Galactoseismology in the Age of Gaia

2017 ◽  
Vol 13 (S334) ◽  
pp. 189-194
Author(s):  
Lawrence M. Widrow ◽  
Matthew H. Chequers
Keyword(s):  
Dark Matter ◽  
Milky Way ◽  
Spiral Structure ◽  
Dwarf Galaxy ◽  
Matter Density ◽  
Observational Evidence ◽  
Time Dependent ◽  
Stellar Disk ◽  
Vertical Force ◽  
Bending Waves

AbstractRecent observations from SEGUE, RAVE, and LAMOST have revealed tantalizing evidence that the local stellar disk of the Milky Way is in a state of disequilibrium. In particular, the disk appears to exhibit bending and breathing waves normal to its midplane within 2 kiloparsecs of our position within the disk. There also appear to be bending waves or corrugations at larger Galactocentric radii. These waves may be linked to other time-dependent disk phenomena such as the bar, spiral structure, and warp, or they may be the result of a passing dark matter subhalo or dwarf galaxy. Here, we discuss the observational evidence for these waves, the theory of bending and breathing waves in (simulated) stellar disks, and implications of disequilibrium for attempts to determine the local vertical force and dark matter density (the Oort problem). We also discuss the types of analyses that one might do with the Gaia database.

scholarly journals Tidal Tails and the Shape of the Dark Matter Halo

2005 ◽  
Vol 22 (3) ◽  
pp. 190-194 ◽  
Author(s):  
Geraint F. Lewis ◽  
Rodrigo A. Ibata
Keyword(s):  
Dark Matter ◽  
Cold Dark Matter ◽  
Milky Way ◽  
Dwarf Galaxy ◽  
Observational Evidence ◽  
Dark Matter Halo ◽  
Dark Matter Halos ◽  
Fundamental Understanding ◽  
Tidal Tails ◽  
Precise Interpretation

AbstractCold dark matter cosmologies successfully accounts for the distribution of matter on large scales. On smaller scales, these cosmological models predict that galaxies like our own Milky Way should be enveloped in massive dark matter halos. Furthermore, these halos should be significantly flattened or even triaxial. Recent observational evidence, drawn from the demise of the Sagittarius dwarf galaxy as it is cannibalized by our own, indicates that the potential of the Milky Way must be close to spherical. While the precise interpretation of the observational evidence is under debate, an apparently spherical halo may signify a pronounced failing of dark matter models, and may even indicate a failure in our fundamental understanding of gravity.

Tidal evolution of dwarf galaxies with shallow dark matter density profiles

2012 ◽  
Vol 10 (H16) ◽  
pp. 346-346
Author(s):  
Ewa L. Łokas
Keyword(s):  
Dark Matter ◽  
Milky Way ◽  
Local Group ◽  
Dwarf Galaxies ◽  
Dwarf Galaxy ◽  
Morphological Evolution ◽  
Matter Density ◽  
Density Profiles ◽  
Tidal Evolution ◽  
Dark Matter Density

AbstractOne of the scenarios for the formation of dwarf spheroidal galaxies in the Local Group proposes that the objects formed from late type dwarfs via tidal interaction with bigger galaxies such as the Milky Way and Andromeda. The scenario naturally explains the morphology-density relation observed for dwarf galaxies in the Local Group. Using N-body simulations we study the long-term tidal evolution of dwarf galaxies in the vicinity of the Milky Way. The dwarf galaxies were initially composed of stellar disks embedded in dark matter haloes of different inner density slopes including shallow ones recently obtained in N-body+hydro simulations of dwarf galaxy formation in isolation. Such progenitors were placed on five different orbits around the Milky Way and their evolution was followed for 10 Gyr. The outcome of the evolution, in terms of the mass loss, morphological transformation and randomization of stellar orbits depends very sensitively on the inner density slope of dark matter. The effects of tides are stronger for dwarfs with shallower slopes; they are more heavily stripped, in some cases down to the scale of ultra-faint satellites of the Milky Way or even dissolved completely with obvious implications for the missing satellites problem. The morphological evolution of the stellar component, from rotationally supported disks to spheroids dominated by random motions, also proceeds faster. In addition, bars which usually form at the first pericenter passage are created more easily and live longer in dwarfs with shallow dark matter density profiles on extended orbits.

scholarly journals The constraining effect of gas and the dark matter halo on the vertical stellar distribution of the Milky Way

