Measurement of Dark Energy with Baryon Acoustic Oscillation (BAO)

1. Measurement of Dark Energy with Baryon Acoustic Oscillation (BAO) Thomas Stucky

2. Outline • Dark Energy (DE) Theoretical Framework • Measurement of DE • Theory of BAO • Modern BAO Measurements with BOSS • Future BAO Measurements

3. Outline • Dark Energy (DE) Theoretical Framework • Measurement of DE • Theory of BAO • Modern BAO Measurements with BOSS • Future BAO Measurements

4. History of Dark Energy (DE) • 1998, Type Ia supernovae observations lead Riesset al and Perlmutteret al to conclude the expansion of the universe to be accelerating. In other words: • Einstein’s cosmological constant models this acceleration. Riess, G. Adam, et al. “Observational Evidence from Supernovae for an Accelerating Universe and a Cosmological Constant.” The Astronomical Journal 116 (1998): 1009-1038. Print. Planck Collaboration. “Planck 2013 results. XVI. Cosmological parameters.” Astronomy & Astrophysics (2014). Web. 3

5. DE’s Importance to Physics DE may teach us: • New physics beyond general relativity. • New elementary particles. • New fundamental forces.

6. Cosmological Constant in the Friedmann Equation • For expansion to occur: • For the cosmological constant • Dark energy may act as a dynamical fluid, then is not constant. In which case . Dark Energy Task Force. “Report of The Dark Energy Task Force.” Astronomy And Astrophysics Advisory Committee, High Energy Physics Advisory Panel. n.d. Web.

7. Parameterization of DE’s Equation of State • Parameterization of dark energy’s equation of state: • Three possibilities: • , cosmological constant • , dynamical fluid • Inconsistencies between proper distance () and density fluctuations ( measurements indicate failure of G.R. Dark Energy Task Force. “Report of The Dark Energy Task Force.” Astronomy And Astrophysics Advisory Committee, High Energy Physics Advisory Panel. n.d. Web.

8. Two Different DE Measurements • Geometric: , , , Measures of proper distances • Growth: Measures of structure growth Dark Energy Task Force. “Report of The Dark Energy Task Force.” Astronomy And Astrophysics Advisory Committee, High Energy Physics Advisory Panel. n.d. Web.

9. Distance-Redshift & Growth-Redshift Plots Dark Energy Task Force. “Report of The Dark Energy Task Force.” Astronomy And Astrophysics Advisory Committee, High Energy Physics Advisory Panel. n.d. Web.

10. Outline • Dark Energy (DE) Theoretical Framework • Measurement of DE • Theory of BAO • Modern BAO Measurements with BOSS • Future BAO Measurements

11. Methods of DE Observation • Type-Ia Supernovae • Galaxy Clusters • Weak Gravitational Lensing • Baryon Acoustic Oscillations (BAO)

12. Type-Ia Supernovae • Using Type-Ia supernovae as standard candles. • Has detected the acceleration for • Measures Dark Energy Task Force. “Report of The Dark Energy Task Force.” Astronomy And Astrophysics Advisory Committee, High Energy Physics Advisory Panel. n.d. Web.

13. Galaxy Cluster • Galaxy clusters are the largest structures in the universe. • Counting of these clusters can produce predictions of a mass function. • Involves complex modeling of baryon interactions: high uncertainties. • Measures - and the growth-based - relation. Dark Energy Task Force. “Report of The Dark Energy Task Force.” Astronomy And Astrophysics Advisory Committee, High Energy Physics Advisory Panel. n.d.Web. http://www.redorbit.com/news/space/1112744091/galaxy-clusters-wise-mission-nasa-120712/

14. Weak Gravitational Lensing • Background galaxies are weakly lensed by foreground mass. • The lensing can be measured without the deflection angle by using a statistical bias known as cosmic shear. • Measures - and -. Dark Energy Task Force. “Report of The Dark Energy Task Force.” Astronomy And Astrophysics Advisory Committee, High Energy Physics Advisory Panel. n.d. Web.

15. Baryon Acoustic Oscillations • Using the BAO sounds horizon as a standard ruler. • Galaxy distribution field can be mapped to dark matter distribution field. • Measures -, - Dark Energy Task Force. “Report of The Dark Energy Task Force.” Astronomy And Astrophysics Advisory Committee, High Energy Physics Advisory Panel. n.d. Web. Feb. 2014. U.S. Dept. of Energy. “BOSS: the Baryon Oscillation Spectroscopic Survey.” U.S. Dept. of Energy. Web.

16. Outline • Dark Energy (DE) Theoretical Framework • Measurement of DE • Theory of BAO • Modern BAO Measurements with BOSS • Future BAO Measurements

17. BAO Refresher • Waves propagate at • Oscillations freeze out at recombination leaving behind density fluctuations. • Sound horizon () is the distance sound waves travel before recombination. Hu, Wayne. “Ringing in the New Cosmology.” University of Chicago. Web.

18. Evolution of BAO Ryden, Barbara. “Introduction to Cosmology.” Addison-Wesley (2003). Print.

19. BAO Animation Hu, Wayne. “Ringing in the New Cosmology.” University of Chicago. Web.

20. Measuring BAO – Fourier Transform Fourier Transform Fourier Transform

21. Measuring BAO – Power Spectrum

22. Outline • Dark Energy (DE) Theoretical Framework • Measurement of DE • Theory of BAO • Modern BAO Measurements with BOSS • Future BAO Measurements

23. Galaxy Redshift Surveys • Survey a large chunk of galaxy redshifts. • Map galaxy distribution to the density function. • Density function gives and . BOSS using SDSS performs surveys of this type. Siegel, Ethan. “Dark Matter: We don’t understand everything.” ScienceBlogs (2010): 26 March. Web.

