1. T. GirardStars: Young, Old and Variable – May 18-21, 2014 T. Girard Yale University The Glint on Magellan's Prow: Young Stars in the Leading Arm of the Magellanic Stream ______________________________________________________

2. T. GirardStars: Young, Old and Variable – May 18-21, 2014 “Score Machine” Ames city-league softball, ~ early 1980’s

3. T. GirardStars: Young, Old and Variable – May 18-21, 2014 A more relevant team... Casetti-Dinescu et al. 2014, (ApJL 784, 37) “Recent Star Formation in the Leading Arm of the Magellanic Stream” Christian Moni Bidin Univ. Catolica del Norte, Antofagasta, Chile Dana Casetti SCSU & Yale University Rene Mendez Universidad de Chile Santiago, Chile Kathy Vieira CIDA Merida, Venezuela Vladimir Korchagin Southern Federal University Rostov-on-Don, Russia Bill van Altena Yale University

4. T. GirardStars: Young, Old and Variable – May 18-21, 2014 Location, location, location… credit: www.eso.org – Yuri Beletsky

5. T. GirardStars: Young, Old and Variable – May 18-21, 2014 “a conglomerate of stars put together in a manner of two clouds”  Antonio Pigafetta (1524) Magellanic Clouds:  Over the Edge of the World by Laurence Bergreen

6. T. GirardStars: Young, Old and Variable – May 18-21, 2014 Magellanic Clouds: The Gaseous Stream Nidever et al. 2010  Figure 9. Magellanic Stream and Clouds in H I (red) with an optical all-sky image (blue, white, and brown; Mellinger 2009) in Aitoff projection with the direction to the Galactic Center at the center.

7. T. GirardStars: Young, Old and Variable – May 18-21, 2014 Magellanic Clouds: The Gaseous Stream Nidever et al. 2008 Gas velocity Gas density Model constraints:  Reproduce the various components of the gaseous Magellanic Stream; spatial and 1D velocity distribution.  Reproduce the current locations and 3D velocities of the Clouds.

8. T. GirardStars: Young, Old and Variable – May 18-21, 2014 Magellanic Clouds: Orbits & Interaction “New” orbit: HST-based , Kallivayalil et al. 2006 Old orbit: (based on matching MS, spatially) MW-Clouds interaction is currently under dispute!

9. T. GirardStars: Young, Old and Variable – May 18-21, 2014 Magellanic Clouds: Modeling the Interaction Diaz & Bekki (2012) SMC: N-body LMC, MW: rigid potentials Cloud-cloud interaction: 1 st encounter: ~2 Gyr ago, MS formation 2 nd encounter: ~200 Myr ago, Bridge formation MW-Clouds interaction: 1 st pericenter passage: ~2.5 Gyr ago 2 nd pericenter passage: now

10. T. GirardStars: Young, Old and Variable – May 18-21, 2014 Magellanic Clouds: Modeling the Interaction Diaz & Bekki (2012) SMC: N-body LMC, MW: rigid potentials

11. T. GirardStars: Young, Old and Variable – May 18-21, 2014 Magellanic Clouds: Modeling the Interaction Diaz & Bekki 2012 (model) Nidever et al. 2010 (observations) Radial velocity distribution

12. T. GirardStars: Young, Old and Variable – May 18-21, 2014 Magellanic Clouds: Modeling the Interaction Diaz & Bekki 2012, Nidever et al. 2010 Spatial distribution: MS, LA, Bridge are of tidal origin, primarily material pulled out from the SMC. LA is poorly explained by all models; gas hydrodynamics most likely plays a role.

13. T. GirardStars: Young, Old and Variable – May 18-21, 2014 Magellanic Clouds: LMC Absolute Proper Motion Diaz (2013, personal communication)

14. T. GirardStars: Young, Old and Variable – May 18-21, 2014 OB-type Star Search: A Cross-Catalog Approach Photometry Astrometry/Photometry GALEX DR5 (Bianchi et al. 2011) 2MASS (Skrutskie et al. 2006) APASS (Henden et al. 2011) NUV J V all-sky 1771-2831Å, eff = 2315.7Å, NUV lim = 20.8 all-sky (also made use of 6x2MASS) AAVSO all-sky survey (B,V, g, r, i) 10 < V < 17.0,  V ~ 0.06 mag SPM4 (Girard et al. 2011) , V  < -20 o, V lim ~17.5  V ~ 0.05 mag

