scholarly journals On the Formation of Elliptical Galaxies

1975 ◽  
Vol 69 ◽  
pp. 271-285
Author(s):  
J. R. Gott
Keyword(s):  
Angular Momentum ◽  
Numerical Models ◽  
Elliptical Galaxies ◽  
Tidal Effects ◽  
Tidal Interactions ◽  
The Galaxy ◽  
Simple Scaling ◽  
Hubble’S Law ◽  
Fitting Parameters ◽  
Relaxation Models

Simple collapse and violent relaxation models produce sharply cut off envelopes with ϱ(r) ∝ r–4, whereas actual elliptical galaxies have more extended envelopes approximately given by ϱ(r) ∝ r–3 as implied by Hubble's Law. Numerical models are presented, showing that when cosmological infall effects are included, galaxies are produced with more extended envelopes having a ϱ(r) ∝ r–2.8 dependence in excellent agreement with Hubble's Law. We have also computed a realistic rotating model of an E5 galaxy which includes infall effects and where the angular momentum of the galaxy is gained through tidal interactions with neighboring protogalaxies. The envelope displays a Hubble dependence but at great distances shows a cutoff due to the tidal effects. The model is compared to the E5 galaxy NGC 4697 and provides an outstandingly good fit to the observations. Except for simple scaling, this excellent fit is produced without the use of any free fitting parameters.

scholarly journals Probing the Tides in Interacting Galaxy Pairs

1990 ◽  
Vol 124 ◽  
pp. 537-542
Author(s):  
Kirk D. Borne
Keyword(s):  
Gravitational Field ◽  
Binary System ◽  
Driving Forces ◽  
Elliptical Galaxies ◽  
Physical Parameters ◽  
Tidal Interactions ◽  
The Galaxy ◽  
Merger Rate ◽  
The Masses ◽  
Best Fit

AbstractDetailed spectroscopic and imaging observations of colliding elliptical galaxies have revealed unmistakable diagnostic signatures of the tidal interactions. It is possible to compare both the distorted luminosity distributions and the disturbed internal rotation profiles with numerical simulations in order to model the strength of the tidal gravitational field acting within a given pair of galaxies. Using the best-fit numerical model, one can then measure directly the mass of a specific interacting binary system. This technique applies to individual pairs and therefore complements the classical methods of measuring the masses of galaxy pairs in well-defined statistical samples. The “personalized” modeling of galaxy pairs also permits the derivation of each binary’s orbit, spatial orientation, and interaction timescale. Similarly, one can probe the tides in less-detailed observations of disturbed galaxies in order to estimate some of the physical parameters for larger samples of interacting galaxy pairs. These parameters are useful inputs to the more universal problems of (1) the galaxy merger rate, (2) the strength and duration of the driving forces behind tidally-stimulated phenomena (e.g., starbursts and maybe QSOs), and (3) the identification of long-lived signatures of interaction/merger events.

scholarly journals Enhanced Star Formation rates in Binary Interacting Elliptical Galaxies

1995 ◽  
Vol 164 ◽  
pp. 452-452
Author(s):  
Tapan K Chatterjee
Keyword(s):  
Star Formation ◽  
Initial Conditions ◽  
Radial Distance ◽  
Orbital Plane ◽  
Elliptical Galaxies ◽  
Tidal Effects ◽  
Stellar Orbits ◽  
Cooling Flow ◽  
The Galaxy ◽  
Stellar Density

