1. The Making of the Hubble Ultra Deep Field
Hubble Science Briefing
October 4, 2012
Massimo Stiavelli
Space Telescope Science Institute

2. Bold methods and new technology
What happens if you point the most powerful camera at the same point in the sky for an unprecedented length of time?
The Wide Field Planetary Camera 2 (WFPC2) 2

3. The Hubble Deep Field
This is exactly what Bob Williams, then STScI Director, decided to do in 1994.
The resulting image, known as the Hubble Deep Field, was the deepest picture of the Universe for many years. 3

4. 4

5. A new instrument…
- A new camera was installed on Hubble in March 2002: the Advanced Camera for Surveys. 5

6. …is a new opportunity
The new STScI Director, Steve Beckwith, decided to use the new, more powerful camera and point it for twice as long as the HDF on a fixed spot in the sky
The Hubble Ultra Deep Field (HUDF) was born 6

7. More than just fishing
The HUDF was doing more than just looking for the unknown
The Sloan Digital Sky Survey (SDSS) had identified the most distant quasars known, formed about 1 Gyrs after the Big Bang
Spectra of these objects, taken with Keck and other telescopes, were showing tantalizing clues… 7

8. Reionization of the Universe
Spectra of the most distant QSOs (quasi-stellar objects) told us that there was some neutral hydrogen in their vicinity
This is not seen for less distant QSOs
Galaxies must ionize all hydrogen about 1 Gyrs after the Big Bang 8

9. Could Hubble see them?
The question then was whether Hubble could see the galaxies responsible for reionization.
This was the science motivation for the HUDF 9

10. How do you create a deep field?
Select a carefully chosen random location in the sky 10

11. Field Location Options11

12. UDF
Hubble Ultra Deep Field 12

13. Yes, mostly 13

14. What about earlier times?
The galaxies found in the HUDF are the most distant that can be found in the optical portion of the electromagnetic spectrum; for more distant objects you must search the infrared portion.
The existing infrared camera (NICMOS) on Hubble gave some hints, but was not powerful enough to do the job. 14

15. Need infrared!
Earlier than 1 Gyrs after the Big Bang, galaxies are faint and relatively rare. We need a sensitive IR instrument: the IR channel of the Wide Field Camera 3 (WFC3). 15

16. More galaxies
WFC3 gave us samples of galaxies all the way to about 650 Myrs after the Big Bang.
As we go back in time, galaxies become rarer and fainter 16

17. eXtreme Deep Field (XDF)
Galaxies from 650 Myrs to 500 Myrs are elusive, but possibly within the reach of Hubble.
To study them one needs very long integrations, on the order of many hundreds of hours
The XDF is the latest and deepest attempt at studying these objects. 17

18. eXtreme Deep Field (XDF)
Garth D. Illingworth Webinar September 2012 18

19. XDF
Moon 19
Garth D. Illingworth Webinar September 2012

20. Garth D. Illingworth Webinar September 2012

21. Garth D. Illingworth Webinar September 201221

22. Garth D. Illingworth Webinar September 201222

23. Garth D. Illingworth Webinar September 201223

24. Hubble eXtreme Deep Field24

25. How XDF lets us see the early universe
Galaxies earlier than 800 Myr after the Big Bang can only be seen in infrared light (“redder” than visible light)
We need near-infrared images to see them!
observed wavelength [microns]
Galaxy Light
HUDF
XDF
Credit: STScI
Garth D. Illingworth (Galaxy Light) Webinar September 2012 25

26. XDF reveals galaxies unseen in our deepest visible-light HUDF images
previous image
HUDF
new image
XDF
Garth D. Illingworth Webinar September 2012 26

27. A red galaxy is not necessarily in the very early universe
Red galaxy colors can also be a sign for old stars, or for a lot of dust, which absorbs blue light
These two galaxies are at a distance of about half the age of the universe
This galaxy is about 13 billion light years away 27
Garth D. Illingworth Webinar September 2012

