Bibcode
Hammersley, P. L.; Cohen, M.; Garzón, F.; Mahoney, T.; López-Corredoira, M.
Bibliographical reference
Monthly Notices, Volume 308, Issue 2, pp. 333-363.
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9
1999
Citations
23
Refereed citations
19
Description
We analyse the stellar content of almost 300deg^2 of the sky close to
the Galactic plane by directly comparing the predictions of the SKY
model (Cohen and Wainscoat et al.) with star counts taken from the Two
Micron Galactic plane Survey (TMGS: Garzón et al.). Through these
comparisons we can examine discrepancies between counts and model and
thereby elicit an understanding of Galactic structure. Over the vast
majority of areas in which we have compared the TMGS data with the SKY
predictions we find very good accord; so good that we are able to remove
the disc source counts to highlight structure in the plane. The
exponential disc is usually dominant, but by relying on the predicted
disc counts of SKY we have been able to probe the molecular ring, spiral
arms, and parts of the bulge. The latter is clearly triaxial. We
recognize a number of off-plane dust clouds not readily included in
models. However, we find that, whilst the simple exponential extinction
function works well in the outer Galaxy, closer than about 4kpc to the
Galactic Centre the extinction drops dramatically. We also examine the
shape of the luminosity function of the bulge and argue that the cores
of all spiral arms we have observed contain a significant population of
supergiants that provides an excess of bright source counts over those
of a simple model of the arms. Analysis of one relatively isolated cut
through an arm near longitude 65 degrees categorically precludes any
possibility of a sech^2z stellar density function for the disc.