A package to inquire empirical extinction or reddening coefficients from far-ultraviolet (UV) to the mid-infrared (IR)
Project description
extinction_coefficient
extinction_coefficient is a astronomy Python package to provide empirical extinction or reddening coefficients from far-ultraviolet (UV) to the mid-infrared (IR). (Zhang & Yuan, 2022)
For a given band a, the extinction coefficient is defined as E(a)/E(B-V), i.e. extinction in a band relative to E(B−V); Similarly, for a given color a-b, the reddening coefficient is defined as E(a-b)/E(B-V).
Our coefficients are mostly valid in the extinction range of 0-0.5 mag and the temperature range of 4000-10000 K. But note that the temperature range varies depending on the band. No extrapolation for out-of-range input values, but rather assignment of boundary values.
Available photometric surveys and passband names
- GALEX passbands: "FUV", "NUV";
- Pan-STARRS 1 passbands: "g", "r", "i", "z", "y";
- SDSS passbands: "u'", "g'", "r'", "i'", "z'";
- Gaia DR3 passbands: "BP", "G", "RP";
- 2MASS passbands: "J", "H", "Ks";
- WISE passbands: "W1", "W2", "W3", "W4".
How to Install
Using pip
# from PyPI (recommmand)
pip install extinction_coefficient
# from the master trunk on the repository, considered developmental code
pip install git+https://github.com/vnohhf/extinction_coeffcient.git
From source
extinction_coefficient can be installed from the source code after downloading it from the git repo (https://github.com/vnohhf/extinction_coeffcient/):
python setup.py install
Quick Start
To get a single value extinction or reddening coefficients obtained when temperature and extinction are not considered, just put mode = 'simple':
from extinction_coefficient import extinction_coefficient
extinction_coefficient('g', mode='simple')
extinction_coefficient('BP-RP', mode='simple')
extinction_coefficient(["BP-RP","FUV-g"], mode='simple')
To obtain extinction or reddening coefficients for (a group of) specific Teff and E(B-V):
Band = 'BP'
EBV = 0.3
Teff = [5000, 6000]
extinction_coefficient(Band,EBV=EBV,Teff=Teff)
Band = np.array(["BP-RP","FUV-g","y-H","u'-W2"])
EBV = [0.1, 0.1, 0.3, 0.5]
Teff = 5500
extinction_coefficient(Band,EBV=EBV,Teff=Teff)
If Teff is unknown in advance, the observed (BP-RP) color can be entered as a substitute. This program first makes a rough reddening correction to the observed (BP-RP) and then converts them to Teff using an empirical polynomial relationship between intrinsic color (BP-RP)0 and Teff. This allows the exact reddening factor to be obtained using Teff, and then the procedure iterates once.
Band = ["BP-RP","FUV-g","i'-z'"]
EBV = [0.1, 0.3, 0.5]
BP_RP = np.array([0.3, 0.6, 1.2])
extinction_coefficient(Band,EBV=EBV,BP_RP=BP_RP)
API
extinction_coefficient(Band,EBV=None,BP_RP=None,Teff=None,mode='func')
Args:
Band: str or array-like, shape (n, )
The passband or color index. If color index are entered, '-' need to be used to connect
the two passband name strings (e.g. "BP-RP"). There support GALEX passbands: "FUV", "NUV";
Pan-STARRS 1 passbands: "g", "r", "i", "z", "y";
SDSS passbands: "u'", "g'", "r'", "i'", "z'";
Gaia DR3 passbands: "BP", "G", "RP";
2MASS passbands: "J", "H", "Ks";
WISE passbands: "W1", "W2", "W3", "W4";
EBV: float or array-like, shape (n, ), optional
The E(B-V), in magnitude.
BP_RP: float or array-like, shape (n, ), optional
The observed (BP-RP) color index.
Teff: float or array-like, shape (n, ), optional
The effective temperature, in Kelvins.
mode: {'func', 'simple'} (default: 'func')
The calculate mode of extinction or reddening coefficients. Possible values:
'func': interpolation results on functions of Teff and E(B-V).
'simple': single value coefficients obtained when temperature and extinction are not considered.
Returns: float or array-like, shape (n, )
Empirical extinction or reddening coefficients. Has the largest shape as the input obj:`Band`, obj:`EBV`,
obj:`BP_RP`, or obj:`Teff`.
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