scholarly journals Dark matter halo sparsity of modified gravity scenarios

2020 ◽  
Vol 102 (4) ◽  
Author(s):  
Pier Stefano Corasaniti ◽  
Carlo Giocoli ◽  
Marco Baldi
Keyword(s):  
Dark Matter ◽  
Modified Gravity ◽  
Dark Matter Halo

scholarly journals Detecting ultralight axion dark matter wind with laser interferometers

2016 ◽  
Vol 26 (07) ◽  
pp. 1750063 ◽  
Author(s):  
Arata Aoki ◽  
Jiro Soda
Keyword(s):  
Dark Matter ◽  
Dark Energy ◽  
Modified Gravity ◽  
Laser Interferometer ◽  
Mass Range ◽  
Dark Matter Halo ◽  
Detector Signal ◽  
Modified Gravity Theory ◽  
Axion Field ◽  
Laser Interferometers

The ultralight axion with mass around [Formula: see text][Formula: see text]eV is known as a candidate of dark matter. A peculiar feature of the ultralight axion is oscillating pressure in time, which produces oscillation of gravitational potentials. Since the solar system moves through the dark matter halo at the velocity of about [Formula: see text], there exists axion wind, which looks like scalar gravitational waves for us. Hence, there is a chance to detect ultralight axion dark matter with a wide mass range by using laser interferometer detectors. We calculate the detector signal induced by the oscillating pressure of the ultralight axion field, which would be detected by future laser interferometer experiments. We also argue that the detector signal can be enhanced due to the resonance in modified gravity theory explaining the dark energy.

scholarly journals Beyond ΛCDM with H i intensity mapping: robustness of cosmological constraints in the presence of astrophysics

2020 ◽  
Vol 496 (4) ◽  
pp. 4115-4126 ◽  
Author(s):  
Stefano Camera ◽  
Hamsa Padmanabhan
Keyword(s):  
Dark Matter ◽  
Modified Gravity ◽  
Cosmological Parameters ◽  
Neutral Hydrogen ◽  
Temperature Fluctuations ◽  
Dark Matter Halo ◽  
Cosmological Constraints ◽  
Intensity Mapping ◽  
Standard Cosmological Model ◽  
First Time

ABSTRACT Mapping the unresolved intensity of the 21-cm emission of neutral hydrogen (H i) is now regarded as one the most promising tools for cosmological investigation in the coming decades. Here, we investigate, for the first time, extensions of the standard cosmological model, such as modified gravity and primordial non-Gaussianity, taking self-consistently into account. The present constraints on the astrophysics of H i clustering in the treatment of the brightness temperature fluctuations. To understand the boundaries within which results thus obtained can be considered reliable, we examine the robustness of cosmological parameter estimation performed via studies of 21-cm intensity mapping, against our knowledge of the astrophysical processes leading to H i clustering. Modelling of astrophysical effects affects cosmological observables through the relation linking the overall H i mass in a bound object, to the mass of the underlying dark matter halo that hosts it. We quantify the biases in estimates of standard cosmological parameters and those describing modified gravity and primordial non-Gaussianity that are obtained if one misconceives the slope of the relation between H i mass and halo mass, or the lower virial velocity cut-off for a dark matter halo to be able to host H i. Remarkably, we find that astrophysical uncertainties will not affect searches for primordial non-Gaussianity – one of the strongest science cases for H i intensity mapping – despite the signal being deeply linked to the H i bias.

scholarly journals Two-component galaxy models with a central BH – II. The ellipsoidal case

2020 ◽  
Vol 500 (1) ◽  
pp. 1054-1070
Author(s):  
Luca Ciotti ◽  
Antonio Mancino ◽  
Silvia Pellegrini ◽  
Azadeh Ziaee Lorzad
Keyword(s):  
Dark Matter ◽  
Stellar Dynamics ◽  
Azimuthal Velocity ◽  
Dark Matter Halo ◽  
Gas Flows ◽  
Total Density ◽  
Density Distributions ◽  
Stellar Component ◽  
Two Component ◽  
Analytical Formulae

ABSTRACT Recently, two-component spherical galaxy models have been presented, where the stellar profile is described by a Jaffe law, and the total density by another Jaffe law, or by an r−3 law at large radii. We extend these two families to their ellipsoidal axisymmetric counterparts: the JJe and J3e models. The total and stellar density distributions can have different flattenings and scale lengths, and the dark matter halo is defined by difference. First, the analytical conditions required to have a nowhere negative dark matter halo density are derived. The Jeans equations for the stellar component are then solved analytically, in the limit of small flattenings, also in the presence of a central BH. The azimuthal velocity dispersion anisotropy is described by the Satoh k-decomposition. Finally, we present the analytical formulae for velocity fields near the centre and at large radii, together with the various terms entering the virial theorem. The JJe and J3e models can be useful in a number of theoretical applications, e.g. to explore the role of the various parameters (flattening, relative scale lengths, mass ratios, rotational support) in determining the behaviour of the stellar kinematical fields before performing more time-expensive integrations with specific galaxy models, to test codes of stellar dynamics and in numerical simulations of gas flows in galaxies.

