MaStar Stellar Parameters

Summary

In this site you will find the MaNGA Stellar Library (MaStar, Yan et al., 2019) physical parameters computed using CoSHA, a Code for Stellar Heuristic Assigment of physical parameters: effective temperature (\(T_\mathrm{eff}\)), surface gravity (\(\log{g}\)), iron abundance (\([\mathrm{Fe}/\mathrm{H}]\)) and alpha to iron abundance (\([\alpha/\mathrm{Fe}]\)).

CoSHA implements a Gradient Tree Boosting (GTB) algorithm to train a model for each property. GTB is a type of ensemble algorithm that trains a predefined number of decision trees in a serial way, so that each decision tree improves its predecessor. We used the GTB implementation in scikit-learn. Since we took an heuristic approach we did not changed the hyperparameters default values. In order to test de realiability of CoSHA we compared our results using external data sets such as APOGEE and tried to reproduce the known spatial trends in well-studied planes such as \([\alpha/\mathrm{Fe}]\) versus \([\mathrm{Fe}/\mathrm{H}]\).

To train/test CoSHA we used the first data release of MaStar (Yan et al., 2019) and the Göttingen Spectral Library (GSL, Husser et al., 2013). Both data sets comprise ~30k stars allowing for a wide parameter space coverage:

	min	max
\(T_\mathrm{eff}\) (K)	2300	12000
\(\log{g}\)	-0.025	6.000
\([\mathrm{Fe}/\mathrm{H}]\)	-4.0	1.0
\([\alpha/\mathrm{Fe}]\)	-0.2	1.2

There are some limitations to using such data set to train CoSHA, being the most important the \(T_\mathrm{eff}\) coverage. We expect to expand the parameter space coverage in future updates of the catalogue. See Mejía-Narváez et al., 2021 for a discussion on other potential limitations.

Despite the above-mentioned limitations in the parameter space coverage, CoSHA recovers with high confidence most important parameter space distribution features.

Figure 1. The parameter space distribution of stellar properties for MaStar as predicted by CoSHA. The binned distribution represents the actual sampling of the parameter space by MaStar, while the contours represent the volume corrected distribution. The contours enclose the 25, 50 and 75% (solid line) and the 95% (dashed line) distribution density. We show the average spectra in both cases as well.

Data Format

The catalogue comprises the atmospheric properties of over 22k stars from MaStar, as well as other physical and observed properties in a FITS file binary table. Below we describe the file structure.

There are two HDUs, the PRIMARY which for the moment will be empty and a binary table which contains the actual CATALOGUE:

          
            No.    Name      Ver    Type      Cards   Dimensions   Format
            0  PRIMARY       1 PrimaryHDU       4   ()
            1  CATALOGUE     1 BinTableHDU     67   22771R x 21C   [22A, E, E, 12A, 13A, E, E, E, E, E, E, E, E, E, E, E, E, E, E, E, E]

The first three columns contain identification and exposure information:

          
            name = 'ID'; format = '22A'
            name = 'RECORD'; format = 'E'
            name = 'NEXP'; format = 'E'

The following four columns contain the right ascention, the declination, the distance and the \(B-V\) color excess:

          
            name = 'RA'; format = '12A'; unit = 'HH:MM:SS.ss'
            name = 'DEC'; format = '13A'; unit = 'DD:MM:SS.ss'
            name = 'DIST'; format = 'E'; unit = 'kpc'
            name = 'EBV'; format = 'E'; unit = 'mag'

The next three columns contain the volume correction factor, the signal-to-noise ratio across the wavelength range and the flux normalization computed as the median flux within the 5490 — 5510Å wavelength windows:

          
            name = 'VCORR'; format = 'E'
            name = 'SNR'; format = 'E'
            name = 'FNORM'; format = 'E'; unit = 'erg/s/cm^2/AA'

The next five columns contain the photometric magnitude in the SDSS ugriz passbands:

          
            name = 'USDSS'; format = 'E'; unit = 'mag'
            name = 'GSDSS'; format = 'E'; unit = 'mag'
            name = 'RSDSS'; format = 'E'; unit = 'mag'
            name = 'ISDSS'; format = 'E'; unit = 'mag'
            name = 'ZSDSS'; format = 'E'; unit = 'mag'

The next two columns represent the radial velocity and its associated error as computed by the MaStar collaboration:

          
            name = 'RADVEL'; format = 'E'; unit = 'km/s'
            name = 'RVERR'; format = 'E'; unit = 'km/s'

And the remaining columns represent the physical properties derived by CoSHA:

          
            name = 'TEFF'; format = 'E'; unit = 'K'
            name = 'LOGG'; format = 'E'; unit = 'log/cm/s^2'
            name = 'MET'; format = 'E'; unit = '[Fe/H]'
            name = 'ALPHAM'; format = 'E'; unit = '[alpha/M]'

We plan to include the uncertainties associated with these quantities in a future release of this catalogue. In the mean time, if you use this catalogue, please cite Mejía-Narváez et al., 2021. If you have some requests or complaints please send me an e-mail.

Changelog

v1.0.0: First version.