- ID:
- ivo://CDS.VizieR/J/ApJ/591/138
- Title:
- Chandra X-ray sources of NGC 1068
- Short Name:
- J/ApJ/591/138
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present an analysis of the compact X-ray source population in the Seyfert 2 galaxy NGC 1068, imaged with a 50ks Chandra observation. We find a total of 84 compact sources on the S3 chip, of which 66 are located within the 25.0B-mag/arcsec^2^ isophote of the galactic disk of NGC 1068. Spectra have been obtained for the 21 sources with at least 50 counts and modeled with both multicolor disk blackbody and power-law models.
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- ID:
- ivo://CDS.VizieR/J/ApJ/736/90
- Title:
- Chandra X-ray sources of NGC 1399
- Short Name:
- J/ApJ/736/90
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a wide-field study of the globular cluster (GC)/low-mass X-ray binary (LMXB) connection in the giant elliptical NGC 1399. The large field of view of the Advanced Camera for Surveys/WFC, combined with Hubble Space Telescope and Chandra high resolution, allow us to constrain the LMXB formation scenarios in elliptical galaxies. We confirm that NGC 1399 has the highest LMXB fraction in GCs of all nearby elliptical galaxies studied so far, even though the exact value depends on galactocentric distance due to the interplay of a differential GC versus galaxy light distribution and the GC color dependence. In fact, LMXBs are preferentially hosted by bright, red GCs out to >5R_eff_ of the galaxy light. The finding that GCs hosting LMXBs follow the radial distribution of their parent GC population argues against the hypothesis that the external dynamical influence of the galaxy affects the LMXB formation in GCs. On the other hand, field-LMXBs closely match the host galaxy light, thus indicating that they are originally formed in situ and not inside GCs. We measure GC structural parameters, finding that the LMXB formation likelihood is influenced independently by mass, metallicity, and GC structural parameters. In particular, the GC central density plays a major role in predicting which GCs host accreting binaries. Finally, our analysis shows that LMXBs in GCs are marginally brighter than those in the field, and in particular the only color-confirmed GC with L_X_>10^39^erg/s shows no variability, which may indicate a superposition of multiple LMXBs in these systems.
- ID:
- ivo://CDS.VizieR/J/ApJ/589/225
- Title:
- Chandra X-ray sources toward Galactic Center
- Short Name:
- J/ApJ/589/225
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a catalog of 2357 point sources detected during 590ks of Chandra observations of the 17x17' field around Sgr A*. This field encompasses a physical area of 40x40pc at a distance of 8kpc. The completeness limit of the sample at the Galactic center is 10^31^erg/s (2.0-8.0keV), while the detection limit is an order of magnitude lower. The 281 sources detected below 1.5keV are mainly in the foreground of the Galactic center, while comparisons to the Chandra deep fields at high Galactic latitudes suggest that only about 100 of the observed sources are background AGNs.
- ID:
- ivo://CDS.VizieR/J/A+AS/142/113
- Title:
- C3H2 and SiC2 collisional rates
- Short Name:
- J/A+AS/142/113
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Collisional rate coefficients for rotational transitions in C3H2 and SiC2 due to collisions with H2 molecules are calculated. The C3H2 has two distinct species, ortho and para, whereas the SiC2 has only ortho specie due to spin statistics for the identical carbon nuclei. For ortho- and para-C3H2 we accounted for 47 and 48 energy levels, respectively. The calculations are done for the kinetic temperatures 30, 60, 90, and 120 K. For ortho-SiC2, we accounted for 40 energy levels and the calculations are done for the kinetic temperatures 25, 50, 75, 100, and 125 K. The results are reported here for the transitions in the upward direction. The values for the downward direction can easily be calculated with the help of the detailed equilibrium equation.
- ID:
- ivo://CDS.VizieR/J/ApJ/724/L84
- Title:
- Changes in Titan's atmosphere from Cassini
- Short Name:
- J/ApJ/724/L84
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We use a six-year data set (2004-2010) of mid-infrared spectra measured by Cassini's Composite InfraRed Spectrometer to search for seasonal variations in Titan's atmospheric temperature and composition. During most of Cassini's mission Titan's northern hemisphere has been in winter, with an intense stratospheric polar vortex highly enriched in trace gases, and a single south-to-north circulation cell. Following northern spring equinox in mid-2009, dramatic changes in atmospheric temperature and composition were expected, but until now the temporal coverage of polar latitudes has been too sparse to discern trends. Here, we show that during equinox and post-equinox periods, abundances of trace gases at both poles have begun to increase. We propose that increases in north polar trace gases are due to a seasonal reduction in gas depletion by horizontal mixing across the vortex boundary. A simultaneous south polar abundance increase suggests that Titan is now entering, or is about to enter, a transitional circulation regime with two branches, rather than the single branch circulation pattern previously observed.
- ID:
- ivo://CDS.VizieR/J/AJ/150/81
- Title:
- CHANG-ES. IV. VLA D-configuration observations
- Short Name:
- J/AJ/150/81
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the first part of the observations made for the Continuum Halos in Nearby Galaxies, an EVLA Survey (CHANG-ES) project. The aim of the CHANG-ES project is to study and characterize the nature of radio halos, their prevalence as well as their magnetic fields, and the cosmic rays illuminating these fields. This paper reports observations with the compact D configuration of the Karl G. Jansky Very Large Array (VLA) for the sample of 35 nearby edge-on galaxies of CHANG-ES. With the new wide bandwidth capabilities of the VLA, an unprecedented sensitivity was achieved for all polarization products. The beam resolution is an average of 9.6" and 36" with noise levels reaching approximately 6 and 30{mu}Jy/beam for C- and L-bands, respectively (robust weighting). We present intensity maps in these two frequency bands (C and L), with different weightings, as well as spectral index maps, polarization maps, and new measurements of star formation rates (SFRs). The data products described herein are available to the public in the CHANG-ES data release available at http://www.queensu.ca/changes. We also present evidence of a trend among galaxies with larger halos having higher SFR surface density, and we show, for the first time, a radio continuum image of the median galaxy, taking advantage of the collective signal-to-noise ratio of 30 of our galaxies. This image shows clearly that a "typical" spiral galaxy is surrounded by a halo of magnetic fields and cosmic rays.
