Ram pressure drag - the effects of ram pressure on dark matter and stellar disc dynamics

ABSTRACT Several white dwarfs (WDs) with atmospheric metal pollution have been found to host small planetary bodies (planetesimals) orbiting near the tidal disruption radius. We study the physical properties and dynamical origin of these bodies under the hypothesis that they underwent high-eccentricity migration from initial distances of several astronomical units. We examine two plausible mechanisms for orbital migration and circularization: tidal friction and ram-pressure drag in a compact disc. For each mechanism, we derive general analytical expressions for the evolution of the orbit that can be rescaled for various situations. We identify the physical parameters that determine whether a planetesimal’s orbit can circularize within the appropriate time-scale and constrain these parameters based on the properties of the observed systems. For tidal migration to work, an internal viscosity similar to that of molten rock is required, and this may be naturally produced by tidal heating. For disc migration to operate, a minimal column density of the disc is implied; the inferred total disc mass is consistent with estimates of the total mass of metals accreted by polluted WDs.

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Kinematic properties and dark matter fraction of Virgo dwarf early-type galaxies

Proceedings of the International Astronomical Union ◽

10.1017/s1743921314005997 ◽

2012 ◽

Vol 10 (H16) ◽

pp. 335-335

Author(s):

E. Toloba ◽

A. Boselli ◽

R. Peletier ◽

J. Gorgas

Keyword(s):

Dark Matter ◽

Galaxy Evolution ◽

Dwarf Galaxies ◽

Elliptical Galaxies ◽

Virgo Cluster ◽

Early Type ◽

Late Type ◽

Fundamental Plane ◽

Ram Pressure ◽

Kinematic Properties

AbstractWhat happens to dwarf galaxies as they enter the cluster potential well is one of the main unknowns in studies of galaxy evolution. Several evidence suggests that late-type galaxies enter the cluster and are transformed to dwarf early-type galaxies (dEs). We study the Virgo cluster to understand which mechanisms are involved in this transformation. We find that the dEs in the outer parts of Virgo have rotation curves with shapes and amplitudes similar to late-type galaxies of the same luminosity (Fig. 1). These dEs are rotationally supported, have disky isophotes, and younger ages than those dEs in the center of Virgo, which are pressure supported, often have boxy isophotes and are older (Fig. 1). Ram pressure stripping, thus, explains the properties of the dEs located in the outskirts of Virgo. However, the dEs in the central cluster regions, which have lost their angular momentum, must have suffered a more violent transformation. A combination of ram pressure stripping and harassment is not enough to remove the rotation and the spiral/disky structures of these galaxies. We find that on the the Faber-Jackson and the Fundamental Plane relations dEs deviate from the trends of massive elliptical galaxies towards the position of dark matter dominated systems such as the dwarf spheroidal satellites of the Milky Way and M31. Both, rotationally and pressure supported dEs, however, populate the same region in these diagrams. This indicates that dEs have a non-negligible dark matter fraction within their half light radius.

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The twisted dark matter halo of the Milky Way

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa3883 ◽

2020 ◽

Author(s):

Shi Shao ◽

Marius Cautun ◽

Alis Deason ◽

Carlos S Frenk

Keyword(s):

Dark Matter ◽

Milky Way ◽

Orbital Plane ◽

Minor Axis ◽

Dark Matter Halo ◽

Misalignment Angle ◽

Stellar Disc ◽

Confidence Levels ◽

The Common ◽

Inner Parts

Abstract We analyse systems analogous to the Milky Way (MW) in the eagle cosmological hydrodynamics simulation in order to deduce the likely structure of the MW’s dark matter halo. We identify MW-mass haloes in the simulation whose satellite galaxies have similar kinematics and spatial distribution to those of the bright satellites of the MW, specifically systems in which the majority of the satellites (8 out of 11) have nearly co-planar orbits that are also perpendicular to the central stellar disc. We find that the normal to the common orbital plane of the co-planar satellites is well aligned with the minor axis of the host dark matter halo, with a median misalignment angle of only 17.3○. Based on this result, we infer that the minor axis of the Galactic dark matter halo points towards (l, b) = (182○, −2○), with an angular uncertainty at the 68 and 95 percentile confidence levels of 22○ and 43○ respectively. Thus, the inferred minor axis of the MW halo lies in the plane of the stellar disc. The halo, however, is not homologous and its flattening and orientation vary with radius. The inner parts of the halo are rounder than the outer parts and well aligned with the stellar disc (that is the minor axis of the halo is perpendicular to the disc). Further out, the halo twists and the minor axis changes direction by 90○. This twist occurs over a very narrow radial range and reflects variations in the filamentary network along which mass was accreted into the MW.

