Subluminal Mass

2020 ◽  
pp. 239-278
Author(s):  
P. J. E. Peebles
Keyword(s):  
Spiral Galaxy ◽  
Spiral Galaxies ◽  
Clusters Of Galaxies ◽  
Spiral Arms ◽  
The Galaxy ◽  
History Of ◽  
Large Clusters ◽  
Mass Component ◽  
Significant Mass

This chapter studies the presence of “subliminal matter.” The presence of significant mass in subluminal matter was first suggested in the 1930s by the surprisingly large velocities of galaxies in clusters of galaxies. The chapter traces the history of discovery of astronomical evidence of subluminal matter in large clusters of galaxies, in groups of a few or just two galaxies that are close enough that they seem likely to be gravitationally bound, and in individual spiral galaxies. There must be enough mass in spirals to account for the circular velocities of disk stars, and the mass rotationally supported in the disk must be large enough that gravity can form spiral arms, but this mass component cannot be so large that the spiral arms grow to destroy the observed nearly circular motions in the disk. These conditions require that most of the mass in a spiral galaxy is in a stable subluminal massive halo draped around the outskirts of the luminous parts of the galaxy.

scholarly journals IR imaging of spiral galaxy bulges

1993 ◽  
Vol 153 ◽  
pp. 441-442
Author(s):  
Dennis Zaritsky ◽  
Marcia Rieke ◽  
Hans-Walter Rix
Keyword(s):  
Spiral Galaxy ◽  
Stellar Population ◽  
Spiral Galaxies ◽  
Spiral Arms ◽  
Ir Imaging ◽  
The Impact

Imaging in the infrared (2.2μ) minimizes the impact of dust obscuration and allows reliable mapping of the mass-tracing stellar population in spiral galaxies. We find dramatic differences compared to photometry at shorter wavelengths (e.g. 0.8μ). As an example, the observations of the mini-bar and inner spiral arms of M 51 are discussed.

scholarly journals The frequency of ring galaxies and the probability of their formation by collisions

1978 ◽  
Vol 79 ◽  
pp. 117-120 ◽  
Author(s):  
V. Dostal ◽  
V. Metlov
Keyword(s):  
Spiral Galaxy ◽  
Relative Velocity ◽  
Unit Volume ◽  
Spiral Galaxies ◽  
Absolute Magnitude ◽  
Stellar Systems ◽  
Clusters Of Galaxies ◽  
Central Collisions ◽  
Ring Galaxies ◽  
Minimum Separation

A survey of ring galaxies which were discovered in 1960 by B. Vorontsov-Velyaminov has been carried out using the Morphological Catalogue of Galaxies. Clusters of galaxies were also included. Such galaxies without spiral arms constitute 0.7% of all galaxies down to 15m.0, and are 100 times less frequent than spiral galaxies. This percentage is the same for clusters, but there are fields where ring galaxies are 3–5 times more frequent than the average. the probability of nearly central chance collisions of galaxies as proposed by some theories has been calculated. It was assumed that a ring galaxy is formed from the encounter of a spiral galaxy with another galaxy if its mass or luminosity is not less than 1% of that of the principal galaxy. the minimum separation of their centres was taken to be less than 2.7 kpc, but the angles between the vectors of the relative velocity and the planes of galaxies were not restricted. the lifetime of the rings once they are formed was assumed to be 109 years and the distribution of the galactic velocities was calculated according to a Maxwellian distribution. the number of galaxies of given absolute magnitude per unit volume was taken from Holmberg (Stars and Stellar Systems, 9, 123). the curvature of the trajectories was taken into account. So conditions were chosen to be most favourable for nearly central collisions.

scholarly journals HII Regions of NGC 628 and M101 as seen with SpIOMM

2010 ◽  
Vol 6 (S277) ◽  
pp. 112-115 ◽  
Author(s):  
Laurie Rousseau-Nepton ◽  
Carmelle Robert ◽  
Laurent Drissen
Keyword(s):  
Spiral Galaxies ◽  
Hii Regions ◽  
Stellar Populations ◽  
Emission Lines ◽  
Visible Range ◽  
Star Forming ◽  
The Galaxy ◽  
History Of

