Still searching Arxiv, refresh for possibly better results.

Results for "Ewine F. van Dishoeck"

total 102317took 0.17s
Chemical changes during star formation: high- versus low-mass YSOsJan 25 2003Recent observational studies of high- and low-mass YSOs at (sub)millimeter and infrared wavelengths are reviewed, and chemical diagnostics of the different physical components are summarized. Methods for determining the temperature, density and abundance ... More
Astrochemistry of dust, ice and gas: introduction and overviewNov 19 2014A brief introduction and overview of the astrochemistry of dust, ice and gas and their interplay is presented, aimed at non-specialists. The importance of basic chemical physics studies of critical reactions is illustrated through a number of recent examples. ... More
ISO spectroscopy of gas and dust: from molecular clouds to protoplanetary disksMar 02 2004Observations of interstellar gas-phase and solid-state species in the 2.4-200 micron range obtained with the spectrometers on board the Infrared Space Observatory are reviewed. Lines and bands due to ices, polycyclic aromatic hydrocarbons, silicates and ... More
Models and Observations of the Chemistry near Young Stellar ObjectsJun 07 1999The study of the chemical evolution of gas and dust from pre-stellar dense cores to circumstellar disks around young stars forms an essential part of understanding star- and planet formation. Throughout the collapse- and protostellar phases, simple and ... More
Molecular photodissociationJun 20 2011Feb 09 2015Photodissociation is the dominant removal process of molecules in any region exposed to intense ultraviolet (UV) radiation. This includes diffuse and translucent interstellar clouds, dense photon-dominated regions, high velocity shocks, the surface layers ... More
Water Vapor in the Inner 25 AU of a Young Disk around a Low-Mass ProtostarJan 10 2010Water is one of the key molecules in the physical and chemical evolution of star- and planet-forming regions. We here report the first spatially resolved observation of thermal emission of (an isotopologue of) water with the Plateau de Bure Interferometer ... More
Star and Planet Formation with ALMA: an OverviewAug 22 2007Submillimeter observations with ALMA will be the essential next step in our understanding of how stars and planets form. Key projects range from detailed imaging of the collapse of pre-stellar cores and measuring the accretion rate of matter onto deeply ... More
Water in Star and Planet Forming RegionsOct 19 2011In this paper we discuss the astronomical search for water vapor in order to understand the disposition of water in all its phases throughout the process of star and planet formation. Our ability to detect and study water vapor has recently received a ... More
The HDO/H2O ratio in gas in the inner regions of a low-mass protostarNov 12 2010The HDO/H2O abundance ratio is thought to be a key diagnostic on the evolution of water during the star- and planet-formation process and thus on its origin on Earth. We here present millimeter-wavelength high angular resolution observations of the deeply ... More
Limits on the cosmic-ray ionization rate toward massive young starsJun 19 2000Recent models of the envelopes of seven massive protostars are used to analyze observations of H3+ infrared absorption and H13CO+ submillimeter emission lines toward these stars, and to constrain the cosmic-ray ionization rate zeta. The H13CO+ gives best-fit ... More
Chemistry in the Envelopes around Massive Young StarsFeb 04 2000Recent observational studies of intermediate- and high-mass star-forming regions at submillimeter and infrared wavelengths are reviewed, and chemical diagnostics of the different physical components associated with young stellar objects are summarized. ... More
Sun-bathing around low-mass protostars: APEX-CHAMP+ observations of high-J COSep 19 2009We present the first maps of high-excitation CO J=6-5 and 7-6 and isotopologue lines over 2'-5' regions at 10" resolution toward low-mass protostars to probe the origin of the warm gas in their surroundings. The data were obtained using the CHAMP+ 650/850 ... More
Disk masses in the Orion Molecular Cloud-2: distinguishing time and environmentMay 23 2019The mass evolution of protoplanetary disks is driven by both internal processes and external factors, such as photoevaporation. Disentangling these two effects, however, has remained difficult. We measure the dust masses of a sample of 132 disks in the ... More