We study the stellar orbits, as a function of the binary motion of two identical ellipticals, under initial conditions marginally sufficient for strong interaction. The stars were initially given circularly symmetric velocities. The tidal effects cause a redistribution of stellar orbits, resulting in crowding of stars in shells; the same attaining its maximum intensity slightly after a pericentric passage. As the galaxies recede, the structure disperses gradually by expanding; but is restored, intensified and forms at a shorter radial distance as the galaxies return for a subsequent approach in a shrinking orbit. We give the stellar positions, projected perpendicular to the orbital plane, shortly after the first (t≈0.5) and second (t≈6) pericentric passages in the figures; (time being given in dimensionless units corresponding to mass=l, radius=l, G=4.50). On the basis of the cooling gas inflow model, the gas will be compressed and shocked in these regions of enhanced stellar density, leading to bursts of star formation. The interval between the two successive starbursts is found to be of the same order as the trapping time needed by the galaxy to incorporate the gas ejected by stars in its cooling flow.

scholarly journals Dissipation and the Formation of Galaxies

1987 ◽  
Vol 127 ◽  
pp. 353-366
Author(s):  
R.G. Carlberg
Keyword(s):  
Angular Momentum ◽  
Galaxy Formation ◽  
Elliptical Galaxies ◽  
Stellar Disk ◽  
Disk Galaxies ◽  
The Core ◽  
Hubble Sequence ◽  
The Galaxy ◽  
Isothermal Gas ◽  
Gas Cloud

The evidence for dissipation in elliptical galaxies indicates neither the epoch of formation nor the rate of radiation. The hypotheses for the formation of ellipticals include mergers of pre-existing, mostly stellar, disk galaxies; accumulation of gassy fragments that subsequently turn into stars; and the dynamical collapse of a distinct protogalactic gas cloud with simultaneous star formation. Mergers of purely stellar disks seem unlikely, because the phase space density of disks is everywhere far below that of the cores of normal ellipticals. Allowing a few percent of the mass of the galaxy to dissipate into the core and turn into stars could remove this difficulty. In the Hubble sequence of galaxies, ellipticals are characterized by their low angular momentum content. As a start to understanding the general problem for galaxy formation and angular momentum acquisition in the presence of dissipation, a cosmological N-body experiment containing both a dominant collisionless component and an isothermal gas is described. The collisionless component clusters in the usual hierarchical manner appropriate to the spectrum of fluctuations. In contrast, the gas fragments only when the Jeans mass drops below the turnaround mass. The fragments subsequently shrink, becoming distinct entities with relatively low chances of being quickly incorporated in a larger unit. Gravitational torques transfer angular momentum outward in the dissipating gas, placing most of the gas angular momentum at large radii in the protogalaxy. The distant, high angular momentum gas has a relatively long infall time onto the galaxy. The gas may continue to rain down for some time if the galaxy remains undisturbed, or, the growth of clustering may strip the gas off, leaving a low angular momentum system.

scholarly journals Gaseous Disks in the Nuclei of Elliptical Galaxies

1997 ◽  
Vol 163 ◽  
pp. 620-625 ◽  
Author(s):  
H. Ford ◽  
Z. Tsvetanov ◽  
L. Ferrarese ◽  
G. Kriss ◽  
W. Jaffe ◽  
...  
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Angular Momentum ◽  
Accretion Disks ◽  
Large Scale ◽  
Elliptical Galaxies ◽  
Central Mass ◽  
Massive Black Holes ◽  
Radio Jets

AbstractHST images have led to the discovery that small (r ~ 1″ r ~ 100 – 200 pc), well-defined, gaseous disks are common in the nuclei of elliptical galaxies. Measurements of rotational velocities in the disks provide a means to measure the central mass and search for massive black holes in the parent galaxies. The minor axes of these disks are closely aligned with the directions of the large–scale radio jets, suggesting that it is angular momentum of the disk rather than that of the black hole that determines the direction of the radio jets. Because the disks are directly observable, we can study the disks themselves, and investigate important questions which cannot be directly addressed with observations of the smaller and unresolved central accretion disks. In this paper we summarize what has been learned to date in this rapidly unfolding new field.

