our cmb motion: the local void influence voids devoid of dwarfs: cosmology or gastrophysics? brent...
TRANSCRIPT
Our CMB Motion: The Local Void influence
Voids Devoid of Dwarfs: Cosmology or Gastrophysics?
Brent Tully Institute for AstronomyUniversity 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 are Overwhelmingly dE
N5353/4 Group
N5846 Group
Local Group
radius
velocity
Fact 2: The Dwarfs in Dynamically Evolved Regions are Overwhelmingly dE
Show me a concentration of dE galaxies and I’ll show you a place with large
M/L
N5353/4 Group
N5846 Group
Local Group
radius
velocity
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 Parkes All Sky Survey
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
Fact 5: we are traveling with the Local Filament as a unit
• 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!!
green/yellow Vpec~0red Vpec > +100blue Vpec < -100
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 = -75attributed primarily to evacuation of Local Void
what does nothing look like?
SGX SGY
SGZ
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
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
TRGBHI
KK246
MB=-14
Bulk Peculiar Velocities
Virgo
Leo Spur
local velocity anomaly
56o
45o
36o
7.8 Mpc
8.9 Mpc
9.5 Mpc
-400 km/s
-540 km/s
-285 km/s-260 km/s
-510 km/s
-260 km/s
local filament
Leo spur
~6 Mpc
Local Void
UGC 3974 D634-03
NGC 2903
milky way
211 km/s
vector decompositions 2
CMB motion Local Group frame: 619 km/s l = 275.2 b = 28.7 sgl = 140.2 sgb= -32.2
Subtract Local Supercluster vectorleaves large-scale structure
component: ~446 km/s l = 300 b = 15 sgl = 163 sgb = -15
Attributed to structure on scales > 3,000 km/s
(again)
Where is the Local Filament going?
~200 km/s
~211 km/s
~446 km/s
attractors on large scales
Kocevski & Ebeling 2006, ApJ, 645, 1043
Conclusions: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.
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.
Conclusions: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.
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.