We report the first detection in the interstellar medium of N-cyanomethanimine (H2CNCN), the stable dimer of HCN of highest energy and the most complex organic molecule identified in space containing ...the prebiotically relevant NCN backbone. We have identified a plethora of a-type rotational transitions with 3 ≤ Jup ≤ 11 and Ka ≤ 2 that belong to this species toward the Galactic center G+0.693-0.027 molecular cloud, the only interstellar source showing the three cyanomethanimine isomers (including the Z- and E-isomers of C-cyanomethanimine, HNCHCN). We have derived a total column density for H2CNCN of (2.9 ± 0.1) × 1012 cm−2, which translates into a total molecular abundance with respect to H2 of (2.1 ± 0.3) × 10−11. We have also revisited the previous detection of E- and Z-HNCHCN and found a total C/N-cyanomethanimine abundance ratio of 31.8 ± 1.8 and a Z/E-HNCHCN ratio of 4.5 ± 0.2. While the latter can be explained on the basis of thermodynamic equilibrium, chemical kinetics are more likely responsible for the observed C/N-cyanomethanimine abundance ratio, where the gas-phase reaction between methanimine (CH2NH) and the cyanogen radical (CN) arises as the primary formation route.
Abstract We present the first detection in space of thionylimide (HNSO) toward the Galactic center molecular cloud G + 0.693-0.027, thanks to the superb sensitivity of an ultradeep molecular line ...survey carried out with the Yebes 40 m and IRAM 30 m telescopes. This molecule is the first species detected in the interstellar medium containing, simultaneously, N, S, and O. We have identified numerous K a = 0, 1, and 2 transitions belonging to HNSO covering from J up = 2 to J up =10, including several completely unblended features. We derive a molecular column density of N = (8 ± 1)×10 13 cm −2 , yielding a fractional abundance relative to H 2 of ∼6 × 10 −10 , which is about ∼37 and ∼4.8 times less abundant than SO and SO 2 , respectively. Although there are still many unknowns in the interstellar chemistry of NSO-bearing molecules, we propose that HNSO is likely formed through the reaction of the NSO radical and atomic H on the surface of icy grains, with alternative routes also deserving exploration. Finally, HNSO appears as a promising link between N, S, and O interstellar chemistry, and its discovery paves the route to the detection of a new family of molecules in space.
One of the most important tools to investigate the chemical history of our Galaxy and our own Solar System is to measure the isotopic fractionation of chemical elements. In the present study new ...astronomical observations devoted to the study of hydrogen and nitrogen fractionation (D/H and 14N/15N ratios) of molecules, towards massive star-forming regions in different evolutionary phases, have been presented. Moreover, a new detailed theoretical study of carbon fractionation, 12C/13C ratios, has been done. One of the main results was the confirmation that the 14N/15N ratio increases with the galactocentric distance, as predicted by stellar nucleosynthesis Galactic chemical evolution models. This work gives new important inputs on the understanding of local chemical processes that favor the production of molecules with different isotopes in star-forming regions.
One of the most important tools to investigate the chemical history of our Galaxy and our own Solar System is to measure the isotopic fractionation of chemical elements. This is the process that ...distributes the less abundant stable isotopes of an element in different molecules. The isotopic ratios are governed by two main processes: 1. chemical evolution of the whole Galaxy due to stellar nucleosynthesis; 2. local fractionation effects. In this Proceeding we report some results highlighting both processes towards massive star-forming regions.
