Documentation

Current Release

Data Release 3.2 (2021-02-13)

This is a major update of GALAH DR3 to the original GALAH DR3 release:

• Improvements and fixes to radial velocity measurement;
• Cross-match of GALAH DR3 with Gaia eDR3;
• Changes to the contents of tables and updating derived parameters for the new Gaia eDR3 astrometry and photometry. But we do not make any changes to values of stellar parameters and abundances in the main_star catalogue.

Improvements to radial velocity measurement

There have been two changes to the radial velocities reported in GALAH DR3.

• We have fixed a bug in the calculation of barycentric velocity corrections. The size of the error was on average 0.3 km/s, with 99 per cent of stars being affected by less than 1 km/s.
• The method by which the reported rv_galah value in all the tables was measured has changed for most stars. Previously, for all stars rv_galah was calculated by SME as part of the stellar parameter and abundance determination. Now, for 80 per cent spectra rv_galah is the radial velocity as calculated by Zwitter et al (2020). This method has errors typically five times smaller than the SME-derived values. There is now a use_rv_flag in the tables galah_dr3.vac_dynamics and galah_dr3.vac_rv that indicates the source of the radial velocity for a given spectrum.

Cross-matched GALAH DR3 with Gaia eDR3.

This cross-match used the previously identified Gaia DR2 source_id for each star and the gaiaedr3.dr2_neighbourhood table created by the Gaia team. More details can be found on the caveats page.

• There is a Gaia eDR3 source_id for every entry in the galah_dr3.main_star table.
• All matched sources have an angular distance between their Gaia DR2 and eDR3 sources smaller than 160 mas, and 99.9 per cent are within 20 mas.
• For the 17654 stars with a Gaia DR2 source_id that had more than one Gaia eDR3 match in gaiaedr3.dr2_neighbourhood (98 per cent two matches, and the remainder with ≤4 matches) we have chosen the match with the smallest angular distances between the Gaia DR2 and Gaia eDR3 position.
  • For over 99 per cent of these 17654 stars, the closest match had an angular distance <10 mas, and second closest match was >600 mas.
  • There is likely source confusion for ~100 stars. For instance, for 57 of the 17654 stars with multiple matches in the gaiaedr3.dr2_neighbourhood table, the second closest match in angular distance has a smaller magnitude difference between Gaia DR2 and eDR3.

Changes to the contents of tables

The consequence of the update to Gaia eDR3 is that most of the GALAH DR3 tables have had changes to their contents:

• We have not changed the GALAH DR3 stellar parameters (e.g., teff, logg, fe_h columns) or abundances (e.g., x_fe columns) in the galah_dr3.main_star and galah_dr3.main_spec tables. These used the Gaia DR2 parallaxes as a prior for the stellar parameter determination, and we have not re-run the analysis pipeline.
• For the galah_dr3.main_star and galah_dr3.main_spec tables, the Gaia DR2-related columns have either been:
  • removed if they had not been used in the GALAH DR3 analysis (e.g., pmra, pmdec)
  • retained if they were used as part of the GALAH DR3 analysis , but with "_dr2" appended to their column names (e.g., parallax and ruwe are now parallax_dr2 and ruwe_dr2).
• There are new versions of the galah_dr3.vac_dynamics and galah_dr3.vac_ages tables using the improved Gaia eDR3 astrometry and GALAH DR3 radial velocities.
• There is a new table called galah_dr3.vac_gaiaedr3 that contains Gaia eDR3 data for all our stars.

Details of changes to the tables

Changes to galah_dr3.main_star

• Changed values:
  • rv_galah (and its error columns)
• Removed Gaia DR2 data columns:
  • pmra, pmdec (and their error columns)
  • the covariance values (e.g., pmra_pmdec_corr), bp_rp, phot_g_mean_mag, l, b, ra_error, dec_error
• Appended _dr2 suffix to the names of retained Gaia DR2 data columns:
  • ra, dec, parallax, rv_gaia (and their error columns)
  • ruwe, r_est, r_hi, r_len, r_lo
• New columns:
  • dr2_source_id and dr3_source_id
  • Cr2_fe, Sc2_fe (and their related columns), and ebv (all previously found in the main_spec table)

Changes to galah_dr3.main_spec

• All the same Gaia columns changes as the main_star table.

Changes to the galah_dr3.vac_ages

• Changed values:
  • All columns except sobject_id
  • Re-calculated with the new Gaia eDR3 inputs
• New columns
  • abs_j_bstep, abs_ks_bstep (and their error columns)
  • the 50 percentile value for all BSTEP calculated values

Changes to galah_dr3.vac_dynamics

• Changed values:
  • All columns except sobject_id
  • Re-calculated with the new Gaia eDR3 inputs
• Renamed columns:
  • vphi_Rzphi to vT_Rzphi (and their error columns)
• New columns
  • angle_R, angle_phi, angle_z (and their error columns)
    • These are the radial, azimuthal, vertical orbit angles
  • use_dist_flag and use_rv_flag
    • bitmask flag which distances and rv were used

Changes to galah_dr3.vac_rv

This table now collates different measurements of the radial velocities values for a given spectrum, rather than just the value calculated by Zwitter et al (2020).

New table galah_dr3.vac_gaiaedr3

• All stars observed by GALAH DR3 for which we can identify a Gaia eDR3 match
• GALAH DR3 sobject_id and star_id
• All columns from gaiaedr3.gaia_source
• All columns from gaiaedr3.dr2_neighbourhood:
  • e.g., angular_distance, magnitude_difference, proper_motion_propagation
• Photogeometric and Geometric Distances from Bailer-Jones et al. (2020)
• Zeropoints from Lindegren et al. (2020)

Minor file name changes

For consistency, all files been updated to have a _v2 suffix, even if they did not have any changes to their contents (e.g., the large compressed files of the spectra).

Previous Releases

Data Release 3.1 (2021-01-18)

Major Updates

• Reduced spectra for all stars in the main catalogue

Data Release 3.0 (2020-11-06)

The Third Data Release of the Galactic Archaeology with HERMES (GALAH) survey provides 678,423 spectra for 600,258 mostly nearby stars, that have been observed with the HERMES spectrograph at the Anglo-Australian Telescope between November 2013 and February 2019. With this data release, for the first time, we provide the reduced one-dimensional spectra for the stars.

See the overview page for more details.

Minor post-release updates

Documentation

• Data reduction and analysis: Information on 7249 stars that were in GALAH DR2 but not in GALAH DR3.