3D Spectroscopy of Blue Compact Galaxies. Diagnostic Diagrams

Here we present the analysis of 3D spectroscopic data of three Blue Compact Galaxies (Mrk324, Mrk370, and IIIZw102). Each of the more than 22500 spectra obtained for each galaxy has been fitted by a single gaussian from which we have inferred the velocity dispersion (sigma), the peak intensity (Ipeak), and the central wavelength (lambda_c). The analysis shows that the sigma vs Ipeak diagrams look remarkably similar to those obtained for giant extragalactic HII regions. They all present a supersonic narrow horizontal band that extends across all the range of intensities and that result from the massive nuclear star-forming regions of every galaxy. The sigma vs Ipeak diagrams present also several inclined bands of lower intensity and an even larger sigma, arising from the large galactic volumes that surround the main central emitting knots. Here we also show that the sigma vs lambda_c and lambda_c vs Ipeak diagrams, are powerful tools able to unveil the presence of high and low mass stellar clusters, and thus allow for the possibility of inferring the star formation activity of distant galaxies, even if these are not spatially resolved.Comment: 15 pages, 3 figures, accepted for publication in The Astronomical Journa

RXJ 0921+4529: a binary quasar or gravitational lens?

We report the new spectroscopic observations of the gravitational lens RXJ 021+4529 with the multi-mode focal reducer SCORPIO of the SAO RAS 6-m telescope. The new spectral observations were compared with the previously observed spectra of components A and B of RXJ 0921+4529, i.e. the same components observed in different epochs. We found a significant difference in the spectrum between the components that cannot be explained with microlensing and/or spectral variation. We conclude that RXJ 0921+4529 is a binary quasar system, where redshifts of quasars A and B are 1.6535 +/- 0.0005 and 1.6625 +/- 0.0015, respectively.Comment: 6 pages, 5 figures, accepted for publication in The Astrophysical Journal Letter

Rephasing processes and quantum memory for light: reversibility issues and how to fix them

Time reversibility is absent from some recently proposed quantum memory protocols such as Absorption Frequency Comb (AFC). Focusing on AFC memory, we show that quantum efficiency and fidelity are reduced dramatically, as a consequence of non-reversibility, when the spectral width of the incoming signal approaches the memory bandwidth. Non-reversibility is revealed through spectral dispersion, giving rise to phase mismatching. We propose a modified AFC scheme that restores reversibility. This way, signals can be retrieved with excellent efficiency over the entire memory bandwidth. This study could be extended to other quantum memory rephasing schemes in inhomogeneously broadened absorbing media.Comment: 8 pages, 6 figures, was presented in 20th International Laser Physics Workshop (LPHYS'11), July 11-15, 2011, Sarajevo, Bosnia and Herzegovin

The Anti-Coincidence Detector for the GLAST Large Area Telescope

This paper describes the design, fabrication and testing of the Anti-Coincidence Detector (ACD) for the Gamma-ray Large Area Space Telescope (GLAST) Large Area Telescope (LAT). The ACD is LAT first-level defense against the charged cosmic ray background that outnumbers the gamma rays by 3-5 orders of magnitude. The ACD covers the top and 4 sides of the LAT tracking detector, requiring a total active area of ~8.3 square meters. The ACD detector utilizes plastic scintillator tiles with wave-length shifting fiber readout. In order to suppress self-veto by shower particles at high gamma-ray energies, the ACD is segmented into 89 tiles of different sizes. The overall ACD efficiency for detection of singly charged relativistic particles entering the tracking detector from the top or sides of the LAT exceeds the required 0.9997.Comment: 33 pages, 19 figure

Note on the role of friction-induced momentum conservation in the collisional drift wave instability

The collisional drift wave instability is reexamined taking into account the ion response in the direction parallel to the magnetic field lines, which appears due to friction with electrons and which can not be omitted in view of the momentum conservation. A modified instability threshold is obtained. In plasmas with dominant electron collisions with neutrals, the instability threshold is shifted towards higher frequencies, compared to the case of dominant electron collisions with ions. The difference between the two cases vanishes when the ion sound response is negligible, i.e., when the instability threshold disappears, and both ions and neutrals react to the electron friction in the same manner.Comment: 12 pages, 1 figur

Illuminating dark matter and primordial black holes with interstellar antiprotons

Interstellar antiproton fluxes can arise from dark matter annihilating or decaying into quarks or gluons that subsequently fragment into antiprotons. Evaporation of primordial black holes also can produce a significant antiproton cosmic-ray flux. Since the background of secondary antiprotons from spallation has an interstellar energy spectrum that peaks at \sim 2\gev and falls rapidly for energies below this, low-energy measurements of cosmic antiprotons are useful in the search for exotic antiproton sources. However, measurement of the flux near the earth is challenged by significant uncertainties from the effects of the solar wind. We suggest evading this problem and more effectively probing dark-matter signals by placing an antiproton spectrometer aboard an interstellar probe currently under discussion. We address the experimental challenges of a light, low-power-consuming detector, and present an initial design of such an instrument. This experimental effort could significantly increase our ability to detect, and have confidence in, a signal of exotic, nonstandard antiproton sources. Furthermore, solar modulation effects in the heliosphere would be better quantified and understood by comparing results to inverse modulated data derived from existing balloon and space-based detectors near the earth.Comment: 18 pages, 3 figure