arXiv subjects

Jes K. Jørgensen

Publications and source records attributed to Jes K. Jørgensen.

At least 55 records · Page 3Linked to original sources

arXiv2022

Rotational spectroscopy of mono-deuterated oxirane ($c$-C$_2$H$_3$DO) and its detection towards IRAS 16293$-$2422 B

We prepared a sample of mono-deuterated oxirane and studied its rotational spectrum in the laboratory between 490 GHz and 1060 GHz in order to improve its spectroscopic parameters and consequently the calculated rest frequencies of its rotational transitions. The updated rest frequencies were employed to detect $c$-C$_2$H$_3$DO for the first time in the interstellar medium in the Atacama Large Millimetre/submillimetre Array (ALMA) Protostellar Interferometric Line Survey (PILS) of the Class 0 protostellar system IRAS 16293$-$2422. Fits of the detected lines using the rotation diagrams yield a temperature of $T_{\rm rot} = 103 \pm 19$ K, which in turn agrees well with 125 K derived for the $c$-C$_2$H$_4$O main isotopologue previously. The $c$-C$_2$H$_3$DO to $c$-C$_2$H$_4$O ratio is found to be $\sim$0.15 corresponding to a D-to-H ratio of $\sim$0.036 per H atom which is slightly higher than the D-to-H ratio of species such as methanol, formaldehyde, ketene and but lower than those of the larger complex organic species such as ethanol, methylformate and glycolaldehyde. This may reflect that oxirane is formed fairly early in the evolution of the prestellar cores. The identification of doubly deuterated oxirane isotopomers in the PILS data may be possible judged by the amount of mono-deuterated oxirane and the observed trend that multiply deuterated isotopologues have higher deuteration rates than their mono-deuterated variants.

astro-ph.GA↗

arXiv2022

A VLA View of the Flared, Asymmetric Disk Around the Class 0 Protostar L1527 IRS

We present high resolution Karl G. Jansky Very Large Array (VLA) observations of the protostar L1527 IRS at 7 mm, 1.3 cm, and 2 cm wavelengths. We detect the edge-on dust disk at all three wavelengths and find that it is asymmetric, with the southern side of the disk brighter than the northern side. We confirm this asymmetry through analytic modeling and also find that the disk is flared at 7 mm. We test the data against models including gap features in the intensity profile, and though we cannot rule such models out, they do not provide a statistically significant improvement in the quality of fit to the data. From these fits, we can however place constraints on allowed properties of any gaps that could be present in the true, underlying intensity profile. The physical nature of the asymmetry is difficult to associate with physical features due to the edge-on nature of the disk, but could be related to spiral arms or asymmetries seen in other imaging of more face-on disks.

astro-ph.SR↗

arXiv2022

The young embedded disk L1527 IRS: constraints on the water snowline and cosmic ray ionization rate from HCO+ observations

The water snowline in circumstellar disks is a crucial component in planet formation, but direct observational constraints on its location remain sparse due to the difficulty of observing water in both young embedded and mature protoplanetary disks. Chemical imaging provides an alternative route to locate the snowline, and HCO$^+$ isotopologues have been shown to be good tracers in protostellar envelopes and Herbig disks. Here we present $\sim$0.5$^{\prime\prime}$ resolution ($\sim$35 au radius) Atacama Large Millimeter/submillimeter Array (ALMA) observations of HCO$^+$ $J=4-3$ and H$^{13}$CO$^+$ $J=3-2$ toward the young (Class 0/I) disk L1527 IRS. Using a source-specific physical model with the midplane snowline at 3.4 au and a small chemical network, we are able to reproduce the HCO$^+$ and H$^{13}$CO$^+$ emission, but for HCO$^+$ only when the cosmic ray ionization rate is lowered to $10^{-18}$ s$^{-1}$. Even though the observations are not sensitive to the expected HCO$^+$ abundance drop across the snowline, the reduction in HCO$^+$ above the snow surface and the global temperature structure allow us to constrain a snowline location between 1.8 and 4.1 au. Deep observations are required to eliminate the envelope contribution to the emission and to derive more stringent constraints on the snowline location. Locating the snowline in young disks directly with observations of H$_2$O isotopologues may therefore still be an alternative option. With a direct snowline measurement, HCO$^+$ will be able to provide constraints on the ionization rate.

