191,127 research outputs found
Extragalactic CS survey
We present a coherent and homogeneous multi-line study of the CS molecule in
nearby (D10Mpc) galaxies. We include, from the literature, all the available
observations from the to the transitions towards NGC 253, NGC
1068, IC 342, Henize~2-10, M~82, the Antennae Galaxies and M~83. We have, for
the first time, detected the CS(7-6) line in NGC 253, M~82 (both in the
North-East and South-West molecular lobes), NGC 4038, M~83 and tentatively in
NGC 1068, IC 342 and Henize~2-10. We use the CS molecule as a tracer of the
densest gas component of the ISM in extragalactic star-forming regions,
following previous theoretical and observational studies by Bayet et al.
(2008a,b and 2009). In this first paper out of a series, we analyze the CS data
sample under both Local Thermodynamical Equilibrium (LTE) and non-LTE (Large
Velocity Gradient-LVG) approximations. We show that except for M~83 and Overlap
(a shifted gas-rich position from the nucleus NGC 4039 in the Antennae
Galaxies), the observations in NGC 253, IC 342, M~82-NE, M~82-SW and NGC 4038
are not well reproduced by a single set of gas component properties and that,
at least, two gas components are required. For each gas component, we provide
estimates of the corresponding kinetic temperature, total CS column density and
gas density.Comment: 17 pages, 16 figures, 3 tables, Accepted to Ap
Fully ab initio atomization energy of benzene via W2 theory
The total atomization energy at absolute zero, (TAE) of benzene,
CH, was computed fully {\em ab initio} by means of W2h theory as 1306.6
kcal/mol, to be compared with the experimentally derived value 1305.7+/-0.7
kcal/mol. The computed result includes contributions from inner-shell
correlation (7.1 kcal/mol), scalar relativistic effects (-1.0 kcal/mol), atomic
spin-orbit splitting (-0.5 kcal/mol), and the anharmonic zero-point vibrational
energy (62.1 kcal/mol). The largest-scale calculations involved are
CCSD/cc-pV5Z and CCSD(T)/cc-pVQZ; basis set extrapolations account for 6.3
kcal/mol of the final result. Performance of more approximate methods has been
analyzed. Our results suggest that, even for systems the size of benzene,
chemically accurate molecular atomization energies can be obtained from fully
first-principles calculations, without resorting to corrections or parameters
derived from experiment.Comment: J. Chem. Phys., accepted. RevTeX, 12 page
Research and Development Expenditures of Innovative Enterprises in the Time of Crisis
In an analysed group of enterprises the smallest "resistance" to crisis was observed in American companies. The enterprises from the EU also reduced research and development expenditures but the pace of a fall in these expenditures was smaller than in the case of American companies.W badanej zbiorowości przedsiębiorstw najmniejszą "odporność" na kryzys wykazaly firmy amerykańskie. Firmy wywodzące się z UE również zanotowaly zmniejszenie nakladów na badania i rozwój, jednak tempo spadku nakladów badawczo-rozwojowych bylo tu mniejsze niż w przypadku firm amerykańskich
Probing gaseous halos of galaxies with radio jets
Reproduced with permission from Astronomy & Astrophysics. © 2019 ESOContext. Gaseous halos play a key role in understanding inflow, feedback, and the overall baryon budget in galaxies. Literature models predict transitions of the state of the gaseous halo between cold and hot accretion, winds, fountains, and hydrostatic halos at certain galaxy masses. Since luminosities of radio AGN are sensitive to halo densities, any significant transition would be expected to show up in the radio luminosities of large samples of galaxies. The LOw Frequency ARray (LOFAR) Two-Metre Sky Survey (LoTSS) has identified a galaxy stellar mass scale, 10 11 M ⊙, above which the radio luminosities increase disproportionately. Aims. We investigate if radio luminosities of galaxies, especially the marked rise at galaxy masses around 10 11 M ⊙, can be explained with standard assumptions regarding jet powers, scaling between black hole mass and galaxy mass, and gaseous halos. Methods. Based on observational data and theoretical constraints, we developed models for the radio luminosity of radio AGN in halos under infall, galactic wind, and hydrostatic conditions. We compared these models to LoTSS data for a large sample of galaxies in the mass range between 10 8.5 M ⊙ and 10 12 M ⊙. Results. Under the assumption that the same characteristic upper limit to jet powers known from high galaxy masses holds at all masses, we find the maximum radio luminosities for the hydrostatic gas halos to lie close to the upper envelope of the distribution of the LOFAR data. The marked rise in radio luminosity at 10 11 M ⊙ is matched in our model and is related to a significant change in halo gas density around this galaxy mass, which is a consequence of lower cooling rates at a higher virial temperature. Wind and infall models overpredict the radio luminosities for small galaxy masses and have no particular steepening of the run of the radio luminosities predicted at any galaxy mass. Conclusions. Radio AGN could have the same characteristic Eddington-scaled upper limit to jet powers in galaxies of all masses in the sample if the galaxies have hydrostatic gas halos in phases when radio AGN are active. We find no evidence of a change of the type of galaxy halo with the galaxy mass. Galactic winds and quasi-spherical cosmological inflow phases cannot frequently occur at the same time as powerful jet episodes unless the jet properties in these phases are significantly different from what we assumed in our model.Peer reviewedFinal Accepted Versio
Nonlinear stability of flock solutions in second-order swarming models
In this paper we consider interacting particle systems which are frequently
used to model collective behavior in animal swarms and other applications. We
study the stability of orientationally aligned formations called flock
solutions, one of the typical patterns emerging from such dynamics. We provide
an analysis showing that the nonlinear stability of flocks in second-order
models entirely depends on the linear stability of the first-order aggregation
equation. Flocks are shown to be nonlinearly stable as a family of states under
reasonable assumptions on the interaction potential. Furthermore, we
numerically verify that commonly used potentials satisfy these hypotheses and
investigate the nonlinear stability of flocks by an extensive case-study of
uniform perturbations.Comment: 22 pages, 1 figure, 1 tabl
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