Supermassive Black Hole feedback in early type galaxies

2020 ◽  
Vol 15 (S359) ◽  
pp. 119-125
Author(s):  
W. Forman ◽  
C. Jones ◽  
A. Bogdan ◽  
R. Kraft ◽  
E. Churazov ◽  
...  
Keyword(s):  
Dark Matter Halo ◽  
Scaling Relations ◽  
Radio Sources ◽  
Early Type ◽  
X Ray ◽  
Galaxy Groups ◽  
Sufficient Energy ◽  
The Galaxy ◽  
Simple Scaling ◽  
Halo Masses

AbstractOptically luminous early type galaxies host X-ray luminous, hot atmospheres. These hot atmospheres, which we refer to as coronae, undergo the same cooling and feedback processes as are commonly found in their more massive cousins, the gas rich atmospheres of galaxy groups and galaxy clusters. In particular, the hot coronae around galaxies radiatively cool and show cavities in X-ray images that are filled with relativistic plasma originating from jets powered by supermassive black holes (SMBH) at the galaxy centers. We discuss the SMBH feedback using an X-ray survey of early type galaxies carried out using Chandra X-ray Observatory observations. Early type galaxies with coronae very commonly have weak X-ray active nuclei and have associated radio sources. Based on the enthalpy of observed cavities in the coronae, there is sufficient energy to “balance” the observed radiative cooling. There are a very few remarkable examples of optically faint galaxies that are 1) unusually X-ray luminous, 2) have large dark matter halo masses, and 3) have large SMBHs (e.g., NGC4342 and NGC4291). These properties suggest that, in some galaxies, star formation may have been truncated at early times, breaking the simple scaling relations.

scholarly journals On a mechanism that structures galaxies

1979 ◽  
Vol 84 ◽  
pp. 157-158
Author(s):  
D. Lynden-Bell
Keyword(s):  
Angular Momentum ◽  
Differential Rotation ◽  
Spiral Structure ◽  
Rotation Curves ◽  
Eccentric Orbits ◽  
The Galaxy ◽  
Central Regions ◽  
Pattern Speed ◽  
Stellar Orbit ◽  
Lindblad Resonance

By considering the interaction of a single stellar orbit with a weak cos 2Φ potential it is shown that in the central regions of galaxies with slowly rising rotation curves, the elongations of the orbits will align along any potential valley and oscillate about it. This effect is more pronounced for elongated orbits. In such regions any pair of orbits will naturally align under their mutual gravity and so a bar will form. The gravity of this bar will drive a spiral structure in the outer parts of the galaxy where differential rotation is too strong to allow the orbits to be caught by the bar. The spiral structure carries a torque which slowly drains angular momentum from the bar, gradually making its outline more eccentric and slowing its pattern speed. In the outer parts of the bar only the more eccentric orbits align with the potential valley; the rounder ones form a ring or lens about the bar. As the pattern speed slows down, the corotation resonance and outer Lindblad resonance, which receive the angular momentun, move outwards. The evolution of the system is eventually slowed down by the weakness of these outer resonances where the material is rather sparse.

scholarly journals Kinematics of Planetary Nebulae in M51's Tidal Tail

2003 ◽  
Vol 209 ◽  
pp. 633-634
Author(s):  
John J. Feldmeier ◽  
J. Christopher Mihos ◽  
Patrick R. Durrell ◽  
Robin Ciardullo ◽  
George H. Jacoby
Keyword(s):  
Surface Brightness ◽  
Numerical Models ◽  
Planetary Nebulae ◽  
Tidal Tail ◽  
Low Surface Brightness ◽  
Galaxy Interaction ◽  
Self Consistent ◽  
The Galaxy ◽  
Interacting Systems ◽  
Kinematic Properties

The galaxy pair NGC 5194/95 (M51) is one of the closest and best known interacting systems. Despite its notoriety, however, many of its features are not well studied. Extending westward from NGC 5195 is a low surface brightness tidal tail, which can only be seen in deep broadband exposures. Our previous [O III] λ5007 planetary nebulae (PN) survey of M51 recovered this tidal tail, and presented us with a opportunity to study the kinematics of a galaxy interaction in progress. We report the results of a spectroscopy survey of the PN, aimed at determining their kinematic properties. We then use these data to constrain new self-consistent numerical models of the system.

