 and type 2 sources in the sense that type 1 sources are 7 (10) times brighter in the near-IR at log lmir{} = 42.5 (log lx{} = 42.5). These offsets only become clear when treating infrared type 1 sources as type 1 AGNs. All AGNs have very red near- to mid-IR dust colors. This, as well as the range of observed near-IR temperatures, can be explained with a simple model with only two free parameters: the obscuration to the hot dust and the ratio between the warm and hot dust areas. We find obscurations of AV^hot = 5 ldots 15 mag for infrared type 1 sources and AV^hot = 15 ldots 35 mag for type 2 sources. The ratio of hot dust to warm dust areas of about 1000 is nicely consistent with the ratio of radii of the respective regions as found by infrared interferometry. [less ▲]

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See detailPast and present secular evolution in the host galaxies of NLS1s
Orban De Xivry, Gilles ULiege; Davies, R.; Schartmann, M. et al

in Narrow-Line Seyfert 1 Galaxies and their Place in the Universe (2011)

In this contribution we show that the host galaxies of NLS1s differ dramatically from those of Broad-Line Seyfert 1s (BLS1s). This leads us to propose that NLS1s represent a class of AGN in which the ... [more ▼]

In this contribution we show that the host galaxies of NLS1s differ dramatically from those of Broad-Line Seyfert 1s (BLS1s). This leads us to propose that NLS1s represent a class of AGN in which the black hole growth is, and has always been, dominated by secular evolution. Our line of argument is as follows. Firstly, by looking at the properties of NLS1 hosts in the literature, we show that the evolution of NLS1s is currently mainly driven by secular processes, in contrast to BLS1s. Secondly, we study the bulges of NLS1 and BLS1 galaxies, and we find that statistically NLS1s have lower Sérsic indices (< nb >∼ 1.5) and less prominent bulges (bulge-to-total light ratio, < B/T >∼ 0.2) than BLS1s (< nb >∼ 2.5 and < B/T >∼ 0.4). This result indicates that NLS1 host bulges are pseudo-bulges and distinct from BLS1 bulges. The direct consequence of this result is that internal secular evolution must have dominated the past evolution of NLS1 hosts, possibly explaining their particular AGN properties. [less ▲]

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See detailThe role of secular evolution in the black hole growth of narrow-line Seyfert 1 galaxies
Orban De Xivry, Gilles ULiege; Davies, R.; Schartmann, M. et al

in Monthly Notices of the Royal Astronomical Society (2011), 417

Narrow-line Seyfert 1 (NLS1) galaxies show extreme properties with respect to the other Seyfert galaxies. Indeed, they are thought to be accreting at Eddington rates and to possess low-mass black holes ... [more ▼]

Narrow-line Seyfert 1 (NLS1) galaxies show extreme properties with respect to the other Seyfert galaxies. Indeed, they are thought to be accreting at Eddington rates and to possess low-mass black holes. Therefore, they may represent a key class of objects for understanding the co-evolution of black holes and their host galaxies. We propose that NLS1s represent a class of active galactic nucleus in which the black hole growth is, and has always been, dominated by secular evolution. First, by looking at the NLS1 host galaxy properties in the literature, we show that the evolution of NLS1s is presently driven by secular processes, much more so than for broad-line Seyfert 1s (BLS1s). Secondly, we study the bulges of NLS1 and BLS1 galaxies. Our results demonstrate that NLS1 host bulges are pseudo-bulges and are statistically different from BLS1 bulges. This difference points to the particular importance of secular processes in the past evolution of their hosts. We build on this result to understand the implications on their evolution and the duration of their duty cycle. We show that NLS1s are not necessarily in a special phase of black hole growth and that several Gyr are required for their black hole masses to become similar to BLS1s. Finally, in the light of our results, we discuss the location of NLS1 galaxies on the MBH-σ plane and speculate about the connection between the NLS1 galaxy properties and their black hole spin. [less ▲]

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See detailThe Dusty Young Universe: photometry and spectroscopy of quasars at z > 2
Meisenheimer, K.; Hutsemekers, Damien ULiege; Tacconi, L. et al

Poster (2007)

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See detailThe Dusty Young Universe
Meisenheimer, K.; Dannerbauer, H.; Klaas, U. et al

Poster (2007)

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