SkyMapper. Brian Schmidt. Stefan Keller, Patrick Tisserand, Gary Da Costa, Mike Bessell, and Paul Francis

Transcription

1 Brian Schmidt Stefan Keller, Patrick Tisserand, Gary Da Costa, Mike Bessell, and Paul Francis

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3 SkyMapper is a relatively small telescope - in an age of extremely large telescopes - why? Scientific impact / $ Now feasible to construct a telescope with sufficient sky coverage to image entire sky Equal photographic plates in coverage, surpass in uniformity, QE and noise Global collecting area (square meters) Global CCD area (Gpixels) Slide 3

4 The Rapid Imaging Survey Era Name Aperture (m) FOV (sq deg) Filter Set Areal Coverage Hemi sphere First Light SDSS 2.5 Drift scan ugriz π of 3/2π N Operating CFHT MegaCam ugriz <1000 N Operating SkyMapper uvgriz 2 π S Starting PanStarrs 1.8 (+3x) 7 grizy 3 π N Starting VISTA zyjhk 2 π S Starting VST ugriz ~5000 S 2011 Discovery Chn 4 2?? N Dark Energy 4 2? 5000 S LSST ugrizy 3 π S Slide 4

5 What is SkyMapper? 1.35m telescope with a 5.7 sq. degree field of view To conduct the Southern Sky Survey: Five year Multi-colour (6 filters) Multi-epoch (6 exposures, each filter) 2π steradians Limiting mag. g~23 Aiming for regular operations early 2009 Summary of program: Keller et al PASA 24,1 Slide 5

6 Who is SkyMapper? Slide 6

7 The SkyMapper Enclosure Rear Shutter Front Shutter Level 2 Service Level Level 3 Observing Space 11.5m tall Vent Door Level 1 Thermally Isolated Equipment Level 6m diameter Slide 7

8 Where is the SkyMapper Telescope? Slide 8

9 Telescope Optics 0.75m secondary Modified Cassegrain design 0.6m fused silica asphere 1.35m primary 2 x 0.45m fused silica spherics Telescope Focal length & f/ ratio mm f/4.78 Slide 9

10 SkyMapper Cassegrain Imager Being built by RSAA 16384x16384 pixel array Cooled with Closed-Cycle He system Shack-Hartmann system for focus, collimation, etc. 6 Filters slots (~10 second exchange time) Bonn shutter (2ms accuracy) Guider Shack-Hartmann Filters Shutter Slide 10

11 The SkyMapper CCDs 32 E2V CCD44-82 devices: 2048x micron pixel CCDs Broadband coated 40 micron (thick) devices Reduced fringing, inc. red response, without bad blue 16384x pixels Using new Pan Starrs controllers (Onaka) Readout in <15 seconds Readnoise ~6e 15 seconds Slide 11

12 The Design of the Southern Sky Survey Slide 12

13 The Southern Sky Survey Full Hemispheric coverage: ~4000 fields observed in six filters, six times per filter Cadence: hours, days, weeks, months, years star/galaxy photometry to 3% globally (g>18.5) astrometry to 50 (15 relative) milliarcsec 36 images of each object over 5 years proper motions to ±5(2) mas/yr. (i.e. σvtan=25km/s at 2.5 (6)kpc) parallax ±5 (2) mas (i.e. 20pc (50) σd=10%) survey complete in 5 years Slide 13

14 Optimised for Stellar Physics Encoded in the spectrum of each star is it Temperature, Gravity, and Chemical Composition Using filters we can isolate portions of the spectrum In designing our survey we sought to optimise our ability to determine the three important stellar parameters so SkyMapper not only compliments survey efforts in the northern hemisphere but enables us to tackle important astrophysics in an exciting new way. Slide 14

15 SkyMapper Filter Set Ex-atmosphere Slide 15

16 Expected Survey Limits u v g r i z 1 epoch epochs Sloan Digital Sky Survey comparison 22.0 n/a AB mag. for signal-to-noise = 5 from 110s exposures Slide 16

17 Challenge Observe All Southern Sky Images, 4069 fields ~15000 deg² : uncrowded fields ~ 6000 deg² : crowded ones Software : Fast Accurate Stable/Robust Slide 17

18 Calibration Plans Conduct Five-Second Survey in photometric conditions cover the southern sky w. 3x5 exposures: 8-15th mag During 5-s observe the highest two reference fields every 90 minutes primary standards: Stars in Walraven system with STIS spectrophotometry Anchor the deeper Main Survey to the Five-Second photometry and astrometry Enables the Main Survey to proceed under non-photometric conditions. Slide 18

