References of "Marconi, A"
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See detailHunting for Planets in the HL Tau Disk
Testi, L.; Skemer, A.; Henning, Th et al

in Astrophysical Journal Letters (2015), 812

Recent ALMA images of HL Tau show gaps in the dusty disk that may be caused by planetary bodies. Given the young age of this system, if confirmed, this finding would imply very short timescales for planet ... [more ▼]

Recent ALMA images of HL Tau show gaps in the dusty disk that may be caused by planetary bodies. Given the young age of this system, if confirmed, this finding would imply very short timescales for planet formation, probably in a gravitationally unstable disk. To test this scenario, we searched for young planets by means of direct imaging in the L‧ band using the Large Binocular Telescope Interferometer mid-infrared camera. At the location of two prominent dips in the dust distribution at ˜70 AU (˜0.″5) from the central star, we reach a contrast level of ˜7.5 mag. We did not detect any point sources at the location of the rings. Using evolutionary models we derive upper limits of ˜10-15 M[SUB]Jup[/SUB] at ≤0.5-1 Ma for the possible planets. With these sensitivity limits we should have been able to detect companions sufficiently massive to open full gaps in the disk. The structures detected at millimeter wavelengths could be gaps in the distributions of large grains on the disk midplane caused by planets not massive enough to fully open the gaps. Future ALMA observations of the molecular gas density profile and kinematics as well as higher contrast infrared observations may be able to provide a definitive answer. [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 detailMilli-arcsecond Astrophysics with VSI, the VLTI Spectro-imager in the ELT Era
Malbet, F.; Buscher, D.; Weigelt, G. et al

in Moorwood, Alan (Ed.) Science with the VLT in the ELT Era (2009)

Nowadays, compact sources relatively warm like surfaces of nearby stars, circumstellar environments of stars from early stages to the most evolved ones and surroundings of active galactic nuclei can be ... [more ▼]

Nowadays, compact sources relatively warm like surfaces of nearby stars, circumstellar environments of stars from early stages to the most evolved ones and surroundings of active galactic nuclei can be investigated at milli-arcsecond scales only with the VLT in its interferometric mode. We propose a spectro-imager, named VSI (VLTI spectro-imager), which is capable to probe these sources both over spatial and spectral scales in the near-infrared domain. This instrument will provide information complementary to what is obtained at the same time with ALMA at different wavelengths and the extreme large telescopes. [less ▲]

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See detailVSI: the VLTI spectro-imager
Malbet, F.; Buscher, D.; Weigelt, G. et al

in Schöller, Markus; Danchi, William; Delplancke, Françoise (Eds.) Optical and Infrared Interferometry (2008, July 01)

The VLTI Spectro Imager (VSI) was proposed as a second-generation instrument of the Very Large Telescope Interferometer providing the ESO community with spectrally-resolved, near-infrared images at ... [more ▼]

The VLTI Spectro Imager (VSI) was proposed as a second-generation instrument of the Very Large Telescope Interferometer providing the ESO community with spectrally-resolved, near-infrared images at angular resolutions down to 1.1 milliarcsecond and spectral resolutions up to R = 12000. Targets as faint as K = 13 will be imaged without requiring a brighter nearby reference object; fainter targets can be accessed if a suitable reference is available. The unique combination of high-dynamic-range imaging at high angular resolution and high spectral resolution enables a scientific program which serves a broad user community and at the same time provides the opportunity for breakthroughs in many areas of astrophysics. The high level specifications of the instrument are derived from a detailed science case based on the capability to obtain, for the first time, milliarcsecond-resolution images of a wide range of targets including: probing the initial conditions for planet formation in the AU-scale environments of young stars; imaging convective cells and other phenomena on the surfaces of stars; mapping the chemical and physical environments of evolved stars, stellar remnants, and stellar winds; and disentangling the central regions of active galactic nuclei and supermassive black holes. VSI will provide these new capabilities using technologies which have been extensively tested in the past and VSI requires little in terms of new infrastructure on the VLTI. At the same time, VSI will be able to make maximum use of new infrastructure as it becomes available; for example, by combining 4, 6 and eventually 8 telescopes, enabling rapid imaging through the measurement of up to 28 visibilities in every wavelength channel within a few minutes. The current studies are focused on a 4-telescope version with an upgrade to a 6-telescope one. The instrument contains its own fringe tracker and tip-tilt control in order to reduce the constraints on the VLTI infrastructure and maximize the scientific return. [less ▲]

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See detailThe Nucleotide Sequence Of Saccharomyces Cerevisiae Chromosome Vii
Tettelin, H.; Carbone, Mla.; Albermann, K. et al

in Nature (1997), 387(6632),

Detailed reference viewed: 156 (12 ULiège)