As a result of the implementation of the Atacama Large Millimeter/submillimeter Array (ALMA), exciting and cutting edge research is being undertaken in millimeter and submillimeter astronomy. ALMA has unprecedented performance and capabilities, e.g., a high angular resolution (down to 10 milli-arcsecond) and high-sensitivity imaging. On the other hand, the millimeter and submillimeter universe unveiled by ALMA is quite limited as regards sky and spectroscopic coverage, i.e., in terms of the three-dimensional (3D) volume of the universe.
In 2008, we began discussions on a future large single-dish telescope. Our initial motivation was the planning of a next-generation millimeter and submillimeter telescope that could, to the greatest possible extent, inherit both the large collecting area of the Nobeyama Radio Observatory (NRO) 45-m telescope (Ukita et al. 1994) and the submillimeter capabilities of the Atacama Submillimeter Telescope Experiment (ASTE) 10-m telescope (Ezawa et al. 2008).
Through discussions with researchers in the Europe and US, as well as in East Asia, we further developed this plan, primarily by considering future necessary scientific developments and potential new discoveries that could be complemented by new single-dish telescopes. We finally resolved to construct a large single-dish telescope, i.e., a new 50-m class telescope, to be called the Large Submillimeter Telescope (LST).
The LST will facilitate groundbreaking exploration of an extremely large 3D volume of the universe and, also, completely new advancements in time-domain science for millimeter and submillimeter astronomy. One of the major scientific goals is unveiling the large-scale structure of the high-z universe in 3D, along with elucidation of cosmic star formation history. This can be accomplished via wide-area spectroscopic surveys of dusty starbursts based on CO and [C II] 158 μm lines (and, presumably, [O III] 88 μm lines, as demonstrated by the recent ALMA detection of a z = 7.2 galaxy; Inoue et al. 2016), as well as multi-band continuum surveys. The LST is very complementary to ALMA and can establish a census of various astronomical objects of our interest through wide-field surveys. The LST can also identify intriguing sources for further investigation by ALMA. By exploiting the synergy with ALMA and other survey-oriented existing and near-future missions in the optical to far-infrared ranges, including HSC/PFS on Subaru, TAO, LSST, Euclid, WFIRST, and SPICA, the LST can contribute to a wide range of research in astronomy and astrophysics.
National Astronomical Observatory of Japan
Osaka Prefecture University
The University of Tokyo