Ro-vibrational excitation of an organic molecule (HCN) in protoplanetary disksDec 04 2014(Abridged) Organic molecules are important constituents of protoplanetary disks. Their ro-vibrational lines observed in the near- and mid-infrared are commonly detected toward T Tauri disks. These lines are the only way to probe the chemistry in the inner ... More
Spectroscopic properties of Young Stellar Objects in the Lupus Molecular CloudsAug 04 2011The results of an optical spectroscopic survey of a sample of young stellar objects (YSOs) and pre-main sequence (PMS) stars in the Lupus Clouds are presented. 92 objects were observed with VLT/FLAMES. All of those objects show IR excess as discovered ... More
Molecular abundances and C/O ratios in chemically evolving planet-forming disk midplanesSep 22 2017(Abridged) Exoplanet atmospheres are thought be built up from accretion of gas as well as pebbles and planetesimals in the midplanes of planet-forming disks. The chemical composition of this material is usually assumed to be unchanged during the disk ... More
Setting the volatile composition of (exo)planet-building material. Does chemical evolution in disk midplanes matter?Jul 22 2016[Abridged] Chemical evolution in the protoplanetary disk midplane can modify the composition of ices and gases. We have investigated if and how chemical evolution affects the abundances and distributions of key volatile species in the midplane of a protoplanetary ... More
The molecular composition of the planet-forming regions of protoplanetary disks across the luminosity regimeJul 30 2015Sep 02 2015(Abridged) Near- to mid-IR observations of protoplanetary disks show that the inner regions (<10AU) are rich in small organic volatiles (e.g., C2H2 and HCN). Trends in the data suggest that disks around cooler stars (~3000K) are potentially more carbon- ... More
Photodesorption of ices I: CO, N2 and CO2Sep 08 2008Jan 23 2009A longstanding problem in astrochemistry is how molecules can be maintained in the gas phase in dense inter- and circumstellar regions. Photodesorption is a non-thermal desorption mechanism, which may explain the small amounts of observed cold gas in ... More
Cold gas as an ice diagnostic toward low mass protostarsJan 08 2009Up to 90% of the chemical reactions during star formation occurs on ice surfaces, probably including the formation of complex organics. Only the most abundant ice species are however observed directly by infrared spectroscopy. This study aims to develop ... More
Warm water deuterium fractionation in IRAS 16293-2422 - The high-resolution ALMA and SMA viewNov 28 2012Measuring the water deuterium fractionation in the inner warm regions of low-mass protostars has so far been hampered by poor angular resolution obtainable with single-dish ground- and space-based telescopes. Observations of water isotopologues using ... More
Physical structure and CO abundance of low-mass protostellar envelopesMay 05 2002We present 1D radiative transfer modelling of the envelopes of a sample of 18 low-mass protostars and pre-stellar cores with the aim of setting up realistic physical models, for use in a chemical description of the sources. The density and temperature ... More
CO2 infrared emission as a diagnostic of planet-forming regions of disksJan 27 2017[Abridged] The infrared ro-vibrational emission lines from organic molecules in the inner regions of protoplanetary disks are unique probes of the physical and chemical structure of planet forming regions and the processes that shape them. The non-LTE ... More
Chemical history of molecules in circumstellar disksJul 11 2011The chemical composition of a protoplanetary disk is determined not only by in situ chemical processes during the disk phase, but also by the history of the gas and dust before it accreted from the natal envelope. In order to understand the disk's chemical ... More
Astrochemistry of Sub-Millimeter Sources in Orion: Studying the Variations of Molecular Tracers with Changing Physical ConditionsOct 06 2003Cornerstone molecules (CO, H_2CO, CH_3OH, HCN, HNC, CN, CS, SO) were observed toward seven sub-millimeter bright sources in the Orion molecular cloud in order to quantify the range of conditions for which individual molecular line tracers provide physical ... More
