- ID:
- ivo://CDS.VizieR/J/ApJ/892/105
- Title:
- Fourth catalog of Fermi LAT-detected AGNs (4LAC)
- Short Name:
- J/ApJ/892/105
- Date:
- 17 Jan 2022 00:31:09
- Publisher:
- CDS
- Description:
- The fourth catalog of active galactic nuclei (AGNs) detected by the Fermi Gamma-ray Space Telescope Large Area Telescope (4LAC) between 2008 August 4 and 2016 August 2 contains 2863 objects located at high Galactic latitudes (|b|>10{deg}). It includes 85% more sources than the previous 3LAC catalog based on 4yr of data. AGNs represent at least 79% of the high-latitude sources in the fourth Fermi-Large Area Telescope Source Catalog (4FGL), which covers the energy range from 50MeV to 1TeV. In addition, 344 gamma-ray AGNs are found at low Galactic latitudes. Most of the 4LAC AGNs are blazars (98%), while the remainder are other types of AGNs. The blazar population consists of 24% Flat Spectrum Radio Quasars (FSRQs), 38% BL Lac-type objects, and 38% blazar candidates of unknown types (BCUs). On average, FSRQs display softer spectra and stronger variability in the gamma-ray band than BL Lacs do, confirming previous findings. All AGNs detected by ground-based atmospheric Cerenkov telescopes are also found in the 4LAC.
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- ID:
- ivo://CDS.VizieR/I/143
- Title:
- Fourth Fundamental Cat and Suppl (FK4, FK4S)
- Short Name:
- I/143
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The FK4 was an attempt to establish a fundamental system of stellar positions and proper motions for the 1950 equinox using as much position data as were available. Most of the stars are brighter than 7.0 mag. To increase the star density in some regions of the sky, positions and proper motions for additional stars were established on the same system. This catalog contains seven data files, six for different equinoxes (1950, 1955, 1960, 1965, 1970, and 1975) and one for the supplemental stars. The 1950 and 1975 files contain the complete FK4 catalog (1535 stars); the others contain only 52 polar stars. In addition to a header record, the primary catalog contains for each star an identification number; the magnitude (maximum for a variable star); a variability flag, the minimum magnitude for a variable or the magnitude of the secondary for a double star; the HD spectral type and the type for the companion or a second type for a variable star; the position and the change and acceleration of the position; the proper motion and its change with time; the mean epoch of the observations for both right ascension and declination; the standard deviations of the position and proper motion; the numbers of the star in the Boss General Catalog, the N30 catalog, and in the Durchmusterungs; and the parallax. The supplement has a flag to indicate duplicity but no information about variability or the second component. It has no information about the temporal change of the position and proper motion and does not list the N30 and Durchmusterung numbers. It also omits the mean epoch for the observations.
- ID:
- ivo://CDS.VizieR/J/A+A/377/801
- Title:
- Fourth list of the Karachentsev catalog
- Short Name:
- J/A+A/377/801
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This paper presents HI observations of 165 dwarf galaxy candidates from the Karachentsev catalog of candidates for nearby dwarf galaxies prepared from film copies of POSSII and the ESO/SERC southern extension. Now a total of 601 galaxies from the published Karachentsev catalog have been searched for HI emission. Table 1 lists coordinates and general optical properties while Table 2 presents HI data and some global properties of these galaxies.
- ID:
- ivo://CDS.VizieR/I/182
- Title:
- Fourth Preliminary Catalogue of Stars
- Short Name:
- I/182
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using the data observed with the Photoelectric Astrolabe Mark II of the Beijing Astronomical Observatory (PPA) during the period from 1982 to 1990, the Fourth Preliminary Catalogue of Stars (PACP4) have been Compiled. It consists of 1969 stars including 650 FK5 stars and 1319 GC stars. The mean precisions of position corrections in right ascension and declination are 4.1 ms and 0.067", respectively. The declinations are from +11 deg to +69 deg. The magnitudes are from 0.1 to 7.3. The mean epoch of observations is 1986.8.
