- ID:
- ivo://CDS.VizieR/J/AJ/117/981
- Title:
- Estimation of stellar metal abundance. II.
- Short Name:
- J/AJ/117/981
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have recalibrated a method for the estimation of stellar metal abundance, parameterized as [Fe/H], based on medium-resolution (1-2{AA}) optical spectra (the majority of which cover the wavelength range 3700-4500{AA}). The equivalent width of the Ca II K line (3933{AA}) as a function of [Fe/H] and broadband B-V color, as predicted from spectrum synthesis and model atmosphere calculations, is compared with observations of 551 stars with high-resolution abundances available from the literature (a sevenfold increase in the number of calibration stars that were previously available). A second method, based on the Fourier autocorrelation function technique first described by Ratnatunga & Freeman (1989, Cat. <V/65>), is used to provide an independent estimate of [Fe/H], as calibrated by comparison with 405 standard-star abundances.
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- ID:
- ivo://CDS.VizieR/J/ApJ/810/138
- Title:
- ETGs sample for the Coma cluster
- Short Name:
- J/ApJ/810/138
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We explore the properties of early-type galaxies (ETGs), including ellipticals (E) and lenticulars (S0), in rich environments, such as clusters of galaxies (Virgo and Coma). The L_24_/L_K_ distribution of ETGs in both Virgo and Coma clusters shows that some S0s have a much larger L_24_/L_K_ ratio (0.5 to ~2 dex) than the bulk of the ETG population. This could be interpreted as an enhanced star formation rate in these lenticulars. We compare the optical colors of galaxies in these two clusters and investigate the nature of these sources with a large L_24_/L_K_ ratio by looking at their spatial distribution within the cluster, analyzing their optical spectra, and looking at their optical colors compared to late-types. We obtain 10 Coma and 3 Virgo early-type sources with larger L_24_/L_K_ ratios than the bulk of their population. We call these sources mid-infrared enhanced galaxies (MIEGs). In Coma, they are mostly located in the southwest part of the cluster where a substructure is falling onto the main cluster. MIEGs present a lower g-r color than the rest of the ETG sample because of a blue continuum. We interpret the excess L_24_/L_K_ ratio as evidence for enhanced star formation induced as a consequence of their infall into the main cluster.
- ID:
- ivo://CDS.VizieR/J/ApJS/256/9
- Title:
- Euclid preparation. XIV. C3R2 survey DR3
- Short Name:
- J/ApJS/256/9
- Date:
- 18 Jan 2022 14:01:22
- Publisher:
- CDS
- Description:
- The Complete Calibration of the Color-Redshift Relation (C3R2) survey is obtaining spectroscopic redshifts in order to map the relation between galaxy color and redshift to a depth of i~24.5 (AB). The primary goal is to enable sufficiently accurate photometric redshifts for Stage IV dark energy projects, particularly Euclid and the Nancy Grace Roman Space Telescope (Roman), which are designed to constrain cosmological parameters through weak lensing. We present 676 new high-confidence spectroscopic redshifts obtained by the C3R2 survey in the 2017B-2019B semesters using the DEIMOS, LRIS, and MOSFIRE multiobject spectrographs on the Keck telescopes. Combined with the 4454 redshifts previously published by this project, the C3R2 survey has now obtained and published 5130 high-quality galaxy spectra and redshifts. If we restrict consideration to only the 0.2<z_p_<2.6 range of interest for the Euclid cosmological goals, then with the current data release, C3R2 has increased the spectroscopic redshift coverage of the Euclid color space from 51% (as reported by Masters+ 2017, J/ApJ/841/111) to the current 91%. Once completed and combined with extensive data collected by other spectroscopic surveys, C3R2 should provide the spectroscopic calibration set needed to enable photometric redshifts to meet the cosmology requirements for Euclid, and make significant headway toward solving the problem for Roman.
