Showing papers by "Pierre Royer published in 2010"
Max Planck Society1, Katholieke Universiteit Leuven2, French Alternative Energies and Atomic Energy Commission3, University of Liège4, Spanish National Research Council5, University of Vienna6, European Space Agency7, European Southern Observatory8, Austrian Institute of Technology9, Graz University of Technology10, European Laboratory for Non-Linear Spectroscopy11, Konkoly Thege Miklós Astronomical Institute12
TL;DR: The Photodetector Array Camera and Spectrometer (PACS) as discussed by the authors is one of the three science instruments on ESA's far infrared and sub-mil- limetre observatory.
Abstract: The Photodetector Array Camera and Spectrometer (PACS) is one of the three science instruments on ESA's far infrared and submil- limetre observatory. It employs two Ge:Ga photoconductor arrays (stressed and unstressed) with 16 × 25 pixels, each, and two filled silicon bolometer arrays with 16 × 32 and 32 × 64 pixels, respectively, to perform integral-field spectroscopy and imaging photom- etry in the 60−210 μm wavelength regime. In photometry mode, it simultaneously images two bands, 60−85 μ mo r 85−125 μ ma nd 125−210 μm, over a field of view of ∼1.75 � × 3.5 � , with close to Nyquist beam sampling in each band. In spectroscopy mode, it images afi eld of 47 �� × 47 �� , resolved into 5 × 5 pixels, with an instantaneous spectral coverage of ∼ 1500 km s −1 and a spectral resolution of ∼175 km s −1 . We summarise the design of the instrument, describe observing modes, calibration, and data analysis methods, and present our current assessment of the in-orbit performance of the instrument based on the performance verification tests. PACS is fully operational, and the achieved performance is close to or better than the pre-launch predictions.
2,645 citations
Paris Diderot University1, INAF2, Cardiff University3, Herzberg Institute of Astrophysics4, Rutherford Appleton Laboratory5, Open University6, University of Paris-Sud7, Max Planck Society8, Katholieke Universiteit Leuven9, McMaster University10, University of Provence11, University of Toulouse12, Chinese Academy of Sciences13, University of Toronto14, Institut d'Astrophysique de Paris15, European Space Research and Technology Centre16, UK Astronomy Technology Centre17
TL;DR: In this paper, the first results from the Gould Belt survey, obtained toward the Aquila Rift and Polaris Flare regions during the'science demonstration phase' of Herschel, were summarized.
Abstract: We summarize the first results from the Gould Belt survey, obtained toward the Aquila Rift and Polaris Flare regions during the 'science demonstration phase' of Herschel. Our 70-500 micron images taken in parallel mode with the SPIRE and PACS cameras reveal a wealth of filamentary structure, as well as numerous dense cores embedded in the filaments. Between ~ 350 and 500 prestellar cores and ~ 45-60 Class 0 protostars can be identified in the Aquila field, while ~ unbound starless cores and no protostars are observed in the Polaris field. The prestellar core mass function (CMF) derived for the Aquila region bears a strong resemblance to the stellar initial mass function (IMF), already confirming the close connection between the CMF and the IMF with much better statistics than earlier studies. Comparing and contrasting our Herschel results in Aquila and Polaris, we propose an observationally-driven scenario for core formation according to which complex networks of long, thin filaments form first within molecular clouds, and then the densest filaments fragment into a number of prestellar cores via gravitational instability.
1,542 citations
INAF1, University of Colorado Boulder2, University College London3, University of Toulouse4, University of Toronto5, Liverpool John Moores University6, California Institute of Technology7, University of Calgary8, European Southern Observatory9, University of Provence10, University of Paris-Sud11, Paris Diderot University12, Katholieke Universiteit Leuven13, University of Bordeaux14, University of Exeter15, University of New South Wales16, University of Leeds17, Spanish National Research Council18, Sapienza University of Rome19, University of Rome Tor Vergata20, Nagoya University21, University of Manchester22, University of Paris23, Jet Propulsion Laboratory24, Cardiff University25, Chinese Academy of Sciences26, Laval University27, University of Helsinki28, Harvard University29, Max Planck Society30, University of Hertfordshire31, University of Cologne32, University of Kent33, Open University34
TL;DR: In this paper, the first results from the science demonstration phase for the Hi-GAL survey, the Herschel key program that will map the inner Galactic plane of the Milky Way in 5 bands, were presented.
