- ID:
- ivo://CDS.VizieR/J/A+A/547/A33
- Title:
- Chemical reactions for a deuteration network
- Short Name:
- J/A+A/547/A33
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The ground-state rotational ortho-D2H+(1,1,1-0,0,0) transition at 1476.6GHz in the prestellar core 16293E has been searched for with the Herschel/HIFI instrument, within the CHESS (Chemical HErschel Surveys of Star forming regions) Key Program. The line has not been detected at the 21mK.km/s level (3 sigma integrated line intensity). We used the ortho-H2D+ 110-111 transition and para-D2H+ 110-101 transition detected in this source to determine an upper limit on the ortho-to-para D2H+ ratio as well as the para-D2H+/ortho-H2D+ ratio from a non-LTE analysis. We then compared our chemical modeling with the observations in order to estimate the CO depletion as well as the H2 density and kinetic temperature at the position observed. The chemical network is provided in the kida.dat file.
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- ID:
- ivo://CDS.VizieR/J/A+A/341/709
- Title:
- Chemical spiral galaxies models
- Short Name:
- J/A+A/341/709
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have extended our chemical and cosmological galaxy evolution model to calculate the abundance evolution for altogether 16 different elements in spiral galaxies in a chemically consistent way which is a considerable step towards a more realistic galaxy modeling. All observed element abundances in Damped Lyman {alpha} (LDA) systems have been compiled.
- ID:
- ivo://CDS.VizieR/J/A+A/545/A12
- Title:
- Chemistry of IRC+10216 inner wind modelled
- Short Name:
- J/A+A/545/A12
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We model the chemistry of the inner wind of the carbon star IRC+10216 and consider the effects of periodic shocks induced by the stellar pulsation on the gas to follow the non-equilibrium chemistry in the shocked gas layers. We consider a very complete set of chemical families, including hydrocarbons and aromatics, hydrides, halogens, and phosphorous-bearing species. Our derived abundances are compared to those for the latest observational data from large surveys and the Herschel telescope. A semi-analytical formalism based on parameterised fluid equations is used to describe the gas density, velocity, and temperature from 1R to 5R. The chemistry is described using a chemical kinetic network of reactions and a set of stiff, ordinary, coupled differential equations is solved.
- ID:
- ivo://CDS.VizieR/J/ApJS/111/203
- Title:
- Chemo-evolutionary Population Synthesis II.
- Short Name:
- J/ApJS/111/203
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of applying a new chemo-evolutionary stellar population model, developed in a previous paper, to new high-quality observational data of the nuclear regions of two representative elliptical galaxies and the bulge of the Sombrero galaxy. Here we fit in detail ~20 absorption lines and six optical and near-infrared colors, following two approaches: fitting a single-age, single-metallicity model and fitting our full chemical evolutionary model. We find that all the iron lines are weaker than the best-fitting models predict, indicating that the iron abundance is anomalous and deficient. We also find that the Ca I index at 4227 A is much lower than predicted by the models. We can obtain good fits for all the other lines and observed colors with models of old and metal-rich stellar populations and can show that the observed radial gradients are due to metallicity decreasing outward. We find that good fits are obtained both with fully evolutionary models and with single-age, single-metallicity models. This is due to the fact that in the evolutionary model more than 80% of the stars form within 1.5 Gyr after the formation of the galaxies. The fact that slightly better fits are obtained with evolutionary models indicates that these galaxies contain a small spread in metallicity.
- ID:
- ivo://CDS.VizieR/J/other/RNAAS/5.13
- Title:
- CHEOPS limb and gravity-darkening coefficients
- Short Name:
- J/other/RNAAS/5.
- Date:
- 17 Jan 2022 00:43:02
- Publisher:
- CDS
- Description:
- The goal of this Research Note is to provide the theoretical calculations of the limb-darkening coefficients (LDC) and gravity-darkening coefficients (GDC) for the space mission CHEOPS. We use two stellar atmosphere models: ATLAS (plane-parallel) and PHOENIX with spherical symmetry covering a wide range of effective temperatures, local gravities, and hydrogen/metal. These grids cover 19 metallicities ranging from 10^-5^ up to 10^+1^ solar abundances, 0<=logg<=6.0 and 2300K<=Te<=50000K. The specific intensity distribution was fitted using six approaches: linear, quadratic, square root, logarithmic, power-2, and a series with four terms. The calculations of the gravity darkening coefficient were performed for both stellar atmosphere models adopting an improved formulation.
- ID:
- ivo://CDS.VizieR/J/A+A/657/A16
- Title:
- Chromatic variations in microlensing events
- Short Name:
- J/A+A/657/A16
- Date:
- 16 Mar 2022 00:52:23
- Publisher:
- CDS
- Description:
- To a first approximation, the microlensing phenomenon is achromatic and great advancements have been achieved with regard to the interpretation of the achromatic signals, leading to the discovery and characterization of well above 100 new exoplanets. At a higher order accuracy in the observations, microlensing has a chromatic component (a color term) that has thus far been explored to a much lesser extent. Here, we analyze the chromatic microlensing effect of four different physical phenomena, which have the potential to contribute key knowledge of the stellar properties that is not easily achievable with other methods of observation. Our simulation is limited to the case of main-sequence source stars. Microlensing is particularly sensitive to giant and sub-giant stars near the Galactic center. While this population can be studied in short snapshots by the largest telescopes in the world, a general monitoring and characterization of the population can be achieved by use of more accessible medium-sized telescopes with specialized equipment via dual-color monitoring from observatories at sites with excellent seeing. We limit the results of this study to what will be achievable from the Danish 1.54m telescope at La Silla observatory based on the use of the existing dual-color lucky imaging camera. Such potential monitoring programs of the bulge population from medium-sized telescopes include the characterization of starspots, limb-darkening, the frequency of close-in giant planet companions, and gravity darkening for blended source stars. We conclude our simulations with quantifying the likelihood of detecting these different phenomena per object where they are present to be ~60 and ~30% for the above-mentioned phenomena when monitored during both high-magnification and caustic crossings, respectively.
