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.
Radek Poleski (Astronomical Observatory, Warsaw University)
I will present recent results obtained by the OGLE survey in two aspects. First, I will focus on black holes and present constraints on their primordial distribution as well as the detection of a few solar mass black hole using the microlensing technique. The detection of more black holes using microlensing will soon be possible thanks to the advances in optical interferometry, which I will also discuss. Second, I will present studies of the structure of the Milky Way. These studies are based on the variable stars (classical Cepheids and Miras) discovered mostly by the OGLE survey.
Gerardo Urrutia Sanchez (Institute for Theoretical Physics, PAN, Warsaw)
Gamma-ray bursts (GRBs) are the most luminous explosions in the universe ( $L \sim 10^{50} - 10^{52}$~erg s$^{-1}$ ) originating from mergers of neutron stars or from the collapse of stripped-envelope massive stars. The first seconds of emission are dominated by gamma emission and high variability in its light curves, in addition, a long-lasting afterglow emission across a wide range of frequencies could be observed after the burst time. In this talk, I will present numerical simulations of collapsar GRBs, showing the propagation of a relativistic jet through the progenitor star and after its breakout. Since electromagnetic signals (the light curves) cannot fully reveal the physical properties of the jet within the stellar envelope, I will discuss GRBs as candidates for gravitational wave (GW) emission arising from the propagation of such ultra-relativistic jets. Our results indicate that key parameters of jet propagation can be inferred from this GW signal and detected by future instruments such as LISA, BBO, DECIGO, and ALIA. These results suggest that future GW detections associated with GRB jets could provide a complete picture of jet evolution together with electromagnetic counterparts.
Mariana Jaber (Center for Theoretical Physics, PAN, Warsaw)
The standard ΛCDM model, despite its remarkable success, remains incomplete, especially regarding the nature of cosmic acceleration. During the first part of the talk, I will discuss my work testing alternatives to the Cosmological Constant, including quintessence models and modifications to General Relativity using galaxy redshift surveys. The resulting catalogues contain a wealth of untapped information, particularly regarding galaxy motions and pairwise velocities. A key challenge in utilising this wealth of new data is understanding galaxy bias, which is essential for making accurate cosmological inferences. This motivates the second part of my talk, where I discuss my research on developing analytical models of galaxy pairwise dynamics based on the kinetic BBGKY theory describing the evolution of a system of particles interacting via gravity. This approach could lead to new methods to constrain cosmological parameters such as matter density, the Hubble parameter, and the growth rate. Combining these analytical models with the information about the large-scale environment and observational data, we could refine constraints on ΛCDM and extend our galaxy bias modelling to non-linear scales.
Deka Kishan (National Center for Nuclear Research, Warsaw)
Weak gravitational lensing remaps the primordial anisotropies in the Cosmic Microwave Background (CMB), introducing lensing induced B-mode polarisation. Estimating the lensing potential field and delensing the observed CMB maps are crucial for improving constrains on cosmological parameters. However, one of the main obstacles is the presence of polarised foreground emissions from our own Galaxy. In this talk, I will discuss about CMB weak lensing reconstruction methods and the impact of galactic foreground emissions in delensing. I will present my results on galactic foreground bias on the tensor-to-scalar ratio in the context of upcoming CMB Stage-4 survey.
Alessandro Trani (Niels Bohr Institute - University of Copenhagen)
Despite eight years since the initial detection of gravitational waves, the astrophysical origin of these phenomena remains elusive. Recent years have witnessed a growing interest in a novel gravitational wave formation pathway: the active galactic nuclei (AGN) channel. I will overview the main astrophysical mechanisms of gravitational wave sources formation and then describe the key features of the AGN channel, discussing our ongoing efforts in modeling compact objects within accretion disks in AGNs.
Francesco Flammini Dotti (Heidelberg University)
The dynamical evolution of massless objects in star clusters aims to explore their dynamics during the dynamical evolution of such structures, which is not easy observable in star clusters, and still not possible in dense star clusters such as globular clusters. In a star cluster, the main phenomenon we are going to focus on are the mass segregation and core collapse. I will first introduce previous works that looked into the motion of these objects, and then I will numerically explore the dynamical evolution of such objects, varying the number density of the hosting star cluster. As a final point, I will try to confute if the relative large abundance of free-floating planets in our galaxy is due to their ejected ree-floating planets. I will use NBODY6++GPU-ML (a N-body code which performs simulations with a large number of particles and massless particles, i.e., star clusters with free-floating planets) The results pinpoint how the massless particles are not particularly affected by mass segregation, but only by the central gravitational evolution of the core of the star cluster, suggesting that those particles, in relatively dense star clusters, are ejected only at much larger timescales.
Azam Zabihi (CAMK/AstroCeNt, Warsaw)
DarkSide-20k: DS-20k is the next iteration in a series of direct detection Dark Matter (DM) experiments utilizing Liquid Argon (LAr) as the detection medium. Building on the success of its predecessor, DarkSide-50 (DS-50), which deployed ∼50 kg of Underground Argon (UAr), DS-20k aims to scale up to 100 tons of UAr, presenting significant technological challenges. The DS-Mockup serves as an intermediate detector designed to demonstrate key components and feasibility for DS-20k. This talk will outline the goals and tests of the DS-Mockup, focusing on the feasibility of assembling a scaled-down version of DS-20k to validate the mechanical and electrical dimensions of the detector, essential for future advancements. Development of the Most Sensitive Dark Matter Detector with Liquid Argon: The Dark Matter Detector with Liquid Argon is being developed to enhance sensitivity to low-mass WIMPs and electron-scattering DM. The scientific goal of the project is to reduce background noise and improve detection sensitivity in three critical areas: minimizing impurities in LAr, reducing radioactivity in photodetectors, and improving understanding of LAr response. This approach could potentially extend the search for dark matter to lower mass regions, enhancing the scientific reach of next-generation detectors like DS-20k. 3Dπ: three-dimensional positron imaging: 3Dπ is a novel total-body PET scanner using liquid argon (LAr) doped with xenon (Xe) as a scintillator material. By leveraging emerging technology from dark matter detection, 3Dπ integrates time-of-flight (TOF) technology and ultra-fast readout electronics for ultra-low dose imaging. Using Monte Carlo simulations, we evaluate 3Dπ's performance in terms of noise equivalent count rate (NECR), spatial resolution, and TOF resolution, showing significant improvements over traditional PET systems. The design promises reduced scan times and radiation exposure, offering a breakthrough in PET imaging technology with applications in clinical diagnostics.
Alexander Tchekhovskoy (Northwestern University)
Abbas Askar (CAMK, Warsaw)
Luke Dones (Southwest Research Institute, Boulder, Colorado)
