Prof. Dimitra Rigopoulou

Abstract:

The extreme infrared (IR) luminosity of local luminous and ultra-luminous IR galaxies (U/LIRGs; 11 < log LIR /Lsun < 12 and log LIR /Lsun > 12, respectively) is mainly powered by star-formation processes triggered by mergers or interactions. While U/LIRGs are rare locally, at z > 1, they become more common, they dominate the star-formation rate (SFR) density, and a fraction of them are found to be normal disk galaxies. Therefore, there must be an evolution of the mechanism triggering these intense starbursts with redshift. To investigate this evolution, we present new optical SWIFT integral field spectroscopic H{\alpha}+[NII] observations of a sample of 9 intermediate-z (0.2 < z < 0.4) U/LIRG systems selected from Herschel 250{\mu}m observations. The main results are the following: (a) the ratios between the velocity dispersion and the rotation curve amplitude indicate that 10-25% (1-2 out of 8) might be compatible with being isolated disks while the remaining objects are interacting/merging systems; (b) the ratio between un-obscured and obscured SFR traced by H{\alpha} and LIR, respectively, is similar in both local and these intermediate-z U/LIRGs; and (c) the ratio between 250{\mu}m and the total IR luminosities of these intermediate-z U/LIRGs is higher than that of local U/LIRGs with the same LIR . This indicates a reduced dust temperature in these intermediate-z U/LIRGs. This, together with their already measured enhanced molecular gas content, suggests that the interstellar medium conditions are different in our sample of intermediate-z galaxies when compared to local U/LIRGs.

Abstract:

The Line Emission Terahertz Observatory (LETO) is a candidate European Space Agency (ESA) M8 mission designed to investigate the interstellar medium, star formation, and the evolution of galaxies through velocity-resolved spectroscopy of key far-infrared emission lines. To meet the demanding sensitivity, spectral-resolution, and mapping-speed requirements of the mission, LETO will employ multi-pixel heterodyne receiver arrays operating across four frequency bands between 0.45 and 5.5 THz.

This paper presents proposed concepts for the LETO Band 1 array receiver, which targets the frequency range below 1 THz using superconductor-insulator-superconductor (SIS) mixer technology. A wideband SIS mixer design covering the baseline 450–650 GHz frequency range is described. The design builds upon proven receiver technologies developed for astronomical instruments, thereby reducing technical risk while maintaining near quantum-limited sensitivity.

Two complementary array architectures are investigated. The first employs a conventional single-polarisation mixer configuration that can be reconfigured to support either single- or dual-polarisation observations. The second is based on a fourprobe dual-polarisation mixer concept that eliminates mechanically reconfigurable optical components while providing flexible observing modes. Several operational configurations are presented, demonstrating how the proposed architecture can balance sensitivity, mapping speed, and spacecraft resource constraints. These concepts form the basis for future development of the LETO Band 1 receiver should the mission progress to subsequent study phases.