Abstract: We present the first results from the science demonstration phase for the Hi-GAL survey, the Herschel key program that will map the inner Galactic plane of the Milky Way in 5 bands. We outline our data reduction strategy and present some science highlights on the two observed 2° × 2° tiles approximately centered at l = 30° and l = 59°. The two regions are extremely rich in intense and highly structured extended emission which shows a widespread organization in filaments. Source SEDs can be built for hundreds of objects in the two fields, and physical parameters can be extracted, for a good fraction of them where the distance could be estimated. The compact sources (which we will call cores' in the following) are found for the most part to be associated with the filaments, and the relationship to the local beam-averaged column density of the filament itself shows that a core seems to appear when a threshold around AV ~ 1 is exceeded for the regions in the l = 59° field; a AV value between 5 and 10 is found for the l = 30° field, likely due to the relatively higher distances of the sources. This outlines an exciting scenario where diffuse clouds first collapse into filaments, which later fragment to cores where the column density has reached a critical level. In spite of core L/M ratios being well in excess of a few for many sources, we find core surface densities between 0.03 and 0.5 g cm-2. Our results are in good agreement with recent MHD numerical simulations of filaments forming from large-scale converging flows.
752 citations
TL;DR: In this paper, the first results from the science demonstration phase for the Hi-GAL survey, the Herschel key-project that will map the inner Galactic Plane of the Milky Way in 5 bands are presented.
Abstract: We present the first results from the science demonstration phase for the Hi-GAL survey, the Herschel key-project that will map the inner Galactic Plane of the Milky Way in 5 bands. We outline our data reduction strategy and present some science highlights on the two observed 2{\deg} x 2{\deg} tiles approximately centered at l=30{\deg} and l=59{\deg}. The two regions are extremely rich in intense and highly structured extended emission which shows a widespread organization in filaments. Source SEDs can be built for hundreds of objects in the two fields, and physical parameters can be extracted, for a good fraction of them where the distance could be estimated. The compact sources (which we will call 'cores' in the following) are found for the most part to be associated with the filaments, and the relationship to the local beam-averaged column density of the filament itself shows that a core seems to appear when a threshold around A_V of about 1 is exceeded for the regions in the l=59{\deg} field; a A_V value between 5 and 10 is found for the l=30{\deg} field, likely due to the relatively larger distances of the sources. This outlines an exciting scenario where diffuse clouds first collapse into filaments, which later fragment to cores where the column density has reached a critical level. In spite of core L/M ratios being well in excess of a few for many sources, we find core surface densities between 0.03 and 0.5 g cm-2. Our results are in good agreement with recent MHD numerical simulations of filaments forming from large-scale converging flows.
735 citations
TL;DR: Hi-GAL as mentioned in this paper is an open-time key project of the Herschel Space Observatory, which aims to detect the earliest phases of the formation of molecular clouds and high-mass stars.
Abstract: Hi-GAL, the Herschel infrared Galactic Plane Survey, is an Open Time Key Project of the Herschel Space Observatory. It will make an unbiased photometric survey of the inner Galactic plane by mapping a 2° wide strip in the longitude range ∣l∣ < 60° in five wavebands between 70 μm and 500 μm. The aim of Hi-GAL is to detect the earliest phases of the formation of molecular clouds and high-mass stars and to use the optimum combination of Herschel wavelength coverage, sensitivity, mapping strategy, and speed to deliver a homogeneous census of star-forming regions and cold structures in the interstellar medium. The resulting representative samples will yield the variation of source temperature, luminosity, mass and age in a wide range of Galactic environments at all scales from massive YSOs in protoclusters to entire spiral arms, providing an evolutionary sequence for the formation of intermediate and high-mass stars. This information is essential to the formulation of a predictive global model of the role of environment and feedback in regulating the star-formation process. Such a model is vital to understanding star formation on galactic scales and in the early universe. Hi-GAL will also provide a science legacy for decades to come with incalculable potential for systematic and serendipitous science in a wide range of astronomical fields, enabling the optimum use of future major facilities such as JWST and ALMA.
