Searching for molecular outflows in Hyper-Luminous Infrared Galaxies

We present constraints on the molecular outflows in a sample of five Hyper-Luminous Infrared Galaxies using Herschel observations of the OH doublet at 119 {\mu}m. We have detected the OH doublet in three cases: one purely in emission and two purely in absorption. The observed emission profile has a significant blueshifted wing suggesting the possibility of tracing an outflow. Out of the two absorption profiles, one seems to be consistent with the systemic velocity while the other clearly indicates the presence of a molecular outflow whose maximum velocity is about ~1500 km/s. Our analysis shows that this system is in general agreement with previous results on Ultra-luminous Infrared Galaxies and QSOs, whose outflow velocities do not seem to correlate with stellar masses or starburst luminosities (star formation rates). Instead the galaxy outflow likely arises from an embedded AGN.Comment: Accepted for publication in MNRAS. 13 pages, 11 figures, 4 table

Molecular Gas, Dust and Star Formation in Galaxies: II. Dust properties and scalings in \sim\ 1600 nearby galaxies

We aim to characterize the relationship between dust properties. We also aim to provide equations to estimate accurate dust properties from limited observational datasets. We assemble a sample of 1,630 nearby (z<0.1) galaxies-over a large range of Mstar, SFR - with multi-wavelength observations available from wise, iras, planck and/or SCUBA. The characterization of dust emission comes from SED fitting using Draine & Li dust models, which we parametrize using two components (warm and cold ). The subsample of these galaxies with global measurements of CO and/or HI are used to explore the molecular and/or atomic gas content of the galaxies. The total Lir, Mdust and dust temperature of the cold component (Tc) form a plane that we refer to as the dust plane. A galaxy's sSFR drives its position on the dust plane: starburst galaxies show higher Lir, Mdust and Tc compared to Main Sequence and passive galaxies. Starburst galaxies also show higher specific Mdust (Mdust/Mstar) and specific Mgas (Mgas/Mstar). The Mdust is more closely correlated with the total Mgas (atomic plus molecular) than with the individual components. Our multi wavelength data allows us to define several equations to estimate Lir, Mdust and Tc from one or two monochromatic luminosities in the infrared and/or sub-millimeter. We estimate the dust mass and infrared luminosity from a single monochromatic luminosity within the R-J tail of the dust emission, with errors of 0.12 and 0.20dex, respectively. These errors are reduced to 0.05 and 0.10 dex, respectively, if the Tc is used. The Mdust is correlated with the total Mism (Mism \propto Mdust^0.7). For galaxies with Mstar 8.5<log(Mstar/Msun) < 11.9, the conversion factor \alpha_850mum shows a large scatter (rms=0.29dex). The SF mode of a galaxy shows a correlation with both the Mgass and Mdust: high Mdust/Mstar galaxies are gas-rich and show the highest SFRs.Comment: 24 pages, 28 figures, 6 tables, Accepted for publication in A&

Full time nonexponential decay in double-barrier quantum structures

We examine an analytical expression for the survival probability for the time evolution of quantum decay to discuss a regime where quantum decay is nonexponential at all times. We find that the interference between the exponential and nonexponential terms of the survival amplitude modifies the usual exponential decay regime in systems where the ratio of the resonance energy to the decay width, is less than 0.3. We suggest that such regime could be observed in semiconductor double-barrier resonant quantum structures with appropriate parameters.Comment: 6 pages, 5 figure

Physical mechanisms of interface-mediated intervalley coupling in Si

The conduction band degeneracy in Si is detrimental to quantum computing based on spin qubits, for which a nondegenerate ground orbital state is desirable. This degeneracy is lifted at an interface with an insulator as the spatially abrupt change in the conduction band minimum leads to intervalley scattering. We present a theoretical study of the interface-induced valley splitting in Si that provides simple criteria for optimal fabrication parameters to maximize this splitting. Our work emphasizes the relevance of different interface-related properties to the valley splitting.Comment: 4 pages, revised versio

Strain control of superlattice implies weak charge-lattice coupling in La0.5_{0.5}Ca0.5_{0.5}MnO3_3

We have recently argued that manganites do not possess stripes of charge order, implying that the electron-lattice coupling is weak [Phys Rev Lett \textbf{94} (2005) 097202]. Here we independently argue the same conclusion based on transmission electron microscopy measurements of a nanopatterned epitaxial film of La$_{0.5}$Ca$_{0.5}$MnO$_3$. In strain relaxed regions, the superlattice period is modified by 2-3% with respect to the parent lattice, suggesting that the two are not strongly tied.Comment: 4 pages, 4 figures It is now explained why the work provides evidence to support weak-coupling, and rule out charge orde

Time scale of forerunners in quantum tunneling

The forerunners preceding the main tunneling signal of the wave created by a source with a sharp onset or by a quantum shutter, have been generally associated with over-the-barrier (non-tunneling) components. We demonstrate that, while this association is true for distances which are larger than the penetration lenght, for smaller distances the forerunner is dominated by under-the-barrier components. We find that its characteristic arrival time is inversely proportional to the difference between the barrier energy and the incidence energy, a tunneling time scale different from both the phase time and the B\"uttiker-Landauer (BL) time.Comment: Revtex4, 14 eps figure