/usr/lib/python3/dist-packages/astroML/datasets/tools/sdss_fits.py is in python3-astroml 0.3-6.
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Tools to download and process SDSS fits files.
More information can be found at
http://www.sdss.org/dr7/products/spectra/index.html
"""
import gc # garbage collection
import numpy as np
from scipy.ndimage.filters import gaussian_filter1d, uniform_filter1d
from scipy import interpolate
from . import download_with_progress_bar
# This is the URL of the sdss fits spectra
FITS_FILENAME = 'spSpec-%(mjd)05i-%(plate)04i-%(fiber)03i.fit'
SDSS_URL = ('http://das.sdss.org/spectro/1d_26/%(plate)04i/'
'1d/spSpec-%(mjd)05i-%(plate)04i-%(fiber)03i.fit')
# lines used to generate line-index labeling
LINES = dict(Ha=6564.61,
Hb=4862.68,
OI=6302.05,
OIII=5008.24,
NIIa=6549.86,
NIIb=6585.27,
SIIa=6718.29,
SIIb=6732.67)
def sdss_fits_url(plate, mjd, fiber):
"""Return the URL of the spectrum FITS file"""
return SDSS_URL % dict(plate=plate, mjd=mjd, fiber=fiber)
def sdss_fits_filename(plate, mjd, fiber):
"""Return the name of the spectrum FITS file"""
return FITS_FILENAME % dict(plate=plate, mjd=mjd, fiber=fiber)
spec_cln_dict = ['SPEC_UNKNOWN',
'SPEC_STAR',
'SPEC_GALAXY',
'SPEC_QSO',
'SPEC_HIZ_QSO', # high redshift QSO, z>2.3
'SPEC_SKY',
'STAR_LATE', # Type M or later (molecular bands dominate)
'GAL_EM'] # emission line galaxy
class SDSSfits(object):
"""A class to open and interact with fits files from SDSS
Parameters
----------
buf : string or file buffer (optional)
file path, buffer, or url of SDSS spectra fits file
if None, then initialize an empty instance.
Notes
-----
This class only provides access to a subset of the information available
in the sdss spectra fits file. The raw fits data can be accessed using
the fits object directly. This can be found in the attribute
``hdulist``. For details, please refer to the data description:
http://www.sdss.org/dr7/dm/flatFiles/spSpec.html
"""
def __init__(self, source=None):
if source is None:
pass
elif isinstance(source, str):
if source.startswith('http://'):
self._load_fits_url(source)
else:
self._load_fits_file(source)
else:
self._load_fits_file(source)
def _load_fits_url(self, url):
# fits is an optional dependency: don't import globally
from astropy.io import fits
buffer = download_with_progress_bar(url, return_buffer=True)
self._initialize(fits.open(buffer))
def _load_fits_file(self, file_or_buffer):
# fits is an optional dependency: don't import globally
from astropy.io import fits
self._initialize(fits.open(file_or_buffer))
def _initialize(self, hdulist):
data = hdulist[0].data
self.name = hdulist[0].header['NAME']
self.spec_cln = hdulist[0].header['SPEC_CLN']
self.coeff0 = hdulist[0].header['COEFF0']
self.coeff1 = hdulist[0].header['COEFF1']
self.z = hdulist[0].header['Z']
self.zerr = hdulist[0].header['Z_ERR']
self.zconf = hdulist[0].header['Z_CONF']
self.spectrum = data[0]
self.spectrum_cont = data[1]
self.error = data[2]
self.mask = data[3]
self.large_err = self.error.max() * 2
self.hdulist = hdulist
def get_line_ew(self, wavelength):
i = np.where(abs(self.hdulist[2].data['restWave'] - wavelength) < 1)
return self.hdulist[2].data['ew'][i]
def __del__(self):
if hasattr(self, 'hdulist'):
del self.hdulist
gc.collect()
def copy(self):
snew = self.__class__()
for param in ['name', 'spec_cln', 'coeff0', 'coeff1',
'z', 'zerr', 'zconf', 'spectrum', 'spectrum_cont',
'error', 'large_err', 'mask', 'hdulist']:
setattr(snew, param, getattr(self, param))
return snew
def restframe(self):
snew = self.copy()
snew.coeff0 = self.coeff0_restframe()
snew.z = 0
return snew
def __len__(self):
return len(self.spectrum)
def log_w_min(self, i=None):
"""
if i is specified, return log_w_min of bin i
