The Infrared Surface Brightness Fluctuation Distances to the Hydra and Coma Clusters 1 Joseph B. Jensen John L. Tonry and Gerard A. Luppino Institute for Astronomy, UniversityofHawaii 2680 Woodlawn Drive, Honolulu, HI 96822 e-mail:
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[email protected] ABSTRACT We present IR surface brightness uctuation (SBF) distance measurements to NGC 4889 in the Coma cluster and to NGC 3309 and NGC 3311 in the Hydra cluster. We explicitly corrected for the contributions to the uctuations from globular clusters, background galaxies, and residual background variance. We measured a distance of 85 10 Mp c to NGC 4889 and a distance of 46 5 Mp c to the Hydra cluster. 1 1 Adopting recession velo cities of 7186 428 km s for Coma and 4054 296 km s 1 1 for Hydra gives a mean Hubble constantofH =87 11km s Mp c . Corrections 0 for residual variances were a signi cant fraction of the SBF signal measured, and, if underestimated, would bias our measurementtowards smaller distances and larger values of H . Both NICMOS on the Hubble Space Telescop e and large-ap erture 0 ground-based telescop es with new IR detectors will make accurate SBF distance measurements p ossible to 100 Mp c and b eyond. Subject headings: distance scale | galaxies: clusters: individual (Hydra, Coma) | galaxies: individual (NGC 3309, NGC 3311, NGC 4889) | galaxies: distances and redshifts 1. Intro duction Measuring accurate and reliable distances is a critical part of the quest to measure the Hubble constant H .Until recently, di erenttechniques for estimating extragalactic distances 0 1 Currently with the Gemini 8-m Telescop es Pro ject, 180 Kino ole St.