SMASHing the LMC. Yumi Choi. Montana State University/University of Arizona. Collaborator

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1 SMASHing the LMC Montana State University/University of Arizona Collaborator David Nidever, Knut Olsen, Gurtina Besla, Robert Blum, Dennis Zaritsky, Roeland van der Marel, Eric Bell, Carme Gallart, Maria-Rosa Cioni, Cliff Johnson, Kathy Vivas, Abi Saha, Thomas de Boer, Noelia Noel, Antonela Monachesi, Blair Conn, Alistair Walker, Matteo Monelli, Guy Stringfellow, David Martinez-Delgado, Pol Massana, and the SMASH team KICP June

2 The Magellanic System on the Sky Large Magellanic Cloud Small Magellanic Cloud ~50 kpc away ~60 kpc away KICP June

3 The Magellanic System on the Sky HI observation (Nidever et al. 2010) KICP June

4 40 Field55 Survey Fields (197) MW Midplane 6 14 DES Footprint h DR1 (61) (α,δ )=(97.5, 70.4) (ρlmc,palmc)=(5.3,102.6) (l,b)=(280.8, 27.2) (ρsmc,pasmc)=(24.5,126.4) (LMS,BMS)=(5.4,1.4) 16 9h Young MS 18 RGB RC 60 0 g0 Magellanic Stream Latitude h 22 MS 20 SG MW Foreground h Magellanic Stream Longitude 18 21h h (g i)0 2 3

5 I. The LMC Reddening Map and 3D Structure (Choi et al. 2018a) KICP June

6 Red Clump Stars as Extinction Probes & Standard Candles RC stars are confined in a narrow region on CMD Girardi (2016) KICP June

7 Observed Color and Magnitude Maps of the RC stars Color traces reddening Magnitude traces reddening & distance Choi et al. (2018a) KICP June

8 Intrinsic Color Radial Profile of the RC Compare with the previously measured metallicity radial gradient and agemetallicity relation in the LMC Choi et al. (2018a) Piatti & Geisler (2013) KICP June

9 Inferred Reddening Map SPIRE 250μm Choi et al. (2018a) KICP June

10 Warps and A Tilted Bar Choi et al. (2018a) Farther Closer A simulation of the MCs with a recent direct collision predicts a similar warp in the LMC disk (Besla et al. 2012) KICP June

11 II. A Ring-like Stellar Overdensity in the LMC (Choi et al. 2018b) KICP June

12 Properties of Magellanic Irregulars: gas-rich, one-armed spirals, and off-center bars (de Vaucouleurs & Freeman 1972) NGC 3664/3664A NGC 4027/4027A Significant fraction of Magellanic Irregulars do not have obvious companions. But, no companion does not mean no interaction in the past - a snapshot in the late merge stage (Besla et al. 2016) KICP June

13 A Long History of Detection, but Barely Studied First detection by de Vaucouleurs (1954a) Briefly mentioned or sign of the structure seen in Westerlund (1964), de Vaucouleurs & Freeman (1972), Irwin (1991), van der Marel (2001), Cioni & Habing (2003), Bica et al. (2008), Gaia data de Vaucouleurs (1955) Helmi et al. (2018) KICP June

14 Modeling the LMC: I. Star Count Map using Red Clump Red Clump Stars selected mostly from the SMASH data and partially from the DES data. Choi et al. (2018a) Choi et al. (2018b) KICP June

15 A Ring-like Overdensity at ~ 6º Continuous over ~270º in position angle Amplitude as large as 2.5 times higher than the smooth disk Choi et al. (2018b) KICP June

16 Stellar Age in the Overdensity: at least > 1 Gyr No stars older than ~ 1 Gyr in the overdensity (Choi et al. 2018b) ~200 Myr ~500 Myr ~1.8 Gyr ~1 Gyr ~1.5 Gyr KICP June

17 Spatial Correlation with the Intermediate-age Star Clusters Bica et al. (2008) Red: Bica clusters Blue: < 250 Myr (Nayak et al. 2016) Choi et al. (2018b) KICP June

18 A Looping Spiral is Common in Magellanic Irregulars! NGC 4618 NGC 3664 KICP June

19 Completely Wrapped up Spiral Arm? Repeated interactions with the SMC might do that! Besla et al. (2016) KICP June

20 Response to the Recent Direct Collision with the SMC? Stellar overdensity seen in MW-Sgr interaction simulations! Gomez et al. (2013) KICP June

21 III. The Very Extended Stellar Populations of the LMC (Nidever et al. 2018b) KICP June

22 Trace the LMC Periphery Using Old Main Sequence Stars Nidever et al. (2018b) KICP June

23 LMC Stellar Density Profile Nidever et al. (2018b) Detection of the old, metal-poor LMC stars out to ~21º (~18.4 kpc) KICP June

24 LMC Stars Out to ~21º 18.4 kpc LMC Milky Way SMC KICP June

25 Summary Derive the 2D reddening map and map the 3D structure of the LMC -> detect a tidally induced new warp Characterize the azimuthally-varying amplitude (up to 2.5 times higher than the smooth disk) and associated stellar ages (> 1 Gyr) of the ring-like overdensity in the LMC for the first time -> its origin might be related with interactions with the SMC Very extended LMC periphery out to ~21º -> accreted halo or tidally stripped outer disk material Comparing observed properties of the LMC disk with simulations allows us to understand the evolution of internal structures in the interacting dwarf galaxies and constrain the MCs mass and MW halo potential! KICP June