Our CMB Motion: The Local Void influence Voids Devoid of Dwarfs: Cosmology or Gastrophysics?

Brent Tully Institute for Astronomy University of Hawaii

Fact 1: Gastrophysics must be important

because

the faint end of the luminosity function of galaxies depends on environment

More dynamically evolved regions have steeper faint-end luminosity functions

Fact 2: The Dwarfs in Dynamically Evolved Regions Overwhelmingly dE N5353/4 Group are Local Group radius N5846 Group

Fact 2: The Dwarfs in Dynamically Evolved Regions Overwhelmingly dE N5353/4 Group are Local Group radius Show me a concentration of dE galaxies and I’ll show you a place with large M/L N5846 Group

Fact 3: Groups of Dwarfs Evidence for Dark Halos

All-sky census of dwarf galaxies and follow up observations with HST/ACS:  most dwarfs are in groups  most of the mass in small groups is invisible  gastrophysics inhibits the collection of gas and star formation in low mass halos or low density regions

Fact 4:

The Local Void

- a void extending 60 Mpc begins at the edge of the Local Group HI P arkes A ll S ky S urvey Time Allocation Committees could have inferred the existence of the Local Void

hundreds of 5% distances within 6 Mpc

marginal at 5 Mpc OK at 8 Mpc good at 3 Mpc

green/yellow V pec ~0 red V pec blue V pec > +100 < -100

• co-moving motion of the Local Group w.r.t.

159 galaxies at 1.1 < d < 7 Mpc is 9 km/s negligible!!

• velocity dispersion about the local expansion of groups and galaxies outside of groups is ~40 km/s within the Local Filament (Karachentsev et al. 2003, AA, 398, 479) cold flow!!

Fact 5:

we are traveling with the Local Filament as a unit

Where is the Local Filament going?

vector decompositions 1 Assume component toward Virgo Cluster: ~200 km/s => l = 282.9 sgl = 102.7

b = 74.5 sgb = -2.3

Subtract from Local Supercluster vector : ~211 km/s => l = 213 sgl = 12 b = -3 sgb = -75 attributed primarily to evacuation of Local Void

what does nothing look like?

SGX SGY

A galaxy in the void The lonely dwarf galaxy ESO461 36 = KK246 at 9 Mpc within the Local Void has a peculiar velocity toward us of -216 km/s KK246 Our peculiar motion in the Local Supercluster of 298 km/s is almost in the same direction, so the peculiar motion out of the void of ESO461-36 = KK246 is at least 500 km/s with respect to the Local Supercluster M B =-14 HI TRGB

Bulk Peculiar Velocities Leo Spur Virgo

Local Void

milky way 211 km/s 36 o 45 o 8.9 Mpc 56 o 7.8 Mpc 9.5 Mpc -285 km/s -260 km/s -400 km/s -260 km/s NGC 2903 -510 km/s UGC 3974 -540 km/s D634-03 local filament ~6 Mpc Leo spur

local velocity anomaly

vector decompositions 2 CMB motion Local Group frame:  l = 275.2 b  619 km/s = 28.7

sgl = 140.2 sgb= -32.2

Subtract Local Supercluster vector leaves large-scale structure component:  l ~446 km/s = 300 b = 15  sgl = 163 sgb = -15 Attributed to structure on scales > 3,000 km/s

(again)

Where is the Local Filament going?

~446 km/s ~200 km/s ~211 km/s attractors on large scales Kocevski & Ebeling 2006, ApJ, 645, 1043

1.

The ratio of dwarf to giant galaxies is highest in high density , dynamically evolved environments. In the standard hierarchical clustering paradigm, the ratio of low to high halo mass is higher in low density , dynamically unevolved regions. Either the paradigm is wrong or gas & stars are preferentially excluded from low mass halos in low density regions.

Conclusio ns:

2.

The evident existence of groups of dwarfs with extreme M/L suggest that gas & stars are excluded in these locals . It must be considered likely that the paucity of dwarfs in voids is due to the inability of halos to collect or retain gas in those environments .

1.

The ratio of dwarf to giant galaxies is highest in high density , dynamically evolved environments. In the standard hierarchical clustering paradigm, the ratio of low to high halo mass is higher in low density , dynamically unevolved regions. Either the paradigm is wrong or gas & stars are preferentially excluded from low mass halos in low density regions.

Conclusio ns:

2.

The evident existence of groups of dwarfs with extreme M/L suggest that gas & stars are excluded in these locals . It must be considered likely that the paucity of dwarfs in voids is due to the inability of halos to collect or retain gas in those environments . 3.

The Local Filament within 7 Mpc is moving as a unit with low internal dispersion. The bulk motion of the filament is decomposed cleanly into 3 quasi-orthogonal components: a motion of ~200 km/s away from the Local Void , a motion of ~200 km/s toward the Virgo Cluster , and a motion of ~450 km/s toward clustering on large scales in the direction of Centaurus. 4.

While we are moving toward -SGZ , the adjacent filament south of the supergalactic equator called Leo Spur has a bulk peculiar motion toward +SGZ and consequently is converging with our filament (in co-moving coordinates). 5.

The lonely dwarf galaxy ESO 461-36 lies 9 Mpc away, 8 Mpc deep into the Local Void. The galaxy appears to be a normal dIrr, with HI and leisurely ongoing star formation. The galaxy has a LARGE peculiar velocity toward the boundary of the void of over 500 km/s.