Disk Lifetimes as a Function of Stellar Mass and Environments in Young Stellar Clusters

拉达博士和她的团队研究了星周盘的寿命与恒星质量和星团环境的关系。这对于理解圆盘向行星系统的发展是很重要的。研究人员将近红外FLAMINGOS光谱法和光度法结合起来，利用存档的中红外斯皮策光度法，研究了英仙座、猎户座a、猎户座B和monob1分子云中嵌入的8个年轻星团（大约1-2百万年）的恒星群。星团的样本涵盖了大小、恒星数量、恒星密度和形态的范围。光谱数据提供了消光、恒星光谱类型、年龄中位数、年龄差、恒星质量和每个星团内恒星的分布。结合Spitzer中红外光度法，得到了源的固有红外过剩量，这是区分有圆盘和包膜的源、有光学厚盘的源、有光学薄的弱盘的源和无圆盘的源的一个指标。盘的寿命可能取决于恒星质量和星团环境，这里的目标是评估有盘的恒星比例对恒星质量的依赖，以及评估盘比例对星团环境（如星团密度、恒星人口、形态和中位年龄）的依赖。本研究还为研究生和青年科学家提供天文研究方面的培训，并参与教育推广活动。

Dr. Lada and her team study the dependence of circumstellar disks lifetimes on stellar mass and stellar cluster environment. This is important to understand the disk development into planetary systems. The researchers combine near-infrared FLAMINGOS spectroscopy and photometry to study the stellar populations for a sample of eight young (about 1-2 million years old) embedded clusters in the molecular clouds Perseus, Orion A, Orion B and Mon OB1 with archival mid-IR Spitzer photometry. The sample of clusters covers a range of sizes, stellar populations, stellar densities and morphologies. The spectroscopic data provide extinction, stellar spectral types, median ages, age spreads, stellar masses and distribution of stars within each cluster. The derived extinction is combined with Spitzer mid-infrared photometry to obtain the intrinsic infrared excess for the sources, which is an indicator for distinguishing sources with disks and envelopes, sources with optically thick disks, sources with optically thin anemic disks, and diskless sources. The disks lifetimes might depend on both stellar mass and cluster environment and the goals here are to assess the dependence of fraction of stars with discs on stellar mass, and to evaluate the dependence of disks fraction on cluster environments such as cluster stellar density, stellar population, morphology, and median ages. This research also provides training for graduate students and young scientists in astronomical research, and they participate in educational outreach activities.