SAGAN: Spectral Analysis of Galaxy and Active galactic Nuclei

SAGAN: Spectral Analysis of Galaxy and Active galactic Nuclei#

SAGAN is a Python package for fitting astronomical spectra, specifically designed for AGN and galaxy spectra with complex emission and absorption line features.

Python Version License Code Style

Key Features#

  • Astropy Integration: All models inherit from Astropy’s modeling framework, ensuring compatibility with standard astronomical tools

  • Multiple Fitting Methods: Support for least-squares, MCMC (emcee), and nested sampling (dynesty; under development) algorithms

  • Comprehensive Line Database: Built-in database of UV/optical emission lines for AGN and galaxy analysis

  • Template Support: Iron (Fe II) templates and stellar population models included

  • Flexible Model Composition: Easily combine continuum, line, and template components

  • Professional Fitting: Parameter constraints, tying, and bounds for complex models

Quick Start#

Install SAGAN from source:

git clone https://github.com/jyshangguan/SAGAN.git
cd SAGAN
pip install -e .

Fit a simple emission line:

import numpy as np
from astropy.modeling.models import Linear1D
from sagan import Line_Gaussian
from astropy.modeling.fitting import LevMarLSQFitter

# Load your spectrum data
wave = np.linspace(4000, 7000, 1000)
flux = np.random.randn(1000) * 0.1  # Your flux data here

# Create a model: continuum + emission line
continuum = Linear1D(slope=0.0, intercept=1.0)
line = Line_Gaussian(amplitude=1.0, dv=0, sigma=200, wavec=6563, name='Halpha')
model = continuum + line

# Fit the model
fitter = LevMarLSQFitter()
fitted_model = fitter(model, wave, flux)

Contents#

User Guide:

Indices and tables#