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