817 research outputs found
Photometric brown-dwarf classification. II. A homogeneous sample of 1361 L and T dwarfs brighter than J = 17.5 with accurate spectral types
We present a homogeneous sample of 1361 L and T dwarfs brighter than J = 17.5
(of which 998 are new), from an effective area of 3070 deg2, classified by the
photo-type method to an accuracy of one spectral sub-type using izYJHKW1W2
photometry from SDSS+UKIDSS+WISE. Other than a small bias in the early L types,
the sample is shown to be effectively complete to the magnitude limit, for all
spectral types L0 to T8. The nature of the bias is an incompleteness estimated
at 3% because peculiar blue L dwarfs of type L4 and earlier are classified late
M. There is a corresponding overcompleteness because peculiar red (likely
young) late M dwarfs are classified early L. Contamination of the sample is
confirmed to be small: so far spectroscopy has been obtained for 19 sources in
the catalogue and all are confirmed to be ultracool dwarfs. We provide
coordinates and izYJHKW1W2 photometry of all sources. We identify an apparent
discontinuity, m 0.4 mag., in the Y-K colour between spectral
types L7 and L8. We present near-infrared spectra of nine sources identified by
photo-type as peculiar, including a new low-gravity source ULAS
J005505.68+013436.0, with spectroscopic classification L2{}. We provide
revised izYJHKW1W2 template colours for late M dwarfs, types M7 to M9.Comment: Accepted for publication in A & A, 17 pages, 14 figures, catalogue of
L and T dwarfs supplied here in source files (anc/ directory), and available
on CD
Solving QCD evolution equations in rapidity space with Markovian Monte Carlo
This work covers methodology of solving QCD evolution equation of the parton
distribution using Markovian Monte Carlo (MMC) algorithms in a class of models
ranging from DGLAP to CCFM. One of the purposes of the above MMCs is to test
the other more sophisticated Monte Carlo programs, the so-called Constrained
Monte Carlo (CMC) programs, which will be used as a building block in the
parton shower MC. This is why the mapping of the evolution variables (eikonal
variable and evolution time) into four-momenta is also defined and tested. The
evolution time is identified with the rapidity variable of the emitted parton.
The presented MMCs are tested independently, with ~0.1% precision, against the
non-MC program APCheb especially devised for this purpose.Comment: version compatible with with the erratum in Acta Physica Polonic
Synthesis and Properties of High Tilted Antiferroelectric Esters with Partially Fluorinated Alkoxyalkoxy Terminal Chains
Novel chiral esters with partially fluorinated alkoxyalkoxy terminal chains are described. Their phase transition temperatures, enthalpies, and electrooptical properties are reported. A helical pitch in pure compounds and their mixtures based on selective reflection of light is also characterized
The effect of light intensity on the production of oat (Avena sativa L.) doubled haploids through oat × maize crosses
Oat haploid embryos were obtained by wide crossing with maize. The effect of light intensity during the growing period of donor plants (450 and 800 µmol m−2 s−1) and in vitro cultures (20, 40, 70 and 110 µmol m−2 s−1) was examined for the induction and development of oat DH lines. Oat florets (26008) from 32 genotypes were pollinated with maize and treated with 2,4-dichlorophenoxyacetic acid. All the tested genotypes formed more haploid embryos when donor plants were grown in a greenhouse (9.4%) compared to a growth chamber (6.1%). The light intensity of 110 µmol m−2 s−1 during in vitro culture resulted in the highest percentage of embryo germination (38.9%), conversion into plants (36.4%) and DH line production (9.2%) when compared with lower light intensities (20, 40 and 70 µmol m−2 s−1). The results show that the growth conditions of the donor plant and light intensity during in vitro culture can affect the development of haploid embryos. This fact may have an impact on oat breeding programs using oat × maize crosses
Near threshold radiative 3 production in annihilation
We consider the final state in electron-positron
annihilation at cms energies not far from the threshold. Both initial and final
state radiations of the hard photon is considered but without interference
between them. The amplitude for the final state radiation is obtained by using
the effective Wess-Zumino-Witten Lagrangian for pion-photon interactions valid
for low energies. In real experiments energies are never such small that
and mesons would have negligible effect. So a phenomenological
Breit-Wigner factor is introduced in the final state radiation amplitude to
account for the vector mesons influence. Using radiative 3 production
amplitudes, a Monte Carlo event generator was developed which could be useful
in experimental studies.Comment: 15 pages, Latex, 6 figures. Misprints corrected. Version to be
published in JHE
Photometric brown-dwarf classification. I. A method to identify and accurately classify large samples of brown dwarfs without spectroscopy
Aims. We present a method, named photo-type, to identify and accurately
classify L and T dwarfs onto the standard spectral classification system using
photometry alone. This enables the creation of large and deep homogeneous
samples of these objects efficiently, without the need for spectroscopy.
