ZWARNING: Warnings for SDSS spectra

Spectra with zWarning equal to zero have no known problems. MANY_OUTLIERS is only ever set in the data taken with the SDSS spectrograph, not the BOSS spectrograph (the SDSS-I, -II and SEGUE-2 surveys). If it is set, that usually indicates a high signal-to-noise spectrum or broad emission lines in a galaxy; that is, MANY_OUTLIERS only rarely signifies a real error.

Bit name	Binary digit	Description
SKY	0	sky fiber
LITTLE_COVERAGE	1	too little wavelength coverage (WCOVERAGE < 0.18)
SMALL_DELTA_CHI2	2	chi-squared of best fit is too close to that of second best (< 0.01 in reduced chi-squared)
NEGATIVE_MODEL	3	synthetic spectrum is negative (only set for stars and QSOs)
MANY_OUTLIERS	4	fraction of points more than 5 sigma away from best model is too large (> 0.05)
Z_FITLIMIT	5	chi-squared minimum at edge of the redshift fitting range (Z_ERR set to -1)
NEGATIVE_EMISSION	6	a QSO line exhibits negative emission, triggered only in QSO spectra, if C_IV, C_III, Mg_II, H_beta, or H_alpha has LINEAREA + 3 * LINEAREA_ERR < 0
UNPLUGGED	7	the fiber was unplugged, so no spectrum obtained
BAD_TARGET	8	catastrophically bad targeting data (e.g. bad astrometry)