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Galaxies, Volume 1, Issue 1 (June 2013), Pages 1-82

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Editorial

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Open AccessEditorial Galaxies: An International Multidisciplinary Open Access Journal
Galaxies 2013, 1(1), 1-5; doi:10.3390/galaxies1010001
Received: 23 October 2012 / Accepted: 1 November 2012 / Published: 8 November 2012
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Abstract
The knowledge of the universe as a whole, its origin, size and shape, its evolution and future, has always intrigued the human mind. Galileo wrote: “Nature’s great book is written in mathematical language.” This new journal will be devoted to [...] Read more.
The knowledge of the universe as a whole, its origin, size and shape, its evolution and future, has always intrigued the human mind. Galileo wrote: “Nature’s great book is written in mathematical language.” This new journal will be devoted to both aspects of knowledge: the direct investigation of our universe and its deeper understanding, from fundamental laws of nature which are translated into mathematical equations, as Galileo and Newton—to name just two representatives of a plethora of past and present researchers—already showed us how to do. Those physical laws, when brought to their most extreme consequences—to their limits in their respective domains of applicability—are even able to give us a plausible idea of how the origin of our universe came about and also of how we can expect its future to evolve and, eventually, how its end will take place. These laws also condense the important interplay between mathematics and physics as just one first example of the interdisciplinarity that will be promoted in the Galaxies Journal. Full article

Research

Jump to: Editorial

Open AccessArticle Exact Expressions for the Pericenter Precession Caused by Some Dark Matter Distributions and Constraints on Them from Orbital Motions in the Solar System, in the Double Pulsar and in the Galactic Center
Galaxies 2013, 1(1), 6-30; doi:10.3390/galaxies1010006
Received: 24 April 2013 / Revised: 16 May 2013 / Accepted: 16 May 2013 / Published: 28 May 2013
Cited by 18 | PDF Full-text (446 KB) | HTML Full-text | XML Full-text
Abstract
We analytically calculate the secular precession of the pericenter of a test particle orbiting a central body surrounded by a continuous distribution of Dark Matter (DM) by using some commonly adopted spherically symmetric density profiles for it. We obtain exact expressions without [...] Read more.
We analytically calculate the secular precession of the pericenter of a test particle orbiting a central body surrounded by a continuous distribution of Dark Matter (DM) by using some commonly adopted spherically symmetric density profiles for it. We obtain exact expressions without resorting to a-priori simplifying assumptions on the orbital geometry of the test particle. Our formulas allow us to put constraints on the parameters of the DM distributions considered in several local astronomical and astrophysical scenarios, such as the Sun's planetary system, the double pulsar, and the stellar system around the supermassive black hole in Sgr A, all characterized by a wide variety of orbital configuratio ns. As far as our Solar System is concerned, latest determinations of the supplementary perihelion precessions ̟˙ with the EPM2011 ephemerides and the common power-law DM density profile ρDM(r) = ρ0rγ λγ yield 5 × 103 GeV cm−3 (γ = 0) ≤ ρ0 ≤ 8 × 103 GeV cm−3 (γ = 4), corresponding to 8.9 × 10−21 g cm−3 ≤ ρ0 ≤ 1.4 × 10−20 g cm−3, at the Saturn's distance. From the periastron of the pulsar PSR J0737-3039A and the same power-low DM density, one has 1.7 × 1016 GeV cm−3 (γ = 0) ≤ ρ0 ≤ 2 × 1016 (γ = 4) GeV cm−3, corresponding to 3.0 × 10−8 g cm−3 ≤ ρ0 ≤ 3.6 × 10−8 g cm−3. The perinigricon of the S0-2 star in Sgr A and the power-law DM model give 1.2 × 1013 GeV cm−3 (γ = 0) ≤ ρ0 ≤ 1 × 1016 (γ = 4, λ = rmin) GeV cm−3, corresponding to 2.1 × 10−11 g cm−3 ≤ ρ0 ≤ 1.8 × 10−8 g cm−3. Full article
(This article belongs to the Special Issue Cosmology with Fluid Components)
Open AccessArticle Halo Models of Large Scale Structure and Reliability of Cosmological N-Body Simulations
Galaxies 2013, 1(1), 31-43; doi:10.3390/galaxies1010031
Received: 15 April 2013 / Revised: 22 May 2013 / Accepted: 23 May 2013 / Published: 29 May 2013
Cited by 2 | PDF Full-text (520 KB) | HTML Full-text | XML Full-text
Abstract
Halo models of the large scale structure of the Universe are critically examined, focusing on the definition of halos as smooth distributions of cold dark matter. This definition is essentially based on the results of cosmological N-body simulations. By a careful analysis [...] Read more.
Halo models of the large scale structure of the Universe are critically examined, focusing on the definition of halos as smooth distributions of cold dark matter. This definition is essentially based on the results of cosmological N-body simulations. By a careful analysis of the standard assumptions of halo models and N-body simulations and by taking into account previous studies of self-similarity of the cosmic web structure, we conclude that N-body cosmological simulations are not fully reliable in the range of scales where halos appear. Therefore, to have a consistent definition of halos is necessary either to define them as entities of arbitrary size with a grainy rather than smooth structure or to define their size in terms of small-scale baryonic physics. Full article
(This article belongs to the Special Issue Cosmology with Fluid Components)
Figures

