Clues on void evolution - I. Large-scale galaxy distributions around voids (original) (raw)
Related papers
The Galaxy Population in Voids: Are All Voids the Same?
The Astrophysical Journal, 2015
The influence of under-dense environments on the formation and evolution of galaxies is studied by analysing the photometric properties of ∼ 200 galaxies residing in voids, taken from our SDSS DR10 void catalog up to z ∼ 0.055. We split void galaxies into two subsamples based on the luminosity density contrast of their host voids: 'sparse void' δ s = δ < −0.95 and 'populous void' δ p = δ > −0.87. We find that galaxies in sparse voids are less massive than galaxies in populous voids. The luminosity distribution of galaxies in populous voids follows the same distribution observed across the SDSS survey in the same redshift range. Galaxies in the sparse voids are also bluer suggesting that they may be going through a relatively slow and continuous star formation. Additionally, we find that the luminosity function of galaxies in populous voids is represented with the Schechter function whereas the same does not hold for sparse voids. Our analysis suggests that the properties of a host void plays a significant role in the formation and evolution of the void galaxies and determining the large scale evolution of voids is an important step to understand what processes regulate the evolution of galaxies.
The Distribution of Galaxies in Voids
Astronomy and Astrophysics
We investigate the distribution of normal (faint) galaxies and blue compact galaxies (BCGs) in voids by analyzing their distribution as a function of distance from the void centers and by employing nearest neighbour statistics between objects of various subsamples. We find that galaxies in voids defined by brighter galaxies tend to be concentrated close to the walls of voids in a hierarchical manner, similar to the behavior of brighter galaxies. The behavior of BCGs is in this respect similar to the one found for normal dwarf galaxies. The median nearest neighbour distance of BCGs from normal galaxies is approximately 0.7 h −1 Mpc, which indicates that these galaxies are located in outlying parts of systems of galaxies defined by normal galaxies.
Towards understanding the structure of voids in the cosmic web
Astronomy & Astrophysics, 2011
Context. According to the modern cosmological paradigm cosmic voids form in low density regions between filaments of galaxies and superclusters. Aims. Our goal is to see how density waves of different scale combine to form voids between galaxy systems of various scale. Methods. We perform numerical simulations of structure formation in cubes of size 100, 256, and 512 h −1 Mpc, with resolutions 256 3 and 512 3 particles and cells. To understand the role of density perturbations of various scale we cut power spectra at scales from 8 to 128 h −1 Mpc, using in all series identical initial random realisations. Results. We find that small haloes and short filaments form all over the simulation box, if perturbations only up to scale 8 h −1 Mpc are present. We call density waves of scale ≥ 64 h −1 Mpc as large, waves of scale ≃ 32 h −1 Mpc as medium scale, and waves of scale ≃ 8 h −1 Mpc as small scale, within a factor of 2. Voids form in regions where medium-and large-scale density perturbations combine in negative parts of waves due to the synchronisation of phases of medium-and large-scale density perturbations. In voids the growth of potential haloes (formed in the absence of large-scale perturbations) is suppressed by the combined negative sections of mediumand large-scale density perturbations, so that their densities are less than the mean density, and thus during the evolution their densities decrease.
Local and large-scale effects on the astrophysics of void galaxies
Monthly Notices of the Royal Astronomical Society
Galaxies in cosmic voids have been reported with properties related to a delayed evolution compared to the rest of the Universe. These characteristics reflect the interaction of galaxies with the environment. However, it is not clear the degree of influence of the large-scale structure on the properties of void galaxies or if these are only influenced by the low local density around them typical of these regions. In this article, we identified cosmic voids in the SDSS-DR16 and studied the g–r colour, star formation rate, and concentration of galaxies. We identified galaxy groups to characterize the local environment and studied the properties of galaxies as a function of total and stellar masses, separately analysing those in voids and the general sample. Our results show that galaxies that inhabit haloes of a given mass (below sim1013.5rmModot{\sim}10^{13.5}{\rm M}_{\odot }sim1013.5rmModot), are bluer, have a higher star formation rate and are less concentrated when the host halo is inside voids compared to oth...
Eprint Arxiv Astro Ph 9711046, 1997
The Northern Local Void is a huge underdense region of the nearby Universe situated between the Hercules, Coma and Local Superclusters. We present an investigation of the galaxy distribution in the Northern Local Void using void statistics. In particular galaxies of different morphological type and luminosity have been studied separately and void catalogues have been compiled from three different luminosity limited galaxy samples for the first time. Our approach is complementary to most other methods usually used in Large-Scale Structure studies and has the potential to detect and describe subtle structures in the galaxy distribution. We found that the resulting sets of voids form a hierarchical system: The fainter the limiting luminosity of the galaxies the smaller are the voids defined by them. Voids outlined by bright galaxies are interlaced by a fine network of faint galaxy filaments dividing them into smaller subvoids. This Void Hierarchy is an important property of the Large-Scale Structure in the Universe which constrains any realistic galaxy and structure formation scenario. In addition, this concept of Void Hierarchy may help to devise new concepts for the study of the Large-Scale Structure in the Universe.
