- ID:
- ivo://CDS.VizieR/J/ApJS/194/15
- Title:
- CCCP: Carina's diffuse X-ray emission
- Short Name:
- J/ApJS/194/15
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a 1.42deg^2^ mosaic of diffuse X-ray emission in the Great Nebula in Carina from the Chandra X-ray Observatory Advanced CCD Imaging Spectrometer camera. After removing >14000 X-ray point sources from the field, we smooth the remaining unresolved emission, tessellate it into segments of similar apparent surface brightness, and perform X-ray spectral fitting on those tessellates to infer the intrinsic properties of the X-ray-emitting plasma. By modeling faint resolved point sources, we estimate the contribution to the extended X-ray emission from unresolved point sources and show that the vast majority of Carina's unresolved X-ray emission is truly diffuse. Line-like correlated residuals in the X-ray spectral fits suggest that substantial X-ray emission is generated by charge exchange at the interfaces between Carina's hot, rarefied plasma and its many cold neutral pillars, ridges, and clumps.
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- ID:
- ivo://CDS.VizieR/J/A+A/636/A45
- Title:
- CEGM03 model and related gravity anomaly data
- Short Name:
- J/A+A/636/A45
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Chinese lunar missions have grown in number over the last ten years, with an increasing focus on radio science investigations. In previous work, we estimated two lunar gravity field models, CEGM01 and CEGM02. The recently lunar mission, Chang'e 5T1, which had an orbital inclination between 18 and 68 degree, and collected orbital tracking data continually for two years, made an improved gravity field model possible. We aimed to estimate a new lunar gravity field model up to degree and order 100, CEGM03, and a new tidal Love number based on the Chang'e 5T1 tracking data combined with the historical tracking data ever used in the solution of CEGM02. The new model makes use of tracking data with this particular inclination, which has not been used in previous gravity field modeling. The solution for this new model was based on our in-house software, LUGREAS. The gravity spectrum power, postfit residuals after precision orbit determination (POD), lunar surface gravity anomalies, correlations between parameters, admittance/coherence with topography model, and accuracy of POD were analyzed to validate the new CEGM03 model. We analyzed the tracking data of the Chang'e 5T1 mission and estimated the CEGM03 lunar gravity field model. We found that the two-way Doppler measurement accuracy reached the 0.2 mm/s with 10 s integration time. The error spectrum shows that the formal error for CEGM03 was at least reduced by about 2 times below the harmonic degree of 20, when compared to the CEGM02 model. The gravity and topography admittance/correlation was also improved when compared to the correlations for the CEGM02 model. The lunar potential Love number k2 was estimated to be 0.02430+/-0.0001 (ten times the formal error). From the model analysis and comparison of the various models, we identified improvements in the CEGM03 model after introducing Chang'e 5T1 tracking data. Moreover, this study illustrates how the low and middle inclination orbits could contribute better accuracy for a low degree of lunar gravity field.
- ID:
- ivo://CDS.VizieR/J/A+A/586/A87
- Title:
- Center-to-limb polarization of FGK stars
- Short Name:
- J/A+A/586/A87
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- One of the necessary parameters needed for the interpretation of the light curves of transiting exoplanets or eclipsing binary stars (as well as interferometric measurements of a star or microlensing events) is how the intensity and polarization of light changes from the center to the limb of a star. Scattering and absorption processes in the stellar atmosphere affect both the center-to-limb variation of intensity (CLVI) and polarization (CLVP). In this paper, we present a study of the CLVI and CLVP in continuum spectra, taking into consideration the different contributions of scattering and absorption opacity for a variety of spectral type stars with spherical atmospheres. We solve the radiative transfer equation for polarized light in the presence of a continuum scattering, taking into consideration the spherical model of a stellar atmosphere. To cross-check our results, we developed two independent codes that are based on Feautrier and short characteristics methods, respectively, We calculate the center-to-limb variation of intensity (CLVI) and polarization (CLVP) in continuum for the Phoenix grid of spherical stellar model atmospheres for a range of effective temperatures (4000-7000K), gravities (logg=1.0-5.5), and wavelengths (4000-7000{AA}). In addition, we present several tests of our codes and compare our calculations for the solar atmosphere with published photometric and polarimetric measurements. We also show that our two codes provide similar results in all considered cases.