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Small Group Dynamics and Extended Gas

International Astronomical Union Colloquium ◽

10.1017/s0252921100054907 ◽

2000 ◽

Vol 174 ◽

pp. 148-153

Author(s):

F. Combes

Keyword(s):

Dark Matter ◽

Small Group ◽

Group Dynamics ◽

Small Groups ◽

Gas Dynamics ◽

X Rays ◽

Galaxy Interactions ◽

Galaxy Groups ◽

Hot Gas ◽

Ram Pressure

AbstractInteractions between galaxies have spectacular effects on gas dynamics, and small galaxy groups are a privileged place to investigate them. In particular, they could test the existence of cold H2 gas as dark matter in the outer parts of galaxies. HI observations have revealed that galaxies in small groups are deficient in atomic gas, like in richer galaxy clusters such as Virgo, although in a lesser extent. Galaxy interactions could be the cause of this deficiency, stripping the gas out of galaxies and enriching the inter-cluster medium (ICM) in hot gas, which in turn strips gas through ram pressure. Alternatively, the gas present at the formation of the group could have been heated to its virial temperature, and be observed now as X-rays. The dynamical processes related to this extended gas in small galaxy groups are reviewed.

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GASP

Astronomy and Astrophysics ◽

10.1051/0004-6361/202037759 ◽

2020 ◽

Vol 640 ◽

pp. A22 ◽

Cited By ~ 1

Author(s):

M. Ramatsoku ◽

P. Serra ◽

B. M. Poggianti ◽

A. Moretti ◽

M. Gullieuszik ◽

...

Keyword(s):

Star Formation ◽

Star Formation Rate ◽

Formation Rate ◽

Stellar Mass ◽

Gas Stripping ◽

Rich Cluster ◽

Very Large Array ◽

Stellar Disc ◽

Ram Pressure ◽

Restoring Forces

We present atomic hydrogen (H I) observations with the Jansky Very Large Array of one of the jellyfish galaxies in the GAs Stripping Phenomena sample, JO201. This massive galaxy (M* = 3.5 × 1010 M⊙) is falling along the line-of-sight towards the centre of a rich cluster (M200 ∼ 1.6 × 1015 M⊙, σcl ∼ 982 ± 55 km s−1) at a high velocity ≥3363 km s−1. Its Hα emission shows a ∼40 kpc tail, which is closely confined to its stellar disc and a ∼100 kpc tail extending further out. We find that H I emission only coincides with the shorter clumpy Hα tail, while no H I emission is detected along the ∼100 kpc Hα tail. In total, we measured an H I mass of MHI = 1.65 × 109 M⊙, which is about 60% lower than expected based on its stellar mass and stellar surface density. We compared JO201 to another jellyfish in the GASP sample, JO206 (of a similar mass but living in a ten times less massive cluster), and we find that they are similarly H I-deficient. Of the total H I mass in JO201, about 30% lies outside the galaxy disc in projection. This H I fraction is probably a lower limit since the velocity distribution shows that most of the H I is redshifted relative to the stellar disc and could be outside the disc. The global star formation rate (SFR) analysis of JO201 suggests an enhanced star formation for its observed H I content. The observed SFR would be expected if JO201 had ten times its current H I mass. The disc is the main contributor of the high star formation efficiency at a given H I gas density for both galaxies, but their tails also show higher star formation efficiencies compared to the outer regions of field galaxies. Generally, we find that JO201 and JO206 are similar based on their H I content, stellar mass, and star formation rate. This finding is unexpected considering their different environments. A toy model comparing the ram pressure of the intracluster medium (ICM) versus the restoring forces of these galaxies suggests that the ram pressure strength exerted on them could be comparable if we consider their 3D orbital velocities and radial distances relative to the clusters.

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Galaxies lacking dark matter in the Illustris simulation

Astronomy and Astrophysics ◽

10.1051/0004-6361/201833771 ◽

2019 ◽

Vol 626 ◽

pp. A47 ◽

Cited By ~ 10

Author(s):

M. Haslbauer ◽

J. Dabringhausen ◽

P. Kroupa ◽

B. Javanmardi ◽

I. Banik

Keyword(s):

