Searching for the in-plane Galactic bar and ring in DENIS

Citation
M. Lopez-corredoira et al., Searching for the in-plane Galactic bar and ring in DENIS, ASTRON ASTR, 373(1), 2001, pp. 139-152
Citations number
64
Categorie Soggetti
Space Sciences
Journal title
ASTRONOMY & ASTROPHYSICS
ISSN journal
14320746 → ACNP
Volume
373
Issue
1
Year of publication
2001
Pages
139 - 152
Database
ISI
SICI code
1432-0746(200107)373:1<139:SFTIGB>2.0.ZU;2-#
Abstract
New evidence for a long thin Galactic bar (in contradistinction to the bulg e), as well as for the existence of the ring and the truncation of the inne r disc, are sought in the DENIS survey. First, we examine DENIS and Two Mic ron Galactic Survey star counts for the characteristic signatures of an in- plane bar and ring. The star counts in the plane for 30 degrees > l > 30 de grees are shown to be highly asymmetric with considerably more sources at p ositive than at negative longitudes. At \b \ approximate to 1.5 degrees, ho wever, the counts are nearly symmetric. Therefore, the asymmetry is not due to the disc, which is shown to have an inner truncation, or to the bulge, so there has to be another major component in the inner Galaxy that is caus ing the asymmetries. This component provides up to 50% of the detected sour ces in the plane between the bulge and l = 27 degrees or l = -14 degrees. T his component is shown to be consistent with an in-plane bar with a positio n angle of 40 degrees and half-length of 3.9 kpc. However, there is also a major peak in the counts at l = -22 degrees, which coincides with the tange ntial point of the so-called 3 kpc arm. This is shown to be most probably a ring or a pseudo-ring. The extinction in the plane is also shown to be asy mmetric with more extinction at negative than at positive longitudes. For l < 8<degrees> the extinction is shown to be slightly tilted with respect to b = 0 degrees in the same manner as the HI disc. We conclude that the Gala xy is a fairly typical ringed barred spiral galaxy.