NICSPol: a near-infrared polarimeter for the 1.2-m telescope at Mount Abu Infrared Observatory

Abstract

NICSPol is a near infrared imaging polarimeter developed for the Near Infrared Camera and Spectrograph (NICS), one of the back end instruments of the 1.2 m Cassegrain telescope at the Mount Abu Infrared Observatory (MIRO), India. The polarimeter consists of a rotating wire grid polarizer which is mounted between the telescope optics and NICS. The polarimetric observations are carried out by rotating the polarizer using a motorized mechanism to determine the Stokes parameters, which are then converted into the polarization fraction and polarization angle.Here we report the details of the instrument and the results of observations of IR polarimetric standards. A set of polarized and unpolarized standards were observed using NICSPol over J, H and Ks bands covering 0.8 to 2.5 µm. The observations of polarized standards using NICSPol show that, NICSPol can constrain polarization within ∼1% for sources brighter than ∼16 magnitude in JHKs bands. NICSPol is a general purpose instrument which could be used to study variety of astrophysical sources such as AGNs, Pulsars, XRBs, Supernovae, star forming regions etc. With few NIR polarimeters available world-wide so far, NICSPol would be the first imaging NIR polarimeter in India.

Infrared polarisation study of Lynds 1340: A case of RNO 8

“…Since the NIC-SPol module is the first element after the telescope and before any asymmetric reflection in the instrument, we do not expect any instrumental polarisation. The results of the standard star observations are discussed in the instrument paper of NICSPol (Aarthy et al, 2019). The instrumental polarisation is close to 1% uncertainty in the polarisation fraction.…”

“…In imaging mode, the instrument has a square FOV of 8 x 8 with a spatial scale of 0.5 per pixel. The capabilities of the instrument were enhanced with the addition (Aarthy et al, 2019) of a polarimetric module (NICSPol), between the telescope optics & NICS. The technique of polarimetry is implemented using a 25.0 mm x 25.0 mm wire-grid polarizer (WGP) module at room temperature fixed in a motorised rotator originally used as a field rotator for a small telescope (Pyxis LE field rotator model from Pyxis Instruments).…”