Complex organic molecules in the Galactic Centre: the N-bearing family

Abstract

We present an unbiased spectral line survey toward the Galactic Centre (GC) quiescent giant molecular cloud (QGMC), G+0.693 using the GBT and IRAM 30 telescopes. Our study highlights an extremely rich organic inventory of abundant amounts of nitrogen (N)-bearing species in a source without signatures of star formation. We report the detection of 17 N-bearing species in this source, of which 8 are complex organic molecules (COMs). A comparison of the derived abundances relative to H 2 is made across various galactic and extragalactic environments. We conclude that the unique chemistry in this source is likely to be dominated by low-velocity shocks with X-rays/cosmic rays also playing an important role in the chemistry. Like previous findings obtained for O-bearing molecules, our results for N-bearing species suggest a more efficient hydrogenation of these species on dust grains in G+0.693 than in hot cores in the Galactic disk, as a consequence of the low dust temperatures coupled with energetic processing by X-ray/cosmic ray radiation in the GC.

Abundant Z-cyanomethanimine in the interstellar medium: paving the way to the synthesis of adenine

“…Both conformers have velocities of around ∼68 km s −1 , consistently with many other molecules observed towards this region (see e.g. Zeng et al 2018). The molecular ratio between the two conformers is [Z/E]=6.1±2.4.…”

“…The results of the fit are summarized in Table 2. We derived an excitation temperature of 8±2 K, very similar to that determined for other complex species in this region Zeng et al 2018), and a column density of (2.0±0.6)×10 14 cm −2 . We present in Table 1 the velocity integrated intensity ( ∫ T * A dv) of the identified transitions resulting from the fit.…”

“…The Z-isomer has a relatively high abundance of 1.5×10 −9 , which is comparable to those of other nitrogen-bearing species in this source such as CH 3 CN or HC 5 N and higher than those of e.g. CH 3 NCO and C 2 H 5 CN (Zeng et al 2018).…”

“…The observations were centered at the coordinates α(J2000.0)= 17 h 47 m 22 s and δ(J2000.0)= -28 • 21 ′ 27 ′′ . We refer to Zeng et al (2018) for more detailed information on the observations.…”

“…Many molecular species have been identified in this cloud, including some of prebiotic relevance such as complex organic molecules (COMs; Requena-Torres et al 2006Zeng et al 2018) and phosphorus-bearing species (Rivilla et al 2018). In particular, numerous nitrile molecules have been already detected in the source such as C 3 N, HC 3 N, HC 5 N, HC 7 N, CH 2 CN, CH 3 CN, CH 3 C 3 N, NH 2 CN and HOCN (Zeng et al 2018). This rich nitrile chemistry makes this source an excellent target to search for more complex nitriles, and in particular Z-HNCHCN.…”