distances to supernovae with the expanding shock front method
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Distances to Supernovae with the Expanding Shock Front Method. Norbert Bartel and Michael Bietenholz (York University). Contents. The Expanding Shock Front Method SN 1993J - Images - Radio Expansion - Optical Expansion - PowerPoint PPT PresentationTRANSCRIPT
Distances to Supernovae with the Distances to Supernovae with the Expanding Shock Front Method Expanding Shock Front Method
Norbert Bartel and Michael Bietenholz (York University)
Contents
• The Expanding Shock Front Method• SN 1993J - Images - Radio Expansion - Optical Expansion - Distance• SN 1979C - Image - Radio Expansion - Optical Expansion - Distance• Conclusions
Angular expansion of SN1993J
66 radius measure-
ments
Radial velocity from optical lines
SN1993JHighest rel. resolution
The Expanding Shock Front Method
D = ---------------
Vopt. max ηκ
Θo •
Vopt. max = max. radial velocity from opt. lines (v of reverse shock)
Θo = angular velocity of outer boundary of radio shell (of forward shock)•
η = outer to inner angular radius of radio shell
Κ = isotropy factor, 1 for spherical symmetry
Shell profiles
Ratio of outerto inner radius,η, determined within 3%
Explosion center:± 45 µas or ± 160 AU
Proper motion:± 9 µas/yr or ± 160 km/s
Peculiar proper motion:320 ±160 km/s to south
Astrometry: M81* core - SN1993J
Limit onanisotropic expansion: 5.5%
Radio and optical velocities
M81: D=4.3±0.6 Mpc
Forward shock
Reverse shock
M100 in the Virgo Cluster
SN 1979C
VLBI image of SN 1979C at t=22 yrVLBI image of SN 1979C at t=22 yr
Modelfit:Circularly symmetricwithin 9%
Visibility curve of SN 1979C at t=22 yrVisibility curve of SN 1979C at t=22 yr
The expansion of SN 1979 C
consistent with almost free expansion for 22 yr
±0.03
Radial velocity from optical lines
Radio and optical velocities
Forward shock
Reverse shock
1.
M100: D=16.5±2.0 Mpc
Conclusions
• The Expanding Shock Front Method allows geometric distance measurements to be made for supernovae < 30 Mpc.
• SN 1993J in M81 D=4.3±0.6 Mpc (3.6±0.4 Mpc from Cepheids)
• SN 1979C in M100 in Virgo D=16.5±2.5 Mpc (uniform sphere) D=19.8±3.0 Mpc (shell) (15.2 --16.5±1.3 Mpc Ceph.)
D=3.6±0.4 Mpc
From Cepheids, Freedman et al. (2001)
With velocity error of reverse shock
With velocity error of reverse shock
1.
Composite Image made from data from three epochs combined
Image with highest resolution
The expansion of SN 1979C
Strong decelerationMarcaide et al. 2002
Optical-Radio Velocity comparison for D=16.5 Mpc
Forward shock
Reverse shock