daniel eisenstein – univ. of arizona wfmos bob nichol on behalf of the wfmos/kaos collaborations...

Daniel Eisenstein – Univ. of Arizona

WFMOS

• Bob Nichol on behalf of the WFMOS/KAOS collaborations (see http://www.noao.edu/kaos)

• Thanks to Matthew Colless, Daniel Eisenstein and Karl Glazebrook for previous WFMOS presentations which I use here.

Bob Nichol - ICG, Portsmouth


Outline

•Science of acoustic oscillations (or “baryon wiggles”) and their detection.

•Standard rulers for measuring distances in the Universe.

•KAOS concept and WFMOS design

•Progress and future timeline



Baryon Oscillations

• Gravity squeezes the gas, pressure pushes back! They oscillate

• When the Universe cools below 3000K these sound waves are frozen in

• Seen in CMB at 380,000 years


Courtesy of Wayne Hu


Baryon Oscillations in Galaxies


Can we see evidence for these baryon oscillations in the distribution of galaxies?Unfortunately much weaker in the matter and washed out by non-linear growthPre-2005, “maybe” (Miller et al. 2001, Percival et al. 2001, Tegmark et al. 2002)

Eisenstein et al. 200546,700 LRGs over 3816 deg2 and 0.16<z<0.47

0.72h-3Gpc3

3.4 detection

SDSS LRG


Cole et al. 2005



Standard Ruler in Universe

• 4.7% measurement4.7% measurement of the distance to z=0.35 (effective redshift of LRG sample)

• 3.7% measurement3.7% measurement of relative distance to z=0.35 and the CMB (most robust measurement we can make)

• Assuming a cosmological constant, LRG measurements, in conjunction with the Tegmark et al. (2004) analysis, show the geometry of the Universe is flat to 1%.Universe is flat to 1%.


As we can accurately predict the absolute scale of these baryon wiggles, we have a “standard ruler” (angular diameter

distance) in the Universe analogous to a “standard candle” (Blake & Glazebrook 2003, Seo & Eisenstein 2003, Hu &

Haiman 2003)

Can we measure this standard ruler at higher redshift and thus constrain w(z)?


Can we do this with existing facilities?

• The challenge is to gain both survey volume (~1Gpc3) and high space density (few hundred per deg2). To do this with AAOmega and FMOS at z>0.5, one still needs to cover hundreds of deg2

to faint flux limits - many years will be needed.

• Can we do this with photometric redshifts? Maybe, but what one gains in area, one looses in detection sensitivity. One could detect (at a few sigma level) the “wiggles” in the SDSS LRG photometric survey in the range 0.4<z<0.6. But photo-z’s need to be accurately calibrated and presently the ~7000 2SLAQ LRGs only give z~0.05 for z>0.5 (Padmanabhan et al. 2004). Next generation of imaging surveys will be better (e.g. DES), but they will still need massive redshift surveys to accurately calibrate their photo-z’s.



KAOS


A quantum leap in spectroscopic efficiency. Thousands of fibres over a 1,5 degree field-of-view

on an 8-meter class telescope: over an order of over an order of magnitude increase in mapping efficiency of 2dFmagnitude increase in mapping efficiency of 2dF

z~1 survey with 2 million

galaxies with twice LRG

volume

1% accuracy

KAOS purple book (Seo, Eisenstein, Blake, Glazebrook)



• For Lambda, SNAP does slightly better than KAOS, but for other equations of state, comparable errors on w.

