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Dynamic and Spatial Properties of Satellitesin Isolated Galactic Systems
Abel B. Diaz
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Presentation Outline
• Rotation Curves: Probing the mass distribution• The Problem• Rotation Curves of Isolated Galaxy Systems• Stellar properties of Satellites• The Holmberg effect• 2D Rotation Curve
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Rotation Curves:Probing the mass distribution
• Within Galaxy– Well known
• External to Galaxy– Not well known
Fritz Zwicky (1933)Babcock (1939)&Vera Rubin (1970)
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The Problem
• How does the mass distribution of galaxies change with distance beyond the disk of the galaxy?
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What would this tell us?
• Learning more about the mass distribution of isolated galaxies may provide insight into galaxy– formation – evolution– LSS
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So how can this be done?
• Rotation Curves of Isolated Galaxy Systems– Dominate source of gravitation
• The center-of-mass of the system is located at center of “primary” galaxy
– Satellites relatively small compared to primary• Maintains center-of-mass located at the center of
primary
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Limits on Isolated Galaxies
1. Small number of detectable satellites
2. Line-of-sight velocity
3. Projected distance
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Isolated Galaxy Ensembles
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Interlopers
• Observed redshift = cosmological redshift + Doppler redshift• The peculiar velocities of the satellites can be on the order of
400km/s• Uncertainty of distance along the line-of-sight
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Velocity DispersionsMcKay (2002), Prada et al (2003), and Brainerd (2004)
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The Data Sample
• New York University Value-Added Galaxy Catalog (NYU-VAGC) – Lowz (Sub Sample of ~50,000 galaxies)
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Ensembles
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Robust Analysis
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Velocity Dispersion Curve
Prada et al (2003), and Brainerd (2004)
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Galaxies Types
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Early vs. Late
• Early type galaxies have larger halos than late type galaxies
• Conroy et al. (2007)
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What These Results Tell Us
• Rotation curve (consistent with NFW)– Supports hierarchical scenario
• Halo sizes– Larger primordial dark matter halos for early
type galaxies than for late type galaxies
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Stellar Properties
• How does the satellite stellar properties change as a function of distance from the primary?– Star formation from self gravity or tidal effects from
primary
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Stellar properties of Satellites
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What Does This Mean
• Primaries cause "tidal" effects on their satellites – Kosh and Grebal (2006)
• More pronounced in satellites with primaries that have a larger mass (halo)
• Different distribution in Systems at larger z (longer ago)
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The Holmberg Effect
Holmberg (1969)
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Modeling
• Check for Isotropy– polar fraction ~0.70– Mean = 45 degrees
• Interloper check– P/T >> 0.5
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Results for Primary tilt < 30o
No Holmberg found in my data
o
5.45
Kolmogorov-Smirnov (KS) test
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Results for Varying tilts angle No Holmberg found in my data
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Binned Results for Primary tilt < 30o
Brainerd (2005)
Sales & Lambas (2004), Koch & Grebel (2006)Zaritsky et al. (1997)
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Binned Results for Primary tilt > 60o
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What does this tell us?
• Dark Matter halo– Spherical
• Puts constraints on models– Infall through fillaments
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2D Velocity Dispersions
• Velocity Distribution– Isotropic about primary
• DM halo– Spherical
45~tilt
45~tilt
iiiR
iiR
zR
zmaj
22222min
22222
cossincos
cossin
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Conclusion
• The Dynamic Properties– Dark Matter Halos
• Different sizes for different type of galaxies• Consistent with NFW (hierarchical scenario)
• The Spatial Properties– Satellites are isotropically distributed, and
have isotropic velocity distribution• Spherical Dark Matter Halo
– Star formation depends on distance from their primary
• Primaries effect their satellites