Lyman-alpha forest

In astronomical spectroscopy, the Lyman-alpha forest is a series of absorption lines in the spectra of distant galaxies and quasars arising from the Lyman-alpha electron transition of the neutral hydrogen atom. As the light travels through multiple gas clouds with different redshifts, multiple absorption lines are formed. History The Lyman-alpha forest was first discovered in 1970 by astronomer Roger Lynds in an observation of the quasar 4C 05.34. Quasar 4C 05.34 was the farthest object observed to that date, and Lynds noted an unusually large number of absorption lines in its spectrum. He suggested that most of the absorption lines were all due to the same Lyman-alpha transition. Follow-up observations by John Bahcall and Samuel Goldsmith confirmed the presence of the unusual absorption lines, though they were less conclusive about the origin of the lines. Subsequently, the spectra of many other high-redshift quasars were observed to have the same system of narrow absorpt

About this result

This page is automatically generated and may contain information that is not correct, complete, up-to-date, or relevant to your search query. The same applies to every other page on this website. Please make sure to verify the information with EPFL's official sources.

Related publications (23)

Related publications

Related people (5)

Related people

Related units (3)

Related units

Related concepts (11)

Related concepts

Related courses (2)

Related courses

Related lectures (8)

Related lectures

Neutrino masses and cosmology with Lyman-alpha forest power spectrum

Arnaud Borde, Julien Lesgourgues

We present constraints on neutrino masses, the primordial fluctuation spectrum from inflation, and other parameters of the ACDM model, using the one-dimensional Ly alpha-forest power spectrum measured by [1] from the Baryon Oscillation Spectroscopic Survey (BOSS) of the Sloan Digital Sky Survey (SDSS-III), complemented by Planck 2015 cosmic microwave background (CMB) data and other cosmological probes. This paper improves on the previous analysis by [2] by using a more powerful set of calibrating hydrodynamical simulations that reduces uncertainties associated with resolution and box size, by adopting a more flexible set of nuisance parameters for describing the evolution of the intergalactic medium, by including additional freedom to account for systematic uncertainties, and by using Planck 2015 constraints in place of Planck 2013. Fitting Ly alpha data alone leads to cosmological parameters in excellent agreement with the values derived independently from CMB data, except for a weak tension on the scalar index n(s). Combining BOSS Ly alpha with Planck CMB constrains the sum of neutrino masses to Sigma m(nu) < 0.12 eV (95% C.L.) including all identified systematic uncertainties, tighter than our previous limit (0.15 eV) and more robust. Adding Ly alpha data to CMB data reduces the uncertainties on the optical depth to reionization tau, through the correlation of tau with sigma(8). Similarly, correlations between cosmological parameters help in constraining the tensor-toscalar ratio of primordial fluctuations r. The tension on n(s) can be accommodated by allowing for a running dn(s)/d In k. Allowing running as a free parameter in the fits does not change the limit on Sigma m(nu). We discuss possible interpretations of these results in the context of slow-roll inflation.

Iop Publishing Ltd2015

Constraint on neutrino masses from SDSS-III/BOSS Ly alpha forest and other cosmological probes

Arnaud Borde, Julien Lesgourgues

We present constraints on the parameters of the ACDM cosmological model in the presence of massive neutrinos, using the one-dimensional Ly alpha forest power spectrum obtained with the Baryon Oscillation Spectroscopic Survey (BOSS) of the Sloan Digital Sky Survey (SDSS) by Palanque-Delabrouille et al. [1], complemented by additional cosmological probes. The interpretation of the measured Ly alpha spectrum is done using a second-order Taylor expansion of the simulated power spectrum. BOSS Ly alpha data alone provide better bounds than previous Ly alpha results, but are still poorly constraining, especially for the sum of neutrino masses Sigma m(v), for which we obtain an upper bound of 1.1 eV (95% CL), including systematics for both data and simulations. Ly alpha constraints on ACDM parameters and neutrino masses are compatible with CMB bounds from the Planck collaboration [2]. Interestingly, the combination of Ly alpha with CMB data reduces the uncertainties significantly, due to very different directions of degeneracy in parameter space, leading to the strongest cosmological bound to date on the total neutrino mass, Sigma m(v) < 0.15 eV at 95% CL (with a best-fit in zero). Adding recent BAO results further tightens this constraint to Sigma m(v) < 0.14 eV at 95% CL. This bound is nearly independent of the statistical approach used, and of the different combinations of CMB and BAO data sets considered in this paper in addition to Ly alpha. Given the measured values of the two squared mass differences Delta m(2), this result tends to favor the normal hierarchy scenario against the inverted hierarchy scenario for the masses of the active neutrino species.

Iop Publishing Ltd2015

Measurement of baryon acoustic oscillation correlations at z=2.3 with SDSS DR12 Ly alpha-Forests

Timothée Guy Olivier Delubac

Here, we use flux-transmission correlations in Ly alpha forests to measure the imprint of baryon acoustic oscillations (BAO). The study uses spectra of 157,783 quasars in the redshift range 2.1

Edp Sciences S A2017

Redshift

In physics, a redshift is an increase in the wavelength, and corresponding decrease in the frequency and photon energy, of electromagnetic radiation (such as light). The opposite change, a decreas

Galaxy

A galaxy is a system of stars, stellar remnants, interstellar gas, dust, and dark matter bound together by gravity. The word is derived from

Wilkinson Microwave Anisotropy Probe

The Wilkinson Microwave Anisotropy Probe (WMAP), originally known as the Microwave Anisotropy Probe (MAP and Explorer 80), was a NASA spacecraft operating from 2001 to 2010 which measured temperatur

PHYS-402: Astrophysics IV : observational cosmology

Cosmology is the study of the structure and evolution of the universe as a whole. This course describes the principal themes of cosmology, as seen from the point of view of observations.

PHYS-424: Plasma II

This course completes the knowledge in plasma physics that students have acquired in the previous two courses, with a discussion of different applications, in the fields of magnetic confinement and controlled fusion, astrophysical and space plasmas, and societal and industrial applications.