Galaxy Research Papers - Academia.edu (original) (raw)

«I Romanzi di Urania», «I Romanzi del Cosmo», «Oltre il Cielo», «Galaxy» e «Galassia», «Futuro» e «Robot» sono i laboratori che, tra anni Cinquanta e Settanta, hanno proposto la fantascienza in Italia come un genere riconoscibile e... more

«I Romanzi di Urania», «I Romanzi del Cosmo», «Oltre il Cielo», «Galaxy» e «Galassia», «Futuro» e «Robot» sono i laboratori che, tra anni Cinquanta e Settanta, hanno proposto la fantascienza in Italia come un genere riconoscibile e declinato in molti modi differenti. Sono queste le sedi in cui hanno trovato posto e si sono sviluppate le traduzioni della fantascienza anglo-americana, i primi autori italiani, la critica e i dibattiti attorno al genere.
Lo studio ripercorre la storia di queste pubblicazioni e dei protagonisti che ne hanno popolato le pagine, per ricostruire, tra avventure spaziali e raffinate distopie urbane, riuso e invenzione, l'alba di una fantascienza scritta in lingua italiana.
http://mimesisedizioni.it/fantascienza-italiana.html

We consider the Universe deep inside the cell of uniformity. At these scales, the Universe is filled with inhomogeneously distributed discrete structures (galaxies, groups and clusters of galaxies), which perturb the background Friedmann... more

We consider the Universe deep inside the cell of uniformity. At these scales, the Universe is filled with inhomogeneously distributed discrete structures (galaxies, groups and clusters of galaxies), which perturb the background Friedmann model. Here, the mechanical approach (Eingorn & Zhuk, 2012) is the most appropriate to describe the dynamics of the inhomogeneities which is defined, on the one hand, by gravitational potentials of inhomogeneities and, on the other hand, by the cosmological expansion of the Universe. In this paper, we present additional arguments in favor of this approach. First, we estimate the size of the cell of uniformity. With the help of the standard methods of statistical physics and for the galaxies of the type of the Milky Way and Andromeda, we get that it is of the order of 190 Mpc which is rather close to observations. Then, we show that the nonrelativistic approximation (with respect to the peculiar velocities) is valid for zlesssim10z \lesssim 10zlesssim10, i.e. approximately for 13 billion years from the present moment. We consider scalar perturbations and, within the Lambda\LambdaLambdaCDM model, justify the main equations. Moreover, we demonstrate that radiation can be naturally incorporated into our scheme. This emphasizes the viability of our approach. This approach gives a possibility to analyze different cosmological models and compare them with the observable Universe. For example, we indicate some problematic aspects of the spatially flat models. Such models require a rather specific distribution of the inhomogeneities to get a finite potential at any points outside gravitating masses. We also criticize the application of the Schwarzschild-de Sitter solution to the description of the motion of test bodies on the cosmological background.

It is well known that soft iron owes its transformation into steel to the addition of carbon. Carbon is the hardest substance on Earth - diamond. Carbon is the mainstay of Life on Earth, since everything living on our planet is built from... more

It is well known that soft iron owes its transformation into steel to the addition of carbon. Carbon is the hardest substance on Earth - diamond. Carbon is the mainstay of Life on Earth, since everything living on our planet is built from it. This all means: carbon is the mainstay of our world. But find out: it is also the stronghold of the entire Universe! The mythical metal orichalcum spoken of by Plato and Tolkien's mithril are carbon, structurally superior to diamond. The Moon is made from it by the hand of God. The UFO is made from it by the hand of the Other. // Общеизвестно, что своим превращением в сталь мягкое железо обязано добавке углерода. Углеродом есть самое твердое вещество Земли — алмаз. Углерод — оплот Жизни на Земле, ибо из него на ней построено живое. Все это означает: углерод в нашем мире есть главная твердь. Но узнайте: он есть и твердь Мира! Мифичный металл орихалк, о каком рек Платон, и мифрил Толкина — это углерод, структурно высший над алмазом. Из него рукою Бога сделана Луна. Из него рукой Иного сделан НЛО.

