Sejong open cluster survey (SOS) – V. the active star forming region SH 2-255 – 257

Beomdu Lim, Hwankyung Sung, Hyeonoh Hur, Byeong Cheol Lee, Michael S. Bessell, Jinyoung S. Kim, Kang Hwan Lee, Byeong Gon Park, Gwanghui Jeong

Research output: Contribution to journalArticlepeer-review

7 Scopus citations


There is much observational evidence that active star formation is taking place in the Hii regions Sh 2-255 – 257. We present a photometric study of this star forming region (SFR) using imaging data obtained in passbands from the optical to the mid-infrared, in order to study the star formation process. A total of 218 members were identified using various selection criteria based on their observational properties. The SFR is reddened by at least E(B −V) = 0.8 mag, and the reddening law toward the region is normal (RV = 3.1). From the zero-age main sequence fitting method it is confirmed that the SFR is 2.1 ± 0.3 kpc from the Sun. The median age of the identified members is estimated to be about 1.3 Myr from a comparison of the Hertzsprung-Russell diagram (HRD) with stellar evolutionary models. The initial mass function (IMF) is derived from the HRD and the near-infrared (J, J −H) color-magnitude diagram. The slope of the IMF is about Γ = −1.6 ± 0.1, which is slightly steeper than that of the Salpeter/Kroupa IMF. It implies that low-mass star formation is dominant in the SFR. The sum of the masses of all the identified members provides the lower limit of the cluster mass (169M⊙). We also analyzed the spectral energy distribution (SED) of pre-main sequence stars using the SED fitting tool of Robitaille et al., and confirm that there is a significant discrepancy between stellar mass and age obtained from two different methods based on the SED fitting tool and the HRD.

Original languageEnglish (US)
Pages (from-to)343-355
Number of pages13
JournalJournal of the Korean Astronomical Society
Issue number6
StatePublished - 2015


  • Extinction – stars
  • Individual
  • Luminosity function
  • Mass function
  • Open clusters and associations
  • Sh 2-255 – 257 (IC 2162) – dust

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


Dive into the research topics of 'Sejong open cluster survey (SOS) – V. the active star forming region SH 2-255 – 257'. Together they form a unique fingerprint.

Cite this