Accurate determinations of stellar parameters and distances for large complete samples of stars are keys for conducting detailed studies of the formaton and evolution of our Galaxy. Here we present stellar atmospheric parameters (effective temperature, luminosity classifications, and metallicity) estimates for some 24 million stars determined from the stellar colors of SMSS DR2 and Gaia EDR3, based on training datasets with available spectroscopic measurements from previous high/medium/low-resolution spectroscopic surveys.

The number of stars with photometric-metallicity estimates is 4-5 times larger than that collected by the current largest spectroscopic survey to date, LAMOST, over the course of the past decade. External checks indicate that the precision of the photometric-metallicity estimates are quite high, comparable to or slightly better than that derived from spectroscopy, with typical values around 0.05-0.15 dex for both dwarf and giant stars with [Fe/H] > -1.0, 0.10-0.20 dex for giant stars with -2.0 < [Fe/H] <= -1.0. and 0.20-0.25 dex for for giant stars with [Fe/H] <= -2.0, and include estimates for stars as metal-poor as [Fe/H] ~ -3.5, substantially lower than previous photometric techniques. Photometric-metallicity estimates are obtained for an unprecedented number of metal-poor stars, including a total of over three million metal-poor (MP; [Fe/H] <= -1.0) stars, over half a million very metal-poor (VMP; [Fe/H] <= -2.0) stars, and over 25,000 extremely metal-poor (EMP; [Fe/H] <= -3.0) stars.

Moreover, distances are determined for over 20 million stars in our sample. For the over 18 million sample stars with accurate Gaia parallaxes, stellar ages are estimated by comparing with theoretical isochrones.

Astrometric information is provided for the stars in our catalog, along with radial velocities for ~10% of our sample stars, taken from completed/ongoing large-scale spectroscopic surveys.

The full catalog can be downloaded by the following links in txt/fits format. The description of those files can be found as follows.

