
Iftikhar Ahmad (CAMK/AstroCeNT, Warsaw)
Dark matter's existence is a key topic in fundamental physics, with Weakly Interacting Massive Particles (WIMPs) being a leading candidate. Direct detection experiments, like those of the DarkSide collaboration, require highly pure target materials to achieve the necessary sensitivity. DarkSide-50 (DS-50) used argon due to its pulse shape discrimination (PSD), ease of purification, and scalability. During transport from Colorado to LNGS (Italy), cosmic rays interacted with the liquid argon, producing an impurity of Argon-37. A study was conducted to determine the activation of Argon-37 using DS-50 data, which was compared with production estimates during transport. The results were in agreement within 1 sigma, validating cosmic activation estimates for Argon-39 and future detectors. The DarkSide-20k (DS-20k) experiment, under construction at INFN-LNGS, will use a dual-phase liquid argon time projection chamber (LAr-TPC) to achieve high sensitivity. To suppress background noise, DS-20k will incorporate cryogenic silicon photomultipliers (SiPMs) and a sophisticated neutron veto. Key to this is the development and testing of Veto PhotoDetection Units (vPDUs), which must detect individual photons with high precision. At Astrocent, two vPDUs were tested, meeting DS-20k’s specifications with results including breakdown voltages (~54 V), dark count rates (<0.1 Hz/mm²), and signal-to-noise ratios (<8).
Lorenzon Giuliano (National Center for Nuclear Research, Warsaw)
The idea of a strict relationship between the evolution of the cold gas and dust components in the interstellar medium (ISM) of quiescent galaxies (QGs) has recently been challenged thanks to the combined use of the Near/Mid-infrared JWST and the sub-mm ALMA telescopes. Such galaxies have little to no star formation and are typically considered poor in ISM, but new evidence is building up revealing both gas-rich and dust-rich QGs, especially at z>1. Such a discovery is changing the way we interpret QGs, raising new questions about the way we select them and on the physics regulating their formation. We use the state-of-the-art suit of cosmological simulations SIMBA to tackle the physical processes generating dust-rich QGs up to z~2 by comparing the effect of internal and environmental quenching mechanisms on the evolution of the ISM content. While dust is generally associated with mechanisms of star formation and has a generally short lifespan, we find in SIMBA indications that grains can survive for much longer due to prolonged accretion of metals from the ISM. This mechanism naturally competes with grain destruction, which is mainly driven by the energy injection of the active galactic nucleus (AGN), suggesting that the interplay between the AGN and the dust growth timescales may be the reason for the observed variety in the dust content of QGs. The results from this theoretical analysis are soon to be directly tested thanks to ad-hoc observations with the ALMA sub-mm telescope we managed to obtain during the Cycle 11 observation campaign.
CAMK Annual Conference
Ricardo Salinas (CAMK/Araucaria, Warsaw)
While adaptive optics is the most widespread method to compensate for atmospheric turbulence, these methods are particularly difficult to implement in the optical regime given the technical challenges imposed by the short coherence times. An alternative to reach the diffraction limit of an optical telescope is provided by speckle interferometry, where, instead of real-time corrections, observations are obtained in timescales similar to the coherence time (a few ms), and the diffraction limit is recovered via a post-hoc reduction in Fourier space. In 2019, the Gemini telescopes commissioned two speckle interferometers, Zorro and 'Alopeke, owned by NASA Ames, which have remained as "permanent visiting" instruments since then. In this talk I will present the characteristics of these instruments, to then present a number of science cases where these instruments are particularly suited, mostly leaning to my own research on RR Lyrae in binary systems, and blue stragglers in hierarchical triplets.
Winter break
Winter break
Rolf Chini (CAMK, Warsaw, Araucaria Project)
The project deals with the rotational velocity (v sin i) of 238 southern O stars. The sample contains 130 spectroscopic single stars (C), 36 single-lined binaries (SB1), and 72 SB2 systems (including eight triples). The overall v sin i statistics peaks at slow rotators (40–100 km/s) with a tail towards medium (100–200 km/s) and fast rotators (200–400 km/s). Binaries, on average, show increased rotation, which differs for close (Porb < 10 d) and wide binaries (10 d < Porb < 3700 d), and for primaries and secondaries. The spin-up of close binaries is well explained by the superposition of spin-orbit synchronization and mass transfer via Roche-lobe overflow. The increased rotation of wide binaries, however, can be caused by various spin-up mechanisms. Timescale arguments lead us to favor a scenario where wide O binaries are spun-up by a combination of cloud or disk fragmentation, which lays the basis of triple and multiple stars, and the subsequent merging or swallowing of low-mass by higher-mass stars or proto-stars.