scholarly journals On Non-Spherical Models for Spiral Galaxy Gravitation Potential Yielding Flat Rotation Curve

2021 ◽  
Author(s):  
Swagatam Sen
Keyword(s):  
Spiral Galaxies ◽  
Galactic Plane ◽  
Rotation Velocity ◽  
Radial Symmetry ◽  
Galactic Centre ◽  
Spherically Symmetric ◽  
Annular Disk ◽  
Spherical Models ◽  
The Galaxy ◽  
Flat Rotation Curve

Abstract A two component model of gravitation potential for spiral galaxies has been proposed which couples a spherically symmetric component with a second component that observes planar radial symmetry on the galactic plane and vanishes outside an annular disk beyond the edge of galaxy's effective radius. It is shown that such a model for potential satisfying Poisson Equation would produce rotation velocity curve towards the edge of the galaxy which is flat over distance from the galactic centre. This relationship, which is experimentally observed in many spiral galaxies, is shown as a consequence of classical understanding of gravity and specific symmetry of the gravitational potential without any extrinsic requirement of dark matter. It is also demonstrated that this potential directly yields a relationship between inner mass of the galaxy and terminal rotation velocity, which has been empirically observed and known as Baryonic Tully-Fisher relations. Furthermore a direct test has been proposed for experimental verification of the proposed theory.

scholarly journals A Derivation of Flat Rotation Curve of Spiral Galaxies and Baryonic Tully-Fisher Relation

2020 ◽  
Author(s):  
Swagatam Sen
Keyword(s):  
Laplace Equation ◽  
Spiral Galaxy ◽  
Rotation Curve ◽  
Spiral Galaxies ◽  
Rotation Velocity ◽  
Alternative Solution ◽  
The Galaxy ◽  
Flat Rotation Curve ◽  
Disc Region ◽  
Fisher Relation

Fundamentally for the extended disc region of a spiral galaxy, an alternative solution to Laplace equation has been presented for a potential that is radially symmetric on the disc plane. This potential, unlike newtonian one, is shown to be logarithmic in distance from the centre, which allows for the rotation velocity to be constant along the disc radius.It is also shown that this potential easily manifests into a relationship between inner mass of the galaxy and terminal rotation velocity, which has been empirically observed and known as Baryonic Tully-Fisher relations.

Interstellar gas in the central region of the Galaxy

1967 ◽  
Vol 31 ◽  
pp. 239-251 ◽  
Author(s):  
F. J. Kerr
Keyword(s):  
Central Region ◽  
Galactic Plane ◽  
Neutral Hydrogen ◽  
Continuum Emission ◽  
Galactic Centre ◽  
Interstellar Gas ◽  
Hydrogen Recombination ◽  
The Galaxy ◽  
Centre Region ◽  
The Relationship

A review is given of information on the galactic-centre region obtained from recent observations of the 21-cm line from neutral hydrogen, the 18-cm group of OH lines, a hydrogen recombination line at 6 cm wavelength, and the continuum emission from ionized hydrogen.Both inward and outward motions are important in this region, in addition to rotation. Several types of observation indicate the presence of material in features inclined to the galactic plane. The relationship between the H and OH concentrations is not yet clear, but a rough picture of the central region can be proposed.

A CO Survey of the Southern Galactic Plane

1981 ◽  
Vol 4 (2) ◽  
pp. 243-247 ◽  
Author(s):  
W. H. McCutcheon ◽  
B. J. Robinson ◽  
J. B. Whiteoak
Keyword(s):  
Northern Hemisphere ◽  
Atomic Hydrogen ◽  
Molecular Hydrogen ◽  
Large Scale ◽  
Galactic Plane ◽  
Galactic Centre ◽  
Hydrogen Distribution ◽  
Millimetre Wave ◽  
The Galaxy ◽  
Wave Emission

Millimetre-wave emission from the CO molecule has proven to be an extremely useful probe of the cold, dense clouds of molecular hydrogen in the Galaxy. Previous studies of the large-scale distribution of CO in the galactic plane (Scoville and Solomon 1975; Burton et al. 1975; Bash and Peters 1976; Burton and Gordon 1978; Solomon et al. 1979b; Cohen et al. 1980) have all been of the northern hemisphere and primarily at longitudes 0° ≤ l ≥ 80°. These studies have revealed the striking characteristic that the CO, and by implication molecular hydrogen clouds, are concentrated in a ring extending from 4 to 8 kpc from the galactic centre. This is in sharp contrast to the atomic hydrogen distribution, which is fairly constant over the extended region from 4 to 13 kpc but correlates well with other Population I indicators.

scholarly journals Local Stellar Kinematics from RAVE data – V. Kinematic Investigation of the Galaxy with Red Clump Stars

2014 ◽  
Vol 31 ◽  
Author(s):  
S. Karaali ◽  
S. Bilir ◽  
S. Ak ◽  
E. Yaz Gökçe ◽  
Ö. Önal ◽  
...  
Keyword(s):  
Velocity Component ◽  
Galactic Plane ◽  
Radial Distance ◽  
Vertical Direction ◽  
Space Velocity ◽  
Galactic Centre ◽  
Galactic Rotation ◽  
Stellar Kinematics ◽  
The Galaxy ◽  
Red Clump

