scholarly journals The outer rotation curve project with VERA: Trigonometric parallax of IRAS 05168+3634

2012 ◽  
Vol 8 (S289) ◽  
pp. 95-98
Author(s):  
Nobuyuki Sakai ◽  
Mareki Honma ◽  
Hiroyuki Nakanishi ◽  
Hirofumi Sakanoue ◽  
Tomoharu Kurayama ◽  
...  
Keyword(s):  
Proper Motion ◽  
Galactic Center ◽  
Rotation Velocity ◽  
Physical Parameters ◽  
Galactic Rotation ◽  
Trigonometric Parallax ◽  
Systemic Velocity ◽  
Local Standard ◽  
The Galaxy ◽  
Perseus Arm

AbstractWe present a measurement of the trigonometric parallax of IRAS 05168+3634 with VERA. The parallax is 0.532 ± 0.053 milli-arcsec, corresponding to a distance of 1.88+0.21−0.17 kpc. This is significantly closer than the previous distance estimate of 6 kpc based on a kinematic distance measurement. This drastic change in the source distance implies the need for revised values of not only the physical parameters of IRAS 05168+3634, but it also impies a different location in the Galaxy, placing it in the Perseus arm rather than the Outer arm. We also measured the proper motion of the source. A combination of the distance and proper motion with the systemic velocity yields a rotation velocity Θ = 227+9−11 km s−1 at the source position, assuming Θ0 = 240 km s−1. Our result, combined with previous VLBI results for six sources in the Perseus arm, indicates that the sources rotate systematically more slowly than the Galactic rotation velocity at the local standard of rest. In fact, we derive peculiar motions in the disk averaged over the seven sources in the Perseus arm of (Umean, Vmean) = (11 ± 3, −17 ± 3) km s−1, which indicates that these seven sources are moving systematically toward the Galactic Center and lag behind the overall Galactic rotation.

scholarly journals Mass distribution of the Galaxy with VERA

2012 ◽  
Vol 8 (S287) ◽  
pp. 421-422
Author(s):  
Nobuyuki Sakai ◽  
Mareki Honma ◽  
Hiroyuki Nakanishi ◽  
Hirofumi Sakanoue ◽  
Tomoharu Kurayama ◽  
...  
Keyword(s):  
Mass Distribution ◽  
Rotation Curve ◽  
Galactic Center ◽  
Rotation Velocity ◽  
Galactic Rotation ◽  
Proper Motions ◽  
Systemic Velocity ◽  
The Galaxy ◽  
Peculiar Motion ◽  
Perseus Arm

AbstractWe aim to reveal the mass distribution of the Galaxy based on a precise rotation curve constructed using VERA observations. We have been observing Galactic H2O masers with VERA. We here report one of the results of VERA for IRAS 05168+3634. The parallax is 0.532 ± 0.053 mas which corresponds to a distance of 1.88+0.21−0.17 kpc, and the proper motions are (μαcosδ, μδ) = (0.23 ± 1.07, −3.14 ± 0.28) mas yr−1. The distance is significantly smaller than the previous distance estimate of 6 kpc based on a kinematic distance. This drastic change places the source in the Perseus arm rather than in the Outer arm. Combination of the distance and the proper motions with the systemic velocity provides a rotation velocity of 227+9−11 km s−1 at the source assuming Θ0 = 240 km s−1. The result is marginally slower than the rotation velocity at LSR with ~ 1−σ significance, but consistent with previous VLBI results for six sources in the Perseus arm. We also show the averaged disk peculiar motion over the seven sources in the Perseus arm as (Umean, Vmean) = (11 ± 3, −17 ± 3) km s−1. It suggests that the seven sources in the Perseus arm are systematically moving toward the Galactic center, and lag behind the Galactic rotation with more than 3-σ significance.

scholarly journals Measurements of annual parallaxes and proper motions of the red supergiant S Per

