1. Inner Halo Shapes of Dwarf Galaxies: Reconciling the Cusp/Core Problem Kristine Spekkens, Riccardo Giovanelli (Cornell) 203 rd AAS, Session 105: Wednesday, 7 January 2004 minimum disk spherical symmetry Density profiles from long-slit spectra: 0.2 0.6 1.0 100 60 r/r opt V rot (km/s) Rotation curve -2 0 1 log(r,kpc) log  M o /pc 3 ) Density profile

2. Kristine Spekkens – Inner Halo Shapes of Dwarf Galaxies Galaxy Sample and Analysis Select low mass systems from ~4800 object SFI++: V rot < 130 km/s H  spectroscopy No bulges, bars from I-band photometry 200 galaxies Invert RCs:  r -  m (small r) CDM predicts  int ~1 Direct inversion yields  m ~0.2 Cusp/core problem: Is distribution of  m consistent with  int  expected from CDM? 20 40 Number of galaxies 0.2 0.6 1 mm

3. Kristine Spekkens – Inner Halo Shapes of Dwarf Galaxies Dwarf Population Simulations 1. Embed infinitely thin, uniform H  disks inside NFW halos (  int = 1) 2. Observables random deviates of sample distributions 3. “Observe” simulated galaxies with single slit in same conditions as for sample 4. Analyze “observations” with same algorithms as for data data 0.2 0.6 1 mm 0.1 0.2 Fraction galaxies data 0.2 0.6 1 mm 0.1 0.2 Fraction galaxies sim.,  int = 1

4. Kristine Spekkens – Inner Halo Shapes of Dwarf Galaxies Dwarf Population Simulations data sim.,  int = 1 mm mm 4080 120 0.3 0.5 0.3 0.5 Distance, Mpc 607080 Inclination, deg 1. Embed infinitely thin, uniform H  disks inside NFW halos (  int = 1) 2. Observables random deviates of sample distributions 3. “Observe” simulated galaxies with single slit in same conditions as for sample 4. Analyze “observations” with same algorithms as for data

5. Kristine Spekkens – Inner Halo Shapes of Dwarf Galaxies Varying  int data 0.2 0.6 1 mm 0.1 0.2 Fraction galaxies sim.,  int = 0.5 Inner slopes from sample are: CONSISTENT with  int = 0.5

6. Kristine Spekkens – Inner Halo Shapes of Dwarf Galaxies Varying  int data 0.2 0.6 1 mm 0.1 0.2 Fraction galaxies sim.,  int = 1.25 Inner slopes from sample are: CONSISTENT with  int = 0.5 CONSISTENT with  int = 1 CONSISTENT with  int = 1.25

7. Kristine Spekkens – Inner Halo Shapes of Dwarf Galaxies Varying  int data 0.2 0.6 1 mm 0.1 0.2 Fraction galaxies sim.,  int = 1.5 Inner slopes from sample are: CONSISTENT with  int = 0.5 CONSISTENT with  int = 1 CONSISTENT with  int = 1.25 INCONSISTENT with  int = 1.5

8. Kristine Spekkens – Inner Halo Shapes of Dwarf Galaxies Is There Really a Cusp-Core Problem?  int = 0.5  int = 1  int = 1.25  int = 1.5 0.20.60.20.60.20.6 0.20.6 1.0 0.2 0.1 Fraction gals. mm mm mm mm Inner halo slopes derived from long-slit spectra are consistent with cuspy profiles predicted by CDM Recover distribution of  m from cuspy  int with simulations of observing and data processing techniques (NFW)