- ID:
- ivo://CDS.VizieR/J/A+A/326/249
- Title:
- Chromospheric models of dwarf M stars
- Short Name:
- J/A+A/326/249
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Tables 4 and 5 give the atmospheric parameters for our models of dM stars Gl 588 and Gl 628. The columns give the column mass in g/cm^-2^, the electron temperature in K, the microturbulent velocity in km/s; the continuum optical depth at 5000{AA}; the hydrogen, proton, and electron density in particles per cm^-3^; and the height h (in km) above the level where tau_5000_=1.
- ID:
- ivo://CDS.VizieR/J/A+A/609/A130
- Title:
- [CII] luminosities of galaxies in G.A.S.+Cloudy
- Short Name:
- J/A+A/609/A130
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Gas is a crucial component of galaxies, providing the fuel to form stars, and it is impossible to understand the evolution of galaxies without knowing their gas properties. The [CII] fine structure transition at 158{mu}m is the dominant cooling line of cool interstellar gas, and is the brightest of emission lines from star forming galaxies from FIR through meter wavelengths, almost unaffected by attenuation. With the advent of ALMA and NOEMA, capable of detecting [CII]-line emission in high-redshift galaxies, there has been a growing interest in using the [CII] line as a probe of the physical conditions of the gas in galaxies, and as a star formation rate (SFR) indicator at z>=4. In this paper, we have used a semi-analytical model of galaxy evolution (G.A.S.) combined with the photoionisation code CLOUDY to predict the [CII] luminosity of a large number of galaxies (25,000 at z~=5) at 4<=z<=8. We assumed that the [CII]-line emission originates from photo-dominated regions. At such high redshift, the CMB represents a strong background and we discuss its effects on the luminosity of the [CII] line. We studied the L[CII]-SFR and L[CII]-Zg relations and show that they do not strongly evolve with redshift from z=4 and to z=8. Galaxies with higher [CII] luminosities tend to have higher metallicities and higher star formation rates but the correlations are very broad, with a scatter of about 0.5 and 0.8dex for L[CII]-SFR and L[CII]-Zg, respectively. Our model reproduces the L[CII]-SFR relations observed in high-redshift star-forming galaxies, with [CII] luminosities lower than expected from local L[CII]-SFR relations. Accordingly, the local observed L[CII]-SFR relation does not apply at high-z (z~=5), even when CMB effects are ignored. Our model naturally produces the [CII] deficit (i.e. the decrease of L[CII]/LIR with LIR), which appears to be strongly correlated with the intensity of the radiation field in our simulated galaxies. We then predict the [CII] luminosity function, and show that it has a power law form in the range of L[CII] probed by the model with a slope {alpha}=-1. The slope is not evolving from z=4 to z=8 but the number density of [CII]-emitters decreases by a factor of 20x. We discuss our predictions in the context of current observational estimates on both the differential and cumulative luminosity functions. The outputs from the model are distributed as FITS-formatted files at the CDS.
- ID:
- ivo://CDS.VizieR/J/ApJ/689/461
- Title:
- Circumstellar disk of {chi} Oph
- Short Name:
- J/ApJ/689/461
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a numerical model describing a circularly symmetric gaseous disk around the Be star {chi} Ophiuchi. The model is constrained by long-baseline interferometric observations that are sensitive to the H{alpha} Balmer line emission from the disk. For the first time, our interferometric observations spatially resolve the inner region of the circumstellar disk around {chi} Oph, and we use these results to place a constraint on the physical extent of the H{alpha}-emitting region. We demonstrate how this in turn results in very specific constraints on the parameters that describe the variation of the gas density as a function of radial distance from the central star.
- ID:
- ivo://CDS.VizieR/J/ApJ/887/134
- Title:
- Classification of Fermi blazar cand. from the 4FGL
- Short Name:
- J/ApJ/887/134
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The recently published fourth Fermi Large Area Telescope source catalog (4FGL) reports 5065 gamma-ray sources in terms of direct observational gamma-ray properties. Among the sources, the largest population is the active galactic nuclei (AGNs), which consists of 3137 blazars, 42 radio galaxies, and 28 other AGNs. The blazar sample comprises 694 flat-spectrum radio quasars (FSRQs), 1131 BL Lac-type objects (BL Lacs), and 1312 blazar candidates of an unknown type (BCUs). The classification of blazars is difficult using optical spectroscopy given the limited knowledge with respect to their intrinsic properties, and the limited availability of astronomical observations. To overcome these challenges, machine-learning algorithms are being investigated as alternative approaches. Using the 4FGL catalog, a sample of 3137 Fermi blazars with 23 parameters is systematically selected. Three established supervised machine-learning algorithms (random forests (RFs), support vector machines (SVMs), artificial neural networks (ANNs)) are employed to general predictive models to classify the BCUs. We analyze the results for all of the different combinations of parameters. Interestingly, a previously reported trend the use of more parameters leading to higher accuracy is not found. Considering the least number of parameters used, combinations of eight, 12 or 10 parameters in the SVM, ANN, or RF generated models achieve the highest accuracy (Accuracy ~91.8%, or ~92.9%). Using the combined classification results from the optimal combinations of parameters, 724 BL Lac type candidates and 332 FSRQ type candidates are predicted; however, 256 remain without a clear prediction.
