The Sample of Red Supergiants in Twelve Low-Mass Galaxies of the Local Group

Abstract

This work establishes the most complete sample of red supergiants (RSGs) in twelve low-mass galaxies (WLM, IC 10, NGC 147, NGC 185, IC 1613, Leo A, Sextans B, Sextans A, NGC 6822, Pegasus Dwarf, SMC and LMC) of the Local Group, which forms the solid basis to study the properties of RSGs as well as the star formation rate (SFR) and initial mass function (IMF) of the galaxies. After removing the foreground dwarf stars by their obvious branch in the near-infrared color-color diagram ((J − H) 0 /(H − K) 0 ) with the UKIRT/WFCAM and 2MASS photometry as well as the Gaia/EDR3 measurements of proper motion and parallax, RSGs are identified from their location in the colormagnitude diagram (J − K) 0 /K 0 of the member stars of the specific galaxy. A total of 2,190 RSGs are found in ten dwarf galaxies, and additionally 4,823 and 2,138 RSGs in the LMC and SMC respectively. The locations of the tip of the red giant branch in the (J − K) 0 /K 0 diagram are determined to serve as an indicator of the metallicity and distance modulus of the galaxies.

Dependence of pulsation mode of Cepheids on metallicity

“…The stars in the samples are examined with the Gaia astrometric information preliminarily in order to confirm their membership. The criteria is the same as that introduced in Yang et al ( 2019), Yang et al (2020), andRen et al (2021b). In brief, a star in SMC or LMC is considered to be a foreground star if its proper motion is beyond 5σ of the peak value of the host galaxy or its distance is closer than 30 kpc.…”