The interaction between jets and clouds in the 3CR galaxies

From the HST/WFPC2 3CR Snapshot Survey, data taken with the filter F555W, F702W and narrow-ramp, a set of galaxies with noticeable extended structure were selected (e.g. 3C 79, 3C 135, 3C 234, etc). All of these objects show large regions of [OIII] λ 5007˚A emission (narrow ramp filter) and the broad-band filters data show similar structures indicating the presence of strong emission in several lines over these regions. The morphology observed seems to be related (e.g. same position angle, direct overlapping or similar shape) with the radio-jet. For some candidates with these properties GMOS/Gemini spectroscopy was taken. These data (both HST direct imaging and Gemini spectroscopy) can be tested with diagnostic diagrams and total UV photons budget to understand the source of energy that is ionizing the gas. This source of ionization was commonly believed to be the UV photons emitted by the powerful active galactic nuclei (AGN), but several of these objects show clearly that shocks produced by the radio jet are the main cause of the observed gas line emission. We show in this work, the results obtained over some of these radio-galaxies: 3C 135, 3C 180, 3C 234 and 3C 284.Fil: Hägele, G. F.. Universidad Autónoma de Madrid; EspañaFil: Feinstein Baigorri, Carlos. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas; ArgentinaFil: Macchetto, D. F.. Space Telescope Science Institute; Estados UnidosFil: Montero, F.. Consejo Nacional de Investigaciónes Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Astronomía y Física del Espacio. - Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Astronomía y Física del Espacio; Argentin

Proof of the cases p≤7p \leq 7 of the Lieb-Seiringer formulation of the Bessis-Moussa-Villani conjecture

It is shown that the polynomial $\lambda(t) = {\rm Tr}[(A + tB)^p]$ has nonnegative coefficients when $p \leq 7$ and A and B are any two complex positive semidefinite $n \times n$ matrices with arbitrary $n$. This proofs a general nontrivial case of the Lieb-Seiringer formulation of the Bessis-Moussa-Villani conjecture which is a long standing problem in theoretical physics.Comment: 5 pages; typos corrected; accepted for publication in Journal of Statistical Physic

Towards bose-einstein condensation of semiconductor excitons: The biexciton polarization effect

We theoretically predict a strong influence of stimulated exciton-exciton scattering on semiconductor luminescence. The stimulated scattering causes circularly polarized instead of unpolarized emission at the biexciton emission line in a degenerate gas of partly spin polarized excitons. The biexciton polarization effect increases with increasing exciton densities and decreasing temperatures and approaches almost unity in the ultimate case of Bose-Einstein condensation. Time- and polarization-resolved luminescence measurements evidence the biexciton polarization effect both in ZnSe and GaAs quantum wells. © 2009 The American Physical Society

Transient terahertz spectroscopy of excitons and unbound carriers in quasi two-dimensional electron-hole gases

We report a comprehensive experimental study and detailed model analysis of the terahertz dielectric response and density kinetics of excitons and unbound electron-hole pairs in GaAs quantum wells. A compact expression is given, in absolute units, for the complex-valued terahertz dielectric function of intra-excitonic transitions between the 1s and higher-energy exciton and continuum levels. It closely describes the terahertz spectra of resonantly generated excitons. Exciton ionization and formation are further explored, where the terahertz response exhibits both intra-excitonic and Drude features. Utilizing a two-component dielectric function, we derive the underlying exciton and unbound pair densities. In the ionized state, excellent agreement is found with the Saha thermodynamic equilibrium, which provides experimental verification of the two-component analysis and density scaling. During exciton formation, in turn, the pair kinetics is quantitatively described by a Saha equilibrium that follows the carrier cooling dynamics. The terahertz-derived kinetics is, moreover, consistent with time-resolved luminescence measured for comparison. Our study establishes a basis for tracking pair densities via transient terahertz spectroscopy of photoexcited quasi-two-dimensional electron-hole gases.Comment: 14 pages, 8 figures, final versio

Temperature-dependent electron Landé g factor and the interband matrix element of GaAs

Very high precision measurements of the electron Landé g factor in GaAs are presented using spin-quantum beat spectroscopy at low excitation densities and temperatures ranging from 2.6 to 300 K. In colligation with available data for the temperature-dependent effective mass temperature dependence of the interband matrix element within a common five-level k⋅p theory can model both parameters consistently. A strong decrease in the interband matrix element with increasing temperature consistently closes a long lasting gap between experiment and theory and substantially improves the modeling of both parameters. © 2009 The American Physical Society

Electron spin orientation under in-plane optical excitation in GaAs quantum wells

