ATT12: The Antarctic 12 m terahertz telescope for studies of dusty galaxies. I. Instrument sensitivity and science forecasts

We present a feasibility study of the Antarctic 12 m Terahertz Telescope (ATT12), a next-generation facility to be constructed at New Dome Fuji in Antarctica, designed to open up the far-infrared and terahertz windows for extragalactic astronomy. While ATT12 will enable a wide range of Galactic and extragalactic science, this paper focuses on its potential for studies of dusty star-forming galaxies (DSFGs) across cosmic time. Using realistic atmospheric transmission models and the planned instrumental specifications of heterodyne spectrometers and wide-field multi-color continuum cameras, we assess the expected sensitivity and scientific capabilities of ATT12. We show that spectroscopic observations will enable detections of [C ii] 158\, μm from galaxies with log (LIR/L_ ) 12 out to z~ 7, while [O iii] 88\, μm will remain observable for HyLIRG-class systems (log LIR/L_ 13) up to z~ 10. Line ratios including [O iii] 52/88\, μm, [N ii] 122/205\, μm, and [O iii]$/$[N iii] will provide unique diagnostics of electron density and O/N abundance at z~ 4–8. Wide-field continuum surveys with the continuum cameras (KIDS-1/2; 300–850 GHz) will reach confusion-limited depths of ~1–2 mJy over ~10000 deg², detecting of order 10⁶–10⁷ DSFGs with LIR 10¹²\, L at z 5 and 10³–10⁴ HyLIRGs with LIR 10¹³\, L up to z~ 7 or even higher. Higher-frequency MKID cameras (KIDS-3/4; $>$850 GHz) are designed for targeted follow-up observations and to extend coverage toward the THz regime. Taken together, ATT12 will provide the first statistically representative samples of dusty galaxies across cosmic time and, through synergy with ALMA, JWST, and the proposed FIR Probe PRIMA, will establish a multi-wavelength framework in which ATT12 discovers large samples through wide-area surveys, ALMA provides high-resolution follow-up of gas and ISM structure, JWST probes stellar populations and metallicity in the rest-frame optical/near-infrared, and PRIMA delivers ultra-sensitive far-infrared spectroscopy from space.