414 research outputs found
Long-Term Profile Variability of Double-Peaked Emmission Lines in AGNs
An increasing number of AGNs exhibit broad, double-peaked Balmer emission
lines, which arise from the outer regions of the accretion disk which fuels the
AGN. The line profiles vary on timescales of 5--10 years. Our group has
monitored a set of 20 double-peaked emitters for the past 8 years (longer for
some objects). Here we describe a project to characterize the variability
patterns of the double-peaked H alpha line profiles and compare with those of
two simple models: a circular disk with a spiral arm and an elliptical disk.Comment: 2 pages, 1 figure, to appear in the proceedings of "The Interplay
among Black Holes, Stars and ISM in Galactic Nuclei", IAU 222, eds. T.
Storchi Bergmann, L.C. Ho, and H.R. Schmit
The Ultraviolet Spectra of Active Galaxies With Double-Peaked Emission Lines
We present the results of UV spectroscopy of AGNs with double-peaked Balmer
emission lines. In 2/3 of the objects, the far-UV resonance lines are strong,
with single-peaked profiles resembling those of Seyfert galaxies. The Mg II
line is the only UV line with a double-peaked profile. In the remaining
objects, the far-UV resonance lines are relatively weak but still
single-peaked. The latter group also displays prominent UV absorption lines,
indicative of a low-ionization absorber. We interpret the difference in the
profiles of the emission lines as resulting from two different regions: a
dense, low-ionization accretion disk (the predominant source of the Balmer and
Mg II lines), and a lower density, higher-ionization wind (the predominant
source of the far-UV resonance lines). These results suggest a way of
connecting the double-peaked emitters with the greater AGN population: in
double-peaked emitters the accretion rate onto the black hole is low, making
the wind feeble and allowing the lines from the underlying disk to shine
through. This scenario also implies that in the majority of AGNs, the wind is
the source of the broad emission lines.Comment: To appear in "The Interplay among Black Holes, Stars and ISM in
Galactic Nuclei," IAU Coll. 222, eds. Storchi Bergmann, Ho, and Schmit
On the nature of the near-UV extended light in Seyfert galaxies
We study the nature of the extended near-UV emission in the inner kiloparsec
of a sample of 15 Seyfert galaxies which have both near-UV (F330W) and narrow
band [OIII] high resolution Hubble images. For the majority of the objects we
find a very similar morphology in both bands. From the [OIII] images we
construct synthetic images of the nebular continuum plus the emission line
contribution expected through the F330W filter, which can be subtracted from
the F330W images. We find that the emission of the ionised gas dominates the
near-UV extended emission in half of the objects. A further broad band
photometric study, in the bands F330W (U), F547M (V) and F160W (H), shows that
the remaining emission is dominated by the underlying galactic bulge
contribution. We also find a blue component whose nature is not clear in 4 out
of 15 objects. This component may be attributed to scattered light from the
AGN, to a young stellar population in unresolved star clusters, or to
early-disrupted clusters. Star forming regions and/or bright off-nuclear star
clusters are observed in 4/15 galaxies of the sample.Comment: 23 pages, 6 figures, 3 tables; accepted for publication in MNRA
Near-infrared and X-ray obscuration to the nucleus of the Seyfert 2 galaxy NGC 3281
We present the results of a near-infrared and X-ray study of the Seyfert 2
galaxy NGC 3281. Emission from the Seyfert nucleus is detected in both regions
of the electromagnetic spectrum, allowing us to infer both the equivalent line
of sight hydrogen column density, N_H = 71.0(+11.3,-12.3)e26/m^2 and the
extinction due to dust, A_V = 22+/-11 magnitudes (90% confidence intervals). We
infer a ratio of N_H/A_V which is an order of magnitude larger than that
determined along lines of sight in the Milky Way and discuss possible
interpretations. We consider the most plausible explanation to be a dense cloud
in the foreground of both the X-ray and infrared emitting regions which
obscures the entire X-ray source but only a fraction of the much larger
infrared source.Comment: 23 pages including 9 figure
‘Sangiovese’ and ‘Garganega’ are two key varieties of the Italian grapevine assortment evolution
Two synonymous cases have been found using a set of 11 SSR markers: ‘Garganega’ and ‘Grecanico dorato’; ‘Catarratto bianco comune’, ‘Catarratto bianco lucido’ and ‘Catarratto bianco extra lucido’. Molecular data at 36 SSR loci showed that ‘Sangiovese’ and ‘Garganega’ represent two key varieties in the Italian ampelographic assortment evolution, as they both have a first degree relationship with numerous wine varieties. ‘Sangiovese’ showed this link with ten varieties: ‘Foglia tonda’, ‘Frappato’, ‘Gaglioppo’, ‘Mantonicone’, ‘Morellino del Casentino’, ‘Morellino del Valdarno’, ‘Nerello mascalese’, ‘Susumaniello’, ‘Tuccanese di Turi’ and ‘Vernaccia nera del Valdarno’. Seven varieties resulted closely related to ‘Garganega’: ‘Trebbiano toscano’ alias ‘Ugni blanc’, ‘Albana’, ‘Empibotte’, ‘Malvasia bianca di Candia a sapore semplice’, ‘Marzemina bianca’, ‘Catarratto’ and ‘Greco del Pollino’. However, being ‘Sangiovese’ parents disputed and those of ‘Garganega’ still unknown, it was not possible to determine the univocal direction of the various crosses. Identification of the “missing” parents would allow these genealogical trees to be drawn up with greater precision.
