scholarly journals Heating of Milky Way disc stars by dark matter fluctuations in cold dark matter and fuzzy dark matter paradigms

2019 ◽  
Vol 485 (2) ◽  
pp. 2861-2876 ◽  
Author(s):  
Benjamin V Church ◽  
Philip Mocz ◽  
Jeremiah P Ostriker
Keyword(s):  
Dark Matter ◽  
Galaxy Formation ◽  
Quantum Interference ◽  
Cold Dark Matter ◽  
Milky Way ◽  
Velocity Dispersion ◽  
Formation Rate ◽  
Density Fluctuations ◽  
Particle Mass ◽  
Small Scale

ABSTRACT Although highly successful on cosmological scales, cold dark matter (CDM) models predict unobserved overdense ‘cusps’ in dwarf galaxies and overestimate their formation rate. We consider an ultralight axion-like scalar boson which promises to reduce these observational discrepancies at galactic scales. The model, known as fuzzy dark matter (FDM), avoids cusps, suppresses small-scale power, and delays galaxy formation via macroscopic quantum pressure. We compare the substructure and density fluctuations of galactic dark matter haloes comprised of ultralight axions to conventional CDM results. Besides self-gravitating subhaloes, FDM includes non-virialized overdense wavelets formed by quantum interference patterns, which are an efficient source of heating to galactic discs. We find that, in the solar neighbourhood, wavelet heating is sufficient to give the oldest disc stars a velocity dispersion of ${\sim } {30}{\, \mathrm{km\, s}^{-1}}$ within a Hubble time if energy is not lost from the disc, the velocity dispersion increasing with stellar age as σD ∝ t0.4 in agreement with observations. Furthermore, we calculate the radius-dependent velocity dispersion and corresponding scaleheight caused by the heating of this dynamical substructure in both CDM and FDM with the determination that these effects will produce a flaring that terminates the Milky Way disc at $15\!-\!20{\, \mathrm{kpc}}$. Although the source of thickened discs is not known, the heating due to perturbations caused by dark substructure cannot exceed the total disc velocity dispersion. Therefore, this work provides a lower bound on the FDM particle mass of ma > 0.6 × 10−22 eV. Furthermore, FDM wavelets with this particle mass should be considered a viable mechanism for producing the observed disc thickening with time.

scholarly journals Probing non-spherical dark halos in the Galactic dwarf satellites

2013 ◽  
Vol 9 (S298) ◽  
pp. 411-411
Author(s):  
Kohei Hayashi ◽  
Masashi Chiba
Keyword(s):  
Dark Matter ◽  
Cold Dark Matter ◽  
Milky Way ◽  
Velocity Dispersion ◽  
Line Of Sight ◽  
Spherical Structure ◽  
Spherical Models ◽  
Galactic Satellites ◽  
Best Fitting

AbstractWe construct axisymmetric mass models for dwarf spheroidal (dSph) galaxies in the Milky Way to obtain realistic limits on the non-spherical structure of their dark halos. This is motivated by the fact that the observed luminous parts of the dSphs are actually non-spherical and cold dark matter models predict non-spherical virialized dark halos on sub-galactic scales. Applying these models to line-of-sight velocity dispersion profiles along three position angles in six Galactic satellites, we find that the best fitting cases for most of the dSphs yield not spherical but oblate and flattened dark halos. We also find that the mass of the dSphs enclosed within inner 300 pc varies depending on their total luminosities, contrary to the conclusion of previous spherical models. This suggests the importance of considering non-spherical shapes of dark halos in dSph mass models.

