VizieR Online Data Catalog: PMA Catalogue (Akhmetov+, 2017)
Abstract
The idea for creating the catalogue is very simple. The PMA catalogue has been derived from a combination of two catalogues, namely 2MASS and Gaia DR1. The difference of epochs of observations for these catalogues is approximately 15 yr. The positions of objects in the Gaia DR1 catalogue are referred to the reference frame, which is consistent with ICRF to better than 0.1 mas for the J2015.0 epoch. The positions of objects in 2MASS are referred to HCRF, which, as was shown in Kovalevsky et al. (1997A&A...323..620K), is aligned with the ICRF to within ±0.6 mas at the epoch 1991.25 and is non-rotating with respect to distant extragalactic objects to within ±0.25mas/yr. By comparing the positions of the common objects contained in the catalogues, it is possible to determine their proper motions within their common range of stellar magnitudes by dividing differences of positions over the time interval between their observations. Formally, proper motions derived in such a way are given in the ICRF system, because the positions of both Gaia DR1 stars and those of 2MASS objects (through Hipparcos/Tycho-2 stars) are given in the ICRF and cover the whole sphere without gaps. We designate them further in this paper as relative, with the aim of discriminating them from absolute ones, which refer to the reference frame defined by the positions of about 1.6 million galaxies from Gaia DR1.
There is no possibility of obtaining estimates of individual errors of proper motions of stars for the PMA Catalogue from the intrinsic convergence, because the direct errors for positions are not indicated in 2MASS. Therefore we use some indirect methods to obtain the estimates of uncertainties for proper motions. After elimination of the systematic errors, the root-mean-squared deviation of the coordinate differences of extended sources is about 200mas, and the mean number of galaxies inside each pixel is about 1300, so we expect the error of the absolute calibration to be 0.35mas/yr. We compared the proper motions of common objects from PMA and from the TGAS and UCAC4 catalogues. Knowing the mean-square errors of (PMA-TGAS) and (PMA-UCAC4) proper motion differences in each pixel, the appropriate errors in PMA vary from 2 to 10mas/yr, depending on magnitude, which are consistent with the errors calculated above. In case of any problems or questions, please contact by e-mail V.S. Akhmetov (akhmetovvs(at)gmail.com or akhmetov(at)astron.kharkov.ua). (1 data file).- Publication:
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VizieR Online Data Catalog
- Pub Date:
- June 2017
- Bibcode:
- 2017yCat.1341....0A
- Keywords:
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- Positional data;
- Proper motions