otherwise, return log_w_min of the spectrum
"""
if i is None:
i = 0
return self.coeff0 + (i - 0.5) * self.coeff1
def log_w_max(self, i=None):
"""
if i is specified, return log_w_max of bin i
otherwise, return log_max of the spectrum
"""
if i is None:
i = len(self) - 1
return self.coeff0 + (i + 0.5) * self.coeff1
def w_min(self, i=None):
return 10 ** self.log_w_min(i)
def w_max(self, i=None):
return 10 ** self.log_w_max(i)
def coeff0_restframe(self):
return self.coeff0 - np.log10(1 + self.z)
def wavelength(self, restframe=False):
"""
return the wavelength of the spectrum in angstroms
"""
if restframe:
coeff0 = self.coeff0_restframe()
else:
coeff0 = self.coeff0
return 10 ** (coeff0 + self.coeff1 * np.arange(len(self.spectrum)))
def compute_mask(self, frac=0.5, filtwidth=5):
"""
return a mask showing where noise spikes to frac over the local
background
"""
smoothed_noise = gaussian_filter1d(self.error, filtwidth)
mask = ((self.error >= (1 + frac) * smoothed_noise)
| (self.error <= 0)
| (self.error >= self.large_err)
| (self.spectrum == 0))
mask_filtered = uniform_filter1d(mask.astype(float),
max(3, filtwidth))
return mask_filtered > 0.5 / filtwidth
def rebin(self, rebin_coeff0, rebin_coeff1, rebin_length):
"""Rebin the spectrum to a new grid.
Parameters
----------
rebin_coeff0: float
log minimum wavelength
rebin_coeff1: float
log wavelength bin width
rebin_length: int
number of bins
Returns
-------
S_new: SDSSfits object
The new spectrum, rebinned to the desired wavelength binning
"""
snew = self.copy()
snew.spectrum = np.zeros(rebin_length)
snew.error = np.zeros(rebin_length)
snew.coeff0 = rebin_coeff0
snew.coeff1 = rebin_coeff1
N_old = len(self.spectrum)
N_new = len(snew.spectrum)
log_w_old = self.coeff0 + (np.arange(N_old + 1) - 0.5) * self.coeff1
log_w_new = snew.coeff0 + (np.arange(N_new + 1) - 0.5) * snew.coeff1
# Perform the interpolation. We'll interpolate the cumulative sum
# so that the total flux of the spectrum is conserved.
# interpolate spectrum
spec_cuml_old = self.spectrum.cumsum()
tck = interpolate.splrep(log_w_old, np.hstack(([0], spec_cuml_old)))
spec_cuml_new = interpolate.splev(log_w_new, tck)
spec_cuml_new[log_w_new >= log_w_old[-1]] = log_w_old[-1]
spec_cuml_new[log_w_new <= log_w_old[0]] = 0
snew.spectrum = np.diff(spec_cuml_new)
snew.spectrum *= self.coeff1 / snew.coeff1
# interpolate error
err_cuml_old = self.error.cumsum()
tck = interpolate.splrep(log_w_old, np.hstack(([0], err_cuml_old)))
err_cuml_new = interpolate.splev(log_w_new, tck)
err_cuml_new[log_w_new >= log_w_old[-1]] = log_w_old[-1]
err_cuml_new[log_w_new <= log_w_old[0]] = 0
snew.error = np.diff(err_cuml_new)
snew.error *= self.coeff1 / snew.coeff1
return snew
def _get_line_strength(self, line):
lam = LINES.get(line)
if lam is None:
lam1 = LINES.get(line + 'a')
ind1 = np.where(abs(self.hdulist[2].data['restWave']
- lam1) < 1)[0]
lam2 = LINES.get(line + 'b')
ind2 = np.where(abs(self.hdulist[2].data['restWave']
- lam2) < 1)[0]
if len(ind1) == 0:
s1 = h1 = 0
nsig1 = 0
else:
s1 = self.hdulist[2].data['sigma'][ind1]
h1 = self.hdulist[2].data['height'][ind1]
nsig1 = self.hdulist[2].data['nsigma'][ind1]
if len(ind2) == 0:
s2 = h2 = 0
nsig2 = 0
else:
s2 = self.hdulist[2].data['sigma'][ind2]
h2 = self.hdulist[2].data['height'][ind2]
nsig2 = self.hdulist[2].data['nsigma'][ind2]
strength = s1 * h1 + s2 * h2
nsig = max(nsig1, nsig2)
else:
ind = np.where(abs(self.hdulist[2].data['restWave'] - lam) < 1)[0]
if len(ind) == 0:
strength = 0
nsig = 0
else:
s = self.hdulist[2].data['sigma'][ind]
h = self.hdulist[2].data['height'][ind]
nsig = self.hdulist[2].data['nsigma'][ind]
strength = s * h
return strength, nsig
def lineratio_index(self, indicator='NII'):
"""Return the line ratio index for the given galaxy.