15. T. GirardStars: Young, Old and Variable – May 18-21, 2014 OB-type Star Search: A Cross-Catalog Approach

16. T. GirardStars: Young, Old and Variable – May 18-21, 2014 OB-type Star Search: A Cross-Catalog Approach -2.0 ≤ (NUV-V) 0 ≤ 0.0 -1.2 ≤ (V-J) 0 ≤ -0.2 (  NUV ≤ 0.10,  J ≤ 0.15)  ≤ 8.0 mas/yr (   ≤ 4.0 mas/yr) 13.0 ≤ V 0 ≤ 17.0 E(B-V) ≤ 0.5 Final Selection Criteria

17. T. GirardStars: Young, Old and Variable – May 18-21, 2014 Results: 567 OB-type star candidates (from an initial ~4 million) Casetti-Dinescu et al. 2012 H I density (Nidever et al. 2010) OB-type Star Search: A Cross-Catalog Approach

18. T. GirardStars: Young, Old and Variable – May 18-21, 2014 OB star candidates include a well-populated SMC wing, extending in a narrow band toward the LMC to RA ~ 3.4 h, possibly reaching to the LMC; two branches partially surrounding the SMC; well-defined concentrations at the ends of the LMC bar, and a well-populated LMC periphery; several groupings in the LA; a few scattered candidates in the MS. OB-type Star Search: The Extended Clouds Region

19. T. GirardStars: Young, Old and Variable – May 18-21, 2014 OB-type Star Search: The Extended Clouds Region OB star candidates include a well-populated SMC wing, extending in a narrow band toward the LMC to RA ~ 3.4 h, possibly reaching to the LMC; two branches partially surrounding the SMC; well-defined concentrations at the ends of the LMC bar, and a well-populated LMC periphery; several groupings in the LA; a few scattered candidates in the MS.

20. T. GirardStars: Young, Old and Variable – May 18-21, 2014 OB-type Stars in the Leading Arm: Spectroscopic Follow-up Obtained spectra of 42 candidates in the Leading Arm, in April 2013 IMACS on 6.5m Baade telescope, 1 Å resolution, 3700-5300 Å range  Spectral Type, RV, log g, T eff ( υ sini, log[N He /N H ] ) Twin 6.5m Magellan telescopes: Baade and Clay Las Campanas, Chile

21. T. GirardStars: Young, Old and Variable – May 18-21, 2014 OB-type Stars in the Leading Arm: Spectroscopic Findings  = fast rotator Casetti-Dinescu et al. 2014

22. T. GirardStars: Young, Old and Variable – May 18-21, 2014 OB-type Stars in the Leading Arm: Spectroscopic Findings Found 19 young, massive stars, including... five with RVs consistent with Leading Arm membership; plus one O6V star, i.e., ~40 M  and very young (~1 Myr). Casetti-Dinescu et al. 2014

23. T. GirardStars: Young, Old and Variable – May 18-21, 2014 OB-type Stars in the Leading Arm: Stars of Interest ID RV (kms) vsini (kms) Teff (K) log glog[N He N H ]Sp.Type B.02 168 ± 4 [ 0 ] 16000 ± 4003.76 ± 0.09 [ -1 ]B4III B.03 229 ± 5 [ 0 ] 17500 ± 11003.86 ± 0.18-1.60 ± 0.18 B3IV B.14 207 ± 5 300 15800 ± 7003.60 ± 0.15 [ -1 ]B4/5III B.15 248 ± 5 [ 0 ] 14800 ± 7004.17 ± 0.15-2.10 ± 0.33 sdB A.15 166 ± 6 280 13400 ± 6003.67 ± 0.18 [ -1 ]B7III A.19 234 ± 6 260 17200 ± 19004.03 ± 0.36-1.58 ± 0.42 B3IV A.08 71 ± 11[ 0 ]43700 ± 12004.47 ± 0.12-1.20 ± 0.39O6V

24. T. GirardStars: Young, Old and Variable – May 18-21, 2014 OB-type Stars in the Leading Arm: Spectroscopic Findings For the five young, LA members (RV>150 km/s)... Distances are ~20 kpc from the Sun, (or ~18 kpc from the Galactic center, i.e. roughly the extent of the Galactic disk). Ages are ~100 Myr, i.e. recently formed. Gray band is kinematical distance to a particular high- velocity cloud in the LA. (McClure-Griffiths et al. 2008) = RV>150km/s,  = O6V star Casetti-Dinescu et al. 2014

25. T. GirardStars: Young, Old and Variable – May 18-21, 2014 Summary:  Young, massive stars have been found in the Leading Arm of the gaseous Magellanic Stream  Their location suggests recent interaction of gas in the Leading Arm with that of the outer edge of the Milky Way  Implying that hydrodynamical effects are at play and must be included in Clouds/MW interaction models  A single, more distant and extremely massive/young O6V star also has been identified, unquestionably formed in situ  Stay tuned for more...

26. T. GirardStars: Young, Old and Variable – May 18-21, 2014 And a little press is always nice...