scholarly journals Dwarfs in the Milky Way halo outer rim: first infall or backsplash satellites?

2020 ◽  
Vol 497 (3) ◽  
pp. 3601-3622
Author(s):  
Matías Blaña ◽  
Andreas Burkert ◽  
Michael Fellhauer ◽  
Marc Schartmann ◽  
Christian Alig
Keyword(s):  
Rest Frame ◽  
Milky Way ◽  
Dark Matter Halo ◽  
Gas Stripping ◽  
Tidal Disruption ◽  
Cosmic Expansion ◽  
The Past ◽  
Systematic Uncertainties ◽  
Virial Mass ◽  
Orbital Solution

ABSTRACT Leo T is a gas-rich dwarf located at $414\, {\rm kpc}$ (1.4Rvir) distance from the Milky Way (MW) and it is currently assumed to be on its first approach. Here, we present an analysis of orbits calculated backwards in time for the dwarf with our new code delorean, exploring a range of systematic uncertainties, e.g.  MW virial mass and accretion, M31 potential, and cosmic expansion. We discover that orbits with tangential velocities in the Galactic standard-of-rest frame lower than $| \vec{u}_{\rm t}^{\rm GSR}| \le 63^{+47}_{-39}\, {\rm km}\, {\rm s}^{\rm -1}$ result in backsplash solutions, i.e. orbits that entered and left the MW dark matter halo in the past, and that velocities above $| \vec{u}_{\rm t}^{\rm GSR}| \ge 21^{+33}_{-21}\, {\rm km}\, {\rm s}^{\rm -1}$ result in wide-orbit backsplash solutions with a minimum pericentre range of $D_{\rm min} \ge 38^{+26}_{-16}\, {\rm kpc}$, which would allow this satellite to survive gas stripping and tidal disruption. Moreover, new proper motion estimates overlap with our orbital solution regions. We applied our method to other distant MW satellites, finding a range of gas stripped backsplash solutions for the gasless Cetus and Eridanus II, providing a possible explanation for their lack of cold gas, while only first infall solutions are found for the H i-rich Phoenix I. We also find that the cosmic expansion can delay their first pericentre passage when compared to the non-expanding scenario. This study explores the provenance of these distant dwarfs and provides constraints on the environmental and internal processes that shaped their evolution and current properties.

The Long View of Planetary Systems

2018 ◽  
Author(s):  
Karel Schrijver
Keyword(s):  
Solar System ◽  
Milky Way ◽  
Planetary Systems ◽  
Giant Planets ◽  
Milky Way Galaxy ◽  
Population Statistics ◽  
The Past ◽  
General Terms ◽  
The Galaxy ◽  
The Universe

How many planetary systems formed before our’s did, and how many will form after? How old is the average exoplanet in the Galaxy? When did the earliest planets start forming? How different are the ages of terrestrial and giant planets? And, ultimately, what will the fate be of our Solar System, of the Milky Way Galaxy, and of the Universe around us? We cannot know the fate of individual exoplanets with great certainty, but based on population statistics this chapter sketches the past, present, and future of exoworlds and of our Earth in general terms.

scholarly journals CONSTRAINTS ON THE SHAPE OF THE MILKY WAY DARK MATTER HALO FROM JEANS EQUATIONS APPLIED TO SLOAN DIGITAL SKY SURVEY DATA

2012 ◽  
Vol 758 (1) ◽  
pp. L23 ◽  
Author(s):  
Sarah R. Loebman ◽  
Željko Ivezić ◽  
Thomas R. Quinn ◽  
Fabio Governato ◽  
Alyson M. Brooks ◽  
...  
Keyword(s):  
Dark Matter ◽  
Survey Data ◽  
Milky Way ◽  
Sloan Digital Sky Survey ◽  
Dark Matter Halo ◽  
Sky Survey

scholarly journals The Dark Matter Halo Density Profile, Spiral Arm Morphology, and Supermassive Black Hole Mass of M33

