Reddening and metallicity maps of the Milky Way bulge from VVV and 2MASS II. The complete high resolution extinction map and implications for Bulge studies

We use the Vista Variables in the Via Lactea (VVV) ESO public survey data to measure extinction values in the complete area of the Galactic bulge covered by the survey at high resolution. We derive reddening values using the method described in Paper I. This is based on measuring the mean (J-Ks) color of red clump giants in small subfields of 2' to 6' in the following bulge area: -10.3<b<+5.1 and -10<l<+10.4. To determine the reddening values E(J-Ks) for each region, we measure the RC color and compare it to the (J-Ks) color of RC stars measured in Baade's window, for which we adopt E(B-V)=0.55. This allows us to construct a reddening map sensitive to small scale variations minimizing the problems arising from differential extinction. The significant reddening variations are clearly observed on spatial scales as small as 2'. We find a good agreement between our extinction measurements and Schlegel maps in the outer bulge, but, as already stated in the literature the Schlegel maps are not reliable for regions within |b| < 6. In the inner regions we compare our results with maps derived from DENIS and Spitzer surveys. While we find good agreement with other studies in the corresponding overlapping regions, our extinction map has better quality due to both higher resolution and a more complete spatial coverage in the Bulge. We investigate the importance of differential reddening and demonstrate the need for high resolution extinction maps for detailed studies of Bulge stellar populations and structure. The extinction variations on scales of up to 2'-6', must be taken into account when analysing the stellar populations of the Bulge.Comment: Accepted for publication in A&

Diffusion and activation of n-type dopants in germanium

The diffusion and activation of $n$-type impurities (P and As) implanted into $p$-type Ge(100) substrates were examined under various dose and annealing conditions. The secondary ion mass spectrometry profiles of chemical concentrations indicated the existence of a sufficiently high number of impurities with increasing implanted doses. However, spreading resistance probe profiles of electrical concentrations showed electrical concentration saturation in spite of increasing doses and indicated poor activation of As relative to P in Ge. The relationships between the chemical and electrical concentrations of P in Ge and Si were calculated, taking into account the effect of incomplete ionization. The results indicated that the activation of P was almost the same in Ge and Si. The activation ratios obtained experimentally were similar to the calculated values, implying insufficient degeneration of Ge. The profiles of P in Ge substrates with and without damage generated by Ge ion implantation were compared, and it was clarified that the damage that may compensate the activated $n$-type dopants has no relationship with the activation of P in Ge.Comment: 6 pages, 4 figure

Statistical atmospheric downscaling for rainfall estimation in Kyushu Island, Japan

International audienceThe present paper develops linear regression models based on singular value decomposition (SVD) with the aim of downscaling atmospheric variables statistically to estimate average rainfall in the Chikugo River Basin, Kyushu Island, southern Japan, on a 12-hour basis. Models were designed to take only significantly correlated areas into account in the downscaling procedure. By using particularly precipitable water in combination with wind speeds at 850 hPa, correlation coefficients between observed and estimated precipitation exceeding 0.8 were reached. The correlations exhibited a seasonal variation with higher values during autumn and winter than during spring and summer. The SVD analysis preceding the model development highlighted three important features of the rainfall regime in southern Japan: (1) the so-called Bai-u front which is responsible for the majority of summer rainfall, (2) the strong circulation pattern associated with autumn rainfall, and (3) the strong influence of orographic lifting creating a pronounced east-west gradient across Kyushu Island. Results confirm the feasibility of establishing meaningful statistical relationships between atmospheric state and basin rainfall even at time scales of less than one day. Keywords: atmospheric downscaling, precipitation, rainfall, singular value decomposition, southern Japa

Origin of the reduced exchange bias in epitaxial FeNi(111)/CoO(111) bilayer

We have employed Soft and Hard X-ray Resonant Magnetic Scattering and Polarised Neutron Diffraction to study the magnetic interface and the bulk antiferromagnetic domain state of the archetypal epitaxial Ni$_{81}$Fe$_{19}$(111)/CoO(111) exchange biased bilayer. The combination of these scattering tools provides unprecedented detailed insights into the still incomplete understanding of some key manifestations of the exchange bias effect. We show that the several orders of magnitude difference between the expected and measured value of exchange bias field is caused by an almost anisotropic in-plane orientation of antiferromagnetic domains. Irreversible changes of their configuration lead to a training effect. This is directly seen as a change in the magnetic half order Bragg peaks after magnetization reversal. A 30 nm size of antiferromagnetic domains is extracted from the width the (1/2 1/2 1/2) antiferromagnetic magnetic peak measured both by neutron and x-ray scattering. A reduced blocking temperature as compared to the measured antiferromagnetic ordering temperature clearly corresponds to the blocking of antiferromagnetic domains. Moreover, an excellent correlation between the size of the antiferromagnetic domains, exchange bias field and frozen-in spin ratio is found, providing a comprehensive understanding of the origin of exchange bias in epitaxial systems.Comment: 8 pages, 5 figures, submitte

Field induced long-range-ordering in an S=1 quasi-one-dimensional Heisenberg antiferromagnet

We have measured the heat capacity and magnetization of the spin one one-dimensional Heisenberg antiferromagnet NDMAP and constructed a magnetic field versus temperature phase diagram. We found a field induced long-range magnetic ordering. We have been successful in explaining the phase diagram theoretically.Comment: 6 pages, 18 figure