We study the optical orientation of electron spins in GaAs/AlGaAs quantum wells for excitation in the growth direction and for in-plane excitation. Time- and polarization-resolved photoluminescence excitation measurements show, for resonant excitation of the heavy-hole conduction band transition, a negligible degree of electron spin polarization for in-plane excitation and nearly 100% for excitation in the growth direction. For resonant excitation of the light-hole conduction band transition, the excited electron spin polarization has the same (opposite) direction for in-plane excitation (in the growth direction) as for excitation into the continuum. The experimental results are well explained by an accurate multiband theory of excitonic absorption taking fully into account electron-hole Coulomb correlations and heavy-hole light-hole coupling.Comment: 10 pages, 4 figures, final versio

The interaction between jets and clouds in the 3CR galaxies

From the HST/WFPC2 3CR Snapshot Survey, data taken with the filter F555W, F702W and narrow-ramp, a set of galaxies with noticeable extended structure were selected (e.g. 3C 79, 3C 135, 3C 234, etc). All of these objects show large regions of [OIII] λ 5007˚A emission (narrow ramp filter) and the broad-band filters data show similar structures indicating the presence of strong emission in several lines over these regions. The morphology observed seems to be related (e.g. same position angle, direct overlapping or similar shape) with the radio-jet. For some candidates with these properties GMOS/Gemini spectroscopy was taken. These data (both HST direct imaging and Gemini spectroscopy) can be tested with diagnostic diagrams and total UV photons budget to understand the source of energy that is ionizing the gas. This source of ionization was commonly believed to be the UV photons emitted by the powerful active galactic nuclei (AGN), but several of these objects show clearly that shocks produced by the radio jet are the main cause of the observed gas line emission. We show in this work, the results obtained over some of these radio-galaxies: 3C 135, 3C 180, 3C 234 and 3C 284.Facultad de Ciencias Astronómicas y Geofísica

The interaction between jets and clouds in the 3CR galaxies

From the HST/WFPC2 3CR Snapshot Survey, data taken with the filter F555W, F702W and narrow-ramp, a set of galaxies with noticeable extended structure were selected (e.g. 3C 79, 3C 135, 3C 234, etc). All of these objects show large regions of [OIII] λ 5007˚A emission (narrow ramp filter) and the broad-band filters data show similar structures indicating the presence of strong emission in several lines over these regions. The morphology observed seems to be related (e.g. same position angle, direct overlapping or similar shape) with the radio-jet. For some candidates with these properties GMOS/Gemini spectroscopy was taken. These data (both HST direct imaging and Gemini spectroscopy) can be tested with diagnostic diagrams and total UV photons budget to understand the source of energy that is ionizing the gas. This source of ionization was commonly believed to be the UV photons emitted by the powerful active galactic nuclei (AGN), but several of these objects show clearly that shocks produced by the radio jet are the main cause of the observed gas line emission. We show in this work, the results obtained over some of these radio-galaxies: 3C 135, 3C 180, 3C 234 and 3C 284.Facultad de Ciencias Astronómicas y Geofísica

Traces of stimulated bosonic exciton-scattering in semiconductor luminescence

We observe signatures of stimulated bosonic scattering of excitons, a precursor of Bose-Einstein-Condensation (BEC), in the photoluminescence of semiconductor quantum wells. The optical decay of a spinless molecule of two excitons (biexciton) into an exciton and a photon with opposite angular momenta is subject to bosonic enhancement in the presence of other excitons. In a spin polarized gas of excitons the bosonic enhancement breaks the symmetry of two equivalent decay channels leading to circularly polarized luminescence of the biexciton with the sign opposite to the excitonic luminescence. Comparison of experiment and many body theory proves stimulated scattering of excitons, but excludes the presence of a fully condensed BEC-like state.Comment: 5 page

The jet-cloud interaction in 3CR galaxies: Preliminary results in four galaxies

We present preliminary results of the Gemini/GMOS longslit spectra for four radiogalaxies: 3C 135, 3C 180, 3C 234 and 3C 284. These objects are a subsample of a set of galaxies with noticeable extended structure selected from the HST/WFPC2 3CR Snapshot Survey, data taken with the filters F555W, F702W and narrow-ramp. All of these objects show large regions of [Oiii]5007 emission (narrow ramp filter) and the broad-band filters data show similar structures indicating the presence of strong emission in several lines over these regions. The morphology observed seems to be related (e.g. same position angle, direct overlapping or similar shape) with the radio-jet. For some candidates with these properties GMOS/Gemini spectroscopy was taken. These data (both HST direct imaging and Gemini spectroscopy) can be tested with diagnostic diagrams and total UV photons budget to understand the source of energy that is ionizing the gas. This source of ionization was commonly believed to be the UV photons emitted by the powerful AGN, but several of these objects shows clearly that shocks produce by the radio jet are the main cause of the observed gas line emission.Facultad de Ciencias Astronómicas y Geofísica