I would like to know the criterias used to build des_dr1.galaxies table

Question

I did a massive query of some galaxies but checking final results I noticed some galaxies have been missed from the selection. For example I think I missed a galaxy around coords: 63.9365, -41.7296

So I query again around these coordinates: 

query="SELECT ra, dec, mag_auto_i,mag_auto_r, mag_auto_g, class_star_g FROM des_dr1.galaxies WHERE 't' = Q3C_RADIAL_QUERY(ra, dec,63.9365, -41.7296 ,0.00278)"

getting: 

ra        dec  mag_auto_i  mag_auto_r  mag_auto_g  class_star_g      g-i      g-r

0  63.939107 -41.727997    20.3290    21.5768    23.7171      0.159899  3.3881  2.1403

1  63.933264 -41.729276    20.3237    22.2376    22.5147      0.059879  2.1910  0.2771

2  63.935540 -41.729488    19.2159    20.4618    22.3500      0.000308  3.1341  1.8882

3  63.936803 -41.731150    22.8635    24.1835    99.0000      0.363030  76.1365  74.8165

but all of them are nearby objects and not the galaxy.

So I looked in the main catalog but adding a restriction in class_star_g<0.1 to query less objects:

query="SELECT ra, dec, mag_auto_i,mag_auto_r, mag_auto_g, class_star_g FROM des_dr1.main WHERE class_star_g<0.1 and 't' = Q3C_RADIAL_QUERY(ra, dec,63.9365, -41.7296 ,0.00278)"

ra        dec  mag_auto_i  mag_auto_r  mag_auto_g  class_star_g    g-i    g-r

0  63.933291 -41.730269    20.4455    21.0329    21.3564      0.011669  0.9109  0.3235

1  63.933264 -41.729276    20.3237    22.2376    22.5147      0.059879  2.1910  0.2771

2  63.935540 -41.729488    19.2159    20.4618    22.3500      0.000308  3.1341  1.8882

3  63.936319 -41.729519    19.5417    20.8182    23.0032      0.004588  3.4615  2.1850 missing one!

Here number 3 now corresponds to the object that I was missing and I also obtained additional ones. So I would like to understand how des_dr1.galaxies was builded in order to know what type of objects and how many more I missed by using this table. I tried to find references/paper but I didn't succeed. 

Thanks in advance for the help. 

K.

Answer 1

The 'galaxies' table is a materialized view of the main catalog created with the following query:

CREATE MATERIALIZED VIEW galaxies AS (
   SELECT *  
   FROM des_dr1.main  
   WHERE
   (WAVG_SPREAD_MODEL_I + WAVG_SPREADERR_MODEL_I) > 0.003 and
   (WAVG_SPREAD_MODEL_I - WAVG_SPREADERR_MODEL_I) > 0.001 and
   WAVG_SPREAD_MODEL_I > -1 and
   IMAFLAGS_ISO_I = 0 and
   MAG_AUTO_I < 23
);

As I remember this criteria was suggested by the DES collaboration however I'm having trouble locating the exact reference.  Hope this helps.

Edit:  See Sec 4.5 of the DES DR1 paper at https://arxiv.org/pdf/1801.03181.pdf