Conveners
Halo finding & statistics
- Susmita Adhikari (Indian Institute of Science Education and Research, Pune)
Halo finding & statistics
- Susmita Adhikari (Indian Institute of Science Education and Research, Pune)
Halo finding & statistics
- Jiaxin Han (Shanghai Jiao Tong University)
Halo finding & statistics
- Jiaxin Han (Shanghai Jiao Tong University)
Whether we try to observe the splashback, edge, or depletion radius (as well as sub-definitions thereof), the vast majority of experimental inferences are based on some type of spherically averaged, projected density profile. Commonly, the radius where the density slope is steepest is taken as the halo boundary, but this definition is particularly sensitive to the observational tracer and to...
Conventionally, halos are considered subhalos if their center lies within the radius of their hosts. However, definitions of the halo boundary vary throughout the literature, such that some halos are not consistently labeled as standalone structures or subhalos. What structures are considered discrete impacts quantities critical to our halo models, such as the halo mass or correlation...
I will discuss some benefits of using caustics (boundaries of stream/shell crossing) to delineate cosmic web components. Our original ORIGAMI (Order-ReversIng Gravity, Apprehended Mangling Indices) algorithm explicitly looks for particle crossings, but much of the tagging works simply by looking for out-of-order particles along orthogonal axes, and then filling in holes. It is also important...
Satellite galaxies are observable tracers of the dark matter subhalos, and are subject to the same gravitational influence of the main halo. Hence, the radial distribution of the satellite galaxies can probe the main halo’s density profile and the associated physical boundary. In this talk, I will discuss the observed satellite radial profiles of Milky Way-mass systems from the SAGA Survey,...
We show that the merger tree of dark matter halos is approximately self-similar by investigating the universality of the subhalo peak mass function (PMF) describing the mass distribution of progenitor halos. Using a set of cosmological simulations and identifying subhalos of different merger levels with HBT+, we verify that the level-1 subhalo PMF is close to universal across halo mass,...
Based on [arxiv:2412.16072] Recent observations from the James Webb Space Telescope revealed a surprisingly large number of galaxies formed at high redshift. Along with strong lensing studies and nearby galaxy observations, these could challenge the standard Lambda Cold Dark Matter cosmology with a power-law primordial power spectrum. In this study, we conduct high-resolution cosmological...
Clusters present an excellent laboratory for studying influences on galaxy evolution due to their extreme environments that alter the evolutionary pathways of galaxies. However, the cluster does not have a clear boundary, which has motivated a number of studies proposing and identifying boundary definitions that capture various aspects of a halo’s properties. For example, the standard...
Dark matter haloes are the end product of cosmological structure formation. Produced through the gravitational collapse of initial density perturbations, these objects are considered to be self gravitating and virialised. Nonetheless, standard methods, used to both detect and analyse these structures in simulations, produce objects that are not virialised requiring the inclusion of an...
Subhalo abundance matching (SHAM) is a widely used empirical model for linking galaxies to (sub)halos and predicting galaxy clustering. It assigns galaxies to subhalos by matching the cumulative number density of galaxies above a luminosity (or stellar mass) threshold to the corresponding number density of subhalos above a mass threshold. Scatters in the stellar-to-halo mass relation can also...
The splashback radius was proposed as a physically motivated boundary of clusters as it sets the limit between the infalling and the orbitally dominated regions. However, galaxy clusters are complex objects connected to filaments of the cosmic web from which they accrete matter that disturbs them and modifies their morphology. In this context, estimating the splashback radius and the cluster...
The Local Group (LG), as a gravitationally bound system of the Milky Way and Andromeda, as well as their satellites, is a cornerstone of near-field cosmology. However, its utility as a cosmological probe requires understanding how it is related to the cosmic web. Using the ABACUSSUMMIT simulation, we identify LG analogues and quantify their environmental dependence. We find that the coupling...
The Blooming Tree (BT) algorithm is an optimized hierarchical clustering method designed to identify clusters, groups, and substructures. We evaluate the performance of this method using a compiled wide-field ($10° \times 10°$) spectroscopic dataset centered on a supercluster of galaxies, A2029. This algorithm effectively identifies all X-ray luminous clusters, many groups, and even filaments...
Dark matter halos are complex evolving objects. In this talk I will discuss a study of the internal structures of dark matter halos using clustering algorithms in higher dimensional phase space, to see if they can pick up dynamical structures that are agnostic of pre-defined boundaries in the dark matter halos. We use the UMAP algorithm to visualize these distinct structures and find that the...
