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P. Colom

Bio: P. Colom is an academic researcher from Paris Diderot University. The author has contributed to research in topics: Comet & Radio telescope. The author has an hindex of 18, co-authored 68 publications receiving 1839 citations.


Papers
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Journal Article
TL;DR: In this article, the authors present millimetre and submillimetre observations of comet C/1995 O1 (Hale-Bopp) undertaken near perihelion with the Caltech Submillimeter Observatory and the 30m telescope and Plateau-de-Bure interferometer of the Institut de Radioastronomie Millimetrique.
Abstract: We present millimetre and submillimetre observations of comet C/1995 O1 (Hale-Bopp) undertaken near perihelion with the Caltech Submillimeter Observatory and the 30-m telescope and Plateau-de-Bure interferometer of the Institut de Radioastronomie Millimetrique. From a spectral molecular survey, six new cometary molecular species have been identified for the first time in a comet: SO, SO2, HC3N, NH2CHO, HCOOH, and HCOOCH3. Relative abundances with respect to water are 0.3% (SO), 0.2% (SO2), 0.02% (HC3N), 0.01-0.02% (NH2CHO), 0.09% (HCOOH), and 0.08% (HCOOCH3). Several rotational transitions of OCS and HNCO, whose first identifications were made previously in comet C/1996 B2 (Hyakutake), have also been detected, confirming that these molecular species are ubiquitous compounds of cometary atmospheres. Inferred abundances of OCS and HNCO relative to water in comet Hale-Bopp are 0.4% and 0.1%, respectively. During this observational campaign, we also observed rotational lines of HCN, HNC, CH3CN, CO, CH3OH, H2CO, H2S, and CS. In combination with results of other observations, a comprehensive view of the volatile composition of the coma of comet Hale-Bopp is obtained. A quantitative comparison shows that chemical abundances in comet Hale-Bopp parallel those inferred in interstellar ices, hot molecular cores and bipolar flows around protostars. This suggests that the processes at work in the interstellar medium, in particular grain surface chemistry, played a major role in the formation of cometary ices. It supports models in which cometary volatiles formed in the interstellar medium and suffered little processing in the Solar Nebula.

279 citations

Journal ArticleDOI
TL;DR: A review of radio spectroscopic observations of comets and further analysis of their results is presented in this article, where Bockelee-Morvan et al. present a spectral survey conducted at radio wavelengths in comet Hale-Bopp with the CSO, the IRAM 30-m telescope and Plateau de Bure interferometer.
Abstract: From radio spectroscopic observations of comets, more than 22 molecules, radicals and ions, plus several iso- topologues, were detected, the majority of them being recently revealed in comets C/1996 B2 (Hyakutake) and C/1995 O1 (Hale-Bopp). Among them, 6 molecules were detected for the first time (Bockelee-Morvan et al. 2000) in the course of a spectral survey conducted at radio wavelengths in comet Hale-Bopp with the CSO, the IRAM 30-m telescope and Plateau de Bure interferometer. In addition, many species were searched for unsuccessfully, some of them with stringent upper limits. We present here a review of these observations and further analysis of their results. This include: (i) confirmed detection of acetaldehyde (CH3CHO); (ii) limits on small molecules such as ketene (H2CCO) or methanimine (CH2NH); (iii) limits on the abundance ratios in homologous series such as HC5N/HC3N, ethanol/methanol, acetic acid/formic acid; (iv) searches for precursors of key cometary species such as atomic Na and HNC; (v) constraints on more exotic species ranging from water dimer (H2O)2 to glycine; (vi) detection of the H 34 S isotopic species and independent observations of HDO and DCN; (vii) lim- its on several other deuterated species; (viii) limits on several radicals and ions and a tentative detection of the C2H radical; (ix) the presence of unidentified lines. Typical abundance upper limits of 2-5 ×10 −4 relative to water are achieved for many species. Better upper limits are obtained for some linear molecules with high dipole moments. But more complex molecules such as dimethyl ether or glycine are poorly constrained. These results should give important clues to the chemical composition of cometary ices, to the formation mechanisms of cometary material, and to the chemical processes which occur in the inner coma.

