6,539 research outputs found
The Relation between Black Hole Mass, Bulge Mass, and Near-Infrared Luminosity
We present new accurate near-infrared (NIR) spheroid (bulge) structural
parameters obtained by two-dimensional image analysis for all galaxies with a
direct black hole (BH) mass determination. As expected, NIR bulge luminosities
Lbul and BH masses are tightly correlated, and if we consider only those
galaxies with secure BH mass measurement and accurate Lbul (27 objects), the
spread of MBH-Lbul is similar to MBH-sigma, where sigma is the effective
stellar velocity dispersion. We find an intrinsic rms scatter of ~0.3 dex in
log MBH. By combining the bulge effective radii R_e measured in our analysis
with sigma, we find a tight linear correlation (rms ~ 0.25 dex) between MBH and
the virial bulge mass (propto R_e sigma^2), with ~ 0.002. A partial
correlation analysis shows that MBH depends on both sigma and R_e, and that
both variables are necessary to drive the correlations between MBH and other
bulge properties.Comment: Astrophysical Journal Letters, in pres
Search for pulsating PMS stars in NGC 6383
A search for pulsating pre-main sequence (PMS) stars was performed in the
young open cluster NGC 6383 using CCD time series photometry in Johnson B & V
filters. With an age of only ~1.7 million years all cluster members later than
spectral type A0 have not reached the ZAMS yet, hence being ideal candidates
for investigating PMS pulsation among A and F type stars. In total 286 stars
have been analyzed using classical Fourier techniques. From about a dozen of
stars within the boundaries of the classical instability strip, two stars were
found to pulsate: NGC 6383 #170, with five frequencies simultaneously, and NGC
6383 #198, with a single frequency. In addition, NGC 6383 #152 is a suspected
PMS variable star, but our data remain inconclusive. Linear, non-adiabatic
models assuming PMS evolutionary phase and purely radial pulsation were
calculated for the two new PMS pulsators. NGC 6383 #170 appears to pulsate
radially in third and fifth overtones, while the other three frequencies seem
to be of non-radial nature. NGC 6383 #198 pulsates monoperiodically, most
probably in the third radial overtone. Magnitudes and B-V colours were
available in the literature for only one third of all stars and we used them
for calibrating the remaining.Comment: 12 pages, 11 figures, accepted by MNRA
Critical properties of Ising model on Sierpinski fractals. A finite size scaling analysis approach
The present paper focuses on the order-disorder transition of an Ising model
on a self-similar lattice. We present a detailed numerical study, based on the
Monte Carlo method in conjunction with the finite size scaling method, of the
critical properties of the Ising model on some two dimensional deterministic
fractal lattices with different Hausdorff dimensions. Those with finite
ramification order do not display ordered phases at any finite temperature,
whereas the lattices with infinite connectivity show genuine critical behavior.
In particular we considered two Sierpinski carpets constructed using different
generators and characterized by Hausdorff dimensions d_H=log 8/log 3 = 1.8927..
and d_H=log 12/log 4 = 1.7924.., respectively.
The data show in a clear way the existence of an order-disorder transition at
finite temperature in both Sierpinski carpets.
By performing several Monte Carlo simulations at different temperatures and
on lattices of increasing size in conjunction with a finite size scaling
analysis, we were able to determine numerically the critical exponents in each
case and to provide an estimate of their errors.
Finally we considered the hyperscaling relation and found indications that it
holds, if one assumes that the relevant dimension in this case is the Hausdorff
dimension of the lattice.Comment: 21 pages, 7 figures; a new section has been added with results for a
second fractal; there are other minor change
Driven low density granular mixtures
We study the steady state properties of a 2D granular mixture in the presence
of energy driving by employing simple analytical estimates and Direct
Simulation Monte Carlo. We adopt two different driving mechanisms: a) a
homogeneous heat bath with friction and b) a vibrating boundary (thermal or
harmonic) in the presence of gravity. The main findings are: the appearance of
two different granular temperatures, one for each species; the existence of
overpopulated tails in the velocity distribution functions and of non trivial
spatial correlations indicating the spontaneous formation of cluster
aggregates. In the case of a fluid subject to gravity and to a vibrating
boundary, both densities and temperatures display non uniform profiles along
the direction normal to the wall, in particular the temperature profiles are
different for the two species while the temperature ratio is almost constant
with the height. Finally, we obtained the velocity distributions at different
heights and verified the non gaussianity of the resulting distributions.Comment: 19 pages, 12 figures, submitted for publicatio
The supermassive black hole mass - S\'ersic index relations for bulges and elliptical galaxies
Scaling relations between supermassive black hole mass, M_BH, and host galaxy
properties are a powerful instrument for studying their coevolution. A complete
picture involving all of the black hole scaling relations, in which each
relation is consistent with the others, is necessary to fully understand the
black hole-galaxy connection. The relation between M_BH and the central light
concentration of the surrounding bulge, quantified by the S\'ersic index n, may
be one of the simplest and strongest such relations, requiring only
uncalibrated galaxy images. We have conducted a census of literature S\'ersic