Dark Matter ◽

Dwarf Galaxies ◽

Dwarf Galaxy ◽

Large Magellanic Cloud ◽

Early Type ◽

Number Density ◽

The Standard Model ◽

Ram Pressure ◽

Self Consistent ◽

First Time

Context. Any viable cosmological model in which galaxies interact predicts the existence of primordial and tidal dwarf galaxies (TDGs). In particular, in the standard model of cosmology (ΛCDM), according to the dual dwarf galaxy theorem, there must exist both primordial dark matter-dominated and dark matter-free TDGs with different radii. Aims. We study the frequency, evolution, and properties of TDGs in a ΛCDM cosmology. Methods. We use the hydrodynamical cosmological Illustris-1 simulation to identify TDG candidates (TDGCs) and study their present-day physical properties. The positions of galaxies in the radius–mass plane, depending on their nonbaryonic content, are compared with observational data and other simulations. We also present movies on the formation of a few galaxies lacking dark matter, confirming their tidal dwarf nature. Tidal dwarf galaxy candidates can however also be formed via other mechanisms, such as from ram-pressure-stripped material or, speculatively, from cold-accreted gas. Results. We find 97 TDGCs with Mstellar > 5 × 107M⊙ at redshift z = 0, corresponding to a co-moving number density of 2.3 × 10−4 h3 cMpc−3. The most massive TDGC has Mtotal = 3.1 × 109 M⊙, comparable to that of the Large Magellanic Cloud. Tidal dwarf galaxy candidates are phase-space-correlated, reach high metallicities, and are typically younger than dark matter-rich dwarf galaxies. Conclusions. We report for the first time the verification of the dual dwarf theorem in a self-consistent ΛCDM cosmological simulation. Simulated TDGCs and dark matter-dominated galaxies populate different regions in the radius–mass diagram in disagreement with observations of early-type galaxies. The dark matter-poor galaxies formed in Illustris-1 have comparable radii to observed dwarf galaxies and to TDGs formed in other galaxy-encounter simulations. In Illustris-1, only 0.17 percent of all selected galaxies with Mstellar = 5 × 107−109 M⊙ are TDGCs or dark matter-poor dwarf galaxies. The occurrence of NGC 1052-DF2-type objects is discussed.

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Modeling a high velocity LMC: The formation of the Magellanic Stream

Proceedings of the International Astronomical Union ◽

10.1017/s1743921308028330 ◽

2008 ◽

Vol 4 (S256) ◽

pp. 117-121

Author(s):

Chiara Mastropietro

Keyword(s):

Dark Matter ◽

Vertical Structure ◽

Milky Way ◽

Large Magellanic Cloud ◽

Low Density ◽

Dark Matter Halos ◽

Tidal Forces ◽

Ram Pressure ◽

Self Consistent ◽

Magellanic Stream

AbstractI use high resolution N-body/SPH simulations to model the new proper motion of the Large Magellanic Cloud (LMC) within the Milky Way (MW) halo and investigate the effects of gravitational and hydrodynamical forces on the formation of the Magellanic Stream (MS). Both the LMC and the MW are fully self consistent galaxy models embedded in extended cuspy ΛCDM dark matter halos. I find that ram-pressure from a low density ionized halo is sufficient to remove a large amount of gas from the LMC's disk forming a trailing Stream that extends more than 120 degrees from the Cloud. Tidal forces elongate the satellite's disk but do not affect its vertical structure. No stars become unbound showing that tidal stripping is almost effectless.

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WALLABY early science – III. An H i study of the spiral galaxy NGC 1566

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stz1448 ◽

2019 ◽

Vol 487 (2) ◽

pp. 2797-2817 ◽

Cited By ~ 6

Author(s):

A Elagali ◽

L Staveley-Smith ◽

J Rhee ◽

O I Wong ◽

A Bosma ◽

...

Keyword(s):

