Stalling of globular cluster orbits in dwarf galaxies.
KAUR K. and SRIDHAR S.
Abstract (from CDS):
We apply the Tremaine-Weinberg theory of dynamical friction to compute the orbital decay of a globular cluster (GC) on an initially circular orbit inside a cored spherical galaxy with isotropic stellar velocities. The retarding torque on the GC, T (rp)< 0, is a function of its orbital radius rp. The torque is exerted by stars whose orbits are resonant with the GC's orbit and given as a sum over the infinitely many possible resonances by the Lynden-Bell-Kalnajs (LBK) formula. We calculate the LBK torque T (rp) and determine rp(t) for a GC of mass Mp=2×105M☉ and an isochrone galaxy of core mass Mc=4×108M☉ and core radius b=1000pc. (i) When rp≳300pc, many strong resonances are active, and as expected, T ~TC, the classical Chandrasekhar torque. (ii) For rp< 300pc, T comes mostly from stars nearly corotating with the GC, trailing or leading it slightly; trailing resonances exert stronger torques. (iii) As rp decreases, the number and strength of resonances drop, so | T | also decreases, with | T | < 10–2| TC| at rp=r*≃(Mp/Mc)1/5b≃220pc, a characteristic "filtering" radius. (iv) Many resonances cease to exist inside r*; this includes all leading and low-order trailing ones. (v) The higher-order trailing resonances inside r* are very weak, with | T | < 10–4| TC| at rp=150pc. (vi) Inspiral times for rp(t) to decay from 300pc to r* far exceed 10Gyr.
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Syntax of coordinates is : "ra dec (wtype) [error ellipse] quality bibcode" :
ra dec : right ascension and declination (unit and frame defined according to your Output Options)
Grey values are increasing the original precision due to the computation of frame transformations
(wtype) : wavelength class for the origin of the coordinates (Rad, mm, IR, Optical, UV, Xray, Gam)
[error ellipse] : measurement uncertainty, on (ra,dec) if the positional angle is 90 degrees, on (majaxis,minaxis) otherwise (in mas at defined epoch in the original catalogue),
position angle (in degrees North celestial pole to East)
Syntax of coordinates is : "ra dec (wtype) [error ellipse] quality bibcode" :
ra dec : right ascension and declination (unit and frame defined according to your Output Options)
Grey values are increasing the original precision due to the computation of frame transformations
(wtype) : wavelength class for the origin of the coordinates (Rad, mm, IR, Optical, UV, Xray, Gam)
[error ellipse] : measurement uncertainty, on (ra,dec) if the positional angle is 90 degrees, on (majaxis,minaxis) otherwise (in mas at defined epoch in the original catalogue),
position angle (in degrees North celestial pole to East)
quality : flag of quality
E ≥ 10"
D : 1-10" (and some old data)
C : 0.1-1"
B : 0.01-0.1" + 2MASS, Tyc
A : VLBI, Hipparcos
bibcode : bibcode of the coordinates reference
FK4
coord.
(ep=B1950 eq=1950) :
02 37 55.0 -34 39 48
[
8000 8000 90
]
Syntax of coordinates is : "ra dec (wtype) [error ellipse] quality bibcode" :
ra dec : right ascension and declination (unit and frame defined according to your Output Options)
Grey values are increasing the original precision due to the computation of frame transformations
(wtype) : wavelength class for the origin of the coordinates (Rad, mm, IR, Optical, UV, Xray, Gam)
[error ellipse] : measurement uncertainty, on (ra,dec) if the positional angle is 90 degrees, on (majaxis,minaxis) otherwise (in mas at defined epoch in the original catalogue),
position angle (in degrees North celestial pole to East)
quality : flag of quality
E ≥ 10"
D : 1-10" (and some old data)
C : 0.1-1"
B : 0.01-0.1" + 2MASS, Tyc
A : VLBI, Hipparcos
bibcode : bibcode of the coordinates reference
Gal
coord.
(ep=J2000) :
237.1038 -65.6515
[
8000 8000 90
]
Syntax of proper motions is : "pm-ra pm-dec [error ellipse] quality bibcode"
pm-ra : mu-ra*cos(dec) (expressed in the ICRS system in mas/yr)
pm-dec : mu-dec (expressed in the ICRS system in mas/yr)
[error ellipse] : error major axis and minor axis (in mas), orientation angle (in deg)
quality : flag of quality (A=best quality -> E=worst quality, {� } =unknown quality)
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quality : flag of quality ( A=best quality -> E=worst quality, ∼=unknown quality)
References (1744 between 1850 and 2024) (Total 1744)
Simbad bibliographic survey began in 1850 for stars (at least bright stars) and in 1983 for all other objects (outside the solar system).
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