index measurements for a sample of 54 local galaxies with directly measured
M_BH values. We find a clear M_BH - n relation, despite an appreciable level of
scatter due to the heterogeneity of the data. Given the current M_BH - L_sph
and the L_sph - n relations, we have additionally derived the expected M_BH - n
relations, which are marginally consistent at the 2 sigma level with the
observed relations. Elliptical galaxies and the bulges of disc galaxies are
each expected to follow two distinct bent M_BH - n relations due to the
S\'ersic/core-S\'ersic divide. For the same central light concentration, we
predict that M_BH in the S\'ersic bulges of disc galaxies are an order
magnitude higher than in S\'ersic elliptical galaxies if they follow the same
M_BH - L_sph relation.Comment: 12 pages, 6 figures, 5 tables, accepted for publication in MNRA
Agronomic characteristics of the spring forms of the wheat landraces (einkorn, emmer, spelt, intermediate bread wheat) grown in organic farming
Organic farmers look to the possibilities of growing neglected crops, such as the spring forms of hulled wheat – einkorn, emmer and spelt – for support in developing the organic farming system. In 2008, 169 landraces from the gene bank at the Crop Research Institute in Prague were tested on certifi ed organic plots. The experiment was aimed at fi nding suitable varieties for the organic farming system. In summary, our fi ndings show that einkorn (Triticum monococcum L.) and emmer wheat [Triticum dicoccum Schrank (Schuebl)] are resistant to powdery mildew and brown rust, spelt wheat (Triticum spelta L.) is less resistant to these two diseases, and the intermediate forms of bread wheat are very sensitive to such infestation. The
varieties evaluated incline to lodging, as they have long and weak stems. Einkorn and emmer wheat have short and dense spikes and a low thousand grains weight, whereas spelt wheat has long and lax spikes. The level of the harvest index is low. Potentially useful varieties were
found during the fi eld experiment and evaluation, and our future efforts will therefore focus on improving resistance to lodging and increasing the productivity of the spike
Feedback-controlled transport in an interacting colloidal system
Based on dynamical density functional theory (DDFT) we consider a
non-equilibrium system of interacting colloidal particles driven by a constant
tilting force through a periodic, symmetric "washboard" potential. We
demonstrate that, despite of pronounced spatio-temporal correlations, the
particle current can be reversed by adding suitable feedback control terms to
the DDFT equation of motion. We explore two distinct control protocols with
time delay, focussing on either the particle positions or the density profile.
Our study shows that the DDFT is an appropriate framework to implement
time-delayed feedback control strategies widely used in other fields of
nonlinear physicsComment: 6 pages, 5 figure
An Observational Pursuit for Population III Stars in a Ly_alpha Emitter at z=6.33 through HeII Emission
We present a very deep near-infrared spectroscopic observation of a strong
Ly_alpha emitter at z=6.33, SDF J132440.6+273607, which we used to search for
HeII 1640. This emission line is expected if the target hosts a significant
number of population III stars. Even after 42 ksec of integration with the
Subaru/OHS spectrograph, no emission-line features are detected in the JH band,
which confirms that SDF J132440.6+273607 is neither an active galactic nucleus
nor a low- emission-line object. We obtained a 2sigma upper-limit of
9.06e-18 ergs/s/cm^2 on the HeII 1640 emission line flux, which corresponds to
a luminosity of 4.11e42 ergs/s. This upper-limit on the HeII 1640 luminosity
implies that the upper limit on population III star-formation rate is in the
range 4.9--41.2 M_sun/yr if population III stars suffer no mass loss, and in
the range 1.8--13.2 M_sun/yr if strong mass loss is present. The non-detection
of HeII in SDF J132440.6+273607 at z=6.33 may thus disfavor weak feedback
models for population III stars.Comment: 13 pages, 3 figures, to appear in The Astrophysical Journal Letter
Interface pinning and slow ordering kinetics on infinitely ramified fractal structures
We investigate the time dependent Ginzburg-Landau (TDGL) equation for a non
conserved order parameter on an infinitely ramified (deterministic) fractal
lattice employing two alternative methods: the auxiliary field approach and a
numerical method of integration of the equations of evolution. In the first
case the domain size evolves with time as , where is
the anomalous random walk exponent associated with the fractal and differs from
the normal value 2, which characterizes all Euclidean lattices. Such a power
law growth is identical to the one observed in the study of the spherical model
on the same lattice, but fails to describe the asymptotic behavior of the
numerical solutions of the TDGL equation for a scalar order parameter. In fact,
the simulations performed on a two dimensional Sierpinski Carpet indicate that,
after an initial stage dominated by a curvature reduction mechanism \`a la
Allen-Cahn, the system enters in a regime where the domain walls between
competing phases are pinned by lattice defects.
The lack of translational invariance determines a rough free energy
landscape, the existence of many metastable minima and the suppression of the
marginally stable modes, which in translationally invariant systems lead to
power law growth and self similar patterns. On fractal structures as the
temperature vanishes the evolution is frozen, since only thermally activated
processes can sustain the growth of pinned domains.Comment: 16 pages+14 figure
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