First resolved stellar halo kinematics of a MW-mass galaxy outside the Local Group: A flat counter-rotating halo in NGC 4945
arXiv:2406.17533 · doi:10.1051/0004-6361/202450626
Abstract
Stellar halos of galaxies, primarily formed through the accretion of smaller objects, are important to understand the hierarchical mass assembly of galaxies. However, the inner regions of stellar halos in disk galaxies are predicted to have an in-situ component that is expected to be prominent along the major axis. Kinematic information is crucial to disentangle the contribution of the in-situ component from the accreted stellar halos. The low surface brightness of stellar halos makes it inaccessible with traditional integrated light spectroscopy. In this work, using a novel technique, we study the kinematics of the stellar halo of the edge-on galaxy NGC 4945. We couple new deep Multi Unit Spectroscopic Explorer spectroscopic observations with existing Hubble Space Telescope imaging data to spectroscopically measure the line-of-sight (LOS) heliocentric velocity and velocity dispersion in two fields at a galactocentric distance of 12.2 kpc (outer disk field) and 34.6 kpc (stellar halo field) along NGC 4945 major axis, by stacking individual spectra of red giant branch and asymptotic giant branch stars. We obtain a LOS velocity and dispersion of 673+/-11 km/s and 73+/-14 km/s, respectively, for the outer disk field. This is consistent with the mean HI velocity of the disk at that distance. For the halo field we obtain a LOS velocity and dispersion of 519+/-12 km/s and 42+/-22 km/s. The halo fields' velocity measurement is within ~40 km/s from the systemic LOS velocity of NGC 4945, which is 563 km/s, suggesting that its stellar halo at 34.6 kpc along the major axis is counter-rotating and is of likely accretion origin. This provides the first ever kinematic measurement of the stellar halo of a Milky Way-mass galaxy outside the Local Group from its resolved stellar population, and establishes a powerful technique for measuring the velocity field of the stellar halos of nearby galaxies.
arXiv commentAccepted to A&A. 23 pages, 12 figures, 2 appendices
References in corpus (84)
- Gaia Data Release 2. Summary of the contents and survey properties
- The Gaia mission
- The EAGLE project: Simulating the evolution and assembly of galaxies and their environments
- Detailed Structural Decomposition of Galaxy Images
- E pur si muove: Galiliean-invariant cosmological hydrodynamical simulations on a moving mesh
- Parametric Recovery of Line-of-Sight Velocity Distributions from Absorption-Line Spectra of Galaxies via Penalized Likelihood
- The Galaxy in Context: Structural, Kinematic and Integrated Properties
- Improving the full spectrum fitting method: accurate convolution with Gauss-Hermite functions
- The merger that led to the formation of the Milky Way's inner stellar halo and thick disk
- Tracing Galaxy Formation with Stellar Halos I: Methods
- Co-formation of the Galactic disc and the stellar halo
- First Results from the TNG50 Simulation: Galactic outflows driven by supernovae and black hole feedback
- First Results from the TNG50 Simulation: The evolution of stellar and gaseous disks across cosmic time
- HyperLEDA. III. The catalogue of extragalactic distances
- Galactic stellar haloes in the CDM model
- The 1000 Brightest HIPASS Galaxies: HI Properties
- The accretion origin of the Milky Way's stellar halo
- Tracing Galaxy Formation with Stellar Halos II: Relating Substructure in Phase- and Abundance-Space to Accretion Histories
- Stellar Tidal Streams in Spiral Galaxies of the Local Volume: A Pilot Survey with Modest Aperture Telescopes
- The Data Processing Pipeline for the MUSE Instrument
- The MUSE Hubble Ultra Deep Field Survey: I. Survey description, data reduction and source detection
- The Dual Origin of Stellar Halos
- ZAP -- Enhanced PCA Sky Subtraction for Integral Field Spectroscopy
- The Milky Way stellar halo out to 40 kpc : Squashed, broken but smooth
- Stars beyond Galaxies: The Origin of Extended Luminous Halos around Galaxies
- Full spectrum fitting with photometry in pPXF: stellar population versus dynamical masses, non-parametric star formation history and metallicity for 3200 LEGA-C galaxies at redshift z~0.8
- The large-scale structure of the halo of the Andromeda Galaxy Part I: global stellar density, morphology and metallicity properties
- On the accretion origin of a vast extended stellar disk around the Andromeda galaxy
- The extended halo of Centaurus A: uncovering satellites, streams, and substructures
- Gaia Early Data Release 3: Summary of the contents and survey properties
- The Auriga Stellar Haloes: Connecting stellar population properties with accretion and merging history
- The large-scale structure of the halo of the Andromeda galaxy II. Hierarchical structure in the Pan-Andromeda Archaeological Survey
