Donald G. York, co-founder of Sloan Digital Sky Survey and ‘visionary’ astronomer, 1944-2025

UChicago professor emeritus helped transform modern astronomy, mapped interstellar medium

DESIVAST: A Catalog of Low-Redshift Voids using Data from the DESI DR1 Bright Galaxy Survey

We present three separate void catalogs created using a volume-limited sample of the DESI Year 1 Bright Galaxy Survey. We use the algorithms VoidFinder and V2 to construct void catalogs out to a redshift of z=0.24. We obtain 1,461 interior voids with VoidFinder, 420 with V2 using REVOLVER pruning, and 295 with V2 using VIDE pruning. Comparing our catalog with an overlapping SDSS void catalog, we find generally consistent void properties but significant differences in the void volume overlap, which we attribute to differences in the galaxy selection and survey masks. These catalogs are suitable for studying the variation in galaxy properties with cosmic environment and for cosmological studies.

MPIA: Ein massereiches Schwarzes Loch erwacht - "live" - Raumfahrer.net

Astronomen sehen das Erwachen eines massereichen Schwarzen Lochs in Echtzeit. Eine Pressemitteilung des Max-Planck-Instituts für Astronomie (MPIA). Quelle: Max-Planck-Institut für Astronomie 19. Juni 2024. 19. Juni 2024 – Ende 2019 begann die zuvor unauffällige Galaxie SDSS1335+0728 plötzlich heller zu leuchten als je zuvor. Um den Ursachen auf den Grund zu gehen, haben Astronomen Daten von […]

What makes a cosmic filament? The dynamical origin and identity of filaments I. fundamentals in 2D

Cosmic filaments are the main transport channels of matter in the Megaparsec universe, and represent the most prominent structural feature in the matter and galaxy distribution. Here we describe and define the physical and dynamical nature of cosmic filaments. It is based on the realization that the complex spatial pattern and connectivity of the cosmic web are already visible in the primordial random Gaussian density field, in the spatial pattern of the primordial tidal and deformation eigenvalue field. The filaments and other structural features in the cosmic web emerging from this are multistream features and structural singularities in phase-space. The caustic skeleton formalism allows a fully analytical classification, identification, and treatment of the nonlinear cosmic web. The caustic conditions yield the mathematical specification of weblike structures in terms of the primordial deformation tensor eigenvalue and eigenvector fields, in which filaments are identified -- in 2D -- with the so-called cusp caustics. These are centered around points that are maximally stretched as a result of the tidal force field. The resulting mathematical conditions represent a complete characterization of filaments in terms of their formation history, dynamics, and orientation. We illustrate the workings of the formalism on the basis of a set of constrained $N$-body simulations of protofilament realizations. These realizations are analyzed in terms of spatial structure, density profiles, and multistream structure and compared to simpler density or potential field saddle point specifications. The presented formalism, and its 3D generalization, will facilitate the mining of the rich cosmological information contained in the observed weblike galaxy distribution, and be of key significance for the analysis of cosmological surveys such as SDSS, DESI, and Euclid.

MPIA: Forscher identifizieren zwei der frühesten Bausteine der Milchstraße – Raumfahrer.net

Hawai'i Supernova Flows: A Peculiar Velocity Survey Using Over a Thousand Supernovae in the Near-Infrared

We introduce the Hawai'i Supernova Flows project and present summary statistics of the first 1,217 astronomical transients observed, 668 of which are spectroscopically classified Type Ia Supernovae (SNe Ia). Our project is designed to obtain systematics-limited distances to SNe Ia while consuming minimal dedicated observational resources. To date, we have performed almost 5,000 near-infrared (NIR) observations of astronomical transients and have obtained spectra for over 200 host galaxies lacking published spectroscopic redshifts. In this survey paper we describe the methodology used to select targets, collect/reduce data, calculate distances, and perform quality cuts. We compare our methods to those used in similar studies, finding general agreement or mild improvement. Our summary statistics include various parametrizations of dispersion in the Hubble diagrams produced using fits to several commonly used SN Ia models. We find the lowest dispersions using the \texttt{SNooPy} package's EBV\_model2, with a root mean square (RMS) deviation of 0.165 mag and a normalized median absolute deviation (NMAD) of 0.123 mag. The full utility of the Hawai'i Supernova Flows data set far exceeds the analyses presented in this paper. Our photometry will provide a valuable test bed for models of SN Ia incorporating NIR data. Differential cosmological studies comparing optical samples and combined optical and NIR samples will have increased leverage for constraining chromatic effects like dust extinction. We invite the community to explore our data by making the light curves, fits, and host galaxy redshifts publicly accessible.

Motion of satellite galaxies suggests younger universe

In standard cosmological models, the formation of cosmological structures begins with the emergence of small structures, which subsequently undergo hierarchical merging, leading to the formation of larger systems. As the universe ages, massive galaxy groups and clusters, being the largest systems, tend to increase in mass and reach a more dynamically relaxed state.

Scientists Discovered an 'Ultra-Large Structure' in Space That Shouldn't Exist

The Big Ring, located 9 billion light years from Earth, is so huge that it challenges our current understanding of the universe.