Properties of dwarf galaxies formed and evolved in the lowest density environment remain largely unexplored and poorly understood. Especially this concerns the low-mass end (M_bar < 10^9 Mo). We overview the results of systematic study of a hundred void dwarfs from the nearby Lynx-Cancer void. We describe the ongoing project aiming to form Nearby Void galaxy sample (R < 25 Mpc) over the whole sky. 1354 objects with distances less than 25 Mpc fall within 25 voids delineated by 460 luminous galaxies/groups. The void major sizes range from 13 to 37 Mpc. 1088 of 1354 void galaxies reside deeply in voids, having distances to the nearest luminous neighbour of 2-11 Mpc. 195 nearest void galaxies reside in the Local Volume. We summarize the main statistical properties of the new sample and outline the prospects of study of both, the void dwarf properties and the fine structure of voids.
Voids occupy about 3/4 of the volume of the Universe and contain about 15% of its mass. Due to various observational selection effects, these structure elements and galaxies populating voids, are highly under-explored. This especially relates to the lowest mass galaxies which comprise the main void population. Studying the nearby voids allows us to improve our understanding of the most elusive void objects. We present the brief overview of the current status and the prospects of the study of the nearest voids and their galaxies. First, we summarize the pioneer study of a hundred galaxies resid…
We present the detection of molecular gas from galaxies located in nearby voids using the CO line emission as a tracer. The observations were done using the 45m Nobeyama Radio Telescope. Void galaxies lie in the most under dense parts of our universe and a significant fraction of them are gas rich, late type spiral galaxies. Although isolated, they have ongoing star formation but appear to be slowly evolving compared to galaxies in denser environments. Not much is known about their star formation properties or cold gas content. In this study we searched for molecular gas in five void galaxies.…
The main goal of this work is to form a large, deep and representative sample of dwarf galaxies residing in voids of the nearby Universe. The formed sample is the basement for the comprehensive mass study of the galaxy content, their evolutionary status, clustering and dynamics with respect to their counterparts residing in more typical, denser regions and for study of void small-scale substructures. We present 25 voids over the entire sky within 25 Mpc from the Local Group. They are defined as groups of lumped empty spheres bounded by `luminous' galaxies with the absolute K-band magnitudes br…
We present the detection of molecular gas using CO(1-0) line emission and follow up Halpha imaging observations of galaxies located in nearby voids. The CO(1-0) observations were done using the 45m telescope of the Nobeyama Radio Observatory (NRO) and the optical observations were done using the Himalayan Chandra Telescope (HCT). Although void galaxies lie in the most under dense parts of our universe, a significant fraction of them are gas rich, spiral galaxies that show signatures of ongoing star formation. Not much is known about their cold gas content or star formation properties. In this …
The intermediate results of the ongoing study of deep samples of ~200 galaxies residing in nearby voids, are presented. Their properties are probed via optical spectroscopy, ugri surface photometry, and HI 21-cm line measurements, with emphasis on their evolutionary status. We derive directly the hydrogen mass M(HI), the ratio M(HI)/L_B and the evolutionary parameter gas-phase O/H. Their luminosities and integrated colours are used to derive stellar mass M(*) and the second evolutionary parameter -- gas mass-fraction f_g. The colours of the outer parts, typically representative of the galaxy o…
In the framework of an ongoing project aimed at searching for and studying eXtremely Metal-Poor (XMP) very gas-rich blue dwarfs in nearby voids, we conducted spectroscopy with the 11-m Southern African Large Telescope (SALT) of 26 candidates, preselected in the first paper of this series (PEPK19). For 23 of them, we detected Oxygen lines, allowing us to estimate the gas O/H ratio. For ten of them, the oxygen abundance is found to be very low, in the range of 12+log(O/H)=6.95-7.30 dex. Of those, four void dwarfs have 12+log(O/H) < 7.19, or Z < Zo/30. For the majority of observed galaxies, the f…
Galaxy interactions in void substructures: Morphology and stellar populations of two triplets from CAVITY
Universidad de Granada（格拉纳达大学）；Universidade Federal do Rio Grande do Sul (UFRGS)（南里奥格兰德联邦大学）；Universidade Federal do Rio Grande (IMEF – FURG)（里奥格兰德联邦大学）；University of Hertfordshire（赫特福德大学）
We present the first detailed integral field spectroscopy study of nine central void galaxies with M*>10^10 Msun using the Wide Field Spectrograph (WiFeS) to determine how a range of assembly histories manifest themselves in the current day Universe. While the majority of these galaxies are evolving secularly, we find a range of morphologies, merger histories and stellar population distributions, though similarly low Halpha-derived star formation rates (<1 Msun/yr). Two of our nine galaxies host AGNs, and two have kinematic disruptions to their gas that are not seen in their stellar component.…
DDO68 (UGC5340) is an unusual dwarf galaxy with extremely low gas metallicity (12+log(O/H) = 7.14) residing in the nearby Lynx-Cancer void. Despite its apparent isolation, it shows both optical and HI morphological evidence for strong tidal disturbance. Here, we study the resolved stellar populations of DDO68 using deep images from the HST archive. We determined a distance of 12.75+-0.41 Mpc using the tip of the red giant branch (TRGB). The star formation history reconstruction reveals that about 60 per cent of stars formed during the initial period of star formation, about 12-14 Gyr ago. Duri…
Voids represent a unique environment for the study of galaxy evolution, as the lower density environment is expected to result in shorter merger histories and slower evolution of galaxies. This provides an ideal opportunity to test theories of galaxy formation and evolution. Imaging of the neutral hydrogen, central in both driving and regulating star formation, directly traces the gas reservoir and can reveal interactions and signs of cold gas accretion. For a new Void Galaxy Survey (VGS), we have carefully selected a sample of 59 galaxies that reside in the deepest underdensities of geometric…
CAVITY: Calar Alto Void Integral-field Treasury surveY: II. Second public data release
Universidad de Granada（格拉纳达大学）；Instituto de Astrofísica de Andalucía - CSIC（安达卢西亚天体物理研究所-西班牙国家研究委员会）；Institut de Radioastonomie Millimétrique (IRAM)（毫米波射电天文研究所）；Université Laval（拉瓦尔大学）
