# Presentation: 431277

## Observational Cosmology at Fermilab: 

**Observational Cosmology at Fermilab: **
**	*****Sloan Digital Sky Survey***
***	******Dark Energy Survey***
***	******SNAP***

*Gajus Miknaitis*
*Fermilab Users Meeting*
*May 31, 2006*

## Sloan Digital Sky Survey (SDSS)

- _Motivation_: study the distribution of matter in the universe by measuring the distribution of galaxies in space (2D + redshift)

- q

*CfA Redshift Survey (1986)*

## Sloan Digital Sky Survey (SDSS)

- _Motivation_: study the distribution of matter in the universe by measuring the distribution of galaxies in space (2D + redshift)

- q

- Imaging camera:
-    find galaxies, measure
-    their angular positions

*CfA Redshift Survey (1986)*

## Sloan Digital Sky Survey (SDSS)

- _Motivation_: study the distribution of matter in the universe by measuring the distribution of galaxies in space (2D + redshift)

- q

- Imaging camera:
-    find galaxies, measure
-    their angular positions

- Multi-object spectrograph:
-  measure galaxy redshifts
-  distance ≈ redshift

*CfA Redshift Survey (1986)*

## SDSS data set

**After ~5 years of operation, SDSS has:**
-  imaged more than 8,000 square degrees of the sky in five bandpasses
-  detected nearly 200 million celestial objects
-  measured spectra of more than 675,000 galaxies, 90,000 quasars, and 185,000 stars

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## visualization: David W. Hogg (NYU)

- visualization: David W. Hogg (NYU)
- with help from Blanton, Finkbeiner,
- Padmanabhan, Schlegel, Wherry

- data: Sloan Digital Sky Survey
- and the Bright Star Catalog

## SDSS & Large Scale Structure

- power spectrum of matter

- 1 megaparsec

## SDSS & Large Scale Structure

- power spectrum of matter

- 1 megaparsec

## Scientific impact of the SDSS

- As of May 30, 2006, **1080** refereed, published papers mention SDSS, “Sloan Survey” or make use of SDSS data
- Over 31,000 citations of these papers in the literature.
- 22 SDSS papers with more than 200 citations

**Some science highlights**
-  State-of-the-art Large Scale Structure measurements
- 3D power spectrum of matter
- detection of baryonic acoustic oscillations
-  Catalog of 105 quasars out to z≈7
-  Reionization of the universe at z=7 (Gunn-Peterson effect)
-  Catalog of 106 galaxy clusters to z=0.5
-  Tidal tails and stellar streams in our galaxy
-  Discovery of many rare low-mass dwarf stars
-  etc, etc!

## SDSS II: The Sequel

- SDSS I: april 2000 - june 2005
*completed*
- SDSS II: july 2005 - july 2008

## SDSS collaboration

**	**

**	****Korean Scientist Group**
**	****LAMOST (China)**
**	****Los Alamos Nat. Lab**
**	****Max Planck Inst. Astron.**
**	****Max Planck Inst. Astrophy.**
**	****New Mexico State U.**
**	****Ohio State U.**
**	****U. Pittsburgh**
**	****U. Portsmouth**
**	****Princeton U.**
**	****US Naval Obs.**
**	****U. Washington**

**~150 scientists from**
**	****Am. Museum Nat. History**
**	****Astrophysical Inst. Potsdam**
**	****U. Basel**
**	****Cambridge U.**
**	****Case Western Reserve**
**	****U. Chicago**
**	****Drexel U.**
**	****Fermilab**
**	****Institute for Adv. Studies**
**	****Japanese Participation Grp**
**	****Johns Hopkins U.**
**	****JINA**
**	****Kavli Institute for Particle Astrophysics**
**	**

## SDSS II: components

-  **SDSS “legacy”**: complete the original imaging and spectroscopy survey
-  **SEGUE**: study the (dark matter) halo of the Milky Way
-  **Supernovae**: survey to discover ~200 SNe to probe the expansion history of the universe (dark energy)

## 1. SDSS “legacy”

-      Imaging is complete                               Spectroscopy on track
-           (gap filled)                                               (two years left)

## Slide 26

## Star streams

- X(kpc)

- Y(kpc)

- as probes
- of Dark Matter!
- density of F stars in a
- patch on the sky,
- color-coded by their
- brightness

## Star streams

- X(kpc)

- Y(kpc)

- Newly discovered 'orphan stream'!

- as probes
- of Dark Matter!
- density of F stars in a
- patch on the sky,
- color-coded by their
- brightness

## Star streams

- X(kpc)

- Y(kpc)

- Newly discovered 'orphan stream'!
- Fitting the orbit of this stream
- in 3-D can constrain the shape of
- the Dark Matter Halo surrounding
- our Milky Way Galaxy.
- Fit is consistent with a spherical halo

- as probes
- of Dark Matter!
- density of F stars in a
- patch on the sky,
- color-coded by their
- brightness

- Sun

- Galactic
- Center

## 3. Supernovae & Dark Energy

- Type Ia supernovae are standard(izable) candles.
- By measuring their brightness and cosmological redshift, we can trace the expansion rate & thus infer the make-up of the universe as a function of time.
- Initial SN experiments found surprisingly that the universe appears to be **speeding up**, fueled by gravitationally repulsive “**dark energy**”.

