Studies of Selected Voids. Surface Photometry of Faint Galaxies in the Direction of 1600+18 in Hercules Void

Based on photographic plates obtained with 2m RCC telescope at National Astronomical Observatory Rozhen (Bulgaria) we inspected an area of ~1 sq.degree in the direction of the Hercules void with automatic object detection software. As our first result we present a list of ~1800 detected galaxies in the wide range of magnitudes 13≤B≤21 and effective surface brightnesses 16≤μeff(B) ≤ 24 mag arcsec. Introduction The presence of voids in the distribution of galaxies has been discovered in early redshift surveys of galaxies see e.g. [1, 2]. Further studies show that the largest voids are those delineated by rich clusters and superclusters of galaxies [3, 4]. The Hercules region has attracted the attention of astronomers since [5] discovered the Hercules supercluster covers a large area of the sky north of celestial equator in the range ascension range between 12 < α < 18. A collaboration project between the Institute of Astronomy of Bulgarian Academy of Sciences and Max Plank Institute for Astronomy (Heidelberg, Germany) is devoted to investigate some known voids [6]. We present here the first results of a study of faint galaxies in the direction of Hercules void. Observations The observations were done during the nights of 27 and 28 June 1991. The Ritchie camera of the 2m RCC telescope at National Astronomical Observatory ′′Rozhen′′ (Bulgaria) was used to get two plates centered on RA(2000): 160158 and DEC: +17°57′30′′ (No.1830 hereafter) and RA: 160215 and DEC: ++17°51′34′′ (No.1831 hereafter).