Searching for Extragalactic Sources in the VISTA Variables in the V\'ia L\'actea Survey

TL;DR

This study develops a photometric method combining SExtractor and PSFEx to identify and characterize extragalactic sources hidden by the Milky Way in the VISTA Variables in the Vía Láctea survey, successfully detecting and confirming numerous galaxy candidates.

Contribution

The paper introduces a new photometric procedure for finding extragalactic objects in the VVV survey, enabling the study of galaxies obscured by the Milky Way.

Findings

Detected 345 and 185 extragalactic candidates in two survey tiles.

All candidates were visually confirmed as galaxies.

Method will be applied to other survey tiles for galaxy distribution analysis.

Abstract

We search for extragalactic sources in the VISTA Variables in the V\'ia L\'actea survey that are hidden by the Galaxy. Herein, we describe our photometric procedure to find and characterize extragalactic objects using a combination of SExtractor and PSFEx. It was applied in two tiles of the survey: d010 and d115, without previous extragalactic IR detections, in order to obtain photometric parameters of the detected sources. The adopted criteria to define extragalactic candidates include CLASS_STAR < 0.3; 1.0 < R1/2 < 5.0 arcsec; 2.1 < C < 5; and Phi > 0.002 and the colors: 0.5 < (J - K_s) < 2.0 mag; 0.0 < (J - H) < 1.0 mag; 0.0 < (H - K_s) < 2.0 mag and (J - H) + 0.9 (H - K_s) > 0.44 mag. We detected 345 and 185 extragalactic candidates in the d010 and d115 tiles, respectively. All of them were visually inspected and confirmed to be galaxies. In general, they are small and more circular objects, due to the near-IR sensitivity to select more compact objects with higher surface brightness. The procedure will be used to identify extragalactic objects in other tiles of the VVV disk, which will allow us to study the distribution of galaxies and filaments hidden by the Milky Way.