- ID:
- ivo://CDS.VizieR/J/A+A/654/A107
- Title:
- Catalogues of Blue Horizontal Branch Stars
- Short Name:
- J/A+A/654/A107
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- Blue horizontal-branch stars evolve from low-mass stars that have completed their main-sequence lifetimes and undergone a helium flash at the end of their red-giant phase. As such, blue horizontal-branch stars are very old objects that can be used as markers in studies of the Galactic structure and formation history. To create a clean sky catalogue of blue horizontal-branch stars, we cross-matched the Gaia data release 2 (DR2) dataset with existing reference catalogues to define selection criteria based on Gaia DR2parameters. Following the publication of Gaia early data release 3 (EDR3), these methods were verified and subsequently applied to this latest release. Previous catalogues of blue horizontal-branch stars were developed using spectral analyses or were restricted to individual globular clusters. The purpose of this catalogue is to identify a set of blue horizontal-branch star candidates that have been selected using photometric and astrometric observations and exhibits a low contamination rate. This has been deemed important as the success of the Gaia mission has changed the way that targets are selected for large-scale spectroscopic surveys, meaning that far fewer spectra will be acquired for blue horizontal-branch stars in the future unless they are specifically targeted. We cross-matched reference blue horizontal-branch datasets with the Gaia DR2 database and defined two sets of selection criteria. Firstly, in Gaia DR2 - colour and absolute G magnitude space, and secondly, in Gaia DR2 - colour and reduced proper motion space. The main-sequence contamination in both subsets of the catalogue was reduced, at the expense of completeness, by concentrating on the Milky Way's Galactic halo, where relatively young main-sequence stars were not expected. The entire catalogue is limited to those stars with no apparent neighbours within 5 arcsec. These methods were verified and subsequently applied to theGaia Early Data Release 3 (EDR3). We present a catalogue, based on Gaia EDR3, of 57377 blue horizontal-branch stars. The Gaia EDR3 parallax was used in selecting 16794 candidates and the proper motions were used to identify a further 40583 candidates.
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/584/A106
- Title:
- Catalogues of variable AGNs
- Short Name:
- J/A+A/584/A106
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Upcoming large area sky surveys like Euclid and eROSITA, which are dedicated to studying the role of dark energy in the expansion history of the Universe and the three-dimensional mass distribution of matter, crucially depend on accurate photometric redshifts. The identification of variable sources, such as active galactic nuclei (AGNs), and the achievable redshift accuracy for varying objects are important in view of the science goals of the Euclid and eROSITA missions. We probe AGN optical variability for a large sample of X-ray-selected AGNs in the XMM-COSMOS field, using the multi-epoch light curves provided by the Pan-STARRS1 (PS1) 3n and Medium Deep Field surveys. To quantify variability we employed a simple statistic to estimate the probability of variability and the normalized excess variance to measure the variability amplitude. Utilizing these two variability parameters, we defined a sample of varying AGNs for every PS1 band. We investigated the influence of variability on the calculation of photometric redshifts by applying three different input photometry sets for our fitting procedure. For each of the five PS1 bands g_P1_, r_P1_, i_P1_, z_P1_, and y_P1_, we chose either the epochs minimizing the interval in observing time, the median magnitude values, or randomly drawn light curve points to compute the redshift. In addition, we derived photometric redshifts using PS1 photometry extended by GALEX/IRAC bands.
- ID:
- ivo://CDS.VizieR/J/ApJ/921/91
- Title:
- Catastrophic cooling in superwinds. II.
