NGC 4258 plays a crucial role in the Extragalactic Distance Scale because it is the only nearby galaxy with a very accurate and precise distance measurement (3% total uncertainty). We present results from recent HST observations of Cepheids in this galaxy, obtained as part of the SH0ES project. By combining ACS and WFPC2 observations from Cycles 12, 13 and 15, we have been able to discover long‐period Cepheids with periods up to 130 days.

We also summarize the results nd future plans of the SH0ES project to characterize the properties of Cepheids in NGC 4258 and hosts of “ideal” type Ia SNe, with the aim of estimating the Hubble constant with a total uncertainty below 5%.

Topics
Hubble's law, Nearby galaxies, Cepheid variables
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© 2009 American Institute of Physics.
2009
American Institute of Physics
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