214 citations

Journal ArticleDOI
Karen J. Meech1, N. Ageorges2, Michael F. A'Hearn3, Claude Arpigny4  +205 moreInstitutions (58)
14 Oct 2005-Science
TL;DR: Data show that there was new material after impact that was compositionally different from that seen before impact, and the ratio of dust mass to gas mass in the ejecta was much larger than before impact.
Abstract: On 4 July 2005, many observatories around the world and in space observed the collision of Deep Impact with comet 9P/Tempel 1 or its aftermath. This was an unprecedented coordinated observational campaign. These data show that (i) there was new material after impact that was compositionally different from that seen before impact; (ii) the ratio of dust mass to gas mass in the ejecta was much larger than before impact; (iii) the new activity did not last more than a few days, and by 9 July the comet's behavior was indistinguishable from its pre-impact behavior; and (iv) there were interesting transient phenomena that may be correlated with cratering physics.

182 citations

Journal ArticleDOI
TL;DR: In this article, the production rates of eight molecular species (CO, HCN, CH3OH, H2CO,H2S, CS, CH 3CN,HNC) have been monitored as a function of heliocentric distance.
Abstract: C/1995 O1 (Hale-Bopp) has been observed on a regular basis since August 1995 at millimetre and submillimetre wavelengths using IRAM, JCMT, CSO and SEST radio telescopes. The production rates of eight molecular species (CO, HCN, CH3OH, H2CO,H2S, CS, CH3CN,HNC) have been monitored as a function of heliocentric distance(rh from 7 AU pre-perihelion to 4 AU post-perihelion. As comet Hale-Bopp approached and receded from the Sun, these species displayed different behaviours. Far from the Sun, the most volatile species were found in general relatively more abundant in the coma. In comparison to other species, HNC, H2CO and CS showed a much steeper increase of the production rate with decreasing rh. Less than 1.5 AU from the Sun, the relative abundances were fairly stable and approached those found in other comets near 1 AU. The kinetic temperature of the coma, estimated from the relative intensities of the CH3OH and CO lines, increased with decreasing rh, from about10 K at 7 AU to 110 K around perihelion. The expansion velocity of the gaseous species, derived from the line shapes, also increased with a law close torh 3.

174 citations

Journal ArticleDOI
TL;DR: The presence of numerous complex organic molecules (COMs; defined as those containing six or more atoms) around protostars shows that star formation is accompanied by an increase of molecular complexity.
Abstract: The presence of numerous complex organic molecules (COMs; defined as those containing six or more atoms) around protostars shows that star formation is accompanied by an increase of molecular complexity. These COMs may be part of the material from which planetesimals and, ultimately, planets formed. Comets represent some of the oldest and most primitive material in the solar system, including ices, and are thus our best window into the volatile composition of the solar protoplanetary disk. Molecules identified to be present in cometary ices include water, simple hydrocarbons, oxygen, sulfur, and nitrogen-bearing species, as well as a few COMs, such as ethylene glycol and glycine. We report the detection of 21 molecules in comet C/2014 Q2 (Lovejoy), including the first identification of ethyl alcohol (ethanol, C2H5OH) and the simplest monosaccharide sugar glycolaldehyde (CH2OHCHO) in a comet. The abundances of ethanol and glycolaldehyde, respectively 5 and 0.8% relative to methanol (0.12 and 0.02% relative to water), are somewhat higher than the values measured in solar-type protostars. Overall, the high abundance of COMs in cometary ices supports the formation through grain-surface reactions in the solar system protoplanetary disk.

130 citations


Cited by
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Journal ArticleDOI
TL;DR: The Cologne Database for Molecular Spectroscopy (CDMS) as discussed by the authors contains a catalog of transition frequencies from the radio-frequency to the far-infrared region covering atomic and molecular species that (may) occur in the interstellar or circumstellar medium or in planetary atmospheres.

