scholarly journals Age and Mass of the Local Group from Satellite Galaxy Dynamics

1999 ◽  
Vol 192 ◽  
pp. 420-426
Author(s):  
Alan B. Whiting
Keyword(s):  
Time Scale ◽  
Local Group ◽  
Galaxy Dynamics ◽  
Cosmological Time ◽  
Satellite Galaxy ◽  
Satellite Galaxies

The present kinematics of an unrelaxed system such as the Local Group can be used to investigate its dynamics on a cosmological time scale. In particular, the classical timing argument of Kahn & Woltjer may be extended to distant satellite galaxies of the Local Group whose distances and velocities are known with some accuracy. Including a correction for the fact that the Local Group was not always dynamically isolated, I derive a mass for the Group of about 1.6 x 1012M⊙ and an age of 1.0 to 1.2 x 1010 years.

scholarly journals Phase-Space Correlations among Systems of Satellite Galaxies

Galaxies ◽  
2021 ◽  
Vol 9 (3) ◽  
pp. 66
Author(s):  
Marcel S. Pawlowski
Keyword(s):  
Phase Space ◽  
Local Group ◽  
Tangential Velocity ◽  
Research Literature ◽  
Highly Active ◽  
Satellite Galaxy ◽  
Different Types ◽  
Motion Measurements ◽  
Satellite Galaxies ◽  
Observational Knowledge

Driven by the increasingly complete observational knowledge of systems of satellite galaxies, mutual spatial alignments and relations in velocities among satellites belonging to a common host have become a productive field of research. Numerous studies have investigated different types of such phase-space correlations and were met with varying degrees of attention by the community. The Planes of Satellite Galaxies issue is maybe the best-known example, with a rich field of research literature and an ongoing, controversial debate on how much of a challenge it poses to the ΛCDM model of cosmology. Another type of correlation, the apparent excess of close pairs of dwarf galaxies, has received considerably less attention despite its reported tension with ΛCDM expectations. With the fast expansion of proper motion measurements in recent years, largely driven by the Gaia mission, other peculiar phase-space correlations have been uncovered among the satellites of the Milky Way. Examples are the apparent tangential velocity excess of satellites compared to cosmological expectations, and the unexpected preference of satellites to be close to their pericenters. At the same time, other kinds of correlations have been found to be more in line with cosmological expectations—specifically, lopsided satellite galaxy systems and the accretion of groups of satellite galaxies. The latter has mostly been studied in cosmological simulations thus far, but it offers the potential to address some of the other issues by providing a way to produce correlations among the orbits of a group’s satellite galaxy members. This review is the first to provide an introduction to the highly active field of phase-space correlations among satellite galaxy systems. The emphasis is on summarizing existing, recent research and highlighting interdependencies between the different, currently almost exclusively individually considered types of correlations. Future prospects in light of upcoming observational facilities and our ever-expanding knowledge of satellite galaxy systems beyond the Local Group are also briefly discussed.

scholarly journals The origin of lopsided satellite galaxy distribution in galaxy pairs

2019 ◽  
Vol 488 (3) ◽  
pp. 3100-3108 ◽  
Author(s):  
Chen Chris Gong ◽  
Noam I Libeskind ◽  
Elmo Tempel ◽  
Quan Guo ◽  
Stefan Gottlöber ◽  
...  
Keyword(s):  
Cold Dark Matter ◽  
Local Group ◽  
Sloan Digital Sky Survey ◽  
Host Galaxies ◽  
The Past ◽  
Satellite Galaxy ◽  
Galaxy Distribution ◽  
Sky Survey ◽  
Satellite Galaxies ◽  
Set Up

ABSTRACT It is well known that satellite galaxies are not isotropically distributed among their host galaxies as suggested by most interpretations of the Λ cold dark matter (ΛCDM) model. One type of anisotropy recently detected in the Sloan Digital Sky Survey (and seen when examining the distribution of satellites in the Local Group and in the Centaurus group) is a tendency to be so-called lopsided. Namely, in pairs of galaxies (like Andromeda and the Milky Way) the satellites are more likely to inhabit the region in between the pair, rather than on opposing sides. Although recent studies found a similar set-up when comparing pairs of galaxies in ΛCDM simulations indicating that such a set-up is not inconsistent with ΛCDM, the origin has yet to be explained. Here we examine the origin of such lopsided set-ups by first identifying such distributions in pairs of galaxies in numerical cosmological simulations, and then tracking back the orbital trajectories of satellites (which at z = 0 display the effect). We report two main results: first, the lopsided distribution was stronger in the past and weakens towards z = 0. Secondly, the weakening of the signal is due to the interaction of satellite galaxies with the pair. Finally, we show that the z = 0 signal is driven primarily by satellites that are on first approach, who have yet to experience a ‘flyby’. This suggests that the signal seen in the observations is also dominated by dynamically young accretion events.

