scholarly journals More than just a wrinkle: a wave-like pattern in Ug versus Lz from Gaia data

2019 ◽  
Vol 490 (4) ◽  
pp. 5414-5423 ◽  
Author(s):  
Jennifer K S Friske ◽  
Ralph Schönrich
Keyword(s):  
Angular Momentum ◽  
Phase Shift ◽  
Radial Velocity ◽  
Galactic Plane ◽  
Wave Pattern ◽  
Short Wave ◽  
First Order ◽  
Gaia Dr1 ◽  
Weak Phase ◽  
Gaia Dr2

ABSTRACT We present a newly found wave-like pattern in mean Galactocentric radial velocity ${\overline{U}_\mathrm{ g}}$ versus guiding centre radius Rg or angular momentum Lz of stars in the RV subsample of Gaia DR2. The short-wave pattern has a wavelength of order $1.2 \, {\rm kpc}$ in Rg or $285 \, {\rm kpc}\, {\rm km}\, {\rm s}^{-1}$ in Lz. The pattern shows only weak changes with Galactocentric radius R and little change in strength in particular with the vertical energy Ez of the stars or the distance to the Galactic plane |z|. The pattern is to first order symmetric around the plane, i.e. has no significant odd terms in z. There is a weak phase shift with the pattern moving towards slightly lower Lz (i.e. trailing) with |z| and Ez. However, we observe a highly significant phase shift in Galactic azimuth ϕ, which is different for different peaks. The peak around $L_{z}\sim 2100 \, {\rm kpc}\, {\rm km}\, {\rm s}^{-1}$ only shows a weak change with ϕ, while the rest of the pattern shows a clearly detectable shift of $\text{d} L_{z}/\text{d} \phi = (200 \pm 22) \, {\rm kpc}\, {\rm km}\, {\rm s}^{-1}\, {\rm rad}^{-1}$. If we consider all peaks to belong to the same pattern, this would suggest a wavenumber m = 4. We further find that the wave-like pattern in Ug appears to be related to the ${\overline{W}}$ versus Lz pattern detected in Gaia DR1. A comparison of the ${\overline{U}_\mathrm{ g}}\!-\!L_{z}$ wave pattern with changes of ${\overline{U}_\mathrm{ g}}$ versus R, which have been previously discussed, suggests that the latter can be understood as just the ${\overline{U}_\mathrm{ g}}\!-\!L_{z}$ pattern washed out by blurring (i.e. orbital excursions around their guiding centre) of disc stars.

scholarly journals Gaia-DR2 extended kinematical maps

2020 ◽  
Vol 642 ◽  
pp. A95 ◽  
Author(s):  
Ž. Chrobáková ◽  
M. López-Corredoira ◽  
F. Sylos Labini ◽  
H.-F. Wang ◽  
R. Nagy
Keyword(s):  
Dark Matter ◽  
Radial Velocity ◽  
Rotation Curve ◽  
Milky Way ◽  
Galactic Plane ◽  
Dark Matter Halo ◽  
Disk Galaxies ◽  
Modified Newtonian Dynamics ◽  
Outer Disk ◽  
Gaia Dr2

Context. Recent statistical deconvolution methods have produced extended kinematical maps in a range of heliocentric distances that are a factor of two to three larger than those analysed in Gaia Collaboration (2018, A&A, 616, A11) based on the same data. Aims. In this paper, we use such maps to derive the rotation curve both in the Galactic plane and in off-plane regions and to analyse the density distribution. Methods. By assuming stationary equilibrium and axisymmetry, we used the Jeans equation to derive the rotation curve. Then we fit it with density models that include both dark matter and predictions of the MOND (Modified Newtonian dynamics) theory. Since the Milky Way exhibits deviations from axisymmetry and equilibrium, we also considered corrections to the Jeans equation. To compute such corrections, we ran N-body experiments of mock disk galaxies where the departure from equilibrium becomes larger as a function of the distance from the centre. Results. The rotation curve in the outer disk of the Milky Way that is constructed with the Jeans equation exhibits very low dependence on R and z and it is well-fitted both by dark matter halo and MOND models. The application of the Jeans equation for deriving the rotation curve, in the case of the systems that deviate from equilibrium and axisymmetry, introduces systematic errors that grow as a function of the amplitude of the average radial velocity. In the case of the Milky Way, we can observe that the amplitude of the radial velocity reaches ∼10% that of the azimuthal one at R ≈ 20 kpc. Based on this condition, using the rotation curve obtained from the Jeans equation to calculate the mass may overestimate its measurement.

