11.4.10. astroML.datasets.fetch_sdss_specgals¶
-
astroML.datasets.fetch_sdss_specgals(data_home=None, download_if_missing=True)[source]¶ Loader for SDSS Galaxies with spectral information
- 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_missingoptional, 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.
- Returns
- datarecarray, shape = (661598,)
record array containing pipeline parameters
Notes
These were compiled from the SDSS database using the following SQL query:
SELECT G.ra, G.dec, S.mjd, S.plate, S.fiberID, --- basic identifiers --- basic spectral data S.z, S.zErr, S.rChi2, S.velDisp, S.velDispErr, --- some useful imaging parameters G.extinction_r, G.petroMag_r, G.psfMag_r, G.psfMagErr_r, G.modelMag_u, modelMagErr_u, G.modelMag_g, modelMagErr_g, G.modelMag_r, modelMagErr_r, G.modelMag_i, modelMagErr_i, G.modelMag_z, modelMagErr_z, G.petroR50_r, G.petroR90_r, --- line fluxes for BPT diagram and other derived spec. parameters GSL.nii_6584_flux, GSL.nii_6584_flux_err, GSL.h_alpha_flux, GSL.h_alpha_flux_err, GSL.oiii_5007_flux, GSL.oiii_5007_flux_err, GSL.h_beta_flux, GSL.h_beta_flux_err, GSL.h_delta_flux, GSL.h_delta_flux_err, GSX.d4000, GSX.d4000_err, GSE.bptclass, GSE.lgm_tot_p50, GSE.sfr_tot_p50, G.objID, GSI.specObjID INTO mydb.SDSSspecgalsDR8 FROM SpecObj S CROSS APPLY dbo.fGetNearestObjEQ(S.ra, S.dec, 0.06) N, Galaxy G, GalSpecInfo GSI, GalSpecLine GSL, GalSpecIndx GSX, GalSpecExtra GSE WHERE N.objID = G.objID AND GSI.specObjID = S.specObjID AND GSL.specObjID = S.specObjID AND GSX.specObjID = S.specObjID AND GSE.specObjID = S.specObjID --- add some quality cuts to get rid of obviously bad measurements AND (G.petroMag_r > 10 AND G.petroMag_r < 18) AND (G.modelMag_u-G.modelMag_r) > 0 AND (G.modelMag_u-G.modelMag_r) < 6 AND (modelMag_u > 10 AND modelMag_u < 25) AND (modelMag_g > 10 AND modelMag_g < 25) AND (modelMag_r > 10 AND modelMag_r < 25) AND (modelMag_i > 10 AND modelMag_i < 25) AND (modelMag_z > 10 AND modelMag_z < 25) AND S.rChi2 < 2 AND (S.zErr > 0 AND S.zErr < 0.01) AND S.z > 0.02 --- end of query ---
Examples
>>> from astroML.datasets import fetch_sdss_specgals >>> data = fetch_sdss_specgals() >>> # number of objects in dataset >>> data.shape (661598,) >>> # first five column names >>> data.dtype.names[:5] ('ra', 'dec', 'mjd', 'plate', 'fiberID') >>> # first three RA values >>> print(data['ra'][:3]) [ 146.71419105 146.74414186 146.62857334] >>> # first three declination values >>> print(data['dec'][:3]) [-1.04127639 -0.6522198 -0.7651468 ]