Observationnal constraints on the nature of the low redshift Lyman-alpha absorbers

V. Le Brun; J. Bergeron; P. Boisse

Home/Archive/arXiv

arXiv · astro-ph/9509146

Observationnal constraints on the nature of the low redshift Lyman-alpha absorbers

V. Le Brun·J. Bergeron·P. Boisse

View original source ↗Read source document ↗Export metadata ↓

Abstract

We present results from a spectroscopic and imaging survey of galaxies in the fields of quasars from the HST Quasar Absorption Line Key Project. The aim of this survey is to identify galaxies within 3.5' from the quasar sightline, to a limiting r-band magnitude mr = 22.5. The data are then compared to the HST homogeneous sample of Lyman-alpha-only absorbers in order to put constraints on the nature of these absorbers, and in particular on their relation to galaxies. The analysis of our sample combined with those of previous studies shows that: 1) the redshift agreements of the Ly-alpha absorber-galaxy associations cannot be due to chance coincidence; 2) there is no clear anti-correlation between the Ly-alpha rest-frame equivalent width and the impact parameter for the whole sample. Our results suggest that most Ly-alpha absorbers are not gaseous clouds that belong in a strict sense to galaxies, as is the case for MgII absorbers. The fraction of associations to the total number of galaxies at impact parameter < D as a function of D drops from 1 to 0.65 at D = 200 H50 kpc and flattens at larger values of D (> 300 H50 kpc), which leads to Ly-alpha galactic halos sizes about three times larger than the inner MgII halo region; 3) there is no correlation between the galaxy luminosity and the impact parameter. This again suggests that a significant Ly-alpha clouds do not belong to individual galaxies, but instead are distributed in the local large-scale structure. 4) the HWHM=120 km/s of the relative velocity distribution of the Ly-alpha absorber-galaxy associations is consistent with either galaxy rotation velocities or the local velocity dispersion in large-scale structures.

Explore related subjects

astro-ph

Keep this discovery

Explore connections, maps & timelines

BibTeX RIS

V. Le Brun, J. Bergeron, P. Boisse. 1995-09-28. Observationnal constraints on the nature of the low redshift Lyman-alpha absorbers. https://arxiv.org/abs/astro-ph/9509146

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related papers

arXiv2024

Deformation procedure for scalar fields in cosmology

This work offers an extension of the deformation procedure introduced in field theory to the case of standard cosmology in the presence of real scalar field in flat space-time. The procedure is shown to work for many models, which give rise to several different cosmic scenarios, evolving under the presence of first-order differential equations which solve the corresponding equations of motion very appropriately.

astro-ph↗

arXiv2023

Does Unruh radiation accelerate the universe? A novel approach to dark energy

In braneworld scenario, the brane accelerates in the bulk, and hence it perceives a thermal bulk filled with Unruh radiation. We put forward that there may be an energy exchange between Unruh radiation in the bulk and the dark matter confined to the brane, which accelerates the universe.

astro-ph↗

arXiv2023

Dark Energy is the Cosmological Quantum Vacuum Energy of Light Particles-The Axion and the Lightest Neutrino

We uncover the general mechanism producing the dark energy(DE). This is only based on well known quantum physics and cosmology. We show that the observed DE originates from the cosmological quantum vacuum of light particles which provides a continuous energy distribution able to reproduce the data. Bosons give positive contributions to the DE while fermions yield negative contributions. As usual in field theory, ultraviolet divergences are subtracted from the physical quantities. The subtractions respect the symmetries of the theory and we normalize the physical quantities to be zero for the Minkowski vacuum. The resulting finite contributions to the energy density and the pressure from the quantum vacuum grow as log a(t) where a(t) is the scale factor, while the particle contributions dilute as 1/a^3(t), as it must be for massive particles. The DE equation of state P = w(z)H turns to be w(z)<-1 with w(z) asymptotically reaching the value -1 from below.A scalar particle can produce the observed DE through its quantum cosmological vacuum provided:(i)its mass is of the order of 10^{-3} eV = 1 meV,(ii) it is very weakly coupled and (iii) it is stable on the time scale of the age of the universe. The axion vacuum thus appears as a natural candidate. The neutrino vacuum (especially the lightest mass eigenstate) can give negative contributions to the DE. We find that w(z=0) is slightly below -1 by an amount ranging from [-1.5 10^{-3}] to [-8 10^{-3}] and we predict the axion mass to be in the range between 4 and 5 meV. We find that the universe will expand in the future faster than the de Sitter universe, as an exponential in the square of the cosmic time. DE arises from the quantum vacua of light particles in FRW cosmological space time in an analogous way to the Casimir effect in Minkowski spacetime with non trivial boundaries.

astro-ph↗