Protoplanetary disk masses from CO isotopologues line emissionOct 08 2014One of the methods for deriving disk masses relies on direct observations of the gas, whose bulk mass is in the outer cold ($T\lesssim30$K) regions. This zone can be well traced by rotational lines of less abundant CO isotopologues, that probe the gas ... More
Photodissociation of water in crystalline ice: a molecular dynamics studyMay 31 2005Ultraviolet irradiation of ice is of great interest for understanding the chemistry in both atmospheric and astrophysical environments. In interstellar space, photodissociation of H2O molecules can be a driving force behind the chemistry on icy dust grains ... More
Probing the protoplanetary disk gas surface density distribution with $^{13}$CO emissionSep 03 2018It is key to constrain the gas surface density distribution, Sigma_gas, as function of disk radius in protoplanetary disks. In this work we investigate if spatially resolved observations of rarer CO isotopologues may be good tracers of Sigma_gas. Physical-chemical ... More
On the origin of O$_2$ and other volatile species in cometsNov 07 2017Molecular oxygen, O$_2$, was recently detected in comet 67P by the ROSINA instrument on board the Rosetta spacecraft with a surprisingly high abundance of 4 % relative to H$_2$O, making O$_2$ the fourth most abundant in comet 67P. Other volatile species ... More
Determining protoplanetary disk gas masses from CO isotopologues line observationsMay 25 2016Despite intensive studies of protoplanetary disks, there is still no reliable way to determine their total mass and their surface density distribution, quantities that are crucial for describing both the structure and the evolution of disks up to the ... More
Subarcsecond resolution observations of warm water towards three deeply embedded low-mass protostarsMar 22 2012Water is present during all stages of star formation: as ice in the cold outer parts of protostellar envelopes and dense inner regions of circumstellar disks, and as gas in the envelopes close to the protostars, in the upper layers of circumstellar disks ... More
Molecular abundances in low-mass protostellar envelopesNov 24 2002A study of the chemical structure of the envelopes around a sample protostars is introduced. Physical models for the envelopes derived using 1D radiative transfer modeling of their dust continuum emission are used as input for Monte Carlo modeling of ... More
A primordial origin for molecular oxygen in comets: A chemical kinetics study of the formation and survival of O$_2$ ice from clouds to disksAug 25 2016Molecular oxygen has been confirmed as the fourth most abundant molecule in cometary material O$_2$/H$_2$O $\sim 4$ %) and is thought to have a primordial nature, i.e., coming from the interstellar cloud from which our solar system was formed. However, ... More
CO destruction in protoplanetary disk midplanes: inside versus outside the CO snow surfaceAug 07 2018Aug 29 2018CO has long been thought to be the best tracer to measure gas masses as it is readily detected at (sub)mm wavelengths in many disks. Inferred gas masses from CO in recent ALMA observations of large samples of disks seem inconsistent with their inferred ... More
Simulating the atomic and molecular content of molecular clouds using probability distributions of physical parametersJan 31 2019Modern observations of the interstellar medium (ISM) in galaxies detect a variety of atomic and molecular species. The goal is to connect these observations to the astrochemical properties of the ISM. 3D hydro-chemical simulations attempt this but due ... More
Interstellar water chemistry: from laboratory to observationsDec 17 2013Water is observed throughout the universe, from diffuse interstellar clouds to protoplanetary disks around young stars, and from comets in our own solar system and exoplanetary atmospheres to galaxies at high redshifts. This review summarizes the spectroscopy ... More
Lines of Circumstellar C2, CN, and CH+ in the Optical Spectra of Post-Agb StarsSep 04 1996Recent optical spectra of post-AGB stars show the presence of C2, CN, and CH+ originating in the circumstellar shell. We present here new, higher resolution spectra which provide constraints on the physical parameters and information on the line profiles. ... More
