Gaia DR3 data (both Gaia EDR3 and the full Gaia DR3) are based on data collected between 25 July 2014 (10:30 UTC) and 28 May 2017 (08:44 UTC), spanning a period of 34 months. As a comparison, Gaia DR2 was based on 22 months of data and Gaia DR1 was based on observations collected during the first 14 months of Gaia's routine operational phase. Survey completeness: The Gaia EDR3 catalogue is essentially complete between G=12 and G=17. The source list for the release is incomplete at the bright end and has an ill-defined faint magnitude limit, which depends on celestial position. The combination of the Gaia scan law coverage and the filtering on data quality which will be done prior to the publication of Gaia EDR3, does lead to some regions of the sky displaying source density fluctuations that reflect the scan law pattern. In addition, small gaps exist in the source distribution, for instance close to bright stars. Astrometry: The parallax improvement is typically 20% with respect to Gaia DR2. The proper motions are typically a factor two better than in Gaia DR2. An overall reduction of systematics has been achieved. E.g., the parallax zero point deduced from the extragalactic sources is about -20{mu}as. A tentative correction formula for the parallax zero point will be provided. Closer to the release date of Gaia Early Data Release 3, an update will be given on the astrometry. Photometry: The G-band photometric uncertainties are ~0.25mmag for G<13, 1mmag at G=17, and 5mmag at G=20mag. The GBP-band photometric uncertainties are ~1mmag for G<13, 10mmag at G=17, and 100mmag at G=20mag. The GRP-band photometric uncertainties are ~1mmag for G<13, 5mmag at G=17, and 50mmag at G=20mag. Closer to the release date of Gaia Early Data Release 3, an update will be given on the photometry. Gaia EDR3 does not contain new radial velocities. The radial velocities of Gaia Data Release 2 have been added to Gaia EDR3 in order to ease the combination of spectrosopic and astrometric data. Radial velocities: Gaia EDR3 hence contains Gaia DR2 median radial velocities for about 7.21 million stars with a mean G magnitude between ~4 and ~13 and an effective temperature (Teff) in the range ~3550 to 6900K. The overall precision of the radial velocities at the bright end is of the order of ~200-300m/s while at the faint end, the overall precision is ~1.2km/s for a Teff of 4750K and ~3.5km/s for a Teff of 6500K. Before publication in Gaia EDR3, an additional filtering has been performed onto the Gaia DR2 radial velocities to remove some 4000 sources that had wrong radial velocities. Please be aware that the Gaia DR2 values are assigned to the Gaia EDR3 sources through an internal cross-match operation. In total, ~10000 Gaia DR2 radial velocities could not be associated to a Gaia EDR3 source. Astrophysical parameters: Gaia EDR3 does not contain new astrophysical parameters. Astrophysical parameters have been published in Gaia DR2 and a new set is expected to be released with the full Gaia DR3 release. Variable stars: Gaia EDR3 does not contain newly classified variable stars. For the overview of the currently available variable stars from Gaia DR2, have a look here. Classifications for a larger set of variable stars are expected with the full Gaia DR3 release. Solar system objects: A large set of solar system objects with orbits will become available with the full Gaia DR3 release. Information on the currently available asteroids in Gaia DR2 can be found here. Documentation: Data release documentation is provided along with each data release in the form of a downloadable PDF and a webpage. The various chapters of the documentation have been indexed at ADS allowing them to be cited. Please visit the Gaia Archive (https://gea.esac.esa.int/archive) to access this documentation, and make sure to check out all relevant information given through the documentation overview page (https://www.cosmos.esa.int/web/gaia-users/archive).
