11.4.4. astroML.datasets.fetch_sdss_S82standards¶
-
astroML.datasets.fetch_sdss_S82standards(data_home=None, download_if_missing=True, crossmatch_2mass=False)[source]¶ Loader for SDSS stripe82 standard star catalog
- Parameters
- data_homeoptional, default=None
Specify another download and cache folder for the datasets. By default all astroML data is stored in ‘~/astroML_data’.
- download_if_missingbool, optional, default=True
If False, raise a IOError if the data is not locally available instead of trying to download the data from the source site.
- crossmatch_2mass: bool, optional, default=False
If True, return the standard star catalog cross-matched with 2mass magnitudes
- Returns
- datandarray, shape = (313859,)
record array containing sdss standard stars (see notes below)
Notes
Information on the data can be found at http://www.astro.washington.edu/users/ivezic/sdss/catalogs/stripe82.html Data is described in Ivezic et al. 2007 (Astronomical Journal, 134, 973). Columns are as follows:
RA Right-ascention of source (degrees) DEC Declination of source (degrees) RArms rms of right-ascention (arcsec) DECrms rms of declination (arcsec) Ntot total number of epochs A_r SFD ISM extinction (mags)
- for each band in (u g r i z):
Nobs_<band> number of observations in this band mmed_<band> median magnitude in this band mmu_<band> mean magnitude in this band msig_<band> standard error on the mean
(1.25 times larger for median)
mrms_<band> root-mean-square scatter mchi2_<band> chi2 per degree of freedom for mean magnitude
For 2-MASS, the following columns are added:
ra2MASS 2-mass right-ascention dec2MASS 2-mass declination J J-band magnitude Jerr J-band error H H-band magnitude Herr H-band error K K-band magnitude Kerr K-band error theta difference between SDSS and 2MASS position (arcsec)
References
Ivesic et al. ApJ 134:973 (2007)
Examples
>>> data = fetch_sdss_S82standards() >>> u_g = data['mmed_u'] - data['mmed_g'] >>> print(u_g[:4]) [-22.23500061 1.34900093 1.43799973 2.08200073]