Galaxy clustering and the dark-matter problem

1986 ◽  
Vol 320 (1556) ◽  
pp. 517-541 ◽  
Keyword(s):  
Dark Matter ◽  
Cold Dark Matter ◽  
Density Fluctuations ◽  
Small Scale ◽  
Galactic Halos ◽  
Galaxy Clustering ◽  
Simple Assumption ◽  
Scale Free ◽  
The Galaxy ◽  
Flat Rotation Curves

Recent observational and theoretical results on galaxy clustering are reviewed. A major difficulty in relating observations to theory is that the former refer to luminous material whereas the latter is most directly concerned with the gravitationally dominant but invisible dark matter. The simple assumption that the distribution of galaxies generally follows that of the mass appears to conflict with evidence suggesting that galaxies of different kinds are clustered in different ways. If galaxies are indeed biased tracers of the mass, then dynamical estimates of the mean cosmic density, which give Ω « 0.2 may underestimate the global value of Ω. There are now several specific models for the behaviour of density fluctuations from very early times to the present epoch. The late phases of this evolution need to be followed by N -body techniques; simulations of scale-free universes and of universes dominated by various types of elementary particles are discussed. In the former case, the models evolve in a self-similar way; the resulting correlations have a steeper slope than that oberved for the galaxy distribution unless the primordial power spectral index n « 2. Universes dominated by light neutrinos acquire a large coherence length at early times. As a result, an early filamentary phase develops into a present day distribution that is more strongly clustered than observed galaxies and is dominated by a few clumps with masses larger than those of any known object. If the dark matter consists of ‘cold’ particles such as photinos or axions, then structure builds up from subgalactic scales in a roughly hierarchical way. The observed pattern of galaxy clustering can be reproduced if either Ω « 0.2 and the galaxies are distributed as the mass, or if Ω — 1, H 0 = 50 km s -1 Mpc -1 and the galaxies form only at high peaks of the smoothed linear density field. The open model, however, is marginally ruled out by the observed small-scale isotropy of the microwave background, whereas the flat one is consistent with such observations. With no further free parameters a flat cold dark-matter universe produces the correct abundance of rich galaxy clusters and of galactic halos; the latter have flat rotation curves with amplitudes spanning the observed range. Preliminary calculations indicate that the properties of voids may be consistent with the data, but the correlations of rich clusters appear to be somewhat weaker than those reported for Abell clusters.

scholarly journals A Model for the Sequence of Elliptical Galaxies

1987 ◽  
Vol 117 ◽  
pp. 367-367
Author(s):  
Rosemary F. G. Wyse ◽  
Bernard J. T. Jones
Keyword(s):  
Dark Matter ◽  
Power Spectrum ◽  
Galaxy Formation ◽  
Cold Dark Matter ◽  
Initial Conditions ◽  
Elliptical Galaxy ◽  
Elliptical Galaxies ◽  
Density Fluctuations ◽  
Analytic Approximation ◽  
Non Linear

We present a simple model for the formation of elliptical galaxies, based on a binary clustering hierarchy of dark matter, the chemical enrichment of the gas at each level being controlled by supernovae. The initial conditions for the non-linear phases of galaxy formation are set by the post-recombination power spectrum of density fluctuations. We investigate two models for this power spectrum - the first is a straightforward power law, |δk|2 ∝ kn, and the second is Peeble's analytic approximation to the emergent spectrum in a universe dominated by cold dark matter. The normalisation is chosen such that on some scale, say M ∼ 1012M⊙, the objects that condense out have properties - radius and velocity dispersion - resembling ‘typical’ galaxies. There is some ambiguity in this due to the poorly determined mass-to-light ratio of a typical elliptical galaxy — we look at two normalisations, σ1D ∼ 350kms−1 and σ1D ∼ 140kms−1. The choice determines which of Compton cooling or hydrogen cooling is more important during the galaxy formation period. The non-linear behaviour of the perturbations is treated by the homogeneous sphere approximation.

scholarly journals Small-scale Substructure in Dark Matter Haloes: Where Does Galaxy Formation Come to an End?

