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

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

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.

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A new instrument…

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

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…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

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

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

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

How do you create a deep field?

- Select a carefully chosen random location in the sky 10

Field Location Options

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UDF

Hubble Ultra Deep Field 12

Yes, mostly

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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.

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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

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

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.

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eXtreme Deep Field (XDF)

Garth D. Illingworth Webinar September 2012

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XDF Moon

Garth D. Illingworth Webinar September 2012

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Garth D. Illingworth Webinar September 2012

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Garth D. Illingworth Webinar September 2012

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Garth D. Illingworth Webinar September 2012

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Garth D. Illingworth Webinar September 2012

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Hubble eXtreme Deep Field 24

How XDF lets

us

see the early universe

HUDF XDF Galaxy Light

Galaxies earlier than 800 Myr after the Big Bang can only be seen in infrared light (“redder” than visible light) observed wavelength [ microns ] We need near-infrared images to see them!

Credit: STScI

Garth D. Illingworth (Galaxy Light) Webinar September 2012

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XDF reveals galaxies unseen in our deepest visible-light HUDF images previous image HUDF new image XDF

Garth D. Illingworth Webinar September 2012

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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

Garth D. Illingworth Webinar September 2012

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Even more distant galaxies

- A redshift 10 galaxy 28

Why are the early times so important?

Years: 0.3 8 16 32 For both humans and galaxies the pace of development is not uniform: more things happen early on 29

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

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.

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CDF-S* region is rich in data (HST, Spitzer, Chandra, etc) [*Chandra Deep Field South]

CDF-South

1999-2000 Chandra CDF-S 2002-2003 ACS GOODS 2003 ACS HUDF 2003 NICMOS HUDF 2004 Spitzer GOODS 2003-2007 NICMOS 2005 HUDF05 2009 ERS 2009-2010 HUDF09 2010-2011 Chandra 4Ms 2010-2012 CANDELS 2012-2013 Ellis All these data were available within 3 months.

~22 ’ x 22 ’

Garth D. Illingworth STScI May 2010 Workshop

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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

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.

700 600 500 400 300 200 100 0 Papers Team HDF HDFS GOODs UDF COSMOS 34

Galaxy Zoo: Hubble

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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

Full-scale model

6.5m James Webb Space Telescope

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JWST improvements over Hubble ’s resolution The Hubble UDF (F105W, F105W, F160W) Simulated JWST 39

JWST improvements over Hubble ’s resolution The Hubble UDF (F105W, F105W, F160W) Simulated JWST 40

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

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

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/m • Multi-layered, deployed sunshade 2 ) • Deployed, segmented primary mirror •

L2 Orbit allowing open design/passive cooling

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JWST Launch Configuration

Long Fairing 17m JWST is folded into stowed position to fit into the payload fairing of the Ariane V launch vehicle Upper stage H155 Core stage P230 Solid Propellant booster

Stowed Configuration

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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.

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