This page gives details of the flags found in the GALAH DR3 catalogues. The main flags that will be of interest to most users of GALAH are: flag_sp, flag_fe_h, and the individual flag_X_fe.

For science cases involving stellar parameters, it is highly recommended that you only consider stars where flag_sp == 0 and flag_fe_h == 0. For science cases involving the abundance of element x, it is highly recommended that you only consider X_fe where flag_X_fe == 0 and snr_c3_iraf > 30.

### flag_sp

This flag is found in the GALAH_DR3_main_allstar_v2 (and GALAH_DR3_main_allspec_v2) catalogues and is the final bit-flag for the stellar parameter quality flag. Its value is found via the summation of the individual flags as tabulated below.

The value of flag_sp are found via the summation of the individual flags as tabulated below:

Value Description
0 No identified problems with stellar parameter determination
1 Gaia DR2 ruwe_dr2 > 1.4 (unreliable astrometric solution, see Lindegren 2018)
4 Low S/N (snr_c2_iraf<10)
8 Reduction issues: (a) Wavelength solution (propagating of red_flag); (b) t-SNE projected reduction issues; (c) Negative/positive fluxes, spikes, etc.
16 t-SNE projected emission features
32 t-SNE projected binaries
64 Binary sequence/pre-main sequence flag
128 SNR-dependent high SME 𝜒2 (bad fit) 512
256 Problems with Fe lines, where line flux is not between 0.03 and 1.00, [Fe/H] not reliable, or blending suspected
512 SME did not finish: (a) No convergence == non-finite stellar parameters; (b) Gaussian RV fit failed
1024 MARCS grid limit reached or outside of reasonable parameter range

The first estimate of the surface gravity of each star was found from the Gaia DR2 parallax, so the first bit of flag_sp indicates stars with likely unreliable astrometry in Gaia DR2 (defined as ruwe_dr2>1.4). Note that a high RUWE in Gaia DR2 may not be indicative of a star having less reliable astrometry in Gaia eDR3 (and future releases).

### flag_fe_h

This flag is found in GALAH_DR3_main_allstar_v2 and GALAH_DR3_main_allstar_v2 and is the final bit-flag for the overall iron abundance fe_h. Its values are found via the summation of the individual flags as tabulated below.

Value Meaning
0 No identified problems with abundance determination of element fe_h
1 Upper limit
16 No reliable measurement reported

### flag_X_fe

These flag are found in GALAH_DR3_main_allstar_v2 and are the final bit-flag for the elemental abundance quality flag for the elemental abundance x_fe. Their values are found via the summation of the individual flags as tabulated below.

Value Meaning
0 No identified problems with abundance determination of element X_fe
1 Upper limit
32 No reliable measurement reported

### ind_flag_X1234

These flags are found in the GALAH_DR3_main_allspec_v2 and are the final bit-flag for the elemental abundance quality for the individual line ind_X1234_fe abundances. Their values are found via the summation of the individual flags as tabulated below.

Value Meaning
0 No identified problems with abundance determination of element ind_X1234_fe
1 Upper limit
2 Bad fit / large 𝜒2 fit
4 Uncertain measurement / saturation
16 Bad stellar parameter flag (flag_sp >= 128)
32 No measurement available

### Other flags

There are a number of other flags found in the GALAH catalogues. Most are only of interest for expert users.

#### red_flag

The spectrum reduction pipeline quality flag. It can be ignored except for expert use, as its value is folded into flag_sp.

#### flag_guess

The GUESS reduction pipeline finds a first estimate of the stellar parameters for a given spectrum. flag_guess is found in the GALAH_DR3_main_allstar_v2 and GALAH_DR3_main_allspec_v2 catalogues and is the GUESS quality flag. This flag can be ignored except for expert use. There are only about 2000 stars in GALAH DR3 for which flag_guess>0 while flag_sp==0.

#### flag_repeat

This flag is set to 0 to indicate if a given sobject_id entry in the GALAH_DR3_main_allspec_v2 is found in GALAH_DR3_main_allstar_v2.

#### use_dist_flag

This flag informs which distance value was used in the Galactic orbit calculations for the GALAH_DR3_VAC_dynamics_v2 catalogue:

• 0: distance_bstep; 1: r_med_photogeo; 2: r_med_geo; 4: parallax; 8: No distance.

#### use_rv_flag

This flag informs which radial velocity value has been used for rv_galah for a given sobject_id:

• 0: rv_obst; 1: rv_sme_v2; 2: dr2_radial_velocity; 4: No radial velocity.

#### Flags from Gaia catalogues

flag_edr3dist, proper_motion_propagation, astrometric_primary_flag are flags propogated from the Gaia catalogues.