共查询到20条相似文献,搜索用时 11 毫秒
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We have undertaken numerical simulations of galaxy interactions and mergers, coupling the dynamics with the star formation
history and the chemical evolution. The self-gravity of stars and gas is taken into account through a tree-code algorithm,
the gas hydrodynamics through SPH, and an empirical law such as a local Schmidt law is used to compute star formation. The
gas and stellar metallicity is computed at each position, according to assumed yields, and the dust amount is monitored. At
each step the spectra of galaxies are computed, according to simple radiative transfer and dust models. Initial conditions
for these simulations will be taken from a large-scale cosmological frame-work. The aim is to build a statistically significant
library of merger histories. The first results of the project will be discussed, in particular on predictions about galaxy
surveys at high redshift.
This revised version was published online in September 2006 with corrections to the Cover Date. 相似文献
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V. P. Reshetnikov 《Astrophysics》1991,35(2-3):386-393
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V. P. Reshetnikov 《Astrophysics and Space Science》1994,211(1):155-160
A sample of members of close-binary interacting galaxies with the known values of the maximum rotational velocities are considered. It is found that the spiral galaxies in interacting systems tend to have lower rotational velocities and smaller mass to luminosity ratios than their counterparts in the field. The Tully-Fisher relationship may be different for interacting and field galaxies. 相似文献
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V. Charmandaris O. Laurent I.F. Mirabel P. Gallais M. Sauvage L. Vigroux C. Cesarsky D. Tran 《Astrophysics and Space Science》1999,266(1-2):99-104
In this paper, we present ISOCAM mid-IR broad band images and spectraof three well known interacting galaxies. These are the prototypicalultraluminous IR galaxy Arp 220, and NGC 6240, which are classifiedas major mergers resulting from a collision of two disk galaxies ofapproximately equal mass, and the prime example of collisional ringgalaxies, the Cartwheel. Our observations provide a new powerful tooland shed some more light to the properties of the hot dust and starformation in interacting galaxies. 相似文献
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Lourdes De Juan Luis Colina Ismael Pérez-Fournon 《Astrophysics and Space Science》1993,205(1):209-216
We have used a numerical method based on elliptical fitting of isophotes to analyse the structural parameters of three pairs of elliptical galaxies containing radio jets. The relationship between tidal interactions and radio activity is also investigated. 相似文献
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We present the results of our analysis of the geometrical tidal tail characteristics for nearby and distant interacting galaxies. The sample includes more than two hundred nearby galaxies and about seven hundred distant ones. The distant galaxies have been selected in several deep fields of the Hubble Space Telescope (HDF-N, HDF-S, HUDF, GOODS, GEMS) and they are at mean redshift 〈z〉 = 0.65. We analyze the distributions of lengths and thicknesses for the tidal structures and show that the tails in distant galaxies appear shorter than those in nearby ones. This effect can be partly attributed to observational selection, but, on the other hand, it may result from the general evolution of the sizes of spiral galaxies with z. The positions of interacting galaxies on the galaxy luminosity (L)-tidal tail length (l) plane are shown to be explained by a simple geometrical model, with the upper envelope of the observed distribution being \(l \propto \sqrt L\). We have solved the problem on the relationship between the observed distribution of tail flatting and the tail length in angular measure by assuming the tidal tails to be arcs of circumferences visible at arbitrary angles to the line of sight. We conclude that the angular length of the tidal tails visually distinguished in nearby and distant galaxies, on average, exceeds 180°. 相似文献
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It is shown that the fractional increase in binding energy of a galaxy in a fast collision with another galaxy of the same size can be well represented by the formula $$\xi _2 = 3({G \mathord{\left/ {\vphantom {G {M_2 \bar R}}} \right. \kern-\nulldelimiterspace} {M_2 \bar R}}) ({{M_1 } \mathord{\left/ {\vphantom {{M_1 } {V_p }}} \right. \kern-\nulldelimiterspace} {V_p }})^2 e^{ - p/\bar R} = \xi _1 ({{M_1 } \mathord{\left/ {\vphantom {{M_1 } {M_2 }}} \right. \kern-\nulldelimiterspace} {M_2 }})^3 ,$$ whereM 1,M 2 are the masses of the perturber and the perturbed galaxy, respectively,V p is the relative velocity of the perturber at minimum separationp, and \(\bar R\) is the dynamical radius of either galaxy. 相似文献
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G. M. Ballabh 《Astrophysics and Space Science》1973,24(2):535-561
Methods are developed for analysing the gravitational properties of disks having circularly symmetric distribution of matter.
