scholarly journals Dark-Matter Content of Early-Type Galaxies with Planetary Nebulae

2007 ◽  
Vol 3 (S244) ◽  
pp. 289-294 ◽  
Author(s):  
N. R. Napolitano ◽  
A. J. Romanowsky ◽  
L. Coccato ◽  
M. Capaccioli ◽  
N. G. Douglas ◽  
...  
Keyword(s):  
Dark Matter ◽  
Planetary Nebula ◽  
Planetary Nebulae ◽  
Matter Content ◽  
The Other ◽  
Early Type ◽  
Scientific Objective ◽  
Target Sample ◽  
The Galaxy ◽  
William Herschel

AbstractWe examine the dark matter properties of nearby early-type galaxies using planetary nebulae (PNe) as mass probes. We have designed a specialised instrument, the Planetary Nebula Spectrograph (PN.S) operating at the William Herschel telescope, with the purpose of measuring PN velocities with best efficiency. The primary scientific objective of this custom-built instrument is the study of the PN kinematics in 12 ordinary round galaxies. Preliminary results showing a dearth of dark matter in ordinary galaxies (Romanowskyet al. 2003) are now confirmed by the first complete PN.S datasets. On the other hand early-type galaxies with a “regular” dark matter content are starting to be observed among the brighter PN.S target sample, thus confirming a correlation between the global dark-to-luminous mass virial ratio (fDM=MDMM*) and the galaxy luminosity and mass.

scholarly journals Low dark matter content of the nearby early-type galaxy NGC 821

2014 ◽  
pp. 29-36 ◽  
Author(s):  
S. Samurovic ◽  
A. Vudragovic ◽  
M. Jovanovic ◽  
M.M. Cirkovic
Keyword(s):  
Dark Matter ◽  
Globular Clusters ◽  
Planetary Nebulae ◽  
Matter Content ◽  
Kinematics And Dynamics ◽  
Constant Mass ◽  
Early Type ◽  
Kinematic Data ◽  
Early Type Galaxy ◽  
Dynamical Modelling

In this paper we analyze the kinematics and dynamics of the nearby early-type galaxy NGC 821 based on its globular clusters (GCs) and planetary nebulae (PNe). We use PNe and GCs to extract the kinematics of NGC 821 which is then used for the dynamical modelling based on the Jeans equation. We apply the Jeans equation using the Newtonian mass-follows-light approach assuming constant mass-to-light ratio and find that using such an approach we can successfully fit the kinematic data. The inferred constant mass-to-light ratio, 4:2 < M=LB < 12:4 present throughout the whole galaxy, implies the lack of significant amount of dark matter. We also used three different MOND approaches and found that we can fit the kinematic data without the need for additional, dark, component.

scholarly journals Luminous and dark matter in early-type lens galaxies

2009 ◽  
Vol 5 (H15) ◽  
pp. 70-70
Author(s):  
C. Grillo
Keyword(s):  
Dark Matter ◽  
Galaxy Formation ◽  
Gravitational Lensing ◽  
Elliptical Galaxy ◽  
Matter Content ◽  
Effective Radius ◽  
Dark Matter Halo ◽  
Early Type ◽  
The Galaxy ◽  
Lens Galaxies

In the past few years gravitational lensing has allowed astrophysicists to make great progress in the understanding of the internal structure of early-type galaxies. By taking advantage of accurate photometric and spectroscopic measurements, the luminous and dark matter content of lens galaxies can in principle be disentangled (e.g., Grillo et al. 2008, 2009). SDSS J1538+5817 is an extraordinary strong lensing system composed of an elliptical galaxy and two equally-distant sources located, respectively, at redshifts 0.143 and 0.531 (Grillo et al., submitted to ApJ). The sources are lensed into two and four images with an almost complete Einstein ring, covering a rather large region on the lens plane. By using HST/ACS and WFPC2 imaging and NOT/ALFOSC spectroscopy, we have investigated the lens total mass distribution within one effective radius. Then, we have fitted the SDSS multicolor photometry of the galaxy with composite stellar population models to obtain its luminous mass. By combining lensing and photometric measurements, we have estimated the lens mass in terms of luminous and dark matter components and studied the global properties of the dark matter halo. The exceptional lensing configuration of this system has allowed us to conclude that the galaxy dark matter density distribution is shallower and more diffused than the luminous one and the former starts exceeding the latter at a distance of approximately 1.5 times the effective radius. Extending these results to a larger number of lenses would help us to decipher the processes that rule galaxy formation and evolution in the LCDM scenario.

scholarly journals Is there a dichotomy in the Dark Matter as well as in the Baryonic Matter properties of ellipticals?