- ID:
- ivo://CDS.VizieR/J/ApJ/885/100
- Title:
- Evolu. star mass-metallicity relation. II.
- Short Name:
- J/ApJ/885/100
- Date:
- 16 Mar 2022 11:50:55
- Publisher:
- CDS
- Description:
- We present the stellar mass-[Fe/H] and mass-[Mg/H] relation of quiescent galaxies in two galaxy clusters at z~0.39 and z~0.54. We derive the age, [Fe/H], and [Mg/Fe] for each individual galaxy using a full-spectrum fitting technique. By comparing with the relations for z~0 Sloan Digital Sky Survey galaxies, we confirm our previous finding that the mass-[Fe/H] relation evolves with redshift. The mass-[Fe/H] relation at higher redshift has lower normalization and possibly steeper slope. However, based on our sample, the mass-[Mg/H] relation does not evolve over the observed redshift range. We use a simple analytic chemical evolution model to constrain the average outflow that these galaxies experience over their lifetime, via the calculation of mass-loading factor. We find that the average mass-loading factor {eta} is a power-law function of galaxy stellar mass, {eta}{prop}M*^-0.21{+/-}0.09^. The measured mass-loading factors are consistent with the results of other observational methods for outflow measurements and with the predictions where outflow is caused by star formation feedback in turbulent disks.
- ID:
- ivo://CDS.VizieR/J/A+A/623/A85
- Title:
- Evolutionary models of cold and low-mass planets
- Short Name:
- J/A+A/623/A85
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Future instruments like the Near Infrared Camera (NIRCam) and the Mid Infrared Instrument (MIRI) on the James Webb Space Telescope (JWST) or the Mid-Infrared E-ELT Imager and Spectrograph (METIS) at the European Extremely Large Telescope (E-ELT) will be able to image exoplanets that are too faint (because they have a low mass, and hence a small size or low effective temperature) for current direct imaging instruments. On the theoretical side, core accretion formation models predict a significant population of low-mass and/or cool planets at orbital distances of ~10-100au. Evolutionary models predicting the planetary intrinsic luminosity as a function of time have traditionally concentrated on gas-dominated giant planets. We extend these cooling curves to Saturnian and Neptunian planets. We simulated the cooling of isolated core-dominated and gas giant planets with masses of 5M_{earth}_ to 2M_{jup}_. The planets consist of a core made of iron, silicates, and ices surrounded by a H/He envelope, similar to the ice giants in the solar system. The luminosity includes the contribution from the cooling and contraction of the core and of the H/He envelope, as well as radiogenic decay. For the atmosphere we used grey, AMES-Cond, petitCODE, and HELIOS models. We considered solar and non-solar metallicities as well as cloud-free and cloudy atmospheres. The most important initial conditions, namely the core-to-envelope ratio and the initial (i.e. post formation) luminosity are taken from planet formation simulations based on the core accretion paradigm. We first compare our cooling curves for Uranus, Neptune, Jupiter, Saturn, GJ 436b, and a 5M_{earth}_ planet with a 1% H/He envelope with other evolutionary models. We then present the temporal evolution of planets with masses between 5M_{earth}_ and 2M_{jup}_ in terms of their luminosity, effective temperature, radius, and entropy. We discuss the impact of different post formation entropies. For the different atmosphere types and initial conditions, magnitudes in various filter bands between 0.9 and 30 micrometer wavelength are provided. Using blackbody fluxes and non-grey spectra, we estimate the detectability of such planets with JWST. We found that a 20(100)M_{earth}_ planet can be detected with JWST in the background limit up to an age of about 10(100)Myr with NIRCam and MIRI, respectively.
