What’s this about a Ring Around the Milky Way?

1. What’s this about a Ring Around the Milky Way? Heidi Newberg Rensselaer Polytechnic Institute In collaboration with: Brian Yanny Fermi National Accelerator Laboratory Eva K. Grebel, Michael Odenkirchen (MPIA-Heidelberg), Steve Kent (FNAL), Connie Rockosi (U. Wash.), Zeljko Ivezic (Princeton) and the REST of the SDSS collaboration

2. The Sloan Digital Sky Survey (SDSS) is a joint project of The University of Chicago, Fermilab, the Institute for Advanced Study, the Japan Participation Group, The Johns Hopkins University, the Max-Planck-Institute for Astronomy (MPIA), the Max-Planck-Institute for Astrophysics (MPA), New Mexico State University, Princeton University, the United States Naval Observatory, and the University of Washington. Funding for the project has been provided by the Alfred P. Sloan Foundation, the Participating Institutions, the National Aeronautics and Space Administration, the National Science Foundation, the U.S. Department of Energy, the Japanese Monbukagakusho, and the Max Planck Society.

4. The stars in galactic disks orbit the centers of the galaxy. The Sun’s orbital period is 200 million years. Galactic disks contain both old and young stellar populations.

5. The stars in the halos of galaxies also orbit the centers of the galaxies, but at random angles. Galactic halos contain only old stellar populations.

7. Mercury Venus Earth Mars Jupiter Saturn Uranus

8. Detecting the Sun’s gravity

9. Rotation speed vs. Distance from galaxy center Mass inside radius R vs. Distance from the galaxy center

17. 100,000 light years 150,000 light years Size of northern lump: 20 kpc by > 2 kpc by < 10 kpc

18. Kathryn Johnston

21. Squashed halo Spherical halo Prolate halo Exponential disk

27. INT Data SDSS Data

28. The Chicago Sun Times “Maybe our galaxy can kick any other galaxy’s butt”

29. Look at these BHB/A stars at g=20.3 near (l,b)= (190,30) degrees.

30. NGC2419 right nearby the 80 kpc stream piece! Globular Cluster was perhaps once associated with Sagittarius

33. The Modern Milky Way Old Thin Disk, Young Thin Disk, Thick Disk, Metal-Weak Thick Disk?? – are they formed separately, or by similar mechanisms? Bulge, Inner Halo, Outer Halo (maybe primarily composed of tidal streams) Dark Matter strongly clumped??? Galaxy formation strongly influenced by bottom-up merger processes

34. Indiana University??

35. LANL??

36. The Gasoline Galary, U. Washington

37. Ben Moore’s N-body site

38. Springel et al. 2001

39. Lucio Mayer (Ben Moore’s group)

40. Sloan Extension for Galactic Underpinnings and Evolution (SEGUE)  Segue (v.) – to proceed to what follows without pause Heidi Newberg1, Kurt Anderson2,3, Timothy Beers4, Jon Brinkmann3, Bing Chen5, Eva Grebel6, Jim Gunn7, Hugh Harris8, Greg Hennessy9, Zeljko Ivezic7, Jill Knapp7, Alexei Kniazev6, Steve Levine8, Robert Lupton7, David Martinez-Delgado6, Peregrine McGehee2,10, Dave Monet8, Jeff Munn8, Michael Odenkirchen6, Jeff Pier8, Connie Rockosi11, Regina Schulte-Ladbeck12, J. Allyn Smith10, Paula Szokody11, Alan Uomoto13, Rosie Wyse13, Brian Yanny14 8 US Naval Observatory, Flagstaff 9 US Naval Observatory, DC 10 Los Alamos National Laboratory 11 University of Washington 12 University of Pittsburgh 13 The Johns Hopkins University 14 Fermi National Accelerator Laboratory 1 Rensselaer Polytechnic Inst. 2 New Mexico State University 3 Apache Point Observatory 4 Michigan State University 5 ESA/Vilspa, Madrid, Spain 6 Max-Planck Heidelberg 7 Princeton University

42. SEGUE

43. Survey outline - specification • 2 years (may be spread out over 4 or more years) • $10 million • 3000 square degrees of new imaging data, including low latitude scans and extra stripes in the South Galactic Cap. • 250,000 spectra of Galactic stars in 200 directions, spread over 27,000 square degrees of the Galaxy (1-2 hour exposures)

44. Justification of target numbers Substructures that we have so far identified in the halo span tens of degrees. If we can scan the sky so as to leave no gaps larger than 10 or 20 degrees, then we will find every major sub-component of our galaxy. The proposed low latitude and South Galactic Cap scans come close to that goal. If there are 27,000 square degrees of sky available to the Northern hemisphere, and each plate represents 100-200 square degrees, then 200 plates will target Galactic structure on the scales it is known to vary.

45. SEGUE Science Drivers • Identify all major Galactic components by age/chemistry/kinematic properties (including in the Galactic plane) • Parameterize these structures in space • Use this information to build a description of the formation history of the galaxy, including the merger and chemical enrichment history • Measure dark matter quantity, distribution, clumpiness, and contribution to galaxy formation mechanism • Find or describe Pop III stars and their contribution to galaxy formation • Trace three dimensional structure of the ISM • Study the nature of star formation in young stellar populations in the disk