RevMexAA (Serie de Conferencias), 00, 1–1 (2007) ABSTRACT ONLY VVV-J144321.0-611753.9: THE FIRST CANDIDATE FOR A GALAXY CLUSTER DISCOVERED IN THE VISTA VARIABLES IN THE VIA LACTEA SURVEY J. L. Nilo Castellón1,2 , M. V. Alonso3,4 , L. Baravalle3 C. Valotto3,4 , R. Barbá1 . D. Minniti5 This abstract summarizes our mural contribution to the conference. The structure of the Milky Way has been the main obstacle in the study of the Large Scale of the Universe (LSS). This has been a major problem over the years, since the mapping of the extragalactic sources located behind the bulge and the disk of the galaxy, is essential to determine the extension of the structures located behind the MW, which define among others, the dynamic of our Local Group. The Search for Extragalactic Sources in the VISTA Variables in the Via Lactea Survey (Baravalle et al. 2015, in prep), is the first systematic program devoted to search for extragalactic sources obscured by the bulge and the plane of the Milky Way, in the area covered by the VVV survey. The main goal of the project, is to look for galaxies, quasars, blazars and galaxy clusters located behind the galaxy structure, in order to contributing in the mapping of the Large Scale Structure The program take advantage of the high resolution images provided by the VVV survey, and the latest versions of the AtrOmatic pipelines, to reprocessed the images and create full catalogs based on Point-Spread Function (PSF) fitting photometry, in order to obtain a series of morphological parameters, astrometrical values, and photometric properties of each source detected. We report the discovery of SESVVV-001 (VVV J144321.0-611753.9), the first concentration of galaxies classified as the first galaxy cluster candidate detected using only data provided by the VVV survey. VVVSES-001 is located at α=14h 43m 20.9s δ=61◦ 17m 53.6s , and is composed by 25 galaxies (at least), all of them with magnitudes ranging between 14 < Ks < 17. The Color-Magnitude Diagram shows a clear trend of galaxies at (J - K)∼1.8, with an slope of s=-0.0453 and a zero-point of zp=2.5001 for the best lineal fit. A population of blue galaxies bellow 3σ the best lineal fit is also observed, with a similar distribution to the called blue cloud of galaxies. Comparing the (J - K) color of the most brightest galaxy(BCG) and the slope of the RCS with Bruzual & Charlot (2003) models and semi-analytical models extracted from Bower et al. (2006) locate VVVSES001 at z∼0.434. X-ray emission extracted from the ROSAT All Sky Survey indicate that the core of VVVSES-001 is clearly detected in X-rays emission, with the cluster core about 1 arcmin in the north direction of the X-ray peak emission. 1 Departamento de Fı́sica y Astronomı́a, Universidad de La Serena, Avenida Juan Cisternas 1200, La Serena, Chile. (jnilo @userena.cl) 2 Dirección de Investigación. Universidad de La Serena. Avenida Raul Bitran s/n, La Serena, Chile. 3 Instituto de Astronoma Teórica y Experimental (IATECONICET). Laprida 922, Córdoba, Argentina. 4 Observatorio Astronómico, Universidad Nacional de Córdoba (OAC-UNC), Laprida 854, Córdoba, Argentina. 5 Observatorio Astronómico, Universidad Nacional de Córdoba (OAC-UNC), Laprida 854, Córdoba, Argentina. 1