Nitriles play a key role as molecular precursors in prebiotic experiments based on the RNA-world scenario for the origin of life. These chemical compounds could have been partially delivered to the ...young Earth from extraterrestrial objects, stressing the importance of establishing the reservoir of nitriles in the interstellar medium. We report here the detection towards the molecular cloud G+0.693−0.027 of several nitriles, including cyanic acid (HOCN), and three C
4
H
3
N isomers (cyanoallene, CH
2
CCHCN; propargyl cyanide, HCCCH
2
CN; and cyanopropyne (CH
3
CCCN), and the tentative detections of cyanoformaldehyde (HCOCN), and glycolonitrile (HOCH
2
CN). We have also performed the first interstellar search of cyanoacetaldehyde (HCOCH
2
CN), which was not detected. Based on the derived molecular abundances of the different nitriles in G+0.693−0.027 and other interstellar sources, we have discussed their formation mechanisms in the ISM. We propose that the observed HOCN abundance in G+0.693−0.027 is mainly due to surface chemistry and subsequent shock-induced desorption, while HCOCN might be mainly formed through gas-phase chemistry. In the case of HOCH
2
CN, several grain-surface routes from abundant precursors could produce it. The derived abundances of the three C
4
H
3
N isomers in G+0.693−0.027 are very similar, and also similar to those previously reported in the dark cold cloud TMC-1. This suggests that the three isomers are likely formed through gas-phase chemistry from common precursors, possibly unsaturated hydrocarbons (CH
3
CCH and CH
2
CCH
2
) that react with the cyanide radical (CN). The rich nitrile feedstock found towards G+0.693−0.027 confirms that interstellar chemistry is able to synthesize in space molecular species that could drive the prebiotic chemistry of the RNA-world.
Ionize Hard: Interstellar PO+ Detection Rivilla, Víctor M.; García De La Concepción, Juan; Jiménez-Serra, Izaskun ...
Frontiers in astronomy and space sciences,
04/2022, Volume:
9
Journal Article
Peer reviewed
Open access
We report the first detection of the phosphorus monoxide ion (PO
+
) in the interstellar medium. Our unbiased and very sensitive spectral survey toward the G+0.693–0.027 molecular cloud covers four ...different rotational transitions of this molecule, two of which (
J
= 1–0 and
J
= 2–1) appear free of contamination from other species. The fit performed, assuming local thermodynamic equilibrium conditions, yields a column density of
N
=(6.0 ± 0.7) × 10
11
cm
−2
. The resulting molecular abundance with respect to molecular hydrogen is 4.5 × 10
–12
. The column density of PO
+
normalized by the cosmic abundance of P is larger than those of NO
+
and SO
+
, normalized by N and S, by factors of 3.6 and 2.3, respectively. The
N
(PO
+
)/
N
(PO) ratio is 0.12 ± 0.03, more than one order of magnitude higher than that of
N
(SO
+
)/
N
(SO) and
N
(NO
+
)/
N
(NO). These results indicate that P is more efficiently ionized than N and S in the ISM. We have performed new chemical models that confirm that the PO
+
abundance is strongly enhanced in shocked regions with high values of cosmic-ray ionization rates (10
–15
− 10
–14
s
−1
), as occurring in the G+0.693–0.027 molecular cloud. The shocks sputter the interstellar icy grain mantles, releasing into the gas phase most of their P content, mainly in the form of PH
3
, which is converted into atomic P, and then ionized efficiently by cosmic rays, forming P
+
. Further reactions with O
2
and OH produces PO
+
. The cosmic-ray ionization of PO might also contribute significantly, which would explain the high
N
(PO
+
)/
N
(PO) ratio observed. The relatively high gas-phase abundance of PO
+
with respect to other P-bearing species stresses the relevance of this species in the interstellar chemistry of P.
The recent discovery of the nature and behavior of carbon atoms interacting with interstellar ices has prompted a number of investigations on the chemistry initiated by carbon accretion on icy ...interstellar dust. In this work, we expand the range of processes promoted by carbon accretion to the chemistry initiated by the interaction of this atom with ammonia (NH
) using quantum chemical calculations. We found that carbon addition to the ammonia molecule forms a rather stable radical, CNH
, that is easily hydrogenated. The complete hydrogenation network is later studied. Our calculations reveal that while conversion to simpler molecules like HCN and HNC is indeed a possible outcome promoted by H-abstraction reactions, methylamine is also easily formed (CH
NH
). In fact, the stability of methylamine against hydrogen abstraction makes this molecule the preferred product of the reaction network. Our results serve as a stepping stone toward the accurate modeling of C-addition reactions in realistic astrochemical kinetic models.
