Exploring the Depths of the Universe Jennifer Lotz Hubble Science Briefing Jan. 16, 2014
Hubble is now observing galaxies 97% of the way back to the Big Bang, during the first 500 million years 2
Challenge: Can we peer deeper into the Universe than the Hubble Ultra Deep Field before the launch of the James Webb Space Telescope? 3
Extragalactic Astronomy 101 1. the speed of light is finite distance = look-back time 2. the universe is expanding distance = velocity 3. objects moving away from us look redder redshift = distance = look-back time 4
1. distance = time 8 minutes the Sun 3 million years Andromeda Earth 13 billion years distant galaxy 13.7 billion years We see distant objects as they were in the past because their light takes a long time to reach us echo of the Big Bang 5
Velocity away from our galaxy 2. distance = velocity the universe is expanding objects farther away are moving away faster Distance from our galaxy Hubble 1929 6
3. velocity = redshift redshift = distance = time velocity N. Wright / www.astro.ucla.edu The light from objects moving away from us is shifted redward. 7
Galaxy redshifts are primarily due to expansion of space, not Doppler shift distant galaxy Emitted blue light Earth Expanding universe stretches light to longer wavelengths Redshift z = stretch factor minus one stretched to green ESO animation: http://www.eso.org/public/videos/redshiftv/ then red (or even infrared) when observed 8
Fainter (4. Astronomer s unit of brightness) Astronomers measure brightness in magnitudes Larger magnitudes are fainter (backwards!) Magnitude = -2.5 log10(brightness) Faintest star the human eye can see is 6 th magnitude Hubble Ultra Deep Field reaches 30 th magnitude = a factor of 4 billion times fainter than what we can see with naked eye Figure from http://sci.esa.int/education/35616-stellar-distances/ Frontier Fields reaches ~10x fainter than Ultra Deep Field = 40 billion times fainter than human eye can see. 9
visible light 10
when the universe was young.. blue = 0.0 K green = 2.7 K red = 4.0 K 380,000 years after the Big Bang microwaves NASA/WMAP Science team 11
When the universe was young... blue = 2.7249 K green = 2.7250 K red = 2.7251 K 380,000 years after the Big Bang NASA/WMAP Science team 12
from the Big Bang to the Milky Way 13
The Hubble Deep Field - 1995 14
The Hubble Deep Field South- 1998 15
The Hubble Ultra Deep Field -2004 new camera on Hubble = new deep field 16
Science Highlights from Deep Fields detection of faint galaxies at look-back times < 1 billion years after the Big Bang cosmic star-formation history peaked ~ 10 billion years ago Galaxies grew in size and mass over this time, and changed their shapes from irregular to smooth Most distant supernovae used to measure distance, confirm accelerating universe Accreting supermassive black holes are found in galaxies at look-back times as early as 10-12 billion years ago. 17
How far away are galaxies? Hydrogen atom excitation levels Hydrogen atoms absorbs ultraviolet light from distant galaxies; this Lyman break is used to estimate their redshift. 18
The Hubble Ultra Deep Field -2009/2012 new camera on Hubble = new deep field 19
Cosmic star formation density The Hubble Ultra Deep Field -2009/2012 deep infrared images needed to detect the highest redshift galaxies Redshift/time since Big Bang 20
most distant galaxy candidate NASA/HST the Ultra Deep Field 21
Challenge: Can we peer deeper into the Universe than the Hubble Ultra Deep Field before the launch of the James Webb Space Telescope? posed to the Hubble Deep Fields Initiative science working group to develop an ambitious new community deep fields program HUDF ACS (optical) = 416 orbits WFC3 (IR) = 163 orbits =579 orbits of HST
Gravitational lensing in action Credit: Ann Feild (STScI) 23
Gravitational Lensing 24
Wine Glass Lensing Phil Marshall 25
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Challenge: Can we peer deeper into the Universe than the Hubble Ultra Deep Field before the launch of the James Webb Space Telescope? 27
Answer: Use Einstein s theory of general relativity - gravitational lensing - to go intrinsically deeper than the Ultra Deep Field. Gravitational lensing magnifies and stretches light from distant galaxies behind massive clusters, making them appear brighter and larger. Six very massive clusters of galaxies chosen as the best zoom lenses, with input from community. The Frontier Fields are being observed by NASA s Great Observatories - Hubble, Spitzer, and Chandra - over the next 3 years. 28