2018 ◽  
Vol 617 ◽  
pp. A142 ◽  
Author(s):  
S. Sarkar ◽  
C. J. Jog
Keyword(s):  
Dark Matter ◽  
Gravitational Field ◽  
Milky Way ◽  
Galactic Disk ◽  
Outer Region ◽  
Hydrogen Gas ◽  
Dark Matter Halo ◽  
Stellar Disk ◽  
Disk Thickness ◽  
Vertical Density

We study the vertical stellar distribution of the Milky Way thin disk in detail with particular focus on the outer disk. We treat the galactic disk as a gravitationally coupled, three-component system consisting of stars, atomic hydrogen gas, and molecular hydrogen gas in the gravitational field of the dark matter halo. The self-consistent vertical distribution for stars and gas in such a realistic system is obtained for radii between 4–22 kpc. The inclusion of an additional gravitating component constrains the vertical stellar distribution toward the mid-plane, so that the mid-plane density is higher, the disk thickness is reduced, and the vertical density profile is steeper than in the one-component, isothermal, stars-alone case. We show that the stellar distribution is constrained mainly by the gravitational field of gas and dark matter halo in the inner and the outer Galaxy, respectively. We find that the thickness of the stellar disk (measured as the half-width at half-maximum of the vertical density distribution) increases with radius, flaring steeply beyond R = 17 kpc. The disk thickness is reduced by a factor of 3–4 in the outer Galaxy as a result of the gravitational field of the halo, which may help the disk resist distortion at large radii. The disk would flare even more if the effect of dark matter halo were not taken into account. Thus it is crucially important to include the effect of the dark matter halo when determining the vertical structure and dynamics of a galactic disk in the outer region.

scholarly journals Kinematical & Chemical Characteristics of the Thin and Thick Disks

2008 ◽  
Vol 4 (S254) ◽  
pp. 179-190 ◽  
Author(s):  
Rosemary F. G. Wyse
Keyword(s):  
Dark Matter ◽  
Cold Dark Matter ◽  
Milky Way ◽  
Observational Evidence ◽  
Chemical Characteristics ◽  
Chemical Abundance ◽  
The Galaxy ◽  
History Of ◽  
Thin And Thick Disks ◽  
Thick Disks

AbstractI discuss how the chemical abundance distributions, kinematics and age distributions of stars in the thin and thick disks of the Galaxy can be used to decipher the merger history of the Milky Way, a typical large galaxy. The observational evidence points to a rather quiescent past merging history, unusual in the context of the ‘consensus’ cold-dark-matter cosmology favoured from observations of structure on scales larger than individual galaxies.

scholarly journals Cold Dark Matter Substructure and the Heating of Galactic Disks

2003 ◽  
Vol 208 ◽  
pp. 391-392
Author(s):  
Andreea S. Font ◽  
Julio F. Navarro
Keyword(s):  
Dark Matter ◽  
Cold Dark Matter ◽  
Milky Way ◽  
Dark Matter Halo ◽  
Stellar Disk ◽  
Minor Role ◽  
Galactic Disks ◽  
Cosmological Simulations ◽  
A Minor

We investigate recent suggestions that substructure in cold dark matter (CDM) halos has potentially destructive effects on galactic disks. N-body simulations of disk/bulge models of the Milky Way, embedded in a dark matter halo with substructure similar to that found in cosmological simulations, show that tides from substructure halos play only a minor role in the dynamical heating of the stellar disk. This suggests that substructure might not preclude CDM halos from being acceptable hosts of thin stellar disks.

scholarly journals Search for dark matter signals towards a selection of recently detected DES dwarf galaxy satellites of the Milky Way with H.E.S.S.

2020 ◽  
Vol 102 (6) ◽  
Author(s):  
H. Abdallah ◽  
R. Adam ◽  
F. Aharonian ◽  
F. Ait Benkhali ◽  
E. O. Angüner ◽  
...  
Keyword(s):  
Dark Matter ◽  
Milky Way ◽  
Dwarf Galaxy ◽  
Selection Of

scholarly journals The Canis Major Dwarf Galaxy

2004 ◽  
Vol 21 (4) ◽  
pp. 371-374
Author(s):  
Geraint F. Lewis ◽  
Rodrigo A. Ibata ◽  
Michael J. Irwin ◽  
Nicolas F. Martin ◽  
Michele Bellazzini ◽  
...  
Keyword(s):  
Building Block ◽  
Milky Way ◽  
Galactic Halo ◽  
Galactic Plane ◽  
Dwarf Galaxy ◽  
Observational Evidence ◽  
Thick Disk ◽  
Equatorial Orbit ◽  
Satellite Galaxy

