Galaxy Formation and Evolution: Observing High-Redshift Galaxies with Large-Aperture Telescopes

1. The Birth and Assembly of Galaxies: the Relationship Between Science Capabilities and Telescope Aperture Betsy Barton Center for Cosmology University of California, Irvine Grateful acknowledgements to: J.-D. Smith,Casey Papovich, Romeel Davé, Jean Brodie, Bev Oke, Brad Whitmore, Rob Kennicutt

2. Galaxy formation and evolution How did galaxies like the Milky Way form? • Using the early universe to “see” it happening M31 (http://zebu.uoregon.edu/images)

3. Galaxy evolution • When and how did the build-up of galaxies occur? • Internal variations in kinematics, metallicity, star formation history to z~5 (and beyond) • Where and when did the first stars form? • When did “first light” happen? • When and how was the universe reionized? • Can we find Pop III star formation?

4. Detailed internal properties of high-redshift galaxies • Science goals: • Dynamical masses • Enrichment and star formation history as a function of position • Direct observations of the build-up of mass through merging (z=3 galaxy from Hubble Deep Field; HST psf ~ 0.1” ~ 770 pc)

5. Near-IR case: for chemical abundances, star formation histories weak absorption Lines in the optical and near-infrared [OII] to z > 5 Ha to z = 3 L/M optical • Few strong lines in optical • between redshifts of • about 1 to 3 • NEED near-IR K H J Plot from Oke & Barton (2000)

6. Unresolved line flux sensitivity estimates (10,000 seconds, high-order AO, R=3000)

7. Kinematics of Lyman break galaxies • At R < 25, ~3-4 LBGs per square arcminute at 2.5 < z < 3.5; ~1 at z > 3.5

8. High-mass mergers are frequent at high redshift 2-2.4 m is z ~ 1 Plot by Joel Berrier; Models in Berrier et al. (2005); Zentner et al. 2004

9. Galaxy evolution at very high redshifts: watching merging in action • The Antennae simulation: a luminous, lumpy local starburst 8-meter 20-meter 30-meter 8 hours sec. with large- aperture telescope, z=4.74 Individual star-forming regions are visible in emission lines at high redshifts with large-aperture telescopes

10. Galaxy evolution at very high redshifts: watching merging in action • The Antennae simulation: a luminous, lumpy local starburst 30-meter 50-meter 100-meter 8 hours sec. with large- aperture telescope, z=4.74 Individual star-forming regions are visible in emission lines at high redshifts with large-aperture telescopes

11. Cluster detections throughout K 20-meter 30-meter

12. Cluster detections throughout K 50-meter 100-meter

13. Can we use the clusters to measure, say, a velocity dispersion? 30-meter 100-meter

14. A 20-meter isn’t big enough at z~5

15. z~5 Antennae star cluster velocity dispersion measurements

16. z~3 (H-band) is a better regime for a 20-m z=3.34 z=4.74 (However, H-band not as open w.r.t. night-sky lines.)

17. Role of Adaptive Optics • Diffraction limit at 1.2 microns: (arcsec) z=3 z=5 z=7

18. Hints of internal structure at high redshift HST/WFPC2 HST/NICMOS colors color/age variation inside high-z galaxies Figure from Casey Papovich

19. Summary of High-z Galaxy Internal Emission-line Measurements • If forming star clusters ubiquitous, like Antennae, then 30-meter can measure kinematics (and SFR) to z~5. • Main gain of > 30-meter is in coverage throughout redshift range (limited utility). • Beyond K-band (z=5.4), a mid-IR optimized 100-meter might be able to follow [OII] to higher redshifts; greatly depends on thermal properties of telescope. • Improvement may come from continuum sensitivity (light bucket). • High-order AO of limited for D > 50 meters; only unresolved objects are small star clusters (and individual stars, SN, etc.).

