1. The Role of Dwarf Galaxy Interactions in Shaping the Magellanic System: Implications for Magellanic Irregulars & Dwarf Spheroidals The Role of Dwarf Galaxy Interactions in Shaping the Magellanic System: Implications for Magellanic Irregulars & Dwarf Spheroidals Gurtina Besla Columbia Nitya Kallivayalil, Lars Hernquist, Roeland van der Marel, T.J. Cox & Dusan Keres

2. Image Credit: Miloslav Druckmuller (Brno University of Technology) Milky Way LMC SMC

3. Local Group & the Distance Morphology Relationship for Satellites Andromeda Milky Way The Local Group Tucana Cetus Antlia

4. Carlos Milovic F. - PixInsight Team http://www.pixinsight.com/ Biomedical Imaging Center - PUC “The Magellanic Clouds are not 'oddities' of Nature, but typical of a definite stage of the barred spiral sequence characterized by a specific kind of asymmetry” - de Vaucouleurs & Freeman 1972 Besla The LMC is the prototype for a class of dwarfs: Magellanic Irregulars

5. SMC: As a spheroidal galaxy? Stephane Guisard Zaritsky et al. 2000 See also Nidever et al. 2011 Besla

6. Nidever et al. 2010 Large Scale Morphology Besla LMC Leading Arm SMC Magellanic Stream Bridge

7. Dwarf Galaxy Evolution By studying the large scale gas morphology: What is the expected baryon loss rates from dwarf-dwarf tidal interactions? By studying the structure of the LMC: What is the dynamical state of the class of galaxies known as Magellanic Irregulars? By studying the structure of the SMC: What is the evolutionary relationship between gas rich, disk-like dwarfs and gas poor dwarf spheroidals? Besla

8. New Orbital History NFW potential for the MW V LMC = 380 +/- 18 km/s Kallivayalil et al. 2006 Piatek et al. 2008 Besla et al. 2007 3rd Epoch of data: V ~ 320 +/- 25 km/s (Kalllivayalil, van der Marel, Besla et al. in prep; New Vcirc, Baseline, Kinematic models) Image: Astronomy Magazine Besla First passage, or long period orbit (> 6 Gyr, e>0.7) (see also Shattow & Loeb 2009) STATIC MW MODEL

9. MW Mass Evolution Mass evolution following Fakhouri, Ma & Boylan- Kolchin 2010 Statistics from Millennium II : > 80% of surviving LMC’s about MW hosts at z=0 were accreted < 2 Gyr ago. (Boylan-Kolchin, Besla & Hernquist 2010) Kallivayalil, van der Marel, Anderson, Besla & Alcock 2012 in prep A First Infall is Favored in a LCDM Universe

10. SMC in orbit about the LMC (no MW) LMC tides remove an extended tail of gas from the SMC without the aid of MW tides GADGET2 (Springel 2005) SPH simulations Rvir

11. Gas Morphology of the Magellanic System LMC Leading Arm SMC Magellanic Stream Bridge Besla et al. 2012, 2010

12. Phookun et al. 1992 Magellanic Irregular NGC 4027 & 4027A ESO B,V,R wikisky Besla

13. LMC in HI Kim et al 2001 R Band Halpha (Bothun, Univ. Oregon) MIPS

14. A recent LMC-SMC collision Besla et al. 2012 arXiv: 1201.1299 Besla

15. De-projected

16. The Structure of the LMC and Magellanic Irregulars Besla

17. DIrr - DSph Connection Tidal stripping/harrassment (Kazantzidis et al. 2011a, Lokas et al. 2012, Klimentowkski et al. 2009, Mayer et al 2005 Resonances -- D’Onghia, Besla et al 2010) but see Kirby talk Mergers with dark satellites (Starkenberg & Helmi in prep) But Rotation? Major Mergers of Disky Dwarfs (Kazantzidis, 2011b - But no gas - BCD Connection?) Direct Collisions in Dwarf Groups Besla

18. SMC Stephane Guisard Zaritsky et al. 2000 See also Nidever et al. 2011 Stanimirovic et al. 2004 NO rotation (< 8 km/s) HI Gradient of 60 km/s To Bridge Besla

19. Gordon et al. 2009 SMC Structure: Herschel

20. SMC Kinematics: Simulation Results Bridge 40 km/s

21. Magellanic Irregular: NGC 4449 Besla How Isolated is Isolated? Martinez-Delgado et al. 2011

22. Summary Through these studies, we have shown that a picture in which the LMC and SMC are a binary pair of tidally interacting galaxies that has recently been accreted by the MW is consistent with - Cosmological expectations & HST PMs - The observed gas distribution of the system - The structure of the LMC: offset bar, characteristic of Magellanic Irregulars - The kinematics and structure of the SMC, establishing it as a transition object b/w a dIrr-dSph This process is expected to occur ubiquitously in small groups of low mass galaxies and may represent a generic mode of dwarf galaxy evolution that is independent of proximity to a massive host.