SUBSTRUCTURE FORMATION IN TIDAL STREAMS OF GALACTIC MINOR MERGERS

In this work, we explore the idea that substructures like stellar clusters could be formed from the tidal stream produced in galactic minor mergers. We use N -body and SPH simulations of satellite galaxies interacting with a larger galaxy. We study the distribution of mass in streams to identify overdensity regions in which a substructure could be formed. We find that without gas, no substructure forms as none of the overdensities shows a definite morphology nor dynamical stability. Including gas we find that several clumps appear and prove to be real long standing physical structures (t ≥ 1 Gyr). We analyze the orbits, ages and masses of these structures, finding their correspondence with the halo subsystems. We conclude that it is possible to form cluster-like structures from the material in tidal streams and find evidence in favour of the presence of dark matter in these systems.

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Quantifying tidal stream disruption in a simulated Milky Way

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stx1268 ◽

2017 ◽

Vol 470 (1) ◽

pp. 522-538 ◽

Cited By ~ 10

Author(s):

Emily Sandford ◽

Andreas H. W. Küpper ◽

Kathryn V. Johnston ◽

Jürg Diemand

Keyword(s):

Dark Matter ◽

Milky Way ◽

Galactic Halo ◽

Mass Range ◽

Galactic Centre ◽

High Dimensions ◽

Density Profiles ◽

Upper Limits ◽

Tidal Stream ◽

Tidal Streams

Abstract Simulations of tidal streams show that close encounters with dark matter subhaloes induce density gaps and distortions in on-sky path along the streams. Accordingly, observing disrupted streams in the Galactic halo would substantiate the hypothesis that dark matter substructure exists there, while in contrast, observing collimated streams with smoothly varying density profiles would place strong upper limits on the number density and mass spectrum of subhaloes. Here, we examine several measures of stellar stream ‘disruption' and their power to distinguish between halo potentials with and without substructure and with different global shapes. We create and evolve a population of 1280 streams on a range of orbits in the Via Lactea II simulation of a Milky Way-like halo, replete with a full mass range of Λcold dark matter subhaloes, and compare it to two control stream populations evolved in smooth spherical and smooth triaxial potentials, respectively. We find that the number of gaps observed in a stellar stream is a poor indicator of the halo potential, but that (i) the thinness of the stream on-sky, (ii) the symmetry of the leading and trailing tails and (iii) the deviation of the tails from a low-order polynomial path on-sky (‘path regularity') distinguish between the three potentials more effectively. We furthermore find that globular cluster streams on low-eccentricity orbits far from the galactic centre (apocentric radius ∼30–80 kpc) are most powerful in distinguishing between the three potentials. If they exist, such streams will shortly be discoverable and mapped in high dimensions with near-future photometric and spectroscopic surveys.

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Simulating the galactic system in interaction AM 2229-735 and the formation of its polar structure

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stz2943 ◽

2019 ◽

Author(s):

Luis F Quiroga ◽

J C Muñoz-Cuartas ◽

I Rodrigues ◽

Noam I Libeskind

Keyword(s):

Dark Matter ◽

Initial Conditions ◽

Polar Structure ◽

Polar Ring ◽

Galactic System ◽

Galaxy Disk ◽

Ring Galaxies ◽

Tidal Stream ◽

Minor Mergers ◽

A Minor

Abstract We study the formation of polar ring galaxies via minor mergers. We used N-body+hydrodynamics simulations to reproduce the dynamics of the observed system AM 2229-735 that is a minor merger whose interaction signals are those of a progenitor for a polar ring galaxy. We used the observational information of the system to get initial conditions for the orbit and numerical realisations of the galaxies to run the simulations. Our simulations reproduce the global characteristics of interaction observed in the system such as arms and a material bridge connecting the galaxies. As a merger remnant, we found a quasi-stable and self gravitating planar tidal stream with dark matter, stars and gas orbiting in a plane approximately perpendicular to the main galaxy disk leading in the future to a polar ring galaxy. We studied the dynamical conditions of the polar structure and found evidence suggesting that this kind of merger remnant can settle down in a disk-like structure with isothermal support, providing inspiring evidence about the process of formation of galactic disks and providing a potentially independent scenario to study the presence of dark matter in this kind of galaxies.

