https://github.com/kaykeigh-zz/galaxy-environment

python package to measure the environment of galaxies
https://github.com/kaykeigh-zz/galaxy-environment

astronomy astrophysics cosmology

Last synced: 2 months ago
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python package to measure the environment of galaxies

• Host: GitHub
• URL: https://github.com/kaykeigh-zz/galaxy-environment
• Owner: kaykeigh-zz
• License: apache-2.0
• Created: 2021-06-25T15:07:17.000Z (over 3 years ago)
• Default Branch: master
• Last Pushed: 2021-10-10T23:22:05.000Z (about 3 years ago)
• Last Synced: 2023-03-01T23:43:34.950Z (almost 2 years ago)
• Topics: astronomy, astrophysics, cosmology
• Language: Jupyter Notebook
• Homepage:
• Size: 12.2 MB
• Stars: 2
• Watchers: 1
• Forks: 1
• Open Issues: 0
• Metadata Files:
  • Readme: README.md
  • License: LICENSE

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README

        
# Building an environmental catalog for galaxies

**Author**: Kayleigh Meneghini | **Email**: [email protected]

## How to use

This package is available on [PyPi](https://pypi.org/project/galaxy-environment/).

For more details, please check this [tutorial](https://github.com/kaykeigh/galaxy-environment/blob/master/tutorial/Tutorial.ipynb), using [S-PLUS](https://arxiv.org/pdf/1907.01567.pdf) data.

```

# Installing 

pip install galaxy-environment

```

```

# import 

from galaxy_environment import environment

```

### Any doubts about this package, please write to [email protected]

-------------------------------------------------------------------------------------------------------------------

## Introduction 

The environment has a decisive role in how galaxies evolve. We observed a strong correlation between galaxy properties such as color, morphology and their environment. However, the definition of environment makes this type of study non-trivial, after all, we can consider the local environment, as the association of a central galaxy and its satellites, or on larger scales, groups and clusters of galaxies.

There are two wide methods used to define the galactic environment, these are: **Nearest Neighbors and Fixed Apertures**.

In this package I have implemented the calculation of environmental estimators by these two methods, using the Python routines developed by Wright (2006) for calculating distances in cosmology.

## Method 1: Nearest Neighbors

The principle of Nearest Neighbors is that galaxies with closest neighbors are in denser environments and, therefore, have higher density fields. 

This method defines the galactic environment using a variable scale, depending on the number of neighbors of each galaxy.

For each galaxy in the sample, values for k are chosen, this being the number of neighbors and calculate the distance to each of them around an interval of z.

## Method 2: Fixed Apertures

This method, unlike the previous one, defines a scale for the environment around a fixed area or volume for each galaxy. 

So, the more galaxies within that area or volume, the denser the environment. 

## Method 3: Bayesian density estimator

An alternative method proposed by [Ivezic et. al (2005)](https://iopscience.iop.org/article/10.1086/427392/pdf), considering distances to *all* K neighbors instead of only the distance to the K-th nearest neighbor