Voids in the Large‐Scale Structure
The Astrophysical Journal, 1997
Voids are the most prominent feature of the large-scale structure of the universe. Still, they have been generally ignored in quantitative analysis of it, essentially due to the lack of an objective tool to identify the voids and to quantify them. To overcome this, we present here the void finder algorithm, a novel tool for objectively quantifying voids in the galaxy distribution. The algorithm first classifies galaxies as either wall galaxies or field galaxies. Then, it identifies voids in the wall galaxy distribution. Voids are defined as continuous volumes that do not contain any wall galaxies. The voids must be thicker than an adjustable limit, which is refined in successive iterations. In this way we identify the same regions that would be recognized as voids by the eye. Small breaches in the walls are ignored, avoiding artificial connections between neighboring voids.
The Effect of Nearby Voids on Galaxy Number Counts
2016
The size, shape and degree of emptiness of void interiors sheds light on the details of galaxy formation. A particularly interesting question is whether void interiors are completely empty or contain a dwarf population. However the nearby voids that are most conducive for dwarf searches have large angular diameters, on the order of a steradian, making it difficult to redshift-map a statistically significant portion of their volume to the magnitude limit of dwarf galaxies. As part of addressing this problem, we investigate here the usefulness of number counts in establishing the best locations to search inside nearby (d < 300 Mpc) galaxy voids, utilizing Wolf plots of log(n < m) vs. m as the basic diagnostic. To illustrate expected signatures, we consider the signature of three void profiles, "cut out", "built up", and "universal profile" carved into Monte-Carlo Schechter function models. We then investigate the signatures of voids in the Millennium Run dark matter simulation and the Sloan Digital Sky Survey. We find in all of these the evidence for cutout and built-up voids is most discernible when the void diameter is similar to the distance to its center. However the density distribution of the universal profile that is characteristic of actual voids is essentially undetectable at any distance. A useful corollary of this finding is that galaxy counts are a reliable measure of survey completeness and stellar contamination even when sampling through significant voids.
Galaxy properties from voids to clusters in the SDSS-DR4
Astronomy and Astrophysics, 2006
Aims. We investigate the environmental dependence of galaxy population properties in a complete volume-limited sample of 91566 galaxies in the redshift range 0.05 ≤ z ≤ 0.095 and with M r ≤ −20.0 (that is M * + 1.45), selected from the Sloan Digital Sky Survey (SDSS) Data Release 4 (DR4). Our aim is to search for systematic variations in the properties of galaxies with the local galaxy density. In particular, we analize how the (u − r) color index and the morphological type of galaxies (the latter evaluated through the SDSS Eclass and FracDev parameters) are related to the environment and to the luminosity of galaxies, in order to find hints that can be related to the presence of a "void" galaxy population. Methods. "Void" galaxies are identified through a highly selective criterion, which takes also into account redshift and allows us to exclude from the sample all the galaxies that are not really close to the center of underdense regions. We study the (u − r) color distribution for galaxies in different luminosity bins, and we look for correlations of color with the environment, the luminosity, and the morphological type of the galaxies. Results. We find that galaxies in underdense regions (voids) have lower luminosity (M r > −21) and are bluer than cluster galaxies. The transition from overdense to underdense environments is smooth, the fraction of late-type galaxies decreases while the fraction of early-type galaxies increases smoothly from underdense to dense environments. Conclusions. We do not find any sudden transition in the galaxy properties with density, which, according to a suggestion by Peebles , should mark the transition to a population of "void" galaxies in ΛCDM models. On the contrary, our results suggest a continuity of galaxy properties, from voids to clusters.
Cosmology with Void-Galaxy Correlations
Physical Review Letters, 2014
Galaxy bias, the unknown relationship between the clustering of galaxies and the underlying dark matter density field is a major hurdle for cosmological inference from large-scale structure. While traditional analyses focus on the absolute clustering amplitude of high-density regions mapped out by galaxy surveys, we propose a relative measurement that compares those to the underdense regions, cosmic voids. On the basis of realistic mock catalogs we demonstrate that cross-correlating galaxies and voids opens up the possibility to calibrate galaxy bias and to define a standard ruler thanks to the observable geometric nature of voids. We illustrate how the clustering of voids is related to mass compensation and show that volume-exclusion significantly reduces the degree of stochasticity in their spatial distribution. Extracting the spherically averaged distribution of galaxies inside voids from their cross-correlations reveals a remarkable concordance with the mass-density profile of voids.
Monthly Notices of the Royal Astronomical Society, 2013
Using the redshift-space distortions of void-galaxy cross-correlation function we analyse the dynamics of voids embedded in different environments. We compute the void-galaxy crosscorrelation function in the Sloan Digital Sky Survey (SDSS) in terms of distances taken along the line of sight and projected into the sky. We analyse the distortions on the cross-correlation isodensity levels and we find anisotropic isocontours consistent with expansion for large voids with smoothly rising density profiles and collapse for small voids with overdense shells surrounding them. Based on the linear approach of gravitational collapse theory we developed a parametric model of the void-galaxy redshift space cross-correlation function. We show that this model can be used to successfully recover the underlying velocity and density profiles of voids from redshift space samples. By applying this technique to real data, we confirm the twofold nature of void dynamics: large voids typically are in an expansion phase whereas small voids tend to be surrounded by overdense and collapsing regions. These results are obtained from the SDSS spectroscopic galaxy catalogue and also from semi-analytic mock galaxy catalogues, thus supporting the viability of the standard ΛCDM model to reproduce large scale structure and dynamics.