Star-galaxy separation by far-infrared color-color diagrams for the AKARI FIS All-Sky Survey (Bright Source Catalogue Version beta-1)

摘要

To separate stars and galaxies in the far infrared AKARI All-Sky Survey data,we have selected a sample with the complete color information available in thelow extinction regions of the sky and constructed color-color plots for thesedata. We looked for the method to separate stars and galaxies using the colorinformation. We performed an extensive search for the counterparts of theseselected All-Sky Survey sources in the NED and SIMBAD databases. Among 5176objects, we found 4272 galaxies, 382 other extragalactic objects, 349 Milky Waystars, 50 other Galactic objects, and 101 sources detected before in variouswavelengths but of an unknown origin. 22 sources were left unidentified. Then,we checked colors of stars and galaxies in the far-infrared flux-color andcolor-color plots. In the resulting diagrams, stars form two clearly separatedclouds. One of them is easy to be distinguished from galaxies and allows for asimple method of excluding a large part of stars using the far-infrared data.The other smaller branch, overplotting galaxies, consists of stars known tohave an infrared excess, like Vega and some fainter stars discovered by IRAS or2MASS. The color properties of these objects in any case make them verydifficult to distinguish from galaxies. We conclude that the FIR color-colordiagrams allow for a high-quality star-galaxy separation. With the proposedsimple method we can select more that 95 % of galaxies rejecting at least 80 %of stars.