Open AccessArticle Attitudes towards Autonomous Data Collection and Analysis in the Planetary Science Community
Galaxies 2013, 1(1), 44-64; doi:10.3390/galaxies1010044
Received: 12 April 2013 / Revised: 29 May 2013 / Accepted: 11 June 2013 / Published: 18 June 2013
Cited by 3 | PDF Full-text (503 KB) | HTML Full-text | XML Full-text
Abstract
As missions are planned to targets further away from Earth, it becomes all but required to increase the role of autonomy in the mission. An investigation of what aspects of mission operations and decision making autonomy will be accepted in by the [...] Read more.
As missions are planned to targets further away from Earth, it becomes all but required to increase the role of autonomy in the mission. An investigation of what aspects of mission operations and decision making autonomy will be accepted in by the planetary science community is thus required to aid in development planning. This paper presents a data set collected regarding attitudes towards autonomous data collection and analysis in the planetary science community and initial analysis of this data. A survey, conducted at the 2013 Lunar and Planetary Science Conference, asked respondents to identify whether or not they would accept conclusions drawn by autonomous data collection techniques and what factors would impact this acceptance. It also looked at the acceptance of computers and computer software in the data collection and analysis process. Full article
Open AccessArticle Cosmological Observations in a Modified Theory of Gravity (MOG)
Galaxies 2013, 1(1), 65-82; doi:10.3390/galaxies1010065
Received: 10 May 2013 / Accepted: 15 June 2013 / Published: 20 June 2013
Cited by 9 | PDF Full-text (335 KB) | HTML Full-text | XML Full-text
Abstract
Our Modified Gravity Theory (MOG) is a gravitational theory without exotic dark matter, based on an action principle. MOG has been used successfully tomodel astrophysical phenomena, such as galaxy rotation curves, galaxy cluster masses and lensing. MOG may also be able to [...] Read more.
Our Modified Gravity Theory (MOG) is a gravitational theory without exotic dark matter, based on an action principle. MOG has been used successfully tomodel astrophysical phenomena, such as galaxy rotation curves, galaxy cluster masses and lensing. MOG may also be able to account for cosmological observations. We assume that the MOG point source solution can be used to describe extended distributions of matter via an appropriately modified Poisson equation. We use this result to model perturbation growth in MOG and find that it agrees well with the observed matter power spectrum at present. As the resolution of the power spectrum improves with increasing survey size, however, significant differences emerge between the predictions of MOG and the standard Λ-cold dark matter (Λ-CDM) model, as in the absence of exotic darkmatter, oscillations of the power spectrum in MOG are not suppressed. We can also use MOG to model the acoustic power spectrum of the cosmic microwave background. A suitably adapted semi-analytical model offers a first indication that MOG may pass this test and correctly model the peak of the acoustic spectrum. Full article
(This article belongs to the Special Issue Cosmology with Fluid Components)

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