The Central 300 pc of the Galaxy Probed by Infrared Spectra of H$_3^+$ and CO: III. Locations of Sgr B2 and Star $iota$. (arXiv:2111.05915v1 [astro-ph.GA])
<a href="http://arxiv.org/find/astro-ph/1/au:+Oka_T/0/1/0/all/0/1">Takeshi Oka</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Geballe_T/0/1/0/all/0/1">T. R. Geballe</a>
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$. To do this we use velocity profiles of
the infrared absorption spectrum of H$_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$. Our conclusion that Sgr B2 lies toward the rear of the CMZ is
contrary to most previous models in which it has been placed shallower than
Sgr~A$^ast$.
Using a simple relation between the radial expansion velocity of diffuse gas
in the Central Molecular Zone (CMZ) of the Galaxy and its distance from
Sgr~A$^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$. To do this we use velocity profiles of
the infrared absorption spectrum of H$_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$. Our conclusion that Sgr B2 lies toward the rear of the CMZ is
contrary to most previous models in which it has been placed shallower than
Sgr~A$^ast$.
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