Another bar in the Bulge

Abstract

Abstract.A map of the projected density of the old stellar population of the Galactic Bulge region is reconstructed using 2MASS data. By making a combination of the H and K photometric bands, it is possible to overcome the effect of reddening, and thus penetrate the inner structure of the Galactic Bulge. The main structure in the map corresponds to the well documented peanut shaped bar which is formed by the inner parts of the Galactic disk as a result of dynamical instabilities. As suggested by numerical simulations, the projected Z profile of the bar, has an almost exponential shape. After subtracting the exponential profile associated with the bar, a large residual appear near the Galactic Center. This residual is elongated and asymmetrical, which suggest a bar structure. Thus we arrive at the conclusion that in addition to the main bar a smaller bar with a different orientation may exist in the central region of the Milky Way. This finding makes the Milky Way very similar to a large number of barred spiral Galaxies which show as well a smaller bar in their central regions.

The long bar as seen by the VVV Survey

“…3.1, we have proposed a simple algorithm to correct the K s -band star counts from extinction, in which we only need the observed magnitudes in J and K s . There is some discussion of the method in the literature (e.g., Alard 2001;López-Corredoira et al 2001) or a similar method for redder wavelengths (e.g., M11), and the logic is clear: the average reddening is proportional to the extinction, thus the average (J − K s ) gives us information about the average extinction along the line of sight. In our case, looking at the central regions (| | ≤ 20 • , |b| < 2.5 • ) and excluding the sources with (J − K s ) < 0.5, the contribution of disk sources is low.…”

“…As realized by Sevenster et al (1999), the angle is around 25 • or lower when low latitudes are excluded from the fit, and around 40−45 • in the plane regions within −15 • < < 30 • . Furthermore, there A&A 559, A11 (2013) is some research on a possible third component, a nuclear bar (Alard 2001;Nishiyama et al 2005;González et al 2011) within | | < 4 • in the plane. Some of us think that this is a more uncertain structure, since it is very dependent on a correct subtraction of the bulge+long bar, the excess of very bright stars due to star forming regions in the inner bulge (López-Corredoira et al 2001b), or the errors affecting the distance of the red clump stars (see Appendix in LC01).…”

86 GHz SiO maser survey of late-type stars in the Inner Galaxy

“…To interpret the information given by the recent observations, detailed models all include some kind of tri-axiality: a tri-axial Galactic bulge or bar (e.g. Alard 2001;Debattista et al 2002;López-Corredoira et al 2001a,b;Ortwin 2002). However, the bar characteristics such as length, pattern speed, and position angle, are still poorly constrained.…”

Molecular gas and star formation in the Milky Way

“…In the 2MASS stellar counts, a nuclear bar has been found by Alard (2001) [1], and a CO nuclear bar corresponds (Sawada et al 2004 [28]). New simulations of gas flow in a two-bar models have been done by Rodriguez-Fernandez & Combes (2008) [25], who find a best fit when the two bars are nearly perpendicular, and the bar-spiral pattern is about 35 km/s/kpc (similar to Fux, 1999 [13]).…”