Photometric Identification of Objects from Galaxy Evolution Explorer Survey and Sloan Digital Sky Survey

TL;DR

This study utilizes combined GALEX and SDSS photometry to classify over 80,000 objects near the North Galactic Pole, revealing most are extragalactic and developing a method to derive their properties for mapping galactic extinction.

Contribution

It introduces a photometric classification and parameter estimation method that distinguishes stars, galaxies, and quasars, and derives distances and extinctions, aiding in 3D galactic extinction mapping.

Findings

Most objects are extragalactic, not stars.

The method classifies objects into spectral and galactic types.

It derives distances, extinctions, and photometric redshifts.

Abstract

We have used GALEX and SDSS observations to extract 7 band photometric magnitudes for over 80,000 objects in the vicinity of the North Galactic Pole. Although these had been identified as stars by the SDSS pipeline, we found through fitting with model SEDs that most were, in fact, of extragalactic origin. Only about 9% of these objects turned out to be main sequence stars and about 11% were white dwarfs and red giants collectively, while galaxies and quasars contributed to the remaining 80% of the data. We have classified these objects into different spectral types (for the stars) and into different galactic types (for the galaxies). As part of our fitting procedure, we derive the distance and extinction to each object and the photometric redshift towards galaxies and quasars. This method easily allows for the addition of any number of observations to cover a more diverse range of wavelengths, as well as the addition of any number of model templates. The primary objective of this work is to eventually derive a 3-dimensional extinction map of the Milky Way galaxy.