IFU front unit

Fiber Integral Field Unit for IFOSC(FIFUI) has been developed for IUCAA Faint Object Spectrometer and Camera (IFOSC), the main backend instrument on IUCAA 2m Telescope at Girawali, Pune, India.

This IFU would enable IFOSC to perform 2-dimensional spectroscopy of extended astronomical objects and will be used as one of the modes of IFOSC. It is based on the idea of connecting the focal plane of the telescope with the spectrograph slit using a fibre bundle. In this way when an extended object is observed each fibre receives light coming from a particular region of the object. Each individual spectrum appears well separated on the detector; therefore, spatial information and spectral information are collected simultaneously. In addition, the IFU uses some coupling optics to realize a 2-D interface between the focal plane of the telescope and the spectrograph slit.

IFU lamp spectrum

                                                          Fig:  Lamp spectra obtained from IFU + IFOSC combination.


The IFU is optimized for the visible spectrum and for a field of view of ∼ 13 arc-seconds × 6 arc-seconds on the sky. It offers three different spatial sampling scales, 0.8 arc seconds per fibre, 1.0 arc-second per fibre and 1.2 arc-seconds per fibre. The Lenslet + Fibre based approach has been used in the realization of the IFU, in which the field of view is sampled by 100 tiny lenslets (diameter of 2.1 mm) and optical fibres. The spectral resolution provided by this IFU assisted Spectrograph would be ∼ 8 − 10 Angstrom and one of its key science motivations is to study the kinematics of Ultra Luminous Infrared Galaxies (ULIRGs) at redshift ∼ 0.05 − 0.1.