- ID:
- ivo://CDS.VizieR/J/ApJ/887/203
- Title:
- Core rotation period measurements of KIC stars
- Short Name:
- J/ApJ/887/203
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Stars between two and three solar masses rotate rapidly on the main sequence, and the detection of slow core and surface rotation in the core-helium burning phase for these stars places strong constraints on their angular momentum transport and loss. From a detailed asteroseismic study of the mixed-dipole mode pattern in a carefully selected, representative sample of stars, we find that slow core rotation rates in the range reported by prior studies are a general phenomenon and not a selection effect. We show that the core rotation rates of these stars decline strongly with decreasing surface gravity during the core He-burning phase. We argue that this is a model-independent indication of significant rapid angular momentum transport between the cores and envelopes of these stars. We see a significant range in core rotation rates at all surface gravities, with little evidence for a convergence toward a uniform value. We demonstrate using evolutionary models that measured surface rotation periods are a biased tracer of the true surface rotation distribution, and we argue for using stellar models for interpreting the contrast between core and surface rotation rates. The core rotation rates we measure do not have a strong mass or metallicity dependence. We argue that the emerging data strongly favor a model where angular momentum transport is much more efficient during the core He-burning phase than in the shell-burning phases that precede and follow it.
Number of results to display per page
Search Results
- 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.
- ID:
- ivo://CDS.VizieR/J/ApJ/854/183
- Title:
- Cosmic-ray nucleosynthesis of p-nuclei
- Short Name:
- J/ApJ/854/183
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We investigate the cosmic-ray nucleosynthesis (CRN) of proton-rich stable nuclides (p-nuclides). We calculate the cosmic-ray (CR) energy spectra of heavy nuclides with mass number A=[74,209], taking into account the detailed nuclear spallation, decay, energy loss, and escape from the Galaxy during the CR propagation. We adopt the latest semiempirical formula SPACS (Schmitt+ 2014PhRvC..90f4605S) for the spallation cross sections and the latest data on nuclear decay. Effective electron-capture decay rates are calculated using the proper cross sections for recombination and ionization in the whole CR energy region. Calculated CR spectral shapes vary for different nuclides. Abundances of proton-rich unstable nuclides increase in CRs with increasing energy relative to those of other nuclides. Yields of the primary and secondary spallation processes and differential yields from respective seed nuclides are calculated. We find that the CR energy region of <=O(100)MeV/nucleon predominantly contributes to the total yields. The atomic cross sections in the low-energy range adopted in this study are then necessary. Effects of CRN on the Galactic chemical evolution of p-nuclides are calculated. Important seed nuclides are identified for respective p-nuclides. The contribution of CRN is significant for ^180m^Ta, accounting for about 20% of the solar abundance. About 87% of the ^180m^Ta CRN yield can be attributed to the primary process. The most important production routes are reactions of ^181^Ta, ^180^Hf, and ^182^W. CRN yields of other p-nuclides are typically about O(10^-4^-10^-2^) of solar abundances.
- ID:
- ivo://CDS.VizieR/J/A+A/627/A137
- Title:
- Cosmology from galaxy lensing and clustering
- Short Name:
- J/A+A/627/A137
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- 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 {sigma}8. We perform a joint GGL and RSD analysis on 250 sq. degrees using shape catalogues from CFHTLenS and CFHT-Stripe 82, and spectroscopic redshifts from the BOSS CMASS sample. We adjust a model that includes non-linear biasing, RSD and Alcock-Paczynski effects. We find f(z=0.57)=0.95+/-0.23, {sigma}8(z=0.57)=0.55+/-0.07 and {OMEGA}m=0.31+/-0.08, in agreement with Planck cosmological results 2018. We also estimate the probe of gravity E_G_=0.43+/-0.10 in agreement with {LAMBDA}CDM-GR predictions of E_G_=0.40. This analysis reveals that RSD efficiently decreases the GGL uncertainty on {OMEGA}m by a factor of 4, and by 30% on {sigma}8. We use an N-body simulation supplemented by an abundance matching prescription for CMASS 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 make our mock catalogues available on the Skies and Universe database.
- ID:
- ivo://CDS.VizieR/J/MNRAS/507/5034
- Title:
- COSMOS2015 dataset machine learning photo-z
- Short Name:
- J/MNRAS/507/5034
- Date:
- 03 Dec 2021 13:07:03
- Publisher:
- CDS
- Description:
- In order to answer the open questions of modern cosmology and galaxy evolution theory, robust algorithms for calculating photometric redshifts (photo-z) for very large samples of galaxies are needed. Correct estimation of the various photo-z algorithms' performance requires attention to both the performance metrics and the data used for the estimation. In this work, we use the supervised machine learning algorithm MLPQNA (Multi-Layer Perceptron with Quasi-Newton Algorithm) to calculate photometric redshifts for the galaxies in the COSMOS2015 catalogue and the unsupervised Self-Organizing Maps (SOM) to determine the reliability of the resulting estimates. We find that for z_spec_<1.2, MLPQNA photo-z predictions are on the same level of quality as spectral energy distribution fitting photo-z. We show that the SOM successfully detects unreliable zspec that cause biases in the estimation of the photo-z algorithms' performance. Additionally, we use SOM to select the objects with reliable photo-z predictions. Our cleaning procedures allow us to extract the subset of objects for which the quality of the final photo-z catalogues is improved by a factor of 2, compared to the overall statistics.