Abstract
We present the first detection of (
Z
)-1,2-ethenediol, (CHOH)
2
, the enol form of glycolaldehyde, in the interstellar medium toward the G+0.693−0.027 molecular cloud located in the ...Galactic Center. We have derived a column density of (1.8 ± 0.1) × 10
13
cm
−2
, which translates into a molecular abundance with respect to molecular hydrogen of 1.3 × 10
−10
. The abundance ratio between glycolaldehyde and (
Z
)-1,2-ethenediol is ∼5.2. We discuss several viable formation routes through chemical reactions from precursors such as HCO, H
2
CO, CHOH, or CH
2
CHOH. We also propose that this species might be an important precursor in the formation of glyceraldehyde (HOCH
2
CHOHCHO) in the interstellar medium through combination with the hydroxymethylene (CHOH) radical.
Context.
Theories of the origins of life propose that early cell membranes were synthesised from amphiphilic molecules simpler than phospholipids, such as fatty alcohols. The discovery in the ...interstellar medium (ISM) of ethanolamine, the simplest phospholipid head group, raises the question whether simple amphiphilic molecules are also synthesised in space.
Aims.
We investigate whether precursors of fatty alcohols are present in the ISM.
Methods.
To do this, we have carried out a spectral survey at 7, 3, 2 and 1 mm towards the Giant Molecular Cloud G+0.693-0.027 located in the Galactic centre using the IRAM 30 m and Yebes 40 m telescopes.
Results.
Here, we report the detection in the ISM of the primary alcohol
n
-propanol (in both conformers
Ga
-
n
-C
3
H
7
OH and
Aa
-
n
-C
3
H
7
OH), a precursor of fatty alcohols. The derived column densities of
n
-propanol are (5.5 ± 0.4) × 10
13
cm
−2
for the
Ga
conformer and (3.4 ± 0.3) × 10
13
cm
−2
for the
Aa
conformer, which imply molecular abundances of (4.1 ± 0.3) × 10
−10
for
Ga
-
n
-C
3
H
7
OH and of (2.5 ± 0.2) × 10
−10
for
Aa
-
n
-C
3
H
7
OH. We also searched for the
AGa
conformer of
n
-butanol
AGa
-
n
-C
4
H
9
OH without success, yielding an upper limit to its abundance of ≤4.1 × 10
−11
. The inferred CH
3
OH:C
2
H
5
OH:C
3
H
7
OH:C
4
H
9
OH abundance ratios are 1:0.04:0.006:≤0.0004 towards G+0.693-0.027, that is, they decrease roughly by one order of magnitude for increasing complexity. We also report the detection of both syn and anti conformers of vinyl alcohol, with column densities of (1.11 ± 0.08) × 10
14
cm
−2
and (1.3 ± 0.4) × 10
13
cm
−2
, and abundances of (8.2 ± 0.6) × 10
−10
and (9.6 ± 3.0) × 10
−11
, respectively.
Conclusions.
The detection of
n
-propanol, together with the recent discovery of ethanolamine in the ISM, opens the possibility that precursors of lipids according to theories of the origin of life, could have been brought to Earth from outer space.
The recent discovery of the nature and behavior of carbon atoms interacting with interstellar ices has prompted a number of investigations on the chemistry initiated by carbon accretion on icy ...interstellar dust. In this work, we expand the range of processes promoted by carbon accretion to the chemistry initiated by the interaction of this atom with ammonia (NH3) using quantum chemical calculations. We found that carbon addition to the ammonia molecule forms a rather stable radical, CNH3, that is easily hydrogenated. The complete hydrogenation network is later studied. Our calculations reveal that while conversion to simpler molecules like HCN and HNC is indeed a possible outcome promoted by H-abstraction reactions, methylamine is also easily formed (CH3NH2). In fact, the stability of methylamine against hydrogen abstraction makes this molecule the preferred product of the reaction network. Our results serve as a stepping stone toward the accurate modeling of C-addition reactions in realistic astrochemical kinetic models.
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