Are the Magellanic Clouds on Their First Passage about the Milky Way?

By G. Besla, N. Kallivayalil, L. Hernquist, Brant Robertson, Thomas J. Cox, R. P. van der Marel, C. Alcock. 2007

440 citations recorded by the source corpus.

Recent proper-motion measurements of the Large and Small Magellanic Clouds (LMC and SMC, respectively) by Kallivayalil and coworkers suggest that the 3D velocities of the Clouds are substantially higher (~100 km s-1) than previously estimated and now approach the escape velocity of the Milky Way (MW). Previous studies have also assumed that the Milky Way can be adequately modeled as an isothermal sphere to large distances. Here we reexamine the orbital history of the Clouds using the new velocities and a ΛCDM-motivated MW model with virial mass Mvir = 1012 M☉ (e.g., Klypin and coworkers). We conclude that the LMC and SMC are either currently on their first passage about the MW or, if the MW can be accurately modeled by an isothermal sphere to distances ≳200 kpc (i.e., Mvir > 2 × 1012 M☉), that their orbital period and apogalacticon distance must be a factor of 2 larger than previously estimated, increasing to 3 Gyr and 200 kpc, respectively. A first passage scenario is consistent with the fact that the LMC and SMC appear to be outliers when compared to other satellite galaxies of the MW: they are irregular in appearance and are moving faster. We discuss the implications of this orbital analysis for our understanding of the star formation history, the nature of the warp in the MW disk and the origin of the Magellanic Stream (MS), a band of H I gas trailing the LMC and SMC that extends ~100° across the sky. Specifically, as a consequence of the new orbital history of the Clouds, the origin of the MS may not be explainable by current tidal and ram pressure stripping models.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/435666fc1a9a7410080812b7215456aa36ae11a8

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Citations in the corpus

Small Dwarf Galaxies within Larger Dwarfs: Why Some Are Luminous while Most Go Dark (2008, background): “…we assume that the entire halo of the galaxy has the same specific angular momentum as the disk, the total angular momentum of the LMC group is greater than the product of the ntire mass of the MW system times the specific angular momentum of the disk (e.g. Fich & Tremaine 1991; Besla et al. 2007).”
Vertical density waves in the Milky Way disc induced by the Sagittarius dwarf galaxy (2012, background): “Given its traditional mass (∼ 2% of the MW mass) and location (∼ 50 kpc) estimates, the LMC tidal field is not sufficiently strong to induce the observed vertical perturbation (e.g. Hunter & Toomre 1969; Besla et al. 2007, hereafter B07).”
THE SAGITTARIUS DWARF GALAXY: A MODEL FOR EVOLUTION IN A TRIAXIAL MILKY WAY HALO (2010, background): “Indeed, some recent lines of investigation suggest that they may have only recently fallen into the gravitational potential of the Milky Way for the first time (e.g., Besla et al. 2007), drastically limiting the time during which they could have torqued the orbit of the Sgr dwarf.”
There's no place like home? Statistics of Milky Way-mass dark matter haloes (2009, methodology): “A recent analysis of the LMC’s orbital history (Besla et al. 2007) based on the updated proper motions of the LMC (Kallivayalil et al. 2006) indicates that the LMC likely fell into the Milky Way’s halo within the last ∼ 3 Gyr.”
THIRD-EPOCH MAGELLANIC CLOUD PROPER MOTIONS. II. THE LARGE MAGELLANIC CLOUD ROTATION FIELD IN THREE DIMENSIONS (2013, background): “In Besla et al. (2007) our team studied the implied orbit of the Magellanic Clouds, and argued that they may be falling into the Milky Way for the first time.”
The role of dwarf galaxy interactions in shaping the Magellanic System and implications for Magellanic Irregulars (2012, background): “8 in Besla et al. 2007).”
SPITZER SAGE SURVEY OF THE LARGE MAGELLANIC CLOUD. III. STAR FORMATION AND ∼1000 NEW CANDIDATE YOUNG STELLAR OBJECTS (2008, methodology): “This is consistent with the new results (Kallivayalil et al. 2006b, 2006a; Besla et al. 2007) suggesting that the LMC is in its first passage with the Milky Way, having entered the virial radius of the dark matter halo 1–3 Gyr ago.”
The Orbital Poles of Milky Way Satellite Galaxies: A Rotationally Supported Disk of Satellites (2008, methodology): “Another problem arises for understanding the satellites in terms of dark matter theory from the models by Besla et al. (2007): based on the proper-motion measurements for the LMC and SMC (Kallivayalil et al. 2006a, 2006b), they concluded that if a CDM-motivated model for the Milky Way halo is…”
The Milky Way’s Circular Velocity Curve to 60 kpc and an Estimate of the Dark Matter Halo Mass from the Kinematics of ~2400 SDSS Blue Horizontal-Branch Stars (2008, background): “However, recent results on the LMC (Kallivayalil et al. 2006; Besla et al. 2007) indicate that not even the Magellanic Clouds may have been bound to the Milky Way for long, posing a potential conceptual problems for the use of satellite dynamics.”
Hunting for the Dark Matter Wake Induced by the Large Magellanic Cloud (2019, background): “Galaxy Models Table 1 summarizes the parameters of the adopted MW model.”
The Milky Way’s bright satellites as an apparent failure of ΛCDM (2011, background): “This result implies that the Magellanic Clouds are likely on their first passage about the MW (Besla et al. 2007), although this conclusion may depend on the mass of the MW (Shattow & Loeb 2009).”
A-type stars in the Canada–France Imaging Survey – II. Tracing the height of the disc at large distances with Blue Stragglers (2018, methodology): “These were also complemented with two additional runs taking into account the contribution of the Large Magellanic Cloud, assuming a first infall orbit (Besla et al. 2007; Kallivayalil et al. 2013).”
THE M31 VELOCITY VECTOR. II. RADIAL ORBIT TOWARD THE MILKY WAY AND IMPLIED LOCAL GROUP MASS (2012, methodology): “The virial radius rvir therefore satisfies ρvir ≡ 3Mvir/4πr3vir = ΔvirΩmρcrit, or in physical units (Besla et al. 2007) rvir = 206 h−1 kpc ( ΔvirΩm 97.2 )−1/3 ( Mvir 1012 h−1 M )1/3 .”
The Origin of the Magellanic Stream and Its Leading Arm (2007, methodology): “But the addition of a more realistic NFW potential for the MW produces the startling result of hyperbolic orbits for the MCs (Besla et al. 2007).”
Mass models of the Milky Way (2011, neutral): “Another possible source of information is the motion of the Magellanic clouds, but this can only be used straightforwardly if they can be assumed to be bound to the Milky Way – Besla et al. (2007) have shown that this may not be a valid assumption.”
The Masses of the Milky Way and Andromeda galaxies (2010, background): “Second, there are some suggestions that the Magellanic Clouds may not be bound, or even if bound may only be on its second passage and so may not be part of the relaxed distribution of satellite galaxies (Besla et al. 2007).”
THE STAR FORMATION HISTORIES OF LOCAL GROUP DWARF GALAXIES. I. HUBBLE SPACE TELESCOPE/WIDE FIELD PLANETARY CAMERA 2 OBSERVATIONS (2014, background): “…a massive galaxies can result in several effects, including the temporary enhancement of star-formation, as is thought to be the case of the SMC and LMC (e.g., Besla et al. 2007, 2012; Weisz et al. 2013) and the eventual quenching of star-formation (e.g., Teyssier et al. 2012; Slater & Bell 2013).”