scholarly journals Tracing Hercules in Galactic azimuth with Gaia DR2

2019 ◽  
Vol 632 ◽  
pp. A107 ◽  
Author(s):  
G. Monari ◽  
B. Famaey ◽  
A. Siebert ◽  
O. Bienaymé ◽  
R. Ibata ◽  
...  
Keyword(s):  
Angular Momentum ◽  
Radial Velocity ◽  
Major Axis ◽  
The Other ◽  
Data Release ◽  
Stellar Velocity ◽  
Pattern Speed ◽  
Gaia Dr2 ◽  
Lindblad Resonance ◽  
Exact Origin

The second data release of the Gaia mission has revealed, in stellar velocity and action space, multiple ridges, the exact origin of which is still debated. Recently, we demonstrated that a large Galactic bar with pattern speed 39 km s−1 kpc−1 creates most of the observed ridges. Among these ridges, the Hercules moving group would then be associated with orbits trapped at the co-rotation resonance of the bar. Here we show that a distinctive prediction of such a model is that the angular momentum of Hercules at the Sun’s radius must significantly decrease with increasing Galactocentric azimuth (i.e. when getting closer to the major axis of the bar). We show that this dependence of the angular momentum of trapped orbits on the azimuth on the other hand does not happen close to the outer Lindblad resonance of a faster bar, unless the orbital distribution is still far from phase-mixed, namely for a bar perturbation younger than ∼2 Gyr. Using Gaia DR2 and Bayesian distances from the StarHorse code, and tracing the average Galactocentric radial velocity as a function of angular momentum and azimuth, we show that the Hercules angular momentum changes significantly with azimuth as expected for the co-rotation resonance of a dynamically old large bar.

scholarly journals Numerical Solution of the Spinor-Spinor Bethe-Salpeter Equation in Functional Nonlinear Spinor Theory

1975 ◽  
Vol 30 (5) ◽  
pp. 656-671
Author(s):  
W. Bauhoff
Keyword(s):  
Angular Momentum ◽  
Excited State ◽  
Variational Method ◽  
Numerical Solution ◽  
High Precision ◽  
Nonlinear Spinor ◽  
Spinor Theory ◽  
First Order ◽  
Scalar Mesons ◽  
Functional Methods

AbstractThe mass eigenvalue equation for mesons in nonlinear spinor theory is derived by functional methods. In second order it leads to a spinorial Bethe-Salpeter equation. This is solved by a variational method with high precision for arbitrary angular momentum. The results for scalar mesons show a shift of the first order results, obtained earlier. The agreement with experiment is improved thereby. An excited state corresponding to the η' is found. A calculation of a Regge trajectory is included,too.

scholarly journals A Gaia DR2 view of the open cluster population in the Milky Way

2018 ◽  
Vol 618 ◽  
pp. A93 ◽  
Author(s):  
T. Cantat-Gaudin ◽  
C. Jordi ◽  
A. Vallenari ◽  
A. Bragaglia ◽  
L. Balaguer-Núñez ◽  
...  
Keyword(s):  
Stellar Evolution ◽  
Milky Way ◽  
Galactic Plane ◽  
Galactic Disk ◽  
Open Cluster ◽  
Open Clusters ◽  
Number Of Clusters ◽  
History Of ◽  
Gaia Dr2

Context. Open clusters are convenient probes of the structure and history of the Galactic disk. They are also fundamental to stellar evolution studies. The second Gaia data release contains precise astrometry at the submilliarcsecond level and homogeneous photometry at the mmag level, that can be used to characterise a large number of clusters over the entire sky. Aims. In this study we aim to establish a list of members and derive mean parameters, in particular distances, for as many clusters as possible, making use of Gaia data alone. Methods. We compiled a list of thousands of known or putative clusters from the literature. We then applied an unsupervised membership assignment code, UPMASK, to the Gaia DR2 data contained within the fields of those clusters. Results. We obtained a list of members and cluster parameters for 1229 clusters. As expected, the youngest clusters are seen to be tightly distributed near the Galactic plane and to trace the spiral arms of the Milky Way, while older objects are more uniformly distributed, deviate further from the plane, and tend to be located at larger Galactocentric distances. Thanks to the quality of Gaia DR2 astrometry, the fully homogeneous parameters derived in this study are the most precise to date. Furthermore, we report on the serendipitous discovery of 60 new open clusters in the fields analysed during this study.

