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The Physical Structure of Galaxies at z ~ 2 - 3

The Physical Structure of Galaxies at z ~ 2 - 3. David R. Law Hubble Fellow, UCLA. John McDonald, CFHT. Galaxies in the Distant Universe: Ringberg Castle May 17, 2010. Summary.

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The Physical Structure of Galaxies at z ~ 2 - 3

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  1. The Physical Structure ofGalaxies at z ~ 2 - 3 David R. Law Hubble Fellow, UCLA John McDonald, CFHT Galaxies in the Distant Universe: Ringberg Castle May 17, 2010

  2. Summary What are the spatially resolved properties of z~2-3 galaxies? • Star-forming galaxies have globally high  • Galaxies with M* < 1010 M have little velocity shear • Galaxies with M* > 1010 M show more pronounced shear • Rest UV/optical morphologies similar for low M*, differ over 1010 M* • Strong mass-radius relation

  3. Introduction: The Optical Galaxy Sample • Optically-selected by color, confirmed by rest-UV spectra (e.g. Steidel et al. 2004) • ~1500 spec. redshifts in ~ 10 fields • Extensive photometric/spectroscopic data, NIR H survey (120+ galaxies; Erb et al. 2006) Broad Physical Properties: • Rapidly starforming: SFR ~ 30 M/year, energetic outflows • High gas fraction: Mgas/M* = 2.1/3.6 x 1010 M • Clustering statistics  halo mass 1011.8 - 1012.2 M Redshift distribution of the galaxy sample (Steidel et al. 2004) Color selection method (Steidel et al. 2004)

  4. OSIRIS Survey: Observing Log • 18 nights total, ~ 7 nights good conditions • Results published in Law et al. (2007, 2009), see also Wright et al. (2007, 2009) • 24 galaxies observed, 15 detected, 13 high-quality. • Varied selection criteria (H bright, high/low M*, NIRSPEC kinematics, etc.)

  5. Results: Low v/ sources 7/13: No significant resolved velocity structure v/ ~ 0.5 3/13: Measurable resolved velocity shear v/ ~ 1 3/13: Multiple components, some with shear, some without

  6. Results: Low v/ sources • Star forming regions compact (r < 2 kpc) • High velocity dispersion in all galaxies •  ~ 70 - 90 km/s • Genuine dispersion, not unresolved gradients • Coherent shear in 4 sources • V/ ~ 1 • Often inconsistent with simple rotation models • Generally don’t look like smooth rotating disks 1-d velocity curves along kinematic major axis for 13 OSIRIS galaxies. Black points represent velocities, red velocity dispersion (Law et al. 2009).

  7. Kinematics are tied to mass/gas fraction Stellar mass vs. velocity shear (Law et al. 2009) Stellar mass vs. H radius (Förster-Schreiber et al. 2009) • Galaxies with velocity shear have significantly greater stellar mass • Low-mass galaxies more likely to be dynamically dominated by gas. • High-mass galaxies more likely to show rotation. See, e.g., N. Forster-Schreiber

  8. Testing sensitivity threshold with NIFS Difference in sensitivity: • OSIRIS observations optimized for angular resolution, comparatively shallow • Look for low surface brightness emission around OSIRIS sample using deep Gemini/NIFS observations (2010a: Glazebrook/Abraham/Law/McDermid). • 45 hours total, 8-10 hours on each object from the OSIRIS sample. • Program ~ 66% complete, results coming soon. OSIRIS/NIFS Ha detections for GDDS-22-2172. Integration time 3 hours.

  9. Rest-optical HST imaging program • 42 orbit Cycle 17 HST WFC3/IR (F160W) imaging program. • GO-11694: D. Law (PI), C. Steidel, Sarah Nagy, A. Shapley • FWHM ~ 0.19’’ , limiting magnitude ~ 26.8 AB/arcsec2 • 50 galaxies in 2 fields to date • Full program >300 spec. confirmed z ~ 2-3 galaxies in 10 fields • Many with rest-optical long-slit or IFU (OSIRIS/SINFONI) spectroscopy HST WFC3/IR image of Q1700+64 field.

  10. HST imaging: morphologies Postage stamps of galaxies at z=1.5 - 3.4 (3’’ squares) • Morphologies generally similar to previous rest-UV studies • Multiple nuclei, clumps, chains, non-nucleated features • Compare Q1700 field to previous ACS imaging (Cycle 15, PI: Shapley)

  11. HST imaging: mass-size relation ACS/F814W: Rest-frame 2700/2000 Å at z=2/3 WFC3/F160W: Rest-frame 5100/3900 Å at z=2/3 ACS WFC3 ACS WFC3 M* ACS WFC3 M* 1.4e9 5.0e9 M* 9.0e10 2.4e10

  12. HST imaging: mass-size relation Color-radius and mass-radius relation for z ~ 2-3 star forming galaxies. (Red: z>2.5, Blue: z<1.9) • Strong relation between GALFIT effective radius Re and R-H color  strong relation between effective radius Re and stellar mass M* • Relation may persist over 2 decades in M* down to 109 M

  13. Summary What are the spatially resolved properties of z~2-3 galaxies? • Star-forming galaxies have globally high  • Galaxies with M* < 1010 M have little velocity shear • Galaxies with M* > 1010 M show more pronounced shear Recent Gemini/NIFS observations will test  limits • Rest UV/optical morphologies similar for low M*, differ over 1010 M • Strong mass-radius relation

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