AbstractWith SpIOMM, we obtained numerous spectra in the visible range covering simultaneously several emission lines of bright Hii regions in the spiral galaxies NGC 628 and M101. We measured the size and luminosity of the Hii regions as well as the gas metallicity, temperature, and density. We estimated the age and star forming rate of the young stellar populations associated with the Hii regions. We looked for gradients along the galaxy radius and search for relations with the galactic arm positions. This is a first step in a project, based on a detailed study of stellar populations, to rebuild the history of spiral galaxies and to identify the mechanisms responsible for their evolution.

scholarly journals A Gaseous Group with Unusual Remote Star Formation

2011 ◽  
Vol 28 (3) ◽  
pp. 271-279 ◽  
Author(s):  
N. Santiago-Figueroa ◽  
M. E. Putman ◽  
J. Werk ◽  
G. R. Meurer ◽  
E. Ryan-Weber
Keyword(s):  
Star Formation ◽  
Spiral Galaxy ◽  
Dwarf Galaxies ◽  
Dwarf Galaxy ◽  
Spiral Arms ◽  
Gaseous Disk ◽  
Ram Pressure ◽  
The Galaxy ◽  
Galaxy Center ◽  
Region 10

AbstractWe present VLA 21-cm observations of the spiral galaxy ESO 481-G017 to determine the nature of remote star formation traced by an Hii region found 43 kpc and ∼800 km s−1 from the galaxy center (in projection). ESO 481-G017 is found to have a 120 kpc Hi disk with a mass of 1.2 × 1010M⊙ and UV GALEX images reveal spiral arms extending into the gaseous disk. Two dwarf galaxies with Hi masses close to 108M⊙ are detected at distances of ∼200 kpc from ESO 481-G017 and a Hi cloud with a mass of 6 × 107M⊙ is found near the position and velocity of the remote Hii region. The Hii region is somewhat offset from the Hi cloud spatially and there is no link to ESO 481-G017 or the dwarf galaxies. We consider several scenarios for the origin of the cloud and Hii region and find the most likely is a dwarf galaxy that is undergoing ram pressure stripping. The Hi mass of the cloud and Hi luminosity of the Hii region (1038.1 erg s−1) are consistent with dwarf galaxy properties, and the stripping can trigger the star formation as well as push the gas away from the stars.

Nonlocal Gravity and Dark Matter

2017 ◽  
Author(s):  
Bahram Mashhoon
Keyword(s):  
Dark Matter ◽  
Solar System ◽  
Observational Data ◽  
Virial Theorem ◽  
Spiral Galaxies ◽  
Clusters Of Galaxies ◽  
The Galaxy

The implications of linearized NLG for the gravitational physics of the Solar System, spiral galaxies and nearby clusters of galaxies are critically examined in this chapter. In the Newtonian regime, NLG involves a reciprocal kernel with three length parameters. We discuss the determination of these parameters by comparing the predictions of the theory with observational data. Furthermore, the virial theorem for the Newtonian regime of NLG is derived and its consequences for nearby “isolated” astronomical systems in virial equilibrium are investigated. For such a galaxy, in particular, the galaxy’s baryonic diameter namely, the diameter of the smallest sphere that completely surrounds the baryonic system at the present time, is predicted to be larger than the basic nonlocality lengthscale, which is about 3 kpc, times the effective dark matter fraction of the galaxy.

scholarly journals Assembling Spiral Galaxies

1996 ◽  
Vol 171 ◽  
pp. 11-18
Author(s):  
R.C. Kennicutt
Keyword(s):  
Galaxy Formation ◽  
Spiral Galaxies ◽  
Dynamical Evolution ◽  
Star Formation History ◽  
Physical Mechanisms ◽  
Hubble Sequence ◽  
Galaxy Formation And Evolution ◽  
The Galaxy ◽  
History Of ◽  
Formation And Evolution

