TY - JOUR
T1 - NGC 1980 Is Not a Foreground Population of Orion
T2 - Spectroscopic Survey of Young Stars with Low Extinction in Orion A
AU - Fang, Min
AU - Kim, Jinyoung Serena
AU - Pascucci, Ilaria
AU - Apai, Dániel
AU - Zhang, Lan
AU - Sicilia-Aguilar, Aurora
AU - Alonso-Martínez, Miguel
AU - Eiroa, Carlos
AU - Wang, Hongchi
N1 - Funding Information:
This research uses data obtained through the Telescope Access Program (TAP), which has been funded by the National Astronomical Observatories of China, the Chinese Academy of Sciences (the Strategic Priority Research Program The Emergence of Cosmological Structures Grant No. XDB09000000), and the Special Fund for Astronomy from the Ministry of Finance. Observations reported here were obtained at the MMT Observatory, a joint facility of the University of Arizona and the Smithsonian Institution.
Publisher Copyright:
© 2017. The American Astronomical Society. All rights reserved..
PY - 2017/4
Y1 - 2017/4
N2 - We perform a spectroscopic survey of the foreground population in Orion A with MMT/Hectospec. We use these data, along with archival spectroscopic data and photometric data, to derive spectral types, extinction values, and masses for 691 stars. Using the Spitzer Space Telescope data, we characterize the disk properties of these sources. We identify 37 new transition disk (TD) objects, 1 globally depleted disk candidate, and 7 probable young debris disks. We discover an object with a mass of less than 0.018-0.030 M o, which harbors a flaring disk. Using the Hα emission line, we characterize the accretion activity of the sources with disks, and confirm that the fraction of accreting TDs is lower than that of optically thick disks (46% ± 7% versus 73% ± 9%, respectively). Using kinematic data from the Sloan Digital Sky Survey and APOGEE INfrared Spectroscopy of the Young Nebulous Clusters program (IN-SYNC), we confirm that the foreground population shows similar kinematics to their local molecular clouds and other young stars in the same regions. Using the isochronal ages, we find that the foreground population has a median age of around 1-2 Myr, which is similar to that of other young stars in Orion A. Therefore, our results argue against the presence of a large and old foreground cluster in front of Orion A.
AB - We perform a spectroscopic survey of the foreground population in Orion A with MMT/Hectospec. We use these data, along with archival spectroscopic data and photometric data, to derive spectral types, extinction values, and masses for 691 stars. Using the Spitzer Space Telescope data, we characterize the disk properties of these sources. We identify 37 new transition disk (TD) objects, 1 globally depleted disk candidate, and 7 probable young debris disks. We discover an object with a mass of less than 0.018-0.030 M o, which harbors a flaring disk. Using the Hα emission line, we characterize the accretion activity of the sources with disks, and confirm that the fraction of accreting TDs is lower than that of optically thick disks (46% ± 7% versus 73% ± 9%, respectively). Using kinematic data from the Sloan Digital Sky Survey and APOGEE INfrared Spectroscopy of the Young Nebulous Clusters program (IN-SYNC), we confirm that the foreground population shows similar kinematics to their local molecular clouds and other young stars in the same regions. Using the isochronal ages, we find that the foreground population has a median age of around 1-2 Myr, which is similar to that of other young stars in Orion A. Therefore, our results argue against the presence of a large and old foreground cluster in front of Orion A.
KW - accretion, accretion disks
KW - protoplanetary disks
KW - stars: pre-main sequence
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U2 - 10.3847/1538-3881/aa647b
DO - 10.3847/1538-3881/aa647b
M3 - Article
AN - SCOPUS:85017290724
VL - 153
JO - Astronomical Journal
JF - Astronomical Journal
SN - 0004-6256
IS - 4
M1 - 188
ER -