20. First Light • Hydrodynamic simulations of Davé, Katz, & Weinberg • Lyman  cooling radiation (green) • Light in Ly from forming stars (red, yellow) z=10 z=8 z=6

21. Diffraction Limits • Diffraction limit at Lyman : z=7

22. Bright star-forming regions • 30 Dor (LMC): even central region resolved for D > 30 • Really only compact star clusters that remain unresolved 60 pc

23. Le Delliou et al. Lyman  source sizesfrom a semi-analytic model All but 8-meter resolve almost all predicted galaxies from Le Delliou et al. (2005) at diffraction limit. z=7 8-meter (Hydro simulations don’t resolve.) 20-meter 30-meter 50-meter 100-meter: -1.74

24. Physical elements of star formation beyond reionization star formation rate partially neutral IGM (above z ~ 6.2) stellar initial mass function { { escape of ionizing and Lya photons penetration through intergalactic medium

25. The IMF, the ISM, and the IGM Recent theoretical work favorable to Lya detection: • IMF: low-metallicity gas leads to top-heavy IMF • Abel et al. (2000)[how fast do you enrich?] • Top-heavy to explain WMAP results (e.g., Cen 2003a,b) • IGM: Ly can escape if bubble of IGM ionized locally; winds help (Haiman 2002; Santos 2003) • ISM: fesc high for WMAP(Cen 2003a,b) • good for ionizing IGM locally • lower fraction good for number of photons converted to Lya [peak ~ fesc = 0.1-0.8 from Santos (2003)]

26. Two favorable scenarios • “optimistic”: • Top-heavy IMF with only 300-1000 solar mass stars • no metals • fesc=0.35 (fraction of ionizing photons that escape from the galaxy; Ly flux is proportional to 1-fesc) • no dust • fIGM = 1 (fraction of Ly photons that hit the IGM and still get to us)

27. Two favorable scenarios • “plausible”: • Top-heavy IMF with Salpeter slope but only 50-500 solar mass stars • no metals • fesc=0.1 (fraction of ionizing photons that escape from the galaxy; Lya flux is proportional to 1-fesc) • no dust • fIGM = 0.25 (fraction of Lya photons that hit the IGM and still get to us) • “heavy Salpeter”/”Salpeter”: • Same as “plausible” but over 1-500 or 1-100 solar masses

28. Lyman  Luminosity Function 8m 30+ hrs Models: Barton et al. (2004) Data: various sources compiled in Santos et al. (2004)

29. Simulation: heavy Salpeter IMF Adapted models from Barton et al. (2004) z=8.227 8 hours 100-m telescope

30. Simulation: Salpeter IMF Adapted models from Barton et al. (2004) z=8.227 8 hours 100-m telescope

31. Simulation: Salpeter IMF Adapted models from Barton et al. (2004) z=8.227 8 hours 50-m telescope

32. Simulation: Salpeter IMF Adapted models from Barton et al. (2004) z=8.227 8 hours 30-m telescope

33. Weighing z=10 stars HeII (1640 Å) Salpeter 1-500 M Zero metallicity HeII (1640 Å) Heavy stars Simulation through 30m telescope, 8 hours, R=3000

34. First Light in the Near IR • Discovery of z > 7 objects: probably done with JWST • Larger ground-based telescopes will • Map reionization in Lyman  • Measure Lyman  line profiles • Look for HeII(1640) as indicator of Pop III star formation • Advantages for > 30-meter aperture: • Needed sensitivity when IGM nearly impenetrable (completely unknown; penetration is the interesting quantity for topology of reionization) • Needed sensitivity when HeII weak (but this is not Pop III anyway)

35. What is beyond a 30-meter telescope? • Older or lower-surface-brightness stars and star formation at z > 2; dwarf galaxies at z > 2 • Faint emission lines and absorption lines at z > 5-6; lines in the mid-IR • Extremely high-z star formation with normal IMF (if it exists) • Upcoming WMAP data release may tell us how high we have to go in z These are issues for “down the road”; a 30-m can address many of the questions we have now.