2007 ◽  
Vol 3 (S242) ◽  
pp. 378-380 ◽  
Author(s):  
Yoshiharu Asaki ◽  
Shuji Deguchi ◽  
Hirishi Imai ◽  
Kazuya Hachisuka ◽  
Makoto Miyoshi ◽  
...  
Keyword(s):  
Water Vapor ◽  
Proper Motion ◽  
Galactic Center ◽  
Rotation Velocity ◽  
Galactic Rotation ◽  
The Sun ◽  
Proper Motions ◽  
Right Ascension

AbstractVLBI phase-referencing monitoring of water vapor masers around the red supergiant, S Per, was conducted over four years. We successfully obtained proper motions and an annual parallax of the masers and determined the distance to S Per of 2.51±0.09 kpc. The proper motion of the star itself was inferred from the maser proper motions, and it was −0.38 and −1.54 mas/yr for right ascension and declination, respectively. Assuming the distance from the sun to the Galactic center, R0, of 8.5 kpc and the rotation velocity around the sun, Θ0, of 220 km/s, the Galactic rotation velocity around S Per is 200 km/s.

scholarly journals The Massive Dark Corona Of Our Galaxy

1996 ◽  
Vol 173 ◽  
pp. 175-176
Author(s):  
K.C. Freeman
Keyword(s):  
Rotation Curve ◽  
Spiral Galaxies ◽  
Galactic Center ◽  
Galactic Disk ◽  
Galactic Rotation ◽  
Rotation Curves ◽  
Stellar Component ◽  
The Galaxy ◽  
Galactic Rotation Curve

From their rotation curves, most spiral galaxies appear to have massive dark coronas. The inferred masses of these dark coronas are typically 5 to 10 times the mass of the underlying stellar component. I will review the evidence that our Galaxy also has a dark corona. Our position in the galactic disk makes it difficult to measure the galactic rotation curve beyond about 20 kpc from the galactic center. However it does allow several other indicators of the total galactic mass out to very large distances. It seems clear that the Galaxy does indeed have a massive dark corona. The data indicate that the enclosed mass within radius R increases like M(R) ≈ R(kpc) × 1010M⊙, out to a radius of more than 100 kpc. The total galactic mass is at least 12 × 1011M⊙.

scholarly journals Lorentz Symmetry Group, Retardation, Intergalactic Mass Depletion and Mechanisms Leading to Galactic Rotation Curves

Symmetry ◽  
2020 ◽  
Vol 12 (10) ◽  
pp. 1693
Author(s):  
Asher Yahalom
Keyword(s):  
Dark Matter ◽  
Galactic Center ◽  
Field Approximation ◽  
Weak Field ◽  
Current Approach ◽  
Galactic Rotation ◽  
Theory Of Relativity ◽  
Detailed Model ◽  
The Galaxy ◽  
Retardation Effects

The general theory of relativity (GR) is symmetric under smooth coordinate transformations, also known as diffeomorphisms. The general coordinate transformation group has a linear subgroup denoted as the Lorentz group of symmetry, which is also maintained in the weak field approximation to GR. The dominant operator in the weak field equation of GR is thus the d’Alembert (wave) operator, which has a retarded potential solution. Galaxies are huge physical systems with dimensions of many tens of thousands of light years. Thus, any change at the galactic center will be noticed at the rim only tens of thousands of years later. Those retardation effects are neglected in the present day galactic modelling used to calculate rotational velocities of matter in the rims of the galaxy and surrounding gas. The significant differences between the predictions of Newtonian instantaneous action at a distance and observed velocities are usually explained by either assuming dark matter or by modifying the laws of gravity (MOND). In this paper, we will show that, by taking general relativity seriously without neglecting retardation effects, one can explain the radial velocities of galactic matter in the M33 galaxy without postulating dark matter. It should be stressed that the current approach does not require that velocities v are high; in fact, the vast majority of galactic bodies (stars, gas) are substantially subluminal—in other words, the ratio of vc≪1. Typical velocities in galaxies are 100 km/s, which makes this ratio 0.001 or smaller. However, one should consider the fact that every gravitational system, even if it is made of subluminal bodies, has a retardation distance, beyond which the retardation effect cannot be neglected. Every natural system, such as stars and galaxies and even galactic clusters, exchanges mass with its environment, for example, the sun loses mass through solar wind and galaxies accrete gas from the intergalactic medium. This means that all natural gravitational systems have a finite retardation distance. The question is thus quantitative: how large is the retardation distance? For the M33 galaxy, the velocity curve indicates that the retardation effects cannot be neglected beyond a certain distance, which was calculated to be roughly 14,000 light years; similar analysis for other galaxies of different types has shown similar results. We demonstrate, using a detailed model, that this does not require a high velocity of gas or stars in or out of the galaxy and is perfectly consistent with the current observational knowledge of galactic and extra galactic material content and dynamics.