1,842 citations

Journal ArticleDOI
TL;DR: Our understanding of the evolution of organic molecules and their voyage from molecular clouds to the early solar system and Earth has changed dramatically as discussed by the authors, and our understanding of molecular evolution has been changed dramatically.
Abstract: ▪ Abstract Our understanding of the evolution of organic molecules, and their voyage from molecular clouds to the early solar system and Earth, has changed dramatically. Incorporating recent observ...

877 citations

Journal ArticleDOI
TL;DR: A detailed survey of more than 100 comets has been carried out by as mentioned in this paper, which enabled taxonomic groupings based on free radical species and on crystallinity of rocky grains.
Abstract: Cometary nuclei contain the least modified material from the formative epoch of our planetary system, and their compositions reflect a range of processes experienced by material prior to its incorporation in the cometary nucleus. Dynamical models suggest that icy bodies in the main cometary reservoirs (Kuiper Belt, Oort Cloud) formed in a range of environments in the protoplanetary disk, and (for the Oort Cloud) even in disks surrounding neighboring stars of the Sun's birth cluster. Photometric and spectroscopic surveys of more than 100 comets have enabled taxonomic groupings based on free radical species and on crystallinity of rocky grains. Since 1985, new surveys have provided emerging taxonomies based on the abundance ratios of primary volatiles. More than 20 primary chemical species are now detected in bright comets. Measurements of nuclear spin ratios (in water, ammonia, and methane) and of isotopic ratios (D/H in water and HCN; 14N/15N in CN and HCN) have provided critical insights on factors affec...

849 citations

Journal ArticleDOI
14 Oct 2005-Science
TL;DR: A large increase in organic material occurred during and after the event, with smaller changes in carbon dioxide relative to water, and a thermal map indicates a surface in equilibrium with sunlight.
Abstract: Deep Impact collided with comet Tempel 1, excavating a crater controlled by gravity. The comet's outer layer is composed of 1- to 100-micrometer fine particles with negligible strength ( 1000 kelvins). A large increase in organic material occurred during and after the event, with smaller changes in carbon dioxide relative to water. On approach, the spacecraft observed frequent natural outbursts, a mean radius of 3.0 ± 0.1 kilometers, smooth and rough terrain, scarps, and impact craters. A thermal map indicates a surface in equilibrium with sunlight.

751 citations

Book ChapterDOI
01 Jan 2005
TL;DR: In this article, it is shown that the same chemical pathways are widespread both in the Milky Way and in external galaxies and that the complexity of organic molecules in different space environments is determined by physical and chemical conditions, including density, temperature, ultraviolet radiation and energetic particle flux.
Abstract: Stellar nucleosynthesis of heavy elements, followed by their subsequent release into the interstellar medium, enables the formation of stable carbon compounds in both gas and solid phases. Spectroscopic astronomical observations provide evidence that the same chemical pathways are widespread both in the Milky Way and in external galaxies. The physical and chemical conditions—including density, temperature, ultraviolet radiation and energetic particle flux—determine reaction pathways and the complexity of organic molecules in different space environments. Most of the organic carbon in space is in the form of poorly-defined macromolecular networks. Furthermore, it is also unknown how interstellar material evolves during the collapse of molecular clouds to form stars and planets. Meteorites provide important constraints for the formation of our Solar System and the origin of life. Organic carbon, though only a trace element in these extraterrestrial rock fragments, can be investigated in great detail with sensitive laboratory methods. Such studies have revealed that many molecules which are essential in terrestrial biochemistry are present in meteorites. To understand if those compounds necessarily had any implications for the origin of life on Earth is the objective of several current and future space missions. However, to address questions such as how simple organic molecules assembled into complex structures like membranes and cells, requires interdisciplinary collaborations involving various scientific disciplines. Introduction Life in the Universe is the consequence of the increasing complexity of chemical pathways which led to stable carbon compounds assembling into cells and higher organisms.

722 citations