28. Even more distant galaxies
A redshift 10 galaxy 28

29. Why are the early times so important?
Years:
For both humans and galaxies the pace of development is not uniform: more things happen early on 29

30. Changing how astronomy is done
The HDF image and the source catalogs were made public.
Astronomers started using other telescopes to study specific objects, measure redshifts, obtain radio or X-ray data.
Most of these data were also made public.
From American Physical Society Newsletter May 1997 30

31. Papers
- The HDF and HUDF surveys led to 1,584 research papers, of which only 89 were published by the team.
The vast majority (94%) of these science papers were published by other scientists
- The HDF was the first case in astronomy of highly valuable data made public, and it encouraged open cooperation. 31

32. Garth D. Illingworth STScI May 2010 Workshop
CDF-S* region is rich in data (HST, Spitzer, Chandra, etc) [*Chandra Deep Field South]
CDF-South
Chandra CDF-S ACS GOODS
ACS HUDF
NICMOS HUDF
Spitzer GOODS NICMOS
HUDF05
ERS
HUDF09
Chandra 4Ms
CANDELS
Ellis
All these data were available within 3 months.
~22’ x 22’
Garth D. Illingworth STScI May 2010 Workshop 32

33. No more lonely hearts of the cosmos
The old-style way of doing research in small research group is being replaced by participation in large groups.
In the past astronomers tended to focus on a few specific objects  Now we focus on large samples 33

34. Non-hierarchical science
In a large collaboration working on a large sample, the difference between team members and non-team members starts to fade.
This opens up possibilities for unaffiliated astronomers, and also for the interested public. 34

35. Galaxy Zoo: Hubble 35

36. 36

37. JWST
Ultimately, in order to see more and fainter objects at these redshifts we need a telescope designed for infrared imaging: the James Webb Space Telescope 37

38. 6.5m James Webb Space Telescope
Full-scale model
6.5m James Webb Space Telescope 38

39. JWST improvements over Hubble’s resolution
The Hubble UDF
(F105W, F105W, F160W)
Simulated JWST
Could also stress:
1.) Success of archives
2.) Prize postdoctoral fellowships – Hubble, Spitzer, Chandra, ?Webb?  springboard for launching career in astronomy. 39

40. JWST improvements over Hubble’s resolution
The Hubble UDF
(F105W, F105W, F160W)
Simulated JWST
Could also stress:
1.) Success of archives
2.) Prize postdoctoral fellowships – Hubble, Spitzer, Chandra, ?Webb?  springboard for launching career in astronomy. 40

41. 41 HST/ACS HST/NICMOS Viz J H JWST/NIRCam JWST/NIRCam Viz (simulated)
03/07/2010 41

42. JWST-Spitzer image comparison
1’x1’ region in the HUDF – 3.5 to 5.8 mm
Spitzer, 1500 min. per band
(GOODS collaboration)
JWST, 16 min. per band (simulated)
(simulation by S. Casertano) 42

43. Hubble & James Webb to same scale
Astronaut
JWST is 7 tons and fits inside an Ariane V shroud
This is made possible by:
Ultra-lightweight optics (~20 kg/m2)
Deployed, segmented primary mirror
Multi-layered, deployed sunshade
L2 Orbit allowing open design/passive cooling 43

44. JWST Launch Configuration
JWST is folded into stowed position to fit into the payload fairing of the Ariane V launch vehicle
Long
Fairing 17m
Upper stage
H155 Core stage
P230 Solid
Propellant
booster
Stowed Configuration
Plan is to fly JWST with an Ariane 5
Contribution from our European Partner
Fairing size requires deployment no matter what launcher 44

45. Conclusions
WFC3-IR has allowed us to begin studying galaxies up to 650 million years from the Big Bang. Progress on these objects is going to be slow because they are too faint for any existing telescope, save for major efforts like the XDF. The James Webb Space Telescope has the sensitivity required to study these objects and even earlier ones. 45