- ID:
- ivo://CDS.VizieR/J/A+A/361/1023
- Title:
- Evolution models for {alpha}-enhanced stars
- Short Name:
- J/A+A/361/1023
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present four large sets of evolutionary tracks for stars with initial chemical compositions [Y=0.250, Z=0.008], [Y=0.2773, Z=0.019], [Y=0.320, Z=0.040] and [Y=0.390, Z=0.070] and enhancement of {alpha} elements with respect to the solar pattern. The major improvement with respect to previous similar calculations is that we use consistent opacities - i.e. computed with the same chemical composition as adopted in the stellar models - over the whole relevant range of temperatures. For the same initial chemical compositions [Y, Z] and otherwise identical input physics we present also new evolutionary sequences with solar-scaled mixtures of abundances. Based on these stellar models we calculate the corresponding sets of isochrones both in the Johnson-Cousins UBVRIJHK and HST/WFPC2 photometric systems. Furthermore, we derive integrated magnitudes, colours and mass-to-light ratios for ideal single stellar populations with total mass equal to 1M_{sun}_ Finally, the major changes in the tracks, isochrones, and integrated magnitudes and colours passing from solar-scaled to {alpha}-enhanced mixtures are briefly outlined. Retrieval of the complete data set is possible via the www page http://pleiadi.pd.astro.it .
- ID:
- ivo://CDS.VizieR/J/A+A/311/361
- Title:
- Evolution models of elliptical galaxies. II.
- Short Name:
- J/A+A/311/361
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In this paper we present new chemo-spectro-photometric models of elliptical galaxies in which infall of primordial gas is allowed to occur. They aim to simulate the collapse of a galaxy made of two components, i.e. luminous material and dark matter. The mass of the dark component is assumed to be constant in time, whereas that of the luminous material is supposed to accrete at a suitable rate. They also include the effect of galactic winds powered by supernova explosions and stellar winds from massive, early-type stars. The models are constrained to match a number of properties of elliptical galaxies, i.e. the slope and mean colours of the colour-magnitude relation (CMR), V versus (V-K), the UV excess as measured by the colour (1550-V) together with the overall shape of the integrated spectral energy distribution (ISED) in the ultraviolet, the relation between the Mg_2_ index and (1550-V), the mass to blue luminosity ratio M/L_B_ as a function of the B luminosity, and finally the broad-band colours (U-B), (B-V), (V-I), (V-K), etc. The CMR is interpreted as a mass-metallicity sequence of old, nearly coeval objects, whose mean age is 15Gyr. Assuming the law of star formation to be proportional to M_g_^k^(t) with k=1, the rate of star formation as function of time starts small, grows to a maximum, and then declines thus easily avoiding the excess of metal-poor stars found by BCF with the closed-box scheme (the analog of the G-Dwarf Problem in the solar vicinity). Owing to their stellar content, infall models can easily reproduce all the basic data of the galaxies under examination. As far as the UV excess is concerned, the same sources proposed by BCF are found to hold also with the infall scheme. H-HB and AGB manque stars of high metallicity play the dominant role, and provide a robust explanation of the correlation between the (1550-V) colour and the luminosity, mass and metallicity of the galaxies. Furthermore, these models confirm the potential of the (1550-V) colour as an age indicator in cosmology as already suggested by BCF. In the rest frame of a massive and metal-rich elliptical galaxy, this colour suffers from one major variation: at the onset of the so-called H-HB and AGB-manque stars (age about 5.6Gyr). This transition occurs at reasonably small red-shifts and therefore could be detected with the present-day instrumentation.
- ID:
- ivo://CDS.VizieR/J/A+A/335/823
- Title:
- Evolution models of elliptical galaxies. III.