- ID:
- ivo://CDS.VizieR/J/other/PBeiO/17.120
- Title:
- Fourth preliminary catalogue of stars
- Short Name:
- J/other/PBeiO/17
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- On the photon counter data observed with Photoeleetric Transit Instrument of Beijing Astronomical Observatory during the period from 1988 to 1990, corrections of right ascensions of 324 stars are given. The mean precision (<m_{DELTA}{alpha}cos{delta}_>) is 4.7ms. The mean observational epoch is 1989.7. The relations of residuals with magnitudes and spectral types are discussed and given respectively. Finally the systematic corrections (PPCP4-FK4) are also analysed.
- ID:
- ivo://CDS.VizieR/IX/4
- Title:
- Fourth UHURU Catalogue (4U)
- Short Name:
- IX/4
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Fourth Uhuru (4U) Catalog lists 339 X-ray sources that were observed with the Uhuru (SAS A) X-ray observatory. It contains positional information in the form of 90% confidence level error boxes, 2-6keV intensities, possible optical and radio counterparts, and alternative names for sources observed in earlier compilations. The major classes of identified objects include binary stellar systems, supernova remnants, Seyfert galaxies, clusters of galaxies, and possibly the new class of superclusters of galaxies. The Uhuru satellite was a scanning X-ray instrument with a narrow (1 by 10 degree FWFM) and a wide (10 by 10 degree FWFM) collimator (cf. Giacconi et al. 1971ApJ...165L..27G). Typically, the scan rate was 0.5degree/second, with the spin axis in one position for roughly one day. During the interval for which the spin axis was fixed, repeated scans were made of the same 10 by 360 degrees band of the sky. For this catalog, the individual scans were superposed using aspect data from an orthogonally mounted triad of magnetometers and a Sun sensor onboard the spacecraft, supplemented by observations of well-located X-ray sources. The observations employed in producing this catalog were obtained over a total of 429 days between 1970 December 12 and 1973 March 18, apart from a gap between 1972 July and December when the spacecraft's transmitter was operating improperly.
- ID:
- ivo://CDS.VizieR/J/AJ/131/1872
- Title:
- Fourth VLBA calibrator survey: VCS4
- Short Name:
- J/AJ/131/1872
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This paper presents the fourth extension to the VLBA Calibrator Survey, containing 258 new sources not previously observed with very long baseline interferometry (VLBI). This survey, based on three 24hr Very Long Baseline Array observing sessions, fills remaining areas on the sky above declination -40{deg} where the calibrator density is less than one source within a 4{deg} radius disk in any given direction. The share of these areas was reduced from 4.6% to 1.9%. Source positions were derived from astrometric analysis of group delays determined at 2.3 and 8.6GHz frequency bands using the Calc/Solve software package. The VCS4 catalog of source positions, plots of correlated flux density versus projected baseline length, contour plots, and fits files of naturally weighted CLEAN images, as well as calibrated visibility function files, are available online at http://vlbi.gsfc.nasa.gov/vcs4 .