Different dust and gas radial extents in protoplanetary disks: consistent models of grain growth and CO emissionMay 17 2017Jun 01 2017ALMA observations of protoplanetary disks confirm earlier indications that there is a clear difference between the dust and gas radial extents. The origin of this difference is still debated, with both radial drift of the dust and optical depth effects ... More
Molecular Oxygen in Oort Cloud Comet 1P/HalleyDec 05 2015Recently the ROSINA mass spectrometer suite on board the European Space Agency's Rosetta spacecraft discovered an abundant amount of molecular oxygen, O2, in the coma of Jupiter family comet 67P/Churyumov-Gerasimenko of O2/H2O = 3.80+/-0.85%. It could ... More
Connecting planet formation and astrochemistry: Refractory carbon depletion leading to super-stellar C/O in giant planetary atmospheresJan 25 2019[Abridged] Combining a time-dependent astrochemical model with a model of planet formation and migration, we compute the carbon-to-oxygen ratio (C/O) of a range of planetary embryos starting their formation in the inner solar system (1-3 AU). The volatile ... More
The Abundance and Emission of H2O and O2 in Clumpy Molecular CloudsNov 23 2000Recent observations with the Submillimeter Wave Astronomy Satellite indicate abundances of gaseous H2O and O2 in dense molecular clouds which are significantly lower than found in standard homogeneous chemistry models. We present here results for the ... More
Gas structure inside dust cavities of transition disks: Oph IRS 48 observed by ALMADec 10 2013(Abridged) Transition disks are recognized by the absence of emission of small dust grains inside a radius of up to several 10s of AUs. Due to the lack of angular resolution and sensitivity, the gas content of such dust holes has not yet been determined, ... More
Structure and Evolution of the Envelopes of Deeply Embedded Massive Young StarsJan 31 2000Feb 01 2000The physical structure of the envelopes around a sample of fourteen massive (1000-100,000 solar L) young stars is investigated on 100- 100,000 AU scales using maps and spectra in submillimeter continuum and lines of C17O, CS and H2CO. The total column ... More
Abundance profiles of CH3OH and H2CO toward massive young stars as evolutionary tracersAug 01 2000The chemical evolution of thirteen regions of massive star formation is studied through single-dish and interferometer line observations at submillimeter wavelengths. The wealth of CH3OH and H2CO lines covering a large range of excitation conditions allows ... More
Warm formaldehyde in the Oph IRS 48 transitional diskFeb 03 2014Feb 07 2014Simple molecules like H2CO and CH3OH in protoplanetary disks are the starting point for the production of more complex organic molecules. So far, the observed chemical complexity in disks has been limited due to freeze out of molecules onto grains in ... More
Detection of interstellar H_2D^+ emissionJun 12 1999We report the detection of the 1_{10}-1_{11} ground state transition of ortho-H_2D^+ at 372.421 GHz in emission from the young stellar object NGC 1333 IRAS 4A. Detailed excitation models with a power-law temperature and density structure yield a beam-averaged ... More
Chemistry of massive young stellar objects with a disk-like structureApr 15 2013Our goal is to take an inventory of complex molecules in three well-known high-mass protostars for which disks or toroids have been claimed and to study the similarities and differences with a sample of massive YSOs without evidence of such flattened ... More
Tracing the envelopes around embedded low-mass young stellar objects with HCO+ and millimeter-continuum observationsJun 09 1997Interferometer observations of millimeter-continuum (OVRO) and single-dish observations of HCO+ and H13CO+ J=1-0, 3-2, and 4-3 (JCMT, IRAM 30m) are presented of nine embedded low-mass young stellar objects (YSOs) in Taurus. All nine objects are detected ... More
Axi-symmetric models of ultraviolet radiative transfer with applications to circumstellar disk chemistryNov 01 2002A new two-dimensional axi-symmetric ultraviolet radiative transfer code is presented, which is used to calculate photodissociation and ionization rates for use in chemistry models of flaring circumstellar disks. Scattering and absorption of photons from ... More
Evidence for Hco+ Infall toward T Tauri?Feb 22 1994High spectral and spatial resolution observations of the HCO+ molecule toward the T Tau binary system obtained with the Owens Valley Millimeter Array reveal a broad emission line profile (V_LSR = 7.2 km/s, width = 2.0 km/s) upon which a narrow, redshifted ... More
