Evolutionary stages and disk properties of young stellar objects in the Perseus cloud. (August 2015)

• Record Type: Journal Article
• Authors: Zhang, Hong-Xin; Gao, Yu; Fang, Min; Yuan, Hai-Bo; Zhao, Ying-He; Chang, Rui-Xiang; Jiang, Xue-Jian; Liu, Xiao-Wei; Luo, A-Li; Ma, Hong-Jun; Shao, Zheng-Yi; Wang, Xiao-Long
• Is Part Of: Research in astronomy and astrophysics. Volume 15:Number 8(2015:Aug.)
• Page Start: 1294
• Page End: 1324
• Publication Date: 2015-08
• Subjects: Astronomy -- Periodicals; Astrophysics -- Periodicals; 520.5
• DOI: 10.1088/1674-4527/15/8/014
• Languages: English
• ISSNs: 1674-4527

Abstract

<abstract> <title>Abstract</title> <p>We investigated the evolutionary stages and disk properties of 211 young stellar objects (YSOs) across the Perseus cloud by modeling their broadband optical to mid-infrared (IR) spectral energy distribution (SED). Our optical <italic>gri</italic> photometry data were obtained from the recently finished Purple Mountain Observatory Xuyi Schmidt Telescope Photometric Survey of the Galactic Anti-center (XSTPS-GAC). About 81% of our sample fall into the Stage II phase which is characterized by having optically thick disks, while 14% into the Stage I phase characterized by having significant infalling envelopes, and the remaining 5% into the Stage III phase characterized by having optically thin disks. The median stellar age and mass of the Perseus YSOs are 3.1 Myr and 0.3 <italic>M</italic><sub>⊙</sub> respectively. By exploring the relationships among the turnoff wave bands λ<sub>turnoff</sub> (longward of which significant IR excesses above the stellar photosphere are observed), the excess spectral index α<sub>excess</sub> as determined for λ > λ<sub>turnoff</sub>, and the disk inner radius <italic>R</italic><sub>in</sub> (determined from SED modeling) for YSOs at different evolutionary stages, we found that the median and standard deviation of α<sub>excess</sub> for YSOs with optically thick disks tend to increase with λ<sub>turnoff</sub>, especially at λ<sub>turnoff</sub> ≥5.8 μm, whereas the median fractional dust luminosities <italic>L</italic><sub>dust</sub>/<italic>L</italic><sub>★</sub> tend to decrease with increasing λ<sub>turnoff</sub>. This points to an inside-out process of disk clearing for small dust grains. Moreover, a positive correlation between α<sub>excess</sub> and <italic>R</italic><sub>in</sub> was found at α<sub>excess</sub> ≳ 0 and <italic>R</italic><sub>in</sub> ≳ 10 × the dust sublimation radius <italic>R</italic><sub>sub</sub>, irrespective of λ<sub>turnoff</sub>, <italic>L</italic><sub>dust</sub>/<italic>L</italic><sub>★</sub> and disk flaring. This suggests that the outer disk flaring either does not evolve synchronously with the inside-out disk clearing of small dust grains or has little appreciable influence on the spectral slopes at λ ≲ 24 μm. About 23% of our YSO disks are classified as transitional disks, which have λ<sub>turnoff</sub> ≥ 5.8 μm and <italic>L</italic><sub>dust</sub>/<italic>L</italic><sub>★</sub> > 10<sup>−3</sup>. The transitional disks and full disks occupy distinctly different regions on the <italic>L</italic><sub>dust</sub>/<italic>L</italic><sub>★</sub> vs. α<sub>excess</sub> diagram. Taking <italic>L</italic><sub>dust</sub>/<italic>L</italic><sub>★</sub> as an approximate discriminator of disks with (>0.1) and without (<0.1) considerable accretion activity, we found that 65% and 35% of the transitional disks may be consistent with being dominantly cleared by photoevaporation and dynamical interaction with giant planets respectively. None of our transitional disks have α<sub>excess</sub> (<0.0) or <italic>L</italic><sub>dust</sub>/<italic>L</italic><sub>★</sub> (>0.1) values that would otherwise be suggestive of disk clearing dominanted by grain growth.</p> </abstract>