579 citations
Max Planck Society1, Katholieke Universiteit Leuven2, French Alternative Energies and Atomic Energy Commission3, University of Liège4, Spanish National Research Council5, University of Vienna6, European Space Agency7, European Southern Observatory8, Austrian Institute of Technology9, Graz University of Technology10, European Laboratory for Non-Linear Spectroscopy11, Konkoly Thege Miklós Astronomical Institute12
TL;DR: The Photodetector Array Camera and Spectrometer (PACS) as discussed by the authors is one of the three science instruments on ESA's far infrared and submillimetre observatory.
Abstract: The Photodetector Array Camera and Spectrometer (PACS) is one of the three science instruments on ESA's far infrared and submillimetre observatory. It employs two Ge:Ga photoconductor arrays (stressed and unstressed) with 16x25 pixels, each, and two filled silicon bolometer arrays with 16x32 and 32x64 pixels, respectively, to perform integral-field spectroscopy and imaging photometry in the 60-210\mu\ m wavelength regime. In photometry mode, it simultaneously images two bands, 60-85\mu\ m or 85-125\mu\m and 125-210\mu\ m, over a field of view of ~1.75'x3.5', with close to Nyquist beam sampling in each band. In spectroscopy mode, it images a field of 47"x47", resolved into 5x5 pixels, with an instantaneous spectral coverage of ~1500km/s and a spectral resolution of ~175km/s. We summarise the design of the instrument, describe observing modes, calibration, and data analysis methods, and present our current assessment of the in-orbit performance of the instrument based on the Performance Verification tests. PACS is fully operational, and the achieved performance is close to or better than the pre-launch predictions.
127 citations
Paris Diderot University1, INAF2, Cardiff University3, Herzberg Institute of Astrophysics4, Open University5, Rutherford Appleton Laboratory6, University of Paris-Sud7, Max Planck Society8, Katholieke Universiteit Leuven9, McMaster University10, University of Provence11, University of Toulouse12, Chinese Academy of Sciences13, University of Toronto14, Institut d'Astrophysique de Paris15, European Space Research and Technology Centre16, UK Astronomy Technology Centre17
TL;DR: In this paper, the first results from the Gould Belt survey, obtained toward the Aquila Rift and Polaris Flare regions during the'science demonstration phase' of Herschel, were summarized.
Abstract: We summarize the first results from the Gould Belt survey, obtained toward the Aquila Rift and Polaris Flare regions during the 'science demonstration phase' of Herschel. Our 70-500 micron images taken in parallel mode with the SPIRE and PACS cameras reveal a wealth of filamentary structure, as well as numerous dense cores embedded in the filaments. Between ~ 350 and 500 prestellar cores and ~ 45-60 Class 0 protostars can be identified in the Aquila field, while ~ unbound starless cores and no protostars are observed in the Polaris field. The prestellar core mass function (CMF) derived for the Aquila region bears a strong resemblance to the stellar initial mass function (IMF), already confirming the close connection between the CMF and the IMF with much better statistics than earlier studies. Comparing and contrasting our Herschel results in Aquila and Polaris, we propose an observationally-driven scenario for core formation according to which complex networks of long, thin filaments form first within molecular clouds, and then the densest filaments fragment into a number of prestellar cores via gravitational instability.
116 citations
University of Amsterdam1, Katholieke Universiteit Leuven2, Spanish National Research Council3, Janssen Pharmaceutica4, University College London5, University of Lethbridge6, Rutherford Appleton Laboratory7, Max Planck Society8, Cardiff University9, Royal Observatory of Belgium10, UK Astronomy Technology Centre11, Institut Universitaire de France12, University of Vienna13, Stockholm University14
TL;DR: Dozens of water vapour lines in the far-infrared and sub-millimetre spectrum of IRC +10216 are detected using the Herschel satellite, and a plausible explanation for the warm water appears to be the penetration of ultraviolet photons deep into a clumpy circumstellar envelope.
