Significance
The detection of ethanolamine (
N
H
2
C
H
2
C
H
2
OH) in a molecular cloud in the interstellar medium confirms that a precursor of phospholipids is efficiently formed by interstellar ...chemistry. Hence, ethanolamine could have been transferred from the proto-Solar nebula to planetesimals and minor bodies of the Solar System and thereafter to our planet. The prebiotic availability of ethanolamine on early Earth could have triggered the formation of efficient and permeable amphiphilic molecules such as phospholipids, thus playing a relevant role in the evolution of the first cellular membranes needed for the emergence of life.
Cell membranes are a key element of life because they keep the genetic material and metabolic machinery together. All present cell membranes are made of phospholipids, yet the nature of the first membranes and the origin of phospholipids are still under debate. We report here the presence of ethanolamine in space,
N
H
2
C
H
2
C
H
2
OH, which forms the hydrophilic head of the simplest and second-most-abundant phospholipid in membranes. The molecular column density of ethanolamine in interstellar space is
N
= (1.51
±
0.07)
×
10
13
c
m
−
2
, implying a molecular abundance with respect to
H
2
of
(
0.9
−
1.4
)
×
10
−
10
. Previous studies reported its presence in meteoritic material, but they suggested that it is synthesized in the meteorite itself by decomposition of amino acids. However, we find that the proportion of the molecule with respect to water in the interstellar medium is similar to the one found in the meteorite (
10
−
6
). These results indicate that ethanolamine forms efficiently in space and, if delivered onto early Earth, could have contributed to the assembling and early evolution of primitive membranes.
One of the proposed scenarios for the origin of life is the primordial RNA world, which considers that RNA molecules were likely responsible for the storage of genetic information and the catalysis ...of biochemical reactions in primitive cells, before the advent of proteins and DNA. In the last decade, experiments in the field of prebiotic chemistry have shown that RNA nucleotides can be synthesized from relatively simple molecular precursors, most of which have been found in space. An important exception is hydroxylamine, NH2OH, which, despite several observational attempts, it has not been detected in space yet. Here we present the first detection of NH2OH in the interstellar medium toward the quiescent molecular cloud G+0.693-0.027 located in the Galactic Center. We have targeted the three groups of transitions from the J = 2−1, 3−2, and 4−3 rotational lines, detecting five transitions that are unblended or only slightly blended. The derived molecular abundance of NH2OH is (2.1 0.9) × 10−10. From the comparison of the derived abundance of NH2OH and chemically related species, with those predicted by chemical models and measured in laboratory experiments, we favor the formation of NH2OH in the interstellar medium via hydrogenation of NO on dust grain surfaces, with possibly a contribution of ice-mantle NH3 oxidation processes. Further laboratory studies and quantum chemical calculations are needed to completely rule out the formation of NH2OH in the gas phase.
The chemical compounds carrying the thiol group (-SH) have been considered essential in recent prebiotic studies regarding the polymerization of amino acids. We have searched for this kind of ...compound toward the Galactic Center quiescent cloud G+0.693–0.027. We report the first detection in the interstellar space of the trans-isomer of monothioformic acid (t-HC(O)SH) with an abundance of ∼1 נ10−10. Additionally, we provide a solid confirmation of the gauche isomer of ethyl mercaptan (g-C2H5SH) with an abundance of ∼3 נ10−10, and we also detect methyl mercaptan (CH3SH) with an abundance of ∼5 נ10−9. Abundance ratios were calculated for the three SH-bearing species and their OH analogs, revealing similar trends between alcohols and thiols with increasing complexity. Possible chemical routes for the interstellar synthesis of t-HC(O)SH, CH3SH, and C2H5SH are discussed, as well as the relevance of these compounds in the synthesis of prebiotic proteins in the primitive Earth.
Galaxies with nuclear bars are believed to efficiently drive gas inward, generating a nuclear starburst and possibly an active galactic nucleus. We confirm this scenario for the isolated, ...double-barred, luminous infrared galaxy ESO 320-G030 based on an analysis of
Herschel
and ALMA spectroscopic observations.