- ID:
- ivo://CDS.VizieR/J/A+A/575/A89
- Title:
- Center-to-limb polarization of FGK stars
- Short Name:
- J/A+A/575/A89
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Scattering and absorption processes in stellar atmosphere act the center-to-limb variations of the intensity (CLVI) and the linear polarization (CLVP) of stellar radiation. There are several theoretical and observational studies of CLVI using different stellar models, however, most studies of CLVP have concentrated on the solar atmosphere and have not considered the CLVP in cooler non-gray stellar atmospheres at all. In this paper, we present a theoretical study of the CLV of the intensity and the linear polarization in continuum spectra of different spectral type stars. We solve the radiative transfer equations for polarized light iteratively assuming no magnetic field and considering a planeparallel model atmospheres and various opacities.
- ID:
- ivo://CDS.VizieR/J/A+A/646/A71
- Title:
- CFHTLenS galaxy bias and redshift distribution
- Short Name:
- J/A+A/646/A71
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Galaxy models predict a tight relation between the clustering of galaxies and dark matter on cosmological scales, but predictions differ notably in the details. We used this opportunity and tested two semi-analytic models by the Munich and Durham groups with data from the Canada-France-Hawaii Telescope Lensing Survey (CFHTLenS). For the test we measured the scale-dependent galaxy bias factor b(k) and correlation factor r(k) from linear to non-linear scales of k=~10h/Mpc at two redshifts z{bar}=0.35, 0.51 for galaxies with stellar mass between 5x10^9^ and 3x10^11^h_70_^-2^M_{sun|_. Our improved gravitational lensing technique accounts for the intrinsic alignment of sources and the magnification of lens galaxies for better constraints for the galaxy-matter correlation r(k). Galaxy bias in CFHTLenS increases with k and stellar mass; it is colour-dependent, revealing the individual footprints of galaxy types. Despite a reasonable model agreement for the relative change with both scale and galaxy properties, there is a clear conflict for b(k) with no model preference: the model galaxies are too weakly clustered. This may flag a model problem at z>~0.3 for all stellar masses. As in the models, however, there is a high correlation r(k) between matter and galaxy density on all scales, and galaxy bias is typically consistent with a deterministic bias on linear scales. Only our blue and low-mass galaxies of about 7x10^9^h_70_^-2^M_{sun}_ at z{bar}=0.51 show, contrary to the models, a weak tendency towards a stochastic bias on linear scales where rls=0.75+/-0.14(stat.)+/-0.06(sys.). This result is of interest for cosmological probes, such as EG, that rely on a deterministic galaxy bias. We provide Monte Carlo realisations of posterior constraints for b(k) and r(k) in CFHTLenS for every galaxy sample in this paper at the CDS.
- ID:
- ivo://CDS.VizieR/J/ApJ/735/26
- Title:
- Chandra observations of M81
- Short Name:
- J/ApJ/735/26
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present an analysis of 15 Chandra observations of the nearby spiral galaxy M81 taken over the course of six weeks in 2005 May-July. Each observation reaches a sensitivity of ~10^37^erg/s. With these observations and one previous deeper Chandra observation, we compile a master source list of 265 point sources, extract and fit their spectra, and differentiate basic populations of sources through their colors. We also carry out variability analyses of individual point sources and of X-ray luminosity functions (XLFs) in multiple regions of M81 on timescales of days, months, and years. We find that, despite measuring significant variability in a considerable fraction of sources, snapshot observations provide a consistent determination of the XLF of M81. We also fit the XLFs for multiple regions of M81 and, using common parameterizations, compare these luminosity functions to those of two other spiral galaxies, M31 and the Milky Way.
