The FIRST Mission

Pilbratt, G.

doi:10.1007/3-540-45553-1_51

Cited by 11 publications

(8 citation statements)

References 3 publications

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“…This conclusion is strengthened by ground-based observations of the H 18 2 O isotope (van der Tak et al 2006). Despite previous observations of the region, the future launch of ESA's Herschel Space Observatory (Pilbratt 2005), with on board the HIFI will provide key information on the physical and chemical conditions in molecular clouds by means of observing many water lines with higher sensitivity. Moreover, its high angular resolution allows to separate regions.…”

Section: The High-mass Star-forming Region Afgl 2591mentioning

confidence: 98%

Modeling the water line emission from the high-mass star-forming region AFGL 2591

Poelman

Tak

2007

A&A

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Context. Observations of water lines are a sensitive probe of the geometry, dynamics and chemical structure of dense molecular gas. The launch of Herschel with on board HIFI and PACS allows to probe the behaviour of multiple water lines with unprecedented sensitivity and resolution. Aims. We investigate the diagnostic value of specific water transitions in high-mass star-forming regions. As a test case, we apply our models to the AFGL 2591 region. Methods. A multi-zone escape probability method is used in two dimensions to calculate the radiative transfer. Similarities and differences of constant and jump abundance models are displayed, as well as when an outflow is incorporated. Results. In general, for models with a constant water abundance, the ground state lines, i.e., 1 10 -1 01 , 1 11 -0 00 , and 2 12 -1 01 , are predicted in absorption, all the others in emission. This behaviour changes for models with a water abundance jump profile in that the line profiles for jumps by a factor of ∼10-100 are similar to the line shapes in the constant abundance models, whereas larger jumps lead to emission profiles. Asymmetric line profiles are found for models with a cavity outflow and depend on the inclination angle. Models with an outflow cavity are favoured to reproduce the SWAS observations of the 1 10 -1 01 ground-state transition. PACS spectra will tell us about the geometry of these regions, both through the continuum and through the lines. Conclusions. It is found that the low-lying transitions of water are sensitive to outflow features, and represent the excitation conditions in the outer regions. High-lying transitions are more sensitive to the adopted density and temperature distribution which probe the inner excitation conditions. The Herschel mission will thus be very helpful to constrain the physical and chemical structure of high-mass star-forming regions such as AFGL 2591.

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Section: The High-mass Star-forming Region Afgl 2591mentioning

confidence: 98%

Modeling the water line emission from the high-mass star-forming region AFGL 2591

Poelman

Tak

2007

A&A

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“…Radiation at these wavelengths where interstellar dust is transparent enables observations of star formation deeply embedded in molecular clouds. The Herschel Space Observatory (formerly known as FIRST) [1], [2]-a European Space Agency (ESA) cornerstone mission scheduled for launch in 2007, covers approximately the 60-700-m (5 THz-430 GHz) range. The Spectral and Photometric Imaging REceiver (SPIRE) [3], [4] is one of the three cryogenic focal plane instruments on board the Herschel Space Observatory.…”

Section: Introductionmentioning

confidence: 99%

Feed horn coupled bolometer arrays for spire-design, simulations, and measurements

Chattopadhyay

Glenn

Bock

et al. 2003

IEEE Trans. Microwave Theory Techn.

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In this paper, we present the design, modeling, and measurements of feed horn coupled large bolometer arrays being developed for the Herschel Space Observatory's Spectral and Photometric Imaging REceiver (SPIRE) instrument. SPIRE has five arrays of feed horn coupled silicon-nitride micromesh "spider-web" bolometers in two instruments, a three-band photometer, and a two-band Fourier transform spectrometer, each covering the 430-GHz-1.5-THz band. The optical coupling efficiency, bandwidth, and crosstalk between adjacent pixels of the arrays were investigated with numerical electromagnetic-field simulators, and prototype arrays were measured extensively in a test facility. The measured results were found to be in good agreement with simulation predictions, and the simulation results were used as a benchmark for the design goals of the instrument.

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“…The Odin satellite, launched in 2001 (Nordh et al 2003), observed with its 1-m antenna the same line in a dozen comets at high spectral resolution and also Figures 1,2,4,7,9 and Table 3 are only available in electronic form at http://www.aanda.org detected the 1 10 −1 01 line at 547.7 GHz of the H 18 2 O isotopologue in a few comets (Lecacheux et al 2003;Biver et al 2007). The Herschel Space Observatory, equipped with a 3.5-m diameter cooled telescope, will cover the 60−600 µm range which contains many rotational lines of water (Pilbratt 2005). The observation of H 2 O, HDO and H 18 2 O in cometary atmospheres is among the highest priorities of Solar System studies with Herschel (Crovisier et al 2005).…”

Section: Introductionmentioning

confidence: 99%

Radiative transfer simulation of water rotational excitation in comets

Захаров¹,

Bockelée‐Morvan²,

Biver³

et al. 2007

A&A

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Context. The recent advent of space-based detectors at far-infrared and submillimetre wavelengths opened up the possibility of observing cometary water from its rotational transitions. The 1 10 −1 01 fundamental line of ortho H 2 O at 557 GHz was detected in several comets by the Submillimeter Wave Astronomical Satellite and Odin. This line as well as other water and H 18 2 O lines will be observed by the three instruments of the ESA Herschel Space Observatory. In order to prepare or interpret these observations, excitation models including H 2 O self-absorption are required. Aims. For treating radiation transfer of water in comets, Bockelée-Morvan (1987, A&A, 181, 169) used the local approximation with the escape probability method (EP). Bensch & Bergin (2004, ApJ, 615, 531) used the Monte-Carlo method (MC), which is more exact from a physical point of view, but is much more CPU time-demanding. The aim of this study is to compare the results of the two methods and to investigate the extent to which the EP method provides acceptable results for synthesizing line profiles and analysing observations. Methods. We developed two 1D numerical codes. The MC code is based on the accelerated Monte Carlo algorithm proposed by Hogerheijde & van der Tak (2000, A&A, 362, 697). The EP code is based on the algorithm proposed by Bockelée-Morvan (1987). They include the seven lowest rotational levels of ortho-water, which are the primarily populated levels in the rotationally cold coma. A spherically symmetric density distribution with constant expansion velocity is assumed. Collisions with water and electrons, and infrared pumping, are taken into account. Synthetic line profiles pertaining to Odin and future Herschel observations with the Heterodyne Instrument for Far-Infrared are computed for water production rates ranging from 10 28 to 10 30 s −1 . Results. We show that the EP method has sufficient accuracy to predict rotational excitation, line intensities and line shapes. Differences in level populations do not exceed 20%, except in the narrow region where a strong gradient in electron temperature and density is present. Line shapes are in excellent agreement and line areas differ by less than 7%.

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The FIRST Mission

Cited by 11 publications

References 3 publications

Modeling the water line emission from the high-mass star-forming region AFGL 2591

Modeling the water line emission from the high-mass star-forming region AFGL 2591

Feed horn coupled bolometer arrays for spire-design, simulations, and measurements

Radiative transfer simulation of water rotational excitation in comets

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