We present the results of near-infrared (JHK) direct and polarimetric imaging of the Serpens cloud core. We detected approximately 200 stars with completeness limits of J=15.5 mag, H=14.75 mag, and K=14.0 mag in a 92.4 arcmin2 region. Although the sources with near-infrared excess distinguished from JHK colors are distributed over the entire region surveyed, there is a concentration toward the SE core. The lower limit of the visual extinction toward the cloud core is estimated to be 24 mag from the absence of the field stars. The polarization of 12 compact sources was measured; 10 sources are young stellar objects, one is a background star candidate, and the other is unidentified. The polarization of the young stellar object (YSO) is most likely due to scattering in the associated nebulae; their position angles are therefore perpendicular to the extension of the nebula associated with each YSO. In contrast, the polarization of the background star candidate CK2 is about 40°. Our results do not support the previously suggested model that the magnetic field runs in a NW-SE direction. The color and polarization patterns suggest that the bright near-infrared reflection nebula in the core is mainly composed of two parts, one illuminated by SVS 2 (the Serpens Reflection Nebula, SRN), and the other by the infrared bright star SVS 20. The appearance of SRN changed between 1991 and 1992. Both surface brightness and polarization patterns in SRN are interpreted as results of the interaction between the outflow and the circumstellar material around SVS 2, showing the inhomogeneity of the surrounding cloud density.
All Science Journal Classification (ASJC) codes
- Astronomy and Astrophysics
- Space and Planetary Science