Astronomy and Astrophysics – Astrophysics
Scientific paper
2006-03-17
Astronomy and Astrophysics
Astrophysics
22 pages, 7 figures
Scientific paper
Aims. The extraplanar stellar populations of highly-inclined disk galaxies IC 2233, IC 5052, NGC 4631 and NGC 5023 are analyzed with the goal to quantify their vertical extent and structure. Methods. Based on the single-star photometry, we separate different stellar populations and analyze their spatial distribution. Results. On archival images obtained with the Hubble Space Telescope ACS/WFC the surroundings of these galaxies are well resolved into stars with the red giant population (RGB) identified far above the galaxy mid-planes. We find that there are a profound change in slope of the number density profile of the evolved RGB stars at extraplanar height of 4-8 kpc, that possibly reflects a truncation of the thick disk and reaching the 2-3 times more extended oblate stellar component (``the halo''). This structure is consistent with our previous studies of both edge-on and face-on disk galaxies in the Local Universe and allow us to improve the spatial model of the stellar components of a typical spiral galaxy. In NGC4631, the revealed asymmetry of its stellar thick disk and halo, is likely caused by the neighbor dwarf galaxy NGC4627. Based on the tip of the red giant branch method (TRGB) we estimated a distance of 10.42+/-0.38 Mpc for IC2233, 5.62+/-0.20 Mpc for IC5052, 7.11+/-0.13 Mpc for NGC4631 (6.70+/-0.15 for its satellite NGC4627) and 6.14+/-0.15 Mpc for NGC5023. We confirm the presence of slight extraplanar metallicity gradient of evolved stars at NGC5023 and IC5052, based on the systematic changes of the colour distribution of red giant stars.
Drozdovsky Igor O.
Galazutdinova O. A.
Tikhonov Nikolay A.
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