scholarly journals Constrained Simulations of the Local Universe

2007 ◽  
Vol 3 (S244) ◽  
pp. 395-396
Author(s):  
G. Yepes ◽  
L. Martinez-Vaquero ◽  
Y. Hoffman ◽  
S. Gottlöber ◽  
A. Klypin
Keyword(s):  
Dark Matter ◽  
Galaxy Formation ◽  
Local Group ◽  
Initial Density ◽  
High Accuracy ◽  
Density Field ◽  
Local Universe ◽  
Local Mass ◽  
Local Supercluster ◽  
The Galaxy

AbstractWe have studied the formation of the Local Universe using constrained cosmological simulations. To this end we use the observed local mass and velocity distributions to generate the initial density field. A variety of N-body simulations with different box sizes and resolutions have been done so far. The largest structures, such as Coma, Virgo and the Local Supercluster are reproduced with high accuracy. We have also been able to obtain a representation of the Local Group with unprecedented accuracy and resolution. From these simulations we are studying in detail the dynamics of the dark matter in our neighborhood. The next step will be to include baryons and study in detail the galaxy formation in our local universe.

scholarly journals Local group star formation in warm and self-interacting dark matter cosmologies

2020 ◽  
Vol 498 (1) ◽  
pp. 702-717 ◽  
Author(s):  
Mark R Lovell ◽  
Wojciech Hellwing ◽  
Aaron Ludlow ◽  
Jesús Zavala ◽  
Andrew Robertson ◽  
...  
Keyword(s):  
Dark Matter ◽  
Star Formation ◽  
Galaxy Formation ◽  
Cold Dark Matter ◽  
Local Group ◽  
Initial Density ◽  
Dark Matter Mass ◽  
Stellar Ages ◽  
Hydrodynamical Simulations ◽  
Star Formation Histories

ABSTRACT The nature of the dark matter can affect the collapse time of dark matter haloes, and can therefore be imprinted in observables such as the stellar population ages and star formation histories of dwarf galaxies. In this paper, we use high-resolution hydrodynamical simulations of Local Group-analogue (LG) volumes in cold dark matter (CDM), sterile neutrino warm dark matter (WDM) and self-interacting dark matter (SIDM) models with the eagle galaxy formation code to study how galaxy formation times change with dark matter model. We are able to identify the same haloes in different simulations, since they share the same initial density field phases. We find that the stellar mass of galaxies depends systematically on resolution, and can differ by as much as a factor of 2 in haloes of a given dark matter mass. The evolution of the stellar populations in SIDM is largely identical to that of CDM, but in WDM early star formation is instead suppressed. The time at which LG haloes can begin to form stars through atomic cooling is delayed by ∼200 Myr in WDM models compared to CDM. It will be necessary to measure stellar ages of old populations to a precision of better than 100 Myr, and to address degeneracies with the redshift of reionization – and potentially other baryonic processes – in order to use these observables to distinguish between dark matter models.

scholarly journals Hi and Galaxy Formation in Loose Groups

2004 ◽  
Vol 21 (4) ◽  
pp. 390-392
Author(s):  
Daniel J. Pisano
Keyword(s):  
Dark Matter ◽  
Galaxy Formation ◽  
Local Group ◽  
Dark Matter Halos ◽  
Early Results ◽  
Large Numbers ◽  
The Galaxy ◽  
Order Of Magnitude ◽  
Low Mass ◽  
High Velocity Clouds

AbstractModels of hierarchical galaxy formation predict that large numbers of low-mass, dark matter halos remain around galaxies today. These models predict an order of magnitude more halos than observed stellar satellites in the Local Group. One possible solution to this discrepancy is that the high-velocity clouds (HVCs) around the Milky Way may be associated with the excess dark matter halos and be the gaseous remnants of the galaxy formation process. If this is the case, then analogues to the HVCs should be visible in other groups. In this paper, I review the observations of Hi clouds lacking stars around other galaxies and in groups, present early results from our Hi survey of loose groups analogous to the Local Group, and discuss implications for the nature of HVCs and galaxy formation.

scholarly journals The APOSTLE simulations: Rotation curves derived from synthetic 21-cm observations

2017 ◽  
Vol 13 (S334) ◽  
pp. 213-218
Author(s):  
Kyle A. Oman
Keyword(s):  
Dark Matter ◽  
Galaxy Formation ◽  
Cold Dark Matter ◽  
Local Group ◽  
Synthetic Data ◽  
Formation Model ◽  
Rotation Curves ◽  
Hydrodynamical Simulation ◽  
The Galaxy ◽  
Spectrally Resolved