Robustness of N2H+ as tracer of the CO snowlineOct 21 2016[Abridged] Snowlines in protoplanetary disks play an important role in planet formation and composition. Since the CO snowline is difficult to observe directly with CO emission, its location has been inferred in several disks from spatially resolved ALMA ... More
Volatile snowlines in embedded disks around low-mass protostarsJul 27 2015(Abridged*) Models of the young solar nebula assume a hot initial disk with most volatiles are in the gas phase. The question remains whether an actively accreting disk is warm enough to have gas-phase water up to 50 AU radius. No detailed studies have ... More
Effects of Reagent Rotation and Vibration on H + OH (v,j) $\to$ O + H2Feb 25 2014The dynamics of the reaction H + OH $\to$ O (3P) + H2 have been studied in a series of quasi-classical trajectory (QCT) calculations and transition state theory (TST) methods using high quality 3A' and 3A'' potential energy surfaces (PESs). Accurate OH ... More
Submillimeter lines from circumstellar disks around pre-main sequence starsAug 23 2001Observations of submillimeter lines of CO (up to J=6-5), HCO+, HCN (up to J=4-3) and their isotopes from circumstellar disks around low mass pre-main sequence stars are presented. The different line ratios and optical depths indicate that most of the ... More
Complex molecules toward low-mass protostars: the Serpens coreJul 28 2011Gas-phase complex organic molecules are commonly detected toward high-mass protostellar hot cores. Detections toward low-mass protostars and outflows are comparatively rare, and a larger sample is key to investigate how the chemistry responds to its environment. ... More
Molecular Dynamics Simulations of CO2 Formation in Interstellar IcesOct 11 2013CO2 ice is one of the most abundant components in ice-coated interstellar ices besides H2O and CO, but the most favorable path to CO2 ice is still unclear. Molecular dynamics calculations on the ultraviolet photodissociation of different kinds of CO-H2O ... More
Organic molecules in protoplanetary disks around TTauri and HerbigAe starsJun 25 2004The results of single-dish observations of low- and high-J transitions of selected molecules from protoplanetary disks around two TTauri stars (LkCa15 and TWHya) and two HerbigAe stars (HD163296 and MWC480) are reported. Simple molecules such as CO, 13CO, ... More
Tracing FUV Radiation in the Embedded Phase of Star FormationJan 10 2011Molecules containing one or a few hydrogen atoms and a heavier atom (hydrides) have been predicted to trace FUV radiation. In some chemical models, FUV emission by the central object or protostar of a star forming region greatly enhances some of the hydride ... More
Circumstellar C2, CN, and CH+ in the optical spectra of post-AGB starsOct 09 1996We present optical high-resolution spectra of a sample of sixteen post-AGB stars and IRC +10216. Of the post-AGB stars, ten show C2 Phillips and Swan and CN Red System absorption, one CH+ emission, one CH+ absorption, and four without any molecules. We ... More
ISO-LWS detection of the 112 micron HD J=1-0 line toward the Orion BarJan 28 1999We report the first detection outside of the solar system of the lowest pure rotational J=1-0 transition of the HD molecule at 112 microns. The detection was made toward the Orion Bar using the Fabry-Perot of the Long Wavelength Spectrometer (LWS) on ... More
Neutral and Ionized Hydrides in Star-forming Regions -- Observations with Herschel/HIFIAug 26 2013The cosmic abundance of hydrides depends critically on high-energy UV, X-ray, and particle irradiation. Here we study hydrides in star-forming regions where irradiation by the young stellar object can be substantial, and density and temperature can be ... More
VLT/X-shooter Spectroscopy of a Dusty Planetary Nebula Discovered with Spitzer/IRSDec 06 2010As part of a mid-infrared spectroscopic survey of young stars with the Spitzer Space Telescope, an unclassified red emission line object was discovered. Based on its high ionization state indicated by the Spitzer spectrum, this object could either be ... More
Water: from clouds to planetsJan 31 2014Feb 25 2014Results from recent space missions, in particular Spitzer and Herschel, have lead to significant progress in our understanding of the formation and transport of water from clouds to disks, planetesimals, and planets. In this review, we provide the underpinnings ... More
