Ultra-faint dwarfs as fossils of the First Galaxies Mia S. Bovill Advisor: Massimo Ricotti University of Maryland Mia S. Bovill Advisor: Massimo Ricotti University of Maryland

Outline Properties of Fossil Galaxies Missing Dwarfs Evolving Fossils to z = 0 Properties of Fossil Galaxies Missing Dwarfs Evolving Fossils to z = 0

Feedback For halos with T VIR < 10 4 K, H 2 serves as the primary coolant. Negative Feedback H 2 is dissociated by non-ionizing UV radiation from Pop III stars. Only M > 10 8 M  can shield enough H 2 to form stars ( ie. Haiman et al, 2000 ). Halos below 10 8 M  will be dark. Positive Feedback Ionizing UV radiation facilitates formation of H 2, lowering the mass threshold for star formation ( ie. Whalen et al (2007) ). When relevant physics is included, stars form in halos of only 10 5 M  ( Ricotti et al (2002a,b) (R02a,b) ). For halos with T VIR < 10 4 K, H 2 serves as the primary coolant. Negative Feedback H 2 is dissociated by non-ionizing UV radiation from Pop III stars. Only M > 10 8 M  can shield enough H 2 to form stars ( ie. Haiman et al, 2000 ). Halos below 10 8 M  will be dark. Positive Feedback Ionizing UV radiation facilitates formation of H 2, lowering the mass threshold for star formation ( ie. Whalen et al (2007) ). When relevant physics is included, stars form in halos of only 10 5 M  ( Ricotti et al (2002a,b) (R02a,b) ).

Sloan Dwarf Observations DwarfDiscoveryFollow-up Bootes I**Belokurov et al (2006)Munoz et al (2006), Bailin & Ford (2006), Martin et al (2007) Bootes II**Walsh et al (2007) Canes Venatici IZucker et al (2006a)Ibata et al (2006), Martin et al (2007), Simon & Geha (2007) Canes Venatici II**Belokurov et al (2007)Simon & Geha (2007) Coma Berenics**Belokurov et al (2007)Simon & Geha (2007) HerculesBelokurov et al (2007)Simon & Geha (2007) Leo IVBelokurov et al (2007)Simon & Geha (2007) Leo TIrwin et al (2007)Simon & Geha (2007) Ursa Major I**Willman et al (2005)Kleyna et al (2005), Martin et al (2007), Simon & Geha (2007) Ursa Major IIZucker et al (2006b)Martin et al (2007), Simon & Geha (2007) Willman IWillman et al (2005)Martin et al (2007) ** fossils

M31 Dwarf Observations DwarfDiscoveryFollow-up And XI Martin et al (2006) And XII Martin et al (2006)Chapman et al (2007) And XIII Martin et al (2006) And XIV Majewski et al (2007) And XV Ibata et al (2007) And XVI Ibata et al (2007) ** fossils

Fossil Properties I Willman I SDSS limits Ricotti & Gnedin (2005), Bovill et al. (2007, in prep) R02a,b predictions. Known survivors Known polluted fossils Known true fossils New ultra-faint dwarfs ~ Ultra-faint dwarfs are detected to Sloan limits.

Fossil Properties II Ricotti & Gnedin (2005), Bovill et al. (2007, in prep) R02a,b predictions. Known survivors Known polluted fossils Known true fossils New ultra-faint dwarfs ~ Without fossils, predicted L v and r c values for given I c are significantly above new observations. ~ M31 dwarf properties are consistent with predictions and known Milky Way fossils. Milky Way M31 Milky Way M31 Willman I

Fossil Properties III ~ Observed and predicted values trace mass to edge of stellar distribution. ~ Ricotti & Gnedin (2005) predicted existence of high M/L fossil population. Ricotti & Gnedin (2005), Bovill et al. (2007, in prep) R02a,b predictions. Known survivors Known polluted fossils Known true fossils New ultra-faint dwarfs

Fossil Properties IV Ricotti & Gnedin (2005), Bovill et al. (2007, in prep) R02a,b predictions. Known survivors Known polluted fossils Known true fossils New ultra-faint dwarfs ~ Z vs. L v scatter for ultra-faint dwarfs agrees with fossil predictions. ~ Scatter in Z due to: - pollution from nearby halos - multiple bursts of star formation ( ie. Stinson et al (2007) ) ~ Where are dwarfs with Z < selection effects - physical effects

Evolving Fossils to z = 0 Fossil properties at z = 0 are simply related to their properties at reionization. R02a,b results can be evolved to z=0 Statistical comparison for a “Milky Way” ( Gnedin & Kravtsov, 2006 ) Direct N-body evolution for a “Local Volume” ( Bovill & Ricotti, in prep ) Fossil properties at z = 0 are simply related to their properties at reionization. R02a,b results can be evolved to z=0 Statistical comparison for a “Milky Way” ( Gnedin & Kravtsov, 2006 ) Direct N-body evolution for a “Local Volume” ( Bovill & Ricotti, in prep )

Observation Completeness Correction We assume satellites are in an isotropic distribution around their hosts and the new dwarfs are a representative sample. SDSS covers 1/4 of the sky. Recent surveys covered ~ 1/4 of the sky around M31 We multiply the numbers of new dwarfs by 4 for both galaxies to account for observational bias. We assume satellites are in an isotropic distribution around their hosts and the new dwarfs are a representative sample. SDSS covers 1/4 of the sky. Recent surveys covered ~ 1/4 of the sky around M31 We multiply the numbers of new dwarfs by 4 for both galaxies to account for observational bias.

