Examples

DES DR2 Sample of 1000 bright stars

SAMPLE OF 1000 BRIGHT STARS Selecting magnitudes of 1000 bright stars in g band with quality given by flags_g and star/galaxy classification given by extended_class_coadd FLAGS_[G,R,I,Z,Y] contains 8 flag bits with basic warnings about the source extraction process, in order of increasing concern. For instance: 1 aperture photometry is likely to be biased by neighboring sources or by more than 10% of bad pixels in any aperture 2 the object has been deblended (you would want to keep this on regions that are a bit crowded, like a galaxy cluster) 4 at least one object pixel is saturated EXTENDED_CLASS_COADD (classification of objects as stars or galaxies): 0 - very likely a star (pure sample of stars) 1 - likely a star, but a contamination of galaxies is expected (more complete sample of stars) 2 - likely a galaxy, but a contamination of stars is expected) (more complete sample of galaxies) 3 - very likely a galaxy (pure sample of galaxies) -99 - flag (no data) The stars were observed at least in one image (nepochs_g >= 1). See DR2 paper (https://arxiv.org/pdf/2101.05765.pdf) for a complete description of columns.

-- SAMPLE OF 1000 BRIGHT STARS
-- Selecting magnitudes of 1000 bright stars in g band
-- with quality given by flags_g and star/galaxy classification given by extended_class_coadd
-- FLAGS_[G,R,I,Z,Y] contains 8 flag bits with basic warnings about the source extraction process, in order of increasing concern. For instance:
-- 1 aperture photometry is likely to be biased by neighboring sources or by more than 10% of bad pixels in any aperture
-- 2 the object has been deblended (you would want to keep this on regions that are a bit crowded, like a galaxy cluster)
-- 4 at least one object pixel is saturated
-- EXTENDED_CLASS_COADD (classification of objects as stars or galaxies):
-- 0 - very likely a star (pure sample of stars)
-- 1 - likely a star, but a contamination of galaxies is expected (more complete sample of stars)
-- 2 - likely a galaxy, but a contamination of stars is expected) (more complete sample of galaxies)
-- 3 - very likely a galaxy (pure sample of galaxies)
-- -99 - flag (no data)
-- The stars were observed at least in one image (nepochs_g >= 1).
-- See DR2 paper (https://arxiv.org/pdf/2101.05765.pdf) for a complete description of columns.

SELECT top 1000 coadd_object_id, ra, dec, wavg_mag_psf_g, flags_g, extended_class_coadd, nepochs_g
FROM des_dr2.main
WHERE ABS(extended_class_coadd) < 2
AND flags_g < 4
AND wavg_mag_psf_g < 20
AND nepochs_g >= 1

DES DR2 Pure sample of 1000 bright galaxies in i band

PURE SAMPLE OF 1000 BRIGHT GALAXIES IN I BAND Selecting i magnitudes of 1000 bright galaxies corrected by extinction (Schlegel+1998) with quality given by flags_i and star/galaxy classification given by extended_class_coadd. FLAGS_[G,R,I,Z,Y] contains 8 flag bits with basic warnings about the source extraction process: 1 aperture photometry is likely to be biased by neighboring sources or by more than 10% of bad pixels in any aperture 2 the object has been deblended (you would want to keep this on regions that are a bit crowded, like a galaxy cluster) 4 at least one object pixel is saturated EXTENDED_CLASS_COADD (classification of objects as stars or galaxies): 0 - very likely a star (pure sample of stars) 1 - likely a star, but a contamination of galaxies is expected (more complete sample of stars) 2 - likely a galaxy, but a contamination of stars is expected (more complete sample of galaxies) 3 - very likely a galaxy (pure sample of galaxies) -99 - flag (no data) The galaxies were observed at least in one image (nepochs_i >= 1). See DR2 paper (https://arxiv.org/pdf/2101.05765.pdf) for a complete description of columns.

-- PURE SAMPLE OF 1000 BRIGHT GALAXIES IN I BAND
-- Selecting i magnitudes of 1000 bright galaxies corrected by extinction (Schlegel+1998)
-- with quality given by flags_i and star/galaxy classification given by extended_class_coadd.
-- FLAGS_[G,R,I,Z,Y] contains 8 flag bits with basic warnings about the source extraction process:
-- 1 aperture photometry is likely to be biased by neighboring sources or by more than 10% of bad pixels in any aperture
-- 2 the object has been deblended (you would want to keep this on regions that are a bit crowded, like a galaxy cluster)
-- 4 at least one object pixel is saturated
-- EXTENDED_CLASS_COADD (classification of objects as stars or galaxies):
-- 0 - very likely a star (pure sample of stars)
-- 1 - likely a star, but a contamination of galaxies is expected (more complete sample of stars)
-- 2 - likely a galaxy, but a contamination of stars is expected (more complete sample of galaxies)
-- 3 - very likely a galaxy (pure sample of galaxies)
-- -99 - flag (no data)
-- The galaxies were observed at least in one image (nepochs_i >= 1).
-- See DR2 paper (https://arxiv.org/pdf/2101.05765.pdf) for a complete description of columns.

