YSO search toward the boundary of the Central Molecular Zone with near-infrared polarimetry

TL;DR

This study used near-infrared polarimetry to identify potential young stellar objects at the boundary of the Central Molecular Zone, revealing a small number of candidates with intrinsic polarization, possibly indicating moderate stellar masses.

Contribution

First near-infrared polarimetric survey targeting the CMZ boundary, identifying potential YSOs and analyzing their polarization properties in this region.

Findings

Identified 10 YSO candidates with spectral energy distributions consistent with young stellar objects.

Many sources are normal stars with heavy interstellar extinction, possibly behind dark clouds.

Mass estimates suggest YSO candidates may have masses between 4-15 solar masses.

Abstract

We have carried out near-infrared polarimetry toward the boundary of the Central Molecular Zone, in the field of (-1.4 deg $\lesssim l \lesssim$ -0.3 deg and 1.0 deg $\lesssim l \lesssim$ 2.9 deg, $|b|\lesssim$ 0.1 deg), using the near-infrared polarimetric camera SIRPOL on the 1.4 m Infrared Survey Facility telescope. We have selected 112 intrinsically polarized sources on the basis of the estimate of interstellar polarization on Stokes $Q/I-U/I$ planes. The selected sources are brighter than $K_S=14.5$ mag and have polarimetric uncertainty $\delta P<1\,%$. Ten of these distinctive polarized sources are fit well with spectral energy distributions of young stellar objects when using the photometry in the archive of the Spitzer Space Telescope mid-infrared data. However, many sources have spectral energy distributions of normal stars suffering heavy interstellar extinction; these might be stars behind dark clouds. Due to the small number of distinctive polarized sources and candidates of young stellar object, we cannot judge if there is a decline of them outside the Central Molecular Zone. Many of massive candidates of young stellar object in the literature have only small intrinsic polarization. This might suggest that their masses are 4-15 M$_{{\rm sun}}$, whose intrinsic polarization has been expected to be small.