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2024.10.30

Constraints on the tensor-to-scalar ratio r via a likelihood-based, optimal lensing reconstruction

<p>The cosmic microwave background (CMB) holds valuable information about the early Universe, including an imprint of its mass distribution that overshadows the faint signal from primordial gravitational waves, likely generated during inflation. Removing this imprint is crucial for future CMB observations to tightly constrain the tensor-to-scalar ratio r. This talk focuses on achieving the tightes...</p>

2024.10.23

The influence of GC evolution on the specific frequency in dwarf galaxies

<p>The presence of large fractions of metal-poor stars in dwarf galaxies still belonging to GCs raises questions about cluster mass loss and their formation mechanisms. These high ratios of metal-poor GCs relative to the number of low-metallicity field stars could imply that clusters in dwarfs have not lost enough mass, compared to more massive galaxies, or that the formation of field stars was su...</p>

2024.10.25

Galaxy Cluster Studies in the Era of High-resolution X-ray Spectroscopy

<p>Galaxy clusters, as massive, virialized halos within the cosmic web, serve as ideal laboratories for advancing our understanding of cosmology, plasma physics, and the nature of dark matter. High-resolution spectroscopy in soft X-rays will open a new window to map multiphase gas in galaxy clusters and probe physics of the intracluster medium, including but not limited to chemical enrichment hist...</p>

2024.10.18

Gravitational Lensing in the Kerr Spacetime: An Analytic Approach for Light and High-Frequency Gravitational Waves

<p>Current efforts of the Event Horizon Telescope aim at resolving the black hole shadow, mainly with the goal to probe the nature of the black hole and thus the underlying theory of gravity. Here, including other lensing features, in particular multiple images either of individual sources or in form of the so-called photon rings, will allow to place much tighter constrains on the spacetime parame...</p>

2024.10.22

Mapping the 3D Universe: From the Past to the Future, Bridging Theories and Observations

<p>This collaborative talk introduces the recent work in COSMO-3D group at EPFL’s Laboratory of Astrophysics (LASTRO). Jiaxi Yu (PhD student) will begin with a historical review of cosmology. The Universe started from a Big Bang, followed by inflation. The emission of the first light of the Universe, cosmic microwave background (CMB), happened in an opaque and dark era of the Universe afterwards....</p>

2024.10.11

Investigating the link between the growth of SMBHs and their host galaxies with X-ray surveys

<p>X-ray surveys have been an effective way to study growing supermassive black holes (SMBHs). Utilizing X-ray survey fields that have extensive multiwavelength data coverage, we can probe how SMBH growth links with the properties of their host galaxies, which will ultimately help to investigate the physical mechanisms behind the potential coevolution of SMBHs and their hosts. In my talk, I will p...</p>

2024.09.27

AGN SED Modeling: AGN luminosity in the simulated universe and implications on the era of reionization

<p>The study of the spectral energy distribution (SED) of active galactic nuclei (AGN) plays an important role in several aspects of the evolution of the galaxy. In this work, we model the black hole (BH) accretion flow for a wide range of BH mass and accretion rate. The accretion flow is divided into two regimes based on the Eddington-normalized accretion rate value - the ADAFs for low accretion ...</p>

2024.09.25

Lyman-alpha Intensity Mapping with optical imaging surveys: Future prospects

<p>Being the first spectral line of HI, Lyman-alpha permeates the cosmic web in emission. It has been largely used to study the close environment of galaxies and QSOs (Lyman-alpha blobs/nebulae); but being a resonant line it should scatter through the intergalactic medium. This should make Lyman-alpha an interesting candidate for Intensity Mapping (IM): the study of large-scale by integrating the ...</p>

2024.09.20

Unveiling the 70-year mystery of the nature of carbon-deficient red giants

<p>Weak G-band stars, or carbon-deficient red giants (CDGs), characterised by weak or absent G-band absorption of the CH molecule driven by low carbon abundances, have remained mysterious for decades. Here, we present a significant increase in the known CDG population identified through systematic spectroscopic surveys. This expanded sample confirms their rarity (&lt;1% of giants). Combining asterose...</p>

2024.09.13

Identifying the Galactic Substructures in 5D Space Using All-sky RR Lyrae Stars in Gaia DR3

<p>Motivated by the vast gap between photometric and spectroscopic data volumes, there is great potential in using 5D kinematic information to identify and study substructures of the Milky Way. We identify substructures in the Galactic halo using 46,575 RR Lyrae stars (RRLs) from Gaia DR3 with the photometric metallicities and distances newly estimated by Li et al. (2023). Assuming a Gaussian prio...</p>