1. Cosmology with the 21 cm Transition Steve Furlanetto Yale University September 25, 2006 Steve Furlanetto Yale University September 25, 2006

2. Outline The 21 cm transition The Dark Ages First Light Reionization Measuring the Matter Power Spectrum Summary The 21 cm transition The Dark Ages First Light Reionization Measuring the Matter Power Spectrum Summary See our Physics Reports review (Furlanetto, Oh, & Briggs 2006, astro- ph/0608032) for more information!

3. The 21 cm Transition Map emission (or absorption) from IGM gas Dark Ages: only probe! Spectral line: measure entire history Direct measurement of IGM properties Map emission (or absorption) from IGM gas Dark Ages: only probe! Spectral line: measure entire history Direct measurement of IGM properties SF, AS, LH (2004)

4. The Spin Temperature In the absence of coupling mechanisms, T S =T CMB Collisions couple T S to T K Efficient when  > 15 [10/(1+z)] 2 if relatively hot Dominated by electron exchange in H-H collisions in neutral medium (Zygelman 2005), or H-e - collisions in partially ionized medium (Furlanetto & Furlanetto 2006) The Wouthuysen-Field Effect Pump triplet state with absorption/re-emission of Ly  photons Becomes effective when ~0.1 Ly  photon/baryon In the absence of coupling mechanisms, T S =T CMB Collisions couple T S to T K Efficient when  > 15 [10/(1+z)] 2 if relatively hot Dominated by electron exchange in H-H collisions in neutral medium (Zygelman 2005), or H-e - collisions in partially ionized medium (Furlanetto & Furlanetto 2006) The Wouthuysen-Field Effect Pump triplet state with absorption/re-emission of Ly  photons Becomes effective when ~0.1 Ly  photon/baryon

5. Observing the Signal The Challenges Terrestrial radio frequency interference Ionospheric “seeing” Foregrounds Instrumental issues (polarization leakage, sidelobe control,…) Noise so large, imaging extremely difficult! LOFAR

6. Error Estimates: z=8 Survey parameters z=8 T sys =440 K t int =1000 hr B=6 MHz No systematics! MWA (solid black) A eff =7000 m 2 1.5 km core SKA (dotted blue) A eff =1 km 2 5 km core MWA SKA Foreground limit after McQuinn et al. (2005)

7. Error Estimates: z=12 Survey parameters z=12 T sys =1000 K t int =1000 hr B=6 MHz No systematics! MWA (solid black) A eff =9000 m 2 1.5 km core SKA (dotted blue) A eff =1 km 2 5 km core MWA SKA Foreground limit

8. The Global Signal: The Dark Ages Straightforward physics Fluctuations directly trace matter power spectrum (Loeb & Zaldarriaga 2004) 3D dataset Small-scale power SF, PO, FB (2006)

9. The Dark Ages: Dark Matter Decay SF, PO, EP (2006) Dark matter decay models  ~10 16 yr  ~10 19 yr Standard calculation

10. The Global Signal: First Light First stars (quasars?) flood Universe with photons Heating W-F effect Ionization Timing depends on f *, f esc, f X, stellar population First stars (quasars?) flood Universe with photons Heating W-F effect Ionization Timing depends on f *, f esc, f X, stellar population Pop II Stars SF (2006) feedback weak X-rays

11. The Ly  and Heating Eras Ly  photons create fluctuations around first sources (Barkana & Loeb 2004, Pritchard & Furlanetto 2006) X-rays seed fluctuations in T S (and hence  T b ) Discrete (biased) sources and 1/r 2 flux Soft X-rays have shorter mean free paths Rapid structure formation Pritchard & Furlanetto (2006)

12. 21 cm Observations: Reionization z=18.3 13 Mpc comoving  =0.1 MHz SF, AS, LH (2004)

13. z=16.1  =0.1 MHz 13 Mpc comoving SF, AS, LH (2004) 21 cm Observations: Reionization