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On N-body simulations of globular cluster streams

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stab886 ◽

2021 ◽

Vol 504 (1) ◽

pp. 648-653

Author(s):

Nilanjan Banik ◽

Jo Bovy

Keyword(s):

Dark Matter ◽

Cold Dark Matter ◽

Analytical Models ◽

Numerical Density ◽

Stellar Streams ◽

Small Scales ◽

Order Of Magnitude ◽

Low Mass ◽

Stream Density ◽

Tidal Streams

ABSTRACT Stellar tidal streams are sensitive tracers of the properties of the gravitational potential in which they orbit and detailed observations of their density structure can be used to place stringent constraints on fluctuations in the potential caused by, e.g. the expected populations of dark matter subhaloes in the standard cold dark matter (CDM) paradigm. Simulations of the evolution of stellar streams in live N-body haloes without low-mass dark matter subhaloes, however, indicate that streams exhibit significant perturbations on small scales even in the absence of substructure. Here, we demonstrate, using high-resolution N-body simulations combined with sophisticated semi-analytical and simple analytical models, that the mass resolutions of 104–$10^5\, \rm {M}_{\odot }$ commonly used to perform such simulations cause spurious stream density variations with a similar magnitude on large scales as those expected from a CDM-like subhalo population and an order of magnitude larger on small, yet observable, scales. We estimate that mass resolutions of ${\approx}100\, \rm {M}_{\odot }$ (${\approx}1\, \rm {M}_{\odot }$) are necessary for spurious, numerical density variations to be well below the CDM subhalo expectation on large (small) scales. That streams are sensitive to a simulation’s particle mass down to such small masses indicates that streams are sensitive to dark matter clustering down to these low masses if a significant fraction of the dark matter is clustered or concentrated in this way, for example, in MACHO models with masses of 10–$100\, \rm {M}_{\odot }$.

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A comparative study of satellite galaxies in Milky Way-like galaxies from HSC, DECaLS, and SDSS

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa3495 ◽

2020 ◽

Vol 500 (3) ◽

pp. 3776-3801

Author(s):

Wenting Wang ◽

Masahiro Takada ◽

Xiangchong Li ◽

Scott G Carlsten ◽

Ting-Wen Lan ◽

...

Keyword(s):

Dark Matter ◽

Milky Way ◽

Statistical Study ◽

Satellite System ◽

Large Scatter ◽

Local Universe ◽

Good Representative ◽

Luminosity Functions ◽

Satellite Galaxies ◽

Good Agreement

ABSTRACT We conduct a comprehensive and statistical study of the luminosity functions (LFs) for satellite galaxies, by counting photometric galaxies from HSC, DECaLS, and SDSS around isolated central galaxies (ICGs) and paired galaxies from the SDSS/DR7 spectroscopic sample. Results of different surveys show very good agreement. The satellite LFs can be measured down to MV ∼ −10, and for central primary galaxies as small as 8.5 < log10M*/M⊙ < 9.2 and 9.2 < log10M*/M⊙ < 9.9, which implies there are on average 3–8 satellites with MV < −10 around LMC-mass ICGs. The bright end cutoff of satellite LFs and the satellite abundance are both sensitive to the magnitude gap between the primary and its companions, indicating galaxy systems with larger magnitude gaps are on average hosted by less massive dark matter haloes. By selecting primaries with stellar mass similar to our Milky Way (MW), we discovered that (i) the averaged satellite LFs of ICGs with different magnitude gaps to their companions and of galaxy pairs with different colour or colour combinations all show steeper slopes than the MW satellite LF; (ii) there are on average more satellites with −15 < MV < −10 than those in our MW; (iii) there are on average 1.5 to 2.5 satellites with MV < −16 around ICGs, consistent with our MW; (iv) even after accounting for the large scatter predicted by numerical simulations, the MW satellite LF is uncommon at MV > −12. Hence, the MW and its satellite system are statistically atypical of our sample of MW-mass systems. In consequence, our MW is not a good representative of other MW-mass galaxies. Strong cosmological implications based on only MW satellites await additional discoveries of fainter satellites in extra-galactic systems. Interestingly, the MW satellite LF is typical among other MW-mass systems within 40 Mpc in the local Universe, perhaps implying the Local Volume is an underdense region.

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The size and mass evolution of the massive galaxies over cosmic time

Proceedings of the International Astronomical Union ◽

10.1017/s1743921313004201 ◽

2012 ◽

Vol 8 (S295) ◽

pp. 27-36

Author(s):

Ignacio Trujillo

Keyword(s):

Structural Evolution ◽

Cosmic Time ◽

Stellar Populations ◽

Massive Galaxies ◽

Active Line ◽

Satellite Galaxies ◽

Compact Galaxies ◽

Minor Mergers ◽

Stellar Properties

AbstractOnce understood as the paradigm of passively evolving objects, the discovery that massive galaxies experienced an enormous structural evolution in the last ten billion years has opened an active line of research. The most significant pending question in this field is the following: which mechanism has made galaxies to grow largely in size without altering their stellar populations properties dramatically? The most viable explanation is that massive galaxies have undergone a significant number of minor mergers which have deposited most of their material in the outer regions of the massive galaxies. This scenario, although appealing, is still far from be observationally proved since the number of satellite galaxies surrounding the massive objects appears insufficient at all redshifts. The presence also of a population of nearby massive compact galaxies with mixture stellar properties is another piece of the puzzle that still does not nicely fit within a comprehensive scheme. I will review these and other intriguing properties of the massive galaxies in this contribution.

