Tidally Induced Offset Disks in Magellanic Spiral Galaxies

Pardy, Stephen; D’Onghia, Elena; Athanassoula, E.; Wilcots, Eric M.; Sheth, Kartik

doi:10.3847/0004-637x/827/2/149

Cited by 34 publications

(37 citation statements)

References 64 publications

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“…The fact that the SMC is in reality an extended body, and here we plot only the separation of the COMs, strengthens this argument further. This result is consistent with the model of Besla et al (2012), specifically their Model 2, in which the LMC and SMC pair have experienced a recent direct collision roughly 100 Myr ago, which also produces the off-center stellar bar and one-armed spiral of the LMC (see also Bekki & Chiba 2007;Pardy et al 2016).…”

Section: Impact Parameter and Timing Of The Last Smc-lmc Encountersupporting

confidence: 92%

The Proper Motion Field of the Small Magellanic Cloud: Kinematic Evidence for Its Tidal Disruption

Zivick

Kallivayalil

Marel

et al. 2018

ApJ

112

120

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We present a new measurement of the systemic proper motion of the Small Magellanic Cloud (SMC), based on an expanded set of 30 fields containing background quasars and spanning a ∼3 year baseline, using the Hubble Space Telescope (HST ) Wide Field Camera 3. Combining this data with our previous 5 HST fields, and an additional 8 measurements from the Gaia-Tycho Astrometric Solution Catalog, brings us to a total of 43 SMC fields. We measure a systemic motion of µ W = −0.82 ± 0.02 (random) ± 0.10 (systematic) mas yr −1 and µ N = −1.21 ± 0.01 (random) ± 0.03 (systematic) mas yr −1 . After subtraction of the systemic motion, we find little evidence for rotation, but find an ordered mean motion radially away from the SMC in the outer regions of the galaxy, indicating that the SMC is in the process of tidal disruption. We model the past interactions of the Clouds with each other based on the measured present-day relative velocity between them of 103 ± 26 km s −1 . We find that in 97% of our considered cases, the Clouds experienced a direct collision 147 ± 33 Myr ago, with a mean impact parameter of 7.5 ± 2.5 kpc.

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Section: Impact Parameter and Timing Of The Last Smc-lmc Encountersupporting

confidence: 92%

The Proper Motion Field of the Small Magellanic Cloud: Kinematic Evidence for Its Tidal Disruption

Zivick

Kallivayalil

Marel

et al. 2018

ApJ

112

120

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“…The bar is also known for its centre being offset with respect to the disc. Recent numerical simulations of dwarfdwarf galaxy interactions (Pardy et al 2016) with a 1:10 mass ratio show that during the encounter of the LMC and SMC morphological structures shift in relation to the LMC's dynamical centre. The stellar disc of the LMC becomes displaced under the effect of the gravitational potential, and this can persist for up to 2 Gyr, while the bar is never actually shifted, suggesting that the dynamical centre of the LMC is always coincident with the bar centre (de Vaucouleurs & Freeman 1972) rather than with the H i centre (Stanimirović et al 2004) as previously assumed.…”

Section: Lmc Morphologymentioning

confidence: 99%

The VMC survey – XXXIV. Morphology of stellar populations in the Magellanic Clouds

Youssoufi

Cioni

Bell

et al. 2019

Monthly Notices of the Royal Astronomical Society

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The Magellanic Clouds are nearby dwarf irregular galaxies whose morphologies show different properties when traced by different stellar populations, making them an important laboratory for studying galaxy morphologies. We study the morphology of the Magellanic Clouds using data from the VISTA survey of the Magellanic Clouds system (VMC). We used about 10 and 2.5 million sources across an area of ∼ 105 deg 2 and ∼ 42 deg 2 towards the Large and Small Magellanic Cloud (LMC and SMC), respectively. We estimated median ages of stellar populations occupying different regions of the near-infrared (J − K s , K s ) colour-magnitude diagram. Morphological maps were produced and detailed features in the central regions were characterised for the first time with bins corresponding to a spatial resolution of 0.13 kpc (LMC) and 0.16 kpc (SMC). In the LMC, we find that main sequence stars show coherent structures that grow with age and trace the multiple spiral arms of the galaxy, star forming regions become dimmer as we progress in age, while supergiant stars are centrally concentrated. Intermediate-age stars, despite tracing a regular and symmetrical morphology, show central clumps and hints of spiral arms. In the SMC, young main sequence stars depict a broken bar. Intermediate-age populations show signatures of elongation towards the Magellanic Bridge that can be attributed to the LMC-SMC interaction ∼ 200 Myr ago. They also show irregular central features suggesting that the inner SMC has also been influenced by tidal interactions.

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“…In both scenarios, the resulting structures are kinematically induced and thus expected to be short-lived (∼1-2 Gyr; Berentzen et al 2003;Yozin & Bekki 2014;Pardy et al 2016), although repetitive encounters can reform the structure. Furthermore, in both scenarios, the origin of the ring-like overdensity at 6 • is a product of tidal interactions with the SMC, rather than the MW.…”

Section: Constraints On the Lmc-smc Evolutionmentioning

confidence: 99%

SMASHing the LMC: Mapping a Ring-like Stellar Overdensity in the LMC Disk

Choi

Nidever

Olsen

et al. 2018

ApJ

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We explore the stellar structure of the Large Magellanic Cloud (LMC) disk using data from the Survey of the MAgellanic Stellar History (SMASH) and the Dark Energy Survey. We detect a ringlike stellar overdensity in the red clump star count map at a radius of ∼6 • (∼5.2 kpc at the LMC distance) that is continuous over ∼270 • in position angle and is only limited by the current data coverage. The overdensity shows an amplitude up to 2.5 times higher than that of the underlying smooth disk. This structure might be related to the multiple arms found by de Vaucouleurs. We find that the overdensity shows spatial correlation with intermediate-age star clusters, but not with young (< 1 Gyr) main-sequence stars, indicating the stellar populations associated with the overdensity are intermediate in age or older. Our findings on the LMC overdensity can be explained by either of two distinct formation mechanisms of a ring-like overdensity: (1) the overdensity formed out of an asymmetric one-armed spiral wrapping around the LMC main body, which is induced by repeated encounters with the Small Magellanic Cloud (SMC) over the last Gyr, or (2) the overdensity formed very recently as a tidal response to a direct collision with the SMC. Although the measured properties of the overdensity alone cannot distinguish between the two candidate scenarios, the consistency with both scenarios suggests that the ring-like overdensity is likely a product of tidal interaction with the SMC, but not with the Milky Way halo.

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Tidally Induced Offset Disks in Magellanic Spiral Galaxies

Cited by 34 publications

References 64 publications

The Proper Motion Field of the Small Magellanic Cloud: Kinematic Evidence for Its Tidal Disruption

The Proper Motion Field of the Small Magellanic Cloud: Kinematic Evidence for Its Tidal Disruption

The VMC survey – XXXIV. Morphology of stellar populations in the Magellanic Clouds

SMASHing the LMC: Mapping a Ring-like Stellar Overdensity in the LMC Disk

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