Year: 2025
Type: preprint
Abstract: The census of stellar streams and dwarf galaxies in the Milky Way provides direct constraints on galaxy formation models and the nature of dark matter. The DESI Milky Way survey -- with a footprint of $14{,}000$ deg$^2$ and a depth of $r<19$ mag -- delivers the largest sample of distant metal-poor stars compared to previous optical fiber-fed spectroscopic surveys. This makes DESI an ideal survey to search for previously undetected streams and dwarf galaxies. We present a detailed characterization of the Cocytos stream, which was re-discovered using a clustering analysis with a catalog of giants in the DESI year 3 data, supplemented with Magellan/MagE spectroscopy. Our analysis reveals a relatively metal-rich ([Fe/H]$=-1.3$) and thick stream (width$=1.6^\circ$) at a heliocentric distance of $\approx 25$ kpc, with an internal velocity dispersion of $6$--$9$ km s$^{-1}$. The stream's metallicity, radial orbit, and proximity to the Virgo stellar overdensities suggest that it is most likely a disrupted globular cluster that came in with the Gaia-Enceladus merger. We also confirm its association with the Pyxis globular cluster. Our result showcases the ability of wide-field spectroscopic surveys to kinematically discover faint disrupted dwarfs and clusters, enabling constraints on the dark matter distribution in the Milky Way.
Source: arXiv (Cornell University)
Authors: Aganze, Christian, Chandra, Vedant, Wechsler, Risa H., Li, Ting S., Koposov, Sergey E., Silva, Leandro Beraldo, Carrillo, Andreia, Riley, Alexander H., Valluri, Monica, Gnedin, Oleg Y., Heiger, Mairead, Rockosi, Constance, Carlberg, Raymond, Byström, Amanda, Kizhuprakkat, Namitha, Lambert, Mika, Kim, Bokyoung, Medina, Gustavo E., Prieto, Carlos Allende, Aguilar, Jessica Nicole, Ahlen, Steven, Bianchi, Davide, Brooks, David, Claybaugh, Todd T., Cooper, Andrew P., de la Macorra, Axel, Dey, Arjun, Doel, Peter, Forero-Romero, Jaime E., Gaztañaga, Enrique, Gontcho, Satya A., Gutierrez, Gaston, Ishak, Mustapha, Kisner, Theodore, Kremin, Anthony, Lahav, Ofer, Landriau, Martin, Guillou, Laurent Le, Meisner, Aaron, Miquel, Ramon, Palanque-Delabrouille, Nathalie, Prada, Francisco, Pérez-Ràfols, Ignasi, Rossi, Graziano, Sanchez, Eusebio, Schubnell, Michael, Sprayberry, David, Tarlé, Gregory, Weaver, Benjamin A., Zou, Hu
Institutions: Kavli Institute for Particle Astrophysics and Cosmology, Center for Astrophysics Harvard & Smithsonian, University of Toronto, University of Cambridge, University of Arizona, Durham University, University of Michigan, University of California, Santa Cruz, University of Edinburgh, National Tsing Hua University, Universidad de La Laguna, Lawrence Berkeley National Laboratory, Boston University, Brera Astronomical Observatory, University College London, Universidad Nacional Autónoma de México, Universidad de Los Andes, Institut d'Estudis Espacials de Catalunya, University of Portsmouth, Fermi National Accelerator Laboratory, Laboratoire de Physique Nucléaire et de Hautes Énergies, Institució Catalana de Recerca i Estudis Avançats, Institute for High Energy Physics, Institut de Recherche sur les Lois Fondamentales de l'Univers, Universidad de Granada, Universitat Politècnica de Catalunya, Sejong University, Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas, Michigan Center for Translational Pathology, Syracuse University, Hiroshima Shudo University, High Energy Accelerator Research Organization
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W4414487635