• Combining methods really help and will control systematics (angular-diameter distance compared to luminosity distance)

• Blake & Glazebrook (2003) give w ~ 0.1

• Same philosophy as 2dF, get started as soon as possible with interesting constraints within first two years (commissioning predicted to be 2011)


WFMOS

• KAOS was highlighted in the Gemini Aspen process

• Gemini has now commissioned a feasibility study for the design of a wide-field MOS (WFMOS) to perform a KAOS-like survey (AAO, NOAO, Johns Hopkins, Oxford, Durham, Portsmouth, CADC, Arizona)

• Fast-track study due to end early this year (Feb 22) with a quick decision

• Baseline design: ~5000 fibres, ~1.5deg FOV, high and low res spectrographs, Gemini or Subaru

• Study will include, amongst other things:

Detailed modeling of the observing strategies, eg z bins, galaxy targets, etc (see Bassett et al. 2004), Revisit predictions and comparisons with other surveys

Better numerical simulations (Durham and Arizona)

Better cost and risk estimates (eg cost savings in software)

Discuss of location of WFMOS and technical issues eg. SDSS low res spectrographs at JHU



SDSS JHU spectrographs

Every photon counts!



Other ScienceFacility instrument and archival research

See Purple Book on KAOS website

Surveys

Proposals

Archival: ~few thousand high-z SNe, Alcock-Paczsynki test (Yamamoto et al. 2004), high-z cluster counts (Newman et al. 2002), reciprocity relation (Bassett &

Kunz 2004) Bob Nichol - ICG,

Portsmouth


Summary


• Like 2dF, WFMOS will open a new window on the Universe

• WFMOS builds on the legacy and experiences of SDSS & 2dF

• Will provide strong constraints on the nature of dark energy and the history of our Galaxy within a few years

of operation

• Fantastic facility instrument for a host of extra science

• Feasibility study underway with decision this year

• Could be on the telescope early next decade


• Discuss physics of acoustic oscillations - simple physics

• We have detected them now at ~ 3 sigma level

• New tool for measuring distances in the Universe - already showed with SDSS to 4%! Can we detect wiggles at higher redshift and map w(z)?

• Can we do this with existing instruments? Can we do this photometrically? Probably not - need advances in multiplexing to get volume+space density. Need 10sigma detections now.

• KAOS concept via the Aspen process which has lead to the WFMOS feasibility study and design - details of this

• Lots of science with KAOS e.g. galaxy archeology! Galaxy evolution. Reciprocity relationship. High z supernovae.

• Summary - new window on the Universe. Lots of imaging surveys planned but KAOS/WFMOS is unique in it’s spectroscopic capacity and the natural successor to the 2dF & SDSS legacy.


How did galaxies form?

• Local universe is full of galaxies: Where did they come from? How did they form they way they did?

• Our theory predicts they form via gravity from tiny quantum fluctuations in the early Universe



Sound Waves in Early Universe

• For 400,000 years after the Big Bang, the cosmic microwave background photons are trapped in the ionized cosmic gas.

• These photons provide an enormous restoring pressure, causing the gas to resist being squeezed by gravity

• Therefore, fluctuations in the gas propagate as sound wavessound waves.

• This ends abruptly when the Universe cools below 3000K and the gas becomes neutral: Universe suddenly becomes transparent

Big

Ban

g Tod

ay

Recombinationz ~ 1000

~400,000 yearsIonized Neutral

Time



Cosmic Microwave Background

• Effect of this sound wave already discovered in relic light of the early universe i.e. the CMB!

• That was the Universe at 400,000 years. Can we see these sound waves today?



Theory of the sound wave• At first, sound wave expands at 57% of the speed of light, then slows as the gas changes from ionized to neutral (red = ionized, green = neutral)

• Final size is reached after one million years. Today, that radius is 500 million 500 million light yearslight years.

• Central peak is overdense in dark matter. Outer ring is overdense in gas. Both are Both are seeds for the formation of seeds for the formation of galaxiesgalaxies.Our theory accurately Our theory accurately predictspredicts an excess of galaxy pairs an excess of galaxy pairs

separated by 500 million light-years: this would be the separated by 500 million light-years: this would be the “SMOKING GUN” “SMOKING GUN” that only gravity was important to explain that only gravity was important to explain the rich structures of galaxies and clusters of galaxies we the rich structures of galaxies and clusters of galaxies we see todaysee today Bob Nichol - ICG,

Portsmouth

QuickTime™ and aGIF decompressor

are needed to see this picture.


