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Galaxies at Cosmic Dawn Revealed in the First Year of the Hubble Frontier Fields Initiative

Galaxies at Cosmic Dawn Revealed in the First Year of the Hubble Frontier Fields Initiative

Dr. Gabriel Brammer (ESA/AURA, STScI)

Hubble Science Briefing / November 6, 2014

Dr. Gabriel Brammer (ESA/AURA, STScI)

Hubble Science Briefing / November 6, 2014

A Look Back:  A Look Back:  

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The Early UniverseAs observed in the Cosmic Microwave Background Radiation (CMBR), structure in the universe 300,000 years after the Big Bang

consisted of tiny density fluctuations (1 in 100,000)

Graphic credit: Le Figaro

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A universe in a boxStart with the initial conditions determined from the cosmic

microwave background and let gravity do its thing….

http://www.illustris-project.org

z=4 z=2 z=1 z=0 (today)time ⇒

Dark M

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as

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z=4 z=2 z=1 z=0 (today)

time ⇒

Galaxies todayD

ark M

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as

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z=4 z=2 z=1 z=0 (today)

time ⇒

Galaxies todayThe local galaxy population:

Sloan Digital Sky Survey (SDSS)

ESA PR 53808

Dark M

atte

rG

as

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Cosmology and galaxy evolution

• Galaxies in the expanding universe flying apart (E. Hubble) causing the wavelengths of light from distant galaxies to be shifted redward ⇒ “redshift”, or “z”

• Given the cosmological model supported by the CMBR and many other observations (e.g., supernovae), the measurement of a galaxy’s redshift is both a ruler (how far is it from us?) and a clock (what was the age of the universe when the light we observe was emitted?)

• To build up an understanding of how galaxies form and evolve, we observe and characterize the galaxy population at different redshifts, which correspond to different epochs in the history of the universe

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Galaxy evolution

A problem: distant galaxies are faint and small!

Rela

tive

surf

ace

brig

htne

ss(S

DSS

@ z

=0.1

≡ 1

)

Redshift, z

Angu

lar s

ize

of th

e Su

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orb

it in

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e M

ilky

Way

(8 k

pc, i

n ar

csec

onds

)

Redshift, zz = 0, today13.7 Gyr after Big Bang 900 Myr after Big Bang

(Gyr: giga/billions, Myr: mega/millions of years)

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Galaxy evolutionThe Hubble Space Telescope provides the needed sensitivity and image quality to detect distant galaxies

1995

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1995

We can measure the total star formation history of the universe in deep Hubble observations!

P. Madau et al. (1996)

Redshift, z

Sta

rs f

orm

ed

per

year,

per

un

it v

olu

me

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Servicing HST: pushing ever further from “cosmic high noon” to “cosmic dawn”

Installing Wide-Field Camera 3, 2009 (NASA) 10

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2004

1995

Redshift, z

Sta

rs f

orm

ed

per

year,

per

un

it v

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2009-2012

2004

1995

Redshift, z

P. Oesch et al. (2014)

Sta

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orm

ed

per

year,

per

un

it v

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me

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2009-2012

2004

1995

Redshift, z

P. Oesch et al. (2014)

Sta

rs f

orm

ed

per

year,

per

un

it v

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me

“High noon” “Dawn”

14⇐ time 14

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The next step?

⇐ time

How can we use Hubble to efficiently and significantly go beyond the large investments of the existing deep fields

today, before the launch of the James Webb Space Telescope in 2018?

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Natural telescopes: gravitational lenses

Illustration by D. Coe, Z. Levay

The Hubble Ultra Deep Field Massive galaxy cluster (A million-billion times the mass of the sun in stars+gas+dark matter)

+

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Natural telescopes: gravitational lenses

Illustration by D. Coe, Z. Levay

Distortion and magnification of the distant galaxies behind the cluster=

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The HST Frontier Fields, year 1

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Abell 2744Cluster

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Abell 2744Cluster “Parallel”

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Scientific collaborationThe first year of Frontier Fields observations has formed the basis of more than 30 publications

with coauthors from 18 countries

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Science highlights

1. Improved determination of the dark matter distribution and total mass of the clusters themselves

2. “Ghost light” from galaxies torn apart in the Abell 2744 cluster

3. Numerous galaxy candidates at z > 7

4. A robust, multiply-imaged galaxy candidate at z ~ 10

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1. Cluster mass models

A reminder: only about 5% of the “stuff” in the universe (energy density) is composed of matter we know and understand, like stars, gas, and neutrinos.

Galaxy clusters are extremely massive (1014 M⊙ in stars, or, > 10 the GDP of the USA, in $) ⨉and dominated by dark matter.

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1. Cluster mass models

• Many multiply imaged lens arcs identified in the deep Frontier Fields imaging of the Abell 2744 and MACS 0416 clusters

• The arcs put strong constraints on the mass distribution in the clusters (e.g., stars plus dark matter)

• The total mass of the cluster constrained with a precision of only a few percent!

• The improved mass model also yields more reliable determination of the magnification map, which is necessary for interpreting the distant background galaxies

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1. Cluster mass models

Dozens of multipleimage pairs

Jauzac et al. (2014)

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1. Cluster mass models1. Cluster mass models

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Dozens of multiple image pairs

Jauzac et al. (2014)

Magnification map

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2. “Ghost light” of shredded cluster galaxies

Trujillo et al. (2014)

Galaxy clusters are a violent environment, with galaxies rushing around at thousands of kilometers per second.

Cluster galaxies can get shredded in the process, with the stellar remains strewn about the cluster

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3. Dozens of galaxies at z > 7

Ishikagi et al. (2014)Atek et al. (2014), Zheng et al. (2014)

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3. Dozens of galaxies at z > 7

Ishikagi et al. (2014)Atek et al. (2014), Zheng et al. (2014)

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4. A multiply-imaged galaxy at z~10

Detections only in the reddest HST infrared filters suggest a redshift of z~10.

Detecting multiple lensed images greatly increases the likelihood that the object is truly at high redshift and not rather a nearby interloper.

b c

a

a

b

c

Zitrin et al. (2010)

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Such faint objects can only be detected in the very long full Frontier Fields exposures!

4. A multiply-imaged galaxy at z~10

An HST orbit

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Such faint objects can only be detected in the very long full Frontier Fields exposures!

4. A multiply-imaged galaxy at z~10

1 orbit 2 orbits 8 orbits 24 orbits

a

b

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Working as a team

Hubble Space Telescope Spitzer Space Telescope Chandra X-ray Observatory

W.M Keck Observatory (Mauna Kea, HI)

European Southern Observatory, Very Large Telescope (Cerro Paranal, Chile)

Gemini Observatory (Mauna Kea, HI, and Cerro Pachón, Chile)

NASA’s Great

Observatories

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Many more exciting results to Many more exciting results to come! come!

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