AbstractThe apostle cosmological hydrodynamical simulation suite is a collection of twelve regions ~5 Mpc in diameter, selected to resemble the Local Group of galaxies in terms of kinematics and environment, and re-simulated at high resolution (minimum gas particle mass of 104 M⊙) using the galaxy formation model and calibration developed for the eagle project. I select a sample of dwarf galaxies (60 < Vmax/km s−1 < 120) from these simulations and construct synthetic spatially- and spectrally-resolved observations of their 21-cm emission. Using the 3Dbarolo tilted-ring modelling tool, I extract rotation curves from the synthetic data cubes. In many cases, non-circular motions present in the gas disc hinder the recovery of a rotation curve which accurately traces the underlying mass distribution; a large central deficit of dark matter, relative to the predictions of cold dark matter N-body simulations, may then be erroneously inferred.

scholarly journals The Bimodality of Galaxy Populations Revisited Through Spectral Synthesis

2006 ◽  
Vol 2 (S235) ◽  
pp. 139-139
Author(s):  
L. Sodré ◽  
A. Mateus ◽  
R. Cid Fernandes ◽  
G. Stasińska ◽  
W. Schoenell ◽  
...  
Keyword(s):  
Galaxy Formation ◽  
Spectral Synthesis ◽  
Synthesis Method ◽  
Local Universe ◽  
Massive Galaxies ◽  
Star Forming ◽  
The Galaxy ◽  
Galaxy Populations ◽  
Galaxy Population ◽  
Stellar Masses

AbstractWe revisit the bimodality of the galaxy population seen in the local universe. We address this issue in terms of physical properties of galaxies, such as mean stellar ages and stellar masses, derived from the application of a spectral synthesis method to galaxy spectra from the SDSS. We show that the mean light-weighted stellar age of galaxies presents the best description of the bimodality seen in the galaxy population. The stellar mass has an additional role since most of the star-forming galaxies present in the local universe are low-mass galaxies. Our results give support to the existence of a ‘downsizing’ in galaxy formation, where nowadays massive galaxies tend to have stellar populations older than those found in less massive objects.

scholarly journals The weak lensing radial acceleration relation: Constraining modified gravity and cold dark matter theories with KiDS-1000

2021 ◽  
Vol 650 ◽  
pp. A113
Author(s):  
Margot M. Brouwer ◽  
Kyle A. Oman ◽  
Edwin A. Valentijn ◽  
Maciej Bilicki ◽  
Catherine Heymans ◽  
...  
Keyword(s):  
Dark Matter ◽  
Galaxy Formation ◽  
Modified Gravity ◽  
Cold Dark Matter ◽  
Weak Lensing ◽  
Mass Relation ◽  
Gravitational Acceleration ◽  
Radial Acceleration ◽  
The Galaxy ◽  
The Difference

We present measurements of the radial gravitational acceleration around isolated galaxies, comparing the expected gravitational acceleration given the baryonic matter (gbar) with the observed gravitational acceleration (gobs), using weak lensing measurements from the fourth data release of the Kilo-Degree Survey (KiDS-1000). These measurements extend the radial acceleration relation (RAR), traditionally measured using galaxy rotation curves, by 2 decades in gobs into the low-acceleration regime beyond the outskirts of the observable galaxy. We compare our RAR measurements to the predictions of two modified gravity (MG) theories: modified Newtonian dynamics and Verlinde’s emergent gravity (EG). We find that the measured relation between gobs and gbar agrees well with the MG predictions. In addition, we find a difference of at least 6σ between the RARs of early- and late-type galaxies (split by Sérsic index and u − r colour) with the same stellar mass. Current MG theories involve a gravity modification that is independent of other galaxy properties, which would be unable to explain this behaviour, although the EG theory is still limited to spherically symmetric static mass models. The difference might be explained if only the early-type galaxies have significant (Mgas ≈ M⋆) circumgalactic gaseous haloes. The observed behaviour is also expected in Λ-cold dark matter (ΛCDM) models where the galaxy-to-halo mass relation depends on the galaxy formation history. We find that MICE, a ΛCDM simulation with hybrid halo occupation distribution modelling and abundance matching, reproduces the observed RAR but significantly differs from BAHAMAS, a hydrodynamical cosmological galaxy formation simulation. Our results are sensitive to the amount of circumgalactic gas; current observational constraints indicate that the resulting corrections are likely moderate. Measurements of the lensing RAR with future cosmological surveys (such as Euclid) will be able to further distinguish between MG and ΛCDM models if systematic uncertainties in the baryonic mass distribution around galaxies are reduced.

scholarly journals Galaxy Formation with Hot Dark Matter and Cosmic Strings

1988 ◽  
Vol 130 ◽  
pp. 560-561
Author(s):  
Robert H. Brandenberger
Keyword(s):  
Dark Matter ◽  
Galaxy Formation ◽  
Cosmic Strings ◽  
Severe Problem ◽  
Small Scales ◽  
The Galaxy