19 ANUSF: Supercomputer Facilities with robot-driven tapes library as a gigantic disk of 1.2 Peta Bytes Pipeline : _Series of Perl scripts : Interface between data / Database _ Code C for scientific tools _ Database : PostgreSQL (need to manage info. for 1 billion objects) Slide 19

20 The Main Survey Combine images using Accurate World Coordinate System Dither pattern between images: eliminate ccd-gaps, cosmic, satellite tracks Mask saturated stars Detect Objects in combined images Use Info from all 6 filters for classification Objects defined from the Union of detections of all filters Slide 20

21 The Main Survey -Photometry Simplified by flat focal plane + good CCD cosmetics Need software that handles crowded and uncrowded fields with uniform output Use a modified version of SExtractor: bypass the detection process to use all photometric algorithms : SMSExPhot Functionality : easy to manipulate, many options Input : list of coordinates Apply photometry on each object on each individual frame Slide 21

22 Observation Scheduler The scheduler must respond to photometric/seeing conditions during a night. Photometric? Seeing > limit? Mode Yes No 5 SecSurvey Yes <2.5" 5 SecSurvey No No Main Survey Maximize the science output 1 st epoch : all filters consecutively - Star Colour 3 first epochs in (g,r) in less than 3 days : for Astrometric and photometric short term variation (TNO + RRlyrae/Cepheids) Optimize constraints for parallax measurement: (i,z) images spaced by 2-4 months Use a Score algorithm for field priority - weighted by amount of time field is observable in survey s remaining time. Deal with Quick Data Quality Check + ANUSF DataBase Quality to validate 1 field/ 1 filter Take care : distance of the Moon + Planets, reduce Airmass.. Seeing Dark Grey Bright Good (u,v,g,r,i,z) (g,r,i,z) (i,z) Average (g,r,i,z) (g,r,i,z) (i,z) Poor Poor seeing programs Slide 22

23 Siding Spring Observatory ANUSF Slide 23

24 What is in the Database Raw Images, Flatfielded images, combined images Photometry - aperture, PSF, Kron, Petrosian Astrometry Flags Derived quantity datasbase parallax, proper motion, best photometry classification (QSO, galaxy, star(type),...) Slide 24

25 Data Release Deliverables to the Outside User: -Data (epoch, RA, DEC, mags, galaxy shape info, ) to be available through a web-served interface which provides catalogs over a user defined area -Images to be available through a web-served interface which provides images over a user defined area Data release will occur after extensive data validation: -Five-Second data after closure in RA and trial application to concurrently obtained main-survey data -FDR Main Survey 3 epochs all filters -SDR Main Survey 6 epochs all filters Slide 25

26 Science Programs Utilising the Southern Sky Survey -Extremely Metal-Poor Stars -Galactic Structure -QSOs -Stromlo Missing Satellite Survey -Young Stars -Solar System -Globular Clusters Keller - Norris - Da Costa - Tisserand - Ragini Singh Jerjen - Mateo +... Bessell - Simon Murphy Francis - Michelle Bannister + M Brown Freeman - Yong Science Programs External to the Southern Sky Survey -Planetary Transit Search -GRB + Low-z Sne + transients -MgII of Southern Sky -Ha of Southern Sky -Variable Stars Daniel Bayliss Schmidt + T. Davis Freeman Bessell + Q. Parker Wood Slide 26

27 Blue Horizontal Branch Stars Slide 27

28 MS+BS Blue Horizontal Branch Stars logg=5 logg=2 HBA RRL ZAHB Teff: 10000K 6000K takes us out to distances >100kpc with low contamination Slide 28

29 Extremely Metal-poor Stars in the Halo Goal: find the first stars to have formed in the Universe: tell us about the assembly and chemical enrichment of the Galaxy v-g is dependent on the level of metal line blanketing in the blue continuum not perturbed dramatically by C-enhancement, chromospheric emission as affects objective-prism surveys F G Slide 29

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31 Extremely Metal-poor Stars in the Halo Scale HES numbers for increased area, depth ~130 [Fe/H]<-5 Select a sample with photometrically derived [Fe/H]<-4 and g<18 returns this sample of spectroscopic [Fe/H] Slide 31

32 High-redshift QSOs are among the most distant optical objects in the Universe, probing the Universe and host galaxies at 6% of its current age. Key objects for studying the reionisation of the Universe - where the first stars and black holes strip the electrons from Hydrogen. 50 objects are expected in the southern hemisphere Slide 32

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34 High-z QSOs Detection is simple: i-band dropouts. Contaminants: L+T dwarfs SDSS tells us we can expect of order 50 objects z<20.5 in the SSSS Detection limited by our i sensitivity (not z!) Proper motions can help remove L +T dwarfs as will J,H,K photometry initial follow-up with WiFES+2.3m and IRIS2+AAT Slide 34