Abstract: The detection of circumstellar water vapour around the ageing carbon star IRC +10216 challenged the current understanding of chemistry in old stars, because water was predicted to be almost absent in carbon-rich stars. Several explanations for the water were postulated, including the vaporization of icy bodies (comets or dwarf planets) in orbit around the star1, grain surface reactions, and photochemistry in the outer circumstellar envelope. With a single water line detected so far from this one carbon-rich evolved star, it is difficult to discriminate between the different mechanisms proposed. Here we report the detection of dozens of water vapour lines in the far-infrared and sub-millimetre spectrum of IRC +1021 using the Herschel satellite. This includes some high-excitation lines with energies corresponding to ~1,000 K, which can be explained only if water is present in the warm inner sooty region of the envelope. A plausible explanation for the warm water appears to be the penetration of ultraviolet photons deep into a clumpy circumstellar envelope. This mechanism also triggers the formation of other molecules, such as ammonia, whose observed abundances6 are much higher than hitherto predicted.
110 citations
UK Astronomy Technology Centre1, Katholieke Universiteit Leuven2, University of St Andrews3, Paris Diderot University4, Stockholm University5, University College London6, Max Planck Society7, University of California, Berkeley8, Herzberg Institute of Astrophysics9, Radboud University Nijmegen10, University of Amsterdam11, Cardiff University12, ETH Zurich13, University of Texas at Austin14, University of Colorado Boulder15, Leiden University16, University of Edinburgh17, Rutherford Appleton Laboratory18, Chalmers University of Technology19, University of Lethbridge20
TL;DR: In this paper, five band imaging of the Vega debris disc obtained using the Herschel Space Observatory is presented, with full-width half-maximum angular resolutions of 5.6-36.9 ''.
Abstract: We present five band imaging of the Vega debris disc obtained using the Herschel Space Observatory. These data span a wavelength range of 70-500 mu m with full-width half-maximum angular resolutions of 5.6-36.9 ''. The disc is well resolved in all bands, with the ring structure visible at 70 and 160 mu m. Radial profiles of the disc surface brightness are produced, and a disc radius of 11 '' (similar to 85AU) is determined. The disc is seen to have a smooth structure thoughout the entire wavelength range, suggesting that the disc is in a steady state, rather than being an ephemeral structure caused by the recent collision of two large planetesimals.
71 citations
TL;DR: In this paper, five-band imaging of the Vega debris disc obtained using the Herschel Space Observatory is presented, with full-width half-maximum angular resolutions of 5.6-36.9".
Abstract: We present five band imaging of the Vega debris disc obtained using the Herschel Space Observatory. These data span a wavelength range of 70-500 um with full-width half-maximum angular resolutions of 5.6-36.9". The disc is well resolved in all bands, with the ring structure visible at 70 and 160 um. Radial profiles of the disc surface brightness are produced, and a disc radius of 11" (~ 85 AU) is determined. The disc is seen to have a smooth structure thoughout the entire wavelength range, suggesting that the disc is in a steady state, rather than being an ephemeral structure caused by the recent collision of two large planetesimals.
56 citations
TL;DR: In this paper, a comparison with existing molecular CO material shows a high degree of correlation for TT Cyg and U Ant but a few distinct differences with other observables are also found.
Abstract: Detached circumstellar dust shells are detected around three carbon variables using Herschel-PACS. Two of them are already known on the basis of their thermal CO emission and two are visible as extensions in IRAS imaging data. By model fits to the new data sets, physical sizes, expansion timescales, dust temperatures, and more are deduced. A comparison with existing molecular CO material shows a high degree of correlation for TT Cyg and U Ant but a few distinct differences with other observables are also found.
TL;DR: In this paper, a comparison with existing molecular CO material shows a high degree of correlation for TT Cyg and U Ant but a few distinct differences with other observables are also found.
Abstract: Detached circumstellar dust shells are detected around three carbon variables using Herschel-PACS. Two of them are already known on the basis of their thermal CO emission and two are visible as extensions in IRAS imaging data. By model fits to the new data sets, physical sizes, expansion timescales, dust temperatures, and more are deduced. A comparison with existing molecular CO material shows a high degree of correlation for TT Cyg and U Ant but a few distinct differences with other observables are also found.
