Sejong Open Cluster Survey (SOS) – II. IC 1848 cluster in the H ii region W5 West

Abstract

IC 1848 is one of the young open clusters in the giant star forming Cas OB6 association. Several interesting aspects relating to star formation processes in giant star forming regions attracted us to study the initial mass function (IMF), star formation mode, and properties of pre-main sequence stars (PMS). A U BV I and Hα photometric study of the young open cluster IC 1848 was conducted as part of the "Sejong Open cluster Survey" (SOS). We have selected 105 early-type members from photometric diagrams. Their mean reddening is E(B − V ) = 0.660 ± 0.054 mag. Using the published photometric data with near-and mid-infrared archival data we confirmed the normal reddening law (R V = 3.1) toward the cluster (IC 1848). A careful zero-age main sequence fitting gives a distance modulus of V 0 − M V = 11.7 ± 0.2 mag, equivalent to 2.2 ± 0.2 kpc. Hα photometry and the list of young stellar objects identified by Koenig et al. permitted us to select a large number of PMS stars comprising 196 Hα emission stars, 35 Hα emission candidates, 5 Class I, 368 Class II, and 24 transition disk candidates. From the Hertzsprung-Russell diagram using stellar evolution models, we estimate an age of 5 Myr from several evolved stars and 3 Myr from the PMS stars. The IMF was derived from stars with mass larger than 3M , and the slope is slightly steeper (Γ = −1.6 ± 0.2) than the Salpeter/Kroupa IMF. Finally, we estimated the mass accretion rate of PMS stars with a UV excess. The mean mass accretion rate is about 1.4 × 10 −8 M yr −1 in the mass range of 0.5M to 2M , whereas intermediate-mass stars ( 2.5M ) exhibit a much higher accretion rate oḟ M > 10 −6 M yr −1 .

An Optical and Infrared Photometric Study of the Young Open Cluster IC 1805 in the Giant H ii Region W4* †

“…These relations have been successfully used to determine the R V of several young open clusters. The color excess ratios of several young open clusters have been well fitted to a single line with a normal R V (Kook et al 2010;Lim et al 2011;Sung et al 2013a;Lim et al 2014aLim et al ,b, 2015a. However the color excess ratios of some extremely young open clusters are best fitted by a combination of two lines with different slopes, which means that two different media with different extinction properties exist in the line-of-sight, i.e.…”

“…Currently, two stellar evolution models of massive stars with stellar rotation are used in the mass and age estimate of massive stars, and these are compared in Sung et al (2013a). For consistency with the mass and age scale of massive stars with previous studies of our group (Hur et al 2012;Sung et al 2013a;Lim et al 2014aLim et al ,b, 2015aHur et al 2015), the age and mass of massive stars are determined using the stellar evolution models of Ekström et al (2012).…”

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

“…The equivalent widths of spectral lines can be underestimated by excess continuum emission due to mass accretion activity (Calvet & Gullbring 1998;Lim et al 2014a ) were measured by integrating the observed emission lines. In the case of the He I line, we computed the equivalent width of the line core within a narrow wavelength range of 0.7 Å to minimize the contribution of the error in the continuum level.…”

High-resolution Near-infrared Observations of a Small Cluster Associated with a Bright-rimmed Cloud in W5

“…The distance range of W5 in the literature is 1.7-2.3 kpc (Sharpless 1955;Johnson et al 1961;Ishida 1970;Georgelin & Georgelin 1976;Chauhan et al 2011). In this paper, we adopt the most recent value of 2.2 kpc for the open cluster IC1848 (Lim et al 2014) as the distance to SFO12 and its exciting stars in W5-W. Four O stars (BD +60 586 A, HD 237019, HD 17520 and HD 17505; Koenig et al 2008) are present in the W5-W and the main exciting star of the bright rim of SFO 12 is BD +60 586 A (O7V; Sota et al 2011), as seen in Figure 1. The projected distance between SFO 12 and the main exciting star is ∼4.4 pc.…”