scholarly journals QUANTUM LOGIC GATES USING q-DEFORMED OSCILLATORS

2006 ◽  
Vol 04 (02) ◽  
pp. 297-305 ◽  
Author(s):  
DEBASHIS GANGOPADHYAY ◽  
MAHENDRA NATH SINHA ROY
Keyword(s):  
Angular Momentum ◽  
Phase Shift ◽  
Quantum Logic ◽  
Logic Gates ◽  
Quantum Logic Gates ◽  
Single Qubit ◽  
Schwinger Mechanism

We show that quantum logic gates, viz. the single qubit Hadamard and Phase Shift gates, can also be realized using q-deformed angular momentum states constructed via the Jordan–Schwinger mechanism with two q-deformed oscillators.

scholarly journals Mikrowellenspektrum, Struktur, Dipolmoment und internes Hinderungspotential von Dimethyldisulfid

1965 ◽  
Vol 20 (12) ◽  
pp. 1676-1681 ◽  
Author(s):  
D. Sutter ◽  
H. Dreizler ◽  
H. D. Rudolph
Keyword(s):  
Perturbation Theory ◽  
Dipole Moment ◽  
Angular Momentum ◽  
Internal Rotation ◽  
Stark Effect ◽  
Order Perturbation ◽  
Frequency Range ◽  
First Order ◽  
Cross Terms ◽  
Second Order Perturbation Theory

The microwave spectra of CD3 —S —S —CD3 and CH3 —S —S—CH3 have been measured in the frequency range from 5.5 to 34 kmc/sec. From the six rotational constants an r0-structure has been calculated. STARK-effect measurements have been made for the 101 —110 and 202—211 rotational transitions of CH3—S—S—CH3. The dipole moment was calculated to be (1.985±0.01) Debye. An approximate value for the barrier to internal rotation of the two methyl tops is given, V3= (1.6±0.1) kcal. The calculation has been based on triplet splittings of the rotational lines using second order perturbation theory in the torsional wavefunctions and neglecting first order and cross terms in angular momentum.

A Radio over Fiber (RoF) Based Single Sideband Modulated Passive Optical Network (PON) Using Mach Zender Modulator Based on Different Electrical Phase Shifts

2018 ◽  
Vol 0 (0) ◽  
Author(s):  
Hilal Ahmad Sheikh ◽  
Anurag Sharma
Keyword(s):  
Phase Shift ◽  
Optical Network ◽  
Phase Shifts ◽  
Radio Over Fiber ◽  
Second Order ◽  
Passive Optical Network ◽  
First Order ◽  
Single Sideband ◽  
Hybrid Coupler ◽  
Shift Technique

AbstractThis research work provides an insight on a radio over fiber (RoF) based passive optical network (RoF-PON) utilizing two diverse electrical phase shifts with optical single sideband modulation (OSSB) by exploiting Mach Zender modulator. The influence of chromatic dispersion (CD) in PONs employing single mode fiber (SMF) is a noteworthy issue and should be limited. The two techniques of OSSB modulation, in view of the two distinct angles of the hybrid coupler are employed for the design and implementation of RoF-PON. The RF signal is partitioned into two ways equally before applying it to the dual drive Mach Zender modulator input, utilizing an electrical hybrid coupler that imparts two discrete phase shifts of 90° and 120° to generate two OSSB signals individually. By utilizing traditional OSSB technique having 90° phase shift, either of the first-order sideband (lower or upper first order) suppression occurs yet second-order harmonics are still existent in the system. As opposed to this, the OSSB technique using 120° phase shift causes the suppression of either lower first order and higher second order sideband or vice versa. When contrasted to the PON based on traditional technique (90° phase shift technique), the suppression of second order sideband in PON using 120° technique lessens the system CD. Hence the PON based on 120° phase shift technique has enhanced functionality in terms of system BER, received power and power losses as compared to that with traditional OSSB technique.

scholarly journals Prediction of stellar occultations by distant solar system bodies in the Gaia era