AbstractWe investigated the space velocity components of 6 610 red clump (RC) stars in terms of vertical distance, Galactocentric radial distance and Galactic longitude. Stellar velocity vectors are corrected for differential rotation of the Galaxy which is taken into account using photometric distances of RC stars. The space velocity components estimated for the sample stars above and below the Galactic plane are compatible only for the space velocity component in the direction to the Galactic rotation of the thin disc stars. The space velocity component in the direction to the Galactic rotation (Vlsr) shows a smooth variation relative to the mean Galactocentric radial distance (Rm), while it attains its maximum at the Galactic plane. The space velocity components in the direction to the Galactic centre (Ulsr) and in the vertical direction (Wlsr) show almost flat distributions relative to Rm, with small changes in their trends at Rm ~ 7.5 kpc. Ulsr values estimated for the RC stars in quadrant 180° < l ⩽ 270° are larger than the ones in quadrants 0° < l ⩽ 90° and 270° < l ⩽ 360°. The smooth distribution of the space velocity dispersions reveals that the thin and thick discs are kinematically continuous components of the Galaxy. Based on the Wlsr space velocity components estimated in the quadrants 0° < l ⩽ 90° and 270° < l ⩽ 360°, in the inward direction relative to the Sun, we showed that RC stars above the Galactic plane move towards the North Galactic Pole, whereas those below the Galactic plane move in the opposite direction. In the case of quadrant 180° < l ⩽ 270°, their behaviour is different, i.e. the RC stars above and below the Galactic plane move towards the Galactic plane. We stated that the Galactic long bar is the probable origin of many, but not all, of the detected features.

scholarly journals A Wide Field λ90cm Image Around the Galactic Centre - Evidence for a Poloidal Magnetic Field

1990 ◽  
Vol 140 ◽  
pp. 375-376
Author(s):  
K. R. Anantharamaiah ◽  
A. Pedlar
Keyword(s):  
Magnetic Field ◽  
Galactic Plane ◽  
Surrounding Medium ◽  
Galactic Centre ◽  
Wide Field ◽  
Pressure Balance ◽  
Poloidal Magnetic Field ◽  
The Galaxy

A number of unique non-thermal filamentary structures, which are all roughly perpendicular to the galactic plane have been discovered in the vicinity of the Galactic centre (see Yusef-Zadeh 1989 and references there in). On the basis of their uniformity, polarization angles, rigidity, and pressure balance with the surrounding medium, it has been hypothesized that a strong polodial field of milligauss strength pervades the inner 50 pc of the Galaxy (Morris and Yusef-Zadeh 1989 and Morris in this volume). We present here a single wide-field image, at λ90cm, which shows all the filamentary structures in this region and show that these observations are consistent with the above hypothesis.

scholarly journals Observations of Magnetic Fields in Galaxies

1992 ◽  
Vol 9 ◽  
pp. 81-86
Author(s):  
R. Wielebinski
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Supernova Remnants ◽  
Large Scale ◽  
Galactic Plane ◽  
Building Blocks ◽  
Galactic Centre ◽  
Definitive Evidence ◽  
The Galaxy ◽  
The Universe

AbstractMagnetic fields are present in every corner of the Universe. The Earth, the Sun and most of the planets are known to possess dipolar magnetic fields. In the Galaxy many individual objects like stars, pulsars, bipolar nebulae and supernova remnants are found to have associated magnetic fields. It seems that the rotation plays a significant role in the ability of a cosmic object to develop a magnetic field. The magnetic field of the Galaxy is observed to be oriented along the galactic plane as evidenced by both optical and radio polarization observations. Radio maps of the Galactic centre reveal poloidal magnetic fields as ‘wisps’ or ‘strings’ around Sagittarius A. Observations of nearby galaxies give us remarkable information about the large-scale magnetic fields in these building blocks of the Universe. Magnetic fields play an important role in the formation of jets of radio galaxies. Further out, in clusters of galaxies, definitive evidence has been given for the existence of intergalactic magnetic fields.

scholarly journals Internal Kinematics of Modelled Isolated and Interacting Disc Galaxies

2006 ◽  
Vol 2 (S235) ◽  
pp. 216-216
Author(s):  
T. Kronberger ◽  
W. Kapferer ◽  
S. Schindler ◽  
A. Böhm ◽  
E. Kutdemir ◽  
...  
Keyword(s):  
Velocity Field ◽  
Spiral Galaxies ◽  
Rotation Velocity ◽  
Systematic Investigation ◽  
Velocity Fields ◽  
The Galaxy ◽  
History Of ◽  
Hydrodynamical Simulations ◽  
Interaction History ◽  
Disc Galaxies

