1. 3D Spectroscopy Francisco Müller Sánchez Instituto de Astrofísica de Canarias La Laguna, España  Introductory Review and Observational Techniques  Science motivation for 3D Spectroscopy  Instrumentation  Preparation of Observations and Principles of Data Reduction  Data Analysis

3. Examples of SINFONI-AO: prototypical merger NGC6240 velocity flux stars molecular gas ionised gas 1”

5. Analysis of data cubes

6. Introductory Review and Observational techniques  Classical observational techniques  Strengths of 3D Data  Concepts of Adaptive Optics  Instrument techniques used to achieve 3D Spectroscopy Beckers 1993: ARA&A 31, 13 Hardy 1998: Adaptive Optics for Astronomical Telescopes Antichi 2009: ApJ, 695, 1042 Kissler-Patig 2005: Science perspectives for 3D spectroscopy also Sterne & Weltraum articles 1994 (Hippler, Kasper, Davies, Ragazzoni)

7. Ancient Mayan Photometry - An eclipse table that predicts times when eclipses may occur. - A Venus table that predicts the times when Venus appears as morning star and the other apparitions of the planet. - A Mars table that records the times when Mars goes into retrograde motion. A second Mars table that tracks the planet's motion along the ecliptic has recently been identified.

8. Photometry The venerable photographic plate and its more recent version, the CCD, provide objective information in two dimensions concerning the brightness, I(x,y), of an extended object or area of sky.

9. Spectroscopy

10. Spectroscopy Long-slit spectroscopy enables us to split the light that reaches us not just from a point but also from an entire line of points into its constituent colours, thereby providing us with information in two dimensions - position along the slit, x, and colour, lambda:I(x,lambda)

11. Why not combine them? 3D spectroscopy attempts to get closer to the fundamental goal of astronomical observing techniques, which is to record the direction, wavelength, polarization state and arrival time for every incoming photon over the largest field of view. In fact using 3D spectroscopy, the wavelength and the incoming direction in a 2D field of view are recorded in a (x,y,λ) data cube, in contrast with standard techniques which either do imaging over a 2D field, or spectroscopy along a 1D slit.

12. Color 3D spectroscopy yields datacubes

13. Scanning Spectrophotometers (Fabry-Perot interferometer) The FPI can be used to obtain monochromatic images over a full two- dimensional field of view with spectral resolutions comparable to those of grating spectrographs. In a Fabry-Pérot the distance between the plates can be tuned in order to change the wavelengths at which transmission peaks occur in the interferometer.

14. Imaging Fourier Transform Spectroscopy

15. Imaging Spectroscopy

16. Scanning Long-Slit Spectroscopy

17. Energy-Resolving Detectors Tantalum superconducting tunnel junctions Peacock et al. 1998

18. Integral-Field Units

19. Concept of integral-field spectroscopy

20. Don’t confuse IFS with MOS (Multi Object Spectroscopy) LUCIFER at the LBT

21. Three ways of doing IFS

22. Lenslets (TIGER Approach)

23. Example of lenslet IFU: SAURON @ WHT

24. Fibers (ARGUS approach)

25. Example of fibers IFU: INTEGRAL @ WHT

26. Slicers

27. SINFONI - made @ MPE Example of Image slicer IFU: SINFONI @ VLT

28. Strengths of 3D data 1 - No slit losses: high system efficiency - Less time consuming - More accurate radial velocity determination - Background estimate can be obtained simultaneously - Kinematics of crowded regions - It doesn’t suffer from changes of several exposures

29. Strengths of 3D data 2. Einstein’s cross section

30. Atmospheric Turbulence for Kolmogorov statistics, the refractive index structure function is van Karman model includes inner (~1cm) & outer (~30m) scales for a wavefront propagating through the atmosphere, the phase structure function is quantified using the structure function

31. C N 2 at Mt Graham (LBT site) Atmospheric Turbulence C N 2 is refractive index structure constant. Turbulence limits the resolution of a telescope to λ/r 0 instead of λ/D. The integral of C N 2 is Fried’s parameter and variance of wavefront aberrations is just

32. Everything depends on C N 2 coherence length where coherence timescale where assumes Taylor’s frozen flow hypothesis where isoplanatic angle

33. Impact of a Perturbed Wavefront  blur  Point focus parallel light rays can be focussed light rays affected by turbulence how well spatial frequencies are transferred through the optical system resulting shape of a point source

34. coma & trefoil Modal Decomposition Most common & simplest for a circular aperture are Zernike modes. For an annular aperture, Karhunen-Loève modes are better.