- Short Name:
- J/A+A/335/823
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In this study we present a simple model of elliptical galaxies aimed at interpreting the gradients in colours and narrow band indices observed across these systems. Salient features of the model are the gradients in mass density and star formation and infall of primordial gas aimed at simulating the collapse of a galaxy into the potential well of dark matter. Adopting a multi-zone model we follow in detail the history of star formation, gas consumption, and chemical enrichment of the galaxy and also allow for the occurrence of galactic winds according to the classical supernova (and stellar winds) energy deposit. The outline of the model, the time scale of gas accretion and rate of star formation as a function of the galacto-centric distance in particular, seek to closely mimic the results from Tree-SPH dynamical models. Although some specific ingredients of the model can be questioned from many points of view (of which we are well aware), the model has to be considered as a gross tool for exploring the consequences of different recipes of gas accretion and star formation in which the simple one-zone scheme is abandoned. With the aid of this model we discuss the observational data on the gradients in metallicity, colours, and narrow band indices across elliptical galaxies.
- ID:
- ivo://CDS.VizieR/J/A+A/624/A8
- Title:
- Evolved Galactic open clusters dynamical properties
- Short Name:
- J/A+A/624/A8
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The stellar content of Galactic open clusters (OCs) is gradually depleted during their evolution as a result of internal relaxation and external interactions. The final residues of the long-term evolution of OCs are called open cluster remnants (OCRs).These are sparsely populated structures that can barely be distinguished from the field. We aimed to characterise and compare the dynamical states of a set of 16 objects catalogued as OCRs or OCR candidates. The sample also includes 7 objects that are catalogued as dynamically evolved OCs for comparison purposes. We used photometric data from the 2MASS catalogue, proper motions and parallaxes from the GAIA DR2 catalogue, and a decontamination algorithm that was applied to the three-dimensional astrometric space of proper motions and parallaxes ({mu}_{alpha}, {mu}_{delta}, {varpi}) for stars in the objects' areas. The investigated OCRs present masses (M) and velocity dispersions ({sigma}_v_) within well-defined ranges: M between ~10-40M_{sun} and {sigma}_v_ between ~1-7km/s. Some objects in the remnant sample have a limiting radius R_lim_<~2pc, which means that they are more compact than the investigated OCs; other remnants have R_lim_ between ~2-7pc, which is comparable to the OCs. In general, our clusters show signals of depletion of low-mass stars. This confirms their dynamically evolved states. Using results from N-body simulations, we conclude that the OCRs we studied are in fact remnants of initially very populous OCs (N_0_~10^3^-10^4^stars). The outcome of the long-term evolution is to bring the final residues of the OCs to dynamical states that are similar to each other, thus masking out the memory of the initial formation conditions of star clusters.
- ID:
- ivo://CDS.VizieR/J/ApJ/902/24
- Title:
- Evolved massive stars with TESS. II.
- Short Name:
- J/ApJ/902/24
- Date:
- 14 Mar 2022 07:45:17
- Publisher:
- CDS
- Description:
- Massive stars briefly pass through the yellow supergiant (YSG) phase as they evolve redward across the H-R diagram and expand into red supergiants (RSGs). Higher-mass stars pass through the YSG phase again as they evolve blueward after experiencing significant RSG mass loss. These post-RSG objects offer us a tantalizing glimpse into which stars end their lives as RSGs and why. One telltale sign of a post-RSG object may be an instability to pulsations, depending on the star's interior structure. Here we report the discovery of five YSGs with pulsation periods faster than 1 day, found in a sample of 76 cool supergiants observed by the Transiting Exoplanet Survey Satellite (TESS) at a two-minute cadence. These pulsating YSGs are concentrated in an H-R diagram region not previously associated with pulsations; we conclude that this is a genuine new class of pulsating star, fast yellow pulsating supergiants (FYPSs). For each FYPS, we extract frequencies via iterative prewhitening and conduct a time-frequency analysis. One FYPS has an extracted frequency that is split into a triplet, and the amplitude of that peak is modulated on the same timescale as the frequency spacing of the triplet; neither rotation nor binary effects are likely culprits. We discuss the evolutionary status of FYPS and conclude that they are candidate post-RSGs. All stars in our sample also show the same stochastic low-frequency variability found in hot OB stars and attributed to internal gravity waves. Finally, we find four {alpha} Cygni variables in our sample, of which three are newly discovered.
