Publication

The clustering of C IV and Si IV at the end of reionization. A perspective from the E-XQR-30 survey

2025

Abstract

We studied the clustering of metal absorption lines and the structures that they arise in as a function of cosmic time. We focused on the behaviour of ̧iv and ionic species. These ̧iv and absorption features are identified along a given quasar sightline. We exploited the two-point correlation function (2PCF) to investigate the clustering of these structures as a function of their separation. We utilised the E-XQR-30 data to perform a novel analysis at z>5. We also drew on literature surveys (including XQ-100) of lower redshift quasars to investigate the possible evolution of this clustering towards cosmic noon (i.e. z∼ 2-3). We find no significant evolution with redshift when considering the separation of absorbers in velocity space. Since we were comparing data across a large interval of cosmic time, we also considered the separation between absorbers in the reference frame of physical distances. In this reference frame, we find that the amplitude of the clustering increases with cosmic time for both ̧iv and on scales of $

Official source

https://infoscience.epfl.ch/entities/publication/f5b8c892-1399-412e-bf7e-e924e2568122

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2025

Abstract

Official source

https://infoscience.epfl.ch/entities/publication/f5b8c892-1399-412e-bf7e-e924e2568122

Related concepts (32)

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 decrease in wavelength and simultaneous increase in frequency and energy, is known as a negative redshift, or blueshift. The terms derive from the colours red and blue which form the extremes of the visible light spectrum.

Gravitational redshift

In physics and general relativity, gravitational redshift (known as Einstein shift in older literature) is the phenomenon that electromagnetic waves or photons travelling out of a gravitational well (seem to) lose energy. This loss of energy corresponds to a decrease in the wave frequency and increase in the wavelength, known more generally as a redshift. The opposite effect, in which photons (seem to) gain energy when travelling into a gravitational well, is known as a gravitational blueshift (a type of blueshift).

Determining the number of clusters in a data set

Determining the number of clusters in a data set, a quantity often labelled k as in the k-means algorithm, is a frequent problem in data clustering, and is a distinct issue from the process of actually solving the clustering problem. For a certain class of clustering algorithms (in particular k-means, k-medoids and expectation–maximization algorithm), there is a parameter commonly referred to as k that specifies the number of clusters to detect.

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