AbstractWe present a systematic investigation of the velocity fields of both isolated and interacting spiral galaxies in combined N-body/hydrodynamical simulations. Closely mimicking the procedures applied in observations of distant, small, and faint galaxies we extract rotation curves (RCs) and compare the results of the simulation directly to observations. Irregularities in the velocity field reflect disturbances in the gravitational potential of the galaxy. They can be used to trace the recent interaction history of a galaxy and give possible clues to the type of the respective interaction. In addition, identifying disturbances in the RCs is important for Tully-Fisher studies in order to accurately derive the maximum rotation velocity.

scholarly journals The Distribution of Open Clusters in the Galaxy

2021 ◽  
Vol 8 ◽  
Author(s):  
Hektor Monteiro ◽  
Douglas A. Barros ◽  
Wilton S. Dias ◽  
Jacques R. D. Lépine
Keyword(s):  
Galactic Plane ◽  
Rotation Velocity ◽  
Open Clusters ◽  
Space Distribution ◽  
Proper Motions ◽  
Corotation Radius ◽  
The Galaxy ◽  
Galactic Abundance ◽  
Galactic Orbit ◽  
Gaia Dr2

In this work we explore the new catalog of galactic open clusters that became available recently, containing 1,750 clusters that have been re-analyzed using the Gaia DR2 catalog to determine the stellar memberships. We used the young open clusters as tracers of spiral arms and determined the spiral pattern rotation speed of the Galaxy and the corotation radius, the strongest Galactic resonance. The sample of open clusters used here is increased by dozens of objects with respect to our previous works. In addition, the distances and ages values are better determined, using improvements to isochrone fitting and including an updated extinction polynomial for the Gaia DR2 photometric band-passes, and the Galactic abundance gradient as a prior for metallicity. In addition to the better age determinations, the catalog contains better positions in the Galactic plane and better proper motions. This allow us to discuss not only the present space distribution of the clusters, but also the space distribution of the clusters's birthplaces, obtained by integration of the orbits for a time equal to their age. The value of the rotation velocity of the arms (28.5 ± 1.0 km s−1 kpc−1) implies that the corotation radius (Rc) is close to the solar Galactic orbit (Rc/R0 = 1.01±0.08), which is supported by other observational evidence discussed in this text. A simulation is presented, illustrating the motion of the clusters in the reference frame of corotation. We also present general statistics of the catalog of clusters, like spatial distribution, distribution relative to height from the Galactic plane, and distribution of ages and metallicity. An important feature of the space distribution, the corotation gap in the gas distribution and its consequences for the young clusters, is discussed.

scholarly journals Hydrogen motions in the central region of the Galaxy

1964 ◽  
Vol 20 ◽  
pp. 183-186 ◽  
Author(s):  
B. F. Burke ◽  
M. A. Tuve
Keyword(s):  
Radio Telescope ◽  
Cross Sections ◽  
Central Region ◽  
Galactic Plane ◽  
Circular Motion ◽  
Galactic Centre ◽  
Strong Deviation ◽  
The Galaxy

The 21-cm hydrogen radiation near the galactic plane exhibits strong deviation from circular motion over longitudes within 30° or so of the galactic centre. In order to extend the observations first made by Rougoor and Oort,* the Carnegie multichannel H-line spectrograph was used with our 60-foot radio telescope at Derwood, Maryland, in order to confirm the Leiden work and extend observations to more southern longitudes. Cross-sections extending ±2° in latitude were taken every 2° in longitude from lII=−26°8 to lII=+2°2 and a series of points along the galactic equator were taken every 1° over the same range. Effort has been concentrated on the southern extension of the observations, which agree well with the Leiden observations over the section in common, but which carry the observations nearly 20° farther south in longitude.

The co-responsibility of mass and environment in the formation of lenticular galaxies

2020 ◽  
Vol 15 (S359) ◽  
pp. 173-174
Author(s):  
A. Cortesi ◽  
L. Coccato ◽  
M. L. Buzzo ◽  
K. Menéndez-Delmestre ◽  
T. Goncalves ◽  
...  
Keyword(s):  
Active Galactic Nuclei ◽  
Maximum Likelihood Method ◽  
Spiral Galaxies ◽  
Galactic Nuclei ◽  
Rotation Velocity ◽  
Elliptical Galaxies ◽  
Likelihood Method ◽  
Data Set ◽  
Lenticular Galaxies ◽  
Galaxies Kinematics

AbstractWe present the latest data release of the Planetary Nebulae Spectrograph Survey (PNS) of ten lenticular galaxies and two spiral galaxies. With this data set we are able to recover the galaxies’ kinematics out to several effective radii. We use a maximum likelihood method to decompose the disk and spheroid kinematics and we compare it with the kinematics of spiral and elliptical galaxies. We build the Tully- Fisher (TF) relation for these galaxies and we compare with data from the literature and simulations. We find that the disks of lenticular galaxies are hotter than the disks of spiral galaxies at low redshifts, but still dominated by rotation velocity. The mechanism responsible for the formation of these lenticular galaxies is neither major mergers, nor a gentle quenching driven by stripping or Active Galactic Nuclei (AGN) feedback.

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