We present a sub-arcsecond cross-match of Gaia DR2 (Cat. I/345) against the INT Photometric H-alpha Survey of the Northern Galactic Plane Data Release 2 (IPHAS DR2, Cat. II/321) and the Kepler-INT Survey (KIS, Cat. J/AJ/144/24). The resulting value-added catalogues (VACs) provide additional precise photometry to the Gaia photometry (r, i and H-alpha for IPHAS, with additional U and g for KIS). In building the catalogue, proper motions given in Gaia DR2 are wound back to match the epochs of IPHAS DR2, thus ensuring high proper motion objects are appropriately cross-matched. The catalogues contain 7927224 and 791071 sources for IPHAS and KIS, respectively. The requirement of >5 sigma parallax detection for every included source means that distances out to 1-1.5kpc are well covered. We define two additional parameters for each catalogued object: (i) fc, a magnitude-dependent tracer of the quality of the Gaia astrometric fit; (ii) fFP, the false-positive rate for parallax measurements determined from astrometric fits of a given quality at a given magnitude. Selection cuts based on these parameters can be used to clean colour-magnitude and colour-colour diagrams in a controlled and justified manner. We provide both full and light versions of the VAC, with VAC-light containing only objects that represent our recommended trade-off between purity and completeness. Uses of the catalogues include the identification of new variable stars in the matched data sets, and more complete identification of H-alpha-excess emission objects thanks to separation of high-luminosity stars from the main sequence.
We use a new Very Large Array Galactic plane catalog at 1.4GHz (Cat. <J/AJ/130/586>) covering the first and second Galactic quadrants (340{deg}<=l<=120{deg}, |b|<=0.8{deg} with |b|<=1.8{deg} for 350{deg}<=l<=40{deg} and |b|<=2.5{deg} for 100{deg}<=l<=105{deg}) in conjunction with the MSX6C (Cat. <V/114>) Galactic plane mid-infrared catalog to supplement and better understand our 5GHz catalog (Cat. <J/ApJS/91/347>).
We present a compilation of hopefully all published galaxies and quasars that were ever optically identified within |b|=<5deg. We present 2304 objects and list (and discuss), in addition to their (often considerably improved) coordinates, the best available morphological type, optical maximum diameters in the red, up-to-date heliocentric radial velocities, references to the papers where a specific object was first optically identified and results of cross-checks with the IRAS point source catalogue.
We have carried out a systematic search for galaxies in the galactic plane in a ten degree wide strip (-5deg<=b<=+5deg). In an area of 300 square degrees between l=180deg and l=210deg, 755 galaxies have been detected on Palomar red- sensitive prints. The smallest galaxies show diameters of 0.1mm corresponding to 6.7". We extended our survey to {delta}=-27deg i.e. l=~247deg to check our catalogue for completeness by comparing it with the Saito et al. (1990, 1991) catalogues of galaxies and present 334 new galaxy candidates at l>=210deg. An asymmetry with respect to the galactic equator is obvious. By assuming the 60{mu} and 100{mu} sky flux density to be a rough measure of the total interstellar galactic extinction, and comparing them with the surface densities of the galaxies, we detected one possible galaxy cluster candidate at (l,b)=~(181.5deg+3.5deg), a concentration of galaxies at (l,b)=~(195deg+4.5deg), and confirmed three other galaxy concentrations. Finally, we argue that the red-sensitive surveys (ESO R; POSS II-R, POSS II-IR) are the best suitable material for galaxy searches in the zone of avoidance.
As the third part in a series of papers on galaxies in the "zone of avoidance" (ZOA) of the Milky Way we present a compilation of 1161 galaxies discovered during a systematic search on Palomar Observatory Sky Survey (POSS) red-sensitive prints. The region searched comprises 200 square degrees, at 120deg<=l<=130deg, -10deg<=b<=+10deg. In addition to galactic, equatorial and rectangular coordinates, we list maximum and minimum optical diameters derived from both the red- and blue-sensitive prints, could assign a morphological type to some of the objects and made cross-checks with the IRAS PSC and several radio catalogues. A test for completeness suggests, that our catalogue should be complete down to a limiting galaxy-diameter of 0.35'. An asymmetric distribution of the galaxies with respect to the galactic equator was found and is discussed by comparing it with the locations of optically visible dust clouds and/or the distribution of IR-emitting dust material. A comparison between the distribution of the galaxies and the 100{mu} IRAS intensity maps led to the identification of four possible clusterings. As a byproduct of our galaxy search, two new planetary nebulae, nebulous stars at the position of a strong cold IRAS point source, and a nearby dwarf irregular galaxy could be detected.