2011 ◽  
Vol 2011 ◽  
pp. 1-8 ◽  
Author(s):  
Marc S. Seigar
Keyword(s):  
Black Hole ◽  
Dark Matter ◽  
Density Profile ◽  
Pitch Angle ◽  
Rotation Curve ◽  
Dark Matter Halo ◽  
Black Hole Mass ◽  
Supermassive Black Hole ◽  
Virial Mass ◽  
Spiral Arm

We investigate the dark matter halo density profile of M33. We find that the HI rotation curve of M33 is best described by an NFW dark matter halo density profile model, with a halo concentration of and a virial mass of . We go on to use the NFW concentration of M33, along with the values derived for other galaxies (as found in the literature), to show that correlates with both spiral arm pitch angle and supermassive black hole mass.

scholarly journals Double X/Peanut Structures in Barred Galaxies – Insights from an N–body Simulation

2020 ◽  
Author(s):  
Bogdan C Ciambur ◽  
Francesca Fragkoudi ◽  
Sergey Khoperskov ◽  
Paola Di Matteo ◽  
Françoise Combes
Keyword(s):  
Dark Matter ◽  
Milky Way ◽  
Large Fraction ◽  
Formation Time ◽  
Dark Matter Halo ◽  
Barred Galaxies ◽  
Pattern Speed ◽  
Nearby Galaxies ◽  
Dynamical Instabilities ◽  
Bow Tie

Abstract Boxy, peanut– or X–shaped “bulges” are observed in a large fraction of barred galaxies viewed in, or close to, edge-on projection, as well as in the Milky Way. They are the product of dynamical instabilities occurring in stellar bars, which cause the latter to buckle and thicken vertically. Recent studies have found nearby galaxies that harbour two such features arising at different radial scales, in a nested configuration. In this paper we explore the formation of such double peanuts, using a collisionless N–body simulation of a pure disc evolving in isolation within a live dark matter halo, which we analyse in a completely analogous way to observations of real galaxies. In the simulation we find a stable double configuration consisting of two X/peanut structures associated to the same galactic bar – rotating with the same pattern speed – but with different morphology, formation time, and evolution. The inner, conventional peanut-shaped structure forms early via the buckling of the bar, and experiences little evolution once it stabilises. This feature is consistent in terms of size, strength and morphology, with peanut structures observed in nearby galaxies. The outer structure, however, displays a strong X, or “bow-tie”, morphology. It forms just after the inner peanut, and gradually extends in time (within 1 to 1.5 Gyr) to almost the end of the bar, a radial scale where ansae occur. We conclude that, although both structures form, and are dynamically coupled to, the same bar, they are supported by inherently different mechanisms.

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 Is the dark matter halo of the Milky Way flattened?

2006 ◽  
Vol 461 (1) ◽  
pp. 155-169 ◽  
Author(s):  
A. Růžička ◽  
J. Palouš ◽  
C. Theis
Keyword(s):  
Dark Matter ◽  
Milky Way ◽  
Dark Matter Halo

scholarly journals Dark matter halo shapes in the Auriga simulations

2019 ◽  
Vol 490 (4) ◽  
pp. 4877-4888 ◽  
Author(s):  
Jesus Prada ◽  
Jaime E Forero-Romero ◽  
Robert J J Grand ◽  
Rüdiger Pakmor ◽  
Volker Springel
Keyword(s):  
Dark Matter ◽  
Strong Influence ◽  
Milky Way ◽  
Spherical Shape ◽  
Dark Matter Halo ◽  
Observational Constraints ◽  
High Degree ◽  
Level Of Agreement

