Gas-Phase CO in Protoplanetary Disks: A Challenge for Turbulent Mixing

2006 ◽  
Vol 647 (1) ◽  
pp. L57-L60 ◽  
Author(s):  
D. Semenov ◽  
D. Wiebe ◽  
Th. Henning
Keyword(s):  
Gas Phase ◽  
Turbulent Mixing ◽  
Protoplanetary Disks

scholarly journals Mixing and chemical reactions in a turbulent liquid mixing layer

1986 ◽  
Vol 170 ◽  
pp. 83-112 ◽  
Author(s):  
M. M. Koochesfahani ◽  
P. E. Dimotakis
Keyword(s):  
Reynolds Number ◽  
Gas Phase ◽  
Turbulent Mixing ◽  
High Speed ◽  
High Reynolds Number ◽  
Schmidt Number ◽  
Mixing Layer ◽  
Entrainment Ratio ◽  
High Reynolds ◽  
Mixed Fluid

An experimental investigation of entrainment and mixing in reacting and non-reacting turbulent mixing layers at large Schmidt number is presented. In non-reacting cases, a passive scalar is used to measure the probability density function (p.d.f.) of the composition field. Chemically reacting experiments employ a diffusion-limited acid–base reaction to directly measure the extent of molecular mixing. The measurements make use of laser-induced fluorescence diagnostics and high-speed, real-time digital image-acquisition techniques.Our results show that the vortical structures in the mixing layer initially roll-up with a large excess of fluid from the high-speed stream entrapped in the cores. During the mixing transition, not only does the amount of mixed fluid increase, but its composition also changes. It is found that the range of compositions of the mixed fluid, above the mixing transition and also throughout the transition region, is essentially uniform across the entire transverse extent of the layer. Our measurements indicate that the probability of finding unmixed fluid in the centre of the layer, above the mixing transition, can be as high as 0.45. In addition, the mean concentration of mixed fluid across the layer is found to be approximately constant at a value corresponding to the entrainment ratio. Comparisons with gas-phase data show that the normalized amount of chemical product formed in the liquid layer, at high Reynolds number, is 50% less than the corresponding quantity measured in the gas-phase case. We therefore conclude that Schmidt number plays a role in turbulent mixing of high-Reynolds-number flows.

scholarly journals Carbon-grain sublimation: a new top-down component to protostellar chemistry

2020 ◽  
Author(s):  
Merel van 't Hoff ◽  
Edwin Bergin ◽  
Jes Jorgensen ◽  
Geoffrey Blake
Keyword(s):  
Gas Phase ◽  
Formation Process ◽  
Organic Molecules ◽  
Planet Formation ◽  
Protoplanetary Disks ◽  
Excitation Temperature ◽  
Top Down ◽  
Carbon Chemistry ◽  
Episodic Nature ◽  
Protosolar Nebula

<p>One of the main goals in the fields of exoplanets and planet formation is to determine the composition of terrestrial, potentially habitable, planets and to link this to the composition of protoplanetary disks. A longstanding puzzle in this regard is the Earth's severe carbon deficit; Earth is 2-4 orders of magnitude depleted in carbon compared to interstellar grains and comets. The solution to this conundrum is that carbon must have been returned to the gas phase in the inner protosolar nebula, such that it could not get accreted onto the forming bodies. A process that could be responsible is the sublimation of carbon grains at the so-called soot line (~300 K) early in the planet-formation process. I will argue that the most likely signatures of this process are an excess of hydrocarbons and nitriles inside the soot line around protostars, and a higher excitation temperature for these molecules compared to oxygen-bearing complex organics that desorb around the water snowline (~100 K). Moreover, I will show that such characteristics have indeed been reported in the literature, for example, in Orion KL, although not uniformly, potentially due to differences in observational settings or related to the episodic nature of protostellar accretion. If this process is active, this would mean that there is an heretofore unrecognized component to the carbon chemistry during the protostellar phase that is acting from the top down - starting from the destruction of larger species - instead of from the bottom up from atoms. In the presence of such a top-down component, the origin of organic molecules needs to be re-explored. </p>

scholarly journals Laboratory data in support of JWST observations of interstellar ices

