Traditionally , the distance to NGC 4038/39 has been derived from the systemic recession velocity , yielding about 20 Mpc for H _ { 0 } = 72 km s ^ { -1 } Mpc ^ { -1 } .
Recently , this widely adopted distance has been challenged based on photometry of the presumed tip of the red giant branch ( TRGB ) , which seems to yield a shorter distance of 13.3 \pm 1.0 Mpc and , with it , nearly 1 mag lower luminosities and smaller radii for objects in this prototypical merger .
Here we present a new distance estimate based on observations of the Type Ia supernova ( SN ) 2007sr in the southern tail , made at Las Campanas Observatory as part of the Carnegie Supernova Project .
The resulting distance of \mbox { $D _ { SN Ia } $ } = 22.3 \pm 2.8 Mpc [ ( m - M ) _ { 0 } = 31.74 \pm 0.27 mag ] is in good agreement with a refined distance estimate based on the recession velocity and the large-scale flow model developed by Tonry and collaborators , \mbox { $D _ { flow } $ } = 22.5 \pm 2.8 Mpc .
We point out three serious problems that a short distance of 13.3 Mpc would entail , and trace the claimed short distance to a likely misidentification of the TRGB .
Reanalyzing Hubble Space Telescope ( HST ) data in the Archive with an improved method , we find a TRGB fainter by 0.9 mag and derive from it a preliminary new TRGB distance of \mbox { $D _ { TRGB } $ } = 20.0 \pm 1.6 Mpc .
Finally , assessing our three distance estimates we recommend using a conservative , rounded value of D = 22 \pm 3 Mpc as the best currently available distance to The Antennae .