## 3. SDSS II Supernovae

*Astier '06*

- SDSS well-suited to finding SNe at *moderate redshifts* that are difficult for other experiments
- Build up **large (~200)** sample of well-observed supernovae to study dark energy and better understand the supernova population
- Study *systematics* which are increasingly important with larger samples

## Finding and measuring supernovae

- supernova

- subtraction artifact

- 1. Take an image
- 2. Take another image later
- 3. Subtract the two

**2.**

**1.**

**3.**

## Finding and measuring supernovae

- supernova

- subtraction artifact

- 1. Take an image
- 2. Take another image later
- 3. Subtract the two
- 4. Continue taking images to measure supernova “light curve”

**2.**

**1.**

**3.**

**4.**

## SDSS II first year

- supernova yield:
- 139
- spectroscopically
- confirmed Type Ia
- Supernovae
- from the
- Fall 2005
- Season
- Analysis is
- underway
- 2 more years to go!

## Future projects

- 1. **Dark Energy Survey**
*first light: 2009*
- 2. **SNAP**
*first light:~2015*

## Dark Energy Survey

- What is Dark Energy?
- Cosmological constant?
- Scalar field?
- Modification to gravity?
- Carry out a “photometric” redshift survey to study Dark Energy with** 4 complementary techniques**
- Observe **5000 deg****2** in 4 broadbands, in Southern hemisphere to overlap with CMB observations by South Pole Telescope
- Requires a new 62 CCD camera (much larger than any current instrument)

## Four probes of Dark Energy

- 1. Weak gravitational lensing

- 2. Baryonic Acoustic Oscillations

*WMAP team*

*Eisenstein et al*

*Jain*

*Joffre et al*

- 3. Cluster
- counts

- 4. Supernovae

*Mohr*

## Measuring Dark Energy with DES

**Complementary probes:**
- sensitivity to cosmological parameters
- systematic errors
- measures of physics
- geometric probes
- growth of structure

- predicted DES constraints on the equation of state of dark energy,
*w*, and its evolution

**By the numbers:**
-  300 million galaxies (WL, BAO)
-  10,000 clusters
-  2,000 supernovae

- w(z)=w0+wa(1-a)

## The Dark Energy Camera 

- The Dark Energy Camera

- Full depletion CCDs
- Very large focal plane
- Readout: 17s readout time, 10 e- noise
- 0.6mx0.6m glass filters: g,r,i,z
- 5 element optical corrector

- CTIO Blanco 4m telescope, operated by NOAO for the NSF

- Focal plane:
- 62 2k x 4k Image CCDs (*520 Mpixels*)
- 8   2k x 2k Guide, focus, alignment CCDs

## The DES Collaboration

- Fermilab: J. Annis, H. T. Diehl, S. Dodelson, J. Estrada, B. Flaugher, J. Frieman, S. Kent, H. Lin, K. W. Merritt, J. Peoples, V. Scarpine, A. Stebbins,
- C. Stoughton, D. Tucker, W. Wester
- University of Illinois at Urbana-Champaign: C. Beldica, R. Brunner, I. Karliner, J. Mohr, R. Plante, P. Ricker, M. Selen, J. Thaler
- University of Chicago:** **J. Carlstrom, S. Dodelson, J. Frieman, M. Gladders,
- W. Hu, S. Kent, E. Sheldon, R. Wechsler
- Lawrence Berkeley National Lab: G. Aldering, N. Roe, C. Bebek, M. Levi,
- S. Perlmutter
- NOAO/CTIO: T. Abbott, C. Miller, C. Smith, N. Suntzeff, A. Walker
- Institut d'Estudis Espacials de Catalunya: F. Castander, P. Fosalba, E. Gaztañaga, J. Miralda-Escude
- Institut de Fisica d'Altes Energies: E. Fernández, M. Martínez
- University College London: O. Lahav, P. Doel, M. Barlow, S. Bridle, D. Brooks, S. Viti, S. Worswick, J. Weller
- University of Cambridge: G. Efstathiou, R. McMahon, W. Sutherland
- University of Edinburgh: J. Peacock
- University of Portsmouth: R. Nichol
- University of Michigan: R. Bernstein, B. Bigelow, M. Campbell, A. Evrard,
-  D. Gerdes, T. McKay, M. Schubnell, G. Tarle, M. Tecchio
- Ciemat Madrid: C. Mana, M. Molla, E. Sanchez    UAM Madrid: J. Garcia-Bellido

## SNAP: Supernova Acceleration Probe

- High precision cosmology from dedicated space-based telescope
- measurements of ~3000 supernovae to z=1.7
- weak lensing
- 9 filters, spanning 0.3-1.7 um
- Spectrograph + Imager containing CCD and IR detectors for a total of ~600 million pixels

- LBNL, UC Berkeley, CalTech, FNAL, Indiana U, IN2P3/INSU (France),  JPL, LAM (France), U Michigan, U Penn, U Stockholm, STScI, Yale

## SNAP at Fermilab

**Electronics**
- Fermilab regulator IC (ASIC)
- signal processing for IR chips, template/voltage control
- Mass memory
- flash for storage, FPGA for control, radiation damage testing
**Simulations**
- Pixel-level image simulations
**Calibration**
- Establish/observe SNAP photometric standard stars
**CCD testing & packaging**
**Cosmic Ray Shield**
**Photo-z for Weak Lensing**

## Summary

- Fermilab is engaged in a variety of exciting observational astrophysics and cosmology projects
- SDSS is the world leader in studies of large scale structure of the universe (and many other fields of astronomy)
- SDSS-II will enhance our understanding of two of the today's greatest mysteries in cosmology:
-  **Dark Matter** and **Dark Energy**
- In the future, DES and SNAP will provide precise constraints on the nature of Dark Energy