2004 ◽  
Vol 220 ◽  
pp. 91-98 ◽  
Author(s):  
J. E. Taylor ◽  
J. Silk ◽  
A. Babul
Keyword(s):  
Dark Matter ◽  
Power Spectrum ◽  
Structure Formation ◽  
Galaxy Formation ◽  
Cold Dark Matter ◽  
High Redshift ◽  
Small Scale ◽  
Analytic Model ◽  
Model Predictions ◽  
Low Mass

Models of structure formation based on cold dark matter predict that most of the small dark matter haloes that first formed at high redshift would have merged into larger systems by the present epoch. Substructure in present-day haloes preserves the remains of these ancient systems, providing the only direct information we may ever have about the low-mass end of the power spectrum. We describe some recent attempts to model halo substructure down to very small masses, using a semi-analytic model of halo formation. We make a preliminary comparison between the model predictions, observations of substructure in lensed systems, and the properties of local satellite galaxies.

scholarly journals A dark matter profile to model diverse feedback-induced core sizes of ΛCDM haloes

2020 ◽  
Vol 497 (2) ◽  
pp. 2393-2417 ◽  
Author(s):  
Alexandres Lazar ◽  
James S Bullock ◽  
Michael Boylan-Kolchin ◽  
T K Chan ◽  
Philip F Hopkins ◽  
...  
Keyword(s):  
Dark Matter ◽  
Galaxy Formation ◽  
Cold Dark Matter ◽  
Milky Way ◽  
Dark Matter Halo ◽  
Constant Density ◽  
Core Formation ◽  
Density Profiles ◽  
The Galaxy ◽  
Two Parameter

ABSTRACT We analyse the cold dark matter density profiles of 54 galaxy haloes simulated with Feedback In Realistic Environments (FIRE)-2 galaxy formation physics, each resolved within $0.5{{\ \rm per\ cent}}$ of the halo virial radius. These haloes contain galaxies with masses that range from ultrafaint dwarfs ($M_\star \simeq 10^{4.5}\, \mathrm{M}_{\odot }$) to the largest spirals ($M_\star \simeq 10^{11}\, \mathrm{M}_{\odot }$) and have density profiles that are both cored and cuspy. We characterize our results using a new, analytic density profile that extends the standard two-parameter Einasto form to allow for a pronounced constant density core in the resolved innermost radius. With one additional core-radius parameter, rc, this three-parameter core-Einasto profile is able to characterize our feedback-impacted dark matter haloes more accurately than other three-parameter profiles proposed in the literature. To enable comparisons with observations, we provide fitting functions for rc and other profile parameters as a function of both M⋆ and M⋆/Mhalo. In agreement with past studies, we find that dark matter core formation is most efficient at the characteristic stellar-to-halo mass ratio M⋆/Mhalo ≃ 5 × 10−3, or $M_{\star } \sim 10^9 \, \mathrm{M}_{\odot }$, with cores that are roughly the size of the galaxy half-light radius, rc ≃ 1−5 kpc. Furthermore, we find no evidence for core formation at radii $\gtrsim 100\ \rm pc$ in galaxies with M⋆/Mhalo < 5 × 10−4 or $M_\star \lesssim 10^6 \, \mathrm{M}_{\odot }$. For Milky Way-size galaxies, baryonic contraction often makes haloes significantly more concentrated and dense at the stellar half-light radius than DMO runs. However, even at the Milky Way scale, FIRE-2 galaxy formation still produces small dark matter cores of ≃ 0.5−2 kpc in size. Recent evidence for a ∼2 kpc core in the Milky Way’s dark matter halo is consistent with this expectation.

scholarly journals To Observe, or Not to Observe, Quantum-Coherent Dark Matter in the Milky Way, That is a Question

2021 ◽  
Vol 8 ◽  
Author(s):  
Tanja Rindler-Daller
Keyword(s):  
Dark Matter ◽  
Scalar Field ◽  
Structure Formation ◽  
Cold Dark Matter ◽  
Milky Way ◽  
Small Scale ◽  
Quantum Mechanical ◽  
Bose Einstein ◽  
The Impact ◽  
Observational Signature