astro-ph.SR↗

arXiv2022

The prebiotic molecular inventory of Serpens SMM1: II. The building blocks of peptide chains

This work aims to constrain the abundances of interstellar amides, by searching for this group of prebiotic molecules in the intermediate-mass protostar Serpens SMM1-a. ALMA observations are conducted toward Serpens SMM1. A spectrum is extracted toward the SMM1-a position and analyzed with the CASSIS line analysis software for the presence of characteristic rotational lines of a number of amides and other molecules. NH$_{2}$CHO, NH$_{2}$CHO $ν_{12}$=1, NH$_{2}^{13}$CHO, CH$_{3}$C(O)NH$_{2}$ $ν$=0,1, CH$_{2}$DOH, CH$_{3}$CHO, and CH$_{3}$C(O)CH$_{3}$ are securely detected, while trans-NHDCHO, NH$_{2}$CDO, CH$_{3}$NHCHO $ν$=0,1, CH$_{3}$COOH, and HOCH$_{2}$CHO are tentatively identified. The results of this work are compared with detections presented in the literature. A uniform CH$_{3}$C(O)NH$_{2}$/NH$_{2}$CHO ratio is found for a group of interstellar sources with vast physical differences. A similar ratio is seen for CH$_{3}$NHCHO, based on a smaller data sample. The D/H ratio of NH$_{2}$CHO is about 1--3\% and is close to values found in the low-mass source IRAS~16293--2422B. The formation of CH$_{3}$C(O)NH$_{2}$ and NH$_{2}$CHO is likely linked. Formation of these molecules on grain surfaces during the dark cloud stage is a likely scenario. The high D/H ratio of NH$_{2}$CHO is also seen as an indication that these molecules are formed on icy dust grains. As a direct consequence, amides are expected to be present in the most pristine material from which planetary systems form, thus providing a reservoir of prebiotic material.

astro-ph.GA↗

arXiv2022

Successive deuteration in low-mass star-forming regions: the case of D$_{2}$-methanol (CHD$_{2}$OH) in IRAS 16293-2422

Accurate quantification of the column density of di-deuterated methanol is a key missing puzzle piece in the otherwise thoroughly constrained family of D-bearing methanol in the deeply embedded low-mass protostellar system and astrochemical template source IRAS16293-2422. A spectroscopic dataset for astrophysical purposes is built for CHD$_{2}$OH and made publicly available to facilitate accurate characterization of this species in astrochemical surveys. The newly computed line list and partition function are used to search for CHD$_{2}$OH towards IRAS16293-2422 A and B in data from ALMA-PILS. Only non-blended, optically thin lines of CHD$_{2}$OH are used for the synthetic spectral fitting. The constructed spectroscopic database contains line frequencies and strengths for 7417 transitions in the 0 to 500 GHz frequency range. ALMA-PILS observations in the 329-363 GHz range are used to identify 105 unique, non-blended, optically thin line frequencies of CHD$_{2}$OH for synthetic spectral fitting. The derived excitation temperatures and column densities yield high D/H ratios of CHD$_{2}$OH in IRAS 16293-2422 A and B of 7.5$\pm$1.1% and 7.7$\pm$1.2%, respectively. Deuteration in IRAS 16293-2422 is not higher than in other low-mass star-forming regions. Di-deuterated molecules consistently have higher D/H ratios than their monodeuterated counterparts in all low-mass protostars, which may be a natural consequence of H-D substitution reactions as seen in laboratory experiments. The Solar System's natal cloud, as traced by comet 67P/Churyumov-Gerasimenko, may have had a lower initial abundance of D, been warmer than the cloud of IRAS16293-2422, or been partially reprocessed. In combination with accurate spectroscopy, a careful spectral analysis, and a consideration of the underlying assumptions, successive deuteration is a robust window on the physicochemical provenance of star-forming systems.