It is shown how this can be conveniently done by assuming that the surface density distribution may be approximated by a polynomial
in ascending powers of the distance from the centre of the configuration. A theory has been developed to determine the gravitational
potential of a single disk at any point in space in terms of the coefficients of the polynomial defining the surface distribution
of matter, and the potential energy of two disks of arbitrary separation and orientation due to their mutual gravitational
attraction. The basic functions, required for obtaining the potential in the plane of the disk and the mutual potential energy
of two coplanar disks, have been tabulated. Two overlapping coplanar disks attract just like mass-points at a certain separation,r
c
, of their centres. The force of attraction of disks is less than the force of attraction of mass-points having masses equal
to the masses of the disks, if the separation of the centres is less thanr
c
, and greater if the separation is greater thanr
c
. For typical galaxies of equal radiiR,r
c
≈R. 相似文献
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A theory has been developed for obtaining the potential energy of two interpenetrating spherically symmetric galaxies of unequal dimensions due to their mutual gravitational interaction. The mass distribution in both the galaxies is assumed to be that of a polytrope of integral index. A basic function that occurs in the theory has been tabulated for the cases of polytropes of indicesn=0 and 4 for four ratios of the radii. 相似文献
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Renzo Sancisi Filippo Fraternali Tom Oosterloo Thijs van der Hulst 《Astronomy and Astrophysics Review》2008,15(3):189-223
Evidence for the accretion of cold gas in galaxies has been rapidly accumulating in the past years. HI observations of galaxies and their environment have brought to light new facts and phenomena which are evidence of ongoing
or recent accretion: (1) A large number of galaxies are accompanied by gas-rich dwarfs or are surrounded by HI cloud complexes, tails and filaments. This suggests ongoing minor mergers and recent arrival of external gas. It may be regarded,
therefore, as direct evidence of cold gas accretion in the local universe. It is probably the same kind of phenomenon of material
infall as the stellar streams observed in the halos of our galaxy and M 31. (2) Considerable amounts of extra-planar HI have been found in nearby spiral galaxies. While a large fraction of this gas is undoubtedly produced by galactic fountains,
it is likely that a part of it is of extragalactic origin. Also the Milky Way has extra-planar gas complexes: the Intermediate-
and High-Velocity Clouds (IVCs and HVCs). (3) Spirals are known to have extended and warped outer layers of HI. It is not clear how these have formed, and how and for how long the warps can be sustained. Gas infall has been proposed
as the origin. (4) The majority of galactic disks are lopsided in their morphology as well as in their kinematics. Also here
recent accretion has been advocated as a possible cause. In our view, accretion takes place both through the arrival and merging
of gas-rich satellites and through gas infall from the intergalactic medium (IGM). The new gas could be added to the halo
or be deposited in the outer parts of galaxies and form reservoirs for replenishing the inner parts and feeding star formation.
The infall may have observable effects on the disk such as bursts of star formation and lopsidedness. We infer a mean “visible”
accretion rate of cold gas in galaxies of at least . In order to reach the accretion rates needed to sustain the observed star formation (), additional infall of large amounts of gas from the IGM seems to be required. 相似文献
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Based on archival Hubble Space Telescope ACS/WFC images, we have performed stellar photometry for more than 0.6 million stars
in the interacting galaxies NGC 5194 and NGC 5195 of the M51 system. Stars of various ages have been identified on the constructed
Hertzsprung-Russell diagram: blue and red supergiants, AGB stars, and red giants. The distance to M51 has been measured from
the position of the tip of the red giant branch, D = 9.9 ± 0.7 Mpc. We have determined the change in the metallicity of red supergiants along the galactic radius in NGC 5194.
Despite the gravitational interaction, the distribution of stars in NGC 5194 does not differ from that in isolated galaxies.
The asymmetric stellar structures of NGC5195 (the so-called “feathers”) formed through the interaction of two galaxies have
been found to consist mostly of AGB stars. 相似文献
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Byurakan Astrophysical Observatory; Special Astrophysical Observatory, USSR Academy of Sciences. Translated from Astrofizika, Vol. 34, No. 3, pp. 383–394, May–June, 1991. 相似文献
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A dynamical model composed of a disk galaxy with an elliptic companion, moving in a circular orbit, is used in order to study
the stellar orbits in a binary galaxy. Using the Poincare surface of section we study the evolution of the stochastic regions
in the primary galaxy considering the mass of the companion or the value of the Jacobi’s integral as a parameter. Our numerical
calculations suggest that the regions of stochasticity increase, as the mass of the companion or the value of the Jacobi’s
integral increase. An interesting observation is that only direct orbits become stochastic. 相似文献
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The formation of spiral structure in a galaxy, as a result of the gravitational perturbation caused by a permanent companion,
is studied. It is found that spiral structure appears only when a resonance exists between the rotational frequency of the
stars in the galaxy and the rotational frequency of the companion galaxy. The number of spiral arms depends strongly on the
particular resonance. In the case where the companion moves in an elliptic orbit, spiral arms are formed when a resonance,
inside the galactic body, exists in almost all the parts of the orbit or, at least, in the largest part of it. 相似文献