RR Lyrae Variables in M33. I. Evidence For a Field Halo Population

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dc.creatorSarajedini, Ata
dc.creatorBarker, M. K.
dc.creatorGeisler, Doug
dc.creatorHarding, Paul
dc.creatorSchommer, Robert
dc.date2006-05-23
dc.date.accessioned2026-07-07T11:25:37Z
dc.date.available2026-07-07T11:25:37Z
dc.descriptionWe present observations of RR Lyrae variables in the Local Group late-type spiral galaxy M33. Using the Advanced Camera for Surveys on the Hubble Space Telescope, we have identified 64 ab-type RR Lyraes in M33. We have estimated reddenings for these stars based on their minimum light V-I colors and metallicities based on their periods. From the distributions of these properties, we conclude that the RR Lyraes belong to two populations - one associated with the halo of M33 and the other with its disk. Given that RR Lyraes are produced by populations older than ~10 Gyr, this suggests that not only does the field halo of M33 contain an old component, but so does its disk. This is one of the best pieces of evidence for the existence of a halo field component in M33. Using a relation between RR Lyrae absolute magnitude and metallicity (Mv(RR) = 0.23[Fe/H] + 0.93), we estimate a mean distance modulus of <(m-M)o> = 24.67 +/- 0.08 for M33. This places M33 approximately 70 kpc beyond M31 in line-of-sight distance.
dc.description20 pages, 17 figures, accepted for publication in The Astronomical Journal
dc.identifierhttps://arxiv.org/abs/astro-ph/0605580
dc.identifierhttp://arxiv.org/abs/astro-ph/0605580
dc.identifierAstron.J.132:1361-1371,2006
dc.identifierdoi:10.1086/506152
dc.identifier.urihttp://salesiana.dossiersoluciones.com/handle/123456789/195564
dc.subjectAstrophysics
dc.titleRR Lyrae Variables in M33. I. Evidence For a Field Halo Population
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