Chemical Features in the Circumnuclear Disk of the Galactic Center

The circumnuclear disk (CND) of the Galactic Center is exposed to many energetic phenomena coming from the supermassive black hole Sgr A* and stellar activities. These energetic activities can affect the chemical composition in the CND by the interaction with UV-photons, cosmic-rays, X-rays, and shock waves. We aim to constrain the physical conditions present in the CND by chemical modeling of observed molecular species detected towards it. We analyzed a selected set of molecular line data taken toward a position in the southwest lobe of the CND with the IRAM 30m and APEX 12-meter telescopes and derived the column density of each molecule using a large velocity gradient (LVG) analysis. The determined chemical composition is compared with a time-dependent gas-grain chemical model based on the UCL\_CHEM code that includes the effects of shock waves with varying physical parameters. Molecules such as CO, HCN, HCO$^+$, HNC, CS, SO, SiO, NO, CN, H$_2$CO, HC$_3$N, N$_2$H$^+$ and H$_3$O$^+$ are detected and their column densities are obtained. Total hydrogen densities obtained from LVG analysis range between $2 \times 10^4$ and $1 \times 10^6\,$cm$^{-3}$ and most species indicate values around several $\times 10^5\,$cm$^{-3}$, which are lower than values corresponding to the Roche limit, which shows that the CND is tidally unstable. The chemical models show good agreement with the observations in cases where the density is $\sim10^4\,$cm$^{-3}$, the cosmic-ray ionization rate is high, $>10^{-15} \,$s$^{-1}$, or shocks with velocities $> 40\,$km s$^{-1}$ have occurred. Comparison of models and observations favors a scenario where the cosmic-ray ionization rate in the CND is high, but precise effects of other factors such as shocks, density structures, UV-photons and X-rays from the Sgr A* must be examined with higher spatial resolution data.Comment: 17 Pages, 13 figures, accepted for publication in A&

Synthesis of the marine natural product N-alpha-(4-bromopyrrolyl-2-carbonyl)-L-homoarginine, a putative biogenetic precursor of the pyrrole-imidazole alkaloids

Lysine is proposed as an alternative biosynthetic precursor of the pyrrole-imidazole alkaloids frequently found in marine sponges. As a putative key intermediate, the natural product N-alpha-(4-bromopyrrolyl-2-carbonyl)-L-homoarginine (1) from the sponge Agelas wiedenmayeri was synthesized in the solid phase starting from the Fmoc/Pmc-protected L-homoarginine and in solution starting from readily available L-lysine methyl ester

Clean Beam Patterns with Low Crosstalk Using 850 GHz Microwave Kinetic Inductance Detectors

We present modeling of distributed λ /4 microwave kinetic inductance detectors (MKIDs) showing how electromagnetic cross coupling between the MKID resonators can occur at frequencies corresponding to the microwave readout signal (∼ 4–8 GHz). We then show system beam pattern measurements in the reimaged focal plane of a 72 detector array of lens–antenna coupled MKIDs at 850 GHz, which enables a direct measure of any residual optical crosstalk. With use of transmission line bridges we see no residual cross coupling between MKIDs and hence low crosstalk down to the − 30 dB level, with near Gaussian shape (limited by reimaging optics) to − 10 dB level