Segue 2 Recently Collided with the Cetus-Palca Stream: New Opportunities to Constrain Dark Matter in an Ultra-Faint Dwarf

Abstract

Stellar streams in the Milky Way are promising detectors of low-mass dark matter (DM) subhalos predicted by $\Lambda$CDM. Passing subhalos induce perturbations in streams that indicate the presence of the subhalos. Understanding how known DM-dominated satellites impact streams is a crucial step towards using stream perturbations to constrain the properties of dark perturbers. Here, we cross-match a \textit{Gaia} EDR3 and SEGUE member catalog of the Cetus-Palca stream (CPS) with H3 for additional radial velocity measurements and fit the orbit of the CPS using this 6-D data. We demonstrate for the first time that the ultra-faint dwarf Segue 2 had a recent (77$\pm$5 Myr ago) close flyby (within the stream's 2$\sigma$ width) with the CPS. This interaction enables constraints on Segue 2's mass and density profile at larger radii ($\mathcal{O}(1)$ kpc) than are probed by its stars ($\mathcal{O}(10)$ pc). While Segue 2 is not expected to strongly affect the portion of the stream covered by our 6-D data, we predict that if Segue 2's mass within $\sim 6$ kpc is $5\times 10^9{M}_{\odot }$, the CPS's velocity dispersion will be $\sim 40$ km s${}^{-1}$ larger at ${\varphi }_1>20^{\circ }$ than at ${\varphi }_1<0^{\circ }$. If no such heating is detected, Segue 2's mass cannot exceed $10^9{M}_{\odot }$ within $\sim 6$ kpc. The proper motion distribution of the CPS near the impact site is mildly sensitive to the shape of Segue 2's density profile. This study presents a critical test for frameworks designed to constrain properties of dark subhalos from stream perturbations.

33 pages, 14 figures, 6 tables. Updated for consistency with published version

References in corpus (51)

• Array Programming with NumPy
• The Gaia mission
• The Astropy Project: Sustaining and Growing a Community-oriented Open-source Project and the Latest Major Release (v5.0) of the Core Package
• Cosmic Structure as the Quantum Interference of a Coherent Dark Wave
• A distance to the Large Magellanic Cloud that is precise to one per cent
• Stellar Feedback in Dwarf Galaxy Formation
• 4MOST: Project overview and information for the First Call for Proposals
• Axion dark matter, solitons, and the cusp-core problem
• The M31 Velocity Vector. II. Radial Orbit Towards the Milky Way and Implied Local Group Mass
• Dwarf galaxies in CDM and SIDM with baryons: observational probes of the nature of dark matter
• The wide-field, multiplexed, spectroscopic facility WEAVE: Survey design, overview, and simulated implementation
• Overview of the DESI Milky Way Survey
• Discovery of a New, Polar-Orbiting Debris Stream in the Milky Way Stellar Halo
• On the structure of tidal tails
• Orbits of Massive Satellite Galaxies: I. A Close Look at the Large Magellanic Cloud and a New Orbital History for M33
• Tracing Sagittarius Structure with SDSS and SEGUE Imaging and Spectroscopy
• Proper Motions, Orbits, and Tidal Influences of Milky Way Dwarf Spheroidal Galaxies
• Measuring the Mass of the Large Magellanic Cloud with Stellar Streams Observed by $S^5$
• Forensics of Subhalo-Stream Encounters: The Three Phases of Gap Growth
• Detection of the Milky Way reflex motion due to the Large Magellanic Cloud infall
• The Preferential Tidal Stripping of Dark Matter versus Stars in Galaxies
• The mechanics of tidal streams
• $S^5$: Probing the Milky Way and Magellanic Clouds potentials with the 6-D map of the Orphan-Chenab stream
• galstreams: A Library of Milky Way Stellar Stream Footprints and Tracks
• Revised and new proper motions for confirmed and candidate Milky Way dwarf galaxies
• Kinematics of Antlia 2 and Crater 2 from The Southern Stellar Stream Spectroscopic Survey (S5)
• $S^5$: The Orbital and Chemical Properties of One Dozen Stellar Streams
• The PAndAS Field of Streams: stellar structures in the Milky Way halo toward Andromeda and Triangulum
• The core-cusp problem: a matter of perspective
• Orbital Clustering Identifies the Origins of Galactic Stellar Streams
• Reflex motion in the Milky Way stellar halo resulting from the Large Magellanic Cloud infall
• Ultrafaint Dwarf Galaxies - the lowest mass relics from before reionization
• The effect of the LMC on the Milky Way system
• The effect of the deforming dark matter haloes of the Milky Way and the Large Magellanic Cloud on the Orphan-Chenab stream
• Quantifying the Stellar Halo's Response to the LMC's Infall with Spherical Harmonics
• The role of faint population III supernovae in forming CEMP stars in ultra-faint dwarf galaxies
• The diversity of rotation curves of simulated galaxies with cusps and cores
• The Complexity of the Cetus Stream Unveiled from the Fusion of STREAMFINDER and StarGO
• Degeneracies Between Self-interacting Dark Matter and Supernova Feedback as cusp-core transformation mechanisms
• Simulating tidal streams in a high resolution dark matter halo
• The many reasons that the rotation curves of low-mass galaxies can fail as tracers of their matter distributions
• Highly r-process enhanced stars in ultra-faint dwarf galaxies
• The Cetus-Palca stream: A disrupted small dwarf galaxy. A prequel to the science possible with WEAVE with precise spectro-photometric distances
• Quantifying tidal stream disruption in a simulated Milky Way
• HSTPROMO Internal Proper Motion Kinematics of Dwarf Spheroidal Galaxies: I. Velocity Anisotropy and Dark Matter Cusp Slope of Draco
• Real and counterfeit cores: how feedback expands halos and disrupts tracers of inner gravitational potential in dwarf galaxies
• SN-driven mechanism of cusp-core transformation: an appraisal
• Probability of forming gaps in the GD-1 stream by close encounters of globular clusters
• The LMC impact on the kinematics of the Milky Way satellites: clues from the running solar apex
• Characterization and dynamics of the peculiar stream Jhelum, A tentative role for the Sagittarius dwarf galaxy
• Probing the assembly of dwarf galaxies through cosmic time with damped Lyman-$\alpha$ absorption spectroscopy

Cited by in corpus (1)

• Inferring the density and membership of stellar streams with flexible models: The GD-1 stream in Gaia Data Release 3