Spanish National Research Council1, Katholieke Universiteit Leuven2, University of Amsterdam3, University College London4, Janssen Pharmaceutica5, Rutherford Appleton Laboratory6, University of Lethbridge7, Max Planck Society8, Cardiff University9, Royal Observatory of Belgium10, UK Astronomy Technology Centre11, University of Vienna12, Stockholm University13
TL;DR: In this paper, anhydrous hydrochloric acid (hydrogen chlorine, HCl) was detected in the carbon-rich star IRC+10216 using the spectroscopic facilities onboard the Herschel satellite.
Abstract: We report on the detection of anhydrous hydrochloric acid (hydrogen chlorine, HCl) in the carbon-rich star IRC+10216 using the spectroscopic facilities onboard the Herschel satellite. Lines from J = 1-0 up to J = 7-6 have been detected. From the observed intensities, we conclude that HCl is produced in the innermost layers of the circumstellar envelope with an abundance relative to H-2 of 5 x 10(-8) and extends until the molecules reach its photodissociation zone. Upper limits to the column densities of AlH, MgH, CaH, CuH, KH, NaH, FeH, and other diatomic hydrides have also been obtained.
Royal Observatory of Belgium1, University College London2, Katholieke Universiteit Leuven3, UK Astronomy Technology Centre4, University of Denver5, University of California, Berkeley6, University of Kentucky7, Cardiff University8, Rutherford Appleton Laboratory9, Stockholm University10, University of Lethbridge11
TL;DR: In this paper, a photoionization model of the Ring nebula with the Cloudy code was developed to determine the physical conditions of the dust and investigate possible formation scenarios for the H2.
Abstract: Herschel PACS and SPIRE images have been obtained of NGC 6720 (the Ring nebula). This is an evolved planetary nebula with a central star that is currently on the cooling track, due to which the outer parts of the nebula are recombining. From the PACS and SPIRE images we conclude that there is a striking resemblance between the dust distribution and the H2 emission, which appears to be observational evidence that H2 forms on grain surfaces. We have developed a photoionization model of the nebula with the Cloudy code which we used to determine the physical conditions of the dust and investigate possible formation scenarios for the H2. We conclude that the most plausible scenario is that the H2 resides in high density knots which were formed after the recombination of the gas started when the central star entered the cooling track. Hydrodynamical instabilities due to the unusually low temperature of the recombining gas are proposed as a mechanism for forming the knots. H2 formation in the knots is expected to be substantial after the central star underwent a strong drop in luminosity about one to two thousand years ago, and may still be ongoing at this moment, depending on the density of the knots and the properties of the grains in the knots.
TL;DR: In this paper, a photoionization model of the Ring Nebula with the Cloudy code was developed to determine the physical conditions of the dust and investigate possible formation scenarios for the H2.
Abstract: Herschel PACS and SPIRE images have been obtained of NGC 6720 (the Ring Nebula). This is an evolved planetary nebula with a central star that is currently on the cooling track, due to which the outer parts of the nebula are recombining. From the PACS and SPIRE images we conclude that there is a striking resemblance between the dust distribution and the H2 emission, which appears to be observational evidence that H2 forms on grain surfaces. We have developed a photoionization model of the nebula with the Cloudy code which we used to determine the physical conditions of the dust and investigate possible formation scenarios for the H2. We conclude that the most plausible scenario is that the H2 resides in high density knots which were formed after the recombination of the gas started when the central star entered the cooling track. Hydrodynamical instabilities due to the unusually low temperature of the recombining gas are proposed as a mechanism for forming the knots. H2 formation in the knots is expected to be substantial after the central star underwent a strong drop in luminosity about one to two thousand years ago, and may still be ongoing at this moment, depending on the density of the knots and the properties of the grains in the knots.
TL;DR: In this article, anhydrous hydrochloric acid (hydrogen chlorine, HCl) was detected in the carbon-rich star IRC+10216 using the spectroscopic facilities onboard the Herschel satellite.
Abstract: We report on the detection of anhydrous hydrochloric acid (hydrogen chlorine, HCl) in the carbon-rich star IRC +10216 using the spectroscopic facilities onboard the Herschel satellite. Lines from J = 1–0 up to J = 7–6 have been detected. From the observed intensities, we conclude that HCl is produced in the innermost layers of the circumstellar envelope with an abundance relative to H2 of 5 × 10-8 and extends until the molecules reach its photodissociation zone. Upper limits to the column densities of AlH, MgH, CaH, CuH, KH, NaH, FeH, and other diatomic hydrides have also been obtained.
