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Session PCMI-PNPS-PNP

Une exploration des objets Trans-Neptuniens avec Herschel
A. Delsanti
(Laboratoire d'Astrophysique de Marseille)
Over a thousand of minor bodies are known to orbit the Sun in a region located beyond Neptune (the Trans-Neptunian Objects, or TNOs). These objects are the most primitive remnants of the planetesimal disk from which the outer planets formed. Their study can provide important constraints on the formation and evolution of the Solar System. The physical properties of these objects are only beginning to be unveiled. Crucial parameters such as size, albedo, density and thermal properties are difficult to assess, and can mainly be derived from far-IR wavelength measurements.

The Herschel Open Time key program "TNOs are cool: a survey of the Trans-Neptunian region" (Mueller et al. 2009, Earth Moon and Planets 105, 209-219) is providing us a unique opportunity to explore the thermal and physical properties of about 140 minor bodies of the outer Solar System (TNOs and Centaurs). We will review the results obtained during the early phase of observation of the Herschel Space Observatory, and present the forthcoming studies.



The first steps of interstellar chemistry revealed by Herschel/HIFI
E. Falgarone on behalf of the PRISMAS team
(Observatoire de Paris & Ecole Normale Supérieure)
The Herschel/HIFI key-project PRISMAS was designed to shed light on the first steps of interstellar chemistry, among which those taking place in the diffuse medium, weakly shielded from the UV radiation field. The results obtained so far go beyond our expectations. The absorption lines of HF, OH+, H2O+ and CH+ obtained in the direction of remote star forming regions provide new sensitive probes of the diffuse medium, including those containing only a small fraction of molecular hydrogen. They also reveal the processes driving this specific chemistry (turbulent dissipation, cosmic ray ionization).


Preliminary work to ALMA, HERSCHEL, SOFIA: submillimeter wave spectroscopy of isotopic species of methyl formate.
Goubet, M., Margulès, L., Motiyenko, R., Bailleux, S., Huet, T. & Wlodarczak, G.
(Laboratoire Phlam)
Complex organic molecules are relatively heavy, their maximum absorption is in the millimetric domain at about 300 GHz. But the most abondant, like methyl formate, could be detected in the ISM up to 900 GHz (Comito et al. 2005). We will present here the last results obtained about the two 18O and the doubly-deuterated species of methyl formate. This concludes the systematic investigation up to 660 GHz for the mono-substituted isotopic species with either 13C, 18O, or D, which began in 2006. The lines from these isotopic species will certainly be present in the spectra which will be recorded in the next years with the very sensitive telescope ALMA, HERSHEL and SOFIA. The detection of isotopic species is very important for the astrophysical community to improve the interstellar chemical modeling and to understand the formation mechanism of these complex organic molecules. Our interest was also on the theoretical aspects. Like other complex organic molecules, methyl formate displays a large amplitude motion. Here it is the rotation of the methyl group with respect to the rest of the molecule. Theoretical models were developed to reproduce accurately the observed frequencies for large quantum numbers values as J-values as high as 70 could be reached. Similarly the investigation of the doubly-deuterated HCOOCHD2 was undertaken to test the model developed for mono-deuterated HCOOCH2D (Margulès et al. 2009). This work is supported by ANR-08-BLAN-0054 and ANR-08-BLAN-0225.

- Comito, C., Schilke, P., Phillips, T.G., et al. 2005, Astrophys. J. Supp., 156, 127 - Margulès, L., Coudert, L.H., Mollendal, H., et al. 2009, J. Mol. Spec., 254, 55



SPIRE spectroscopy of the interstellar medium
E. Habart, A. Abergel, E. Dartois, D. Naylor, E. Polehampton, J.-P. Baluteau, A. Zavagno, C. Joblin and the SAG 4 consortium
(Institut d'Astrophysique Spatiale (IAS))
The SPIRE Fourier Transform Spectrometer (FTS) on-board Herschel allows us, for the first time, to simultaneously measure the complete far-infrared spectrum from 194 to 671 microns. A wealth of rotational lines of CO (and its isotopologues), fine structure lines of C and N+, and emission lines from radicals and molecules has already been observed towards several galactic regions and nearby galaxies. The strengths of the atomic and molecular lines place fundamental constraints on the physical conditions but also the chemistry of the interstellar medium (ISM). FTS mapping capabilities are also extremely powerful in characterizing the spatial morphology of the extended region and understand how the gas properties vary within the studied region. A first analysis of FTS observations of selected galactic sources with precise excitation conditions and geometry including HII regions, photodissociation regions (PDRs) and molecular cloud cores will be presented. This study as part of the SPIRE ISM consortium key program (Abergel et al. 2010) illustrates the promise of the FTS for the study of the ISM and emphasizes the need for complementary spectroscopic data to be obtained from HIFI, PACS and ground-based instruments.


