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Register a new userGalaxies at Redshift ~0.5 Around Three Closely Spaced Quasar Sightlines
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We examine the relationship between galaxies and the intergalactic medium at z < 1 using a group of three closely spaced background QSOs with z_em ~1 observed with the Hubble Space Telescope. Using a new grouping algorithm, we identify groups of galaxies and absorbers across the three QSO sightlines that may be physically linked. There is an excess number of such groups compared to the number we expect from a random distribution of absorbers at a confidence level of 99.9%. The same search is performed with mock spectra generated using a hydrodynamic simulation, and we find the vast majority of such groups arise in dense regions of the simulation. We find that at z<0.5, groups in the simulation generally trace the large-scale filamentary structure as seen in the projected 2-d distribution of the HI column density in a ~30 h^-1 Mpc region. We discover a probable sub-damped Lyman-alpha system at z=0.557 showing strong, low-ionisation metal absorption lines. Previous analyses of absorption across the three sightlines attributed these metal lines to HI. We show that even when the new line identifications are taken into account, evidence remains for planar structures with scales of ~1 Mpc absorbing across the three sightlines. We identify a galaxy at z=0.2272 with associated metal absorption in two sightlines, each 200 kpc away. By constraining the star formation history of the galaxy, we show the gas causing this metal absorption may have been enriched and ejected by the galaxy during a burst of star formation 2 Gyr ago.
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A quantum-mechanical formulation of energy transfer between closely-spaced surfaces is given. Coupling between the two surfaces arises from the atomic dipole-dipole interaction involving transverse-photon exchange. The exchange of photons at resonance greatly enhances the radiation transfer. The spacing (distance) dependence is derived for the quantum well - quantum well situation. The interaction between two planar quantum wells, separated by a gap is found to be proportional to the 4th power of the wavelength-to-gapwidth ratio and to the radiation tunneling factor for the evanescent waves. Expressions for the net power transfer, in the near-field regime, from hot to cold surface for this case is given and evaluated for representative materials. Computational modeling of selected, but realizable, emitter and detector structures and materials shows the benefits of both near-field and resonance coupling (e.g., with 0.1 micron gaps).
We propose to use the flux variability of lensed quasar images induced by gravitational microlensing to measure the transverse peculiar velocity of lens galaxies over a wide range of redshift. Microlensing variability is caused by the motions of the observer, the lens galaxy (including the motion of the stars within the galaxy), and the source; hence, its frequency is directly related to the galaxys transverse peculiar velocity. The idea is to count time-event rates (e.g., peak or caustic crossing rates) in the observed microlensing light curves of lensed quasars that can be compared with model predictions for different values of the transverse peculiar velocity. To compensate for the large time-scale of microlensing variability we propose to count and model the number of events in an ensemble of gravitational lenses. We develop the methodology to achieve this goal and apply it to an ensemble of 17 lensed quasar systems. In spite of the shortcomings of the available data, we have obtained tentative estimates of the peculiar velocity dispersion of lens galaxies at $zsim 0.5$, $sigma_{rm pec}(0.53pm0.18)simeq(638pm213)sqrt{langle m rangle/0.3 M_odot} , rm km, s^{-1}$. Scaling at zero redshift we derive, $sigma_{rm pec}(0)simeq(491pm164) sqrt{langle m rangle/0.3 M_odot} , rm km, s^{-1}$, consistent with peculiar motions of nearby galaxies and with recent $N$-body nonlinear reconstructions of the Local Universe based on $Lambda$CDM. We analyze the different sources of uncertainty of the method and find that for the present ensemble of 17 lensed systems the error is dominated by Poissonian noise, but that for larger ensembles the impact of the uncertainty on the average stellar mass may be significant.
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In this paper, we present experimental techniques to resolve the closely spaced hyperfine levels of a weak transition by eliminating the residual/partial two-photon Doppler broadening and cross-over resonances in a wavelength mismatched double resonance spectroscopy. The elimination of the partial Doppler broadening is based on velocity induced population oscillation (VIPO) and velocity selective saturation (VSS) effect followed by the subtraction of the broad background of the two-photon spectrum. Since the VIPO and VSS effect are the phenomena for near zero velocity group atoms, the subtraction gives rise to Doppler-free peaks and the closely spaced hyperfine levels of the $6text{P}_{3/2}$ state in Rb are well resolved. The double resonance experiment is conducted on $5text{S}_{1/2}rightarrow5text{P}_{3/2}$ strong transition (at 780~nm) and $5text{S}_{1/2}rightarrow6text{P}_{3/2}$ weak transition (at 420~nm) at room temperature.
A quantum-mechanical formulation of energy transfer between closely spaced surfaces is given. Coupling between the two surfaces arises from the atomic dipole-dipole interaction involving transverse-photon exchange. The exchange of photons at resonance enhances the radiation transfer. The interaction between two surfaces, separated by a gap, is found to be dependent upon geometric, material, frequency, dipole, and temperature factors, along with a radiation-tunneling factor for the evanescent waves. The derived geometric term has a gap-spacing (distance) dependence that varies inversely as the second power for bulk samples to the inverse fourth power for the quantum well - quantum well case. Expressions for the net power transfer, in the near-field regime, from hot to cold surface for this case is given and evaluated for representative materials.
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