- ID:
- ivo://CDS.VizieR/J/ApJS/100/281
- Title:
- Cosmic background anisotropies
- Short Name:
- J/ApJS/100/281
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Cosmic microwave background (CMB) anisotropies and density fluctuations are calculated for flat cold dark matter (CDM) models with a wide range of parameters, viz., {OMEGA}_0,h_, and {OMEGA}_B_, for standard recombination and for various epochs of reionization. Tables of the power spectrum of CMB anisotropies in the form of C_l_ values as a function of l are presented. Although the Harrison-Zeldovich initial spectrum is assumed in these tables, we present simple approximations for obtaining the C_l_ values corresponding to a tilted spectrum from those with a Harrison-Zeldovich spectrum. Values of {sigma}_8_ are derived for the matter density spectrum, with {sigma}(10deg), fixed Q_(rms-PS) and COBE Differential Microwave Radiometer (DMR) 2yr normalizations. Simple modifications of the fitting formula for the density transfer function are given which are applicable for models with high baryon density. By using both numerical results and these fitting formulae, we calculate the relation between {sigma}_8_ and Q_(rms-PS) and find good agreement. In addition, the velocity fields are calculated.
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Search Results
- ID:
- ivo://CDS.VizieR/J/AJ/157/152
- Title:
- Dark spots on Neptune from 25 years of HST images
- Short Name:
- J/AJ/157/152
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We scoured the full set of blue-wavelength Hubble Space Telescope images of Neptune, finding one additional dark spot in new Hubble data beyond those discovered in 1989, 1994, 1996, and 2015. We report the complete disappearance of the SDS-2015 dark spot, using new Hubble data taken on 2018 September 9-10, as part of the Outer Planet Atmospheres Legacy (OPAL) program. Overall, dark spots in the full Hubble data set have lifetimes of at least one to two years, and no more than six years. We modeled a set of dark spots randomly distributed in time over the latitude range on Neptune that is visible from Earth, finding that the cadence of archival Hubble images would have detected about 70% of these spots if their lifetimes are only one year, or about 85%-95% of simulated spots with lifetimes of two or more years. Based on the Hubble data set, we conclude that dark spots have average occurrence rates of one dark spot every four to six years. Many numerical models to date have simulated much shorter vortex lifetimes, so our findings provide constraints that may lead to improved understanding of Neptune's wind field, stratification, and humidity.
- ID:
- ivo://CDS.VizieR/J/A+A/547/A105
- Title:
- D-burning in core accretion objects
- Short Name:
- J/A+A/547/A105
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Our aim is to study deuterium burning in objects forming according to the core accretion scenario in the hot and cold start assumption and what minimum deuterium burning mass limit is found for these objects. We also study how the burning process influences the structure and luminosity of the objects. Furthermore we want to test and verify our results by comparing them to already existing hot start simulations which did not consider, however, the formation process.
- ID:
- ivo://CDS.VizieR/J/A+A/586/A96
- Title:
- Disk-locking PMS evolutionary tracks
- Short Name:
- J/A+A/586/A96
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Rotational evolution in young stars is described by pre-main sequence evolutionary tracks including non-gray boundary conditions, rotation, conservation of angular momentum, and simulations of disk-locking. By assuming that disk-locking is the regulation mechanism for the stellar angular velocity during the early stages of pre-main sequence evolution, we use our rotating models and observational data to constrain disk lifetimes (Tdisk) of a representative sample of low-mass stars in two young clusters, the Orion Nebula cluster (ONC) and NGC 2264, and to better understand their rotational evolution. The period distributions of the ONC and NGC 2264 are known to be bimodal and to depend on the stellar mass. To follow the rotational evolution of these two clusters' stars, we generated sets of evolutionary tracks from a fully convective configuration with low central temperatures (before D- and Li-burning). We assumed that the evolution of fast rotators can be represented by models considering conservation of angular momentum during all stages and of moderate rotators by models considering conservation of angular velocity during the first stages of evolution. With these models we estimate a mass and an age for all stars.
- ID:
- ivo://CDS.VizieR/J/A+A/357/572
- Title:
- Dust formation in WC stars
- Short Name:
- J/A+A/357/572
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The following table gives the ratefile of the chemical model. Columns {alpha}, {beta} and {gamma} give the rate k at temperature T in the Arrhenius form: k = {alpha} * (T/300)^{beta}^ * exp(-{gamma}/T) The arrows indicate reversible reactions.
- ID:
- ivo://CDS.VizieR/J/ApJ/689/919
- Title:
- Dynamical evolution of globular clusters
- Short Name:
- J/ApJ/689/919
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We test the hypothesis that metal-poor globular clusters form within disk galaxies at redshifts z>3. We calculate the orbits of model clusters in the time-variable gravitational potential of a Milky Way-sized galaxy, using the outputs of a cosmological N-body simulation. We find that at present the orbits are isotropic in the inner 50kpc of the Galaxy and preferentially radial at larger distances. All clusters located outside 10kpc from the center formed in satellite galaxies, some of which are now tidally disrupted and some of which survive as dwarf galaxies. Mergers of the progenitors lead to a spheroidal spatial distribution of model clusters, although it is more extended than that of Galactic metal-poor clusters and has a somewhat shallower power-law slope of the number density profile, {gamma}~2.7. The combination of two-body relaxation, tidal shocks, and stellar evolution drives the evolution of the cluster mass function from an initial power law to a peaked distribution, in agreement with observations. However, not all initial conditions and not all evolution scenarios are consistent with the observed mass function of the Galactic globular clusters. We find that our best-fitting models require the average cluster density, M/R^3^_h_, to be constant initially for clusters of all mass and to remain constant with time. However, these models do not explain the observed decrease of the mean density with galactocentric distance. Both synchronous formation of all clusters at a single epoch (z=4) and continuous formation over a span of 1.6Gyr (between z=9 and 3) are consistent with the data. For both formation scenarios, we provide online catalogs of the main physical properties of model clusters.