14. z=14.5  =0.1 MHz 13 Mpc comoving SF, AS, LH (2004) 21 cm Observations: Reionization

15. z=13.2  =0.1 MHz 13 Mpc comoving SF, AS, LH (2004) 21 cm Observations: Reionization

16. z=12.1  =0.1 MHz 13 Mpc comoving SF, AS, LH (2004) 21 cm Observations: Reionization

17. z=11.2  =0.1 MHz 13 Mpc comoving SF, AS, LH (2004) 21 cm Observations: Reionization

18. z=10.4  =0.1 MHz 13 Mpc comoving SF, AS, LH (2004) 21 cm Observations: Reionization

19. z=9.8  =0.1 MHz 13 Mpc comoving SF, AS, LH (2004) 21 cm Observations: Reionization

20. z=9.2  =0.1 MHz 13 Mpc comoving SF, AS, LH (2004) 21 cm Observations: Reionization

21. z=8.7  =0.1 MHz 13 Mpc comoving SF, AS, LH (2004) 21 cm Observations: Reionization

22. z=8.3  =0.1 MHz 13 Mpc comoving SF, AS, LH (2004) 21 cm Observations: Reionization

23. z=7.9  =0.1 MHz 13 Mpc comoving SF, AS, LH (2004) 21 cm Observations: Reionization

24. z=7.5  =0.1 MHz 13 Mpc comoving SF, AS, LH (2004) 21 cm Observations: Reionization

25. z=9.2  =0.1 MHz 13 Mpc comoving SF, AS, LH (2004) 21 cm Observations: Reionization

26. The Power Spectrum Rich set of information from bubble distribution: Timing: growth of structure Underlying source population (SF, MM, LH 2005) Uniform ionizing component (SF, MZ, LH 2004b) Feedback (SF, MZ, LH 2004b) Correlation with density field (SF, MZ, LH 2004b) Also must consider higher- order statistics! Rich set of information from bubble distribution: Timing: growth of structure Underlying source population (SF, MM, LH 2005) Uniform ionizing component (SF, MZ, LH 2004b) Feedback (SF, MZ, LH 2004b) Correlation with density field (SF, MZ, LH 2004b) Also must consider higher- order statistics! x i =0.78 z=10 x i =0.13 x i =0.36 x i =0.48 x i =0.59 x i =0.69

27. Fundamental Cosmology? Probably a period where density dominates before reionization: measure matter power spectrum Modest improvements to small scales (neutrinos, tilt, etc.; McQuinn et al. 2005, Bowman et al. 2005) Redshift space distortions Anisotropic: can extract matter power spectrum (Bharadwaj & Ali 2004, Barkana & Loeb 2004) Probably a period where density dominates before reionization: measure matter power spectrum Modest improvements to small scales (neutrinos, tilt, etc.; McQuinn et al. 2005, Bowman et al. 2005) Redshift space distortions Anisotropic: can extract matter power spectrum (Bharadwaj & Ali 2004, Barkana & Loeb 2004) SF (2006)

28. Anisotropic Power Spectrum: Error Estimates at z=8 Survey parameters z=8 T sys =440 K t int =1000 hr B=6 MHz No systematics! MWA (solid black) A eff =7000 m 2 1.5 km core SKA (dotted blue) A eff =1 km 2 5 km core MWA SKA Foreground limit after McQuinn et al. (2005)

29. Conclusions The 21 cm line is a unique probe of the high-redshift universe Reionization: measures distribution of ionized gas and its relation to sources, at every redshift First Light: measures the impact of these sources on their environment Dark Ages: “clean” probe of cosmology and of exotic processes like dark matter decay The 21 cm line is a unique probe of the high-redshift universe Reionization: measures distribution of ionized gas and its relation to sources, at every redshift First Light: measures the impact of these sources on their environment Dark Ages: “clean” probe of cosmology and of exotic processes like dark matter decay See our Physics Reports review (Furlanetto, Oh, & Briggs 2006, astro- ph/0608032) for more information!