scholarly journals Analysis of Low-and High-Resolution Observations of High-Velocity Clouds

1989 ◽  
Vol 120 ◽  
pp. 416-423
Author(s):  
Bart P. Wakker
Keyword(s):  
High Velocity ◽  
Galactic Center ◽  
Neutral Hydrogen ◽  
Current Status ◽  
Galactic Rotation ◽  
Single Model ◽  
Neutral Gas ◽  
The Galaxy ◽  
High Velocity Clouds ◽  
Distance Problem

For almost three decades neutral hydrogen moving at velocities unexplicable by galactic rotation has been observed. These so-called high-velocity clouds (HVCs) have been invoked as evidence for infall of neutral gas to the galaxy, as manifestations of a galactic fountain, as energy source for the formation of supershells, etc. No general consensus about their origin has presently been reached. However, it is becoming clear that no single model will suffice to explain all HVCs. A number of clouds may consist of material streaming toward the galactic center, as Mirabel (this conference) has advocated for several years, though their origin still remains unclear. A better understanding is mainly hampered by the fact that the distance remains unknown. An overview of the current status of the distance problem is given by van Woerden elsewhere in this volume.

scholarly journals Population and Evolution of Pulsating A-F Stars

1995 ◽  
Vol 164 ◽  
pp. 364-364
Author(s):  
Jiang Shiyang ◽  
Liu Yanying
Keyword(s):  
White Dwarfs ◽  
Main Sequence ◽  
Rotation Velocity ◽  
Light Variation ◽  
Galactic Rotation ◽  
Strongly Correlated ◽  
The Galaxy ◽  
The Mean ◽  
F Stars ◽  
Rotation Constant

Pulsating A-F variables include all the stellar types listed in teh Table, as well as the pulsating white dwarfs. Stars near the zero-age-main-sequence have faster rotation velocity, which slows as expected with age (Villata 1992) and a smaller amplitude of light variation, so we suggest that rotation velocity be considered in Population classifications. Also, in the Galaxy, the galactic rotation constant A is related to stellar age T by: A(kms−1kpc−1) = (−2.4±0.8)T(109yr) + (32±2) (Kharchenko 1992). The linear rotation velocity is also a function of the Z coordinate of the object inside the Galaxy: the mean Z-gradient is −10kms−1kpc−1 (Malakhova & Petrovskaya, 1992). Thus the population is strongly correlated with the rotation velocity and the evolutionary age.

The Rotation Curve from A-F Supergiants

1996 ◽  
Vol 169 ◽  
pp. 703-706
Author(s):  
D. M. Peterson ◽  
D. Slowik
Keyword(s):  
Total Mass ◽  
Rotation Curve ◽  
Galactic Center ◽  
Galactic Rotation ◽  
The Sun ◽  
Critical Information ◽  
New Class ◽  
The Galaxy ◽  
Local Distance