The Sloan Digital Sky Survey• The Sloan Digital Sky Survey

is a survey of (one quarter) of the northern sky. Over 200 scientists from 14 institutions around the world.

• Here we report on a sample that covers 10% of the sky.

• Luminous red galaxy sample: special spectroscopic sample of 47,000 galaxies that extends to z = 0.47, 6 billion light years away.

SDSS Telescope in Apache Point, New Mexico


Largest volume ever surveyed Largest volume ever surveyed with galaxies (This is why we with galaxies (This is why we

can see this wave)can see this wave)


700,000 light years

500 Million Light Years

Credit: SDSSA slice of the SDSS



The Correlation Function

• The correlation function is the probability of finding pairs at a given separation, above that of a random distribution.

Excess of galaxies separated by 500 million

light years



What does it mean?

• We have detected the sound wave in the Universe at two very different epochs (400,000 yrs after Big Bang and present-day). This is important because our theory of gravitational structure formation predicts that such features should have been preserved. Detecting the sound wave in the galaxies is the “SMOKING GUN”SMOKING GUN” that our theory is correct.

• Better yet, the sound wave is an object of fixed size, a “standard ruler” or “cosmic yardstick”. This means that we can measure its apparent size anywhere in the Universe, and determine how far it is away because we know its true size.



Looking back in time in the Universe

FLAT GEOMETRYCREDIT: WMAP & SDSS websites

CM

B


FLAT GEOMETRY

SD

SS

GA

LAX

IES




SD

SS

GA

LAX

IES

CM

B


OPEN GEOMETRY




CM

B


CLOSED GEOMETRY

SD

SS

GA

LAX

IES


UNIVERSE IS FLAT TO 1% UNIVERSE IS FLAT TO 1% PRECISIONPRECISION



Dark Energy

• In 1998, two groups used distant supernovae to discover the acceleration of the expansion history of the Universe.

• supernovae were fainter than expected, implying that they were further away.

• The cause of this is completely unknown but almost surely exotic new physics. It has been dubbed “dark dark energyenergy”. Our detection requires dark energy to be correct!

• Now we can map the expansion of the Universe using our “cosmic yardstick”. This is a robust and innovative new method for cosmologists and will spawn future surveys of the Universe.



More Information

• http://cmb.as.arizona.edu/~eisenste/acousticpeak

• http://www.dsg.port.ac.uk/~nicholb/wiggles

• [email protected]



Thanks to....

• The science analysis team was supported by several grants from the National Science Foundation, as well as funds from the University of Arizona, the Sloan Foundation, and NASA.

• The SDSS is supported by the Alfred P. Sloan Foundation, NASA, the National Science Foundation, Dept of Energy, the Japanese Monbukagakusho, the Max Planck Society, and the Participating Institutions: University of Chicago, Fermilab, the Institute for Advanced Study, the Japanese Participation Group, the Johns Hopkins University, the Korean Scientist Group, the Max Planck Institute for Astronomy, the Max Planck Institute for Astrophysics, New Mexico State University, the University of Pittsburgh, the University of Portsmouth, Princeton University, the US Naval Observatory, and the University of Washington.



EXTRA SLIDES

• EXTRA SLIDES FOR Q&A



Cosmic Yardstick?


If we know the true size of something, we can estimate how far it is away by it’s apparent size

Satellite photos of Earth via

Google can now be used to measure distances


Color SDSS Data (Hogg & Blanton)

LRG


Life is more complicated•Universe is composed of many perturbations, all superimposed.

•We do not expect to see bulls-eyes in the galaxy map. Indeed, the ring is only 1% of the height of the center.

•The whole analysis is statistical. Therefore need massive datasets like SDSS


daniel eisenstein – univ. of arizona wfmos bob nichol on behalf of the wfmos/kaos collaborations...

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