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

Abstract

Aims. We investigate the star formation activity in a young star forming cluster embedded at the edge of the RCW 41 H ii region. As a complementary goal, we aim to demonstrate the gain provided by wide-field adaptive optics (WFAO) instruments to study young clusters. Methods. We used deep, JHK s images from the newly commissioned Gemini-GeMS/GSAOI instrument, complemented with Spitzer IRAC observations, in order to study the photometric properties of the young stellar cluster. GeMS is a WFAO instrument that delivers almost diffraction-limited images over a field of ∼2 across. The exquisite angular resolution allows us to reach a limiting magnitude of J ∼ 22 for 98% completeness. The combination of the IRAC photometry with our JHK s catalog is used to build color−color diagrams, and select young stellar object (YSO) candidates. The JHK s photometry is also used in conjunction with pre-main sequence evolutionary models to infer masses and ages. The K-band luminosity function is derived, and then used to build the initial mass function (IMF) of the cluster. Results. We detect the presence of 80 YSO candidates. Those YSOs are used to infer the cluster age, which is found to be in the range 1 to 5 Myr. More precisely, we find that 1/3 of the YSOs are in a range between 3 to 5 Myr, while 2/3 of the YSO are ≤3 Myr. When looking at the spatial distribution of these two populations, we find evidence of a potential age gradient across the field that suggests sequential star formation. We construct the IMF and show that we can sample the mass distribution well into the brown dwarf regime (down to ∼0.01 M ). The logarithmic mass function rises to peak at ∼0.3 M , before turning over and declining into the brown dwarf regime. The total cluster mass derived is estimated to be 78 ± 18 M , while the ratio derived of brown dwarfs to star is 18 ± 5%. When comparing it with other young clusters, we find that the IMF shape of the young cluster embedded within RCW 41 is consistent with those of Trapezium, IC 348, or Chamaeleon I, except for the IMF peak, which happens to be at higher mass. This characteristic is also seen in clusters like NGC 6611 or even Taurus. These results suggest that the medium-to-low mass end of the IMF possibly depends on environment.

Young Cluster Berkeley 59: Properties, Evolution, and Star Formation

“…We can however make a relatively good estimate from the present data as they reach down to 0.2 M . Most of the observations of the high-mass SFRs in our Galaxy are consistent with an IMF that declines below 0.2 M (e.g., Luhman 2007;Andersen et al 2008;Oliveira et al 2009;Sung & Bessell 2010;Neichel et al 2015;Jose et al 2017). Thus the contribution below it is not expected to substantially alter the estimate of the total mass of the cluster if we assume that the cluster contains stars down to 0.08 M .…”

The Low-mass Population in the Young Cluster Stock 8: Stellar Properties and Initial Mass Function

“…9 shows the K-band luminosity function of the cluster. The shape of the luminosity function appears remarkably similar to the well studied star forming regions such as Trapezium (Muench et al 2002), NGC2024 (Spezzi et al 2015), L1641 (Fang et al 2012), RCW41 (Neichel et al 2015), NGC6611 (Oliveira et al 2009). For comparison, the K-band luminosity function of Trapezium cluster from Muench et al (2002) is overplotted in Fig.…”

Star formation in the filament of S254-S258 OB complex: a cluster in the process of being created

“…If we assume that the cloud has already formed stars down to the hydrogen-burning limit (i.e., ∼0.08 M ), this would not drastically alter the SFE of the complex, because most of the observations in our Galaxy are consistent with an IMF that declines below 0.1 M (e.g., Lada 2005;Andersen et al 2008;Oliveira et al 2009;Neichel et al 2015). Thus, we do not expect a large population of Class II and Class I YSOs below our completeness limit.…”