English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

The chemical differentiation of seven COMs in the extended region around SgrB2 has been observed: CH$_2$OHCHO, CH$_3$OCHO, t-HCOOH, C$_2$H$_5$OH, andCH$_3$NH$_2$ were detected both in the extended region and near the hot coresSgr B2(N) and Sgr B2(M), while CH$_3$OCH$_3$ and C$_2$H$_5$CN were onlydetected near the hot cores. The density and temperature in the extended regionare relatively low. Different desorption mechanisms have been proposed toexplain the observed COMs in cold regions but fail to explain the deficiency ofCH$_3$OCH$_3$ and C$_2$H$_5$CN. We explored under what physical conditions thechemical simulations can fit the observations and explain the different spatialdistribution of these species. We used the Monte Carlo method to perform adetailed parameter space study. We investigated how different mechanisms affectthe results. All gas-grain chemical models based on static physics cannot fitthe observations. The results based on evolving physical conditions can fit sixCOMs when $T\sim30-60$ K, but the best-fit temperature is still higher than theobserved dust temperature of 20 K. The best agreement at $T\sim27$ K isachieved by considering a short-duration $\sim 10^2$ yr X-ray burst with$\zeta_{\mathrm{CR}}=1.3\times10^{-13}$ s$^{-1}$ when the temperature is 20 K.The reactive desorption is the key mechanism for producing these COMs andinducing the low abundances of CH$_3$OCH$_3$ and C$_2$H$_5$CN. The evolution ofthe extended region around Sgr~B2 may have begun with a cold, $T\le10$ K phasefollowed by a warm-up phase. When its temperature reached $T\sim20$ K, an X-rayflare from Sgr A* with a short duration of no more than 100 years was acquired,affecting strongly the Sgr B2 chemistry. The observed COMs retain theirobserved abundances only several hundred years after such a flare, which couldimply that such short-term X-ray flares occur relatively often.

Chemical modeling of the complex organic molecules in the extended region around Sagittarius B2