35. A simple adaptive optics system open & closed loop images Neptune (Keck, NGS) star (Calar Alto, LGS)

36. Shack Hartmann Sensor Measures first derivative of wavefront (gradients) Displacement of spots is proportional to the wavefront tilt Many algorithms possible for centroiding Easy to extend to very high order systems Divides pupil into subapertures (developed in 1900 by J.Hartmann)

37. Shack Hartmann Sensor

38. Piezo Actuator Mirrors 349 actuator DM wiring on back side reference block thin flexible (glass) mirror piezo actuators which contract & lengthen when voltages are applied incoming wavefront will be flat when it reflects off the mirror

39. Curvature Sensor (developed in 1994 by F.Roddier)

40. A few things to bear in mind - AO works better at longer wavelengths (dependence of r 0 on λ 6/5 ) e.g. consider a phase change of 250nm with respect to 500nm optical light and 2.2μm near infrared light. So at longer wavelengths, coherence length is greater & timescales are longer - One can measure in optical & correct in infrared (absolute phase change is same) - AO systems have to run fast (bandwidth ~1/10 of the frame rate) prediction would be great… time amplitude of aberration

41. Residual Wavefront Variance & Strehl Ratio coherence length isoplanatic angle total wavefront variance for large j (number of Zernike modes) Strehl ratio ratio of peak intensity to that for a perfect optical system coherence timescale

42. Sodium & Rayleigh Laser Guide Stars MMT VLT Keck sky coverage few % with NGS but ~50% with LGS (most coverage in galactic plane; almost none at galactic pole) Starfire Optical Range, Calar Alto, Lick, MMT, Keck, VLT, Subaru, Gemini North, WHT, Palomar 200”, Mt Wilson 100”, (LBT, Gemini South)

43. A few issues with Laser Guide Stars sodium density height (km) time (min) on-axis LGS spot off-axis LGS spot 1. laser technology 2. elongation of spot due to finite thickness of layer 3. variations in height of sodium layer 4. need for tip-tilt star

44. MultiConjugate Adaptive Optics 1 star & 1 DM 3 stars & 2 DMs MAD strehl maps reference stars high turbulence layer low turbulence layer telescope one wavefront sensor per star DM1 DM2 WFSs

45. MultiConjugate Adaptive Optics This is computationally complex Classical MCAO needs multiple guide stars (e.g. Gemini South MCAO needs 5 LGS & 3 NGS). Instead, one can use the layer oriented approach, with LGS or NGS. reference stars high turbulence layer low turbulence layer telescope one wavefront sensor per deformable mirror DM1 DM2 WFS1 LINC-NIRVANA on the LBT uses pyramid sensors to co-add the light from many faint stars on the detector; but note that the strehl ratio is expected to be limited & vary a bit over the field

46. Examples of LGS-AO: interacting galaxies IRAS 09061-1248 NACO-LGS/VLT UKIRT (archive) K-band image of these interacting galaxies shows the vast amount more detail that LGS-AO can reveal

47. Examples of LGS-AO: prototypical merger NGC6240 Komossa et al. 2003 Tecza et al. 2000 2µm continuum 1”

48. Examples of LGS-AO: prototypical merger NGC6240 velocity flux stars molecular gas ionised gas 1”

49. Examples of LGS-AO: high redshift galaxies

50. Future perspectives: FRIDA @ GTC

51. Future perspectives: SERPIL @ LBT

52. Multiple IFS: KMOS @ VLT

54. IFS @ ELT

55. Outlook for tomorrow’s lecture  Science perspectives for IFS  Galactic astronomy  The Galactic Center  Nearby AGN  Quasars and high-z galaxies

57. Bimorph Mirrors bimorph mirror for Gemini, showing the zones 2 layer piezo ceramic which bends when a voltage is applied continuous electrode control electrodes thin glass mirror incoming wavefront will be flat when it reflects off the mirror

58. Realistic Expectations Extreme AO (e.g. “planet finders”) aims for >90% strehl at K… but with bright stars AGN are not particularly bright (fainter than typical limit of R~15mag), and tend to be fuzzy with a relatively bright background. Off-axis correction is usually not an option. LGS performance can vary from 0.1” resolution to ~20% Strehl at K. One can do much better than the seeing limit, but don’t expect perfect performance every time; and beware of spatial & temporal variations 5” 600nm2.2µm 5” Circinus Galaxy no bright point source for AO reference; and bright background. with an IR-WFS (i.e. NACO)

59. adapted from Rigaut 2000 Multiple Layers of Turbulence Turbulence Layers with 2 turbulent layers, on- and off-axis wavefronts are different

60. adapted from Rigaut 2000 Deformable mirror Turbulence Layers Multiple Layers of Turbulence with 2 turbulent layers, on- and off-axis wavefronts are different and cannot be corrected with a single DM

61. Multiple Layers of Turbulence adapted from Rigaut 2000 with 2 turbulent layers, on- and off-axis wavefronts are different Deformable mirrors Turbulence Layers but they can be corrected with multi-conjugate DMs and cannot be corrected with a single DM