SELECT top 1000 coadd_object_id, ra, dec, mag_auto_i_dered, flags_i, extended_class_coadd, nepochs_i
FROM des_dr2.main
WHERE ABS(extended_class_coadd) > 2
AND flags_i < 4
AND mag_auto_i_dered < 21
AND nepochs_i >= 1

DES DR2 Checking star-galaxy classification by color-color diagram

Checking star-galaxy classification by color-color diagram with a pure sample of bright stars

-- CHECKING STAR-GALAXY CLASSIFICATION BY COLOR-COLOR DIAGRAM WITH A PURE SAMPLE OF BRIGHT STARS

SELECT top 1000 coadd_object_id, ra, dec, wavg_mag_psf_g_dered, wavg_mag_psf_r_dered, wavg_mag_psf_i_dered, wavg_mag_psf_g_dered-wavg_mag_psf_r_dered as gr_color, wavg_mag_psf_r_dered-wavg_mag_psf_i_dered as ri_color
FROM des_dr2.main
AND ABS(extended_class_coadd) < 1
AND flags_g < 4
AND flags_r < 4
AND flags_i < 4
AND ABS(wavg_mag_psf_g_dered) < 22.
AND ABS(wavg_mag_psf_r_dered) < 22.
AND ABS(wavg_mag_psf_i_dered) < 22.

DES DR2 CMD of a pure sample of 1000 bright galaxies in i band

CMD OF A PURE SAMPLE OF 1000 BRIGHT GALAXIES IN I BAND Selecting magnitudes of a sample of 1000 bright galaxies in r and i band corrected by extinction (Schlegel+1998) with quality given by flags_i and star/galaxy classification given by extended_class_coadd. FLAGS_[G,R,I,Z,Y] contains 8 flag bits with basic warnings about the source extraction process: 1 aperture photometry is likely to be biased by neighboring sources or by more than 10% of bad pixels in any aperture 2 the object has been deblended (you would want to keep this on regions that are a bit crowded, like a galaxy cluster) 4 at least one object pixel is saturated EXTENDED_CLASS_COADD (classification of objects as stars or galaxies): 0 - very likely a star (pure sample of stars) 1 - likely a star, but a contamination of galaxies is expected (more complete sample of stars) 2 - likely a galaxy, but a contamination of stars is expected (more complete sample of galaxies) 3 - very likely a galaxy (pure sample of galaxies) -99 - flag (no data) The galaxies were observed at least in one image (nepochs_i >= 1). (r-i) color is calculated in order to plot a CMD. See DR2 paper (https://arxiv.org/pdf/2101.05765.pdf) for a complete description of columns.

-- CMD OF A PURE SAMPLE OF 1000 BRIGHT GALAXIES IN I BAND
-- Selecting magnitudes of a sample of 1000 bright galaxies in r and i band corrected by extinction (Schlegel+1998)
-- with quality given by flags_i and star/galaxy classification given by extended_class_coadd.
-- FLAGS_[G,R,I,Z,Y] contains 8 flag bits with basic warnings about the source extraction process:
-- 1 aperture photometry is likely to be biased by neighboring sources or by more than 10% of bad pixels in any aperture
-- 2 the object has been deblended (you would want to keep this on regions that are a bit crowded, like a galaxy cluster)
-- 4 at least one object pixel is saturated
-- EXTENDED_CLASS_COADD (classification of objects as stars or galaxies):
-- 0 - very likely a star (pure sample of stars)
-- 1 - likely a star, but a contamination of galaxies is expected (more complete sample of stars)
-- 2 - likely a galaxy, but a contamination of stars is expected (more complete sample of galaxies)
-- 3 - very likely a galaxy (pure sample of galaxies)
-- -99 - flag (no data)
-- The galaxies were observed at least in one image (nepochs_i >= 1).
-- See DR2 paper (https://arxiv.org/pdf/2101.05765.pdf) for a complete description of columns.
-- (r-i) color is calculated in order to plot a CMD.

SELECT top 1000 coadd_object_id, ra, dec, mag_auto_r_dered, mag_auto_i_dered, flags_r, flags_i, extended_class_coadd, nepochs_i,
mag_auto_r_dered - mag_auto_i_dered as ri_color
FROM des_dr2.main
WHERE ABS(extended_class_coadd) > 2
AND flags_i < 4
AND flags_r < 4
AND mag_auto_i_dered < 21
AND nepochs_r >= 1
AND nepochs_i >= 1

DES DR2 Magnitude errors for mag_auto

Magnitude errors for mag_auto

-- MAGNITUDE ERRORS FOR MAG_AUTO

SELECT top 1000 mag_auto_g, magerr_auto_g,
mag_auto_r, magerr_auto_r,
mag_auto_i, magerr_auto_i,
flags_g, flags_r, flags_i,
nepochs_g, nepochs_r, nepochs_i
FROM des_dr2.main
WHERE flags_g < 4
AND flags_r < 4
AND flags_i < 4
AND nepochs_g >= 1
AND nepochs_r >= 1
AND nepochs_i >= 1

DES DR2 Selecting stars in a box near Sculptor dwarf galaxy

Selecting stars in a box near Sculptor dwarf galaxy

-- SELECTING STARS IN A BOX NEAR SCULPTOR DWARF GALAXY!

SELECT top 100 coadd_object_id, ra, dec, mag_auto_g_dered, mag_auto_r_dered, mag_auto_g_dered - mag_auto_r_dered as gr_dered
FROM des_dr2.main
WHERE (ra > 15.0183 - 0.02)
AND (ra < 15.0183 + 0.02)
AND (dec > -33.719 - 0.02)
AND (dec < -33.719 + 0.02)
AND ABS(extended_class_coadd) < 2
AND flags_g < 4
AND flags_r < 4