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
Galaxy formation and evolution How did galaxies like the Milky Way form? Using the early universe to see it happening (http://zebu.uoregon.edu/images) M31
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?
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)
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)
Unresolved line flux sensitivity estimates (10,000 seconds, high-order AO, R=3000)
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
High-mass mergers are frequent at high redshift 2-2.4 µm m is Dz z ~ 1 Plot by Joel Berrier; Models in Berrier et al. (2005); Zentner et al. 2004
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
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
Cluster detections throughout K 20-meter 30-meter
Cluster detections throughout K 50-meter 100-meter
Can we use the clusters to measure, say, a velocity dispersion? 30-meter 100-meter
A 20-meter isn t t big enough at z~5
z~5 Antennae star cluster velocity dispersion measurements
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.)
Role of Adaptive Optics Diffraction limit at 1.2 microns: (arcsec) z=3 z=5 z=7 8-meter 0.038 290 pc 240 pc 200 pc 20-meter 0.015 120 pc 95 pc 80 pc 30-meter 0.010 78 pc 63 pc 53 pc 50-meter 0.006 47 pc 38 pc 32 pc 100- meter 0.003 23 pc 19 pc 16 pc
Hints of internal structure at high redshift HST/WFPC2 HST/NICMOS colors color/age variation inside high-z galaxies Figure from Casey Papovich
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.).
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
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
Bright star-forming regions 30 Dor (LMC): even central region resolved for D > 30 Really only compact star clusters that remain unresolved 60 pc
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
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
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 = 0.1-0.8 from Santos (2003)]
Two favorable scenarios optimistic : Top-heavy IMF with only 300-1000 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)
Two favorable scenarios plausible : Top-heavy IMF with Salpeter slope but only 50-500 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 1-500 or 1-100 solar masses
Lyman α Luminosity Function 8m 30+ hrs 30+ hrs Models: Barton et al. (2004) Data: various sources compiled in Santos et al. (2004)
Simulation: heavy Salpeter IMF Adapted models from Barton et al. (2004) z=8.227 8 hours 100-m telescope
Simulation: Salpeter IMF Adapted models from Barton et al. (2004) z=8.227 8 hours 100-m telescope
Simulation: Salpeter IMF Adapted models from Barton et al. (2004) z=8.227 8 hours 50-m telescope
Simulation: Salpeter IMF Adapted models from Barton et al. (2004) z=8.227 8 hours 30-m telescope
Weighing z=10 stars HeII (λ1640( Å) Salpeter 1-500 M Zero metallicity HeII (λ1640( Å) Heavy stars Simulation through 30m telescope, 8 hours, R=3000
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)
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.