TL;DR: In this paper, the authors obtained Herschel PACS and SPIRE images of the thermal emission of the debris disk around the A5V star, and used them to complete the SED over a few octaves in wavelength that had been previously inaccessible.
Abstract: We obtained Herschel PACS and SPIRE images of the thermal emission of the debris disk around the A5V star {\beta} Pic. The disk is well resolved in the PACS filters at 70, 100, and 160 {\mu}m. The surface brightness profiles between 70 and 160 {\mu}m show no significant asymmetries along the disk, and are compatible with 90% of the emission between 70 and 160 {\mu}m originating in a region closer than 200 AU to the star. Although only marginally resolving the debris disk, the maps obtained in the SPIRE 250 - 500 {\mu}m filters provide full-disk photometry, completing the SED over a few octaves in wavelength that had been previously inaccessible. The small far-infrared spectral index ({\beta} = 0.34) indicates that the grain size distribution in the inner disk (<200AU) is inconsistent with a local collisional equilibrium. The size distribution is either modified by non-equilibrium effects, or exhibits a wavy pattern, caused by an under-abundance of impactors which have been removed by radiation pressure.
Katholieke Universiteit Leuven1, University College London2, University of Denver3, University of California, Berkeley4, University of Amsterdam5, Cardiff University6, UK Astronomy Technology Centre7, University of Vienna8, Rutherford Appleton Laboratory9, Stockholm University10, University of Lethbridge11
TL;DR: Sahai et al. as discussed by the authors used the far-IR images of the archetype carbon star CW Leo (IRC +10216) by the Herschel Space Observatory (Pilbratt et al., 2010) to show an extended structure at about 11′ from the star which correlates with the UV structure seen by the GALaxy Evolution EXplorer Space Observatory.
Abstract: Far-IR (FIR) images of the archetype carbon star CW Leo (IRC +10216) by the Herschel Space Observatory (Pilbratt et al. 2010) reveal an extended structure at about 11′ from the star which correlates with the UV structure seen by the GALaxy Evolution EXplorer Space Observatory (GALEX) (Sahai & Chronopoulos 2010). The UV emission is believed to be due to the shocked asymptotic giant branch (AGB) wind with the interstellar medium (ISM) (Sahai & Chronopoulos). We present our main results from the Herschel data on the wind–ISM interaction.
Katholieke Universiteit Leuven1, UK Astronomy Technology Centre2, Paris Diderot University3, Stockholm University4, University of Amsterdam5, Radboud University Nijmegen6, University College London7, Max Planck Society8, University of California, Berkeley9, Herzberg Institute of Astrophysics10, European Space Research and Technology Centre11, Cardiff University12, ETH Zurich13, University of St Andrews14, University of Texas at Austin15, University of Colorado Boulder16, Leiden University17, University of Edinburgh18, Rutherford Appleton Laboratory19, Chalmers University of Technology20, University of Lethbridge21
TL;DR: In this paper, the authors obtained Herschel PACS and SPIRE images of the thermal emission of the debris disk around the A5V star beta Pic and used them to complete the SED over a few octaves in wavelength that had been previously inaccessible.
Abstract: We obtained Herschel PACS and SPIRE images of the thermal emission of the debris disk around the A5V star beta Pic. The disk is well resolved in the PACS filters at 70, 100, and 160 mu m. The surface brightness profiles between 70 and 160 mu m show no significant asymmetries along the disk, and are compatible with 90% of the emission between 70 and 160 mu m originating in a region closer than 200 AU to the star. Although only marginally resolving the debris disk, the maps obtained in the SPIRE 250-500 mu m filters provide full-disk photometry, completing the SED over a few octaves in wavelength that had been previously inaccessible. The small far-infrared spectral index (beta = 0.34) indicates that the grain size distribution in the inner disk (<200 AU) is inconsistent with a local collisional equilibrium. The size distribution is either modified by non-equilibrium effects, or exhibits a wavy pattern, caused by an under-abundance of impactors which have been removed by radiation pressure.