astro-ph.GA↗

arXiv2021

A cold accretion flow onto one component of a multiple protostellar system

Context: Gas accretion flows transport material from the cloud core onto the protostar. In multiple protostellar systems, it is not clear if the delivery mechanism is preferential or evenly distributed among the components. Aims: Gas accretion flows within IRAS16293 is explored out to 6000 AU. Methods: ALMA Band 3 observations of low-$J$ transitions of HNC, cyanopolyynes (HC$_3$N, HC$_5$N), and N$_2$H$^+$ are used to probe the cloud core structure at ~100 AU resolution. Additional Band 3 archival data provide low-$J$ HCN and SiO lines. These data are compared with the corresponding higher-$J$ lines from the PILS Band 7 data for excitation analysis. The HNC/HCN ratio is used as a temperature tracer. Results: The low-$J$ transitions of HC$_3$N, HC$_5$N, HNC and N$_2$H$^+$ trace extended and elongated structures from 6000 AU down to ~100 AU, without accompanying dust continuum emission. Two structures are identified: one traces a flow that is likely accreting toward the most luminous component of the system IRAS16293 A. Temperatures inferred from the HCN/HNC ratio suggest that the gas in this flow is cold, between 10 and 30 K. The other structure is part of an UV-irradiated cavity wall entrained by one of the outflows. The two outflows driven by IRAS16293 A present different molecular gas distributions. Conclusions: Accretion of cold gas is seen from 6000 AU scales onto IRAS16293 A, but not onto source B, indicates that cloud core material accretion is competitive due to feedback onto a dominant component in an embedded multiple protostellar system. The preferential delivery of material could explain the higher luminosity and multiplicity of source A compared to source B. The results of this work demonstrate that several different molecular species, and multiple transitions of each species, are needed to confirm and characterize accretion flows in protostellar cloud cores.

astro-ph.GA↗

arXiv2021

Imaging the water snowline around protostars with water and HCO$^+$ isotopologues

The water snowline location in protostellar envelopes provides crucial information about the thermal structure and the mass accretion process as it can inform about the occurrence of recent ($\lesssim$1,000 yr) accretion bursts. In addition, the ability to image water emission makes these sources excellent laboratories to test indirect snowline tracers such as H$^{13}$CO$^+$. We study the water snowline in five protostellar envelopes in Perseus using a suite of molecular line observations taken with the Atacama Large Millimeter/submillimeter Array (ALMA) at $\sim$0.2$^{\prime\prime}-$0.7$^{\prime\prime}$ (60--210 au) resolution. B1-c provides a textbook example of compact H$_2^{18}$O ($3_{1,3}-2_{2,0}$) and HDO ($3_{1,2}-2_{2,1}$) emission surrounded by a ring of H$^{13}$CO$^+$ ($J=2-1$) and HC$^{18}$O$^+$ ($J=3-2$). Compact HDO surrounded by H$^{13}$CO$^+$ is also detected toward B1-bS. The optically thick main isotopologue HCO$^+$ is not suited to trace the snowline and HC$^{18}$O$^+$ is a better tracer than H$^{13}$CO$^+$ due to a lower contribution from the outer envelope. However, since a detailed analysis is needed to derive a snowline location from H$^{13}$CO$^+$ or HC$^{18}$O$^+$ emission, their true value as snowline tracer will lie in the application in sources where water cannot be readily detected. For protostellar envelopes, the most straightforward way to locate the water snowline is through observations of H$_2^{18}$O or HDO. Including all sub-arcsecond resolution water observations from the literature, we derive an average burst interval of $\sim$10,000 yr, but high-resolution water observations of a larger number of protostars is required to better constrain the burst frequency.

astro-ph.GA↗

arXiv2021

Fitting infrared ice spectra with genetic modelling algorithms. Presenting the ENIIGMA fitting tool

