# NGC 1980 is not a foreground population of Orion: Spectroscopic survey of young stars with low extinction in Orion A

## TL;DR

This spectroscopic survey of stars in Orion A clarifies that the foreground population is young and kinematically similar to local clouds, challenging previous assumptions of an older foreground cluster.

## Contribution

The study provides detailed spectral, disk, and kinematic analysis of the Orion A foreground stars, demonstrating they are young and not a separate older population.

## Key findings

- Foreground stars are young (~1-2 Myr) and share kinematics with Orion A clouds.
- Identification of 37 new transition disks and other disk types.
- Foreground population is not an older cluster but part of the ongoing star formation.

## Abstract

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$_{\odot}$, which harbors a flaring disk. Using the H$\alpha$ 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$\pm$7% versus 73$\pm$9%, 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.