The Galactic rotation law provides critical information for estimating the distribution of mass in the Galaxy, for tying the distance of the Sun from the Galactic center to local distance scales, and, if determined over large enough distances, for estimating the total mass of the system and the amount of nonluminous matter present. Interior to the Sun velocities are well defined by observations of the ISM, particularly HI. These techniques are not available for points exterior to the Sun and we must rely on observations of velocities of objects whose distances can be estimated. Notable among these are the Cepheids (Pont et al 1994) and the combination of CO velocities and OB cluster distances (Brand & Blitz 1993) where the two are found to coexist. Adding a new class of objects, particularly bright, relatively common objects to this effort is of importance.

scholarly journals Filamentary Structures Near the Galactic Center

1989 ◽  
Vol 136 ◽  
pp. 243-263 ◽  
Author(s):  
F. Yusef-Zadeh
Keyword(s):  
Magnetic Field ◽  
Large Scale ◽  
Galactic Center ◽  
Galactic Plane ◽  
Galactic Rotation ◽  
Physical Interaction ◽  
Magnetic Structures ◽  
The Galaxy ◽  
Field Lines ◽  
The Magnetic Field

Recent studies of the Galactic center environment have revealed a wealth of new thermal and nonthermal features with unusual characteristics. A system of nonthermal filamentary structures tracing magnetic field lines are found to extend over 200pc in the direction perpendicular to the Galactic plane. Ionized structures, like nonthermal features, appear filamentary and show forbidden velocity fields in the sense of Galactic rotation and large line widths. Faraday rotation characteristics and the flat spectral index distributions of the nonthermal filaments suggest a mixture of thermal and nonthermal gas. Furthermore, the relative spatial distributions of the magnetic structures with respect to those of the ionized and molecular gas suggest a physical interaction between these two systems. In spite of numerous questions concerning the origin of the large-scale organized magnetic structures, the mechanism by which particles are accelerated to relativistic energies, and the source or sources of heating the dust and gas, recent studies have been able to distinguish the inner 200pc of the nucleus from the disk of the Galaxy in at least two more respects: (1) the recognition that the magnetic field has a large-scale structure and is strong, uniform and dynamically important; and (2) the physics of interstellar matter may be dominated by the poloidal component of the magnetic field.

scholarly journals Does Our Galaxy have a Massive Dark Corona?

1996 ◽  
Vol 169 ◽  
pp. 645-650
Author(s):  
K.C. Freeman
Keyword(s):  
Rotation Curve ◽  
Spiral Galaxies ◽  
Galactic Center ◽  
Galactic Disk ◽  
Galactic Rotation ◽  
Rotation Curves ◽  
The Galaxy ◽  
Galactic Rotation Curve

The rotation curves of spiral galaxies indicate that most of them have massive dark coronas, and it seems likely that our Galaxy also has a dark corona. Our position in the galactic disk makes it difficult to measure the galactic rotation curve beyond about 20 kpc from the galactic center, but it does allow us to use several other indicators of the total galactic mass out to very large distances. I will review some of these indicators. The conclusion is that the Galaxy does indeed have a massive dark corona: the data are consistent with the enclosed mass within radius R increasing like M(R) ≈ R(kpc) × 1010M⊙, out to a radius of more than 100 kpc, and a total galactic mass of at least 12 × 1011M⊙.

Modelling the Milky Way with Gaia-TGAS

2017 ◽  
Vol 12 (S330) ◽  
pp. 222-224
Author(s):  
Jason A. S. Hunt
Keyword(s):  
Angular Momentum ◽  
Milky Way ◽  
Solar Rotation ◽  
Rotation Velocity ◽  
Solar Neighbourhood ◽  
Galactic Centre ◽  
Galactic Rotation ◽  
Perseus Arm

AbstractI summarize two recent projects involving the Gaia-TGAS data. Firstly, I discuss a detection of a lack of disc stars in the Solar neighbourhood with velocities close to zero angular momentum. We use predictions of this effect to make a measurement of the Solar rotation velocity around the Galactic centre, and also of R0. Secondly, I discuss a detection of a group of stars with systematically high Galactic rotation velocity. We propose that it may be caused by the Perseus arm and compare the data with simulations.

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