Precursors of fatty alcohols in the ISM: Discovery of n-propanol

Theories on the origins of life propose that early cell membranes were synthesized 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 synthesized in space. We investigate whether precursors of fatty alcohols are present in the ISM. For this, we have carried out a spectral survey at 7, 3, 2 and 1 mm toward the Giant Molecular Cloud G+0.693-0.027 located in the Galactic Center using the IRAM 30m and Yebes 40m telescopes. Here, we report the detection in the ISM of the primary alcohol n-propanol (in both conformers Ga-n-C3H7OH and Aa-n-C3H7OH), a precursor of fatty alcohols. The derived column densities of n-propanol are (5.5+-0.4)x10^13 cm^-2 for the Ga conformer and (3.4+-0.3)x10^13 cm^-2 for the Aa conformer, which imply molecular abundances of (4.1+-0.3)x10^-10 for Ga-n-C3H7OH and of (2.5+-0.2)x10^-10 for Aa-n-C3H7OH. We also searched for the AGa conformer of n-butanol (AGa-n-C4H9OH) without success yielding an upper limit to its abundance of <4.1x10^-11. The inferred CH3OH:C2H5OH:C3H7OH:C4H9OH abundance ratios go as 1:0.04:0.006:<0.0004 toward G+0.693-0.027, i.e. 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)x10^14 cm^-2 and (1.3+-0.4)x10^13 cm^-2, and abundances of (8.2+-0.6)x10^-10 and (9.6+-3.0)x10^-11, respectively. 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.Comment: 15 pages, 10 figures, accepted for A&

Ionize Hard: Interstellar PO+ Detection

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 \ub1 0.7) 7 1011\ua0cm−2. The resulting molecular abundance with respect to molecular hydrogen is 4.5 7 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 \ub1 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 PH3, which is converted into atomic P, and then ionized efficiently by cosmic rays, forming P+. Further reactions with O2 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

Precursors of the RNA-world in space: Detection of (ZZ)-1,2-ethenediol in the interstellar medium, a key intermediate in sugar formation

We present the first detection of ($Z$)-1,2-ethenediol, (CHOH)$_2$, the enol form of glycolaldehyde, in the interstellar medium towards the G+0.693-0.027 molecular cloud located in the Galactic Center. We have derived a column density of (1.8$\pm$0.1)$\times$10$^{13}$ cm$^{-2}$, which translates into a molecular abundance with respect to molecular hydrogen of 1.3$\times$10$^{-10}$. The abundance ratio between glycolaldehyde and ($Z$)-1,2-ethenediol is $\sim$5.2. We discuss several viable formation routes through chemical reactions from precursors such as HCO, H$_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.Comment: Accepted for publication in The Astrophysical Journal Letter

Estudio de las primeras fases de la formación de los supercúmulos estelares

Tesis inédita de la Universidad Complutense de Madrid, Facultad de Ciencias Físicas, leída el 03-03-2022This thesis aims to study the earliest heavily obscured phases of massive star formation in starburst (SB) galaxies through a multi-line analysis of the HC3N rotational transitions from the ground and vibrationally excited states (HC3N*). Due to its unique spectroscopic properties, we also discuss the potential of HC3N* as a tool to discern whether the obscured nuclei of galaxies are being heated by a SB or by an accreting super massive black hole (i.e. an active galactic nucleus; AGN). Star formation is one of the most relevant physical processes in the formation and evolution of a galaxy. In particular, the energy released back (feedback) to their surrounding interstellar medium (ISM) from massive stars profoundly impacts the galaxy’s evolution. In a SB galaxy, most star formation takes place in the nucleus and in the form of compact massive star clusters known as superstar clusters (SSCs), which represent one of the most extreme models of star formation. Another major source of energy that can profoundly impact the ISM of a galaxy is an AGN. Both massive star formation and the AGN can reduce the star formation efficiency of a galaxy and even halt future star formation through feedback mechanisms. Hence, to study the physical conditions of the gas driving the formation of SSCs and shed light on the formation of massive stars, which is still not well understood, we need to observe the earliest phases of massive star formation before significant feedback intervenes...El objetivo de esta tesis es el estudio de las fases más tempranas y oscurecidas de la formación estelar masiva en galaxias con un brote de formación estelar (starburst; SB) mediante la emisión de HC3N proveniente de sus estados vibracionalmente excitados (HC3N*). Debido a las propiedades espectrales únicas de HC3N*, se estudia también su potencial como posible herramienta para discernir si los núcleos oscurecidos de galaxias están siendo calentados por un SB o por la acreción de un agujero negro súper masivo (AGN).La formación estelar es uno de los procesos más relevantes en la formación y evolución de galaxias. En particular, la energía que liberan (feedback) al medio interestelar (ISM) las estrellas masivas tiene un impacto profundo en la evolución de una galaxia. En las galaxias SB, la mayoría de esta formación estelar está localizada en el núcleo en forma de súper cúmulos de estrellas (SSCs), que representan uno de los modos más extremos de formación estelar. Otra fuente importante de energía en una galaxia que puede alterar su ISM es un AGN. Ambos, la formación estelar masiva y el AGN, pueden reducirla eficiencia de la formación estelar de una galaxia e incluso detenerla a través de su feedback. Por lo tanto, para estudiar las condiciones físicas del gas que está formando los SSCs y comprender mejor la formación de estrellas masivas, necesitamos observar las fases más tempranas de su formación, antes de que el feedback haya tenido lugar...Fac. de Ciencias FísicasTRUEunpu

Prebiotic Precursors of the Primordial RNA World in Space: Detection of NH2OH

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.With funding from the Spanish government through the "María de Maeztu Unit of Excellence" accreditation (MDM-2017-0737