Nearby spiral galaxies offer vital clues to some of the most fundamental questions about galaxy formation and evolution: What is the star formation history of the universe, past and future? When did disks form, during the final stages of a single primeval collapse, or as a continuous or episodic process? What is the evolutionary nature of the Hubble sequence, and what are the physical mechanisms that dictate the present-day Hubble type of a galaxy? Was Hubble type imprinted at birth, or can it be deterined or at least modified by infall, mergers, or secular dynamical evolution within the galaxy? These issues are not specific to spirals, of course, and much of this conference will address just these questions in a broader context. However present-day spirals offer unique advantages for studying these problems; they exhibit a broad range of dynamical and evolutionary properties, and the dynamical fragility of disks makes them excellent seismometers of galaxy interaction and merger rates at recent epochs.

scholarly journals The beauty of resolution: The SN Ib factory NGC 2770 spatially resolved

2014 ◽  
Vol 10 (S309) ◽  
pp. 169-170
Author(s):  
C. C. Thöne ◽  
L. Christensen ◽  
J. Gorosabel ◽  
A. de Ugarte Postigo
Keyword(s):  
Stellar Population ◽  
Late Type ◽  
Spiral Arms ◽  
Star Forming ◽  
Spatially Resolved ◽  
Star Forming Regions ◽  
The Galaxy ◽  
History Of ◽  
First Time

AbstractThe late-type spiral NGC 2770 hosted 3 Type Ib supernovae (SNe) in or next to star-forming regions in its outer spiral arms. We study the properties of the SN sites and the galaxy at different spatial resolutions to infer propeties of the SN progenitors and the SF history of the galaxy. Several 3D techniques are used and, for the first time, we present images of metallicity, shocks and stellar population ages from OSIRIS/GTC imaging with tunable narrowband filters.

scholarly journals A Unified Electro-Gravity Theory to Model Spiral Galaxies without Dark Matter

2019 ◽  
Author(s):  
Nirod K. Das
Keyword(s):  
Elementary Particle ◽  
Dark Matter ◽  
Spiral Galaxy ◽  
Surface Brightness ◽  
Spiral Galaxies ◽  
Rotation Speed ◽  
Modified Newtonian Dynamics ◽  
Newtonian Dynamics ◽  
The Galaxy ◽  
Flat Rotation Curves

A unified electro-gravity (UEG) theory, which has been successfully used for modeling an elementary particle, is applied in this paper to model gravitation in spiral galaxies. The new UEG model would explain the “flat rotation curves” commonly observed in the spiral galaxies, without need for any hypothetical dark matter. The UEG theory is implemented in a somewhat different manner for a spiral galaxy, as compared to the simple application of the UEG theory to an elementary particle. This is because the spiral galaxy, unlike the elementary particle, is not spherically symmetric. The UEG constant $\gamma$, required in the new model to support the galaxies' flat rotation speeds, is estimated using measured data from a galaxy survey, as well as for a selected galaxy for illustration. The estimates are compared with the $\gamma$ derived from the UEG model of an elementary particle. The UEG model for the galaxy is shown to explain the empirical Tully-Fisher Relationship (TFR), is consistent with the Modified Newtonian Dynamics (MOND), and is also independently supported by measured trends of galaxy thickness with surface brightness and rotation speed.

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.

scholarly journals A Circulation Hypothesis of Spiral Galaxies

1998 ◽  
Vol 188 ◽  
pp. 293-294
Author(s):  
Chen Linfei
Keyword(s):  
Spiral Galaxies ◽  
Spiral Structure ◽  
Galactic Center ◽  
Circulatory System ◽  
Spiral Arms ◽  
The Galaxy ◽  
Spiral Arm

A circulation hypothesis of spiral galaxies is proposed here to explain their spiral structure: the spiral arm material is going to the galactic center along a spiral orbit and then ejects from the galactic center in the form of two-way jets in opposite directions and finally, the ejected jets return to the galaxy in the form of spiral arms again, thereby forming a closed circulatory system.

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