2004 ◽  
Vol 220 ◽  
pp. 173-174
Author(s):  
N. R. Napolitano ◽  
M. Capaccioli ◽  
M. Arnaboldi ◽  
M. R. Merrifield ◽  
N. G. Douglas ◽  
...  
Keyword(s):  
Dark Matter ◽  
Structural Parameters ◽  
Matter Content ◽  
Baryonic Matter ◽  
Early Type

We have found a correlation between the M / L global gradients and the structural parameters of the luminous components of a sample of 19 early-type galaxies. Such a correlation supports the hypothesis that there is a connection between the dark matter content and the evolution of the baryonic component in such systems.

scholarly journals Dark matter content and internal dynamics of NGC 4697: nmagic particle models from slit data and planetary nebula velocities

2008 ◽  
Vol 385 (4) ◽  
pp. 1729-1748 ◽  
Author(s):  
Flavio De Lorenzi ◽  
Ortwin Gerhard ◽  
Roberto P. Saglia ◽  
Niranjan Sambhus ◽  
Victor P. Debattista ◽  
...  
Keyword(s):  
Dark Matter ◽  
Planetary Nebula ◽  
Matter Content ◽  
Internal Dynamics

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.

scholarly journals Hubble parameter and the potential of the cosmological scalar field

2020 ◽  
pp. 15-19
Author(s):  
V. Zhdanov ◽  
A. Alexandrov ◽  
O. Stashko
Keyword(s):  
Dark Matter ◽  
Scalar Field ◽  
Hubble Parameter ◽  
Three Dimensional ◽  
Approximation Error ◽  
Field Potential ◽  
Matter Content ◽  
Order Equation ◽  
The Other ◽  
Cold Matter

We consider a homogeneous isotropic Universe filled with cold matter (with zero pressure) and dynamic dark energy in a form of a scalar field. For known scalar field potential V(φ), the Friedmann equations are reduced to a system of the first order equation for the Hubble parameter H(z) and the second order equation for the scalar field as functions of the redshift z. On the other hand, knowledge of H(z) allows us to get the scalar field potential in a parametric form for a known cold matter content and three dimensional curvature parameter. We analyze when the accepted model mimics the dependence H(z) derived in the framework of the other models, e.g., hydrodynamic ones. Two examples of this mimicry are considered. The first one deals with the case when H2(z)~ Ωm(1+z)3+ΩΛ, but Ωm parameter overestimates the input of the cold matter (dark matter+baryons). The resulting scalar field potential is V(φ)=a+bsinh2(cφ), where the constants a,b,c depend on the Ω – parameters of the problem. In the other example we assume that some part of the dark matter has a non-zero equation of state p=wε, -1<w<1. In this case H2(z)~ Ωdm1(1+z)3(1+w)+ Ωb+Ωdm2)(1+z)3+ΩΛ. The corresponding potentials are defined for positive values of φ. For both signs of w potential V(φ) is a monotonically increasing function with typically an asymptotically exponential behavior; though for some choice of parameters we may have a singularity of V(φ)on a finite interval. Then we consider fitting of the potential for w from the interval [-0.2,0.2] for three different values of Ωdm2 by means of a simple formula Vfit(φ)=p0+p1exp(p2 φ). The dependencies pi(w) are presented and the approximation error is estimated.

scholarly journals The Cosmological Decrease of Galactic Density and the Induced Retarded Gravity Effect on Rotation Curves

2021 ◽  
Author(s):  
Asher Yahalom
Keyword(s):  
Dark Matter ◽  
Galactic Center ◽  
Temporal Change ◽  
The Other ◽  
Local Effects ◽  
Physical Systems ◽  
Cosmic Expansion ◽  
The Galaxy ◽  
Action At A Distance ◽  
Retardation Effects

Galaxies are huge physical systems having dimensions of many tens of thousands of light years. Thus any change at the galactic center will be noticed at the rim only tens of thousands of years later. Those retardation effects seems to be neglected in present day galactic modelling used to calculate rotational velocities of matter in the rims of the galaxy and surrounding gas. The significant differences between the predictions of Newtonian instantaneous action at a distance and observed velocities are usually explained by either assuming dark matter or by modifying the laws of gravity (MOND). In this paper we will show that taking general relativity seriously without neglecting retardation effects one can explain the radial velocities of galactic matter without postulating dark matter. However, this will rely on a temporal change of galactic mass. We will compare two different mechanisms of density change, one is local, that is accretion of matter from the intergalactic medium. The other is global, that is the cosmological decrease of density due to the cosmic expansion. It will be shown that local effects are much more important in this respect.

scholarly journals Imprint of Pressure on Characteristic Dark Matter Profiles: The Case of ESO0140040

Galaxies ◽  
2020 ◽  
Vol 8 (4) ◽  
pp. 74
Author(s):  
Kuantay Boshkayev ◽  
Talgar Konysbayev ◽  
Ergali Kurmanov ◽  
Orlando Luongo ◽  
Marco Muccino
Keyword(s):  
Dark Matter ◽  
Complex Structure ◽  
Matter Content ◽  
Model Parameters ◽  
Matter Distribution ◽  
Density Profiles ◽  
The Galaxy ◽  
Dark Matter Distribution ◽  
Observational Signature

We investigate the dark matter distribution in the spiral galaxy ESO0140040, employing the most widely used density profiles: the pseudo-isothermal, exponential sphere, Burkert, Navarro-Frenk-White, Moore and Einasto profiles. We infer the model parameters and estimate the total dark matter content from the rotation curve data. For simplicity, we assume that dark matter distribution is spherically symmetric without accounting for the complex structure of the galaxy. Our predictions are compared with previous results and the fitted parameters are statistically confronted for each profile. We thus show that although one does not include the galaxy structure it is possible to account for the same dynamics assuming that dark matter provides a non-zero pressure in the Newtonian approximation. In this respect, we solve the hydrostatic equilibrium equation and construct the dark matter pressure as a function for each profile. Consequently, we discuss the dark matter equation of state and calculate the speed of sound in dark matter. Furthermore, we interpret our results in view of our approach and we discuss the role of the refractive index as an observational signature to discriminate between our approach and the standard one.

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