Methods. We created a catalogue of point sources with photometry in 8 bands,
ranging from 0.75 to 4.6 microns, selected from an area of 3344 deg^2, by
combining SDSS, UKIDSS LAS, and WISE data. Sources with 13.0 < J < 17.5, and Y
- J > 0.8, were then classified by comparison against template colours of
quasars, stars, and brown dwarfs. The L and T templates, spectral types L0 to
T8, were created by identifying previously known sources with spectroscopic
classifications, and fitting polynomial relations between colour and spectral
type. Results. Of the 192 known L and T dwarfs with reliable photometry in the
surveyed area and magnitude range, 189 are recovered by our selection and
classification method. We have quantified the accuracy of the classification
method both externally, with spectroscopy, and internally, by creating
synthetic catalogues and accounting for the uncertainties. We find that,
brighter than J = 17.5, photo-type classifications are accurate to one spectral
sub-type, and are therefore competitive with spectroscopic classifications. The
resultant catalogue of 1157 L and T dwarfs will be presented in a companion
paper.Comment: 15 pages, 12 figures, Accepted for publication in A &
Markovian MC simulation of QCD evolution at NLO level with minimum k_T
We present two Monte Carlo algorithms of the Markovian type which solve the
modified QCD evolution equations at the NLO level. The modifications with
respect to the standard DGLAP evolution concern the argument of the strong
coupling constant alpha_S. We analyze the z - dependent argument and then the
k_T - dependent one. The evolution time variable is identified with the
rapidity. The two algorithms are tested to the 0.05% precision level. We find
that the NLO corrections in the evolution of parton momentum distributions with
k_T - dependent coupling constant are of the order of 10 to 20%, and in a small
x region even up to 30%, with respect to the LO contributions.Comment: 32 pages, 9 pdf figure
Crustal influx, indentation, ductile thinning and gravity redistribution in a continental wedge: Building a Moldanubian mantled gneiss dome with underthrust Saxothuringian material (European Variscan belt)
27 p.International audience[1] The contribution of lateral forces, vertical load, gravity redistribution and erosion to the origin of mantled gneiss domes in internal zones of orogens remains debated. In the Orlica-Snieznik dome (Moldanubian zone, European Variscan belt), the polyphase tectono-metamorphic history is initially characterized by the development of subhorizontal fabrics associated with medium- to high-grade metamorphic conditions in different levels of the crust. It reflects the eastward influx of a Saxothuringian-type passive margin sequence below a Teplá-Barrandian upper plate. The ongoing influx of continental crust creates a thick felsic orogenic root with HP rocks and migmatitic orthogneiss. The orogenic wedge is subsequently indented by the eastern Brunia microcontinent producing a multiscale folding of the orogenic infrastructure. The resulting kilometre-scale folding is associated with the variable burial of the middle crust in synforms and the exhumation of the lower crust in antiforms. These localized vertical exchanges of material and heat are coeval with a larger crustal-scale folding of the whole infrastructure generating a general uplift of the dome. It is exemplified by increasing metamorphic conditions and younging of 40Ar/39Ar cooling ages toward the extruded migmatitic subdomes cored by HP rocks. The vertical growth of the dome induces exhumation by pure shear-dominated ductile thinning laterally evolving to non-coaxial detachment faulting, while erosion feeds the surrounding sedimentary basins. Modeling of the Bouguer anomaly grid is compatible with crustal-scale mass transfers between a dense superstructure and a lighter infrastructure. The model implies that the Moldanubian Orlica-Snieznik mantled gneiss dome derives from polyphase recycling of Saxothuringian material
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