Context. A variety of laboratory ice spectra simulating different chemical environments, ice morphology as well as thermal and energetic processing are demanded to provide an accurate interpretation of the infrared spectra of protostars. To answer which combination of laboratory data best fit the observations, an automated statistically-based computational approach becomes necessary. Aims. To introduce a new approach, based on evolutionary algorithms, to search for molecules in ice mantles via spectral decomposition of infrared observational data with laboratory ice spectra. Methods. A publicly available and open-source fitting tool, called ENIIGMA (dEcompositioN of Infrared Ice features using Genetic Modelling Algorithms), is introduced. The tool has dedicated Python functions to carry out continuum determination of the protostellar spectra, silicate extraction, spectral decomposition and statistical analysis to calculate confidence intervals and quantify degeneracy. As an assessment of the code, several tests were conducted with known ice samples and constructed mixtures. A complete analysis of the Elias 29 spectrum was performed as well. Results. The ENIIGMA fitting tool can identify the correct ice samples and their fractions in all checks with known samples tested in this paper. Concerning the Elias 29 spectrum, the broad spectral range between 2.5-20 $μ$m was successfully decomposed after continuum determination and silicate extraction. This analysis allowed the identification of different molecules in the ice mantle, including a tentative detection of CH$_3$CH$_2$OH. Conclusions. The ENIIGMA is a toolbox for spectroscopy analysis of infrared spectra that is well-timed with the launch of the James Webb Space Telescope. Additionally, it allows for exploring the different chemical environments and irradiation fields in order to correctly interpret astronomical observations.

astro-ph.IM↗

arXiv2020

Temperature structures of embedded disks: young disks in Taurus are warm

The chemical composition of gas and ice in disks around young stars set the bulk composition of planets. In contrast to protoplanetary disks (Class II), young disks that are still embedded in their natal envelope (Class 0 and I) are predicted to be too warm for CO to freeze out, as has been confirmed observationally for L1527 IRS. To establish whether young disks are generally warmer than their more evolved counterparts, we observed five young (Class 0/I and Class I) disks in Taurus with the Atacama Large Millimeter/submillimeter Array (ALMA), targeting C$^{17}$O $2-1$, H$_2$CO $3_{1,2}-2_{1,1}$, HDO $3_{1,2}-2_{2,1}$ and CH$_3$OH $5_K-4_K$ transitions at $0.48^{\prime\prime} \times 0.31^{\prime\prime}$ resolution. The different freeze-out temperatures of these species allow us to derive a global temperature structure. C$^{17}$O and H$_2$CO are detected in all disks, with no signs of CO freeze-out in the inner $\sim$100 au, and a CO abundance close to $\sim$10$^{-4}$. H$_2$CO emission originates in the surface layers of the two edge-on disks, as witnessed by the especially beautiful V-shaped emission pattern in IRAS~04302+2247. HDO and CH$_3$OH are not detected, with column density upper limits more than 100 times lower than for hot cores. Young disks are thus found to be warmer than more evolved protoplanetary disks around solar analogues, with no CO freeze-out (or only in the outermost part of $\gtrsim$100 au disks) or CO processing. However, they are not as warm as hot cores or disks around outbursting sources, and therefore do not have a large gas-phase reservoir of complex molecules.

astro-ph.SR↗

arXiv2020

Carbon-grain sublimation: a new top-down component of protostellar chemistry

Earth's carbon deficit has been an outstanding problem in our understanding of the formation of our Solar System. A possible solution would be the sublimation of carbon grains at the so-called soot line (~300 K) early in the planet-formation process. Here, we argue that the most likely signatures of this process are an excess of hydrocarbons and nitriles inside the soot line, and a higher excitation temperature for these molecules compared to oxygen-bearing complex organics that desorb around the water snowline (~100 K). Such characteristics have been reported in the literature, for example, in Orion KL, although not uniformly, potentially due to differences in observational settings and analysis methods of different studies or related to the episodic nature of protostellar accretion. If this process is active, this would mean that there is a heretofore unknown 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.

