Fonctionne avec Indico
v3.2.8
10h: Damien Cherouvrier
Detection and physics of distant galaxy clusters via the Sunyaev-Zel’dovich effect
Clusters of galaxies, formed at the latest stages of structure formation, constitute unique cosmological probes. With the advent of large SZ surveys like those from the Planck satellite, the ACT and SPT telescopes, we now have access to a large catalog of galaxy clusters detected at millimeter wavelengths via the thermal Sunyaev-Zeldovich (tSZ) effect. However, they do not offer the high angular resolution needed to detect the lowest mass, high redshift clusters. This could be achieved by using millimeter cameras operated in large millimeter telescopes like for example the NIKA2 camera installed in the IRAM 30–m telescope in Spain. In this presentation, I will first outline the methodology we have used to blindly detect galaxy clusters with the NIKA2 camera, followed by a discussion on the properties of our cluster candidates. Then, I will introduce the Grenoble-Tsukuba collaboration and the ongoing work on the Tsukuba-Grenoble 100 GHz KIDs array camera. After installing the camera at the Nobeyama 45m telescope in Japan, we plan complementary observations of the cluster candidates previously mentioned.
10h30: Marina Masson
Search for Orphan Gamma-Ray Burst Afterglows with the Vera C. Rubin Observatory
Gamma-Ray Bursts (GRBs) are among the most energetic phenomena in the Universe. They are brief and bright flashes of gamma-rays, lasting from less than a second to tens of seconds, and are believed to be produced by the collapse of massive stars or by the merger of two neutron stars. The very intense gamma-ray radiation, called prompt emission, is followed by a slowly fading emission, called afterglow. The afterglow can be observed from a larger angle, in a wide range of the electromagnetic spectrum and during more time than the prompt emission. Viewed off-axis, this emission has a negligible gamma-ray flux but can still be observed in the optical and radio bands, as a so-called "GRB orphan afterglow". Orphan afterglows are good candidates to learn more about GRB physics and progenitors, or for the development of multi-messenger astrophysics, and the Rubin Observatory Legacy Survey of Space and Time (LSST) is expected to be a prime tool to enhance the detection of these faint sources. The goal of my PhD is to identify the best orphan afterglows candidates among the Rubin LSST data. In this context, we developed a machine learning filter able to discriminate orphan-like events among all the variable objects. In this seminar, I will present the performance of our filter as tested on the ELAsTiCC data set (a simulated alert stream of the Rubin LSST data) and our own Rubin observation simulations.