1. Felix J. “Jay” Lockman GBT Principal Scientist NRAO, Green Bank Gas without stars in the Local Group and other Science Highlights from The Green Bank Telescope WUStL April 2014

2. 2 100 meter diameter unblocked Receivers cover 0.1 to 100 GHz Excellent point-source sensitivity Unsurpassed sensitivity for low surface-brightness emission >85% of total sky covered δ ≥-46° Location in the National Radio Quiet Zone Key capabilities of the GBT WUStL April 2014

3. 3 The National Radio Quiet Zone WUStL April 2014 location The National Radio Quiet Zone is unique in North America “No cellphone, no Wi-Fi: Living in America's quietest place” Kevin Monahan, Producer, NBC News http://news.yahoo.com/video/quiet-zone-where-no-cell-193638410.html

4. 4 Unblocked Optics for High Dynamic Range WUStL April 2014 Unique GBT optics give it factor ~10 greater dynamic range than conventional telesopes

5. 5 University of Georgia, Sept 2011 Optimized receivers 8 meter secondary Unique GBT optics give it Point source sensitivity of a ~120m telescope With its state-of-the art receivers it has Point source sensitivity √2 better than VLA at ≲ 2 GHZ

6. 6 University of Georgia, Sept 2011 2209 actuators The Active Surface in 2009 achieved rms < 240μ at night, the goal is 210μ The world’s largest telescope operating at mm wavelengths At 3mm the GBT is as sensitive as ALMA

7. 7 New: 4mm receiver for Spectroscopy and VLBI at 68-92 GHz! WUStL April 2014

8. 8 >6000 hours a year for astronomy 24/7 25% at freq≥18 GHz Dynamic Scheduling WUStL April 2014 Ron Maddalena, prognosticator 6-8 projects run each day

9. 9 * >1200 scientists and their students have used the GBT since 2009 * Many are not “astronomers”, but physicists, planetary scientists, chemists,... * The typical GBT proposal has * 5 Authors * One of whom is a student * One of whom is from a non-US institution * Demand for use of the GBT is as great as demand for the Very Large Array * Four new receiving systems in the works (Penn, Stanford, Berkeley, BYU, WVU) Who Uses the GBT? WUStL April 2014

10. 10 WUStL April 2014 science.nrao.edu/facilities/gbt

11. Research areas of the most-cited GBT publications Pulsars and compact objects Gravity and General Relativity Galactic HI, HII regions and Supernova Remnants Interstellar Chemistry The internal structure of Mercury Evolution of spiral galaxies Pre-stellar molecular cores and star formation Studies of a binary black hole HI content of galaxies CO emission from z>5 galaxies The magnetic field in the Galactic Center Anisotropies in the cosmic IR background WUStL April 2014

12. 12 WUStL April 2014 Bi-static radar studies with Arecibo transmitting GBT receiving

13. WUStL April 2014 Campbell, B.A. et al JGR-P 2014 optical

14. WUStL April 2014 Campbell, B.A. et al JGR-P 2014 70cm radar

15. WUStL April 2014 Campbell, B.A. et al JGR-P 2014 TiO 2 abundanc e

16. 16 Why is a planet like a disco ball? Its radar return is speckled WUStL April 2014 Speckle pattern is tied to the rotation of the body

17. Observing Strategy (J.-L. Margot et al.) Illuminate target with radar from Goldstone Record echoes at Goldstone and Green Bank Cross-correlate the two echo time-series (the alignment time is ~minutes) WUStL April 2014

18. 18 When is a planet like a raw egg? When it has a molten core. Goldstone + GBT Bistatic Radar “Large Longitude Libration of Mercury Reveals a Molten Core” Margot et al. 2007 Science Determining the rotation of Mercury to a few parts in 10 6 WUStL April 2014

19. 19 WUStL April 2014 The GBT is the world’s premier pulsar observatory (Quiet Zone, collecting area, receivers, detectors, sky coverage) The Pulsar Renaissance Fastest Pulsar Most Massive Pulsar Pulsars in Globular Clusters Tests of General Relativity Relativistic Spin Precession Pulsar in a three-body system

20. 20 WUStL April 2014 The Shapiro Delay

21. 21 WUStL April 2014 GBT measurements of the radio pulsar J1614-2230 Orbital inclination = 89.17(2) deg Companion mass = 0.500(6) solar Pulsar mass = 1.97(4) solar Demorest et al. (2010) Residual delay μs This pulsar near 2 M ⊙ set the record for pulsar mass, and the densest matter known in the Universe

22. 22 WUStL April 2014 A Pulsar in a Triple System Ransom et al. Nature (2014) Masses: 1.4378(13), 0.19751(15), 0.4101(3) M ⊙ Angle between orbital planes: 1.20(17)x10 -2 deg

23. 23 Using pulsars to directly detect gravitational radiation WUStL April 2014

24. 24 WUStL April 2014 Predicted Power in Gravitational Radiation Pulsar timing

25. 25 WUStL April 2014 GBT Very Large Array (VLA) Diam A digression on the sensitivity of radio telescopes angular resolution = λ/D point source sensitivity ∝ 4r 2 Na resolved source sensitivity ∝ 4 r a 2 N a / Diam 2 / receiver noise

