<p>As we all know, the distribution of galaxies, which depend on the spatial coordinates, can help us understand the large-scale structure of the Universe. We can measure the distribution of galaxies from the Sky Survey Project directly, or examine it from the Hydro/N-body simulations.</p>
<p>My question is that if there are any observables that just depend on the distance to us, i.e. the scale. If so, such observables are one-dimensional.</p>

CC BY-SA 4.0
2021-07-11T22:40:30.477Z
The Lyman α forest?
pela
CC BY-SA 4.0
2021-07-12T00:39:58.693Z
@pela Are there any others?
Wang Yun
CC BY-SA 4.0
2021-07-12T01:50:25.877Z
I am not sure if this matches your criteria, but the frequency dispersion ([1](https://en.wikipedia.org/wiki/Dispersion_relation), [2](https://en.wikipedia.org/wiki/Dispersion_(optics)), [3](https://en.wikipedia.org/wiki/Dielectric#Dielectric_dispersion), [4](https://en.wikipedia.org/wiki/Plasma_oscillation#'Warm'_electrons)) of [Fast Radio Bursts](https://en.wikipedia.org/wiki/Fast_radio_burst) or FRB's depends on distance, and is used as a measure of that distance. Right now statistics are very low so it would probably not be useful to show clustering.
uhoh
CC BY-SA 4.0
2021-07-12T01:50:51.863Z
cf. [Just how fast is a Fast Radio Burst thought to be?](https://astronomy.stackexchange.com/q/29487/7982) and [Do ASKAP and ALMA have “fast dump” interferometric modes? Can they see and perhaps report Fast Radio Bursts in real time?](https://astronomy.stackexchange.com/q/40664/7982)
uhoh
CC BY-SA 4.0
2021-07-20T12:35:29.727Z
You could also consider looking for other absorbers in background spectra than just the Lya forest, e.g. DLAs. But these are rare enough that you typically only get one or two, so could hardly be called "clustering analysis". Most lines of sight through the Universe contain only one or a few galaxies. If you want to study clustering, you need to have enough clustering objects to study. In a 1D line of sight, that basically restricts you to diffuse intergalactic gas clouds, i.e. the Lya forest.
pela
CC BY-SA 4.0
2021-07-20T12:37:38.533Z
But with _many_ adjacent 1D lines of sight, such as offered by integral field spectroscopy, you can study galaxy clustering (see e.g. the recent paper by [Herrero Alonso et al. (2021)](https://arxiv.org/abs/2107.03723)).
pela
<cosmology><observable-universe><n-body-simulations>
What are the one-dimensional observables that can reveal the matter clustering properties of the Universe?
Wang Yun
# What are the one-dimensional observables that can reveal the matter clustering properties of the Universe?

(Asked by: username_0 on 2021-07-11)

As we all know, the distribution of galaxies, which depend on the spatial coordinates, can help us understand the large-scale structure of the Universe. We can measure the distribution of galaxies from the Sky Survey Project directly, or examine it from the Hydro/N-body simulations.

My question is that if there are any observables that just depend on the distance to us, i.e. the scale. If so, such observables are one-dimensional.

**Tags:** cosmology, observable-universe, n-body-simulations
> **Comments:**
> **username_1**: The Lyman α forest?  
> **username_0**: @pela Are there any others?  
> **username_2**: I am not sure if this matches your criteria, but the frequency dispersion ([1](https://en.wikipedia.org/wiki/Dispersion_relation), [2](https://en.wikipedia.org/wiki/Dispersion_(optics)), [3](https://en.wikipedia.org/wiki/Dielectric#Dielectric_dispersion), [4](https://en.wikipedia.org/wiki/Plasma_oscillation#'Warm'_electrons)) of [Fast Radio Bursts](https://en.wikipedia.org/wiki/Fast_radio_burst) or FRB's depends on distance, and is used as a measure of that distance. Right now statistics are very low so it would probably not be useful to show clustering.  
> **username_2**: cf. [Just how fast is a Fast Radio Burst thought to be?](https://astronomy.stackexchange.com/q/29487/7982) and [Do ASKAP and ALMA have “fast dump” interferometric modes? Can they see and perhaps report Fast Radio Bursts in real time?](https://astronomy.stackexchange.com/q/40664/7982)  
> **username_1**: You could also consider looking for other absorbers in background spectra than just the Lya forest, e.g. DLAs. But these are rare enough that you typically only get one or two, so could hardly be called "clustering analysis". Most lines of sight through the Universe contain only one or a few galaxies. If you want to study clustering, you need to have enough clustering objects to study. In a 1D line of sight, that basically restricts you to diffuse intergalactic gas clouds, i.e. the Lya forest.  
> **username_1**: But with _many_ adjacent 1D lines of sight, such as offered by integral field spectroscopy, you can study galaxy clustering (see e.g. the recent paper by [Herrero Alonso et al. (2021)](https://arxiv.org/abs/2107.03723)).  

---

## 0 answers