When and how did the universe begin? Why are we here? Is the apparent 'grand design' of our universe evidence for a benevolent creator who set things in motion? Or does science offer another explanation? In The Grand Design, the most... more

In this paper we study scalar perturbations of the metric for nonlinear f(R)f(R)f(R) models. We consider the Universe at the late stage of its evolution and deep inside the cell of uniformity. We investigate the astrophysical approach in the... more

In this paper we study scalar perturbations of the metric for nonlinear f(R)f(R)f(R) models. We consider the Universe at the late stage of its evolution and deep inside the cell of uniformity. We investigate the astrophysical approach in the case of Minkowski spacetime background and two cases in the cosmological approach, the large scalaron mass approximation and the quasi-static approximation, getting explicit expressions for scalar perturbations for both these cases. In the most interesting quasi-static approximation, the scalar perturbation functions depend on both the nonlinearity function f(R)f(R)f(R) and the scale factor aaa. Hence, we can study the dynamical behavior of the inhomogeneities (e.g., galaxies and dwarf galaxies) including into consideration their gravitational attraction and the cosmological expansion, and also taking into account the effects of nonlinearity. Our investigation is valid for functions f(R)f(R)f(R) which have stable de Sitter points in future with respect to the present time, that is typical for the most popular f(R)f(R)f(R) models.

We report calculations of the stellar and gaseous response to a Milky Way mass distribution model including a spiral pattern with a locus as traced by K-band observations, over imposed on the axisymmetric components in the plane of the... more

We report calculations of the stellar and gaseous response to a Milky Way mass distribution model including a spiral pattern with a locus as traced by K-band observations, over imposed on the axisymmetric components in the plane of the disk. The stellar study extends calculations from previous work concerning the self-consistency of the pattern. The stellar response to the imposed spiral mass is studied via computations of the central family of periodic and nearby orbits as a function of the pattern rotation speed, Ωp, among other parameters. A fine grid of values of Ωp was explored ranging from 12 to 25 km s −1 kpc −1. Dynamical self-consistency is highly sensitive to Ωp, with the best fit appearing at 20 km s −1 kpc −1. We give an account of recent independent pieces of theoretical and observational work that are dependent on the value of Ωp, all of which are consistent with the value found here; the recent star formation history of the Milky Way, local inferences of cosmic ray fl...

Scalar cosmological perturbations are investigated in the framework of a model with interacting dark energy and dark matter. In addition to these constituents, the inhomogeneous Universe is supposed to be filled with the standard... more

Scalar cosmological perturbations are investigated in the framework of a model with interacting dark energy and dark matter. In addition to these constituents, the inhomogeneous Universe is supposed to be filled with the standard noninteracting constituents corresponding to the conventional Lambda\LambdaLambdaCDM model. The interaction term is chosen in the form of a linear combination of dark sector energy densities with evolving coefficients. The methods of discrete cosmology are applied, and strong theoretical constraints on the parameters of the model are derived. A brief comparison with observational data is performed.

Massive stars disrupt their natal molecular cloud material through radiative and mechanical feedback processes. These processes have profound effects on the evolution of interstellar matter in our Galaxy and throughout the universe, from... more

Massive stars disrupt their natal molecular cloud material through radiative and mechanical feedback processes. These processes have profound effects on the evolution of interstellar matter in our Galaxy and throughout the universe, from the era of vigorous star formation at redshifts of 1–3 to the present day. The dominant feedback processes can be probed by observations of the Photo-Dissociation Regions (PDRs) where the far-ultraviolet photons of massive stars create warm regions of gas and dust in the neutral atomic and molecular gas. PDR emission provides a unique tool to study in detail the physical and chemical processes that are relevant for most of the mass in inter- and circumstellar media including diffuse clouds, proto-planetary disks, and molecular cloud surfaces, globules, planetary nebulae, and star-forming regions. PDR emission dominates the infrared (IR) spectra of star-forming galaxies. Most of the Galactic and extragalactic observations obtained with the James Webb...