24. Sloan Digital Sky Survey (SDSS) • 2.5m Ritchey-Chretien altitude-azimuth telescope. • Located in Apache Point Observatory, New Mexico. • 30 CCDs with 2048x2048 pixels each. • Angular resolution: 0.396 arc seconds/pixel U.S. Dept. of Energy. “BOSS: the Baryon Oscillation Spectroscopic Survey.” U.S. Dept. of Energy. Web. 4 Apr. 2014.

25. Baryon Oscillation Spectroscopic Survey (BOSS) • Galaxy and quasar redshift survey using SDSS. • 1.5 million galaxies were selected for spectroscopy from SDSS-I/II data. • Ly-α forest spectra of 160,000 quasars were taken. Eisenstein, Daniel J. et al. “SDSS-III: Massive Spectroscopic Surveys of the Distant Universe, the Milky Way Galaxy, and Extra-Solar Planetary Systems.” arXiv(2011): 17 Aug. Web.

26. BOSS Galaxy Selection Eisenstein, Daniel J. et al. “SDSS-III: Massive Spectroscopic Surveys of the Distant Universe, the Milky Way Galaxy, and Extra-Solar Planetary Systems.” arXiv(2011): 17 Aug. Web.

27. BOSS Spectrograph • Spectra of quasars and galaxies are taken. • Precisely drilled aluminum plates hold fiber optics. • Fibers connect to a dual-channel spectrograph allows for 1000 spectra. Eisenstein, Daniel J. et al. “SDSS-III: Massive Spectroscopic Surveys of the Distant Universe, the Milky Way Galaxy, and Extra-Solar Planetary Systems.” arXiv(2011): 17 Aug. Web.

28. BOSS Data Coverage Eisenstein, Daniel J. et al. “SDSS-III: Massive Spectroscopic Surveys of the Distant Universe, the Milky Way Galaxy, and Extra-Solar Planetary Systems.” arXiv(2011): 17 Aug. Web.

29. Example of BOSS Galaxy and Quasar Spectra

30. BOSS DS11 Data

31. BOSS Conclusions • Measurements are in excellent agreement with the ΛCDM model. • Agreement with a dark energy as a cosmological constant ( is constant in space and time). • G.R. still holds.

32. Outline • Dark Energy (DE) Theoretical Framework • Measurement of DE • Theory of BAO • Modern BAO Measurements with BOSS • Future BAO Measurements

33. Future DE Measurements with BAO • Dark Energy Spectroscopic Instrument (DESI) • Large Synoptic Survey Telescope (LSST) • Square Kilometer Array (SKA)

34. Dark Energy Spectroscopic Instrument (DESI) • Will construct a 3D map of tens of millions of galaxies and quasars. • Will use a 4m telescope at Kitt Peak National Observatory. • Due by 2018. http://desi.lbl.gov/

35. Large Synoptic Survey Telescope (LSST) • 8.4m telescope with a 3200 megapixel camera. • Will scan 20,000 deg2 several times per month in 6 distinct bands. • Observes in range of 0.5<z<3. • Will also study supernovae and weak-lensing. Dark Energy Task Force. “Report of The Dark Energy Task Force.” Astronomy And Astrophysics Advisory Committee, High Energy Physics Advisory Panel. n.d. Web. Feb. 2014. http://www.lsst.org/lsst/

36. Square Kilometer Array (SKA) • Radio interferometer array • Sensitive to 100MHz – 25 GHz. • Will survey neutral hydrogen of 109 galaxies. Dark Energy Task Force. “Report of The Dark Energy Task Force.” Astronomy And Astrophysics Advisory Committee, High Energy Physics Advisory Panel. n.d. Web. Feb. 2014. https://www.skatelescope.org/

37. Questions?

38. References • Dark Energy Task Force. “Report of The Dark Energy Task Force.” Astronomy And Astrophysics Advisory Committee, High Energy Physics Advisory Panel. n.d.Web. • Riess, G. Adam, et al. “Observational Evidence from Supernovae for an Accelerating Universe and a Cosmological Constant.” The Astronomical Journal 116 (1998): 1009-1038. Print. • Planck Collaboration. “Planck 2013 results. XVI. Cosmological parameters.” Astronomy & Astrophysics(2014). Web. • SDSS Data Release 7. Sloan Digital Sky Survey, 19 Mar. 2003. Web. • Ryden, Barbara. “Introduction to Cosmology.” Addison-Wesley (2003). Print. • U.S. Dept. of Energy. “BOSS: the Baryon Oscillation Spectroscopic Survey.” U.S. Dept. of Energy. Web. • Hu, Wayne. “Ringing in the New Cosmology.” University of Chicago. Web. • Siegel, Ethan. “Dark Matter: We don’t understand everything.” ScienceBlogs (2010): 26 March. Web. • Eisenstein, Daniel J. et al. “SDSS-III: Massive Spectroscopic Surveys of the Distant Universe, the Milky Way Galaxy, and Extra-Solar Planetary Systems.” arXiv(2011): 17 Aug. Web.