astro-ph.EP↗

arXiv2020

An ALMA Survey of H$_2$CO in Protoplanetary Disks

H$_2$CO is one of the most abundant organic molecules in protoplanetary disks and can serve as a precursor to more complex organic chemistry. We present an ALMA survey of H$_2$CO towards 15 disks covering a range of stellar spectral types, stellar ages, and dust continuum morphologies. H$_2$CO is detected towards 13 disks and tentatively detected towards a 14th. We find both centrally-peaked and centrally-depressed emission morphologies, and half of the disks show ring-like structures at or beyond expected CO snowline locations. Together these morphologies suggest that H$_2$CO in disks is commonly produced through both gas-phase and CO-ice-regulated grain-surface chemistry. We extract disk-averaged and azimuthally-averaged H$_2$CO excitation temperatures and column densities for four disks with multiple H$_2$CO line detections. The temperatures are between 20-50K, with the exception of colder temperatures in the DM Tau disk. These temperatures suggest that H$_2$CO emission in disks is generally emerging from the warm molecular layer, with some contributions from the colder midplane. Applying the same H$_2$CO excitation temperatures to all disks in the survey, we find that H$_2$CO column densities span almost three orders of magnitude ($\sim 5 \times 10^{11} - 5 \times 10^{14} \mathrm{cm}^{-2}$). The column densities appear uncorrelated with disk size and stellar age, but Herbig Ae disks may have less H$_2$CO compared to T Tauri disks, possibly because of less CO freeze-out. More H$_2$CO observations towards Herbig Ae disks are needed to confirm this tentative trend, and to better constrain under which disk conditions H$_2$CO and other oxygen-bearing organics efficiently form during planet formation.

astro-ph.SR↗

arXiv2019

Mass Assembly of Stellar Systems and their Evolution with the SMA (MASSES) -- Full Data Release

We present and release the full dataset for the Mass Assembly of Stellar Systems and their Evolution with the SMA (MASSES) survey. This survey used the Submillimeter Array (SMA) to image the 74 known protostars within the Perseus molecular cloud. The SMA was used in two array configurations to capture outflows for scales $>$30$^{\prime\prime}$ ($>$9000 au) and to probe scales down to $\sim$1$^{\prime\prime}$ ($\sim$300 au). The protostars were observed with the 1.3 mm and 850 $μ$m receivers simultaneously to detect continuum at both wavelengths and molecular line emission from CO(2-1), $^{13}$CO(2-1), C$^{18}$O(2-1), N$_2$D$^+$(3-2), CO(3-2), HCO$^+$(4-3), and H$^{13}$CO$^+$(4-3). Some of the observations also used the SMA's recently upgraded correlator, SWARM, whose broader bandwidth allowed for several more spectral lines to be observed (e.g., SO, H$_2$CO, DCO$^+$, DCN, CS, CN). Of the main continuum and spectral tracers observed, 84% of the images and cubes had emission detected. The median C$^{18}$O(2-1) linewidth is $\sim$1.0 km s$^{-1}$, which is slightly higher than those measured with single-dish telescopes at scales of 3000-20000 au. Of the 74 targets, six are suggested to be first hydrostatic core candidates, and we suggest that L1451-mm is the best candidate. We question a previous continuum detection toward L1448 IRS2E. In the SVS13 system, SVS13A certainly appears to be the most evolved source, while SVS13C appears to be hotter and more evolved than SVS13B. The MASSES survey is the largest publicly available interferometric continuum and spectral line protostellar survey to date, and is largely unbiased as it only targets protostars in Perseus. All visibility ($uv$) data and imaged data are publicly available at https://dataverse.harvard.edu/dataverse/full_MASSES/.

astro-ph.GA↗

arXiv2019

Temperature profiles of young disk-like structures: The case of IRAS 16293A

Temperature is a crucial parameter in circumstellar disk evolution and planet formation, because it governs the resistance of the gas to gravitational instability and sets the chemical composition of the planet-forming material. We set out to determine the gas temperature of the young disk-like structure around the Class 0 protostar IRAS 16293$-$2422A. We use Atacama Large Millimeter/submillimeter Array (ALMA) observations of multiple H$_2$CS $J=7-6$ and $J=10-9$ lines from the Protostellar Interferometric Line Survey (PILS) to create a temperature map for the inner $\sim$200 AU of the disk-like structure. This molecule is a particularly useful temperature probe because transitions between energy levels with different $K_{\rm{a}}$ quantum numbers operate only through collisions. Based on the H$_2$CS line ratios, the temperature is between $\sim$100$-$175 K in the inner $\sim$150 AU, and drops to $\sim$75 K at $\sim$200 AU. At the current resolution (0.5$^{\prime\prime} \sim$70 AU), no jump is seen in the temperature at the disk-envelope interface. The temperature structure derived from H$_2$CS is consistent with envelope temperature profiles that constrain the temperature from 1000 AU scales down to $\sim$100 AU, but does not follow the temperature rise seen in these profiles at smaller radii. Higher angular resolution observations of optically thin temperature tracers are needed to establish whether cooling by gas-phase water, the presence of a putative disk or the dust optical depth influences the gas temperature at $\lesssim$100 AU scales. The temperature at 100 AU is higher in IRAS 16293A than in the embedded Class 0/I disk L1527, consistent with the higher luminosity of the former.

