The Central 300 pc of the Galaxy Probed by Infrared Spectra of H${}_3^{+}$ and CO: III. Locations of Sgr B2 and Star $\iota$

Abstract

Using a simple relation between the radial expansion velocity of diffuse gas in the Central Molecular Zone (CMZ) of the Galaxy and its distance from Sgr A${}^{\ast }$ we estimate the physical depths within the CMZ of Star $\iota$ (2MASS $J$17470898-2829561) and two Sgr B2 far-infrared continuum sources with respect to the location of Sgr A${}^{\ast }$. To do this we use velocity profiles of mid-infrared absorption lines of H${}_3^{+}$ and of far-infrared absorption lines of H${}_2$O${}^{+}$, OH${}^{+}$, and ${}^{13}$CH${}^{+}$. The distances to Star $\iota$ and to the Sgr B2 sources are found to be $\sim$90 pc greater than the distance to Sgr A${}^{\ast }$. Our conclusion that Sgr B2 lies toward the rear of the CMZ is contrary to many previous models in which it has been placed shallower than Sgr A${}^{\ast }$.

9 pages, 10 figures. Accepted by ApJ

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Cited by in corpus (2)

• Three-Dimensional Structure of the Central Molecular Zone
• Living on the edge of the Central Molecular Zone: G1.3 is the more likely candidate for gas accretion into the CMZ