Dark Matter ◽

Spiral Galaxy ◽

Atomic Hydrogen ◽

Mass Fraction ◽

Rotation Curve ◽

Stellar Mass ◽

Hydrogen Gas ◽

Dark Matter Halo ◽

Ram Pressure ◽

Interacting Systems

ABSTRACT This paper reports on the atomic hydrogen gas (H i) observations of the spiral galaxy NGC 1566 using the newly commissioned Australian Square Kilometre Array Pathfinder radio telescope. We measure an integrated H i flux density of $180.2$ Jy km s−1 emanating from this galaxy, which translates to an H i mass of $1.94\times 10^{10}\, \mathrm{ M}_{\odot }$ at an assumed distance of $21.3$ Mpc. Our observations show that NGC 1566 has an asymmetric and mildly warped H i disc. The H i-to-stellar mass fraction (M$_{\rm{H\,{{\small I}}}}$/M∗) of NGC 1566 is 0.29, which is high in comparison with galaxies that have the same stellar mass ($10^{10.8}$ M⊙). We also derive the rotation curve of this galaxy to a radius of $50$ kpc and fit different mass models to it. The NFW, Burkert, and pseudo-isothermal dark matter halo profiles fit the observed rotation curve reasonably well and recover dark matter fractions of 0.62, 0.58, and 0.66, respectively. Down to the column density sensitivity of our observations ($N_{\rm{H\,{{\small I}}}}\, =\, 3.7\times 10^{19}$ cm−2), we detect no H i clouds connected to, or in the nearby vicinity of, the H i disc of NGC 1566 nor nearby interacting systems. We conclude that, based on a simple analytic model, ram pressure interactions with the IGM can affect the H i disc of NGC 1566 and is possibly the reason for the asymmetries seen in the H i morphology of NGC 1566.

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Formation of ultra-diffuse galaxies in the field and in galaxy groups

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stz1499 ◽

2019 ◽

Vol 487 (4) ◽

pp. 5272-5290 ◽

Cited By ~ 21

Author(s):

Fangzhou Jiang ◽

Avishai Dekel ◽

Jonathan Freundlich ◽

Aaron J Romanowsky ◽

Aaron A Dutton ◽

...

Keyword(s):

Dark Matter ◽

Star Formation ◽

Formation Rate ◽

Mass Range ◽

High Threshold ◽

Gas Stripping ◽

Galaxy Groups ◽

Field Versus ◽

Prolate Shape ◽

Ram Pressure

ABSTRACT We study ultra-diffuse galaxies (UDGs) in zoom in cosmological simulations, seeking the origin of UDGs in the field versus galaxy groups. We find that while field UDGs arise from dwarfs in a characteristic mass range by multiple episodes of supernova feedback (Di Cintio et al.), group UDGs may also form by tidal puffing up and they become quiescent by ram-pressure stripping. The field and group UDGs share similar properties, independent of distance from the group centre. Their dark-matter haloes have ordinary spin parameters and centrally dominant dark-matter cores. Their stellar components tend to have a prolate shape with a Sérsic index n ∼ 1 but no significant rotation. Ram pressure removes the gas from the group UDGs when they are at pericentre, quenching star formation in them and making them redder. This generates a colour/star-formation-rate gradient with distance from the centre of the dense environment, as observed in clusters. We find that ∼20 per cent of the field UDGs that fall into a massive halo survive as satellite UDGs. In addition, normal field dwarfs on highly eccentric orbits can become UDGs near pericentre due to tidal puffing up, contributing about half of the group-UDG population. We interpret our findings using simple toy models, showing that gas stripping is mostly due to ram pressure rather than tides. We estimate that the energy deposited by tides in the bound component of a satellite over one orbit can cause significant puffing up provided that the orbit is sufficiently eccentric. We caution that while the simulations produce UDGs that match the observations, they under-produce the more compact dwarfs in the same mass range, possibly because of the high threshold for star formation or the strong feedback.

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Mass Stripping in Dwarf Spheroidal Galaxies and ω Cen

Symposium - International Astronomical Union ◽

10.1017/s0074180900198006 ◽

2004 ◽

Vol 217 ◽

pp. 384-385

Author(s):

Takuji Tsujimoto ◽

Toshikazu Shigeyama

Keyword(s):

Dark Matter ◽

Star Formation ◽

Velocity Dispersion ◽

Gradual Increase ◽

Galactic Disk ◽

Abundance Pattern ◽

Dwarf Spheroidal Galaxies ◽

Bulk Motion ◽

Ram Pressure ◽

The Common

The stellar abundance pattern of neutron-capture elements such as Ba is used as a powerful tool to infer how star formation proceeded in dwarf spheroidal (dSph) galaxies. It is found that the abundance correlation of Ba with Fe in stars belonging to dSph galaxies have a feature similar to the Ba-Fe correlation in Galactic metal-poor stars. The common feature of these two correlations implies that dSph stars formed from gas with a velocity dispersion of ~26 km s−1. This velocity dispersion together with the stellar luminosities strongly suggests that dark matter dominated dSph galaxies. The tidal force of the Milky Way links this velocity dispersion with the currently observed value ≤ 10 km s−1 by stripping the dark matter in dSph galaxies. We also investigate the ram pressure exerted on the gas in ω Cen. It is found that the ram pressure is not strong enough to strip the gas but is expected to induce a bulk motion of the gas during the star formation epoch which is compatible with the recent observed finding and then the remaining gas after the star formation is likely to be stripped due to the gradual increase in the gas density in the forming Galactic disk.

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