The Cepheid Distance to NGC 5253: Calibration of $M(max)$ for SNe Ia 1972E and 18955B
Session 72 -- High Z Line Measurements; Gravitational Microlensing: Distance Determination
Display presentation, Friday, January 14, 9:30-6:45, Salons I/II Room (Crystal Gateway)

## [72.14] The Cepheid Distance to NGC 5253: Calibration of $M(max)$ for SNe Ia 1972E and 18955B

A. Saha$^{1}$, N. Panagia$^{1}$, A. Sandage$^{2}$, G. A. Tammann$^{3}$, L. Labhardt$^{3}$, H. Schwengeler$^{3}, F. D. Macchetto$^{1} ( $^{1}$Space Telescope Science Institute, $^{2}$Observatories of the Carnegie Institution of Washington, $^{3}$Astronomisches Institut der Universitat Basel)

The apparent $V$ band distance modulus of NGC 5253, parent galaxy to the type Ia supernovae 1972E and 1895B, is $(m -M)_{AV} = 28.06 \pm 0.06$ mag determined from eleven Cepheid variables with unambiguous periods obtained with the Hubble Space Telescope . The internal reddening is zero to within $E(B - V) < 0.03$ mag, determined from four independent methods. \par The absolute magnitudes of SN Ia 1972E are $M_{B}(max) = -19.53 \pm 0.12$, and $M_V(max) = -19.46 \pm 0.12$. The absolute magnitude of SN Ia 1895B is $M_{B}(max) = -19.69 \pm 0.21$, based on $B(max) = 8.4 \pm 0.2$ determined by correcting Walker's (1923) comparison stars to the modern photoelectric zero point in $B$. \par Combining these data with the data for SN 1937C in IC 4182 determined earlier gives mean values of $= -19.55 \pm 0.08$ mag based now on three calibrations relative to Cepheids, and $= -19.58 \pm 0.09$ mag based on two Cepheid determinations. \par Using the extant Hubble diagrams in B and V for SN Ia gives the global values of the Hubble constant as \begin{displaymath} H_{0}(B) = 52 \pm 8 ~{\rm km s^{-1} Mpc^{-1} } \end{displaymath} and \begin{displaymath} H_{0}(V) = 55 \pm 8 ~{\rm km s^{-1} Mpc^{-1} } \end{displaymath}

The quoted error is the external uncertainty assuming an intrinsic dispersion of 0.3 mag about the Hubble diagram for SN Ia. \newline Subject headings: Cepheids - distance scale - Galaxies:individual: NGC 5253 - Supernovae: individual:1895B, 1972E