Improving Catalogue Matching By Supplementing Astrometry with Additional Photometric Information
Monthly Notices of the Royal Astronomical Society
Oxford University Press (OUP)
The matching of sources between photometric catalogues can lead to cases where objects of differing brightness are incorrectly assumed to be detections of the same source. The rejection of unphysical matches can be achieved through the inclusion of information about the sources’ magnitudes. The method described here uses the additional photometric information from both catalogues in the process of accepting or rejecting counterparts, providing approximately a factor 10 improvement in Bayes’ factor with its inclusion. When folding in the photometric information we avoid using prior astrophysical knowledge. Additionally, the method allows for the possibility of no counterparts to sources as well as the possibility that sources overlap multiple potential counterparts. We formally describe the probability of two sources being the same astrometric object, allowing systematic effects of astrometric perturbation (by, e.g., contaminant objects) to be accounted for. We apply the method to two cases. First, we test IPHAS-Gaia matches to compare the resulting matches in two catalogues of similar wavelength coverage but differing dynamical ranges. Second, we apply the method to matches between IPHAS and 2MASS and show that the method holds when considering two catalogues with approximately equal astrometric precision. We discuss the importance of including the magnitude information in each case. Additionally, we discuss extending the method to multiple catalogue matches through an iterative matching process. The method allows for the selection of high-quality matches by providing an overall probability for each pairing, giving the flexibility to choose stars known to be good matches.
The authors thank the referee for their thorough report and useful comments, which helped us to improve this paper. TJW acknowledges support from an STFC Studentship. This work has made use of the SciPy (Jones et al. 2001), NumPy (van der Walt et al. 2011), Matplotlib (Hunter 2007), and F2PY (Peterson 2009) Python modules. This paper makes use of data obtained as part of the INT Photometric H_ Survey of the Northern Galactic Plane (IPHAS, www.iphas.org) carried out at the Isaac Newton Telescope (INT). The INT is operated on the island of La Palma by the Isaac Newton Group in the Spanish Obser- vatorio del Roque de los Muchachos of the Instituto de Astro_sica de Canarias. All IPHAS data are processed by the Cambridge Astronomical Survey Unit, at the Institute of Astronomy in Cambridge. The bandmerged DR2 cata- logue was assembled at the Centre for Astrophysics Re- search, University of Hertfordshire, supported by STFC grant ST/J001333/1. This publication makes use of data products from the Two Micron All Sky Survey, which is a joint project of the University of Massachusetts and the Infrared Processing and Analysis Center/California Institute of Technology, funded by the National Aeronautics and Space Administration and the National Science Foundation. This work has made use of data from the European Space Agency (ESA) mission Gaia (http://www.cosmos.esa.int/gaia), processed by the Gaia Data Processing and Analysis Consortium (DPAC, http://www.cosmos.esa.int/web/gaia/dpac/consortium). Funding for the DPAC has been provided by national insti- tutions, in particular the institutions participating in the Gaia Multilateral Agreement.
This is the author accepted manuscript. The final version is available from Oxford University Press via the DOI in this record.