- Building Late-Type Spiral Galaxies by In-Situ and Ex-Situ Star Formation
- Beyond 31 mag/arcsec^2: the low surface brightness frontier with the largest optical telescopes
- Resolving stellar populations with crowded field 3D spectroscopy
- Dwarfs Gobbling Dwarfs: A Stellar Tidal Stream Around NGC 4449 and Hierarchical Galaxy Formation on Small Scales
- Mapping the Stellar Halo with the H3 Spectroscopic Survey
- Formation of In Situ Stellar Haloes in Milky Way-Mass Galaxies
- The total stellar halo mass of the Milky Way
- A 2-3 billion year old major merger paradigm for the Andromeda galaxy and its outskirts
- The origin of galactic metal-rich stellar halo components with highly eccentric orbits
- The Dragonfly Nearby Galaxies Survey. I. Substantial variation in the diffuse stellar halos around spiral galaxies
- The Andromeda galaxy's most important merger about 2 billion years ago as M32's likely progenitor
- Diverse Stellar Haloes in Nearby Milky Way-Mass Disc Galaxies
- First results from the Dragonfly Telephoto Array: the apparent lack of a stellar halo in the massive spiral galaxy M101
- The GHOSTS survey. II. The diversity of Halo Color and Metallicity Profiles of Massive Disk Galaxies
- Global Properties of M31's Stellar Halo from the SPLASH Survey. I. Surface Brightness Profile
- Weighing the stellar constituents of the Galactic halo with APOGEE red giant stars
- The Local Volume HI Survey (LVHIS)
- The Eating Habits of Milky Way Mass Halos: Destroyed Dwarf Satellites and the Metallicity Distribution of Accreted Stars
- The masses and metallicities of stellar haloes reflect galactic merger histories
- Global Properties of M31's Stellar Halo from the SPLASH Survey: II. Metallicity Profile
- The slight spin of the old stellar halo
- Stellar Kinematics in the Complicated Inner Spheroid of M31: Discovery of Substructure Along the Southeastern Minor Axis and its Relationship to the Giant Southern Stream
- Galaxies grow their bulges and black holes in diverse ways
- A Hyper Suprime-Cam View of the Interacting Galaxies of the M81 Group
- Lessons from the Auriga discs: The hunt for the Milky Way's ex-situ disc is not yet over
- The stellar halos of ETGs in the IllustrisTNG simulations: the photometric and kinematic diversity of galaxies at large radii
- The massive relic galaxy NGC 1277 is dark matter deficient. From dynamical models of integral-field stellar kinematics out to five effective radii
- DESI Observations of the Andromeda Galaxy: Revealing the Immigration History of our Nearest Neighbor
- On the stellar halo metallicity profile of Milky Way-like galaxies in the Auriga simulations
- Testing galaxy formation models with the GHOSTS survey: The color profile of M81's stellar halo
- Characterizing the formation history of Milky Way-like stellar haloes with model emulators
- Detection of a distinct metal-poor stellar halo in the early-type galaxy NGC 3115
- Integral-field kinematics and stellar populations of early-type galaxies out to three half-light radii
- The Saga of M81: Global View of a Massive Stellar Halo in Formation
- Global Properties of M31's Stellar Halo from the SPLASH Survey: III. Measuring the Stellar Velocity Dispersion Profile
- The stellar population content of the thick disk and halo of the Milky Way analogue NGC 891
- Elemental Abundances in M31: Gradients in the Giant Stellar Stream
- Elemental Abundances in M31: Alpha and Iron Element Abundances from Low-Resolution Resolved Stellar Spectroscopy in the Stellar Halo
- The TREX Survey: Kinematical Complexity Throughout M33's Stellar Disk and Evidence for a Stellar Halo
- The Strikingly Metal-Rich Halo of the Sombrero Galaxy
- INSPIRE: INvestigating Stellar Population In RElics III. Second data release (DR2): testing the systematics on the stellar velocity dispersion
- The outermost stellar halo of NGC 5128 (Centaurus A): Radial structure
- Elemental Abundances in M31: Properties of the Inner Stellar Halo
- The survey of planetary nebulae in Andromeda (M31) VI. Kinematics of M31 inner-halo substructures and comparison with major-merger simulation predictions
- New Surface Brightness Fluctuations Spectroscopic Technique: NGC4449 and its Stellar Tidal Stream
- The halo of M105 and its group environment as traced by planetary nebula populations: II. Using kinematics of single stars to unveil the presence of intragroup light around the Leo I galaxies NGC 3384 and M105
- Constructing the Milky Way Stellar Halo in the Galactic Center by Direct Orbit Integration
- Detailed accretion history of the supermassive black hole in NGC 5972 over the past 10 years through the extended emission line region
- MUSE library of stellar spectra
- Searching for Milky Way twins: Radial abundance distribution as a strict criterion
- The extended HI halo of NGC 4945 as seen by MeerKAT
- The extended Planetary Nebula Spectrograph (ePN.S) early-type galaxy survey: The specific angular momentum of ETGs