- Short Name:
- J/ApJ/921/91
- Date:
- 15 Nov 2021
- Publisher:
- CDS
- Description:
- Superwinds and superbubbles driven by mechanical feedback from super star clusters (SSCs) are common features in many star-forming galaxies. While the adiabatic fluid model can well describe the dynamics of superwinds, several observations of starburst galaxies revealed the presence of compact regions with suppressed superwinds and strongly radiative cooling, i.e., catastrophic cooling. In the present study, we employ the non-equilibrium atomic chemistry and cooling package MAIHEM, built on the FLASH hydrodynamics code, to generate a grid of models investigating the dependence of cooling modes on the metallicity, SSC outflow parameters, and ambient density. While gas metallicity plays a substantial role, catastrophic cooling is more sensitive to high mass-loading and reduced kinetic heating efficiency. Our hydrodynamic simulations indicate that the presence of a hot superbubble does not necessarily imply an adiabatic outflow, and vice versa. Using CLOUDY photoionization models, we predict UV and optical line emission for both adiabatic and catastrophic cooling outflows, for radiation-bounded and partially density-bounded models. Although the line ratios predicted by our radiation-bounded models agree well with observations of star-forming galaxies, they do not provide diagnostics that unambiguously distinguish the parameter space of catastrophically cooling flows. Comparison with observations suggests the possibility of minor density bounding, non-equilibrium ionization, and/or observational bias toward the central outflow regions.
- ID:
- ivo://CDS.VizieR/J/A+A/551/A32
- Title:
- Catching the radio flare in CTA 102
- Short Name:
- J/A+A/551/A32
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Very Long Baseline Interferometry (VLBI) observations can resolve the radio structure of active galactic nuclei (AGN) and provide estimates of the structural and kinematic characteristics on parsec-scales in their jets. The changes in the kinematics of the observed jet features can be used to study the physical conditions in the innermost regions of these sources. We performed multifrequency multiepoch Very Long Baseline Array (VLBA) observations of the blazar CTA102 during its 2006 radio flare, the strongest ever reported for this source. These observations provide an excellent opportunity to investigate the evolution of the physical properties of blazars, especially during these flaring events. We want to study the kinematic changes in the source during the strong radio outburst in April 2006 and test the assumption of a shock-shock interaction. This assumption is based on the analysis and modeling of the single-dish observations of CTA 102 (Paper I, 2011A&A...531A..95F). In this paper we study the kinematics of CTA 102 at several frequencies using VLBI observations. From the modeled jet features we derived estimates for the evolution of the physical parameters, such as the particle density and the magnetic field. Furthermore ,we combined our observations during the 2006 flare with long-term VLBA monitoring of the source at 15 GHz and 43 GHz We cross-identified seven features throughout our entire multifrequency observations and find evidence of two possible recollimation shocks around 0.1mas (deprojected 18pc at a viewing angle of 2.6{deg} and 6.0mas (deprojected 1kpc) from the core. The 43GHz observations reveal a feature ejected at epoch t_ej_=2005.9+/-0.2, which could be connected to the 2006 April radio flare. Furthermore, this feature might be associated with the traveling component involved in the possible shock-shock interaction, which gives rise to the observed double peak structure in the single-dish light curves reported in Paper I, 2011A&A...531A..95F.
- ID:
- ivo://CDS.VizieR/J/A+A/580/A121
- Title:
- CaT/[Fe/H] calibration for Galactic bulge stars
- Short Name:
- J/A+A/580/A121
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a new calibration of the calcium II triplet equivalent widths versus [Fe/H], constructed upon K giant stars in the Galactic bulge. This calibration will be used to derive iron abundances for the targets of the GIBS survey, and is in general especially well suited for solar and supersolar metallicity giants, which are typical of external massive galaxies. To obtain the calibration, about 150 bulge K giants were observed with the GIRAFFE spectrograph at the VLT with a resolution of R~20000 and at R~6000. In the first case, the spectra allowed us to directly determine the Fe abundances from several unblended Fe lines, deriving what we call here high-resolution [Fe/H] measurements. The low-resolution spectra allowed us to measure equivalent widths of the two strongest lines of the near-infrared calcium II triplet at 8542 and 8662{AA}. By comparing the two measurements, we derived a relation between calcium equivalent widths and [Fe/H] that is linear over the metallicity range probed here, -1<[Fe/H]<+0.7. By adding a small second-order correction based on literature globular cluster data, we derived the unique calibration equation [Fe/H]_CaT_=-3.150+0.432W'+0.006W'^2^, with an rms dispersion of 0.197dex, valid across the whole metallicity range -2.3<[Fe/H]<+0.7.
