Dynamic and Spatial Properties of Satellites in 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 Dispersions McKay (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 < 30 o No Holmberg found in my data Kolmogorov-Smirnov (KS) test

Results for Varying tilts angle No Holmberg found in my data

Binned Results for Primary tilt < 30 o Brainerd (2005) Sales & Lambas (2004), Koch & Grebel (2006) Zaritsky et al. (1997)

Binned Results for Primary tilt > 60 o

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

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