Мақола

The inner halo of M 87: a first direct view of the red-giant population

S. BirdTuorla Observatory, University of Turku, Väsiäläntie 20, 21500 Piikkiö, FinlandW. E. HarrisDepartment of Physics and Astronomy, McMaster University, Hamilton L8S 4M1, CanadaJ. P. BlakesleeHerzberg Institute of Astrophysics, National Research Council of Canada, Victoria BC V9E 2E7, CanadaC. FlynnDepartment of Physics and Astronomy, University of Sydney, Sydney, Australia

2010en

ABI

Аннотация

An unusually deep (V,I) imaging dataset for the Virgo supergiant M 87 with the Hubble Space Telescope ACS successfully resolves its brightest red-giant stars, reaching MI(lim) = −2.5. After assessing the photometric completeness and biasses, we use this material to estimate the metallicity distribution for the inner halo of M 87, finding that the distribution is very broad and likely to peak near [m/H] ≃ −0.4 and perhaps higher. The shape of the MDF strongly resembles that of the inner halo for the nearby giant E galaxy NGC 5128. As a byproduct of our study, we also obtain a preliminary measurement of the distance to M 87 with the TRGB (red-giant branch tip) method; the result is (m − M)0 = 31.12±0.14 (d = 16.7±0.9 Mpc). Averaging this result with three other recent techniques give a weighted mean d(M87) = (16.4 ± 0.5) Mpc.

Ҳали таржима қилинмаган

Идентификаторлар

DOI: 10.1051/0004-6361/201014876

Иқтибослар ва манбалар

2 та иқтибос0 та фойдаланилган манба

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