Tac's Page

　To date, several concepts for a "z-machine" have been developed and/or employed for different wavelength regimes. For example, the frequency range of the Zpectrometer (Harris et al. 2007) on the Green Bank Telescope (GBT) is 28.5-34.5 GHz, and this has been used to successfully observe CO (J = 1-0) toward four SMGs (Harris et al. 2010). The Redshift Search Receiver (RSR; Erickson et al. 2007) is a 74-110 GHz detector and spectrometer for the Large Millimeter Telescope (LMT), but in the early stage of its use it has been installed on the Haystack 37-m telescope, as well as on the Five College Radio Astronomy Observatory (FCRAO) 14-m telescope. Chung et al. (2009) have already observed CO (J = 1-0) toward 29 ultraluminous infrared galaxies (ULIRGs) using the RSR on the FCRAO 14-m telescope. Z-Spec (Glenn et al. 2007) is a 185-293 GHz band receiver on the CSO, which Bradford et al. (2009) have used to present the first broadband λ = 1 mm spectrum toward the z = 2.56 Cloverleaf quasar. The redshift (z) and early universe spectrometer (ZEUS; Stacey et al. 2007) is an echelle grating spectrometer in the submillimeter band. Moreover, the eight mixer receivers (EMIR) on the IRAM 30-m telescope and Weiβ et al. (2009) have been used to detect CO (J = 3-2) in the 3-mm band and CO (J = 5-4) in the 2-mm band from an optically/ultraviolet faint SMG. They were able to successfully determine the redshift of the SMG for the first time.
　We have developed a new z-machine for the Nobeyama Radio Observatory (NRO) 45-m radio telescope in 100-GHz band. The detectors of this receiver are waveguide-type sideband-separating (2SB) mixers that can observe the upper sideband (USB) and lower sideband (LSB) simultaneously. The receiver has a wide radio frequency (RF) range and is suitable for the z-machine. The backend systems are newly developed wide-band digital spectrometers, which have a highly flexible FX-type spectrometer that allows a maximum bandwidth of 32 GHz (2 GHz x 16 arrays) on 4,096 spectral channels. The 2SB mixer is adopted for a part of the frequency band of the Atacama large millimeter submillimeter array (ALMA), which suggests that the 2SB receiver systems are more efficient than other SSB receivers (e.g., Nakajima et al. 2007; 2008). Over an RF range of 80-116 GHz, the SSB receiver noise temperatures of the mixers are lower than about 50 K. The image rejection ratios (IRRs) are greater than approximately 10 dB in most of the same range. Moreover, our z-machine has two beams, and the beam separation is approximately 45" therefore, the two beams can be turned on in an alternate manner for observation using the position switch. This can significantly reduce the amount of dead time and facilitate the efficient observation of point sources.
　Using the newly developed z-machine for the 45-m telescope, we observed a 12CO (J= 3-2) emission line toward the cloverleaf as confirmation of the performance of the receiver system. This is the first astronomical observation that has been made using a two-beam 2SB SIS receiver system in the 100-GHz band. The SSB noise temperature of the system, including the atmosphere, is typically 150-300 K.