The Physical Structure of Galaxies at z ~ 2 - 3

David R. LawHubble Fellow, UCLA

The Physical Structure ofGalaxies at z ~ 2 - 3

The Physical Structure ofGalaxies at z ~ 2 - 3

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Galaxies in the Distant Universe: Ringberg Castle May 17, 2010

SummarySummary

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

What are the spatially resolved properties of z~2-3 galaxies?

Redshift distribution of the galaxysample (Steidel et al. 2004)

Introduction: The Optical Galaxy Sample

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 fieldsExtensive 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

Color selection method (Steidel et al. 2004)

OSIRIS Survey: Observing LogOSIRIS Survey: Observing LogName Redshift Time

Q0449-BX93 2.0067 4h 30m

Q1217-BX95 2.4246 1h 45m

HDF-BX1564 2.2228 1h

Q1623-BX453 2.1820 2h 30m

Q1623-BX455 2.4079 1h 30m

Q1623-BX502 2.1557 2h 45m

Q1623-BX543 2.5207 3h 15m

Q1700-BX490 2.3957 3h 15m

Q1700-BX710 2.2947 1h 30m

Q1700-BX763 2.2920 3h 30m

DSF2237a-C2 3.3172 1h 30m

Q2343-BX418 2.3050 1h 45m

Q2343-BX513 2.1082 3h 30m

Q2343-BX587 2.2430 1h 30m

Q2343-BX660 2.1739 3h

18 nights total, ~ 7 nights good conditionsResults 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.)

Results: Low v/ sourcesResults: Low v/ sources

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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

Results: Low v/ sourcesResults: Low v/ sources

Star forming regions compact (r < 2 kpc)

High velocity dispersion in all galaxies

~ 70 - 90 km/sGenuine dispersion, not unresolved gradients

Coherent shear in 4 sources

V/ ~ 1Often 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).

Stellar mass vs. velocity shear (Law 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

Kinematics are tied to mass/gas fraction

Kinematics are tied to mass/gas fraction

Stellar mass vs. H radius (Förster-Schreiber et al. 2009)

Testing sensitivity threshold with NIFS

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.

Rest-optical HST imaging programRest-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.

HST imaging: morphologiesHST imaging: morphologies

Morphologies generally similar to previous rest-UV studiesMultiple nuclei, clumps, chains, non-nucleated featuresCompare Q1700 field to previous ACS imaging (Cycle 15, PI: Shapley)

Postage stamps of galaxies at z=1.5 - 3.4 (3’’ squares)

ACS WFC3 ACS WFC3

ACS WFC3M* M*

M*

HST imaging: mass-size relationHST imaging: mass-size relationACS/F814W: Rest-frame 2700/2000 Å at z=2/3WFC3/F160W: Rest-frame 5100/3900 Å at z=2/3

5.0e9

9.0e10

2.4e10

1.4e9

HST imaging: mass-size relationHST imaging: mass-size relation

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

Color-radius and mass-radius relation for z ~ 2-3 star forming galaxies. (Red: z>2.5, Blue: z<1.9)

SummarySummary

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

What are the spatially resolved properties of z~2-3 galaxies?