The Initial Mass Function and Young Brown Dwarf Candidates in NGC 2264. Iv. The Initial Mass Function and Star Formation History

Abstract

We have studied the star formation history and the initial mass function (IMF) using the age and mass derived from spectral energy distribution (SED) fitting and from color-magnitude diagrams. We also examined the physical and structural parameters of more than 1,000 pre-main sequence stars in NGC 2264 using the on-line SED fitting tool (SED fitter) of Robitaille et al.We have compared the physical parameters of central stars from SED fitter and other methods. The temperature of the central star is, in many cases, much higher than that expected from its spectral type. The mass and age from SED fitter are not well matched with those from color-magnitude diagrams. We have made some suggestions to improve the accuracy of temperature estimates in SED fitter.In most cases these parameters of individual stars from SED fitter in a star forming region (SFR) or in the whole cluster showed nearly no systematic variation with age or with any other relevant parameter. On the other hand, the median properties of stars in NGC 2264 SFRs showed an evident evolutionary Subject headings: open clusters and associations: individual (NGC 2264) -stars: luminosity function, mass function

A Constraint on the Formation Timescale of the Young Open Cluster NGC 2264: Lithium Abundance of Pre-Main Sequence Stars

“…It may imply the presence of an age difference among these subclusters. Sung & Bessell (2010) suggested an outside-in sequential star formation scenario within NGC 2264 from the age distribution of the PMS stars. A nearby supernova Siess et al (2000) and Baraffe et al (2015), respectively.…”

“…If the star formation history suggested by Sung & Bessell (2010) is true, an age spread of 3-4 Myr may be the time duration of the star formation activity propagated from the halo to the S Mon region. A large number of stars in the Spokes and Cone nebula regions are still embedded in the cloud.…”

“…The underlying initial mass function was assumed to be G = -1.7 (a = 2.7-Sung & Bessell 2010). The age of the model clusters was set to 3 Myr (Sung & Bessell 2010), and age spreads of 0-6 Myr were applied to the clusters with a 1 Myr interval, respectively. The evolutionary models of Baraffe et al (2015) for PMS stars were adopted to assign the effective temperature and Li abundance of individual stars of the model clusters.…”

“…The high number ratio of Class I to Class II objects indicates that the subclusters in the regions have been formed recently relative to the other regions. If we adopt the median age of the individual subclusters from Table 2 of Sung & Bessell (2010), the age difference between the halo and Spokes + Cone nebula regions is about 1 Myr. Hence, the stellar population in the entire region of NGC 2264 may have formed within 5 Myr.…”

Deep near-infrared adaptive-optics observations of a young embedded cluster at the edge of the RCW 41 H II region

“…We can compare the IMF derived for the young cluster embedded within RCW 41 with those of other well studied young clusters, such as IC 348 and the Trapezium (Muench et al 2003;Luhman et al 2000), Chamaeleon I (Luhman et al 2007), NGC 2024(Levine et al 2006, NGC 2264 (Sung et al 2010), NGC 6611 (Oliveira et al 2009), NGC 7538 (Mallick et al 2014, W3 Main (Ojha et al 2009;Bik et al 2014), and NGC 3603 (Harayama et al 2008). As for these clusters, RCW 41 has an IMF that rise in number with decreasing mass into the subsolar regime, with Salpeterlike power-law slopes.…”