2017 ◽  
Vol 12 (S330) ◽  
pp. 382-385
Author(s):  
Josselin Desmars ◽  
Julio Camargo ◽  
Bruno Sicardy ◽  
Felipe Braga-Ribas ◽  
Roberto Vieira-Martins ◽  
...  
Keyword(s):  
Solar System ◽  
Orbit Determination ◽  
Proper Motions ◽  
Close Vicinity ◽  
Gaia Dr1 ◽  
Solar System Objects ◽  
Stellar Occultations ◽  
Solar System Bodies ◽  
Transneptunian Objects ◽  
Gaia Dr2

AbstractStellar occultations are a unique technique to access physical characteristics of distant solar system objects from the ground. They allow the measure of the size and the shape at kilometric level, the detection of tenuous atmospheres (few nanobars), and the investigation of close vicinity (satellites, rings) of Transneptunian objects and Centaurs. This technique is made successful thanks to accurate predictions of occultations. Accuracy of the predictions depends on the uncertainty in the position of the occulted star and the object's orbit. The Gaia stellar catalogue (Gaia Collaboration (2017)) now allows to get accurate astrometric stellar positions (to the mas level). The main uncertainty remains on the orbit. In this context, we now take advantage of the NIMA method (Desmars et al.(2015)) for the orbit determination and of the Gaia DR1 catalogue for the astrometry. In this document, we show how the orbit determination is improved by reducing current and some past observations with Gaia DR1. Moreover, we also use more than 45 past positive occultations observed in the 2009-2017 period to derive very accurate astrometric positions only depending on the position of the occulted stars (about few mas with Gaia DR1). We use the case of (10199) Chariklo as an illustration. The main limitation lies in the imprecision of the proper motions which is going to be solved by the Gaia DR2 release.

Gaia Photometric Catalogue: the calibration of the DR2 photometry

2018 ◽  
Vol 14 (A30) ◽  
pp. 466-470
Author(s):  
D. W. Evans ◽  
M. Riello ◽  
F. De Angeli ◽  
J. M. Carrasco ◽  
P. Montegriffo ◽  
...  
Keyword(s):  
Scientific Community ◽  
Photometric Data ◽  
Photometric System ◽  
Gaia Dr1 ◽  
System A ◽  
Data Release ◽  
Definition Of ◽  
High Level ◽  
Crucial Part ◽  
Gaia Dr2

AbstractGaia DR2 was released in April 2018 and contains a photometric catalogue of more than 1 billion sources. This release contains colour information in the form of integrated BP and RP photometry in addition to the latest G-band photometry. The level of uncertainty can be as good as 2 mmag with some residual systematics at the 10 mmag level. The addition of colour information greatly enhances the value of the photometric data for the scientific community. A high level overview of the photometric processing, with a focus on the improvements with respect to Gaia DR1, was given. The definition of the Gaia photometric system, a crucial part of the calibration of the photometry, was also explained. Finally, some of the photometric improvements expected for the next data release were described.

Radiation of short waves from the resonantly excited capillary–gravity waves

2016 ◽  
Vol 810 ◽  
pp. 5-24 ◽  
Author(s):  
M. Hirata ◽  
S. Okino ◽  
H. Hanazaki
Keyword(s):  
Solitary Wave ◽  
Solitary Waves ◽  
Gravity Waves ◽  
Wave Pattern ◽  
Short Wave ◽  
Bond Number ◽  
Linear Wave ◽  
Cnoidal Wave ◽  
Short Waves ◽  
Long Wave

Capillary–gravity waves resonantly excited by an obstacle (Froude number: $Fr=1$) are investigated by the numerical solution of the Euler equations. The radiation of short waves from the long nonlinear waves is observed when the capillary effects are weak (Bond number: $Bo<1/3$). The upstream-advancing solitary wave radiates a short linear wave whose phase velocity is equal to the solitary waves and group velocity is faster than the solitary wave (soliton radiation). Therefore, the short wave is observed upstream of the foremost solitary wave. The downstream cnoidal wave also radiates a short wave which propagates upstream in the depression region between the obstacle and the cnoidal wave. The short wave interacts with the long wave above the obstacle, and generates a second short wave which propagates downstream. These generation processes will be repeated, and the number of wavenumber components in the depression region increases with time to generate a complicated wave pattern. The upstream soliton radiation can be predicted qualitatively by the fifth-order forced Korteweg–de Vries equation, but the equation overestimates the wavelength since it is based on a long-wave approximation. At a large Bond number of $Bo=2/3$, the wave pattern has the rotation symmetry against the pattern at $Bo=0$, and the depression solitary waves propagate downstream.

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