- ID:
- ivo://CDS.VizieR/J/ApJS/176/19
- Title:
- COSMOS: strong lens systems
- Short Name:
- J/ApJS/176/19
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the first catalog of 67 strong galaxy-galaxy lens candidates discovered in the 1.64deg^2^ Hubble Space Telescope COSMOS survey. Twenty of these systems display multiple images or strongly curved large arcs. Our initial search is performed by visual inspection of the data and is restricted, for practical considerations, to massive early-type lens galaxies with arcs found at radii smaller than ~5". Simple mass models are constructed for the best lens candidates, and our results are compared to the strong lensing catalogs of the SLACS survey and the CASTLES database. These new strong galaxy-galaxy lensing systems constitute a valuable sample to study the mass distribution of early-type galaxies and their associated dark matter halos.
- ID:
- ivo://CDS.VizieR/J/A+A/566/A95
- Title:
- C-rich giants synthetic spectrophotometry. IV
- Short Name:
- J/A+A/566/A95
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The evolution and spectral properties of stars on the asymptotic giant branch (AGB) are significantly affected by massloss through dusty stellar winds. Dynamic atmosphere and wind models are an essential tool for studying these evolved stars, both individually and as members of stellar populations, to understand their contribution to the integrated light and chemical evolution of galaxies. This paper is part of a series with the purpose of testing state-of-the-art atmosphere and wind models of C-type AGB stars against observations, and making them available to the community for use in various theoretical and observational studies. We have computed low-resolution spectra and photometry (in the wavelength range 0.35-25um) for a grid of 540 dynamic models with stellar parameters typical of solar-metallicity C-rich AGB stars and with a range of pulsation amplitudes. The models cover the dynamic atmosphere and dusty outflow (if present), assuming spherical symmetry, and taking opacities of gas-phase species and dust grains consistently into account. To characterize the time-dependent dynamic and photometric behaviour of the models in a concise way we defined a number of classes for models with and without winds.Results. Comparisons with observed data in general show a quite satisfactory agreement for example regarding mass-loss rates vs. (J-K) colours or K magnitudes vs. (J-K) colours. Some exceptions from the good overall agreement, however, are found and attributed to the range of input parameters (e.g. relatively high carbon excesses) or intrinsic model assumptions (e.g. small particle limit for grain opacities). While current results indicate that some changes in model assumptions and parameter ranges should be made in the future to bring certain synthetic observables into better agreement with observations, it seems unlikely that these pending improvements will significantly affect the mass-loss rates of the models.
- ID:
- ivo://CDS.VizieR/J/A+A/645/A102
- Title:
- Crust structure of neutron stars
- Short Name:
- J/A+A/645/A102
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The thermal evolution of neutron stars in soft X-ray transients (SXTs) is sensitive to the equation of state, nucleon superfluidity, and the composition and structure of the crust. Carrying out comparisons of the observations of their crust cooling with simulations offers a powerful tool for verifying theoretical models of dense matter. We study the effect of physics input on the thermal evolution of neutron stars in SXTs. In particular, we consider different modern models of the sources of deep crustal heating during accretion episodes and the effects brought on by impurities embedded in the crust during its formation. We simulated the thermal structure and evolution of episodically accreting neutron stars under different assumptions regarding the crust composition and on the distribution of heat sources and impurities. For the non-accreted crust, we considered the nuclear charge fluctuations that arise at crust formation. For the accreted crust, we compared different theoretical models of composition and internal heating. We also compared the results of numerical simulations to observations of the crust cooling in SXT MXB 1659-29. The non-accreted part of the inner crust of a neutron star can have a layered structure, with almost pure crystalline layers interchanged with layers composed of mixtures of different nuclei. The latter layers have relatively low thermal conductivities, which has an effect on the thermal evolution of the transients. The impurity distribution in the crust strongly depends on models of the dense matter and the crust formation scenario. The shallow heating that is needed to reach an agreement between the theory and the observations depends on characteristics of the crust and envelope.
- ID:
- ivo://CDS.VizieR/J/MNRAS/425/477
- Title:
- Dark matter annihilation in galaxy clusters
- Short Name:
- J/MNRAS/425/477
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Clusters of galaxies are potentially important targets for indirect searches for dark matter (DM) annihilation. Here we reassess the detection prospects for annihilation in massive haloes, based on a statistical investigation of 1743 clusters in the new Meta-Catalogue of X-ray Clusters (MCXC). We derive a new limit for the extragalactic DM annihilation background of at least 20 per cent of that originating from the Galaxy for an integration angle of 0.1{deg}.
- ID:
- ivo://CDS.VizieR/J/ApJ/733/L51
- Title:
- Dark matter densities in cluster isochrones
- Short Name:
- J/ApJ/733/L51
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In order to characterize how dark matter (DM) annihilation inside stars changes the aspect of a stellar cluster, we computed the evolution until the ignition of the He burning of stars from 0.7M_{sun}_ to 3.5M_{sun}_ within halos of DM with different characteristics. We found that, when a cluster is surrounded by a dense DM halo, the positions of the cluster' stars in the H-R diagram have a brighter and hotter turnoff point than in the classical scenario without DM, therefore giving the cluster a younger appearance. The high DM densities required to produce these effects are expected only in very specific locations, such as near the center of our Galaxy. In particular, if DM is formed by the 8 GeV weakly interacting massive particles recently invoked to reconcile the results from direct detection experiments, then this signature is predicted for halos of DM with a density {rho}_{chi}_=3x10^5^GeV/cm^3^. A DM density gradient inside the stellar cluster would result in a broader main sequence, turnoff, and red giant branch regions. Moreover, we found that for very high DM halo densities the bottom of the isochrones in the H-R diagram rises to higher luminosities, leading to a characteristic signature on the stellar cluster. We argue that this signature could be used to indirectly probe the presence of DM particles in the location of a cluster.
