Abstract
Abstract This work establishes the most complete sample of red supergiants (RSGs) in 12 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 a solid basis to study the properties of RSGs as well as the star formation rate and initial mass function 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 color–magnitude diagram J − K 0 / K 0 of the member stars of the specific galaxy. A total of 2190 RSGs are found in 10 dwarf galaxies, and additionally, 4823 and 2138 RSGs are found in 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.
Highlights
Red supergiants (RSGs) are Population I massive stars in the core-helium burning phase
The initial mass of red supergiants (RSGs) is generally considered to be at least ∼ 8M, while we (Ren et al 2021, Paper I hereafter) suggested that the lower mass limit can be as small as 7M according to the location of RSGs in the color-magnitude diagram, which agrees with the proposal of Yang et al (2019)
This work selects the red supergiants in twelve low-mass galaxies of the Local Group by using mainly the nearinfrared photometry data in the JHK bands taken by United Kingdom Infra-Red Telescope (UKIRT)/Wide Field Camera (WFCAM) from mid-2005 to 2007 and the 2MASS point source catalog as well as the PS1 photometry and Gaia astrometric information
Summary
Red supergiants (RSGs) are Population I massive stars in the core-helium burning phase. Yang et al (2019, 2020) and Yang et al (2021a) separated efficiently the SMC and LMC members from foreground stars by using astrometric solution from Gaia/DR2 and combined a variety of color-magnitude diagrams (CMDs) to identify 1,239 and 2,974 RSGs in SMC and LMC, which is a drastic increase from previous studies (Feast et al 1980; Catchpole & Feast 1981; Wood et al 1983; Pierce et al 2000; Massey 2002; Massey & Olsen 2003; Neugent et al 2012; Gonzalez-Fernandez et al 2015; Yang & Jiang 2011, 2012) This revolutionary progress comes from both more data and the effective method to identify the member stars of the Magellanic Clouds (MCs) since the MC members concentrate on the proper motions expected from the motion of MCs relative to the Galaxy.
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