We are developing an ultra-wideband spectroscopic instrument, DESHIMA (Deep Spectroscopic HIgh-redshift Mapper), based on the technologies of an on-chip filterbank and Microwave Kinetic Inductance Detector (MKID) in order to investigate dusty starburst galaxies in the distant universe at millimeter and submillimeter wavelength. On-site experiment of prototype DESHIMA was performed using the ASTE 10-m telescope (Ezawa et al. 2008) in Oct. and Nov. 2017. In this session, we used 49 frequency channels in 332-377 GHz band (frequency step of $\sim$1 GHz), and successfully detected astronomical molecular lines such as the redshifted CO (J=3-2) line of VV114, a luminous infrared galaxy at z=0.020. We present a reliable responsivity model that converts frequency responses of the MKIDs to line-of-sight brightness temperature. Using a skydip dataset under various precipitable water vapors (PWV, 0.4-3.0 mm, obtained by the ALMA radiometers, Nikolic et al. 2013), we estimated the responsivity model parameters and PWVs iteratively. First, we estimated line-of-sight brightness temperature from the ALMA PWVs and elevation angles of the telescope using an atmospheric transmission model (ATM, Pardo et al. 2001) and obtained two fitting parameters of the responsivity model for each MKID. Then, we estimated PWVs (DESHIMA PWVs) using frequency response of MKIDs. Finally, we fit the parameters again assuming the DESHIMA PWVs. As a result of analysis, we obtained temperature calibration uncertainty of $1\sigma \sim$4% typically, which was smaller than those of other photometric errors (e.g., chopper wheel method, planet flux model, 5-20%).
|Less than 5 years of experience since completion of Ph.D||N|
|Student (Ph.D., M.Sc. or B.Sc.)||N|