The combination of galaxy-galaxy lensing (GGL) and redshift space distortion of galaxy clustering (RSD) is a privileged technique to test general relativity predictions and break degeneracies between the growth rate of structure parameter... more

The combination of galaxy-galaxy lensing (GGL) and redshift space distortion of galaxy clustering (RSD) is a privileged technique to test general relativity predictions and break degeneracies between the growth rate of structure parameter f and the amplitude of the linear power spectrum σ8. We performed a joint GGL and RSD analysis on 250 sq. deg using shape catalogues from CFHTLenS and CFHT-Stripe 82 and spectroscopic redshifts from the BOSS CMASS sample. We adjusted a model that includes non-linear biasing, RSD, and Alcock–Paczynski effects. We used an N-body simulation supplemented by an abundance matching prescription for CMASS galaxies to build a set of overlapping lensing and clustering mocks. Together with additional spectroscopic data, this helps us to quantify and correct several systematic errors, such as photometric redshifts. We find f(z = 0.57) = 0.95 ± 0.23, σ8(z = 0.57) = 0.55 ± 0.07 and Ωm = 0.31 ± 0.08, in agreement with Planck cosmological results 2018. We also est...

Two color (B−V and V−i) CCD photometry of the dominant galaxy (BCG) in five Bautz-Morgan type I clusters has been obtained at the 1.5 m Danish telescope at La Silla. In this paper we analyze their surface brightness and color profiles.... more

Two color (B−V and V−i) CCD photometry of the dominant galaxy (BCG) in five Bautz-Morgan type I clusters has been obtained at the 1.5 m Danish telescope at La Silla. In this paper we analyze their surface brightness and color profiles. All galaxies but one have surface brightness profiles that can be described by a de Vaucouleurs'law with similar effective surface brightness μ e ∼23.2 V mag arcsec −2 and effective radius r e between 30 and 40 kpc. Average colors are alike in all the five galaxies and color gradients are small or absent

Context. The cosmic web, a complex network of galaxy groups and clusters connected by filaments, is a dynamical environment in which galaxies form and evolve. However, the impact of cosmic filaments on the properties of galaxies is... more

Context. The cosmic web, a complex network of galaxy groups and clusters connected by filaments, is a dynamical environment in which galaxies form and evolve. However, the impact of cosmic filaments on the properties of galaxies is difficult to study because of the much more influential local (galaxy-group scale) environment. Aims. The aim of this paper is to investigate the dependence of intrinsic galaxy properties on distance to the nearest cosmic web filament, using a sample of galaxies for which the local environment is easily assessable. Methods. Our study is based on a volume-limited galaxy sample with Mr ≤ −19 mag, drawn from the SDSS DR12. We chose brightest group galaxies (BGGs) in groups with two to six members as our probes of the impact of filamentary environment because their local environment can be determined more accurately. We use the Bisous marked point process method to detect cosmic-web filaments with radii of 0.5−1.0 Mpc and measure the perpendicular filament sp...

In this paper we consider the Universe at the late stage of its evolution and deep inside the cell of uniformity. At these scales, the Universe is filled with inhomogeneously distributed discrete structures (galaxies, groups and clusters... more

In this paper we consider the Universe at the late stage of its evolution and deep inside the cell of uniformity. At these scales, the Universe is filled with inhomogeneously distributed discrete structures (galaxies, groups and clusters of galaxies). Supposing that a small fraction of colored objects escaped hadronization and survived up to now in the form of quark-gluon nuggets (QNs), and also taking into account radiation, we investigate scalar perturbations of the FRW metrics due to inhomogeneities of dustlike matter as well as fluctuations of QNs and radiation. In particular, we demonstrate that the nonrelativistic gravitational potential is defined by the distribution of inhomogeneities/fluctuations of both dustlike matter and QNs. Consequently, QNs can be distributed around the baryonic inhomogeneities (e.g., galaxies) in such a way that it can solve the problem of the flatness of the rotation curves. We also show that the fluctuations of radiation are caused by both the inhomogeneities in the form of galaxies and the fluctuations of quark-gluon nuggets. Therefore, if QNs exist, the CMB anisotropy should contain also the contributions from QNs. Additionally, the spatial distribution of the radiation fluctuations is defined by the gravitational potential. All these results look physically reasonable.