astro-ph.SR↗

arXiv2019

Interferometric observations of warm deuterated methanol in the inner regions of low-mass protostars

Methanol is a key species in astrochemistry since it is the most abundant organic molecule in the ISM and is thought to be the mother molecule of many complex organic species. Estimating the deuteration of methanol around young protostars is of crucial importance because it highly depends on its formation mechanisms and the physical conditions during its moment of formation. We analyse dozens of transitions from deuterated methanol isotopologues coming from various existing observational datasets from the IRAM-PdBI and ALMA sub-mm interferometers to estimate the methanol deuteration surrounding three low-mass protostars on Solar System scales. A population diagram analysis allows us to derive a [CH$_2$DOH]/[CH$_3$OH] abundance ratio of 3-6 % and a [CH$_3$OD]/[CH$_3$OH] ratio of 0.4-1.6 % in the warm inner protostellar regions. These values are ten times lower than those derived with previous single-dish observations towards these sources but they are 10-100 times higher than the methanol deuteration measured in massive hot cores. Dust temperature maps obtained from Herschel and Planck observations show that massive hot cores are located in warmer molecular clouds than low-mass sources, with temperature differences of $\sim$10 K. Comparison with the predictions of the gas-grain astrochemical model GRAINOBLE shows that such a temperature difference is sufficient to explain the different deuteration observed in low- to high-mass sources, suggesting that the physical conditions of the molecular cloud at the origin of the protostars mostly govern the present observed deuteration of methanol. The methanol deuteration measured in this work is higher by a factor of 5 than the upper limit in methanol deuteration estimated in comet Hale-Bopp, implying that an important reprocessing of the organic material would have occurred in the solar nebula during the formation of the Solar System.

astro-ph.GA↗

arXiv2019

Kinematics around the B335 protostar down to au scales

Context. The relationship between outflow launching and formation of accretion disks around young stellar objects is still not entirely understood, which is why spectrally and spatially resolved observations are needed. Recently, the Atacama Large Millimetre/sub-millimetre Array (ALMA) has carried out long-baseline observations towards a handful of sources, revealing connections between outflows and the inner regions of disks. Aims. Here we aim to determine the small-scale kinematic and morphological properties of the outflow from the isolated protostar B335 for which no Keplerian disk has, so far, been observed on scales down to 10 au. Methods. We use ALMA in its longest-baseline configuration to observe emission from CO isotopologs, SiO, SO$_2$ and CH$_3$OH. The proximity of B335 provides a resolution of ~3 au (0.03''). We also combine our long-baseline data with archival data to produce a high-fidelity image covering scales up to 700 au (7''). Results. $^{12}$CO has a X-shaped morphology with arms ~50 au in width that we associate with the walls of an outflow cavity, similar to what is observed on larger scales. Long-baseline continuum emission is confined to <7 au of the protostar, while short-baseline continuum emission follows the $^{12}$CO outflow and cavity walls. Methanol is detected within ~30 au of the protostar. SiO is also detected in the vicinity of the protostar, but extended along the outflow. Conclusions. The $^{12}$CO outflow shows no clear signs of rotation at distances $\gtrsim$30 au from the protostar. SiO traces the protostellar jet on small scales, but without obvious rotation. CH$_3$OH and SO$_2$ trace a region <16 au in diameter, centred on the continuum peak, which is clearly rotating. Using episodic, high-velocity, $^{12}$CO features, we estimate the launching radius of the outflow to be <0.1 au and dynamical timescales on the order of a few years.

astro-ph.SR↗

arXiv2019

Ingredients for Solar-like Systems: protostar IRAS 16293-2422 B versus comet 67P/Churyumov-Gerasimenko