- ID:
- ivo://CDS.VizieR/J/A+AS/131/395
- Title:
- Eclipsing binaries light curves models
- Short Name:
- J/A+AS/131/395
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present parameters used in the investigation of the light curves of eclipsing binaries together with other data needed for the interpretation of their stellar and dynamical evolution. Parameters include limb-darkening coefficients and gravity darkening exponents, while data include the apsidal motion constants, the moment of inertia, and the potential energy. The adopted stellar models are those computed by Claret (1995, Cat. <J/A+AS/109/441>) for a representative chemical composition of X=0.70 and Z=0.02. In addition to the parameters needed for the study of the dynamical behavior and tidal evolution of binary systems, we supply the linear limb-darkening coefficients computed in 12 different photometric bands, as well as the gravity darkening exponent for each point along the evolutionary track. We have developed a method, based on the triangles strategy by Kippenhahn et al. 1967 to compute the gravity-darkening exponent using interior models. For the first time, the gravity-darkening exponents are presented as a function of mass and age. The old values of {beta}_1_ (0.32 and 1.0 for convective and radiative envelopes) are thus superseded by the present calculations and a smooth transition is achieved between both energy transport mechanisms. The tables presented here assist modeling of the light curves of close binaries using limb-darkening and gravity darkening coefficients which are consistent with the observed masses, radii and effective temperatures. In order to facilitate the use of the grid of models presented here in a variety of different research fields other than binary stars, synthetic colors (U-B, B-V, u-b, b-y) and M_v_ are also given.
- ID:
- ivo://CDS.VizieR/J/A+A/650/A203
- Title:
- Effects of IMG on Galactic chemical enrichment
- Short Name:
- J/A+A/650/A203
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- We have been seeing mounting evidence that the stellar initial mass function (IMF) might extend far beyond the canonical Mi~100M_{sun}_ limit, but the impact of such a hypothesis on the chemical enrichment of galaxies is yet to be clarified. We aim to address this question by analysing the observed abundances of thin- and thick-disc stars in the Milky Way with chemical evolution models that account for the contribution of very massive stars dying as pair instability supernovae. We built new sets of chemical yields from massive and very massive stars up to Mi~350M_{sun}_ by combining the wind ejecta extracted from our hydrostatic stellar evolution models with explosion ejecta from the literature. Using a simple chemical evolution code, we analysed the effects of adopting different yield tables by comparing predictions against observations of stars in the solar vicinity. After several tests, we set our focus on the [O/Fe] ratio that best separates the chemical patterns of the two Milky Way components. We nd that with a standard IMF, truncated at Mi~100M_{sun}_, we can reproduce various observational constraints for thin-disc stars; however, the same IMF fails to account for the [O/Fe] ratios of thick-disc stars. The best results are obtained by extending the IMF up to Mi=350M_{sun}_; while including the chemical ejecta of very massive stars in the form of winds and pair instability supernova (PISN) explosions. Our study indicates that PISN may have played a significant role in shaping the chemical evolution of the thick disc of the Milky Way. Including their chemical yields makes it easier to reproduce not only the level of the a-enhancement, but also the observed slope of thick-disc stars in the [O/Fe] versus [Fe/H] diagram. The bottom line is that the contribution of very massive stars to the chemical enrichment of galaxies is potentially quite important and should not be neglected in models of chemical evolution.
- ID:
- ivo://CDS.VizieR/J/ApJS/167/177
- Title:
- Emission lines of evolving HII regions
- Short Name:
- J/ApJS/167/177
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We build, as far as theory will permit, self-consistent model HII regions around central clusters of aging stars. These produce strong emission line diagnostics applicable to either individual HII regions in galaxies or to the integrated emission line spectra of disk or starburst galaxies. The models assume that the expansion and internal pressure of individual HII regions is driven by the net input of mechanical energy from the central cluster, be it through winds or supernova events. This eliminates the ionization parameter as a free variable, replacing it with a parameter that depends on the ratio of the cluster mass to the pressure in the surrounding interstellar medium. These models explain why HII regions with low abundances have high excitation and demonstrate that at least part of the warm ionized medium is the result of overlapping faint, old, large, and low-pressure HII regions. We present line ratios (at both optical and IR wavelengths) that provide reliable abundance diagnostics for both single HII regions or for integrated galaxy spectra, and we find a number that can be used to estimate the mean age of the cluster stars exciting individual HII regions.
- ID:
- ivo://CDS.VizieR/J/ApJ/416/276
- Title:
- Eq. of State in Magnetic Neutron Stars
- Short Name:
- J/ApJ/416/276
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This catalog is based on the calculated equation of state in cold dense matter. Each table in the catalog lists bulk properties of Fe-56 in a magnetic field ranging from one million to 1000 million Tesla.