2019 ◽  
Vol 15 (S350) ◽  
pp. 420-421
Author(s):  
Marina G. Rachid ◽  
Jeroen Terwisscha van Scheltinga ◽  
Daniël Koletzki ◽  
Giulia Marcandalli ◽  
Ewine F. van Dishoeck ◽  
...  
Keyword(s):  
Solid State ◽  
Gas Phase ◽  
Organic Molecules ◽  
Methyl Formate ◽  
Laboratory Data ◽  
Protoplanetary Disks ◽  
Theoretical Studies ◽  
James Webb Space Telescope ◽  
Complex Organic ◽  
Experimental And Theoretical Studies

AbstractExperimental and theoretical studies have shown that Complex Organic Molecules (COMs) can be formed on icy dusty grains in molecular clouds and protoplanetary disks. The number of astronomical detections of solid COMs, however, is very limited. With the upcoming launch of the James Webb Space Telescope (JWST) this should change, but in order to identify solid state features of COMs, accurate laboratory data are needed. Here we present high resolution (0.5 cm–1) infrared ice spectra of acetone (C3H6O) and methyl formate (HCOOCH3), two molecules already identified in astronomical gas phase surveys, whose interstellar synthesis is expected to follow solid state pathways.

scholarly journals Laboratory constraints on ice formation, restructuring and desorption

2015 ◽  
Vol 11 (A29A) ◽  
pp. 309-312
Author(s):  
Karin I. Öberg
Keyword(s):  
Gas Phase ◽  
Chemical Reactions ◽  
Organic Molecules ◽  
Protoplanetary Disks ◽  
Ice Formation ◽  
Circumstellar Dust ◽  
Dust Grains ◽  
Complex Molecules ◽  
Detailed Understanding ◽  
Complex Organic

AbstractIces form on the surfaces of interstellar and circumstellar dust grains though freeze-out of molecules and atoms from the gas-phase followed by chemical reactions. The composition, chemistry, structure and desorption properties of these ices regulate two important aspects of planet formation: the locations of major condensation fronts in protoplanetary disks (i.e. snow lines) and the formation efficiencies of complex organic molecules in astrophysical environments. The latter regulates the availability of prebiotic material on nascent planets. With ALMA it is possible to directly observe both (CO) snowlines and complex organics in protoplanetary disks. The interpretation of these observations requires a detailed understanding of the fundamental ice processes that regulate the build-up, evolution and desorption of icy grain mantles. This proceeding reviews how experiments on thermal CO and N2 ice desorption, UV photodesorption of CO ice, and CO diffusion in H2O ice have been used to guide and interpret astrochemical observations of snowlines and complex molecules.

scholarly journals Water in Protoplanetary Disks

2012 ◽  
Vol 8 (S293) ◽  
pp. 235-237
Author(s):  
H. Nomura ◽  
C. Walsh ◽  
D. Heinzeller ◽  
T. J. Millar
Keyword(s):  
Turbulent Mixing ◽  
Line Emission ◽  
Protoplanetary Disks ◽  
Space Telescopes ◽  
Model Calculations ◽  
Water Line ◽  
Water Abundance ◽  
Size Growth ◽  
Abundance Profile ◽  
Grain Model

AbstractInfrared water line emission from protoplanetary disks, recently observed by the Spitzer and Herschel space telescopes, is thought to trace the surface layer of the inner to outer regions of the disks. We have modelled the water abundance profile and line emission, especially focusing on the effects of dust size growth and turbulent mixing. Comparison between model calculations and observations suggests a small grain model with turbulent mixing is preferred.

From disk midplanes to exoplanet atmospheres. The volatile chemical link.

