TY - JOUR
T1 - NGC 1980 is not a foreground population of Orion
AU - Fang, Min
AU - Kim, Jinyoung Serena
AU - Pascucci, Ilaria
AU - Apai, Daniel
AU - Zhang, Lan
AU - Sicilia-Aguilar, Aurora
AU - Alonso-Martinez, Miguel
AU - Eiroa, Carlos
AU - Wang, Hongchi
PY - 2017/3/20
Y1 - 2017/3/20
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, one globally depleted disk candidate, and 7 probable young debris disks. We discover an object with a mass less than 0.018-0.030 M?, which harbors a flaring disk. Using the H? emission line, we characterize the accretion activity of the sources with disks, and confirm that fraction of accreting TDs is lower than that of optically thick disks (46� versus 73�, respectively). Using kinematic data from the Sloan Digital Sky Survey and APOGEE INfrared Spectroscopy of 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 around 1-2 Myr, which is similar to the one 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, one globally depleted disk candidate, and 7 probable young debris disks. We discover an object with a mass less than 0.018-0.030 M?, which harbors a flaring disk. Using the H? emission line, we characterize the accretion activity of the sources with disks, and confirm that fraction of accreting TDs is lower than that of optically thick disks (46� versus 73�, respectively). Using kinematic data from the Sloan Digital Sky Survey and APOGEE INfrared Spectroscopy of 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 around 1-2 Myr, which is similar to the one 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 - Planetary systems: protoplanetary disks
KW - Stars: pre-main sequence
UR - https://arxiv.org/abs/1703.06948
U2 - 10.3847/1538-3881/aa647b
DO - 10.3847/1538-3881/aa647b
M3 - Article
SN - 0004-6256
VL - 153
JO - Astronomical Journal
JF - Astronomical Journal
IS - 4
ER -