AbstractRecent observational evidence suggests that the Sagittarius dwarf galaxy represents the only major ongoing accretion event in the Galactic halo, accounting for the majority of stellar debris identified there. This paper summarises the recent discovery of another potential Milky Way accretion event, the Canis Major dwarf galaxy. This dwarf satellite galaxy is found to lie just below the Galactic plane and appears to be on an equatorial orbit. Unlike Sagittarius, which is contributing to the Galactic halo, the location and eventual demise of Canis Major suggests that it represents a building block of the thick disk.

scholarly journals In Pursuit of the Least Luminous Galaxies

2010 ◽  
Vol 2010 ◽  
pp. 1-11 ◽  
Author(s):  
Beth Willman
Keyword(s):  
Dark Matter ◽  
Milky Way ◽  
Field Survey ◽  
Dwarf Galaxies ◽  
Dwarf Galaxy ◽  
Wide Field ◽  
Dark Matter Halos ◽  
The Past ◽  
Luminous Galaxies ◽  
Host Stars

The dwarf galaxy companions to the Milky Way are unique cosmological laboratories. With luminosities as low as10−7LMW, they inhabit the lowest mass dark matter halos known to host stars and are presently the most direct tracers of the distribution, mass spectrum, and clustering scale of dark matter. Their resolved stellar populations also facilitate detailed studies of their history and mass content. To fully exploit this potential requires a well-defined census of virtually invisible galaxies to the faintest possible limits and to the largest possible distances. I review the past and present impacts of survey astronomy on the census of Milky Way dwarf galaxy companions and discuss the future of finding ultra-faint dwarf galaxies around the Milky Way and beyond in wide-field survey data.

scholarly journals Determination of the local dark matter density using K-dwarfs from Gaia DR2

2020 ◽  
Vol 240 ◽  
pp. 04002
Author(s):  
M. Dafa Wardana ◽  
Hesti Wulandari ◽  
Sulistiyowati ◽  
Akbar H. Khatami
Keyword(s):  
Dark Matter ◽  
Galactic Disk ◽  
Matter Density ◽  
Solar Neighborhood ◽  
Stellar Disk ◽  
Vertical Position ◽  
Dark Halo ◽  
Detection Rates ◽  
Dark Matter Density ◽  
Gaia Dr2

Local dark matter density, ρdm, is one of the crucial astrophysical inputs for the estimation of detection rates in dark matter direct search experi- ments. Knowing the value also helps us to investigate the shape of the Galactic dark halo, which is of importance for indirect dark matter searches, as well as for various studies in astrophysics and cosmology. In this work, we performed kinematics study of stars in the solar neighborhood to determine the local dark matter density. As tracers we used 95,543 K-dwarfs from Gaia DR2 inside a heliocentric cylinder with a radius of 150 pc and height 200 pc above and below the Galactic mid plane. Their positions and motions were analyzed, assum- ing that the Galaxy is axisymmetric and the tracers are in dynamical equilib- rium. We applied Jeans and Poisson equations to relate the observed quantities, i.e. vertical position and velocity, with the local dark matter density. The tilt term in the Jeans equation is considered to be small and is therefore neglected. Galactic disk is modelled to consist of a single exponential stellar disk, a thin gas layer, and dark matter whose density is constant within the volume consid- ered. Marginalization for the free parameters was performed with Bayesian theorem using Markov Chain Monte Carlo (MCMC) method. We find that ρdm = 0.0116 ± 0.0012 MO/pc or ρdm = 0.439 ± 0.046 GeV/cm3, in agreement within the range of uncertainty with results of several previous studies.

scholarly journals Measure the local dark matter density with LAMOST spectroscopic survey

2015 ◽  
Vol 11 (S317) ◽  
pp. 330-331
Author(s):  
Chao Liu ◽  
Qiran Xia ◽  
Shude Mao
Keyword(s):  
Dark Matter ◽  
Milky Way ◽  
Galactic Disk ◽  
Matter Density ◽  
Dark Matter Halo ◽  
Selection Effects ◽  
Local Rotation ◽  
Dark Matter Density ◽  
The North ◽  
North Galactic

AbstractThe local dark matter density plays the key role in the distribution of the dark matter halo near the Galactic disk. It will also answer whether a dark matter disk exists in the Milky Way. We measure the local dark matter density with LAMOST observed stars located at around the north Galactic pole. The selection effects of the observations are well considered and corrected. We find that the derived DM density, which is around 0.0159+0.0047−0.0057M⊙ pc−3 providing a flat local rotation curve.

Sign in / Sign up

Export Citation Format

Share Document