Hundreds of Milky Way Satellites Luminosity Bias in

Hundreds of Milky Way Satellites? Luminosity Bias in the Satellite Luminosity Function Erik J. Tollerud UC Irvine Collaborators: James Bullock, Louie Strigari, Beth Willman Tollerud et al. 2008, Ap. J In Press, Ar. Xiv: 0806. 4381 Santa Cruz Galaxy Formation Workshop 2008

Overview Introduction Bias Correction (Lum. and Anisotropy) SDSS Detection Limits Via Lactea and Radial Distributions Results/Satellite Counts Future Surveys

Introduction Missing Satellite Problem (Klypin et al. 1999, Moore et al. 1999)

Bias Correction

Bias Correction

Bias Correction

SDSS Detection Limits Tollerud et al. 2008 Lines from Koposov et al. 2007 Shaded region from Walsh, Willman, & Jerjen 2008

Via Lactea and Observed Satellites Tollerud et al. 2008 Public data release of Via Lactea: see Diemand, Kuhlen, & Madau 2007 Correction only depends on radial distribution from VL Observed Satellites centrally biased Less biased if luminosity bias considered

Subhalo Anisotropy fsubhalos (l, b, Ω=ΩSDSS) Tollerud et al. 2008

Corrected MW Satellite Luminosity Function Tollerud et al. 2008

Multiple Scenario Results Variables: Inclusion of faintest d. Sphs VL Subhalo population Router Detection Limits Scenarios can have very different faint-end slopes Tollerud et al. 2008

~400 Satellites - Implications Data from Strigari et al. 2007 Diemand et al. 2008

Future Surveys Tollerud et al. 2008 Detectable Satellites in survey footprint: LSST: 93 -179/145 -283 Skymapper: 42 -79 DES: 19 -37 Surveys should show significantly different faint-end slopes

Conclusions Hundreds of d. Sphs is not crazy talk LSST will find the missing satellites if they are there, but smaller surveys will find some, and sooner Faint-end slope is not yet well constrained, but probably still rising

KS Test Results

MW Sats

Scenarios 2, 3, 4: inc Seg 1, excl Wil 1, Boo II 5 -10: different subhalo populations 11 -14: Router 200, 389, 500 15: unit detection efficiency 16 -17: different detection limits 18: Constant sky coverage

Scenario Results

All Distributions

Introduction Missing Satellite Problem (Klypin et al. 1999, Moore et al. 1999)

Luminosity Bias

Anisotropy