35 Trans-Neptunian Objects Francis, Bannister, M. Brown (CalTech)... We have the potential to find the largest of the outer solar system dwarf planets in Kuiper Belt scattered Oort cloud comets What are a,e,i of these bodies - and how do these compare to theories of the creation of Kuiper belt and Oort Cloud. Previous searches only at low inclinations Possible to have a 15-16th mag Pluto yet undiscovered in Southern Hemisphere. Eris UB313 25% more massive than Pluto travels far from the ecliptic plane of the planets Slide 35

36 Search for extreme little Milky Way How many dwarf satellites galaxies are there in the Local Group? There is reason to believe that the census is not complete: New companions to MW and M31 have been found 2MASS turned up Sag and CMa dwarfs SDSS has turned up a gaggle of objects Understand how galaxies are built up Slide 36

37 Search for extreme little Milky Way satellites Slide 37

38 Draco, 83 kpc, -8.8 UMa, 100kpc, -6.8? Discovered by Willman et al from SDSS data Slide 38

39 Southern Sky Poor Seeing Time Survey Time Slide 39

40 SkyMapper Transient Search Measure Supernova Distance in the Near Universe to study Dark Energy Use Gravity induced motions to test predictions of gravity Explosion Physics s of all types of explosions Slide 40

41 Nicolas Regnault & Julien Guy from IN2P3 Slide 41

42 It s a long way to the top of S S O 1 Jan Our ARC DP grant starts. E1 Title: The Southern Sky Survey E2 Project Description, Aims and Background Project Description and Aims: We propose to use the robotic Great Melbourne Telescope (GMT) to car ry out an optical survey of the entire southern sky. The survey will be: Multi-Colour. We will observe at six wavelengths, from the near-uv to the near-ir 1. Photometric. We will measure the brightness of each object detected, at each wavelength, with systematic errors of less than 0.02 mag 2. Astrometric. We will determine the absolut e positions of the objects we detect with an accuracy of better than 0.05 arcsec. 3. Sensitive to variability. Each par t of the sky will be observed multiple times, to look for tim e variability and movement. The RSAA director has guaranteed that at least 80% of the Great Melbourne Telescope observing time will be devoted to this proj ect, over 5 years. We will generate 25 terabytes of data and will detect more than 10 9 objects. All calibrated data will be made publicly available on-line via the ANU supercomputer facility. We anticipate that the survey will be used for a n enormous variety of scientific projects by astrophysicists worldwide for decades to come. The team members, however, are particularly interested in the following science goals: Mapping the distribution of dark matter in the outer regions of our own galaxy. Searching for high redshift QSOs to probe the reionisation of the universe. Slide 42

43 My own picture from 20th January 2003 Slide 43

44 8 April Bushfire report to ARC 5. Supervise construction of a wide field (approx 7sq degree field of view) 1.8 meter telescope at Siding Spring Observatory. (New Goal) 6. Supervise construction of a >100 million pixel CCD array for the Siding Spring Survey Telescope. (New Goal) Slide 44

45 Aug 2004 Contract let for 1.35m SkyMapper Telescope to EOS. Slide 45

46 The Mirror Crack d The sequel The Mirror Crack d Part III The Mirror Crack d - The Final Chapter Dr. Zhivago to the rescue... Slide 46

47 Russians Deliver Primary more or less on time Slide 47

48 Secondary from SAGEM on time Slide 48

49 The whole thing put together mid 2007, in Tucson Slide 49

50 First light, Tucson, July 2007 Slide 50

51 Bonn-Shutter arrives on time Slide 51

52 Focal Plane Dewar assembled Slide 52

53 Slide 53

54 $40,000 of filter Slide 54

55 $2.5M of CCDs from E2V - arrive in 2006, on time Slide 55

56 Dome Slide 56

57 July 2008 Slide 57

58 Telescope to SSO Sep 2008 Slide 58

59 Telescope to SSO Sep 2008 Slide 59

60 Telescope to SSO Sep 2008 Slide 60

61 Telescope to SSO Sep 2008 Slide 61

62 Lady Bugs! Slide 62

63 EOS handed telescope to ANU mid-february 2009 Telescope points and tracks to spec via a Shack-Hartmann we also showed image quality at spec (~0.65 ) across the focal plane SkyMapper Focal Plane Array shipping on 16th of Feb. achieves 5e- readnoise in 12sec readout. Filters completed... Prelimary Science demonstration Regular Operations as soon as possible afterwards. Slide 63

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66 Brian Schmidt Stefan Keller, Patrick Tisserand, Gary Da Costa, Mike Bessell, and Paul Francis