We study the late-time evolution of the Universe where dark energy (DE) is presented by a barotropic fluid on top of cold dark matter (CDM). We also take into account the radiation content of the Universe. Here by the late stage of the... more

We study the late-time evolution of the Universe where dark energy (DE) is presented by a barotropic fluid on top of cold dark matter (CDM). We also take into account the radiation content of the Universe. Here by the late stage of the evolution we refer to the epoch where CDM is already clustered into inhomogeneously distributed discrete structures (galaxies, groups and clusters of galaxies). Under this condition the mechanical approach is an adequate tool to study the Universe deep inside the cell of uniformity. More precisely, we study scalar perturbations of the FLRW metric due to inhomogeneities of CDM as well as fluctuations of radiation and DE. For an arbitrary equation of state for DE we obtain a system of equations for the scalar perturbations within the mechanical approach. First, in the case of a constant DE equation of state parameter www, we demonstrate that our method singles out the cosmological constant as the only viable dark energy candidate. Then, we apply our approach to variable equation of state parameters in the form of three different linear parametrizations of www, e.g., the Chevallier-Polarski-Linder perfect fluid model. We conclude that all these models are incompatible with the theory of scalar perturbations in the late Universe.

We use data from the Sloan Digital Sky Survey and visual classifications of morphology from the Galaxy Zoo project to study black hole growth in the nearby Universe (z < 0.05) and to break down the AGN host galaxy population by color,... more

We use data from the Sloan Digital Sky Survey and visual classifications of morphology from the Galaxy Zoo project to study black hole growth in the nearby Universe (z < 0.05) and to break down the AGN host galaxy population by color, stellar mass and morphology. We find that black hole growth at luminosities L_OIII >1E40 erg/s in early- and late-type galaxies is fundamentally different. AGN host galaxies as a population have a broad range of stellar masses (1E10-1E11 Msun), reside in the green valley of the color-mass diagram and their central black holes have median masses around 1E6.5 Msun. However, by comparing early- and late-type AGN host galaxies to their non-active counterparts, we find several key differences: in early-type galaxies, it is preferentially the galaxies with the least massive black holes that are growing, while late-type galaxies, it is preferentially the most massive}black holes that are growing. The duty cycle of AGN in early-type galaxies is strongly ...

Context. The morphological evolution of star-forming galaxies provides important clues to understand their physical properties, as well as the triggering and quenching mechanisms of star formation. Aims. We analyze the morphology of... more

Context. The morphological evolution of star-forming galaxies provides important clues to understand their physical properties, as well as the triggering and quenching mechanisms of star formation. Aims. We analyze the morphology of galaxies hosting star-forming events at low redshift (z < 0.36). We aim at connecting morphology and star-formation properties of low-mass galaxies (median stellar mass ∼108.5 M⊙) beyond the local Universe. Methods. We use a sample of mediumband selected star-forming galaxies from the GOODS-North field. Hα images for the sample are created combining both spectral energy distribution fits and HST data. Using them, we mask the star forming regions to obtain an unbiased two-dimensional model of the light distribution of the host galaxies. For this purpose we use PHI, a new Bayesian photometric decomposition code. We applied it independently to 7 HST bands, from the ultraviolet to the near-infrared, assuming a Sérsic surface brightness model. Results. St...

The possibility of determining the value of the Hubble constant using observations of galaxy clusters in X-ray and microwave wavelengths through the Sunyaev Zel’dovich (SZ) effect has long been known. Previous measurements have been... more

The possibility of determining the value of the Hubble constant using observations of galaxy clusters in X-ray and microwave wavelengths through the Sunyaev Zel’dovich (SZ) effect has long been known. Previous measurements have been plagued by relatively large errors in the observational data and severe biases induced, for example, by cluster triaxiality and clumpiness. The advent of Planck allows us to map the Compton parameter y, that is, the amplitude of the SZ effect, with unprecedented accuracy at intermediate cluster-centric radii, which in turn allows performing a detailed spatially resolved comparison with X-ray measurements. Given such higher quality observational data, we developed a Bayesian approach that combines informed priors on the physics of the intracluster medium obtained from hydrodynamical simulations of massive clusters with measurement uncertainties. We applied our method to a sample of 61 galaxy clusters with redshifts up to z < 0.5 observed with Planck a...