This is the index used in Vanderplas et al 2009, and makes use
of line-ratio fits from Kewley et al 2001
Parameters
----------
indicator: string ['NII'|'OI'|'SII']
The emission line to use as an indicator
Returns
-------
cln: integer
The classification of the spectrum based on SDSS pipeline and
the line ratios.
0 : unknown (SPEC_CLN = 0)
1 : star (SPEC_CLN = 1)
2 : absorption galaxy (H-alpha seen in absorption)
3 : normal galaxy (no significant H-alpha emission or absorption)
4 : emission line galaxies (below line-ratio curve)
5 : narrow-line QSO (above line-ratio curve)
6 : broad-line QSO (SPEC_CLN = 3)
7 : Sky (SPEC_CLN = 4)
8 : Hi-z QSO (SPEC_CLN = 5)
9 : Late-type star (SPEC_CLN = 6)
10 : Emission galaxy (SPEC_CLN = 7)
ratios: tuple
The line ratios used to compute this
"""
assert indicator in ['NII', 'OI', 'SII']
if self.spec_cln < 2:
return self.spec_cln, (0, 0)
elif self.spec_cln > 2:
return self.spec_cln + 3, (0, 0)
strength_Ha, nsig_Ha = self._get_line_strength('Ha')
strength_Hb, nsig_Hb = self._get_line_strength('Hb')
if nsig_Ha < 3 or nsig_Hb < 3:
return 3, (0, 0)
if strength_Ha < 0 or strength_Hb < 0:
return 2, (0, 0)
# all that's left is choosing between 4 and 5
# we do this based on line-ratios
strength_I, nsig_I = self._get_line_strength(indicator)
strength_OIII, nsig_OIII = self._get_line_strength('OIII')
log_OIII_Hb = np.log10(strength_OIII / strength_Hb)
I_Ha = np.log10(strength_I / strength_Ha)
if indicator == 'NII':
if I_Ha >= 0.47 or log_OIII_Hb >= log_OIII_Hb_NII(I_Ha):
return 5, (I_Ha, log_OIII_Hb)
else:
return 4, (I_Ha, log_OIII_Hb)
elif indicator == 'OI':
if I_Ha >= -0.59 or log_OIII_Hb >= log_OIII_Hb_OI(I_Ha):
return 5, (I_Ha, log_OIII_Hb)
else:
return 4, (I_Ha, log_OIII_Hb)
else:
if I_Ha >= 0.32 or log_OIII_Hb >= log_OIII_Hb_SII(I_Ha):
return 5, (I_Ha, log_OIII_Hb)
else:
return 4, (I_Ha, log_OIII_Hb)
#----------------------------------------------------------------------
# Empirical fits from Kewley et al 2001
def log_OIII_Hb_NII(log_NII_Ha, eps=0):
return 1.19 + eps + 0.61 / (log_NII_Ha - eps - 0.47)
def log_OIII_Hb_OI(log_OI_Ha, eps=0):
return 1.33 + eps + 0.73 / (log_OI_Ha - eps + 0.59)
def log_OIII_Hb_SII(log_SII_Ha, eps=0):
return 1.30 + eps + 0.72 / (log_SII_Ha - eps - 0.32)
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