TL;DR: In this article, an extended bow shock structure was found in an incomplete arc of 22' diameter, which is cospatial with the termination shock due to interaction with the interstellar medium (ISM) as defined by Sahai & Chronopoulos from ultraviolet GALEX images.
Abstract: Herschel PACS and SPIRE images have been obtained over a 30'x30' area around the well-known carbon star CW Leo (IRC +10 216). An extended structure is found in an incomplete arc of ~22' diameter, which is cospatial with the termination shock due to interaction with the interstellar medium (ISM) as defined by Sahai & Chronopoulos from ultraviolet GALEX images. Fluxes are derived in the 70, 160, 250, 350, and 550 um bands in the region where the interaction with the ISM takes place, and this can be fitted with a modified black body with a temperature of 25+-3 K. Using the published proper motion and radial velocity for the star, we derive a heliocentric space motion of 25.1 km/s. Using the PACS and SPIRE data and the analytical formula of the bow shock structure, we infer a de-projected standoff distance of the bow shock of R0 = (8.0+-0.3)x10^17 cm. We also derive a relative velocity of the star with respect to the ISM of (106.6+-8.7)/sqrt(n_ISM) km/s, where n_ISM is the number density of the local ISM.
Katholieke Universiteit Leuven1, University of Amsterdam2, University College London3, Rutherford Appleton Laboratory4, University of Lethbridge5, Spanish National Research Council6, Janssen Pharmaceutica7, University of California, Berkeley8, Max Planck Society9, Cardiff University10, Royal Observatory of Belgium11, UK Astronomy Technology Centre12, University of Vienna13, Stockholm University14
TL;DR: In this paper, the spectral fingerprints of more than 900 spectral lines of the red supergiant VY CMa were analyzed and 13 different molecules and their isotopologues were identified.
Abstract: With a luminosity >10 5 Land a mass-loss rate of ∼2 × 10 −4 Myr −1 , the red supergiant VY CMa truly is a spectacular object. Because of its extreme evolutionary state, it could explode as supernova any time. Studying its circumstellar material, into which the supernova blast will run, provides interesting constraints on supernova explosions and on the rich chemistry taking place in such complex circumstellar envelopes. We have obtained spectroscopy of VY CMa over the full wavelength range offered by the PACS and SPIRE instruments of Herschel, i.e. 55-672 micron. The observations show the spectral fingerprints of more than 900 spectral lines, of which more than half belong to water. In total, we have identified 13 different molecules and some of their isotopologues. A first analysis shows that water is abundantly present, with an ortho-to-para ratio as low as ∼1.3:1, and that chemical non-equilibrium processes determine the abundance fractions in the inner envelope.
TL;DR: In this article, the authors used PACS and SPIRE spectrometers on board Herschel to detect several tens of lines from SiS and SiO, including lines from the v=1 vibrational level.
Abstract: The interstellar medium is enriched primarily by matter ejected from evolved low and intermediate mass stars. The outflows from these stars create a circumstellar envelope in which a rich gas-phase and dust-nucleation chemistry takes place. We observed the nearest carbon-rich evolved star, IRC+10216, using the PACS (55-210 {\mu}m) and SPIRE (194-672 {\mu}m) spectrometers on board Herschel. We find several tens of lines from SiS and SiO, including lines from the v=1 vibrational level. For SiS these transitions range up to J=124-123, corresponding to energies around 6700K, while the highest detectable transition is J=90-89 for SiO, which corresponds to an energy around 8400K. Both species trace the dust formation zone of IRC+10216, and the broad energy ranges involved in their detected transitions permit us to derive the physical properties of the gas and the particular zone in which each species has been formed. This allows us to check the accuracy of chemical thermodynamical equilibrium models and the suggested depletion of SiS and SiO due to accretion onto dust grains.
Katholieke Universiteit Leuven1, University of Amsterdam2, Spanish National Research Council3, University College London4, Rutherford Appleton Laboratory5, University of Lethbridge6, Janssen Pharmaceutica7, University of California, Berkeley8, Max Planck Society9, Cardiff University10, Royal Observatory of Belgium11, UK Astronomy Technology Centre12, University of Vienna13, Stockholm University14
TL;DR: In this paper, the authors used PACS and SPIRE spectrometers on board Herschel to detect several tens of lines from SiS and SiO, including lines from the v = 1 vibrational level.