Herschel/HIFI révéle les premières phases de la formation stellaire
F. Herpin, L. Chavarria, S. Bontemps, T. Jacq, J. Braine, A. Baudry, F. van der Tak, F. Wyrowski, E. van Dishoeck
(LAB/OASU)
The understanding of the star formation is still on progress. Especially, the formation of high-mass stars is much less understood than the low-mass case: even the time order of observational phenomena is uncertain. Water, one of the most important molecules in the Universe, might elucidate key episodes in the process of stellar birth, and especially could be a major role in the formation of high-mass stars. For both types of stars, the source chemical composition is not well known and even less known is the chemical evolution of the interstellar matter throughout the various phases of star formation.

This talk presents the first results of the various Herschel Space Observatory star formation key-programs. One of the instruments on-board HSO, HIFI, is the most powerful spectrometer never built, covering a huge frequency range, most of them unaccessible from ground. In particular, one of the KP, WISH, aims at following the process of star formation during the various stages and at using the water as a physical diagnostic throughout the evolution. The HIFI instrument is used to make maps and spectra of $\sim$20 lines in $\sim$20 sources spanning a large range in physical parameters, from pre-stellar cores to UCHII regions.

I will review the status of the programs and focus specifically on the spectroscopic results. I will show how powerful are the HIFI high-resolution spectral observations to resolve different physical source components such as the dense core, the outflows or the extended cold cloud aroung the object.



Premiers résultats Herschel sur les disques proto-planétaires
C.Pinte, F. Menard
(LAOG, Grenoble)
TBW


La base de données cinétiques pour l'Astrochimie : KIDA
V. Wakelam
(Laboratoire d'Astrophysique de Bordeaux)
KIDA (for KInetic Database for Astrochemistry) is a project initiated by different communities in order to 1) improve the interaction between astrochemists and physico-chemists and 2) simplify the work of modeling the chemistry of astrophysical environments. Here astrophysical environments stand for the interstellar medium and planetary atmospheres. Both types of environments use similar chemical networks and the physico-chemists who work on the determination of reaction rate coefficients for both types of environment are the same.



Rates of excitation for molecules of astrochemical relevance
L. Wiesenfeld, A. Faure
(Laboratoire d'Astrophysique de Grenoble)
We have set up a framework for calculating in a precise and controlled way the collisional properties of several molecules of astrophysical meaning. The collisional properties of molecules help in understanding the excitation scheme of the various rotational levels, observed by the ground telescopes in the cm- sub mm spectral regions as well as by the newly launched Herschel space telescope, with a special emphasis to the heterodyne spectrometer HIFI.

We have been very successful in calculating and assessing the properties of some of the main molecules observed in astrophysical media. The quantities that are relevant for astrophysics are rotational and vibrational quenching/excitation rates by means of collisions of H2 : we have dealt with H2O and with some organic molecules (CO, HC3N, H2CO, NH3) as well as the isotopomers of some of those species. We calculate those rates by means of successively determining an intermolecular potential energy surface and calculating inelastic cross sections and rates classically and/or quantum mechanically.

We use these rates for simulating and interpreting some astrophysical spectra with a special emphasis on star forming regions. We compare the inelastic cross-sections with experiments performed in laboratory conditions relevant for the analysis of the ISM.



Dust silicate emission in FIR/submm
Anne Coupeaud, Karine Demyk, Claude Meny and Céline Nayral
(CESR)
The observations of PRONAOS and Archeops in the submillimeter wavelength range revealed a dependence with temperature of the spectral index of the dust emissivity $\beta$. This parameter is of a great importance since it is used for the estimation of the dust mass. Our goal is to characterize and to explain the unusual optical properties of the big silicate grains with temperature in this domain of long wavelengths. With the experimental set-up ESPOIRS (Etude Spectroscopique des Propriétés Optiques dans l'InfraRouge et le Submillimétrique des analogues de poussière) we performed some experiments on absorption properties (5-1000 $\mu$m) of analogues interstellar grains in function of the temperature (300K to 4K). This study is very helpful for the interpretation of the data of Herschel and Planck.


Initial highlights of the Herschel imaging Survey of OB Young Stellar Objects (HOBYS)
T. Hill, F. Motte, A. Zavagno, S. Bontemps, N. Schneider, M. Hennemann, J. di Francesco and the HOBYS consortium
(CEA/Saclay)
I will present highlights from the Herschel key program HOBYS obtained during the science demonstration and early routine phases (Motte, Zavagno, Bontemps, et al.).

