(Abridged) Using the Arecibo Observatory we have obtained neutral hydrogen (HI) absorption and emission spectral pairs in the direction of 26 background radio continuum sources in the vicinity of the Perseus molecular cloud. Strong absorption lines w
ere detected in all cases allowing us to estimate spin temperature (T_s) and optical depth for 107 individual Gaussian components along these lines of sight. Basic properties of individual HI clouds (spin temperature, optical depth, and the column density of the cold and warm neutral medium, CNM and WNM) in and around Perseus are very similar to those found for random interstellar lines of sight sampled by the Millennium HI survey. This suggests that the neutral gas found in and around molecular clouds is not atypical. However, lines of sight in the vicinity of Perseus have on average a higher total HI column density and the CNM fraction, suggesting an enhanced amount of cold HI relative to an average interstellar field. Our estimated optical depth and spin temperature are in stark contrast with the recent attempt at using Planck data to estimate properties of the optically thick HI. Only ~15% of lines of sight in our study have a column density weighted average spin temperature lower than 50 K, in comparison with >85% of Plancks sky coverage. The observed CNM fraction is inversely proportional to the optical-depth weighted average spin temperature, in excellent agreement with the recent numerical simulations by Kim et al. While the CNM fraction is on average higher around Perseus relative to a random interstellar field, it is generally low, 10-50%. This suggests that extended WNM envelopes around molecular clouds, and/or significant mixing of CNM and WNM throughout molecular clouds, are present and should be considered in the models of molecule and star formation.
We derive the CO-to-H2 conversion factor, X_CO = N(H2)/I_CO, across the Perseus molecular cloud on sub-parsec scales by combining the dust-based N(H2) data with the I_CO data from the COMPLETE Survey. We estimate an average X_CO ~ 3 x 10^19 cm^-2 K^-
1 km^-1 s and find a factor of ~3 variations in X_CO between the five sub-regions in Perseus. Within the individual regions, X_CO varies by a factor of ~100, suggesting that X_CO strongly depends on local conditions in the interstellar medium. We find that X_CO sharply decreases at Av < 3 mag but gradually increases at Av > 3 mag, with the transition occurring at Av where I_CO becomes optically thick. We compare the N(HI), N(H2), I_CO, and X_CO distributions with two models of the formation of molecular gas, a one-dimensional photodissociation region (PDR) model and a three-dimensional magnetohydrodynamic (MHD) model tracking both the dynamical and chemical evolution of gas. The PDR model based on the steady state and equilibrium chemistry reproduces our data very well but requires a diffuse halo to match the observed N(HI) and I_CO distributions. The MHD model generally matches our data well, suggesting that time-dependent effects on H2 and CO formation are insignificant for an evolved molecular cloud like Perseus. However, we find interesting discrepancies, including a broader range of N(HI), likely underestimated I_CO, and a large scatter of I_CO at small Av. These discrepancies likely result from strong compressions/rarefactions and density fluctuations in the MHD model.
We study the quantum Goos-H{a}nchen(GH) effect for wave-packet dynamics at a normal/superconductor (NS) interface. We find that the effect is amplified by a factor $(E_F/Delta)$, with $E_F$ the Fermi energy and $Delta$ the gap. Interestingly, the GH
effect appears only as a time delay $delta t$ without any lateral shift, and the corresponding delay length is about $(E_F/Delta)lambda_F$, with $lambda_F$ the Fermi wavelength. This makes the NS interface sticky when $Delta ll E_F$, since typically GH effects are of wavelength order. This sticky behavior can be further enhanced by a resonance mode in NSNS interface. Finally, for a large $Delta$, the resonance-mode effect makes a transition from Andreev to the specular electron reflection as the width of the sandwiched superconductor is reduced.
In the two body hadronic tau decays, such as tau->to K pi (eta)nu, vector mesons play important role. Belle and Babar measured hadronic invariant mass spectrum of tau -> K pi nu decay. To compare the spectrum with theoretical prediction, we develop t
he chiral Lagrangian with vector mesons in Kimura:2012nx. We compute the form factors of the hadronic tau decay taking account of the quantum corrections of Nambu Goldstone bosons. We also show how to renormalizethe divergence of the Feynman diagrams with arbitrary number of loops and determine the counterterms within one loop using background field method.In this report, we discuss the renormalization of Kimura:2012nx by considering the one loop Feynman diagrams.
Using pulsewidth data for 872 isolated radio pulsars we test the hypothesis that pulsars evolve through a progressive narrowing of the emission cone combined with progressive alignment of the spin and magnetic axes. The new data provide strong eviden
ce for the alignment over a time-scale of about 1 Myr with a log standard deviation of around 0.8 across the observed population. This time-scale is shorter than the time-scale of about 10 Myr found by previous authors, but the log standard deviation is larger. The results are inconsistent with models based on magnetic field decay alone or monotonic counter-alignment to orthogonal rotation. The best fits are obtained for a braking index parameter n_gamma approximately equal to 2.3, consistent the mean of the six measured values, but based on a much larger sample of young pulsars. The least-squares fitted models are used to predict the mean inclination angle between the spin and magnetic axes as a function of log characteristic age. Comparing these predictions to existing estimates it is found that the model in which pulsars are born with a random angle of inclination gives the best fit to the data. Plots of the mean beaming fraction as a function of characteristic age are presented using the best-fitting model parameters.
The recent experimental evaluation of the 18F(a,p)21Ne reaction rate, when considering its associated uncertainties, presented significant differences compared to the theoretical Hauser-Feshbach rate. This was most apparent at the low temperatures re
levant for He-shell burning in asymptotic giant branch (AGB) stars. Investigations into the effect on AGB nucleosynthesis revealed that the upper limit resulted in an enhanced production of 19F and 21Ne in carbon-rich AGB models, but the recommended and lower limits presented no differences from using the theoretical rate. This was the case for models spanning a range in metallicity from solar to [Fe/H] ~ -2.3. The results of this study are relevant for observations of F and C-enriched AGB stars in the Galaxy, and to the Ne composition of mainstream silicon carbide grains, that supposedly formed in the outflows of cool, carbon-rich giant stars. We discuss the mechanism that produces the extra F and summarize our main findings.
We present detailed models of low and intermediate-mass asymptotic giant branch (AGB) stars with and without the 18F(a,p)21Ne reaction included in the nuclear network, where the rate for this reaction has been recently experimentally evaluated for th
e first time. The lower and recommended measured rates for this reaction produce negligible changes to the stellar yields, whereas the upper limit of the rate affects the production of 19F and 21Ne. The stellar yields increase by ~50% to up to a factor of 4.5 for 19F, and by factors of ~2 to 9.6 for 21Ne. While the 18}F(a,p)21Ne reaction competes with 18O production, the extra protons released are captured by 18O to facilitate the 18O(p,a)15N(a,g)19F chain. The higher abundances of 19F obtained using the upper limit of the rate helps to match the [F/O] ratios observed in AGB stars, but only for large C/O ratios. Extra-mixing processes are proposed to help to solve this problem. Some evidence that the 18F(a,p)21Ne rate might be closer to its upper limit is provided by the fact that the higher calculated 21Ne/22Ne ratios in the He intershell provide an explanation for the Ne isotopic composition of silicon-carbide grains from AGB stars. This needs to be confirmed by future experiments of the 18F(a,p)21Ne reaction rate. The availability of accurate fluorine yields from AGB stars will be fundamental for interpreting observations of this element in carbon-enhanced metal-poor stars.
