Dwarfs in nearby voids: results of SALT spectroscopy

• DOI: 10.48550/arxiv.2312.07815
• Publication Date: 2023-01-01
• Authors: S. A. Pustilnik; A. Y. Kniazev; А. Л. Теплякова; Y. A. Perepelitsyna; E. S. Egorova
• Keywords: Doubly ionized oxygen; Line (geometry); Void (composites)

In the framework of ongoing project, aimed at systematical studying galaxies in nearby voids, we conducted spectroscopy with Southern African Large Telescope (SALT) 62 objects from Nearby Void Galaxy (NVG) sample. They include 8 remaining 60 preselected candidates to eXtremely Metal-Poor (XMP) dwarfs, two known void XMP dwarfs and 52 residing within Local Volume. For 47 obtained spectra diverse quality. 42 them, detected Hydrogen Oxygen lines that allowed us get estimates O/H observed HII regions. 12 objects, faint line [Oiii]4363, directly derive electron temperature T_e obtain their gas by direct method. 14 undetected [Oiii]4363 fall lowest metallicities range (12+log(O/H) < 7.5 dex). use a carefully checked new empirical 'Strong line' method Izotov et al. other only strong 12+log(O/H) ~7.5-8.0 dex, used modified version 'semi-empirical' Thuan. It accounts for effect excitation parameter O32 on T_e. 16 are found 7.39 dex. Of four have = 7.07 - 7.20 NVG 15 mistaken radial velocities HyperLEDA. do not reside voids.