The warm gas atmosphere of the HD 100546 disk seen by Herschel (Evidence of a gas-rich, carbon-poor atmosphere?)Jan 23 2012(Abridged) Context. With the Herschel Space Observatory, lines of simple molecules (C+, O, and CO) have been observed in the atmosphere of protoplanetary disks. When combined with ground-based [CI], all principle forms of carbon can be studied. The absence ... More
Deep Spitzer spectroscopy of the `Flying Saucer' edge-on disk: Large grains beyond 50 AUFeb 14 2007We present deep Spitzer-IRS low-resolution (lambda/Delta lambda ~ 100) 5-35 micron spectroscopy of the edge-on disk ``the Flying Saucer'' (2MASS J16281370-2431391) in the Ophiuchus molecular cloud. The spectral energy distribution exhibits the characteristic ... More
Water and methanol in low-mass protostellar outflows: gas-phase synthesis, ice sputtering and destructionFeb 28 2014Water in outflows from protostars originates either as a result of gas-phase synthesis from atomic oxygen at T > 200 K, or from sputtered ice mantles containing water ice. We aim to quantify the contribution of the two mechanisms that lead to water in ... More
HD far infrared emission as a measure of protoplanetary disk massMay 22 2017Protoplanetary disks around young stars are the sites of planet formation. While the dust mass can be estimated using standard methods, determining the gas mass - and thus the amount of material available to form giant planets - has proven to be very ... More
Inferring giant planets from ALMA millimeter continuum and line observations in (transition) disksOct 12 2017Dec 27 2017Potential signatures of proto-planets embedded in their natal protoplanetary disk are radial gaps or cavities in the continuum emission in the IR-mm wavelength range. ALMA observations are now probing spatially resolved rotational line emission of CO ... More
Multidimensional chemical modelling, II. Irradiated outflow wallsJun 03 2009Observations of the high-mass star forming region AFGL 2591 reveal a large abundance of CO+, a molecule known to be enhanced by far UV (FUV) and X-ray irradiation. In chemical models assuming a spherically symmetric envelope, the volume of gas irradiated ... More
Quantification of segregation dynamics in ice mixturesJul 22 2009(Abridged) The observed presence of pure CO2 ice in protostellar envelopes is attributed to thermally induced ice segregation, but a lack of quantitative experimental data has prevented its use as a temperature probe. Quantitative segregation studies ... More
The Infrared Band Strengths of H2o, Co and Co2 in Laboratory Simulations of Astrophysical Ice MixturesSep 28 1994Mar 14 1995Infrared spectroscopic observations toward objects obscured by dense cloud material show that H$_2$O, CO and, likely, CO$_2$ are important constituents of interstellar ice mantles. In order to accurately calculate the column densities of these molecules, ... More
Formation of Glycerol through Hydrogenation of CO ice under Prestellar Core ConditionsMay 26 2017Observational studies reveal that complex organic molecules (COMs) can be found in various objects associated with different star formation stages. The identification of COMs in prestellar cores, i.e., cold environments in which thermally induced chemistry ... More
Photon Dominated Regions in Low UV Fields: A Study of The Peripheral Region of L1204/S140Dec 11 2001We have carried out an in-depth study of the peripheral region of the molecular cloud L1204/S140, where the far ultraviolet radiation and the density are relatively low. Our observations test theories of photon-dominated regions (PDRs) in a regime that ... More
c2d Spitzer IRS spectra of embedded low-mass young stars: gas-phase emission linesMay 17 2010A survey of mid-IR gas-phase emission lines of H2, H2O and various atoms toward a sample of 43 embedded low-mass young stars in nearby star-forming regions is presented. The sources are selected from the Spitzer "Cores to Disks" (c2d) legacy program. ... More
The effect of a strong external radiation field on protostellar envelopes in OrionDec 12 2005We discuss the effects of an enhanced interstellar radiation field (ISRF) on the observables of protostellar cores in the Orion cloud region. Dust radiative transfer is used to constrain the envelope physical structure by reproducing SCUBA 850 micron ... More