scholarly journals Brightest cluster galaxies: the centre can(not?) hold

2020 ◽  
Vol 500 (1) ◽  
pp. 310-318
Author(s):  
Roberto De Propris ◽  
Michael J West ◽  
Felipe Andrade-Santos ◽  
Cinthia Ragone-Figueroa ◽  
Elena Rasia ◽  
...  
Keyword(s):  
Dark Matter ◽  
Local Environment ◽  
Major Axis ◽  
Theoretical Models ◽  
Dark Matter Halo ◽  
Gas Distribution ◽  
X Ray ◽  
Cluster Galaxies ◽  
Peculiar Velocities ◽  
Brightest Cluster Galaxies

ABSTRACT We explore the persistence of the alignment of brightest cluster galaxies (BCGs) with their local environment. We find that a significant fraction of BCGs do not coincide with the centroid of the X-ray gas distribution and/or show peculiar velocities (they are not at rest with respect to the cluster mean). Despite this, we find that BCGs are generally aligned with the cluster mass distribution even when they have significant offsets from the X-ray centre and significant peculiar velocities. The large offsets are not consistent with simple theoretical models. To account for these observations BCGs must undergo mergers preferentially along their major axis, the main infall direction. Such BCGs may be oscillating within the cluster potential after having been displaced by mergers or collisions, or the dark matter halo itself may not yet be relaxed.

scholarly journals Dwarf galaxies without dark matter: constraints on modified gravity

2020 ◽  
Vol 501 (1) ◽  
pp. 254-260
Author(s):  
Ali Rida Khalifeh ◽  
Raul Jimenez
Keyword(s):  
Dark Matter ◽  
Modified Gravity ◽  
Virial Theorem ◽  
Dwarf Galaxies ◽  
Strong Support ◽  
Gravity Models ◽  
Birkhoff Theorem ◽  
Astronomical Surveys ◽  
Stringent Test ◽  
Modified Gravity Models

ABSTRACT The discovery of 19 dwarf galaxies without dark matter (DM) provides, counterintuitively, strong support for the ΛCDM standard model of cosmology. Their presence is well accommodated in a scenario where the DM is in the form of cold dark particles. However, it is interesting to explore quantitatively what is needed from modified gravity models to accommodate the presence of these galaxies and what extra degree of freedom is needed in these models. To this end, we derive the dynamics at galaxy scales (Virial theorem) for a general class of modified gravity models. We distinguish between theories that satisfy the Jebsen–Birkhoff theorem, and those that do not. Our aim is to develop tests that can distinguish whether DM is part of the theory of gravity or a particle. The 19 dwarf galaxies discovered provide us with a stringent test for models of modified gravity. Our main finding is that there will always be an extra contribution to the Virial theorem coming from the modification of gravity, even if a certain galaxy shows very small, if not negligible, trace of DM, as has been reported recently. Thus, if these and more galaxies are confirmed as devoid (or negligible) of DM, while other similar galaxies have abundant DM, it seems interesting to find modifications of gravity to describe DM. Our result can be used by future astronomical surveys to put constraints on the parameters of modified gravity models at astrophysical scales where DM is described as such.

scholarly journals Does the Cosmological Expansion Change Local Dynamics?

Symmetry ◽  
2021 ◽  
Vol 13 (8) ◽  
pp. 1417
Author(s):  
Marcelo Schiffer
Keyword(s):  
Dark Matter ◽  
Modified Gravity ◽  
Hubble Constant ◽  
Matter Content ◽  
Matter Distribution ◽  
Present Value ◽  
Field Equations ◽  
Local Dynamics ◽  
Cosmological Expansion ◽  
Modified Gravity Theories

It is a well-known fact that the Newtonian description of dynamics within Galaxies for its known matter content is in disagreement with the observations as the acceleration approaches a0≈1.2×10−10 m/s2 (slighter larger for clusters). Both the Dark Matter scenario and Modified Gravity Theories (MGT) fail to explain the existence of such an acceleration scale. Motivated by the closeness of the acceleration scale and the Hubble constant cH0≈10−9 h m/s2, we are led to analyze whether this coincidence might have a Cosmological origin for scalar-tensor and spinor-tensor theories by performing detailed calculations for perturbations that represent the local matter distribution on the top of the cosmological background. Then, we solve the field equations for these perturbations in a power series in the present value of the Hubble constant. As we shall see, for both theories, the power expansion contains only even powers in the Hubble constant, a fact that renders the cosmological expansion irrelevant for the local dynamics.

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 2dF Spectroscopy of Globular Clusters in M104

2005 ◽  
Vol 13 ◽  
pp. 199-199
Author(s):  
Terry Bridges ◽  
Steve Zepf ◽  
Katherine Rhode ◽  
Ken Freeman
Keyword(s):  
Dark Matter ◽  
Strong Evidence ◽  
Total Mass ◽  
Globular Clusters ◽  
Total Sample ◽  
Dark Matter Halo ◽  
Large Radius ◽  
Counter Rotation ◽  
Spatial Coverage

AbstractWe have found 56 new globular clusters in M104 from 2dF multi-fiber spectroscopy, doubling the number of confirmed clusters, and extending the spatial coverage to 50 kpc radius. We find no significant rotation in the total sample, or for subsets split by color or radius. However, there are hints that the blue clusters have a higher rotation than the red clusters, and for counter-rotation of clusters at large radius. We find a total mass of M ~ 1 × 1012M⊙ and a (M/L)B =30 out to 50 kpc radius, which is strong evidence for a dark matter halo in M104.

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