VARIABILITY PROPERTIES OF SWIFT-BAT GAMMA-RAY BURSTS

2011 ◽  
Vol 20 (10) ◽  
pp. 1969-1973 ◽  
Author(s):  
RAFFAELLA MARGUTTI ◽  
CRISTIANO GUIDORZI ◽  
GUIDO CHINCARINI
Keyword(s):  
Energy Range ◽  
Time Scales ◽  
Time Scale ◽  
Rest Frame ◽  
Gamma Ray ◽  
Timing Analysis ◽  
Gamma Ray Bursts ◽  
Cosmological Time ◽  
The Time Domain ◽  
Prompt Emission

We study the variability properties of the prompt emission of Gamma-Ray Bursts in the gamma-ray energy range. We use the power spectrum analysis in the time domain as developed by [Margutti, in preparation]; this technique is suitable to study the rms variations at different time scales. The timing analysis of 252 Swift light-curves in the 15–150 keV energy range reveals the existence of different variability classes. Moreover, after accounting for the cosmological time dilation, the distribution of the GRB characteristic variability time scales is found to cluster around 0.6–1 s we identify this time scale as a characteristic variability time scale of long GRBs in the source rest frame.

scholarly journals The effects of photoionization on galaxy formation - II. Satellite galaxies in the Local Group

2002 ◽  
Vol 333 (1) ◽  
pp. 177-190 ◽  
Author(s):  
A. J. Benson ◽  
C. S. Frenk ◽  
C. G. Lacey ◽  
C. M. Baugh ◽  
S. Cole
Keyword(s):  
Galaxy Formation ◽  
Local Group ◽  
Satellite Galaxies

scholarly journals The preferred direction of infalling satellite galaxies in the Local Group

2010 ◽  
Vol 411 (3) ◽  
pp. 1525-1535 ◽  
Author(s):  
Noam I. Libeskind ◽  
Alexander Knebe ◽  
Yehuda Hoffman ◽  
Stefan Gottlöber ◽  
Gustavo Yepes ◽  
...  
Keyword(s):  
Local Group ◽  
Preferred Direction ◽  
Satellite Galaxies

scholarly journals Warm dark matter model with a few keV mass is bad for the too-big-to-fail problem

2019 ◽  
Vol 491 (2) ◽  
pp. 2520-2535 ◽  
Author(s):  
Xi Kang
Keyword(s):  
Dark Matter ◽  
Star Formation ◽  
Analytical Description ◽  
Realistic Model ◽  
Analytical Models ◽  
Satellite Galaxy ◽  
The Galaxy ◽  
Dynamical Simulations ◽  
Satellite Galaxies ◽  
Tidal Heating

ABSTRACT Theoretical studying of the very inner structure of faint satellite galaxy requires very high-resolution hydro-dynamical simulations with realistic model for star formation, which are beginning to emerge recently. In this work, we present an analytical description to model the inner kinematic of satellites in the Milky Way (MW). We use a Monte Carlo method to produce merger trees for MW mass halo and analytical models to produce stellar mass in the satellite galaxies. We consider two important processes which can significantly modify the inner mass distribution in satellite galaxy. The first is baryonic feedback which can induce a flat inner profile depending on the star formation efficiency in the galaxy. The second is the tidal stripping to reduce and re-distribute the mass inside satellite. We apply this model to MW satellite galaxies in both CDM and thermal relic WDM models. It is found that tidal heating must be effective to produce a relatively flat distribution of the satellite circular velocities, to agree with the data. The constraint on WDM mass depends on the host halo mass. For a MW halo with dark matter mass lower than $2\times 10^{12}\, \text{ M}_\odot$, a 2 keV WDM model can be safely excluded as the predicted satellite circular velocities are systematically lower than the data. For WDM with mass of 3.5 keV, it requires the MW halo mass to be larger than $1.5\times 10^{12}\, {\text{ M}}_{\odot }$.

scholarly journals The shape alignment of satellite galaxies in Local Group-like pairs from the SDSS

2019 ◽  
Vol 484 (3) ◽  
pp. 4325-4336 ◽  
Author(s):  
Peng Wang ◽  
Quan Guo ◽  
Noam I Libeskind ◽  
Elmo Tempel ◽  
Chengliang Wei ◽  
...  
Keyword(s):  
Local Group ◽  
Shape Alignment ◽  
Satellite Galaxies
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