Frontier Fields will also observe 6 fields in parallel with the clusters, the second deepest observations of blank fields ever obtained. Simultaneous images are taken with Hubble s infrared camera WFC3/IR and the optical camera ACS; cameras will swap positions ~6 months later. 29
Deep observations of the Frontier Fields will: probe galaxies 10-20x intrinsically fainter than any seen before, particularly those in the first billion years of the Universe study the early formation histories of galaxies intrinsically faint enough to be the early progenitors of the Milky Way study internal properties of highly-magnified galaxies at high spatial resolutions provide a statistical picture of galaxy formation at early times 30
Deep observations of the Frontier Fields will: + map out dark matter, substructure in clusters + use 100s of multiple images as probe of distance, DE + search for (lensed) SN, transients in distant universe + deep and high-spatial resolution studies of z~1-4 galaxies, (UV escape fraction, sub-kpc structures and star-formation) + search for trans-neptunian objects in solar system + give parallaxes of Milky Way stars +??? 31
Spitzer Frontier Fields Infrared Spitzer Space Telescope will look at Frontier Fields in 2 filters redder than Hubble can see to depths of ~26.5 magnitude Spitzer crucial for confirming the distant galaxies, measuring their total stellar masses http://irsa.ipac.caltech.edu/data/spitzer/frontier/ 32
Chandra Frontier Fields MACS0717.5+3745 C. Jones-Forman MACS0416.1-2403 S. Murray X-ray detect hot cluster gas cluster mass and background accreting black holes archival Chandra data available for all of Frontier Fields; Chandra FOV encompasses both cluster + parallel fields new observations began this fall 33
HST Frontier Fields: Clusters Avoid dusty, bright regions of sky; visible from south (ALMA) and north (Mauna Kea) 34
HST Frontier Fields Abell 2744 MACSJ0416.1-2403 MACSJ0717.5+3745 MACSJ1149.5+2223. Abell370 Abell S1063 Hubble will observe 2 cluster per year, over 3 years 140 orbits per cluster 35
Abell 2744 - HST Epoch 1 completed November 2013 Cluster Parallel Blank Field 36
Abell 2744 - HST Epoch 1 completed November 2013 Cluster Parallel Blank Field 37
Abell 2744 Parallel Blank Field 38
Abell 2744 Cluster 39
Abell 2744 Cluster 40
Abell 2744 Cluster 41
Abell 2744 Cluster a model of the cluster s optics gives us the magnification power model credit: J. Richard, CATS team 42
background galaxies are magnified by factors up to ~10-20, providing the deepest yet view of the universe 43
lensed galaxies background galaxies are magnified by factors up to ~10-20, providing the deepest yet view of the universe 44
Number of galaxies Number of galaxies Abell 2744 + parallels are very very deep Fainter Fainter Optical ACS images (blue, green, yellow) reach ~29 th magnitude (dashed line) Infrared WFC3/IR images (orange, pink, red, dark-red) >~28.7 magnitude (observed magnitudes, not intrinsic magnitudes) 45
Number of galaxies Deepest view yet into the distant universe: Observed Fainter HUDF12 Intrinsically Fainter HUDF12 Take observed fluxes x lensing magnifications (average ~1.8x, max ~80x) intrinsically faintest Frontier Fields galaxies ~2.5 magnitudes (10x) fainter than Ultra Deep Field (blue dashed line) 46
Exploring the Depths of the Universe The Frontier Fields is combining the power of nature s telescopes - massive clusters of galaxies - with HST to provide the intrinsically deepest view of the universe yet. Parallel imaging is providing the second deepest observations of blank fields, and improve our statistical understanding of most distant and faint galaxies. NASA s Great Observatories -- Hubble, Spitzer, and Chandra - will observe the Frontier Field clusters and parallel fields over the next 3 years. The first set of Hubble observations of Abell 2744 are complete, and images have been publicly released. These reveal thousands of distant galaxies, many at intrinsic luminosities ~10 times fainter than ever seen before. http://www.stsci.edu/hst/campaigns/frontier-fields http://frontierfields.wordpress.com/ https://www.facebook.com/frontierfields 47
Exploring the Depths of the Universe Jennifer Lotz, Matt Mountain, & the Frontier Fields Team Space Telescope Science Institute,Spitzer Science Center www.stsci.edu/hst/campaigns/frontier-fields contact: lotz@stsci.edu 48