- ID:
- ivo://CDS.VizieR/J/A+A/633/A147
- Title:
- FQS. Galactic Plane CO survey
- Short Name:
- J/A+A/633/A147
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the Forgotten Quadrant Survey (FQS), an ESO large project that used the 12m antenna of the Arizona Radio Observatory to map the Galactic Plane in the range 220{deg}<l<240{deg}, and -2.5{deg}<b<0{deg}, both in ^12^CO(1-0), and ^13^CO(1-0), at a spectral resolution of 0.65km/s and 0.26km/s. We used the (1-0) transition of carbon monoxide to trace the molecular component of the interstellar medium. Our data set allows us to easily identify how the molecular dense gas is organised at different spatial scales: from the giant clouds with their denser filamentary networks, down to the clumps and cores that host the new-born stars and to obtain reliable estimates of their key physical parameters such as size and mass. We present the first release of the data of the FQS survey and discuss their quality. Spectra with 0.65km/s velocity channels have noise ranging from 0.8K to 1.3K for ^12^CO (1-0) and from 0.3K to 0.6K for ^13^CO (1-0). In this first paper, we used the ^12^CO (1-0) spectral cubes to produce a catalogue of 263 molecular clouds. The clouds are grouped in three main structures corresponding to the Local, Perseus, and Outer arms up to a distance of ~8.6kpc from the Sun. This is the first self-consistent statistical catalogue of molecular clouds of the outer Galaxy obtained with a subarcminute spatial resolution and therefore able to detect not only the classical giant molecular clouds, but also the small clouds and to resolve the cloud structure at the sub-parsec scale up to a distance of a few kiloparsec. We found two classes of objects: structures with sizes above a few parsecs that are typical molecular clouds and may be self-gravitating, and subparsec structures that cannot be in gravitational equilibrium and are likely transient or confined by external pressure. We used the ratio between the Herschel H2 column density and the integrated intensity of the CO lines to calculate the CO conversion factor and we found mean values of (3.3+/-1.4)x10^20^cm^-2^/(K.km/s) and (1.2+/-0.4)x10^21^cm^-2^/(K.km/s), for ^12^CO (1-0) and ^13^CO (1-0), respectively. FQS contributes to the general effort in producing a new generation of high-quality spectroscopic data for the Galactic Plane in the less studied third Galactic Quadrant, toward the outer Galaxy. FQS has produced a data-set of great legacy value, largely improving the data quality both in terms of sensitivity and spatial resolution over previous data sets.
- ID:
- ivo://CDS.VizieR/J/MNRAS/490/2521
- Title:
- Fractal Statistics in Young Star Clusters
- Short Name:
- J/MNRAS/490/2521
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We used fractal statistics to quantify the degree of observed substructures in a sample of 50 embedded clusters and more evolved open clusters (<100Myr) found in different galactic regions. The observed fractal parameters were compared with N-body simulations from the literature, which reproduce star-forming regions under different initial conditions and geometries that are related to the cluster' dynamical evolution. Parallax and proper motion from Gaia-DR2 were used to accurately determine cluster membership by using the Bayesian model and cross-entropy technique. The statistical parameters Q, <m> and <s> were used to compare observed cluster structure with simulations. A low level of substructures (Q<0.8) is found for most of the sample that coincides with simulations of regions showing fractal dimension D~2-3. Few clusters (<20 per cent) have uniform distribution with a radial density profile ({alpha}<2). A comparison of Q with mass segregation ({LAMBDA}MSR) and local density as a function of mass ({SIGMA}LDR) shows the clusters coinciding with models that adopt supervirial initial conditions. The age-crossing time plot indicates that our objects are dynamically young, similar to the unbound associations found in the Milky Way. We conclude that this sample may be expanding very slowly. The flat distribution in the Q-age plot and the absence of trends in the distributions of {LAMBDA}MSR and {SIGMA}LDR against age show that in the first 10 Myr the clusters did not change structurally and seem not to have expanded from a much denser region.
- ID:
- ivo://CDS.VizieR/J/MNRAS/456/2041
- Title:
- Fragmentation in filamentary molecular clouds
- Short Name:
- J/MNRAS/456/2041
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Recent surveys of dust continuum emission at sub-mm wavelengths have shown that filamentary molecular clouds are ubiquitous along the Galactic plane. These structures are inhomogeneous, with overdensities that are sometimes associated with infrared emission and active of star formation. To investigate the connection between filaments and star formation, requires an understanding of the processes that lead to the fragmentation of filaments and a determination of the physical properties of the overdensities (clumps). In this paper, we present a multiwavelength study of five filamentary molecular clouds, containing several clumps in different evolutionary stages of star formation. We analyse the fragmentation of the filaments and derive the physical properties of their clumps. We find that the clumps in all filaments have a characteristic spacing consistent with the prediction of the 'sausage' instability theory, regardless of the complex morphology of the filaments or their evolutionary stage. We also find that most clumps have sufficient mass and density to form high-mass stars, supporting the idea that high-mass stars and clusters form within filaments.