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2010 CFHT Users Meeting
November 16-18, 2010
ASIAA Auditorium, Taipei, Taiwan

Poster Presentation

Cepheids and Long Period Variables in NGC 4258

Author(s): Samantha Hoffmann (Texas A & M), Lucas Macri (Texas A & M), Chow-Choong Ngeow (NCU), Shashi Kanbur (SUNY-Oswego)

Presenter: Chow Choong Ngeow (National Central University)

NGC 4258, a nearby (D=7.2Mpc) spiral galaxy, serves as the "anchor" or first rung in the Extragalactic Distance Scale thanks to a very precise and accurate geometric distance estimate based on maser observations. We have imaged NGC 4258 with Gemini from 2004 to 2007 and discovered a large number of long-period Cepheids, extending the upper period range of the previously-existing HST Period-Luminosity (P-L) relation from 45 to 150 days. In addition, we discovered numerous long-period variables (LPVs) with periods up to 900 days. These variables have the potential to be excellent distance indicators in the near-infrared, which is highly relevant for the JWST era. Queued observations of NGC 4258 with CFHT have been carried out in 2010A Semester, for a total of 4 hours. Our CFHT observations will be used to (i) obtain more robust periods for the variables and provide updated phase information in support of ongoing HST observations at H band; (ii) carry out a search for ultra-long period Cepheids in this galaxy; (iii) tie the existing Gemini observations to the Sloan magnitude system, to obtain accurate magnitudes and colors for these important variables. We present preliminary results for the study of Cepheids and long period variables in NGC 4258 based on the Gemini and CFHT data.

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