Relevance of the Lin's and Host hydropedological models to predict grape yield and wine quality
The adoption of precision agriculture in viticulture could be greatly enhanced by the diffusion of straightforward and easy to be applied hydropedological models, able to predict the spatial variability of available soil water. The Lin's and Host hydropedological models were applied to standard soil series descriptions and hillslope position, to predict the distribution of hydrological functional units in two vineyard and their relevance for grape yield and wine quality. A three-years trial was carried out in Chianti (Central Italy) on Sangiovese. The soils of the vineyards differentiated in structure, porosity and related hydropedological characteristics, as well as in salinity. Soil spatial variability was deeply affected by earth movement carried out before vine plantation. Six plots were selected in the different hydrological functional units of the two vineyards, that is, at summit, backslope and footslope morphological positions, to monitor soil hydrology, grape production and wine quality. Plot selection was based upon a cluster analysis of local slope, topographic wetness index (TWI), and cumulative moisture up to the root limiting layer, appreciated by means of a detailed combined geophysical survey. Water content, redox processes and temperature were monitored, as well as yield, phenological phases, and chemical analysis of grapes. The isotopic ratio δ<sup>13</sup>C was measured in the wine ethanol upon harvesting to evaluate the degree of stress suffered by vines. The grapes in each plot were collected for wine making in small barrels. The wines obtained were analysed and submitted to a blind organoleptic testing. <br></br> The results demonstrated that the combined application of the two hydropedological models can be used for the prevision of the moisture status of soils cultivated with grape during summertime in Mediterranean climate. As correctly foreseen by the models, the amount of mean daily transpirable soil water (TSW) during the growing season differed considerably between the vineyards and increased significantly along the three positions on slope in both vineyards. The water accumulation along slope occurred in every year, even during the very dry 2006. The installation of indicators of reduction in soils (IRIS) tubes allowed confirmation of the occurrence of reductive processes in the most shallow soil. <br></br> Both Sangiovese grape yield and quality of wine were influenced by the interaction between TSW content and salinity, sometimes contrary to expectations. Therefore, the studied hydropedological models were not relevant to predict grape yield and wine quality in all the hydrological functional units. The diffusion of hydropedological models in precision viticulture could be boosted considering salinity along with topography and soil hydrological characteristics
Investigations on the identity of ‘Canaiolo bianco’ and other white grape varieties of central Italy
During research for the rescue and description of grapevine germplasm in central Italy, 28 white accessions were collected, 10 of them sharing the name ‘Canaiolo bianco’ but having different morphological and yield characteristics. ‘Canaiolo bianco’ is listed as essential in the specifications for some D.O.C.G. and D.O.C. Tuscan wines, but its correct identity is not clear. With the aim to identify and characterize our samples and to pinpoint what the true-to-type ‘Canaiolo bianco’ is, we described these accessions using a multidisciplinary approach, encompassing DNA analysis, ampelographic, phyllometric, phenological and yield descriptions. Moreover we collected as much historical information as possible about them. The 28 accessions investigated were grouped in 8 varieties with very distinct traits. The research has provided useful information for clarifying various cases of synonymy and homonymy. Moreover, we hypothesize that the true to type ‘Canaiolo bianco’ corresponds to the so called ‘Drupeggio’.
EUVE J0425.6-5714: A Newly Discovered AM Herculis Star
We detected a new AM Her star serendipitously in a 25 day observation with
the EUVE satellite. A coherent period of 85.82 min is present in the EUVE Deep
Survey imager light curve of this source. A spectroscopic identification is
made with a 19th magnitude blue star that has H and He emission lines, and
broad cyclotron humps typical of a magnetic cataclysmic variable. A lower limit
to the polar magnetic field of 46 MG is estimated from the spacing of the
cyclotron harmonics. EUVE J0425.6-5714 is also detected in archival ROSAT HRI
observations spanning two months, and its stable and highly structured light
curve permits us to fit a coherent ephemeris linking the ROSAT and EUVE data
over a 1.3 yr gap. The derived period is 85.82107 +/- 0.00020 min, and the
ephemeris should be accurate to 0.1 cycles until the year 2005. A narrow but
partial X-ray eclipse suggests that this object belongs to the group of Am Her
stars whose viewing geometry is such that the accretion stream periodically
occults the soft X-ray emitting accretion spot on the surface of the white
dwarf. A non-detection of hard X-rays from ASCA observations that are
contemporaneous with the ROSAT HRI shows that the soft X-rays must dominate by
at least an order of magnitude, which is consistent with a known trend among AM
Her stars with large magnetic field. This object should not be confused with
the Seyfert galaxy 1H 0419-577 (= LB 1727), another X-ray/EUV source which lies
only 4' away, and was the principal target of these monitoring observations.Comment: 13 pages, 5 figures, to appear in PASP, Dec. 1998 issu
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