Our modern day Solar System has $4.6\times10^9$ yrs of evolution behind it with just a few relics of its birth conditions remaining. Comets are thought to be some of the most pristine tracers of the initial ingredients that were combined to produce the Earth and the other planets. Other low-mass protostars may be analogous to our proto-Sun and hence, could be used to study the building blocks necessary to form Solar-like systems. This study tests this idea on the basis of new high sensitivity, high spatial resolution ALMA data on the protoplanetary disc-scales (~70 au) of IRAS 16293-2422 and the bulk composition of comet 67P/Churyumov-Gerasimenko, as determined for the first time with the unique in situ monitoring carried out by Rosetta. The comparative analysis of the observations from the Protostellar Interferometric Line Survey (PILS) and the measurements made with Rosetta Orbiter Spectrometer for Ion and Neutral Analysis (ROSINA) shows that the relative abundances of CHO-, N-, and S-bearing molecules correlate, with some scatter, between protostellar and cometary data. A tentative correlation is seen for the first time for P- and Cl-bearing compounds. The results imply that the volatile composition of cometesimals and planetesimals is partially inherited from the pre- and protostellar phases of evolution.

astro-ph.SR↗

arXiv2019

The organic chemistry in the innermost, infalling envelope of the Class 0 protostar L483

Context: The protostellar envelopes, outflow and large-scale chemistry of Class~0 and Class~I objects have been well-studied, but while previous works have hinted at or found a few Keplerian disks at the Class~0 stage, it remains to be seen if their presence in this early stage is the norm. Likewise, while complex organics have been detected toward some Class~0 objects, their distribution is unknown as they could reside in the hottest parts of the envelope, in the emerging disk itself or in other components of the protostellar system, such as shocked regions related to outflows. Aims: In this work, we aim to address two related issues regarding protostars: when rotationally supported disks form around deeply embedded protostars and where complex organic molecules reside in such objects. Methods: We observed the deeply embedded protostar, L483, using Atacama Large Millimeter/submillimeter Array (ALMA) Band~7 data from Cycles~1 and 3 with a high angular resolution down to $\sim$~0.1$^{\prime\prime}$ (20~au) scales. Results: We find that the kinematics of CS~$J=7$--$6$ and H$^{13}$CN~$J=4$--$3$ are best fitted by the velocity profile from infall under conservation of angular momentum and not by a Keplerian profile. The spatial extents of the observed complex organics are consistent with an estimated ice sublimation radius of the envelope at $\sim$~50~au, suggesting that the complex organics exist in the hot corino of L483. Conclusions: We find that L483 does not harbor a Keplerian disk down to at least $15$~au in radius. Instead, the innermost regions of L483 are undergoing a rotating collapse. This result highlights that some Class~0 objects contain only very small disks, or none at all, with the complex organic chemistry taking place on scales inside the hot corino of the envelope, in a region larger than the emerging disk.

astro-ph.SR↗

arXiv2019

Millimeter and Submillimeter Wave Spectroscopy of Propanal

The rotational spectra of the two stable conformers syn- and gauche-propanal (CH$_3$CH$_2$CHO) were studied in the millimeter and submillimeter wave regions from 75 to 500 GHz with the Cologne (Sub-)Millimeter wave Spectrometer. Furthermore, the first excited states associated with the aldehyde torsion and with the methyl torsion, respectively, of the $syn$-conformer were analyzed. The newly obtained spectroscopic parameters yield better predictions, thus fulfill sensitivity and resolution requirements in new astronomical observations in order to unambiguously assign pure rotational transitions of propanal. This is demonstrated on a radio astronomical spectrum from the Atacama Large Millimeter/submillimeter Array Protostellar Interferometric Line Survey (ALMA-PILS). In particular, an accurate description of observed splittings, caused by internal rotation of the methyl group in the $syn$-conformer and by tunneling rotation interaction from two stable degenerate $gauche$-conformers, is reported. The rotational spectrum of propanal is of additional interest because of its two large amplitude motions pertaining to the methyl and the aldehyde group, respectively.

astro-ph.SR↗