On dust irradiation in planetary nebulae in the context of survivability of ices

Yeghikyan, A. G.

doi:10.1016/j.molap.2017.06.002

Cited by 3 publications

(2 citation statements)

References 39 publications

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“…Taking this flux and making the same calculations as before, we found an average water photodesorbed column density of 3.7 × 10 15 molecules cm −2 in 1000 yr. This result is in line with Yeghikyan (2017) for a CR rate of 10 −13 -10 −14 s −1 in their models. Abdulgalil et al (2017) bombarded water ice with lowenergy electrons.…”

Section: Discussionsupporting

confidence: 90%

“…This is a low number compared to gasphase water abundance toward massive protostars ∼ 10 18 molecules cm −2 (Boonman et al 2000 andvan Dishoeck 2003) but in cold clouds, Zmuidzinas et al (1995) and Tauber et al (1996) have found that the gas-phase H 2 O abundance is low, ∼ 10 −8 to 10 −7 related to H 2 . Yeghikyan (2017), using the Cloudy code (Ferland et al 2013), calculated the effect of the irradiation on the abun-dance of water (ice and gas) in planetary nebulae (PN) for 1000 yr. They concluded that this abundance depends on the ionization rate of hydrogen by energetic particles like cosmic rays (CR).…”

Section: Discussionmentioning

confidence: 99%

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New measurements on water ice photodesorption and product formation under ultraviolet irradiation

Cruz-Díaz

Martín-Doménech

Moreno

et al. 2017

Monthly Notices of the Royal Astronomical Society

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The photodesorption of icy grain mantles has been claimed to be responsible for the abundance of gas-phase molecules toward cold regions. Being water a ubiquitous molecule, it is crucial to understand its role in photochemistry and its behavior under an ultraviolet field. We report new measurements on the UV-photodesorption of water ice and its H 2 , OH, and O 2 photoproducts using a calibrated quadrupole mass spectrometer. Solid water was deposited under ultra-high-vacuum conditions and then UV-irradiated at various temperatures starting from 8 K with a microwave discharged hydrogen lamp. Deuterated water was used for confirmation of the results. We found a photodesorption yield of 1.3 × 10 −3 molecules per incident photon for water, and 0.7 × 10 −3 molecules per incident photon for deuterated water at the lowest irradiation temperature, 8 K. The photodesorption yield per absorbed photon is given and comparison with astrophysical scenarios, where water ice photodesorption could account for the presence of gas-phase water toward cold regions in the absence of a thermal desorption process is addressed.

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Section: Discussionsupporting

confidence: 90%

Section: Discussionmentioning

confidence: 99%

New measurements on water ice photodesorption and product formation under ultraviolet irradiation

Cruz-Díaz

Martín-Doménech

Moreno

et al. 2017

Monthly Notices of the Royal Astronomical Society

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Astrochemistry as the basics of Astrobiology: from simplest molecules to bioindicatorsonexoplanets surfaces

Yeghikyan¹,

Observatory²

2018

ComBAO

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The problem of the origin of Life is discussed from the astrophysical point of view. Most biologists and geologists up to the present time believe that Life was originated on the Earth in some initial natural chemical pre-reactors, where a mixture of water, ammonia, methane containing species and some other substances, under the influence of an energy source like, e.g. lightning, turned into quite complex compounds such as amino acids and complex hydrocarbons. In fact, under conditions of the primordial Earth, it is not possible to obtain such pre-biological molecules by not-bio-chemical methods, as discussed in this paper. Instead, an astrophysical view of the problem of the origin of Life on the Earth is proposed and it is recalled that the biological evolution on the Earth was preceded by the chemical evolution of complex chemical compounds, mostly under extraterrestrial conditions, where it is only possible to form optically active amino acids, sugars and heavy hydrocarbons necessary for constructing the first pre-biomolecules. Then, according to a widespread point of view, they were brought to Earth by comets and dust between 4.5 and 3.8 billion years ago. Some part of the matter of comets landed unchanged during grazing collisions. Prebiotic complexes on the surface of the planet participate in the formation of a specific cover with a reflective spectrum (or color index), whose characteristic details can be tried to reveal by observation. The most promising bio-indicators at present are optically active amino acids and their derivatives, however, the existing observational capabilities are insufficient to identify them. More promising as (pre)biomarkers are the heavy hydrocarbons discussed in this article, in particular bitumen and isoprene hydrocarbons.

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Astrochemistry and Astrobiology over the last 20 years

Yeghikyan

2024

ComBAO

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A review of the achievements of astrochemistry and astrobiology over the past 20 years is given. Advances in astrochemistry in understanding the processes of emergence and survival high molecular weight chemical compounds are directly related to the conditions of prebiomolecules origin, like -amino acids and complex hydrocarbons. And if on the case of amino acids and hydrocarbons synthesis , the astrophysical picture seems quite clear, then on the case of the emergence of chiral amino acids, of which the proteins of living organisms are composed, there is no generally accepted point of view. Probably they occurred in certain photochemical transformations under the influence of circularly polarized radiation in the conditions of star formation regions of molecular clouds.

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On dust irradiation in planetary nebulae in the context of survivability of ices

Cited by 3 publications

References 39 publications

New measurements on water ice photodesorption and product formation under ultraviolet irradiation

New measurements on water ice photodesorption and product formation under ultraviolet irradiation

Astrochemistry as the basics of Astrobiology: from simplest molecules to bioindicatorsonexoplanets surfaces

Astrochemistry and Astrobiology over the last 20 years

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