The Local Void - AMIGA
Transcript of The Local Void - AMIGA
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The Local Void!
Brent Tully !Institute for Astronomy!University of Hawaii !
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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!
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Tom Jarrett’s 2MASS Extended Source Catalog
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the local volume
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Mapping the local volume: !hundreds of 5% distances within
6 Mpc
marginal at 5 Mpc
OK at 8 Mpc
good at 3 Mpc
Extragalactic Distance Database!
http://edd.ifa.hawaii.edu!select CMDs/TRGB catalog!
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We are traveling with the Local Sheet as a unit!The Local Sheet is a wall bounding the Local Void
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 Sheet (Karachentsev et al. 2003, AA, 398, 479) cold flow!!
green/yellow Vpec~0 red Vpec > +100 blue Vpec < -100 !
Edge-on to Supergalactic plane!
Pole-on to Supergalactic plane!
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Where is the Local Sheet going?
Orange vector shows our motion w.r.t. 1800 galaxies with distance measurements within 3,000 km/s!
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vector decomposition Assume component toward Virgo Cluster: 185 km/s => l = 283.8 sgl = 102.9 b = 74.5 sgb = -2.4
Subtract from 323 km/s Local Supercluster vector:
259 km/s => l = 210 sgl = 11 b = -2 sgb = -72 => evacuation of Local Void
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A galaxy in the void
The lonely dwarf galaxy ESO461-36 = KK246 at 6.4 Mpc within the Local Void has a peculiar velocity
toward us of -30 km/s!
Our peculiar motion in the Local Supercluster of 323 km/s is almost in the same direction, so the peculiar motion out of the void of ESO461-36 = KK246 is at least 350 km/s with respect to the Local Supercluster !
TRGB!
HI !
KK246!MB=-14 !
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Bulk Peculiar Velocities
Virgo!
Leo Spur !
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Voids push!
In the currently favored cosmology model, empty regions expand at 16 km/s/Mpc.!
To explain an evacuation motion of 260 km/s, the Local Void must be at least 45 Mpc across and be very empty. !
velo
city!
position!
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Other galaxies in the Local Void MCG-02-41-001 !
MCG-01-57-015 ! UGCA 433 = DDO 215!
NGC 7077 (BCD)!
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(again)!Where is the Local Sheet going?
185 km/s !
void reflex 259 km/s!
455 km/s!
attractors on large scales!
Kocevski & Ebeling 2006, ApJ, 645, 1043!
Virgo 185 km/s!
large scale 455 km/s!