Logo
ScienceStack
Table of Contents
Fetching ...
Sign In

The LMT 2 Millimeter Receiver System (B4R). I. Overview and Results of Science Demonstration

Ryohei Kawabe, Takeshi Sakai, Kunihiko Tanaka, Akio Taniguchi, Bunyo Hatsukade, Yoichi Tamura, Yuki Yoshimura, Tatsuya Takekoshi, Tai Oshima, Masato Hagimoto, Teppei Yonetsu, Kotomi Taniguchi, Kotaro Kohno, Hiroyuki Maezawa, David H. Hughes, Peter F. Schloerb, Edgar Colín-Beltrán, Miguel Chávez Dagostino, Víctor Gómez-Rivera, Arturo I. Gómez-Ruiz, Gopal Narayanan, Iván Rodríguez-Montoya, David Sánchez-Argüelles, Yoshito Shimajiri, Kamal Souccar, Min S. Yun, Tom J. L. C. Bakx, Kevin C. Harrington, Shinji Fujita, Fumitaka Nakamura, O. S. Rojas-García, Alfredo A. Montaña Barbano, Javier Zaragoza-Cardiel

Abstract

We report on the results of the on-sky test and science demonstration conducted with the 2 mm receiver system, B4R, on the 50 m Large Millimeter Telescope (LMT), located at an altitude of 4600 m in Mexico. The B4R receiver was developed based on the dual-polarization sideband-separating mixer technology of the Atacama Large Millimeter/submillimeter Array, and is equipped with a fast Fourier transform digital spectrometer, XFFTS. The primary science objective is the spectroscopic redshift identification of high-redshift dusty star-forming galaxies, complementing the existing 3 mm Redshift Search Receiver by enabling the detection of multiple carbon monoxide lines. Additionally, the B4R receiver broadens the range of science cases possible with the LMT, including astrochemistry, as the 2 mm band encompasses unique molecular lines such as deuterated molecules and shock tracers. During on-site commissioning in 2018 and 2019, we successfully demonstrated on-the-fly mapping and position-switching observations toward the Orion Molecular Cloud 1 and bright high-redshift dusty star-forming galaxies, respectively. We confirmed that the installed B4R system largely met its basic performance specifications. Furthermore, we measured the LMT's aperture efficiencies across the entire B4R frequency range (130-160 GHz), finding them to be roughly consistent with expectations based on a surface accuracy of 100 $μ$m and the receiver optics design. These results with the B4R will enable the most sensitive single-dish spectroscopic observations at 2 mm using the LMT.

The LMT 2 Millimeter Receiver System (B4R). I. Overview and Results of Science Demonstration

Abstract

We report on the results of the on-sky test and science demonstration conducted with the 2 mm receiver system, B4R, on the 50 m Large Millimeter Telescope (LMT), located at an altitude of 4600 m in Mexico. The B4R receiver was developed based on the dual-polarization sideband-separating mixer technology of the Atacama Large Millimeter/submillimeter Array, and is equipped with a fast Fourier transform digital spectrometer, XFFTS. The primary science objective is the spectroscopic redshift identification of high-redshift dusty star-forming galaxies, complementing the existing 3 mm Redshift Search Receiver by enabling the detection of multiple carbon monoxide lines. Additionally, the B4R receiver broadens the range of science cases possible with the LMT, including astrochemistry, as the 2 mm band encompasses unique molecular lines such as deuterated molecules and shock tracers. During on-site commissioning in 2018 and 2019, we successfully demonstrated on-the-fly mapping and position-switching observations toward the Orion Molecular Cloud 1 and bright high-redshift dusty star-forming galaxies, respectively. We confirmed that the installed B4R system largely met its basic performance specifications. Furthermore, we measured the LMT's aperture efficiencies across the entire B4R frequency range (130-160 GHz), finding them to be roughly consistent with expectations based on a surface accuracy of 100 m and the receiver optics design. These results with the B4R will enable the most sensitive single-dish spectroscopic observations at 2 mm using the LMT.

Paper Structure

This paper contains 21 sections, 11 figures, 5 tables.

Table of Contents

  1. Introduction
  2. B4R System and Installation
  3. The 2 mm Receiver
  4. Digital Spectrometer
  5. Installation, On-sky Test, and Science Demonstration
  6. Results of On-sky Test
  7. Beam Map
  8. Aperture Efficiency
  9. Pointing
  10. Baseline Ripple Suppression
  11. Other Issues and Improvements
  12. Results of Science Demonstration
  13. PSW Observations of High-$z$ HyLIRGs
  14. OTF Mapping of OMC-1
  15. Spectral Scan of Orion-KL
  16. ...and 6 more sections

Figures (11)

  • Figure 1: Left: photo of the B4R in the LMT Receiver Cabin. Right: drawing of the B4R and its warm optics.
  • Figure 2: Block diagram of the B4R. The upper part is installed in the receiver cabin, and the lower part is located in the backend room. The components highlighted with red squares are controlled by computers.
  • Figure 3: Beam pattern at 129.36 GHz. The red and blue lines represent the radial profiles of the beam from northeast to southwest and from northwest to southeast in horizontal coordinates, respectively.
  • Figure 4: Aperture efficiency as a function of observing frequency. Red and black filled circles show the measured values with the B4R and other receivers, respectively. The blue line represents the case for the zero-frequency efficiency of 65% and the rms surface error of 100 $\mu$m. The other two lines (orange or gray) are for the rms surface error ($\varepsilon$) of 100 or 75 $\mu$m and the zero-frequency efficiency of 70%. Cyan fill shows the RF frequency range of the B4R.
  • Figure 5: Redshifted CO and [C i] spectra covering a frequency range of 2.5 GHz, taken toward one of the Planck-selected, strongly lensed HyLIRGs, PJ020941.3, at $z=2.55$. In each panel, $v=0$ km s$^{-1}$ corresponds to the line redshift obtained from our observations (see Table \ref{['tab:high-z-observation']}).
  • ...and 6 more figures