Dynamic and Spatial Properties of Satellitesin Isolated Galactic Systems

Abel B. Diaz

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

Rotation Curves:Probing the mass distribution

• Within Galaxy– Well known

• External to Galaxy– Not well known

Fritz Zwicky (1933)Babcock (1939)&Vera Rubin (1970)

The Problem

• How does the mass distribution of galaxies change with distance beyond the disk of the galaxy?

What would this tell us?

• Learning more about the mass distribution of isolated galaxies may provide insight into galaxy– formation – evolution– LSS

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

Limits on Isolated Galaxies

1. Small number of detectable satellites

2. Line-of-sight velocity

3. Projected distance

Isolated Galaxy Ensembles

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

Velocity DispersionsMcKay (2002), Prada et al (2003), and Brainerd (2004)

The Data Sample

• New York University Value-Added Galaxy Catalog (NYU-VAGC) – Lowz (Sub Sample of ~50,000 galaxies)

Ensembles

Robust Analysis

Velocity Dispersion Curve

Prada et al (2003), and Brainerd (2004)

Galaxies Types

Early vs. Late

• Early type galaxies have larger halos than late type galaxies

• Conroy et al. (2007)

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

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

Stellar properties of Satellites

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)

The Holmberg Effect

Holmberg (1969)

Modeling

• Check for Isotropy– polar fraction ~0.70– Mean = 45 degrees

• Interloper check– P/T >> 0.5

Results for Primary tilt < 30o

No Holmberg found in my data

o

5.45

Kolmogorov-Smirnov (KS) test

Results for Varying tilts angle No Holmberg found in my data

Binned Results for Primary tilt < 30o

Brainerd (2005)

Sales & Lambas (2004), Koch & Grebel (2006)Zaritsky et al. (1997)

Binned Results for Primary tilt > 60o

What does this tell us?

• Dark Matter halo– Spherical

• Puts constraints on models– Infall through fillaments

2D Velocity Dispersions

• Velocity Distribution– Isotropic about primary

• DM halo– Spherical

45~tilt

45~tilt

iiiR

iiR

zR

zmaj

22222min

22222

cossincos

cossin

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