The Birth and Assembly of Galaxies: the Relationship Between Science Capabilities and Telescope Aperture

Transcription

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

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 optical L/M J H K [OII] to z > 5 Ha to z = 3 Few strong lines in optical between redshifts of about 1 to 3 NEED near-ir 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 µm m is Dz 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 largeaperture 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 largeaperture 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 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=4.74 z=3.34 (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 8-meter pc 240 pc 200 pc 20-meter pc 95 pc 80 pc 30-meter pc 63 pc 53 pc 50-meter pc 38 pc 32 pc 100- meter pc 19 pc 16 pc

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( 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 α cooling radiation (green( green) Light in Lyα from forming stars (red( red,, yellow) z=10 z=8 z=6

21 Diffraction Limits Diffraction limit at Lyman α: z=7 8-meter 160 pc 20-meter 64 pc 30-meter 43 pc 50-meter 100- meter 25 pc 13 pc

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 α source sizes from a semi-analytic model z=7 All but 8-meter resolve almost all predicted galaxies from Le Delliou et al. (2005) at diffraction limit. 8-meter 20-meter 30-meter 50-meter (Hydro simulations don t t resolve.) 100-meter: -1.74

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

25 The IMF, the ISM, and the IGM Recent theoretical work favorable to Lyα 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: Lyα can escape if bubble of IGM ionized locally; winds help (Haiman 2002; Santos 2003) ISM: f esc high for WMAP (Cen 2003a,b) good for ionizing IGM locally lower fraction good for number of photons converted to Lyα [peak ~ f esc = from Santos (2003)]

26 Two favorable scenarios optimistic : Top-heavy IMF with only solar mass stars no metals f esc =0.35 (fraction of ionizing photons that escape from the galaxy; Lyα flux is proportional to 1-f esc ) no dust f IGM = 1 (fraction of Lyα photons that hit the IGM and still get to us)

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

28 Lyman α Luminosity Function 8m 30+ hrs 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= hours 100-m telescope

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

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

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

33 Weighing z=10 stars HeII (λ1640( Å) Salpeter M Zero metallicity HeII (λ1640( 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 α Measure Lyman α 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.