Herschel
/PACS and SPIRE observations of ESO 320-G030 show absorption or emission in 18 lines of H
2
O, which we combine with the ALMA H
2
O 4
23
− 3
30
448 GHz line (
E
upper
∼ 400 K) and continuum images to study the physical properties of the nuclear region. Radiative transfer models indicate that three nuclear components are required to account for the multi-transition H
2
O and continuum data. An envelope, with radius
R
∼ 130 − 150 pc, dust temperature
T
dust
≈ 50 K, and
N
H2
∼ 2 × 10
23
cm
−2
, surrounds a nuclear disk with
R
∼ 40 pc that is optically thick in the far-infrared (
τ
100 μm
∼ 1.5 − 3,
N
H2
∼ 2 × 10
24
cm
−2
). In addition, an extremely compact (
R
∼ 12 pc), warm (≈100 K), and buried (
τ
100 μm
> 5,
N
H2
≳ 5 × 10
24
cm
−2
) core component is required to account for the very high-lying H
2
O absorption lines. The three nuclear components account for 70% of the galaxy luminosity (SFR ∼ 16 − 18
M
⊙
yr
−1
). The nucleus is fed by a molecular inflow observed in CO 2-1 with ALMA, which is associated with the nuclear bar. With decreasing radius (
r
= 450 − 225 pc), the mass inflow rate increases up to
Ṁ
inf
∼ 20
Ṁ
yr
−1
, which is similar to the nuclear star formation rate (SFR), indicating that the starburst is sustained by the inflow. At lower
r
, ∼100 − 150 pc, the inflow is best probed by the far-infrared OH ground-state doublets, with an estimated
Ṁ
inf
∼ 30
Ṁ
yr
−1
. The inferred short timescale of ∼20 Myr for nuclear gas replenishment indicates quick secular evolution, and indicates that we are witnessing an intermediate stage (< 100 Myr) proto-pseudobulge fed by a massive inflow that is driven by a strong nuclear bar. We also apply the H
2
O model to the
Herschel
far-infrared spectroscopic observations of H
2
18
O, OH,
18
OH, OH
+
, H
2
O
+
, H
3
O
+
, NH, NH
2
, NH
3
, CH, CH
+
,
13
CH
+
, HF, SH, and C
3
, and we estimate their abundances.
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.
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.
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.
Abstract
The Central Molecular Zone (CMZ) contains most of the mass of our Galaxy but its star formation rate is one order of magnitude lower than in the Galactic disk. This is likely related to the ...fact that the bulk of the gas in the CMZ is in a warm (>100 K) and turbulent phase with little material in the prestellar phase. We present in this Letter observations of deuterium fractionation (D/H ratios) of HCN, HNC, HCO
+
, and N
2
H
+
toward the CMZ molecular cloud G+0.693–0.027. These observations clearly show, for the first time, the presence of a colder, denser, and less turbulent narrow component, with a line width of ∼9 km s
−1
, in addition to the warm, less dense, and turbulent broad component with a line width of ∼20 km s
−1
. The very low D/H ratio ≤6 × 10
−5
for HCO
+
and N
2
H
+
, close to the cosmic value (∼2.5 × 10
−5
), and the high D/H ratios, >4 × 10
−4
for HCN and HNC, derived for the broad component confirm the presence of high-temperature deuteration routes for nitriles. For the narrow component we have derived D/H ratios >10
−4
and excitation temperatures of 7 K for all molecules, suggesting kinetic temperatures ≤30 K and H
2
densities ≥5 × 10
4
cm
−3
, at least one order of magnitude larger than that for the broad component. The method presented in this Letter allows us to identify clouds on the verge of star formation, i.e., under prestellar conditions, toward the CMZ. This method can also be used for the identification of such clouds in external galaxies.
Abstract
Amines, particularly primary amines (R-NH
2
), are closely related to the primordial synthesis of amino acids since they share the same structural backbone. However, only a limited number of ...amines has been identified in the interstellar medium, which prevents us from studying their chemistry as well as their relation to prebiotic species that could lead to the emergence of life. In this Letter, we report the first interstellar detection of vinylamine (C
2
H
3
NH
2
) and tentative detection of ethylamine (C
2
H
5
NH
2
) toward the Galactic center cloud G+0.693-0.027. The derived abundance with respect to H
2
is (3.3 ± 0.4) × 10
−10
and (1.9 ± 0.5) × 10
−10
, respectively. The inferred abundance ratios of C
2
H
3
NH
2
and C
2
H
5
NH
2
with respect to methylamine (CH
3
NH
2
) are ∼0.02 and ∼0.008, respectively. The derived abundance of C
2
H
3
NH
2
, C
2
H
5
NH
2
, and several other NH
2
-bearing species are compared to those obtained toward high-mass and low-mass star-forming regions. Based on recent chemical and laboratory studies, possible chemical routes for the interstellar synthesis of C
2
H
3
NH
2
and C
2
H
5
NH
2
are discussed.
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