As the fourth part in a series of papers on galaxies in the "zone of avoidance" (ZOA) of the Milky Way we present a compilation of 1067 galaxies discovered during a systematic search on Palomar Observatory Sky Survey I (POSSI) red-sensitive prints. The region searched comprises 500 square degrees, at 130{deg}<=l<=180{deg}, -5{deg}<=b<=+5{deg}. In addition to galactic and equatorial coordinates, we list maximum and minimum optical diameters derived from both the red- and blue-sensitive prints and made cross checks with the IRAS PSC catalogue. An asymmetric distribution of the galaxies with respect to the galactic equator is found and is compared to the locations of optically visible dust clouds and/or the distribution of IR-emitting dust material. There is a pronounced bridge of galaxies across the galactic plane at l=~160{deg} which will be discussed according to recent results on the extension of the Pisces-Perseus supercluster.
As the fifth part in our series of papers on galaxies in the "zone of avoidance" (ZOA) of the Milky Way we present 1346 new galaxy candidates discovered during a systematic search on Palomar Observatory Sky Survey (POSSI-E) red-sensitive prints. The region searched comprises 400 square degrees at 90{deg}<=l<=110{deg}, -10{deg}<=b<=+10{deg}. We list galactic and equatorial coordinates, maximum optical diameters and diameters of the core, if visible, both for the red- and blue-sensitive POSS prints. An asymmetric distribution of the galaxies with respect to the galactic equator is found and can most probably be attributed to the galactic warp. We also present radial velocities for 14 galaxies measured for the first time which are located in the region where a branch of the Pisces Perseus Supercluster is approaching the ZOA from the south (l=~90{deg}, b=~-10{deg}).
We present a catalog of galaxy cluster candidates, selected through their Sunyaev-Zel'dovich (SZ) effect signature in the first 720deg^2^ of the South Pole Telescope (SPT) survey. This area was mapped with the SPT in the 2008 and 2009 austral winters to a depth of ~18{mu}K_CMB_-arcmin at 150GHz; 550deg^2^ of it was also mapped to ~44{mu}K_CMB_-arcmin at 95GHz. Based on optical imaging of all 224 candidates and near-infrared imaging of the majority of candidates, we have found optical and/or infrared counterparts for 158, which we then classify as confirmed galaxy clusters. Of these 158 clusters, 135 were first identified as clusters in SPT data, including 117 new discoveries reported in this work. This catalog triples the number of confirmed galaxy clusters discovered through the SZ effect. We report photometrically derived (and in some cases spectroscopic) redshifts for confirmed clusters and redshift lower limits for the remaining candidates. The catalog extends to high redshift with a median redshift of z=0.55 and maximum confirmed redshift of z=1.37. Forty-five of the clusters have counterparts in the ROSAT bright or faint source catalogs from which we estimate X-ray fluxes. Based on simulations, we expect the catalog to be nearly 100% complete above M_500_{approx}5x10^14^M_{sun}_h^-1^_70_ at z>~0.6. There are 121 candidates detected at signal-to-noise ratio greater than five, at which the catalog purity is measured to be 95%.
Clusters of galaxies in most of the previous catalogs have redshifts z<=0.3. Using the photometric redshifts of galaxies from the Sloan Digital Sky Survey Data Release 6 (SDSS DR6), we identify 39716 clusters in the redshift range 0.05<z<0.6 with more than eight luminous (M_r_<=-21) member galaxies. Cluster redshifts are estimated accurately with an uncertainty of less than 0.022. The contamination rate of member galaxies is found to be roughly 20%, and the completeness of member galaxy detection reaches ~90%. Monte Carlo simulations show that the cluster detection rate is more than 90% for massive (M_200_>2x10^14^M_{sun}_) clusters of z<=0.42. The false detection rate is ~5%. We obtain the richness, the summed luminosity, and the gross galaxy number within the determined radius for identified clusters. They are tightly related to the X-ray luminosity and temperature of clusters. Cluster mass is related to the richness and summed luminosity with M_200_{prop.to}R^1.90+/-0.04^ and M_200_{prop.to}L^1.64+/-0.03^_r_, respectively. In addition, 790 new candidates of X-ray clusters are found by cross-identification of our clusters with the source list of the ROSAT X-ray survey.
