We present $UBVI_c$ CCD photometry of the young open cluster Stock 8 with the aim to study the basic properties and star formation scenario in this region. The radius of the cluster is found to be $\sim 6^{\prime}$ ($\sim 3.6$ pc) and the reddening within the cluster region varies from $E(B-V)=0.40$ to 0.60 mag. The cluster is located at a distance of $2.05 \pm 0.10$ kpc. Using H$α$ slitless spectroscopy and 2MASS NIR data we identified H$α$ emission and NIR excess young stellar objects (YSOs), respectively. The colour-magnitude diagrams of these YSOs reveal that majority of these objects have ages between 1 to 5 Myr indicating a non-coeval star formation in the cluster. Massive stars in the cluster region reveal an average age of $\le$ 2 Myr. In the cluster region ($r \le 6^\prime$) the slope of the mass function (MF), $Γ$, in the mass range $\sim 1.0 \le M/M_\odot < 13.4$ can be represented by a power law having a slope of $-1.38\pm0.12$, which agrees well with Salpeter value (-1.35). In the mass range $0.3 \le M/M_\odot < 1.0$, the MF is also found to follow a power law with a shallower slope of $Γ= -0.58\pm 0.23$ indicating a break in the slope of the IMF at $\sim 1 M_\odot$. The slope of the $K$-band luminosity function for the cluster ($r \le 6^\prime$) is found to be $0.31\pm0.02$, which is smaller than the average value ($\sim$ 0.4) obtained for embedded star clusters. A significant number of YSOs are distributed along a Nebulous Stream towards the east side of the cluster. A small cluster is embedded in the Nebulous Stream. The YSOs lying in the Nebulous Stream and in the embedded cluster are found to be younger than the stars in the cluster Stock 8. It appears that star formation activity in the Nebulous Stream and embedded cluster may be independent from that of Stock 8.
In a sample of six young open clusters we investigated 1753 objects using the narrow band, three filter Delta a photometric system resulting in the detection of eleven bona-fide magnetic chemically peculiar (CP) stars and five Be or metal-weak stars. The results for the distant cluster NGC 3105 is most important because of the still unknown influence of the global metallicity gradient of the Milky Way. These findings confirm that CP stars are present in open clusters of very young ages (log t > 6.90) at galactocentric distances up to 11.4 kpc. For all programme clusters the age, reddening, and…
Progressive star formation in the young SMC cluster NGC 602
NGC 602是一个年轻的星团，位于小麦哲伦星云的边缘区域，被称为机翼。远离银河系的主体，并邻接麦哲伦桥，SMC的机翼的特点是气体和恒星含量低。通过哈勃太空望远镜（HST）上的高级巡天照相机（ACS）的深度光学成像，我们发现了一个广泛的前主序（PMS）人口，恒星质量在0.6-3太阳质量范围内。这些低质量的PMS星大约在400万年前与中央星团形成。斯皮策太空望远镜（Spitzer Space Telescope）从红外线阵列相机（IRAC）拍摄的同一区域的图像也揭示了一群年轻恒星物体（YSO），其中一些仍然嵌入星云物质中，其中大多数可能比HST/ACS成像检测到的年轻恒星更近。我们推断，恒星的形成开始在这个地区约4万年前的中央集群的形成，并逐渐向外围的恒星形成目前正在进行中。