Hot dark matter particles have large thermal velocities at teg and hence cannot be gravitationally bound on small scales (free streaming). In models of formation of structure based on linear adiabatic perturbations all inhomogeneities on scales smaller than the maximal free streaming length λj are washed out. The mass λj inside a bail of radius exceeds the galaxy mass. Hence in the above models galaxies can only lorm by fragmentation of larger-scale objects. This is a severe problem.

scholarly journals ELUCID—EXPLORING THE LOCAL UNIVERSE WITH RECONSTRUCTED INITIAL DENSITY FIELD. III. CONSTRAINED SIMULATION IN THE SDSS VOLUME

2016 ◽  
Vol 831 (2) ◽  
pp. 164 ◽  
Author(s):  
Huiyuan Wang ◽  
H. J. Mo ◽  
Xiaohu Yang ◽  
Youcai Zhang ◽  
JingJing Shi ◽  
...  
Keyword(s):  
Initial Density ◽  
Density Field ◽  
Local Universe

THE LINK BETWEEN GALAXIES AND DARK MATTER

2011 ◽  
Vol 20 (10) ◽  
pp. 1771-1777
Author(s):  
HOUJUN MO
Keyword(s):  
Dark Matter ◽  
Galaxy Formation ◽  
Luminosity Function ◽  
The Other ◽  
Dark Matter Halos ◽  
Galaxy Formation And Evolution ◽  
The Galaxy ◽  
Galaxy Halo ◽  
Formation And Evolution ◽  
The Universe

Given that dark matter is gravitationally dominant in the universe, and that galaxy formation is closely related to dark matter halos, a key first step in understanding galaxy formation and evolution in the CDM paradigm is to quantify the galaxy-halo connection for galaxies of different properties. Here I will present results about the halo/galaxy connection obtained from two different methods. One is based on the conditional luminosity function, which describes the occupation of galaxies in halos of different masses, and the other is based on galaxy systems properly selected to represent dark halos.

DARK MATTER IN SPIRAL HALOS AND THE HALO MASS FUNCTION

1994 ◽  
Vol 03 (supp01) ◽  
pp. 87-92
Author(s):  
KEITH M. ASHMAN ◽  
PAOLO SALUCCI ◽  
MASSIMO PERSIC
Keyword(s):  
Dark Matter ◽  
Hierarchical Clustering ◽  
Galaxy Formation ◽  
Luminosity Function ◽  
Mass Function ◽  
Dark Halo ◽  
Constant Mass ◽  
High Luminosity ◽  
The Galaxy ◽  
Galaxy Luminosity Function

Evidence that low-luminosity spirals have a higher dark matter fraction than their high-luminosity counterparts is discussed. The empirical correlation between dark matter fraction and luminosity is used, in conjunction with the galaxy luminosity function of spirals, to derive the dark halo mass function of these galaxies. The mass function is shown to be consistent with hierarchical clustering models of galaxy formation. This contrasts with previous results based on the assumption of a constant mass-to-light ratio for all spirals, which predict too many low-luminosity galaxies.

scholarly journals An interesting case of the formation and evolution of a barred galaxy in the cosmological context

2020 ◽  
Vol 642 ◽  
pp. L12
Author(s):  
Ewa L. Łokas
Keyword(s):  
Dark Matter ◽  
Galaxy Formation ◽  
Cosmic Time ◽  
Galaxy Cluster ◽  
Interesting Case ◽  
Massive Galaxies ◽  
Barred Galaxies ◽  
Tidal Interactions ◽  
The Galaxy ◽  
Formation And Evolution

Elongated, bar-like galaxies without a significant disk component, with little rotation support and no gas, often form as a result of tidal interactions with a galaxy cluster, as was recently demonstrated using the IllustrisTNG-100 simulation. Galaxies that exhibit similar properties are, however, also found to be infalling into the cluster for the first time. We use the same simulation to study in detail the history of such a galaxy over cosmic time in order to determine its origin. The bar appears to be triggered at t = 6.8 Gyr by the combined effect of the last significant merger with a subhalo and the first passage of another dwarf satellite, both ten times less massive than the galaxy. The satellites deposit all their gas in the galaxy, contributing to its third and last star-formation episode, which perturbs the disk and may also contribute to the formation of the bar. The galaxy then starts to lose its gas and dark matter due to its passage near a group of more massive galaxies. The strongest interaction involves a galaxy 22 times more massive, leaving the barred galaxy with no gas and half of its maximum dark matter mass. During this time, the bar grows steadily, seemingly unaffected by the interactions, although they may have aided its growth by stripping the gas. The studied galaxy, together with two other similar objects briefly discussed in this Letter, suggest the existence of a new class of early-type barred galaxies and thereby demonstrate the importance of interactions in galaxy formation and evolution.

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