Journal Article

The structure of the outer Galactic disc as revealed by IPHAS early A stars

S. E. Sale, J. E. Drew, C. Knigge, A. A. Zijlstra, M. J. Irwin, R. A. H. Morris, S. Phillipps, J. J. Drake, R. Greimel, Y. C. Unruh, P. J. Groot, A. Mampaso and N. A. Walton

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 402, issue 2, pages 713-723
Published in print February 2010 | ISSN: 0035-8711
Published online February 2010 | e-ISSN: 1365-2966 | DOI: http://dx.doi.org/10.1111/j.1365-2966.2009.15746.x
The structure of the outer Galactic disc as revealed by IPHAS early A stars

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This study is an investigation of the stellar density profile of the Galactic disc in the anticentre direction. We select over 40 000 early A stars from INT/WFC Photometric Hα Survey of the Northern Galactic Plane (IPHAS) photometry in the Galactic longitude range 160° < l < 200° close to the equatorial plane (−1° < b < +1°). We then compare their observed reddening-corrected apparent magnitude distribution with simulated photometry obtained from parametrized models in order to set constraints on the anticentre stellar density profile. By selecting A stars, we are appraising the properties of a population only ∼100 Myr old. We find that the stellar density profile of young stars is well fit to an exponential with length-scale of (3020 ± 120statistical± 180systematic) pc, which is comparable to that obtained in earlier studies, out to a Galactocentric radius of RT= (13.0 ± 0.5statistical± 0.6systematic) kpc. At larger radii, the rate of decline appears to increase with the scalelength dropping to (1200 ± 300statistical± 70systematic) pc. This result amounts to a refinement of the conclusions reached in previous studies that the stellar density profile is abruptly truncated. The IPHAS A star data are not compatible with models that propose a sudden change in metallicity at RG= 10 kpc.

Keywords: surveys; Galaxy: abundances; Galaxy: disc; Galaxy: stellar content; Galaxy: structure

Journal Article.  9102 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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