AAS 197, January 2001
Session 119. The Cosmic Distance Scale
Oral, Thursday, January 11, 2001, 10:30am-12:00noon, San Diego

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[119.02] An HST Cepheid Distance to NGC 2841

G. D. Bothun (University of Oregon), W. Freedman (Carnegie Observatories), P. Garnavich (Notre Dame), L. Macri (Harvard-Smithsonian Center for Astrophysics), M. Richmond (Rochester Institute of Technology)

Seventeen orbits in V and I have been used to detect Cepheids in the large rotational velocity spiral galaxy NGC 2841. Approximately 30 Cepheids were detected in the observed fields thus securing a relatively accurate distance. This galaxy was chosen for study because a) it has hosted two supernova in the past and, fortuitously (i.e. we didn't plan this), SN 1999by decided to occur in this host, b) it extends the calibration of the Cepheid based Tully-Fisher relation to larger line widths than the current calibration (the rotational velocity of N2841 is 300 km/s) and c) an accurate distance provides a critical test of Modified Newtonian Dynamics (MOND).

Preliminary reductions of the Cepheid data indicate a distance of 12 +/- 1 Mpc. This distance is significantly less than the MOND required distance of 19.5 Mpc. This distance is also approximately 0.75 mag less than that obtained by applying the current calibration of the SN Ia luminosity scale. Finally, this distance is also significantly less than the predicted TF distance given the observed line width. The implications of this curious combination of results will be briefly discussed.

This work was performed with support from the Cycle 8 GO program at HST.

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