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

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

Monthly Notices of the Royal Astronomical Society, Volume 402, Issue 2, pp. 713-723.

Advertised on:
2
2010
Number of authors
13
IAC number of authors
1
Citations
38
Refereed citations
31
Description
This study is an investigation of the stellar density profile of the Galactic disc in the anticentre direction. We select over 40000 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.
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