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2009MNRAS.396.1231R - Mon. Not. R. Astron. Soc., 396, 1231-1246 (2009/July-1)
The stellar population content of the thick disc and halo of the Milky way analogue NGC 891.
REJKUBA M., MOUHCINE M. and IBATA R.
Abstract (from CDS):
The colour-magnitude diagrams of thick disc and spheroid population are dominated by old red giant branch stars with a wide range of metallicities, from the sparsely populated metal-poor tail at [Fe/H] ∼ -2.4dex, up to about half-solar metallicity. The peak of the metallicity distribution function of the thick disc is at -0.9dex. The inner parts of the thick disc, within ∼14 kpc along the major axis show no vertical colour/metallicity gradient. In the outer parts, a mild vertical gradient of Δ(V - I)0/Δ|Z| = 0.1±0.05/kpc or less than 0.1 dex/kpc is detected, with bluer colours or more metal-poor stars at larger distances from the plane. This gradient is, however, accounted for by the mixing with the metal-poor halo stars. No metallicity gradient along the major axis is present for thick-disc stars, but strong variations of about 0.35 dex around the mean of [Fe/H] = -1.13dex are found. The properties of the asymmetric metallicity distribution functions of the thick-disc stars show no significant changes in both the radial and the vertical directions. The stellar populations situated within the solar-cylinder-like distances show strikingly different properties from those of the Galaxy populating similar distances. This suggests that the accretion histories of both galaxies have been different.
The spheroid population, composed of the inner spheroid and the halo, shows remarkably uniform stellar population properties. The median metallicity of the halo stellar population shows a shallow gradient from about -1.15dex in the inner parts to -1.27dex at 24 kpc distance from the centre, corresponding to ∼13reff. Similar to the thick-disc stars, large variations around the mean relation are present.
Abstract Copyright: © 2009 The Authors. Journal compilation © 2009 RAS
Journal keyword(s): galaxies: formation - galaxies: haloes - galaxies: individual: NGC 891 - galaxies: stellar content
VizieR on-line data: <Available at CDS (J/MNRAS/396/1231): table1.dat table2.dat>
Status at CDS : All or part of tables of objects will not be ingested in SIMBAD.
Simbad objects: 5
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