【SDSS】SQL search through SDSS website

This is just a note from my work.

SDSS search website:
      http://www.sdss3.org/dr10/
      http://classic.sdss.org/dr7/
  DR10包括DR8和DR9, 但是DR7以及之前的结果都需要在DR7里面搜索。
(1) search particular objects
  http://data.sdss3.org/bulkSpectra/
(2) search objects with certain criterion
  http://skyservice.pha.jhu.edu/casjobs/default.aspx


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          DR10
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commands
search at website http://skyserver.sdss3.org/CasJobs/MyDB.aspx or from individual sites.
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http://skyserver.sdss3.org/dr10/en/help/docs/realquery.aspx
-- a) Finding galaxies by their emission lines:
-- This query selects galaxy spectra with high internal reddening,
-- as measured by the standard Balmer decrement technique. It
-- makes use of the galSpec tables for the measurements of
-- galaxy lines. In this case we use galSpecLine, which has
-- emission line measurements.

SELECT
s.specObjID, s.plate, s.fiberid, s.mjd, s.z, s.zwarning,
g.h_beta_flux, g.h_beta_flux_err,
g.h_alpha_flux, g.h_alpha_flux_err,
g.oiii_5007_flux, g.oiii_5007_flux_err,
g.oiii_5007_eqw
FROM GalSpecLine AS g
  JOIN SpecObj AS s ON s.specobjid = g.specobjid
WHERE
  --h_alpha_flux > h_alpha_flux_err*5
  --AND h_beta_flux > h_beta_flux_err*5
  --AND h_beta_flux_err > 0
  --AND h_alpha_flux > 10.*h_beta_flux
  oiii_5007_flux > oiii_5007_flux_err*5
  AND oiii_5007_eqw > 600.
  AND s.class = 'GALAXY'
  AND s.zwarning = 0

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          DR7
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http://cas.sdss.org/dr7/en/tools/search/sql.asp

SELECT
G.objId, S.plate, S.fiberID, S.mjd, S.z,  L1.ew,L1.ewerr, L2.ew,L2.ewerr,L1.ew*L1.continuum,L1.ewerr*L1.continuum

FROM Galaxy as G
   JOIN SpecObj as S ON G.objId=S.bestObjId
   JOIN SpecLine as hL1 ON S.specObjId=L1.specObjId
   JOIN SpecLine as L2 ON S.specObjId=L2.specObjId  
   JOIN SpecLine as Lb ON S.specObjId=Lb.specObjId
WHERE
     L1.LineId = 5008
     and L1.ew > 1000.
     and L1.ew/L1.ewerr > 3.
     and L2.LineId =6565
     and Lb.LineId =4863
     --and log10( (L1.ew*L1.continuum)/(Lb.ew*Lb.continuum) ) < 0.75


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Check image:
   http://cas.sdss.org/dr7/en/tools/chart/list.asp
   http://skyserver.sdss3.org/public/en/tools/chart/listinfo.aspx

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# Example script for looking at BOSS spectra and redshift fits via Python.
#
# Written by Adam S. Bolton, University of Utah, Oct. 2009
#

# Imports:
import numpy as n
import pyfits as pf
import matplotlib as mpl
mpl.use('TkAgg')
mpl.interactive(True)
from matplotlib import pyplot as p

# Set topdir:
topdir = '/data/BOSS/spectro/redux/v5_5_12/'

# Pick your plate/mjd and read the data:
plate = '3621'
mjd = '55104'
spfile = topdir + plate + '/spPlate-' + plate + '-' + mjd + '.fits'
zbfile = topdir + plate + '/spZbest-' + plate + '-' + mjd + '.fits'
hdulist = pf.open(spfile)
c0 = hdulist[0].header['coeff0']
c1 = hdulist[0].header['coeff1']
npix = hdulist[0].header['naxis1']
wave = 10.**(c0 + c1 * n.arange(npix))
# Following commented-out bit was needed for some of the early redux:
#bzero = hdulist[0].header['bzero']
bunit = hdulist[0].header['bunit']
flux = hdulist[0].data
ivar = hdulist[1].data
hdulist.close()
hdulist = 0
hdulist = pf.open(zbfile)
synflux = hdulist[2].data
zstruc = hdulist[1].data
hdulist.close()
hdulist = 0

i = 499
# Set starting fiber point (above), then copy and paste
# the following repeatedly to loop over spectra:
i+=1
# Following commented-out bit was needed for some of the early redux:
#p.plot(wave, (flux[i,:]-bzero) * (ivar[i,:] > 0), 'k', hold=False)
p.plot(wave, flux[i,:] * (ivar[i,:] > 0), 'k', hold=False)
p.plot(wave, synflux[i,:], 'g', hold=True)
p.xlabel('Angstroms')
p.ylabel(bunit)
p.title(zstruc[i].field('class') + ', z = ' + str(zstruc[i].field('z')))




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  SDSS get the images and the spectra
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One example from Peter Erwin:   http://www.mpe.mpg.de/~erwin/code/telarchive/
# This is the URL of the SDSS images ( from astroML)
http://www.astroml.org/sklearn_tutorial/auto_examples/plot_sdss_images.html

url = ("http://casjobs.sdss.org/ImgCutoutDR7/"
           "getjpeg.aspx?ra=%.8f&dec=%.8f&scale=%.2f&width=%i&height=%i"
           % (RA, DEC, scale, width, height))

However, this link does not work now. Please use :
SDSS_URL = ('http://skyservice.pha.jhu.edu/DR7/ImgCutout/getjpeg.aspx?'
            'ra=%(RA).8f&dec=%(DEC).8f&scale=%(scale).2f&width=%(width)i&height=%(height)i&opt=&query=')

# This is the URL of the sdss fits spectra (from astroML)
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')



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  DR7   about the spectra files 
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http://classic.sdss.org/dr7/products/spectra/read_spSpec.html
The spSpec file's header contains several parameters such as object identification and coordinates, observing information, spectral classification, redshift, etc..
The fits image contains a 4x(roughly 4000) image whose
  first row is the spectrum,
  second the continuum subtracted spectrum,
  third the error,
  forth a bitmask.
  fifth ?   sky light ?
Notice that the wavelength vector is not contained in the image, but must be generated from parameters in the header.
SDSS spectra are binned in constant Log(Λ ) and the wavelength can be obtained from the header parameters COEFF0 and COEFF1 (or alternatively CRVAL1 and CD1_1) as follows:

lambda = 10**(COEFF0 + COEFF1*i), where i denotes the (zero indexed) pixel number.

Six binary tables are included, most importantly,
 HDU 2 which contains a table of gaussian fits to line positions,
 HDU 3 which contains a table on line index parameters. Also included, but of less general interest, are:
 HDU 1 which contains line parameters used in the emission-line redshift determination;
 HDU 3 which contains information on emission-line redshifts;
 HDU 4 which contains a table of cross-correlation redshifts with all the templates, and
 HDU 6 which has additional mask information as well as the spectral resolution as a function of wavelength.