LAMOST DR5_v3 data were released to all the users in June of 2019. The international version of DR4 is a subset of DR5_v3. Except the update of the ratio of signal to noise (SNR) information, this version on the parameters has no difference with the domestic DR5_v2 which is the revised version of domestic DR5_v1. Comparing with DR5_v1, the only change is the amount of released data of DR5_v2. Specifically, 30, 817 spectra are added in and 21, 027 spectra are abandoned from the new verison. Besides, the information is updated for 26, 341 spectra. We present the distributions of parameters for DR5_v2, and compare this version with the previous versions. The results are shown as follows.
The atmospherical parameter space of DR5_v2 is shown as follows. Metallicity bins are represented by different colors.
The histograms of Teff, logg, [Fe/H] and rv are plotted individually.
The following diagrams show the distributions of errors of atmospherical parameters (Teff, logg, [Fe/H]) as well as rv in different SNR of r band (snr)) bins.
We compare the atmospherical parameters of DR5_v2 with those of DR5_v1. There is little difference between these two versions, which can seen in the following figures.
We present the variations of redshifts with SNR of g band (sng), r band (snr) or i band (sni). In the figures, there is a gap lying at the redshift about 1.0 for QSOs, which is also shown in the figures of Z versurs sng/snr/sni. The reason is that the spectral line of Mg II with redshift about 1.0 are often confused with the conjection of the two spectrum arms. To avoid mistaking the bad conjection as Mg II line of QSO, the pipeline and following eyecheck are apt to refuse such spectra as QSO, which results in the missing of some true QSO spectra with redshift about 1.0.
We select targets which have both DR5_v1 and DR3 parameters, and compare their atmospheric parameters (Teff, logg, [Fe/H]) and rv of the two versions in following figures. The average values and standard deviations of differences of the two versions were also shown in the figures.
The histograms of the differences between DR5_v1 and DR3 for atmospherical parameters (Teff, logg, [Fe/H]) and rv are shown as follows. The differences of parameters are divided into four groups according to the snr, presented by different colors.
The difference of parameters between LAMOST DR5_v1 and SDSS (DR14 and APOGEE) are shown in this section.
(1). The following figures show the comparisons of atmospherical parameters (Teff, logg, [Fe/H]) as well as rv between LAMOST DR5 and SDSS DR14. For the parameters of logg, a branch is seen in the bottom-right of the top-right panel. It could be explained by the inhomogeneous distribution of the atmospherical parameters for the ELODIE library. There are holes for giants in the ELODIE library, making the estimations of the initial guess for atmospherical parameters in the giant holes inaccurate.
(2). The histograms of the differences of atmospherical parameters (Teff, logg, [Fe/H]) as well as rv between LAMOST DR5_v1 and APOGEE are provided as follows. In comparison with APOGEE, the differences of parameters are divided into four groups according to snr. We also plot the mean values and the standard deviations corresponding to each snr bin in the figures.