HostSub_GP

HostSub_GP is a Python package designed for precise removal of host galaxy contamination in transient longslit spectroscopy. By utilizing archival images of the host galaxies, HostSub_GP constructs a robust 2D model of the galaxy spectrum using Gaussian Processes (GPs). This advanced modeling enables the accurate recovery of flux from faint extragalactic transients, even when superimposed on a bright host galaxy background.

Users are recommended to use PypeIt for basic image processing, and the spec2d data products are naturally adopted as the input of HostSub_GP. Please raise an issue if you would like to post-process the data products of your favorate pipeline with HostSub_GP.

Installation

Pull the Repository

git clone https://github.com/slowdivePTG/HostSub_GP.git
cd HostSub_GP

Set up a Clean Environment

For venv users:

python3 -m venv .venv
source .venv/bin/activate

For conda users:

conda create -n HostSub_GP python=3.12
conda activate HostSub_GP

Install via pip

pip install .

Optional Dependencies

The package includes optional dependencies that can be installed as needed:

• PypeIt integration: For working with PypeIt data products

  pip install ".[pypeit]"

Note: PypeIt is an optional dependency. If you plan to use PypeIt's spec2d data products as input, install with the pypeit extra as shown above.

Citation

If you make use of HostSub_GP in your research, please cite the following publication:

• Liu & Miller, 2025, arXiv:2508.15278.