Initial Gaia Source List
Initial Gaia Source List (IGSL) is a star catalog in support of the Gaia mission . In the end, the Gaia mission should deliver a catalog based entirely on its own data. For the initial phase, however, a way was needed to match the Gaia objects with the objects from other star catalogs. For this purpose, a separate catalog of objects from several other catalogs was compiled, which roughly represents the level of knowledge of astronomy at the beginning of the Gaia mission.
The entries were limited to a magnitude brighter than G = 21 at the weaker end , but the Gaia Ecliptic Pole Catalog and Large Quasar Reference Frame are excluded from the magnitude limit.
IGSL formed the basis for the Gaia DR1 star catalog . Since the second Gaia DR2 data catalog , the IGSL has largely become obsolete for data processing with DPAC , DPAC now uses the Main Data Base Catalog (MDB), which is based on the data from Gaia, but the small SPSS catalog is becoming more important for the Keep the photometry calibration for the entire mission.
Attitude Star Catalog
A subset of the IGSL objects exists in the Attitude Star Catalog. This catalog was required for the first approximation of the iterative evaluation of the Gaia data. There should be 75 such stars per square degree as temporary guide stars. The prerequisite for being accepted as an Attitude Star was:
- G-band magnitude brighter than 13.4.
- Known positions with an accuracy of better than 200 mas.
- 75 individual stars per square degree.
- There must be no other bright objects in the 40 ”area
- The object must not in Washington Double Star Catalog be listed
There are some regions in the realm of the poles that have fewer than 75 such stars. In more densely populated regions more than 1000 stars would have been possible in some cases, in these cases the magnitude limit was raised in favor of brighter objects. The Attitude Star Catalog has a total of 8,173,331 entries with information on position, proper movement and magnitudes. All objects in total have been assigned to a nearby guiding star. When evaluating the Gaia data, the positions of the guide stars were calculated in the first calculations, then the positions of the other assigned objects together relative to the guide stars. In this way, the computational effort is limited and a low standard deviation is achieved in the first iterations.
Gaia Spectrophotometric Standard Star Catalog (SPSS)
IGSL contains a list of approx. 200 stars of different spectral classes and magnitudes for calibrating the photometric measurements . It is the result of the Gaia Spectrophotometric Standard Stars Survey (SPSS), a selection of stars using Earth-based data in advance of the Gaia mission. Previous catalogs for calibrating the magnitudes, including the pole sequence, could not be used for Gaia, as many of these objects are too bright for detection with Gaia. It is anticipated that some of the selected stars may be double stars or variable stars that have not yet been recognized and that would have to be deleted, for this reason the list contains more stars than necessary.
Gaia Initial Quasar Catalog (GIQC)
A list of quasars based on the Large Quasar Astrometric Catalog was compiled for IGSL . This in turn goes back to Sloan Digital Sky Survey . From the over one million objects, a selection of 150,000 quasars was made, which is in the range of the magnitude limit of Gaia. The selected objects have already been carefully observed and documented. Quasars are in most cases very far away, so that their proper movements and parallaxes are negligibly small.
content
Version 3.0 of the IGSL was finally determined in September 2013 and contains a total of 1,222,598,530 objects. The following catalogs were used for this list:
- Gaia Ecliptic Pole Catalog : The Gaia Ecliptic Pole Catalog. Version 3.0
- GSC2.3 : The Second Guide Star Catalog. Version 2.3
- LQRF: Large Quasar Reference Frame.
- OGLE : Optical Gravitational Lensing Experiment. Version III
- PPMXL: Catalog of positions and proper motions on the ICRS
- SDSS : Sloan Digital Sky Survey. Data Release 9
- UCAC4 : USNO CCD Astrograph Catalog. Version 4
- 2MASS : Two Micron All-Sky Survey Point Source Catalog.
- Tycho-2 , Hipparcos , Sky2000 and Gaia Spectrophotometric Standard Star catalog (SPSS) as defined by the Gaiamission working group CU5.
IGSL4
The IGSL was not only used for Gaia, but also in other places. The merging of the various data sets caused various problems, for example data was overwritten by other data sets, objects were omitted or listed twice. Version four of the IGSL corrected these known problems.
Individual evidence
- ↑ a b R. L. Smart: The Initial Gaia Source List and the Attitude Star Catalog GAIA-C3-TN-OATO-RLS-004-02 . Ed .: Gaia DPAC Data Processing & Analysis Consortium. October 17, 2013 ( esa.int ).
- ^ RL Smart: The Attitude Star Catalog . GAIA-C3-TN-OATO-RLS-007-1. Ed .: DPAC. April 28, 2014 ( inaf.it [PDF]).
- ↑ E. Pancino et al .: The Gaia spectrophotometric standard stars survey. I. Preliminary results. ( arxiv.org [PDF]).
- ↑ C. Jordi et al .: The Gaia Spectrophotometric Standard Stars . ( sea-astronomia.es [PDF]).
- ↑ Daniel Michalik and Lennart Lindegren: Quasars can be used to verify the parallax zero-point of the Tycho-Gaia Astrometric Solution . Ed .: A&A. 586, A26 (2016), September 24, 2015, doi : 10.1051 / 0004-6361 / 201527444 .
- ↑ F. Mignard, S. Klioner, L. Lindegren et al .: Gaia Data Release 1; Reference frame and optical properties of ICRF sources . doi : 10.1051 / 0004-6361 / 201629534 ( aanda.org [PDF]).
- ↑ Gaia project and DPAC News . No. 23 , April 25, 2014, pp. 7 ( esa.int [PDF]).
- ^ Siegfried Roeser, Markus Demleitner, Elena Schilbach: The PPMXL catalog of positions and proper motions on the ICRS. Combining USNO-B1.0 and 2MASS. Ed .: The Astronomical Journal. No. 139 , March 30, 2010, p. 2440-2447 , doi : 10.1088 / 0004-6256 / 139/6/2440 , arxiv : 1003.5852 ( iop.org [PDF]).
- ^ RL Smart, L. Nicastro: The initial Gaia source list . May 20, 2014, doi : 10.1051 / 0004-6361 / 201424241 ( inaf.it [PDF]).