Open AccessNear‐infrared star counts as a test of a Galactic bar structure
Author(s) -
Unavane M.,
Gilmore Gerard
Publication year - 1998
Publication title -
monthly notices of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.058
H-Index - 383
eISSN - 1365-2966
pISSN - 0035-8711
DOI - 10.1046/j.1365-8711.1998.29511267.x
Subject(s) - physics , astrophysics , milky way , longitude , photometry (optics) , magnitude (astronomy) , bulge , asymmetry , astronomy , galactic center , absolute magnitude , apparent magnitude , extinction (optical mineralogy) , latitude , galaxy , stars , quantum mechanics , optics
We present survey data in the narrow‐band L filter (nb L ), taken at UKIRT, for a total area of 277 arcmin 2 , roughly equally divided between four regions at zero Galactic latitude and longitudes ??4.??3 and ??2.??3. The 80 per cent completeness level for these observations is at roughly magnitude 11.0. This magnitude limit, owing to the low coefficient for interstellar extinction at this wavelength ( A nb L =0.047 A V ), allows us to observe bulge giants. We match the nb L magnitudes with DENIS survey K magnitudes, and find 95 per cent of nb L sources are matched to K sources. Constructing colour–magnitude diagrams, we deredden the magnitudes and find evidence for a longitude‐dependent asymmetry in the source counts. We find that there are ∼15 per cent and ∼5 per cent more sources at the negative longitude than at the corresponding positive longitude for the fields at ??4.??3 and ??2.??3, respectively. This is compared with the predictions of some Galactic bar models. We find an asymmetry in the expected sense, which favours gas dynamical models and the recent deconvolution of surface photometry data over earlier treatments of photometric data.