The photometric properties of red supergiants (RSGs) in three nearby galaxies NGC 4449, NGC 5055 and NGC 5457 were investigated using near-infrared (JHK) imaging data obtained fromWFCAM UKIRT. The resulting near-infrared photometric catalogue was combined with optical archive data to remove foreground Galactic stars. We found that the foreground stars can be separated from the supergiants in a (i - K, r - i) colour-colour diagram. The (J - K, K)0 colour-magnitude diagrams of the three galaxies are investigated and compared with theoretical isochrones. The majority of RSGs in the three galaxies have common age ranges from log (tyr) = 6.9 to log (tyr) = 7.3, and this indicates that these galaxies have experienced recent star formation within 20 Myr. For NGC 4449 and NGC 5457, the RSGs are spatially correlated with the HII regions, which, however, is not the case for NGC 5055. We were not able to identify a clear metallicity dependence on the colours and the peak absolute magnitudes of the RSGs in the three galaxies. The inaccuracy of our photometric data contributes to the unclear metallicity effect on the colours ofRSGs. Instead, we found a similar colour distribution and a constant peak magnitude of MK =-11.9 for the RSGs in the three galaxies. Therefore, we note that additional spectroscopy data for our RSG candidates, including photometry, are necessary to examine whether the RSG population changes with metallicity.
Bibliographical noteFunding Information:
We are grateful to the anonymous referee for detailed comments that greatly improved this paper. This research was supported by the Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education, Science and Technology (NRF-2015R1A6A3A03016141). YJS is also grateful for the support of the Basic Science Research Program (NRF-2016R1D1A1B01006608). This paper is based in part on data collected by the Subaru Telescope and obtained from SMOKA, which is operated by the Astronomy Data Center, National Astronomical Observatory of Japan. It uses observations obtained with MegaPrime/MegaCam, a joint project of theCanada-France-Hawaii Telescope (CFHT) and CEA/IRFU at the CFHT, which is operated by the National Research Council of Canada (NRC), the Institut National des Science de l'Univers of the Centre National de la Recherche Scientifique (CNRS) of France and the University of Hawaii. This work is based in part on data products produced at Terapix and made available from the Canadian Astronomy Data Centre as part of the Canada-France-Hawaii Telescope Legacy Survey, a collaborative project of NRC and CNRS.
© 2017 The Authors.
All Science Journal Classification (ASJC) codes
- Astronomy and Astrophysics
- Space and Planetary Science