The complex chemistry of outflow cavity walls exposed: the case of low-mass protostarsMay 21 2015Complex organic molecules are ubiquitous companions of young low-mass protostars. Recent observations suggest that their emission stems, not only from the traditional hot corino, but also from offset positions. In this work, 2D physicochemical modelling ... More
Role of environment and gas temperature in the formation of multiple protostellar systems: molecular tracersSep 13 2018Context: Simulations suggest that gas heating due to radiative feedback is a key factor in whether or not multiple protostellar systems will form. Chemistry is a good tracer of the physical structure of a protostellar system, since it depends on the temperature ... More
Simultaneous Hydrogenation and UV-photolysis Experiments of NO in CO-rich Interstellar Ice Analogues; linking HNCO, OCN-, NH2CHO and NH2OHMay 25 2017The laboratory work presented here, simulates the chemistry on icy dust grains as typical for the 'CO freeze-out stage' in dark molecular clouds. It differs from previous studies in that solid-state hydrogenation and vacuum UV-photoprocessing are applied ... More
Photodissociation and chemistry of N$_2$ in the circumstellar envelope of carbon-rich AGB starsJun 28 2014The envelopes of AGB stars are irradiated externally by ultraviolet photons; hence, the chemistry is sensitive to the photodissociation of N$_2$ and CO, which are major reservoirs of nitrogen and carbon, respectively. The photodissociation of N$_2$ has ... More
A 30 AU radius CO gas hole in the disk around the Herbig Ae star Oph IRS 48Oct 10 2011The physical processes leading to the disappearance of disks around young stars are not well understood. A subclass of transitional disks, the so-called cold disks with large inner dust holes, provide a crucial laboratory for studying disk dissipation ... More
Hydrides in Young Stellar Objects: Radiation tracers in a protostar-disk-outflow systemJul 20 2010Context: Hydrides of the most abundant heavier elements are fundamental molecules in cosmic chemistry. Some of them trace gas irradiated by UV or X-rays. Aims: We explore the abundances of major hydrides in W3 IRS5, a prototypical region of high-mass ... More
Do siblings always form and evolve simultaneously? Testing the coevality of multiple protostellar systems through SEDsApr 20 2016Multiplicity is common in field stars and among protostellar systems. Models suggest two paths of formation: turbulent fragmentation and protostellar disk fragmentation. We attempt to find whether or not the coevality frequency of multiple protostellar ... More
Photodesorption of Ices II: H2O and D2ODec 10 2008Gaseous H2O has been detected in several cold astrophysical environments, where the observed abundances cannot be explained by thermal desorption of H2O ice or by H2O gas phase formation. These observations hence suggest an efficient non-thermal ice desorption ... More
High-precision C17O, C18O and C16O measurements in young stellar objects: analogues for CO self-shielding in the early solar systemJun 05 2009Using very high resolution (lambda / Dlambda ~ 95000) 4.7 micron fundamental and 2.3 micron overtone ro-vibrational CO absorption spectra obtained with the CRIRES infrared spectrometer on the Very Large Telescope (VLT), we report detections of four CO ... More
Efficiency of radial transport of ices in protoplanetary disks probed with infrared observations: the case of CO$_2$Dec 11 2017The efficiency of radial transport of icy solid material from outer disk to the inner disk is currently unconstrained. Efficient radial transport of icy dust grains could significantly alter the composition of the gas in the inner disk. Our aim is to ... More
Evolution of CO lines in time-dependent models of protostellar disk formationApr 18 2013(Abridged) Star and planet formation theories predict an evolution in the density, temperature, and velocity structure as the envelope collapses and forms an accretion disk. The aim of this work is to model the evolution of the molecular excitation, line ... More
On the Evolution of Dust Mineralogy, From Protoplanetary Disks to Planetary SystemsApr 18 2011Mineralogical studies of silicate features emitted by dust grains in protoplanetary disks and Solar System bodies can shed light on the progress of planet formation. The significant fraction of crystalline material in comets, chondritic meteorites and ... More