scholarly journals The Galactic Pulsar Population and Neutron Star Birth

1987 ◽  
Vol 125 ◽  
pp. 67-78
Author(s):  
Ramesh Narayan
Keyword(s):  
Angular Momentum ◽  
Neutron Star ◽  
Binary Systems ◽  
Magnetic Coupling ◽  
Scale Height ◽  
High Magnetic Fields ◽  
Radio Pulsars ◽  
X Ray ◽  
The Galaxy ◽  
Low Mass

The radio pulsars in the Galaxy are found predominantly in the disk, with a scale height of several hundred parsecs. After allowing for pulsar velocities, the data are consistent with the hypothesis that single pulsars form from massive stellar progenitors. The number of active single pulsars in the Galaxy is ∼ 1.5 × 105, and their birthrate is 1 per ∼ 60 yrs. There is some evidence that many single pulsars, particularly those with high magnetic fields, are born spinning slowly, with initial periods ∼ 0.5–1s. This could imply an origin through binary “recycling” followed by orbit disruption, or might suggest that the pre-supernova stellar core efficiently loses angular momentum to the envelope through magnetic coupling. The birthrate of binary radio pulsars, particularly of the millisecond variety, seems to be much larger than previous estimates, and might suggest that these systems do not originate in low mass X-ray binary systems.

scholarly journals Relation Between Star Formation and Angular Momentum in Spiral Galaxies

1983 ◽  
Vol 100 ◽  
pp. 135-136
Author(s):  
L. Carrasco ◽  
A. Serrano
Keyword(s):  
Angular Momentum ◽  
Star Formation ◽  
Radial Distribution ◽  
Spiral Galaxies ◽  
Formation Rate ◽  
Inverse Function ◽  
Solar Neighborhood ◽  
Spin Angular Momentum ◽  
Stellar Formation ◽  
The Galaxy

We derive the radial distribution of the specific angular momentum j=J/M, for the gas in M31, M51 and the galaxy, objects for which well observed unsmoothed rotation curves are available in the literature. We find the specific angular momentum to be anti-correlated with the present stellar formation rate, i.e. minima of spin angular momentum correspond to the loci of spiral arms. We find that the stellar formation rate is an inverse function of j. We derive new values of Oort's A constant for the arm and interarm regions in the solar neighborhood.

The Hi Neighborhoods Around STARBIRDS

2018 ◽  
Vol 14 (S344) ◽  
pp. 280-282
Author(s):  
Megan C. Johnson ◽  
Kristen B. W. McQuinn ◽  
John Cannon ◽  
Charlotte Martinkus ◽  
Evan Skillman ◽  
...  
Keyword(s):  
Star Formation ◽  
Surface Brightness ◽  
Spiral Galaxies ◽  
Dwarf Galaxies ◽  
Neutral Hydrogen ◽  
Tidal Interactions ◽  
Low Surface Brightness ◽  
The Galaxy ◽  
Green Bank Telescope ◽  
Intense Star Formation

AbstractStarbursts are finite periods of intense star formation (SF) that can dramatically impact the evolutionary state of a galaxy. Recent results suggest that starbursts in dwarf galaxies last longer and are distributed over more of the galaxy than previously thought, with star formation efficiencies (SFEs) comparable to spiral galaxies, much higher than those typical of non-bursting dwarfs. This difference might be explainable if the starburst mode is externally triggered by gravitational interactions with other nearby systems. We present new, sensitive neutral hydrogen observations of 18 starburst dwarf galaxies, which are part of the STARburst IRregular Dwarf Survey (STARBIRDS) and each were mapped with the Green Bank Telescope (GBT) and/or Parkes Telescope in order to study the low surface brightness gas distributions, a common tracer for tidal interactions.

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