Speaker
Description
Far-infrared (IR) spectroscopic observations are essential to study physical properties of star-forming regions under various environments, for example. The 158-μm line emission of singly-ionized carbon ([CII]) is one of the strongest far-IR lines as a major cooling channel of the gas-phase interstellar medium, and thus is a key to determine the evolution of ionized and atomic gas phases into the molecular gas phase in which stars are formed. Despite the importance, the origin of the [CII] line emission is spatially unclear yet due to poor spatial resolutions in the far-IR range.
With a balloon-borne far-IR telescope, we have been observing the [CII] line emission from galactic star-forming regions in collaboration with Tata Institute of Fundamental Research in India. The focal plane instrument is a Fabry-Perot spectrometer (FPS) tuned to the [CII] line emission. The FPS mainly consists of a Fabry-Perot (FP) module and a single-pixel stressed Ge photoconductor. The both components are installed into a very limited space to cool them down at 2 K. Because such Ge photoconductors need a large stressing mechanism to extend the cut-off wavelength up to ~200 μm, it is practically difficult to make a compact and large array format. Due to the reason, the single pixel has been used and limits a spatial resolution which does not achieve the diffraction limit.
To break through the limitation, by introducing the room-temperature surface-activated bonding (SAB) technique, we successfully developed a Ge Blocked Impurity Band (BIB) array detector that is sensitive out to ~200 μm without any large stressing mechanisms; the SAB technique enables us to realize a Ge BIB array detector hybridized with an FD-SOI cryo-CMOS readout circuit and thus makes them more compact. By introducing a 5x5 pixel Ge BIB array detector in combination with a new FP module, we are developing a new FPS with high-spatial and spectral resolutions. Then, the spatial resolution will be improved by a factor of ~2. Furthermore, owing to over Nyquist sampling of a diffraction pattern, a super spatial resolution will be achieved by a data analysis process. Here, we will give a presentation of the current development status on the new FPS and of expected scientific impacts from [CII] observations with the new FPS.