Abstract: The interstellar medium is enriched primarily by matter ejected from evolved low and intermediate mass stars. The outflows from these stars create a circumstellar envelope in which a rich gas-phase and dust-nucleation chemistry takes place. We observed the nearest carbon-rich evolved star, IRC +10216, using the PACS (55–210 μm) and SPIRE (194–672 μm) spectrometers on board Herschel. We find several tens of lines from SiS and SiO, including lines from the v = 1 vibrational level. For SiS these transitions range up to J = 124–123, corresponding to energies around 6700 K, while the highest detectable transition is J = 90–89 for SiO, which corresponds to an energy around 8400 K. Both species trace the dust formation zone of IRC +10216, and the broad energy ranges involved in their detected transitions permit us to derive the physical properties of the gas and the particular zone in which each species has been formed. This allows us to check the accuracy of chemical thermodynamical equilibrium models and the suggested depletion of SiS and SiO due to accretion onto dust grains.
Posted Content•
14 May 2010
TL;DR: In this article, the first results from the Gould Belt survey, obtained toward the Aquila Rift and Polaris Flare regions during the'science demonstration phase' of Herschel, were summarized.
Abstract: We summarize the first results from the Gould Belt survey, obtained toward the Aquila Rift and Polaris Flare regions during the 'science demonstration phase' of Herschel. Our 70-500 micron images taken in parallel mode with the SPIRE and PACS cameras reveal a wealth of filamentary structure, as well as numerous dense cores embedded in the filaments. Between ~ 350 and 500 prestellar cores and ~ 45-60 Class 0 protostars can be identified in the Aquila field, while ~ unbound starless cores and no protostars are observed in the Polaris field. The prestellar core mass function (CMF) derived for the Aquila region bears a strong resemblance to the stellar initial mass function (IMF), already confirming the close connection between the CMF and the IMF with much better statistics than earlier studies. Comparing and contrasting our Herschel results in Aquila and Polaris, we propose an observationally-driven scenario for core formation according to which complex networks of long, thin filaments form first within molecular clouds, and then the densest filaments fragment into a number of prestellar cores via gravitational instability.
Katholieke Universiteit Leuven1, University of Amsterdam2, University College London3, Rutherford Appleton Laboratory4, University of Lethbridge5, Janssen Pharmaceutica6, Spanish National Research Council7, University of California, Berkeley8, Max Planck Society9, Cardiff University10, Royal Observatory of Belgium11, UK Astronomy Technology Centre12, University of Vienna13, Stockholm University14
TL;DR: In this paper, the spectral fingerprints of more than 900 spectral lines of the red supergiant VY CMa were analyzed and 13 different molecules and some of their isotopologues were identified.
Abstract: With a luminosity > 10^5 Lsun and a mass-loss rate of about 2.10-4 Msun/yr, the red supergiant VY CMa truly is a spectacular object. Because of its extreme evolutionary state, it could explode as supernova any time. Studying its circumstellar material, into which the supernova blast will run, provides interesting constraints on supernova explosions and on the rich chemistry taking place in such complex circumstellar envelopes. We have obtained spectroscopy of VYCMa over the full wavelength range offered by the PACS and SPIRE instruments of Herschel, i.e. 55 to 672 micron. The observations show the spectral fingerprints of more than 900 spectral lines, of which more than half belong to water. In total, we have identified 13 different molecules and some of their isotopologues. A first analysis shows that water is abundantly present, with an ortho-to-para ratio as low as 1.3:1, and that chemical non-equilibrium processes determine the abundance fractions in the inner envelope.
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TL;DR: In this paper, the authors presented the detection of the 69 −mu −m band of the crystalline olivine forsterite within the MESS key program of Herschel.
Abstract: In this article we present the detection of the 69 {\mu}m band of the crystalline olivine forsterite within the MESS key program of Herschel. We determine the temperature of the forsterite grains by fitting the 69 {\mu}m band.