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Find information, examples, FAQs and extensive descriptions of the data, curated by the survey teams.

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GALAH

The Galactic Archaeology with HERMES survey is collecting stellar parameters and abundances for one million stars in the Milky Way. GALAH yields a comprehensive view of the formation & evolution of the Galaxy.
March 26, 2018 by S. Martell
Oct. 11, 2020, 2:48 p.m. J. Simpson

Table schema

GALAH DR2
Field name Units Data type Description
star_id char[16] 2MASS ID number by default, UCAC4 ID number if 2MASS unavailable (begins with UCAC4-)
sobject_id int64 Unique per-observation star ID
gaia_dr2_id int64 Gaia DR2 SOURCE_ID
ndfclass char[12] Observation type
field_id int64 GALAH internal field ID number
raj2000 Deg float64 Right ascension from 2MASS, J2000
dej2000 Deg float64 Declination from 2MASS, J2000
jmag Mag float64 J magnitude from 2MASS
hmag Mag float64 H magnitude from 2MASS
kmag Mag float64 K magnitude from 2MASS
vmag_jk Mag float64 Synthetic V magnitude calculated from JHK, used for target selection
e_jmag Mag float64 Uncertainty in J magnitude, from 2MASS
e_hmag Mag float64 Uncertainty in H magnitude, from 2MASS
e_kmag Mag float64 Uncertainty in K magnitude, from 2MASS
snr_c1 float64 Signal to noise per pixel in the HERMES blue channel
snr_c2 float64 Signal to noise per pixel in the HERMES green channel
snr_c3 float64 Signal to noise per pixel in the HERMES red channel
snr_c4 float64 Signal to noise per pixel in the HERMES IR channel
rv_synt km/s float64 Radial velocity from cross-correlation against synthetic spectra
e_rv_synt km/s float64 Uncertainty in rv_synt
rv_obst km/s float64 Radial velocity from internal cross-correlation against data
e_rv_obst km/s float64 Uncertainty in rv_obst
rv_nogr_obst km/s float64 Radial velocity from internal cross-correlation against data, uncorrected for gravitational redshift
e_rv_nogr_obst km/s float64 Uncertainty in rv_nogr_obst
chi2_cannon float64 Summed chi-squared over all spectral pixels
sp_label_distance float64 Label distance similar to Ho et al. (2017)
flag_cannon int64 Bitmask for spectrum information. Flag=0 parameters are recommended for use.
teff K float64 Effective temperature
e_teff K float64 Uncertainty in teff
logg log(cm/s**2) float64 Surface gravity
e_logg log(cm/s**2) float64 Uncertainty in logg
fe_h dex float64 Iron abundance (not overall metallicity [M/H])
e_fe_h dex float64 Uncertainty in fe_h
vmic km/s float64 Microturbulent velocity
e_vmic km/s float64 Uncertainty in vmic
vsini km/s float64 Line of sight rotational velocity
e_vsini km/s float64 Uncertainty in vsini
alpha_fe dex float64 Alpha enhancement, determined as an error-weighted combination of Mg, Si, Ca, Ti
e_alpha_fe dex float64 Uncertainty in alpha_fe
x_fe dex float64 [X/Fe] abundance for element X. Elements reported in this table are Li, C, O, Na, Mg, Al, Si, K, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Ba, La and Eu
e_x_fe dex float64 Uncertainty in x_fe
flag_x_fe int64 Bitmask indicating difficulty in abundance determination. Flag=0 abundances are recommended for use.

flag_cannon bitmask values

Value Meaning
0 No flag
1 The Cannon starts to extrapolate. For some stars the values could be incorrect.
2 The chi-squared of the best fitting model spectrum is significantly higher or lower.
4 Reduction flag raised
8 Binary star according to t-SNE
16 Negative flux according to t-SNE
32 Oscillating continuum according to t-SNE
64 General reduction issues according to t-SNE
128 Emission lines according to t-SNE

flag_x_fe bitmask values

Value Meaning
0 No flag
1 Line strength below 2-sigma upper limit
2 The Cannon starts to extrapolate. For some stars the values could be incorrect.
4 The chi-squared of the best fitting model spectrum is significantly higher or lower.
8 flag_cannon is not 0
March 26, 2018 by S. Martell
Oct. 11, 2020, 2:48 p.m. J. Simpson