ABSTRACT We present shape measurements of Milky Way–sized dark matter haloes at redshift z = 0 in a suite of 30 zoom simulations from the Auriga project. We compare the results in full magnetohydrodynamics against dark matter–only simulations and find a strong influence of baryons in making dark matter haloes rounder at all radii compared to their dark matter–only counterparts. At distances ≲30 kpc, rounder dark matter distributions correlate with extended massive stellar discs and low-core gas densities. We measure the alignment between the halo and the disc shapes at different radii and find a high degree of alignment at all radii for most of the galaxies. In some cases, the alignment significantly changes as a function of radius implying that the halo shape twists; this effect correlates with recently formed bulges and is almost absent in the dark matter–only simulations. In a comparison against observational constraints, we find that $20{{\ \rm per\ cent}}$ of haloes in our sample are consistent with observational results derived from the Pal 5 stream that favours an almost spherical shape. Including baryons is a required element to achieve this level of agreement. In contrast, none of the simulations (neither dark matter only nor with baryons) match the constraints derived from the Sagittarius stream that favour an oblate dark matter halo.

The 111 and 129 GeVγ-ray lines from annihilations in the Milky Way dark matter halo, dark disk and subhalos

2013 ◽  
Vol 8 (3) ◽  
pp. 4-18
Author(s):  
Ilias Cholis ◽  
Haril Nurbiantoro Santosa ◽  
Maryam Tavakoli ◽  
Piero Ullio
Keyword(s):  
Dark Matter ◽  
Milky Way ◽  
Dark Matter Halo

scholarly journals The Magellanic Group and the Seven Dwarfs

2008 ◽  
Vol 4 (S256) ◽  
pp. 473-478 ◽  
Author(s):  
Elena D'Onghia ◽  
George Lake
Keyword(s):  
Velocity Distribution ◽  
Galaxy Formation ◽  
Milky Way ◽  
Dwarf Galaxies ◽  
Magellanic Clouds ◽  
Tidal Disruption ◽  
Circular Velocity ◽  
Orbital Configuration

AbstractThe Magellanic Clouds were the largest members of a group of dwarf galaxies that entered the Milky Way (MW) halo at late times. This group, dominated by the LMC, contained ~4% of the mass of the Milky Way prior to its accretion and tidal disruption, but ≈70% of the known dwarfs orbiting the MW. Our theory addresses many outstanding problems in galaxy formation associated with dwarf galaxies. First, it can explain the planar orbital configuration populated by some dSphs in the MW. Second, it provides a mechanism for lighting up a subset of dwarf galaxies to reproduce the cumulative circular velocity distribution of the satellites in the MW. Finally, our model predicts that most dwarfs will be found in association with other dwarfs. The recent discovery of Leo V (Belokurov et al. 2008), a dwarf spheroidal companion of Leo IV, and the nearby dwarf associations supports our hypothesis.

scholarly journals Hypervelocity star candidates in Gaia DR1/TGAS

2017 ◽  
Vol 12 (S330) ◽  
pp. 181-184
Author(s):  
T. Marchetti ◽  
E. M. Rossi ◽  
G. Kordopatis ◽  
A. G. A. Brown ◽  
A. Rimoldi ◽  
...  
Keyword(s):  
Neural Network ◽  
Data Mining ◽  
Rest Frame ◽  
Milky Way ◽  
Galactic Centre ◽  
Predicted Probability ◽  
Data Release ◽  
Galactic Potentials ◽  
Escape Speed ◽  
Total Velocity

AbstractHypervelocity stars (HVSs) are characterized by a total velocity in excess of the Galactic escape speed, and with trajectories consistent with coming from the Galactic Centre. We apply a novel data mining routine, an artificial neural network, to discover HVSs in the TGAS subset of the first data release of the Gaia satellite, using only the astrometry of the stars. We find 80 stars with a predicted probability >90% of being HVSs, and we retrieved radial velocities for 47 of those. We discover 14 objects with a total velocity in the Galactic rest frame >400 km s−1, and 5 of these have a probability >50% of being unbound from the Milky Way. Tracing back orbits in different Galactic potentials, we discover 1 HVS candidate, 5 bound HVS candidates, and 5 runaway star candidates with remarkably high velocities, between 400 and 780 km s−1. We wait for future Gaia releases to confirm the goodness of our sample and to increase the number of HVS candidates.

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