FileName                     Lrecl  Records   Explanations
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ReadMe                           80        .   This file
SMSS_PARAM_DEC+00.txt           524   529444   SMSS parameter catalog with dec greater than +00 degree
SMSS_PARAM_DEC-10.txt           524  3462313   SMSS parameter catalog with dec between -10 and 0 degrees
SMSS_PARAM_DEC-20.txt           524  3456364   SMSS parameter catalog with dec between -20 and -10 degrees
SMSS_PARAM_DEC-30.txt           524  4478051   SMSS parameter catalog with dec between -30 and -20 degrees
SMSS_PARAM_DEC-40.txt           524  4715142   SMSS parameter catalog with dec between -40 and -30 degrees
SMSS_PARAM_DEC-50.txt           524  3109506   SMSS parameter catalog with dec between -50 and -40 degrees
SMSS_PARAM_DEC-60.txt           524  1771420   SMSS parameter catalog with dec between -60 and -50 degrees
SMSS_PARAM_DEC-70.txt           524  1496596   SMSS parameter catalog with dec between -70 and -60 degrees
SMSS_PARAM_DEC-80.txt           524   988150   SMSS parameter catalog with dec between -80 and -70 degrees
SMSS_PARAM_DEC-90.txt           524   232866   SMSS parameter catalog with dec between -90 and -80 degrees
SMSS_PARAM_ALL.fits             524 24239852   Full SMSS parameter catalog in FITS format
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Byte-by-byte Description of files: SMSS_PARAM_DEC-90.txt to SMSS_PARAM_DEC+00.txt
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     Bytes Format Units   Label                Explanations
--------------------------------------------------------------------------------
     1-  9  I9    ---     SMSS_ID              Unique ID for the SMSS catalog
    11- 29  A19   ---     sourceid             Cross-matched Gaia EDR3 source ID
    31- 40  F10.6 deg     ra                   Right Ascension from SMSS DR2 (J2000)
    42- 51  F10.6 deg     dec                  Declination from SMSS DR2 (J2000)
    53- 62  F10.6 deg     gl                   Galactic longitude derived from ICRS coordinates 
    64- 73  F10.6 deg     gb                   Galactic latitude derived from ICRS coordinates
    75- 80  F6.3  mag     u                    u-band PSF magnitude from SMSS DR2 (1)
    82- 87  F6.3  mag     v                    v-band PSF magnitude from SMSS DR2 (1)
    89- 94  F6.3  mag     g                    g-band PSF magnitude from SMSS DR2 (1)
    96-101  F6.3  mag     r                    r-band PSF magnitude from SMSS DR2 (1)
   103-108  F6.3  mag     i                    i-band PSF magnitude from SMSS DR2 (1)
   110-115  F6.3  mag     z                    z-band PSF magnitude from SMSS DR2 (1)
   117-122  F6.3  mag     uc                   Corrected u-band PSF magnitude of SMSS DR2 by Huang et al. 
                                               (2021) (1) 
   124-129  F6.3  mag     vc                   Corrected v-band PSF magnitude of SMSS DR2 by Huang et al. 
                                               (2021) (1) 
   131-136  F6.3  mag     gc                   Corrected g-band PSF magnitude of SMSS DR2 by Huang et al. 
                                               (2021) (1) 
   138-143  F6.3  mag     rc                   Corrected r-band PSF magnitude of SMSS DR2 by Huang et al. 
                                               (2021) (1) 
   145-149  F5.3  mag     err_u                Uncertainty of u-band PSF magnitude from SMSS DR2 (2)
   151-155  F5.3  mag     err_v                Uncertainty of v-band PSF magnitude from SMSS DR2 (2)
   157-161  F5.3  mag     err_g                Uncertainty of g-band PSF magnitude from SMSS DR2 (2)
   163-167  F5.3  mag     err_r                Uncertainty of r-band PSF magnitude from SMSS DR2 (2)
   169-173  F5.3  mag     err_i                Uncertainty of i-band PSF magnitude from SMSS DR2 (2)
   175-179  F5.3  mag     err_z                Uncertainty of z-band PSF magnitude from SMSS DR2 (2)
   181-186  F6.3  mag     G_C                  Magnitude for the Gaia G-band (calibration-corrected)
   188-193  F6.3  mag     BP                   Magnitude for the Gaia BP-band
   195-200  F6.3  mag     RP                   Magnitude for the Gaia RP-band
   202-206  F5.3  mag     err_G_C              Uncertainty of the Gaia G-band magnitude
                                                (calibration-corrected)
   208-212  F5.3  mag     err_BP               Uncertainty of the Gaia BP-band magnitude
   214-218  F5.3  mag     err_RP               Uncertainty of the Gaia RP-band magnitude
   220-224  F5.3  mag     ebv_sfd              Value of E(B − V) from from the extinction map of Schlegel
                                                et al. (1998), corrected for a 14% systematic
   226-231  F6.3  mag     br0                  Intrinsic color (BP-RP)_0
   233-238  F6.3  mag     ub0                  Intrinsic color (u-BP)_0 (2)
   240-245  F6.3  mag     vb0                  Intrinsic color (v-BP)_0 (2)
   247-251  F5.3  mag     err_br0              Uncertainty of color (BP-RP)_0
   253-257  F5.3  mag     err_ub0              Uncertainty of color (u-BP)_0 (2)
   259-263  F5.3  mag     err_vb0              Uncertainty of color (v-BP)_0 (2)
   265-269  F5.2  dex     feh                  Photometric metallicity
   271-274  F4.2  dex     err_feh              Uncertainty of photometric metallicity
   276-280  A5    ---     feh_flg              Flag to indicate the stellar color(s) used in 
                                               estimating [Fe/H], which takes the values “ub”, “vb”, 