- ID:
- ivo://CDS.VizieR/J/A+A/654/A156
- Title:
- Chaotic diffusion of fundamental frequencies
- Short Name:
- J/A+A/654/A156
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- The long-term variations of the orbit of the Earth govern the insolation on its surface and hence its climate. The use of the astronomical signal, whose imprint has been recovered in the geological records, has revolutionized the determination of the geological time scales (e.g. Gradstein & Ogg, 2020, in Geologic Time Scale (Amsterdam: Elsevier), 21). However, the orbital variations beyond 60Myr cannot be reliably predicted because of the A,chaotic dynamics of the planetary orbits in the Solar System (Laskar, 1989Natur.338..237L). Taking into account this dynamical uncertainty is necessary for a complete astronomical calibration of geological records. Our work addresses this problem with a statistical analysis on 120000 orbital solutions of the secular model of the Solar System ranging from 500Myr to 5Gyr. We obtain the marginal probability density functions of the fundamental secular frequencies using kernel density estimation. The uncertainty of the density estimation is also obtained here in the form of confidence intervals determined by the moving block bootstrap method. The results of the secular model are shown to be in good agreement with those of the direct integrations of a comprehensive model of the Solar System. Applicationof our work is illustrated on two geological data: the Newark-Hartford
- ID:
- ivo://CDS.VizieR/J/ApJ/764/18
- Title:
- Characteristic frequencies of giant exoplanets
- Short Name:
- J/ApJ/764/18
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We calculate the eigenfrequencies and eigenfunctions of the acoustic oscillations of giant exoplanets and explore the dependence of the characteristic frequency {nu}_0_ and the eigenfrequencies on several parameters: the planet mass, the planet radius, the core mass, and the heavy element mass fraction in the envelope. We provide the eigenvalues for degree l up to 8 and radial order n up to 12. For the selected values of l and n, we find that the pulsation eigenfrequencies depend strongly on the planet mass and radius, especially at high frequency. We quantify this dependence through the calculation of the characteristic frequency {nu}_0_ which gives us an estimate of the scale of the eigenvalue spectrum at high frequency. For the mass range 0.5M_J_<=M_P_<=15M_J_, and fixing the planet radius to the Jovian value, we find that {nu}_0_~164.0x(M_P_/M_J_)^0.48^{mu}Hz, where M_P_ is the planet mass and M_J_ is Jupiter's mass. For the radius range from 0.9 to 2.0R_J_, and fixing the planet's mass to the Jovian value, we find that {nu}_0_~164.0x(R_P_/R_J_)^-2.09^{mu}Hz, where R_P_ is the planet radius and R_J_ is Jupiter's radius. We explore the influence of the presence of a dense core on the pulsation frequencies and on the characteristic frequency of giant exoplanets. We find that the presence of heavy elements in the envelope affects the eigenvalue distribution in ways similar to the presence of a dense core. Additionally, we apply our formalism to Jupiter and Saturn and find results consistent with both the observational data of Gaulme et al. (2011A&A...531A.104G) and previous theoretical work.
- ID:
- ivo://CDS.VizieR/J/ApJ/812/142
- Title:
- Chemical evolution in the LMC with a new model
- Short Name:
- J/ApJ/812/142
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using a new network and a new model, we have studied chemical complexity in cold portions of dense clouds of the Large Magellanic Cloud (LMC). We varied the hydrogen number density between 1x10^5^ and 5x10^5^/cm3 and, for each density, we ran models for A_V_=3, 5, and 10. Then, for each density and visual extinction we varied the grain temperature between 10 and 50K in small intervals, while keeping the gas temperature constant at 20K. We used a gas-to-dust mass ratio based on a variety of observations and analyses, and scaled the elemental abundances of the LMC so that they are representative of so-called "low" metallic abundances. We found that although the LMC is metal-poor, it still shows a rich chemistry; almost all the major observed species in the gas phase of our Galaxy should be detectable using present-day observational facilities. We compared our model results with observed gas-phase abundances in some cold and dense sources, and found reasonably good agreement for most species. We also found that some observed results, especially for methanol, are better matched if these regions currently possess lower temperatures, or possessed them in the past. Finally, we discussed our simulated abundances for H_2_O ice with respect to total hydrogen, and CO_2_, CO, CH_3_OH, and NH_3_ ices with respect to water ice, and compared our values with those for two observed ices --CO_2_ and CO-- detected in front of young stellar objects in the LMC.
- ID:
- ivo://CDS.VizieR/J/ApJ/822/105
- Title:
- Chemical evolution in the SMC
- Short Name:
- J/ApJ/822/105
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Large (LMC) and Small (SMC) Magellanic Clouds are irregular satellite galaxies of the Milky Way. Both are metal- and dust-poor, although the SMC is significantly poorer in both. We have recently simulated the chemistry in cold dense regions of the LMC and found that a rich chemistry exists in the gas-phase. In this paper, we report a companion study of the chemistry of dense regions of the SMC, confining our attention to cold regions of dense clouds with a variety of densities, visual extinctions, and grain temperatures, and a fixed gas-phase temperature. With a gas-to-dust ratio and elemental abundances based on observations and scaling, we found that for molecules like CO and N_2_, which are predominantly formed in the gas phase, their abundances are consistent with the reduced elemental abundances of their constituent elements above 25K; however, for species that are produced fully (e.g., CH_3_OH) or partially on the grain surface (e.g., H_2_CO, NH_3_), the dependence on metallicity can be complex. Most of the major gas-phase species observed in our Galaxy are produced in the SMC although in lower quantities. With our simulations, we are able to explain observed gas-phase abundances reasonably well in the dense sources N27 and LIRS 36. We have also compared our calculated abundances of selected ices with limited observations in dense regions in front of young stellar objects.
