Determining the Motion of the Local Group Using SN Ia Light Curve Shapes

摘要

We have measured our Galaxy's motion relative to distant galaxies in whichtype Ia supernovae (SN Ia) have been observed. The effective recession velocityof this sample is 7000 km s$^{-1}$, which approaches the depth of the survey ofbrightest cluster galaxies by Lauer and Postman (1994). We use the Light CurveShape (LCS) method for deriving distances to SN Ia, providing relative distanceestimates to individual supernovae with a precision of $sim$ 5% (Riess,Press, & Kirshner 1995). Analyzing the distribution on the sky of velocityresiduals from a pure Hubble flow for 13 recent SN Ia drawn primarily from theCal'{a}n/Tololo survey (Hamuy 1993a, 1994, 1995a, 1995b, Maza et al. 1994), wefind the best solution for the motion of the Local Group in this frame is 600$pm 350$ km s$^{-1}$ in the direction b=260$deg$ {it l}=+54$deg$ with a 1$sigma$ error ellipse that measures 90$deg$ by 25$deg$. This solution isconsistent with the rest frame of the cosmic microwave background (CMB) asdetermined by the Cosmic Background Explorer (COBE) measurement of the dipoletemperature anisotropy (Smoot et al. 1992). It is inconsistent with thevelocity observed by Lauer and Postman.