26. 26 ✴ for an unresolved (point) source, signal strength is proportional to collecting area ✴ for a resolved source it depends on the configuration of the collecting area ✴ time to detect goes as signal -2 point source resolved source WUStL April 2014 A digression on the sensitivity of a radio telescope

27. 27 WUStL April 2014 Surface brightness efficiency Instrumentf 21cm HPBW GBT19.1’ Arecibo13.2’ VLA-D ∼ 10 2 46” VLA-C ∼ 10 3 14” VLA-B ∼ 10 4 4.3” ASKAP ∼ 10 3 GBT VLA-D Diam A digression on sensitivity For a given collecting area, the brightness sensitivity is always greatest for a filled aperture

28. WUStL April 2014 This is why the VLBA can’t detect anything cooler than 10 5 K

29. 29 ✴ Extended source “short spacing” data ✴ Specialized or high-performance receiving systems ✴ Low surface brightness phenomena WUStL April 2014 Filled aperture radio telescopes

30. 30 Studies of the chemical content and evolution of star-forming clouds WUStL April 2014

31. propenal cyanoformaldehyde ketenimine propanal carbodiimide ethanimine acetamide cyclopropenone methyltriacetylene C6H-C6H- Some (of the 17) New GBT Molecule Detections Interstellar anions Chemistry for its own sake Linking ISM Chemistry to the origin of life on Earth Molecules/Chemistry as a tool for understanding star formation H 2 O (water) H 2 CO (formaldehyde) HCOOH (formic acid) CH 3 OH (methanol) HOCH 2 CH 2 OH (ethylene glycol) CH 3 CO 2 H (acetic acid) CH 3 CH 2 OH (ethyl alcohol) CH 2 OHCHO (glycolaldehyde)

32. A Sharp Transition to Coherence in Dense Cores Pineda et al 2010 NH 3 WUStL April 2014

33. HC 7 N: A Chemical “Clock” in a Molecular Cloud? Friesen et al 2013, MNRAS [NH 3 ]/[HC 7 N] WUStL April 2014

34. 34 GBT Detection of H 2 O Masers in Active Galactic Nuclei Discovered by the GBT Monitored by the GBT Imaged by the VLBA + GBT YIELD: Mass of the Black Hole Conditions in Accretion Disks Geometric measurement of H 0 e.g., UGC 3789 H 0 = 68.9 ± 7.1 km s -1 Mpc -1 (Reid et al 2013, ApJ, 767, 154) WUStL April 2014

35. 35 GBT High-Resolution SZE in a Galaxy Cluster Mroczkowski et al. (2012) WUStL April 2014 MUSTANG Bolometer array at 90 GHz

36. 36 HI “Intensity Mapping” WUStL April 2014 At large redshift the HI from individual galaxies cannot be seen, but their collective signal is detectable. This technique was developed on the GBT by Ui-Le Pen, Jeffrey B. Peterson et al.

37. 37 HI “Intensity Mapping” at z=0.8 using the GBT WUStL April 2014 Masui et al. (2013) This provides information on the HI content and structure in the HI distribution at z~1.

38. HI disks of galaxies N HI = 10 21.5 cm -2 T b = 65 K t ≈ 2x10 -5 f 2 secInstrument f2f2f2f2 21 cm HPBW GBT19.1’ Arecibo13.2’ VLA-D ∼ 10 4 46” VLA-C ∼ 10 6 14” VLA-B ∼ 10 8 4.3” HI edges of galaxies N HI = 10 19.5 T b = 0.6 K t ≈ 0.2 f 2 sec THINGS VLA Survey Walter et al. 2008 at 30” resolution 3σ=10 19.5 at 6” resolution 3σ=10 20.5 Neutral Hydrogen (HI) in galaxies t = 21cm 3σ detection time WUStL April 2014

39. 39 “On the continuing formation of the Andromeda Galaxy: Detection of HI Clouds in the M31 Halo” Thilker et al 2004 ApJ Text Extraplanar HI N HI = 10 18.5 T b = 0.06 K t ≈ 20 f 2 secInstrument f2f2f2f2 GBT1 VLA-D ∼ 10 4 VLA-C ∼ 10 6 VLA-B ∼ 10 8 GBT Detection of High-velocity HI Clouds Around Andromeda 10 6-7 M ⊙ WUStL April 2014 What is the origin of this gas?