In recent years, Bose-Einstein-condensed dark matter (BEC-DM) has become a popular alternative to standard, collisionless cold dark matter (CDM). This BEC-DM -also called scalar field dark matter (SFDM)- can suppress structure formation and thereby resolve the small-scale crisis of CDM for a range of boson masses. However, these same boson masses also entail implications for BEC-DM substructure within galaxies, especially within our own Milky Way. Observational signature effects of BEC-DM substructure depend upon its unique quantum-mechanical features and have the potential to reveal its presence. Ongoing efforts to determine the dark matter substructure in our Milky Way will continue and expand considerably over the next years. In this contribution, we will discuss some of the existing constraints and potentially new ones with respect to the impact of BEC-DM onto baryonic tracers. Studying dark matter substructure in our Milky Way will soon resolve the question, whether dark matter behaves classical or quantum on scales of ≲ 1 kpc.

scholarly journals Galaxies on Sub-Galactic Scales

2012 ◽  
Vol 29 (4) ◽  
pp. 383-394 ◽  
Author(s):  
Helmut Jerjen
Keyword(s):  
Dark Matter ◽  
Galaxy Formation ◽  
Cold Dark Matter ◽  
Milky Way ◽  
Dwarf Galaxy ◽  
Near Field ◽  
Sloan Digital Sky Survey ◽  
Matter Theory ◽  
Satellite Galaxies ◽  
Star Formation Histories

AbstractThe Sloan Digital Sky Survey has been immensely successful in detecting new Milky Way satellite galaxies over the past seven years. It was instrumental in finding examples of the least luminous galaxies we know in the Universe, uncovering apparent inconsistencies between cold dark matter theory and dwarf galaxy properties, providing first evidence for a possible lower mass limit for dark matter halos in visible galaxies, and reopening the discussion about the building block scenario for the Milky Way halo. Nonetheless, these results are still drawn only from a relatively small number of galaxies distributed over an area covering about 29% of the sky, which leaves us currently with more questions than answers. The study of these extreme stellar systems is a multi-parameter problem: ages, metallicities, star formation histories, dark matter contents, population fractions and spatial distributions must be determined. Progress in the field is discussed and attention drawn to some of the limitations that currently hamper our ability to fully understand the phenomenon of the ‘ultra-faint dwarf galaxy’. In this context, the Stromlo Milky Way Satellite Survey represents a new initiative to systematically search and scrutinize optically elusive Milky Way satellite galaxies in the Southern hemisphere. In doing so, the program aims at investigating some of the challenging questions in stellar evolution, galaxy formation and near-field cosmology.

scholarly journals Galaxy formation with BECDM – II. Cosmic filaments and first galaxies

2020 ◽  
Vol 494 (2) ◽  
pp. 2027-2044 ◽  
Author(s):  
Philip Mocz ◽  
Anastasia Fialkov ◽  
Mark Vogelsberger ◽  
Fernando Becerra ◽  
Xuejian Shen ◽  
...  
Keyword(s):  
Dark Matter ◽  
Star Formation ◽  
Power Spectrum ◽  
Galaxy Formation ◽  
Cold Dark Matter ◽  
Einstein Condensate ◽  
Boson Mass ◽  
Small Scale ◽  
Bose Einstein Condensate ◽  
First Galaxies

