Virtual Observatory Tools

Transcription

1 Virtual Observatory Tools The Astronomer Annual Meeting 2009 John Murrell Croydon Astronomical Society 1

2 Introduction What is the Virtual Observatory? Two VO Tools Blind Astrometry - where is your image on the sky? Sinbad - what s in your image? Questions 2

3 The Virtual Observatory: objectives To make astronomical data from lots of sources covering different frequencies / energy available with one common consistent interface Provide the tools to allow you to obtain and analyse the data The VO only returns the data you have requested ie the search is done on remote servers Enable the reuse of data from other observatories Enable multi waveband investigations 3

4 What is held in the Virtual Observatory? Original instrument data - usually calibrated with instrumental artefacts removed. May be images, catalogues, spectra or any other form of data related to sky positions From Gamma Rays via visual to Radio Old data from plates such as the DSS and old catalogues 4

5 Calibrating your images FITS images have their location on the sky as well as the image size & orientation in the WCS header FITS images from amateur cameras / mounts do not normally contain the WCS header information To integrate your own images with the VO you need to perform an Astrometric Calibration This was quite difficult as you had to manually link the stars on your image with a reference image. 5

6 Astrometry.net Blind Astrometry Solver Interfaces Flikr Astromery - flickr.com/groups/astrometry/ Astrometry.net - Alpha Tester Install Astrometry software on your machine 6

7 Astrometry.net - Automated Astrometry You need to apply to become an Alpha Tester. The service is still under development so it may not work 7

8 What Astrometry.net returns Original Image converted to FITS with WCS Headers List of identified sources Other information see 3C273- astrometry.html Lots of examples on the Flikr site Works quite well even if stars are trailed or non-stellar objects in the frame 8

9 Caution The Flickr interface will make your images available for all Astrometry.net still retain some rights over any images you submit via Alpha testing You can always make the image unusable by blotting out part with a bar - it will still normally solve ok The FITS image may be limited by the number of bits of the original - JPEG are only 8 bits per colour 9

10 Now you know where your field is on the sky how do you find information on the objects in it or comparison images? Use another VO tool - Aladin 10

11 Aladin Sky Atlas at CDS Strasbourg The Aladin sky atlas is available in three modes: a Java Standalone application, a Java applet interface and a simple previewer. All free The Java standalone version - best for serious work as you can save & load images & status information to your computer 11

12 Aladin - Stand Alone Applet Start Screen ou can also open a cal image file - FITS with WCS if possible 12

13 Aladin - Quick Start 13

14 Aladin Load Additional Catalogue Data 14

15 Aladin Select Additional images 15

16 Image with SN selected 16

17 ocate the Supernova SN 2008S 17

18 Click on the Supernova & find information 18

19 Aladin - Colour Image 19

20 Examples from Aladin - Colour Image 20

21 M1 negative image Reverse the colours and adjust the contrast 21

22 M1 - Create a colour image from the three DSS plates & identify the Pulsar 22

23 Select the pulsar for more details as before 23

24 M45 + Sinbad overlay 24

25 Other uses for colour images Require 2 or 3 images in similar filters taken at different times Stars that are on all images both will show up as white Stars that have moved or were only on one or two images will show up as different colours. Use it to find Asteroids, High Proper Motion Stars, Novas, Variable Stars or Supernovae 25

26 Example : Binary Star WN0 7 26

27 Example: Binary Star WN0 7 The arrows indicate current position 27

28 Examples from Aladin - M16 28

29 H1 Shells in the SMC showing location size & velocity 29

30 Red objects in the Pelican Nebula -1 30

31 Red objects in the Pelican Nebula

32 Red objects in the Pelican Nebula

33 Sinbad - M45 33

34 Sinbad - M45 Multiscreen 34

35 Object Identification - Tago s variable in Cassiopeia discovered 30th October 2006 Original Image by Maurice Gavin Canon 20 D camera 35

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39 Aladin - Filters - Cassiopeia 39

40 More Information - EURO-VO ook here for xamples 44

41 Example Scientific Workflows 45

42 onfirming a supernova 46

43 Conclusions Astrometry.net is a useful tool to identify the location of your image on the sky and convert it to FITS You lose the ability to do photometric measurements if you start with JPEG Aladin allows you to explore your image in greater depth 47

44 The End Any Questions? The Aladin VO portal is at: European Virtual Observatory at: Plus the Amateur VO page on 48