- ID:
- ivo://CDS.VizieR/J/ApJ/893/96
- Title:
- CHAOS IV: NGC3184 LBT obs. & 3 other gal. abundances
- Short Name:
- J/ApJ/893/96
- Date:
- 07 Mar 2022 07:28:28
- Publisher:
- CDS
- Description:
- The chemical abundances of spiral galaxies, as probed by HII regions across their disks, are key to understanding the evolution of galaxies over a wide range of environments. We present Large Binocular Telescope/Multi-Object Double Spectrographs spectra of 52 HII regions in NGC 3184 as part of the CHemical Abundances Of Spirals (CHAOS) project. We explore the direct-method gas-phase abundance trends for the first four CHAOS galaxies, using temperature measurements from one or more auroral-line detections in 190 individual HII regions. We find that the dispersion in T_e_-T_e_ relationships is dependent on ionization, as characterized by F_{lambda}5007_/F_{lambda}3727_, and so we recommend ionization-based temperature priorities for abundance calculations. We confirm our previous results that [NII] and [SIII] provide the most robust measures of electron temperature in low-ionization zones, while [OIII] provides reliable electron temperatures in high-ionization nebula. We measure relative and absolute abundances for O, N, S, Ar, and Ne. The four CHAOS galaxies marginally conform with a universal O/H gradient, as found by empirical integral field unit studies when plotted relative to effective radius. However, after adjusting for vertical offsets, we find a tight universal N/O gradient of {alpha}_N/O_=-0.33dex/R_e_ with {sigma}_tot._=0.08 for R_g_/R_e_<2.0, where N is dominated by secondary production. Despite this tight universal N/O gradient, the scatter in the N/O-O/H relationship is significant. Interestingly, the scatter is similar when N/O is plotted relative to O/H or S/H. The observable ionic states of S probe lower ionization and excitation energies than O, which might be more appropriate for characterizing abundances in metal-rich HII regions.
- 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/761/57
- Title:
- CHARA array angular diameters of HR 8799
- Short Name:
- J/ApJ/761/57
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- HR 8799 is an hF0 mA5 {gamma} Doradus-, {lambda} Bootis-, Vega-type star best known for hosting four directly imaged candidate planetary companions. Using the CHARA Array interferometer, we measure HR 8799's limb-darkened angular diameter to be 0.342+/-0.008mas (an error of only 2%). By combining our measurement with the star's parallax and photometry from the literature, we greatly improve upon previous estimates of its fundamental parameters, including stellar radius (1.44+/-0.06R_{sun}_), effective temperature (7193+/-87K, consistent with F0), luminosity (5.05+/-0.29L_{sun}_), and the extent of the habitable zone (HZ; 1.62-3.32AU). These improved stellar properties permit much more precise comparisons with stellar evolutionary models, from which a mass and age can be determined, once the metallicity of the star is known. Considering the observational properties of other {lambda} Bootis stars and the indirect evidence for youth of HR 8799, we argue that the internal abundance, and what we refer to as the effective abundance, is most likely near solar. Finally, using the Yonsei-Yale evolutionary models with uniformly scaled solar-like abundances, we estimate HR 8799's mass and age considering two possibilities: 1.516^+0.038^_-0.024_M_{sun}_ and 33^+7^_-13.2_Myr if the star is contracting toward the zero-age main sequence or 1.513^+0.023^_-0.024_M_{sun}_ and 90^+381^_-50_Myr if it is expanding from it. This improved estimate of HR 8799's age with realistic uncertainties provides the best constraints to date on the masses of its orbiting companions, and strongly suggests they are indeed planets. They nevertheless all appear to orbit well outside the HZ of this young star.
- ID:
- ivo://CDS.VizieR/J/ApJ/858/71
- Title:
- CHARA array obs. of 13 AB Dor moving group stars
- Short Name:
- J/ApJ/858/71
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present interferometric measurements obtained with the CHARA Array of 13 adolescent-age stars in nearby moving groups. The motivation was to spatially resolve the largest stars and to search for binary companions. Nine stars have diameters smaller than the resolution limit and no evidence for companions within 0.5-50mas and {Delta}H<2.0mag. The diameters of three stars were spatially resolved: GJ 159 (0.582+/-0.016mas) and GJ 393 (0.564+/-0.021mas) in the AB Dor moving group, and former member HD 89744 (0.556+/-0.032mas). Combining the angular diameters with their distances and bolometric fluxes, we measured radii and effective temperatures. The temperatures of GJ 159 (6286+/-123K) and GJ 393 (3515+/-68K) are consistent with spectroscopic measurements. Comparisons with evolutionary models show that HD 89744 has evolved off the main sequence. GJ 159 and GJ 393 lie within 1.5{sigma} of the zero-age main sequence, complicating their age estimates because it is unclear whether the stars are contracting or expanding. GJ 159 has a mass of 1.2+/-0.1M_{sun}_ with an age spanning 0.021-3.0Gyr. Its debris disk and lithium abundance favor a young age. GJ 393 has a mass of 0.42+/-0.03M_{sun}_ and a lower limit on its age 0.06Gyr. This overlaps with the age of the moving group; however, an older age would be more consistent with its slow rotation, low activity, and luminosity, suggesting that GJ 393 is a kinematic interloper.