ABSTRACT Bose–Einstein condensate dark matter (BECDM, also known as fuzzy dark matter) is motivated by fundamental physics and has recently received significant attention as a serious alternative to the established cold dark matter (CDM) model. We perform cosmological simulations of BECDM gravitationally coupled to baryons and investigate structure formation at high redshifts (z ≳ 5) for a boson mass m = 2.5 × 10−22 eV, exploring the dynamical effects of its wavelike nature on the cosmic web and the formation of first galaxies. Our BECDM simulations are directly compared to CDM as well as to simulations where the dynamical quantum potential is ignored and only the initial suppression of the power spectrum is considered – a warm dark matter-like (‘WDM’) model often used as a proxy for BECDM. Our simulations confirm that ‘WDM’ is a good approximation to BECDM on large cosmological scales even in the presence of the baryonic feedback. Similarities also exist on small scales, with primordial star formation happening both in isolated haloes and continuously along cosmic filaments; the latter effect is not present in CDM. Global star formation and metal enrichment in these first galaxies are delayed in BECDM/‘WDM’ compared to the CDM case: in BECDM/‘WDM’ first stars form at z ∼ 13/13.5, while in CDM star formation starts at z ∼ 35. The signature of BECDM interference, not present in ‘WDM’, is seen in the evolved dark matter power spectrum: although the small-scale structure is initially suppressed, power on kpc scales is added at lower redshifts. Our simulations lay the groundwork for realistic simulations of galaxy formation in BECDM.

scholarly journals Clues to the nature of dark matter from first galaxies

2019 ◽  
Vol 489 (1) ◽  
pp. 487-496 ◽  
Author(s):  
Boyan K Stoychev ◽  
Keri L Dixon ◽  
Andrea V Macciò ◽  
Marvin Blank ◽  
Aaron A Dutton
Keyword(s):  
Dark Matter ◽  
Star Formation ◽  
Galaxy Formation ◽  
Cold Dark Matter ◽  
High Redshift ◽  
Formation Rate ◽  
Neutral Hydrogen ◽  
Mass Function ◽  
Stellar Mass ◽  
The Impact

ABSTRACT We use 38 high-resolution simulations of galaxy formation between redshift 10 and 5 to study the impact of a 3 keV warm dark matter (WDM) candidate on the high-redshift Universe. We focus our attention on the stellar mass function and the global star formation rate and consider the consequences for reionization, namely the neutral hydrogen fraction evolution and the electron scattering optical depth. We find that three different effects contribute to differentiate warm and cold dark matter (CDM) predictions: WDM suppresses the number of haloes with mass less than few 109 M⊙; at a fixed halo mass, WDM produces fewer stars than CDM, and finally at halo masses below 109 M⊙, WDM has a larger fraction of dark haloes than CDM post-reionization. These three effects combine to produce a lower stellar mass function in WDM for galaxies with stellar masses at and below 107 M⊙. For z > 7, the global star formation density is lower by a factor of two in the WDM scenario, and for a fixed escape fraction, the fraction of neutral hydrogen is higher by 0.3 at z ∼ 6. This latter quantity can be partially reconciled with CDM and observations only by increasing the escape fraction from 23 per cent to 34 per cent. Overall, our study shows that galaxy formation simulations at high redshift are a key tool to differentiate between dark matter candidates given a model for baryonic physics.

scholarly journals Dwarf Galaxies, Cold Dark Matter, and Biased Galaxy Formation

1987 ◽  
Vol 117 ◽  
pp. 362-362
Author(s):  
Avishai Dekel ◽  
Joseph Silk
Keyword(s):  
Dark Matter ◽  
Galaxy Formation ◽  
Surface Brightness ◽  
Cold Dark Matter ◽  
Velocity Dispersion ◽  
Local Group ◽  
Dwarf Galaxies ◽  
Virgo Cluster ◽  
Slow Decrease ◽  
Gas Loss

The formation of dwarf, diffuse, metal-poor galaxies, as a result of supernova driven winds, is reexamained in view of the accumulating data on dwarfs in the local group and in the Virgo cluster. The observed drop in both surface-brightness and metallicity with decreasing luminosity is not easily understood if the gaseous protogalaxies are self-gravitating (because they swell after gas-loss), but they are produced naturally inside dominant halos, with a mass-radius relation that indicates ‘cold’ dark matter. The theory predicts for the faint dwarfs an M/L that increases with decreasing luminosity up to 10–100, and a corresponding slow decrease in velocity dispersion down to 5–10 km/s.

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