The Physical Structure of Protoplanetary Disks: the Serpens Cluster Compared with Other RegionsDec 13 2012Spectral energy distributions are presented for 94 young stars surrounded by disks in the Serpens Molecular Cloud, based on photometry and Spitzer IRS spectra. Taking a distance to the cloud of 415 pc rather than 259 pc, the distribution of ages is shifted ... More
Nitrogen isotope fractionation in protoplanetary disksFeb 08 2018Aims: The two stable isotopes of nitrogen, 14N and 15N, exhibit a range of abundance ratios both inside and outside the solar system. The elemental ratio in the solar neighborhood is 440. Recent ALMA observations showed HCN/HC15N ratios from 83 to 156 ... More
Hot water in the inner 100 AU of the Class 0 protostar NGC1333 IRAS2AMar 25 2013Evaporation of water ice above 100 K in the inner few 100 AU of low-mass embedded protostars (the so-called hot core) should produce quiescent water vapor abundances of ~10^-4 relative to H2. Observational evidence so far points at abundances of only ... More
The chemical connection between 67P/C-G and IRAS 16293-2422Feb 08 2018The chemical evolution of a star- and planet-forming system begins in the prestellar phase and proceeds across the subsequent evolutionary phases. The chemical trail from cores to protoplanetary disks to planetary embryos can be studied by comparing distant ... More
Nitrogen isotope fractionation in protoplanetary disksFeb 08 2018May 15 2018Aims: The two stable isotopes of nitrogen, 14N and 15N, exhibit a range of abundance ratios both inside and outside the solar system. The elemental ratio in the solar neighborhood is 440. Recent ALMA observations showed HCN/HC15N ratios from 83 to 156 ... More
Shocks and UV radiation around low-mass protostars: the Herschel-PACS legacyNov 08 2017Far-infrared spectroscopy reveals gas cooling and its underlying heating due to physical processes taking place in the surroundings of protostars. These processes are reflected in both the chemistry and excitation of abundant molecular species. Here, ... More
Exploring organic chemistry in planet-forming zonesDec 13 2012Dec 14 2012Over the last few years, the chemistry of molecules other than CO in the planet-forming zones of disks is starting to be explored with Spitzer and high-resolution ground-based data. However, these studies have focused only on a few simple molecules. The ... More
Molecular dynamics study of photodissociation of water in crystalline and amorphous iceDec 23 2005We present results of classical dynamics calculations, performed to study the photodissociation of water in crystalline and amorphous ice surfaces at a surface temperature of 10 K. Dissociation in the top six monolayers is considered. Desorption of H2O ... More
A cold complex chemistry toward the low-mass protostar B1-b: evidence for complex molecule production in icesMay 04 2010Gas-phase complex organic molecules have been detected toward a range of high- and low-mass star-forming regions at abundances which cannot be explained by any known gas-phase chemistry. Recent laboratory experiments show that UV irradiation of CH3OH-rich ... More
Photodesorption of H2O, HDO, and D2O ice and its impact on fractionationMar 02 2015The HDO/H2O ratio in interstellar gas is often used to draw conclusions on the origin of water in star-forming regions and on Earth. In cold cores and in the outer regions of protoplanetary disks, gas-phase water comes from photodesorption of water ice. ... More
Methanol Along the Path from Envelope to Protoplanetary DiscSep 08 2014Interstellar methanol is considered to be a parent species of larger, more complex organic molecules. A physicochemical simulation of infalling parcels of matter is performed for a low-mass star-forming system to trace the chemical evolution from cloud ... More
Molecular Cloud Structure in the Magellanic Clouds: Effect of MetallicityDec 11 1997Jan 12 1998The chemical structure of neutral clouds in low metallicity environments is examined with particular emphasis on the H to H_2 and C+ to CO transitions. We observed near-IR H_2 lines and the CO J=1-0 line from 30 Doradus and N159/N160 in the Large Magellanic ... More
Matryoshka Holes: Nested Emission Rings in the Transitional Disk Oph IRS 48Sep 07 2012The processes that form transition disks - disks with depleted inner regions - are not well understood; possible scenarios include planet formation, grain growth and photoevaporation. Disks with spatially resolved dust holes are rare, but, in general, ... More