                                               and “ub+vb”
   282-285  I4    K       Teff                 Effective temperature
   287-289  I3    K       err_Teff             Uncertainty of effective temperature
   291-297  F7.3  kpc     dist_adop            Distance (3)
   299-304  F6.3  kpc     err_dist_adop        Uncertainty of distance (3)
   306-313  A8    kpc     dist_adop_flg        Flag to indicate the method used to derive distance, which 
                                               takes the values “parallax”, “CAF”, and “NO” (4)
   315-321  F7.3  kpc     X                    X position in the right-handed Cartesian system (3)
   323-329  F7.3  kpc     Y                    Y position in the right-handed Cartesian system (3)
   331-337  F7.3  kpc     Z                    Z position in the right-handed 
                                               Cartesian system (3)
   339-344  F6.3  kpc     err_X                Uncertainty of X position in the right-handed 
                                               Cartesian system (3)
   346-351  F6.3  kpc     err_Y                Uncertainty of Y position in the right-handed 
                                               Cartesian system (3)
   353-358  F6.3  kpc     err_Z                Uncertainty of Z position in the right-handed 
                                               Cartesian system (3)
   360-366  F7.3  kpc     rgc                  Galactocentric distance (3)
   368-373  F6.3  kpc     err_rgc              Uncertainty of Galactocentric distance (3)
   375-381  F7.3  kpc     rad                  Projected Galactocentric distance onto the Galactic plane (3)
   383-388  F6.3  kpc     err_rad              Uncertainty of projected Galactocentric distance (3)
   390-394  F5.2  Gyr     age                  Stellar age (3)
   396-399  F4.2  Gyr     err_age              Uncertainty of stellar age (3)
   401-407  F7.2  km/s    rv_adop              Radial velocity (5)
   409-413  F5.2  km/s    err_rv_adop          Uncertainty of radial velocity (3)
   415-422  A8    ---     rv_adop_flg          Flag to indicate the source of radial velocity, 
                                               which takes the values “Gaia-ESO”, “GALAH”, “APOGEE”, 
                                               “Gaia”, “RAVE”, “LAMOST”, “SEGUE”, “AEGIS”, 
                                               “B&B”, “LIT” and “NO” (6)
   424-429  F6.2  mas     parallax             Parallax from Gaia EDR3 (7)
   431-436  F6.2  mas     err_parallax         Uncertainty of parallax from Gaia EDR3 (8)
   438-444  F7.2  mas/yr  pmra                 Proper motion in Right Ascension direction from Gaia EDR3 (9)
   446-449  F4.2  mas/yr  err_pmra             Uncertainty of proper motion in Right Ascension direction 
                                               from Gaia EDR3 (8)
   451-457  F7.2  mas/yr  pmdec                Proper motion in Declination direction from Gaia EDR3 (9)
   459-462  F4.2  mas/yr  err_pmdec            Uncertainty of proper motion in Declination direction 
                                               from Gaia EDR3 (8)
   464-470  F7.2  km/s    vrad                 Radial velocity in the Galactocentric cylindrical system (5)
   472-478  F7.2  km/s    vphi                 Azimuthal velocity in the Galactocentric 
                                               cylindrical system (5)
   480-486  F7.2  km/s    vz                   Vertical velocity in the Galactocentric 
                                               cylindrical system (5)
   488-492  F5.2  km/s    err_vrad             Uncertainty of radial velocity in the Galactocentric 
                                               cylindrical system (3)
   494-498  F5.2  km/s    err_vphi             Uncertainty of azimuthal velocity in the Galactocentric 
                                               cylindrical system (3)
   500-504  F5.2  km/s    err_vz               Uncertainty of vertical velocity in the Galactocentric 
                                               cylindrical system (3)
   506-511  F6.2  ---     RUWE                 Renormalised unit weight error from Gaia EDR3 (7)
   513-517  A5    ---     type                 Flag to indicate classifications of stars, which takes the 
                                               values “dwarf” and “giant”
   519-524  A6    ---     subtype              Flag to indicate further sub-classifications of dwarf stars, 
                                               which takes the values “TO”, “MS”, “Binary” and “NO”
 --------------------------------------------------------------------------------
  Note (1): 99.999 means no measurement
  Note (2): 0.000 means no measurement
  Note (3): 0.00 means no estimate
  Note (4): CAF means distance estimates from the color - absolute magnitude method
  
  Note (5): -999.99 menas no estimate
  Note (6):  The radial velocities are from Gaia-ESO DR3 (Gilmore et al. 2012; Randich & Gilmore 2013), 
             GALAH DR3+ (Buder et al. 2021), SDSS DR16 (Ahumada et al. 2020), 
             Gaia DR2 (Katz et al. 2019), RAVE DR5 (Kunder et al. 2017), LAMOST DR7, 
             AEGIS (Yoon et al. 2018), B&B survey (Schlaufman & Casey 2014), 
             as reported by Limberg et al. (2021), and several bibliographic collections 
             (Barbier-Brossat& Figon 2000; Malaroda et al. 2006; de Bruijne et al. 2012). 
  Note (7): -99.99 means no measurement
  Note (8): 0.00 means no measurement
  Note (9): -999.99 means no measurement