- The multi-wavelength Herschel images of Rosette reveal a clear dust temperature gradient in the molecular cloud, demonstrating the strong influence of the NGC6334 UV field and winds on the cloud. These results make Rosette one of the best regions to investigate the relative importance of triggered versus spontaneous star formation (Schneider et al. 2010). - The spatial resolution and sensitivity of these Herschel images allows us to pinpoint individual high- and low-mass protostars within the cloud. The PACS images in particular reveal young clusters of protostars. Spectral energy distributions, using Herchel (SPIRE and PACS) as well as Spitzer, provides robust measurements of a protostar's mass and luminosity. The evolutionary diagram (M_env vs L_bol) of Rosette protostars complements such diagrams drawn for low-mass star-forming regions (Hennemann et al. 2010). - Several hundred $\sim$0.5 pc clumps have been identified in Rosette covering a large range in the mass spectrum compared with e.g. the Gould-belt survey. We will investigate variations of the cloud structure (mass spectrum, gas concentration, gravitational boundedness,...) as a function of the distance to the O stars (Di Francesco et al. 2010). A comparison with the results obtained for the high-mass star-forming region NGC7538 will be made (Reid et al.). - The properties of the YSO population on the borders of the Galactic HII regions RCW 120 and Sh104 are reported. A series of red sources, not previously detected, which may represent the early stages of star formation are seen in the PACS and SPIRE bands. SEDs constrain, their physical properties (mass, age, evolution stage) allowing us to discuss how the HII region has triggered the formation of a new generation of stars (Zavagno et al. 2010). -These Herschel images of Rosette and NGC7538 provide the first unbiased and complete census of their OB-type young stellar objects including high-mass infrared-quiet protostars, which were overlooked by Spitzer.

The fundamental properties (luminosity and mass) of YSOs in the HOBYS fields will be used to constrain their evolutionary stage and lifetime of intermediate- and high-mass YSOs, ultimately improving our understanding of high-mass star formation.



Dust properties within molecular clouds as seen by Herschel using a new spectral inversion technique
D.J. Marshall, L. Anderson, J-Ph. Bernard, C. Brunt, M. Huang, P. Martin, L. Montier, J. Mottram, D. Paradis, I. Ristorcelli1, & J. Rodon
(CESR)
The dust properties inferred from the observed dust spectral energy distribution provides us with crucial information on the physical state of the interstellar medium. The conditions within molecular clouds are particularly interesting as these are the future sites for star formation. However, the derivation of dust properties within molecular clouds is not trivial as many line of sight components contribute to the dust emission. I will present a new spectral inversion method with which it is possible to obtain the dust properties within individual molecular cores. For several of the molecular cores, the derived temperatures of the dust is seen to be higher than in the surrounding HI. This shows that the heating source is embedded in the core, making these objects new "hot molecular core" candidates.


Herschel-PACS observation of the T Tauri disk TW Hya: constraining the disk dust and gas mass
Wing-Fai Thi & Herschel-GASPS team
(Laboratoire d'Astrophysics de Grenoble)
We present Herschel-PACS observations of the disk around the TTauri star TW Hya. We complement this with continuum data and ground-based 12CO 3-2 and 13CO 3-2 observations. We model the continuum and the line fluxes with the 3D Monte-Carlo code MCFOST and the thermo-chemical code ProDiMo. We detect the [OI] line at 63 but the [OI] line at 145 micron and the [CII] line at 157 micron. Preliminary modeling suggests a dust mass for grains with radius < 1 mm of $\sim$1.9E-4 Msun (total solid mass of 3E-3 Msun) and a gas mass of (0.5-5)E-3 Msun.


Star formation triggered by Galactic HII regions: first results from the Herschel Space Observatory
Zavagno, A., Anderson, L.D., Russeil, D., Rodon, J.A., Deharveng, L., Baluteau, J.-P., Motte, F., Bontemps, S., Abergel, A., Molinari, S.
(LAM)
We present the first results obtained with the Herschel Space Observatory on a sample of Galactic HII regions that show triggered star formation on their borders. The Herschel satellite reveals a population of young, highly embedded sources never seen before. The large wavelength coverage of the Herschel satellite allows us to characterize, for the first time, the physical properties of these young sources. We will show how Herschel opens a new window in this research field and present the rich perspectives offered.




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suivant: Poster contributions monter: sf2a_boa précédent: Poster contributions
Samuel Boissier 2010-06-16