J/MNRAS/486/5924 Dark matter halo and stellar stream asymmetry (Kipper+, 2019)
The influence of dark matter halo on the stellar stream asymmetry via dynamical
friction.
Kipper R., Tenjes P., Hutsi G., Tuvikene T., Tempel E.
<Mon. Not. R. Astron. Soc., 486, 5924-5933 (2019)>
=2019MNRAS.486.5924K 2019MNRAS.486.5924K (SIMBAD/NED BibCode)
ADC_Keywords: Clusters, globular ; Stars, halo ; Optical
Keywords: globular clusters: general - Galaxy: kinematics and dynamics -
dark matter
Abstract:
We study the effect of dynamical friction on globular clusters (GCs)
and on the stars evaporated from the GCs (stellar streams) moving in
the Galactic halo. Due to dynamical friction, the position of a GC as
a stream progenitor starts to shift with respect to its original
position in the reference frame of initial GC orbit. Therefore the
stars that have evaporated at different times have different mean
position with respect to the GC position. This shifting results in a
certain asymmetry in stellar density distribution between the leading
and trailing arms of the stream. The degree of the asymmetry depends
on the characteristics of the environment in which the GC and the
stream stars move. As GCs are located mainly in outer parts of a
galaxy, this makes dynamical friction a unique probe to constrain the
underlying dark matter spatial density and velocity distributions. For
a GC NGC 3201 we compared our theoretical shift estimates with
available observations. Due to large uncertainties in current
observation data, we can only conclude that the derived estimates have
the same order of magnitude.
Description:
We estimated how much the effect of dynamical friction influences the
asymmetry of GC stellar streams. The constant lagging of a GC behind
on its orbit when compared with the stream stars produces a shift of
the GC with respect to the previously evaporated stars and thus an
asymmetry between the leading and trailing parts of the stream. Thus,
the distribution of recently evaporated stars is preferably more
lopsided compared to the earlier evaporated stars. From the
observational perspective, it is seen as an asymmetry in surface
density distributions between the two branches of the stellar stream.
We calculated shifts (Δx) of the progenitor GC and its
evaporated stream stars with respect to the initial position of the
progenitor GC or the centre of the symmetry of the oldest parts of the
stream. In most cases, either calculated shifts are too small to be
detected within current observational data, or pericentres of GC
orbits are too near the MW central bar, which can be another source of
asymmetry in observed stellar streams. Although there are numerous
hindrances, it should still be possible to study the dark matter by
taking these effects into account and provided deep photometric
observations of the stream. The diversity of the distances,
evaporation histories, and densities of the streams do not allow us to
deduce a certain brightness limit for needed observations.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tablea1.dat 59 149 Complete table of dynamical friction estimates
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Byte-by-byte Description of file: tablea1.dat
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Bytes Format Units Label Explanations
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1- 12 A12 --- Name Globular cluster name
14- 19 F6.2 deg GLON Galactic longitude of the GC
21- 26 F6.2 deg GLAT Galactic latitude of the GC
28- 32 F5.1 kpc Dist Distance of the GC from the Sun
34- 37 I4 pc Dxiso Estimation of shift along the orbit produced
by dynamical friction from only dark matter
over the 5Gyr time span (isotropic) (1)
39- 43 F5.2 deg DPhiiso Angular shift representing the angular
distance between the GC and stream centre
along the orbit as viewed from the
Sun (isotropic) (1)
45- 48 I4 pc Dxa Estimation of shift along the orbit produced
by dynamical friction from only dark matter
over the 5Gyr time span (anisotropic) (2)
50- 53 F4.2 deg DPhia Angular shift representing the angular
distance between the GC and stream centre
along the orbit as viewed from the
Sun (anisotropic) (2)
55- 59 F5.1 kpc Peri Pericentre
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Note (1): Calculations made assuming isotropic dark matter particle velocity
dispersion tensor
Note (2): Calculations made assuming constant anisotropic dark matter particle
velocity dispersion tensor with the anisotropy value adopted from
stellar halo
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History:
From electronic version of the journal
(End) Ana Fiallos [CDS] 08-Nov-2022