2020 ◽  
Author(s):  
Christian Eistrup
Keyword(s):  
Chemical Composition ◽  
Gas Phase ◽  
Chemical Reactions ◽  
Chemical Evolution ◽  
Protoplanetary Disks ◽  
Solid Material ◽  
Comprehensive Treatment ◽  
Large Network ◽  
Grain Interaction ◽  
Grain Surface

<p>Exoplanetary science is now pushing to constrain the atmospheric compositions of exoplanets. This quest will be further aided by the next generation of facilities, such as the JWST and ground-based ELTs. Linking the observed composition of exoplanet atmospheres to where and how these atmospheres formed in their natal protoplanetary disks often involves comparing the observed exoplanetary atmospheric carbon-to-oxygen (C/O) ratio to a model of a disk midplane with a fixed chemical composition. In this scenario, chemical evolution in the midplane prior to and during the planet formation era is not considered. The C/O ratios of gas and ice in the disk midplane are simply defined by icelines of volatile molecules such as water and CO in the midplane. However, kinetic chemical evolution during the lifetime of the gaseous disk can change the relative abundances of volatile molecules, thus altering the C/O ratios of the planet-forming material. In my chemical evolution models, I utilize a large network of gas-phase, grain-surface and gas-grain interaction reactions, thus providing a comprehensive treatment of chemistry. In my talk, I will outline how such chemical reactions can cause the chemical composition in the disk midplane to evolve, how this affects the C/O ratios of the gas and solid material that form planets, and how such changes to the midplane chemical composition can lead to differences in exoplanet atmospheric compositions. These differences in exoplanet atmospheric compositions may be discernible with JWST observations.</p>

scholarly journals Muti-technique observations and modelling of the gas and dust phases of protoplanetary disks

2009 ◽  
Vol 5 (H15) ◽  
pp. 767-767
Author(s):  
C. Pinte ◽  
F. Ménard ◽  
G. Duchěne ◽  
J. C. Augereau
Keyword(s):  
Gas Phase ◽  
Observational Data ◽  
Large Scale ◽  
Scattered Light ◽  
Protoplanetary Disks ◽  
Quality Data ◽  
Data Sets ◽  
Wide Range ◽  
Dust Component ◽  
Chemical Conditions

A wide range of high-quality data is becoming available for protoplanetary disks. From these data sets many issues have already been addressed, such as constraining the large scale geometry of disks, finding evidence of dust grain evolution, as well as constraining the kinematics and physico-chemical conditions of the gas phase. Most of these results are based on models that emphasise fitting observations of either the dust component (SEDs or scattered light images or, more recently, interferometric visibilities), or the gas phase (resolved maps in molecular lines). In this contribution, we present a more global approach which aims at interpreting consistently the increasing amount of observational data in the framework of a single model, in order to to better characterize both the dust population and the gas disk properties, as well as their interactions. We present results of such modeling applied to a few disks (e.g. IM Lup, see Figure) with large observational data-sets available (scattered light images, polarisation maps, IR spectroscopy, X-ray spectrum, CO maps). These kinds of multi-wavelengths studies will become very powerful in the context of forthcoming instruments such as Herschel and ALMA.

scholarly journals WATER IN PROTOPLANETARY DISKS: DEUTERATION AND TURBULENT MIXING

2013 ◽  
Vol 779 (1) ◽  
pp. 11 ◽  
Author(s):  
Kenji Furuya ◽  
Yuri Aikawa ◽  
Hideko Nomura ◽  
Franck Hersant ◽  
Valentine Wakelam
Keyword(s):  
Turbulent Mixing ◽  
Protoplanetary Disks

Complex organic molecules tracing the comet-forming zones in protoplanetary disks

2019 ◽  
Vol 15 (S350) ◽  
pp. 463-464
Author(s):  
Catherine Walsh ◽  
John D. Ilee
Keyword(s):  
Gas Phase ◽  
Column Density ◽  
Organic Molecules ◽  
Rotational Temperature ◽  
Protoplanetary Disks ◽  
Independent Determination ◽  
Model Independent ◽  
Abundance And Distribution ◽  
Complex Organic

AbstractResolved emission from gas-phase methanol can reveal the abundance and distribution of the comet-forming ice reservoir in protoplanetary disks. ALMA Cycle 4 observations of four transitions of gas-phase methanol in TW Hya allow the first model-independent determination of the rotational temperature of methanol in a prototoplanetary disk. The data confirm that the methanol is rotationally cold (Trot < 50 K), and well constrain the column density to 2 × 1012 cm−2. Astrochemical models will constrain the chemical origin of methanol in TW Hya.

Sign in / Sign up

Export Citation Format

Share Document