40. High Velocity Clouds around galaxies M31 -- GBT Thilker et al. 2004, ApJ, 601, L39 contours at 0.5,1,2,10,20 x 10 18 HI Masses = 10 6-7 M ⊙ M33 -- Arecibo Grossi et al. 2008, A&A, 487, 161 lowest contour 2x10 18 The Milky Way has HVCs covering 40% - 80% of the sky

41. 41 The “Smith” High Velocity Cloud Hydrogen image of the inner Milky Way (from old survey data) GBT WUStL April 2014

42. The “Smith” Milky Way High Velocity Cloud 2 kpc dist = 12.4 ± 1.3 kpc R = 7.6 ± 1.0 kpc z = -2.2 kpc M HI > 2x10 6 M ⊙ size ≈ 3 x 1 kpc No Stars! Wakker et al (2008) Lockman et al (2008, 2014) HI from new unpublished GBT survey WUStL April 2014 If you are looking for a good project...

43. WUStL April 2014 Smith Cloud Milky Way Position Velocity Smith Cloud edges decelerated by Milky Way shedding mass into the halo

44. The Smith Cloud has ionized gas 2 kpc dist = 12.4 ± 1.3 kpc R = 7.6 ± 1.0 kpc z = -2.2 kpc M HI > 2x10 6 M ⊙ size ≈ 3 x 1 kpc No Stars! H+ data from WHAM (Wisconsin H-alpha mapper) M H+ > 10 6 M ⊙ [N\H] = 0.14 - 0.44 Lockman et al (2008, 2014) Hill et al (2009) At M31 ≈0.084 K WUStL April 2014 GBT HI

45. WUStL April 2014 The Smith Cloud is bound to the Galaxy Milky Way V esc ~ 500 km/s Smith Vtot ≲ 300 km/s Smith V θ ≈ 260 km/s Lockman et al (2008, 2014)... and will hit the Galactic plane adding angular momentum to the disk ✔ ✔✔

46. Several million times the mass of the Sun fresh gas for new stars in the Milky Way

48. 30 Million Years from Now

49. 49 z>0 (above the plane) z<0 (below the plane) current location Sun 5 Myr intervals crosses the plane in 30 Myr The Smith Cloud Trajectory?? Where did the Cloud arise? WUStL April 2014

50. Nichols & Bland-Hawthorn (2009) -- DM confined Does the Smith Cloud have dark matter?

51. 51

52. WUStL April 2014 Nichols, Mirabal, Agertz, Lockman, Bland-Hawthorn (2014, submitted) Does the Smith Cloud have dark matter?

53. 53 HI in the Local Group of Galaxies 1 Mpc WUStL April 2014 Galaxy Formation is a Continuing Process M33 M31

54. 54 WUStL April 2014 The M81 group Optical + VLA + GBT Chynoweth et al 2009 Group HI N HI = 10 18.5 T b = 0.06 K t ≈ 20 f 2 sec Galaxies in groups interact

55. WUStL April 2014 M31 Interactions (Lewis et al 2013) GBT 21cm HI N HI = 10 17.5 T b = 0.006 K t ≈ 2 000 f 2 s GBT survey

56. 56 9’ resolution 15’ resolution WUStL April 2014 Smith Cloud Discrete HI Clouds between M31 and M33 Wolfe et al. (2013, Nature)

57. 57 The M31-M33 HI clouds are not part of the high velocity cloud systems of M31 or M33 WUStL April 2014 M33 HVC M31 HVC Wolfe et al. (2013)

58. Discrete HI Clouds between M31 and M33 Smith: M HI > 10 6 M ⊙ Diameter 1x3 kpc No stars in any of these! Not self-gravitating WUStL April 2014 Wolfe et al. (2013, Nature)

59. 59 WUStL April 2014 The Cosmic Web (a simulation) Interaction? or Cosmic Web?

60. The Smith Cloud -- What is it? Remnant of a disrupted satellite? -- Where are the stars? Cold flow accretion? -- Metal Abundances? A Dark Galaxy? -- Can we prove that dark matter is present? The Smith Cloud -- What’s next? New GBT HI Survey Completed (2014) GBT observations of “leading clouds” published (2014) Nichols et al analysis of DM dominated models (2014) ✔ New VLA survey of Faraday Rotation Analyzed (2014) HST Observations of metallicity and ionization stage (?) WUStL April 2014

61. 61 NATURE May 9, 2013 WUStL April 2014 log(MHI): 4.6-5.6 M ⊙ size: <3 - 6.4 kpc

62. The M31-M33 Clouds -- What’s next? GBT HI Observations Continuing (2014) HST observations of metallicity and ionization stage (?) The M31-M33 Clouds Remnants of a past interaction?  Time scale for cloud survival wrong?  What about IC 10? Dwarfs or Dark Galaxies?  Why the alignment with M31-M33? Condensations from an intergalactic filament?  The filament would link M31-M33 WUStL April 2014

63. 63 The potential of HI studies at 10 17 cm -2 – Flow of gas into and out of the Milky Way and other galaxies – Tracing past interactions – The cosmic web? (The HI is a trace constituent of mostly ionized gas) The challenge – Signals are very weak, and yet likely extended – Possible with current instruments, it just takes time Near term – Better receivers -- Tsys=10 K? – Phased array feed receivers -- soon will become competitive – EVLA-E -- f≈0.25 Long term – SKA? No advantage at all. Studies of almost nothing in the 21cm line WUStL April 2014