The catalogue / Labels and quality flags

Labels and quality flags

Each label source stores a value, an error and a quality flag for every parameter of every star. This page lists the parameters and says when a label is valid.

Parameters

The file’s parameter_names attribute lists the parameters in the order of the label columns. APOGEE and GALAH use the same order. A default build has 11 parameters:

Column	Name	Parameter	Units
0	teff	effective temperature	K
1	logg	surface gravity, log g	dex, with g in cm s⁻²
2	fe_h	[Fe/H]	dex
3–10	mg_fe, c_fe, si_fe, ni_fe, al_fe, ca_fe, n_fe, mn_fe	[X/Fe] of Mg, C, Si, Ni, Al, Ca, N and Mn	dex

The extended set

With the option --elements extended, scripts/build_catalogue_v2.py adds nine elements after Mn: O, Na, K, Ti, V, Cr, Co, Ba and Sr. The catalogue then has 20 parameters.

A label source does not measure every element. If its input file has no column for an element, the builder stores that element with error 0. These labels are never valid.

[X/Fe] and [X/H]

By default the abundances are relative to iron, [X/Fe]. With the option --abundance-scale x_h, the builder stores them relative to hydrogen, [X/H], and the names end in _h, such as mg_h. The file’s abundance_scale attribute records the choice.

The builder derives [X/H] from [X/Fe] and [Fe/H]:

\[ [\mathrm{X/H}] = [\mathrm{X/Fe}] + [\mathrm{Fe/H}], \qquad \sigma_{\mathrm{X/H}} = \sqrt{\sigma_{\mathrm{X/Fe}}^2 + \sigma_{\mathrm{Fe/H}}^2}, \]

where σ is the error of each abundance. GALAH abundances are always derived. For APOGEE, the builder copies [X/H] from the allStar X_H column where the input file has it, and the error from X_H_ERR. It derives [X/H] only for an element without that column. APOGEE measures no Ba or Sr, so its ba_h and sr_h labels have error 0 and are never valid.

When a label is valid

A label is valid when its error is positive and its flag is 0; Preprocessing gives the masking rule. The builder flags a label whose value or error is not finite, and stores it with value 0 and error 0.

In a built catalogue each flag is 0 or 1. The loaders take a max_flag_bits argument, which limits the number of flagged labels of a star. A star with more flagged labels loses all its labels: load_labels and load_merged_sparse mask them, and load_for_training drops the star. With 0, one flagged label removes the whole star. With −1, the loaders remove only the flagged labels.

Quality flags per label source

The builder sets a label’s flag from the flags of its label source:

Parameter	APOGEE flag set when	GALAH flag set when
teff	ASPCAPFLAG bit 0 (TEFF_WARN) or bit 16 (TEFF_BAD)	flag_sp ≠ 0
logg	ASPCAPFLAG bit 1 (LOGG_WARN) or bit 17 (LOGG_BAD)	flag_sp ≠ 0
fe_h	FE_H_FLAG ≠ 0	flag_fe_h ≠ 0
each [X/Fe]	X_FE_FLAG ≠ 0, such as MG_FE_FLAG	flag_x_fe ≠ 0, such as flag_mg_fe
each [X/H] copied from X_H	X_FE_FLAG ≠ 0
each derived [X/H]	X_FE_FLAG ≠ 0 or FE_H_FLAG ≠ 0	flag_x_fe ≠ 0 or flag_fe_h ≠ 0

Other ASPCAPFLAG bits, such as VMICRO_WARN, do not flag Teff or log g. The bits are defined in the APOGEE bitmask documentation and the GALAH flag documentation.