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Dark matter–radiation interactions: the structure of Milky Way satellite galaxies

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stw1078 ◽

2016 ◽

Vol 461 (3) ◽

pp. 2282-2287 ◽

Cited By ~ 31

Author(s):

J. A. Schewtschenko ◽

C. M. Baugh ◽

R. J. Wilkinson ◽

C. Bœhm ◽

S. Pascoli ◽

...

Keyword(s):

Dark Matter ◽

Milky Way ◽

Satellite Galaxies

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The Milky Way’s halo and subhaloes in self-interacting dark matter

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stz2345 ◽

2019 ◽

Vol 490 (2) ◽

pp. 2117-2123 ◽

Cited By ~ 10

Author(s):

Victor H Robles ◽

Tyler Kelley ◽

James S Bullock ◽

Manoj Kaplinghat

Keyword(s):

Dark Matter ◽

Cold Dark Matter ◽

Elastic Cross Section ◽

Too Big To Fail ◽

Density Profiles ◽

Potential Core ◽

Cold Dark Matter Model ◽

Matter Model ◽

Satellite Galaxies ◽

Dark Matter Model

ABSTRACT We perform high-resolution simulations of an MW-like galaxy in a self-interacting cold dark matter model with elastic cross-section over mass of $1~\rm cm^2\, g^{-1}$ (SIDM) and compare to a model without self-interactions (CDM). We run our simulations with and without a time-dependent embedded potential to capture effects of the baryonic disc and bulge contributions. The CDM and SIDM simulations with the embedded baryonic potential exhibit remarkably similar host halo profiles, subhalo abundances, and radial distributions within the virial radius. The SIDM host halo is denser in the centre than the CDM host and has no discernible core, in sharp contrast to the case without the baryonic potential (core size ${\sim}7 \, \rm kpc$). The most massive subhaloes (with $V_{\mathrm{peak}}\gt 20 \, \rm km\, s^{-1}$) in our SIDM simulations, expected to host the classical satellite galaxies, have density profiles that are less dense than their CDM analogues at radii less than 500 pc but the deviation diminishes for less massive subhaloes. With the baryonic potential included in the CDM and SIDM simulations, the most massive subhaloes do not display the too-big-to-fail problem. However, the least dense among the massive subhaloes in both these simulations tend to have the smallest pericenter values, a trend that is not apparent among the bright MW satellite galaxies.

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Satellite galaxies in the Illustris-1 simulation: anisotropic locations around relatively isolated hosts

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stz2102 ◽

2019 ◽

Vol 489 (1) ◽

pp. 459-469 ◽

Cited By ~ 4

Author(s):

Tereasa G Brainerd ◽

Masaya Yamamoto

Keyword(s):

Dark Matter ◽

Mass Density ◽

Stellar Mass ◽

Stellar Surface ◽

Surface Mass ◽

Degree Of Anisotropy ◽

Surface Mass Density ◽

The Mean ◽

Satellite Galaxies ◽

Stellar Masses

ABSTRACT We investigate the locations of satellite galaxies in the z = 0 redshift slice of the hydrodynamical Illustris-1 simulation. As expected from previous work, the satellites are distributed anisotropically in the plane of the sky, with a preference for being located near the major axes of their hosts. Due to misalignment of mass and light within the hosts, the degree of anisotropy is considerably less when satellite locations are measured with respect to the hosts’ stellar surface mass density than when they are measured with respect to the hosts’ dark matter surface mass density. When measured with respect to the hosts’ dark matter surface mass density, the mean satellite location depends strongly on host stellar mass and luminosity, with the satellites of the faintest, least massive hosts showing the greatest anisotropy. When measured with respect to the hosts’ stellar surface mass density, the mean satellite location is essentially independent of host stellar mass and luminosity. In addition, the satellite locations are largely insensitive to the amount of stellar mass used to define the hosts’ stellar surface mass density, as long as at least 50–70 per cent of the hosts’ total stellar mass is used. The satellite locations are dependent upon the stellar masses of the satellites, with the most massive satellites having the most anisotropic distributions.

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