Luminosity Function ~ For d < 100 kpc observations and theory agree ~ For d > 100 kpc SDSS cannot detect M V < -5 (L V < 8 x 10 3 L  ) ( Koposov et al (2007) ) ~ WMAP III parameters may lower the number of halos at large distances from their hosts. Gnedin & Kravtsov (2006) Bovill et al, in prep

Radial Distribution 250 kpc SDSS limit for HB (Simon & Geha, 2007) ~ L > 10 5 L  shows good agreement out to 1 Mpc ~ L > 10 3 L  matches well for d 250 kpc can be partially explained by observational bias. Gnedin & Kravtsov (2006), Bovill et al., in prep

Need for primordial dwarfs Simulations predict ~40 halos with v circ > 20 kms -1 ( Kravtsov et al (2004), Diemand et al (2007a,b) ). Milky Way now has: 16 previously known satellites 11 ultra-faint Sloan Dwarfs ~ 30 undiscovered dwarfs above SDSS detection limits If primordial fossils are included, ~100 halos are within L > 10 3 L  within 300 kpc of the Milky Way ( Gnedin & Kravtsov, 2006 ). Simulations predict ~40 halos with v circ > 20 kms -1 ( Kravtsov et al (2004), Diemand et al (2007a,b) ). Milky Way now has: 16 previously known satellites 11 ultra-faint Sloan Dwarfs ~ 30 undiscovered dwarfs above SDSS detection limits If primordial fossils are included, ~100 halos are within L > 10 3 L  within 300 kpc of the Milky Way ( Gnedin & Kravtsov, 2006 ).

Evolving Fossils to z = 0 Fossil properties at z = 0 are simply related to their properties at z reion. R02a,b results can be evolved to z=0 Statistical comparison for single “Milky Way” ( Gnedin & Kravtsov, 2006 ) Direct N-body evolution for a “Local Volume” ( Bovill & Ricotti, in prep ) Adding large scale modes, create a 10 3 Mpc 3 volume from 1 Mpc 3 R02a,b results. Embed in a 50 3 Mpc 3 low resolution centered on a filament. Run from z ~10 to z = 0. Fossil properties at z = 0 are simply related to their properties at z reion. R02a,b results can be evolved to z=0 Statistical comparison for single “Milky Way” ( Gnedin & Kravtsov, 2006 ) Direct N-body evolution for a “Local Volume” ( Bovill & Ricotti, in prep ) Adding large scale modes, create a 10 3 Mpc 3 volume from 1 Mpc 3 R02a,b results. Embed in a 50 3 Mpc 3 low resolution centered on a filament. Run from z ~10 to z = 0.

z = 0 Luminosity Function ~ M HOST ~ 2 x M  ~ Approximately 1/5 the dwarfs expected for the Milky Way ~ Number of dwarfs with d < 1 Mpc results agree with Gnedin & Kravtsov (2006) red = M < 10 9 M 

z = 0 Radial Distribution red = M < 10 9 M  ~ M HOST ~ 2 x M  ~ L > 10 5 L SUN new results agree with Gnedin & Kravtsov (2006) at 300 kpc. ~ Increase for d > 300 kpc due to our host galaxy not being isolated.

Summary Properties of the new Sloan and M31 dwarfs agree well with predictions for primordial galaxies Within SDSS limits, the missing satellite problem is almost solved. Tidal formation alone cannot produce enough dwarfs to account for the SDSS additions. Properties of the new Sloan and M31 dwarfs agree well with predictions for primordial galaxies Within SDSS limits, the missing satellite problem is almost solved. Tidal formation alone cannot produce enough dwarfs to account for the SDSS additions.

Initial Conditions Start Point - Ricotti et al (2002a,b) 1 Mpc 3 HD simulation including the effects of radiative transfer run to z = 8.3. ~ A HD run to z=0 is not computationally possible. ~ We turn HD halos into N-body particles and create a larger volume. ~ Density fluctuations on > 1 Mpc scales are then added.

The First Galaxies At high z, the majority of the universe’s mass was contained in halos < 10 8 M . Approximately 10% of these early dwarfs will survive untouched to z = 0. CITATION??

DR6 Predictions SDSS DR6 (Citation) will include M31 And XI - XVI have similar properties to previously known Milky Way dwarfs From SDSS limits and current predictions we estimate 12 new dwarfs between 100 and 300 kpc of M31 are detectable by SDSS SDSS DR6 (Citation) will include M31 And XI - XVI have similar properties to previously known Milky Way dwarfs From SDSS limits and current predictions we estimate 12 new dwarfs between 100 and 300 kpc of M31 are detectable by SDSS

What is a Fossil*? *defined by Ricotti & Gnedin (2005) Survivors (M > 10 9 M  ) * star formation started after reionization * mostly dIrr, some dE LMC M32 Polluted fossils (M ~ /9 M  ) * significant star formation after reionization * tidal effects from host cause additional bursts * dSph and dE Pegasus True fossils (M ~ /9 M  ) * < 30% of stars formed after reionization * never accreted gas from the IGM * mostly dSph Cetus