Large Scale Structure in Absorption: Gas within and around Galaxy Voids

Abstract

We investigate the properties of the HI Ly-a absorption systems (Ly-a forest) within and around galaxy voids at z<0.1. We find a significant excess (>99% c.l.) of Ly-a systems at the edges of galaxy voids with respect to a random distribution, on ~5 h^{-1} Mpc scales. We find no significant difference in the number of systems inside voids with respect to the random expectation. We report differences between both column density (N_{HI}) and Doppler parameter (b_{HI}) distributions of Ly-a systems found inside and at the edge of galaxy voids at the >98% and >90% c.l. respectively. Low density environments (voids) have smaller values for both N_{HI} and b_{HI} than higher density ones (edges of voids). These trends are theoretically expected and also found in GIMIC, a state-of-the-art hydrodynamical simulation. Our findings are consistent with a scenario of at least three types of Ly-alpha: (1) containing embedded galaxies and so directly correlated with galaxies (referred as `halo-like'), (2) correlated with galaxies only because they lie in the same over-dense LSS, and (3) associated with under-dense LSS with a very low auto-correlation amplitude (~ random) that are not correlated with luminous galaxies. We argue the latter arise in structures still growing linearly from the primordial density fluctuations inside galaxy voids that have not formed galaxies because of their low densities. We estimate that these under-dense LSS absorbers account for 25-30% +- 6% of the current Ly-a population (N_{HI} > 10^{12.5} cm^{-2}) while the other two types account for the remaining 70-75% +- 12%. Assuming that only N_{HI} > 10^{14} cm^{-2} systems have embedded galaxies nearby, we have estimated the contribution of the `halo-like' Ly-a to be ~12-15% +- 4% and consequently ~55-60% +- 13% of the Ly-a systems to be associated with the over-dense LSS.

To be accepted by MNRAS (reviewed); 18 pages, 8 figures, 4 tables

References in corpus (11)

• The effect of photo-ionization on the cooling rates of enriched, astrophysical plasmas
• Chemical enrichment in cosmological, smoothed particle hydrodynamics simulations
• The Low-z Intergalactic Medium. III. HI and Metal Absorbers at z<0.4
• The Aspen--Amsterdam Void Finder Comparison Project
• Physical Properties, Baryon Content, and Evolution of the LyαForest: New Insights from High Resolution Observations at z < 0.4
• The emptiness of voids: yet another over-abundance problem for the LCDM model
• Galaxy Clusters in the Line of Sight to Background Quasars: I. Survey Design and Incidence of MgII Absorbers at Cluster Redshifts
• Continuous statistics of the Lyman-alpha forest at 0 < z < 1.6: the mean flux, flux distribution, and autocorrelation from HST FOS spectra
• Cross correlation of Lyman-alpha absorbers with gas-rich galaxies
• The Metallicity of Intergalactic Gas in Cosmic Voids
• The association between gas and galaxies II: The 2-point correlation function

Cited by in corpus (24)

• Quasars Probing Quasars VI. Excess HI Absorption Within One Proper Mpc of z~2 Quasars
• A Deep Search For Faint Galaxies Associated With Very Low-redshift C IV Absorbers: III. The Mass- and Environment-dependent Circumgalactic Medium
• Photometric Properties of Void Galaxies in the Sloan Digital Sky Survey DR7 Data Release
• The Properties of the Circumgalactic Medium in Red and Blue Galaxies: Results from the COS-GASS+COS-Halos Surveys
• Probing the intra-group medium of a z = 0.28 galaxy group
• On the connection between the intergalactic medium and galaxies: The HI-galaxy cross-correlation at z < 1
• Towards the statistical detection of the warm-hot intergalactic medium in inter-cluster filaments of the cosmic web
• Revealing the Dark Threads of the Cosmic Web
• A Detection of $z$~2.3 Cosmic Voids from 3D Lyman-$\alpha$ Forest Tomography in the COSMOS Field
• Quasar Sightline and Galaxy Evolution (QSAGE) Survey - I. The Galaxy Environment of OVI Absorbers up to z=1.4 around PKS 0232-04
• Updated void catalogs of the SDSS DR7 main sample
• The COS Absorption Survey of Baryon Harbors: The Galaxy Database and Cross-Correlation Analysis of OVI Systems
• The VLT LBG Redshift Survey - VI. Mapping HI in the proximity of $z\sim 3$ LBGs with X-Shooter
• Warm-hot gas in groups and galaxies toward H2356-309
• On the relation between Lya absorbers and local galaxy filaments
• CGM${}^2$ $+$ CASBaH: The Mass Dependence of H~I Ly$\alpha$-Galaxy Clustering and the Extent of the CGM
• Kinematics of MgII Absorbers from the Redshift-space Distortion Around Massive Quiescent Galaxies
• A Global Census of Metals in the Universe
• Stochastic Order Redshift Technique (SORT): a simple, efficient and robust method to improve cosmological redshift measurements
• Considering light-matter interactions in the Friedmann equations
• Answers from the void: VIDE and its applications
• A positive correlation between broad HI Ly$\alpha$ absorptions and local overdensities of galaxies
• The intergalactic medium in the cosmic web
• Studying the gaseous outskirts of galaxy groups with coherent Ly alpha absorption patterns