Exploring the Northern Over-density Region of the Small Magellanic Cloud with MAGIC Photometry and APOGEE Spectroscopy

The Small Magellanic Cloud Northern Over-Density (SMCNOD), a recently discovered feature extending beyond the SMC periphery, has been explained as potentially originating as an extension of the SMC main body, potentially as a result of tidal stripping from SMC-LMC encounters, or, alternatively, the SMCNOD may represent a smaller dwarf galaxy, or the remains of one, being tidally disrupted by the SMC (A. Pieres et al. 2017). Since its discovery by A. Pieres et al. (2017), the SMCNOD has been explored in various ways in attempts to discriminate between these different origin scenarios. In particular, chemistry can be used to establish whether the SMCNOD stars share the same composition as stars in the SMC main body, or whether the SMCNOD is lower metallicity, as might be expected for a dwarf galaxy. Similarly, the kinematics of these stars may give further insights into their connection (or not) with the SMC. Here we apply to these purposes the metallicity information obtained for >800 SMCNOD stars to g ≲ 21.5 using photometry in the narrow-band CaHK filter as part of early data obtained from the DECam MAGIC Survey. We find the metallicity distribution function (MDF) for the SMCNOD to be both extremely broad (ranging from [Fe/H] < -2.5 to < -0.5), but also broadly peaked, with a plateau in the MDF from [Fe/H] < -2.0 to < -1.5. We also use the relatively small sample of SMCNOD stars sampled by the APOGEE survey to help ascertain the kinematics of the region. Together, the chemical and kinematical evidence from MAGIC and APOGEE appears to lend credence to tidal stripping as a viable explanation for the origin of the SMCNOD.