Spin-Reorientation Transition of Field-Induced Magnetic Ordering Phases in the Anisotropic Haldane System

A possible spin-reorientation transition in field-induced magnetic ordering phases of the S=1 Haldane system with large easy-plane anisotropy is proposed, using an effective Lagrangian formalism as well as the density matrix renormalization group method. Such a spin-reorientation transition is predicted in the case where the applied magnetic field is inclined from the easy axis of the anisotropy. We point out that this transition has a close connection with a variation of the order parameter even at zero temperature, although it is different from a quantum analog of the so-called spin-flop transition proposed for the system having a strong easy axis anisotropy. In connection with a novel phase observed recently in the Haldane system at high fields, we discuss possible implications for the field-induced magnetic ordering.Comment: 14 pages, 7 figure

Finite Size Scaling for Low Energy Excitations in Integer Heisenberg Spin Chains

In this paper we study the finite size scaling for low energy excitations of $S=1$ and $S=2$ Heisenberg chains, using the density matrix renormalization group technique. A crossover from $1/L$ behavior (with $L$ as the chain length) for medium chain length to $1/L^2$ scaling for long chain length is found for excitations in the continuum band as the length of the open chain increases. Topological spin $S=1/2$ excitations are shown to give rise to the two lowest energy states for both open and periodic $S=1$ chains. In periodic chains these two excitations are ``confined'' next to each other, while for open chains they are two free edge 1/2 spins. The finite size scaling of the two lowest energy excitations of open $S=2$ chains is determined by coupling the two free edge $S=1$ spins. The gap and correlation length for $S=2$ open Heisenberg chains are shown to be 0.082 (in units of the exchange $J$) and 47, respectively.Comment: 4 pages (two column), PS file, to be appear as a PRB Brief Repor

Low temperature acoustic properties of amorphous silica and the Tunneling Model

Internal friction and speed of sound of a-SiO(2) was measured above 6 mK using a torsional oscillator at 90 kHz, controlling for thermal decoupling, non-linear effects, and clamping losses. Strain amplitudes e(A) = 10^{-8} mark the transition between the linear and non-linear regime. In the linear regime, excellent agreement with the Tunneling Model was observed for both the internal friction and speed of sound, with a cut-off energy of E(min) = 6.6 mK. In the non-linear regime, two different behaviors were observed. Above 10 mK the behavior was typical for non-linear harmonic oscillators, while below 10 mK a different behavior was found. Its origin is not understood.Comment: 1 tex file, 6 figure

The astrometric Gaia-FUN-SSO observation campaign of 99 942 Apophis

Astrometric observations performed by the Gaia Follow-Up Network for Solar System Objects (Gaia-FUN-SSO) play a key role in ensuring that moving objects first detected by ESA's Gaia mission remain recoverable after their discovery. An observation campaign on the potentially hazardous asteroid (99 942) Apophis was conducted during the asteroid's latest period of visibility, from 12/21/2012 to 5/2/2013, to test the coordination and evaluate the overall performance of the Gaia-FUN-SSO . The 2732 high quality astrometric observations acquired during the Gaia-FUN-SSO campaign were reduced with the Platform for Reduction of Astronomical Images Automatically (PRAIA), using the USNO CCD Astrograph Catalogue 4 (UCAC4) as a reference. The astrometric reduction process and the precision of the newly obtained measurements are discussed. We compare the residuals of astrometric observations that we obtained using this reduction process to data sets that were individually reduced by observers and accepted by the Minor Planet Center. We obtained 2103 previously unpublished astrometric positions and provide these to the scientific community. Using these data we show that our reduction of this astrometric campaign with a reliable stellar catalog substantially improves the quality of the astrometric results. We present evidence that the new data will help to reduce the orbit uncertainty of Apophis during its close approach in 2029. We show that uncertainties due to geolocations of observing stations, as well as rounding of astrometric data can introduce an unnecessary degradation in the quality of the resulting astrometric positions. Finally, we discuss the impact of our campaign reduction on the recovery process of newly discovered asteroids.Comment: Accepted for publication in A&

Experimental electronic heat capacities of α−\alpha- and δ−\delta-Plutonium; heavy-fermion physics in an element

We have measured the heat capacities of $\delta-$Pu$_{0.95}$Al$_{0.05}$ and $\alpha-$Pu over the temperature range 2-303 K. The availability of data below 10 K plus an estimate of the phonon contribution to the heat capacity based on recent neutron-scattering experiments on the same sample enable us to make a reliable deduction of the electronic contribution to the heat capacity of $\delta-$Pu$_{0.95}$Al$_{0.05}$; we find $\gamma = 64 \pm 3$ mJK$^{-2}$mol$^{-1}$ as $T \to 0$. This is a factor $\sim 4$ larger than that of any element, and large enough for $\delta-$Pu$_{0.95}$Al$_{0.05}$ to be classed as a heavy-fermion system. By contrast, $\gamma = 17 \pm 1$ mJK$^{-2}$mol$^{-1}$ in $\alpha-$Pu. Two distinct anomalies are seen in the electronic contribution to the heat capacity of $\delta-$Pu$_{0.95}$Al$_{0.05}$, one or both of which may be associated with the formation of the $\alpha'-$ martensitic phase. We suggest that the large $\gamma$-value of $\delta-$Pu$_{0.95}$Al$_{0.05}$ may be caused by proximity to a quantum-critical point.Comment: 4 pages, 4 figure