- ID:
- ivo://CDS.VizieR/J/MNRAS/426/1475
- Title:
- CaT in 903 globular clusters
- Short Name:
- J/MNRAS/426/1475
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Although the colour distribution of globular clusters in massive galaxies is well known to be bimodal, the spectroscopic metallicity distribution has been measured in only a few galaxies. After redefining the calcium triplet index-metallicity relation, we use our relation to derive the metallicity of 903 globular clusters in 11 early-type galaxies. This is the largest sample of spectroscopic globular cluster metallicities yet assembled. We compare these metallicities with those derived from Lick indices finding good agreement. In six of the eight galaxies with sufficient numbers of high-quality spectra we find bimodality in the spectroscopic metallicity distribution. Our results imply that most massive early-type galaxies have bimodal metallicity as well as colour distributions. This bimodality suggests that most massive early-type galaxies experienced two periods of star formation.
- ID:
- ivo://svo.cab/cat/catlib
- Title:
- CaT library. Empirical Calibration of the Near-IR Ca II Triplet
- Short Name:
- CaT library
- Date:
- 03 Jun 2020 15:33:59
- Publisher:
- SVO/CAB
- Description:
- CaT library, Empirical Calibration of the Near-IR Ca II Triplet
- ID:
- ivo://CDS.VizieR/J/ApJ/408/305
- Title:
- Cat of Stellar Lyman-Alpha Fluxes
- Short Name:
- J/ApJ/408/305
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The data file gives the measured Lyman alpha flux or upper limits for 275 stars as derived from IUE spectra. The file is a subset of Table 1 of Landsman and Simon in that when a star had multiple measurements, only the best measurement is included in this table. The spectral types, V and B-V magnitudes in the table are culled from various sources as described in the paper. Most of the measurements are derived from low-dispersion spectra, and those derived from high-dispersion spectra are flagged. Each measurement was assigned a data quality code according to the signal to noise after removal of the diffuse Lyman alpha background emission. -1 - upper limit 1 - good quality 2 - fair quality 3 - poor quality 4 - contains saturated pixels The final column gives the ratio of the Ly alpha flux to the total bolometric flux of the star, determined as described in the paper. A roundoff was applied to the fluxes listed here to give the fluxes listed in Table 1 of Landsman and Simon.
- ID:
- ivo://sao.ru/cats
- Title:
- CATS Database - Astrophysical CATalogs support System
- Date:
- 23 Jun 2014 11:36:41
- Publisher:
- Special Astrophysical Observatory of RAS (SAO RAS)
- Description:
- The CATS (astrophysical CATalogs Support system), a publicly accessible tool maintained at Special Astrophysical Observatory of the Russian Academy of Sciences (SAO RAS) (http://cats.sao.ru) allowing one to search hundreds of catalogs of astronomical objects discovered all along the electromagnetic spectrum. Our emphasis is mainly on catalogs of radio continuum sources observed from 10 MHz to 245 GHz, and secondly on catalogs of objects such as radio and active stars, X-ray binaries, planetary nebulae, HII regions, supernova remnants, pulsars, nearby and radio galaxies, AGN and quasars. CATS also includes the catalogs from the largest extragalactic surveys with non-radio waves. In 2008 CATS comprised a total of about 10e9 records from over 400 catalogs in the radio, IR, optical and X-ray windows, including most source catalogs deriving from observations with the Russian radio telescope RATAN-600. CATS offers several search tools through different ways of access, e.g. via web interface and e-mail.
3090. CatWISE2020 Catalog
- ID:
- ivo://irsa.ipac/WISE/Catalog/CatWISE2
- Title:
- CatWISE2020 Catalog
- Short Name:
- CatWISE2
- Date:
- 02 Dec 2020 19:45:36
- Publisher:
- NASA/IPAC Infrared Science Archive
- Description:
- The CatWISE2020 catalog contains positions and brightnesses for 1,890,715,640 sources selected from combined WISE and NEOWISE all-sky survey data collected from 2010 to 2018 at 3.4 and 4.6 microns (W1 and W2). CatWISE adapts AllWISE software to measure the sources in co-added images created from six month subsets of these data, each representing one coverage of the inertial sky, or epoch. The catalog includes the measured motion of sources in 12 epochs over the 8 year span of the data.
