Thijs de Graauw - Academia.edu (original) (raw)
Papers by Thijs de Graauw
Astronomy & Astrophysics, 2000
First detections of thermal water vapor absorption lines have been made toward Orion IRc2 using t... more First detections of thermal water vapor absorption lines have been made toward Orion IRc2 using the Short Wavelength Spectrometer (SWS) on board the Infrared Space Observatory (ISO). Grating spectra covering wavelengths 25-45 mu m yield 19 pure rotational lines, originating from energy levels 200-750 K above ground. Fabry-Perot spectra of 5 transitions resolve the line profiles and reveal the H2O
![Research paper thumbnail of Crystalline silicates in planetray nebulae with [WC] central stars](https://attachments.academia-assets.com/66811640/thumbnails/1.jpg)
](Ant Algorithms, 1998
We present ISO-SWS spectroscopy of the cool dusty envelopes surrounding two Planetary Nebulae wit... more We present ISO-SWS spectroscopy of the cool dusty envelopes surrounding two Planetary Nebulae with [WC] central stars, BD+30~3639 and He~2-113. The lambda < 15micron region is dominated by a rising continuum with prominent emission from C-rich dust (PAHs), while the long wavelength part shows narrow solid state features from crystalline silicates. This demonstrates that the chemical composition of both stars
ICMWFST'96. 1996 4th International Conference on Millimeter Wave and Far Infrared Science and Technology. Proceedings, 1996
There are great interests in developing Nb SIS mixers because of the extremely low noise temperat... more There are great interests in developing Nb SIS mixers because of the extremely low noise temperatures and because of the need of low local oscillator (LO) power. Several groups have demonstrated experimentally that Nb SIS mixers with integrated tuning elements can perform near the quantum noise limit up to the Nb gap frequency (~700 GHz). Beyond this frequency, a major loss will take place in the tuning elements, which are Nb-SiO2-Nb micro-striplines, because the incoming photons can break the Cooper-pairs, thus increasing the surface resistance of the Nb strips. Applying highly conductive Al instead of Nb for a stripline can reduce the loss since the former has a lower surface resistance at higher frequencies. In this work, we report the fabrication of waveguide Nb SIS mixers with Al striplines and heterodyne measurement results around 1 THz
Planetary and Space Science, 2009
This Guaranteed Time Key Programme, approved by the European Space Agency, aims at determining th... more This Guaranteed Time Key Programme, approved by the European Space Agency, aims at determining the distribution, the evolution and the origin of water in Mars, the Outer Planets, Titan, Enceladus and Comets, using the three Herschel instruments HIFI, PACS and SPIRE. It addresses the broad topic of water and its isotopologues in planetary and cometary atmospheres. The nature of cometary activity and the thermodynamics of cometary comae will be investigated by studying water excitation in a sample of comets. The D/H ratio, the key parameter for constraining the origin and evolution of Solar System species, will be measured for the first time in a Jupiter-family comet. A comparison with existing and new measurements of D/H in Oort-cloud comets will constrain the composition of pre-solar cometary grains and possibly the dynamics of the protosolar nebula. New measurements of D/H in Giant Planets, similarly constraining the composition of proto-planetary ices, will be obtained. The D/H and other isotopic ratios, diagnostic of Mars' atmosphere evolution, will be accurately measured in H 2 O and CO. The role of water vapour in Mars' atmospheric chemistry will be studied by monitoring vertical profiles of H 2 O and HDO and by searching for several other species (and CO and H 2 O isotopes). A detailed study of the source of water in the upper atmosphere of the Giant Planets and Titan will be performed. By monitoring the water abundance, vertical profile, and input fluxes in the various objects, and when possible with the help of mapping observations, we will discriminate between the possible sources of water in the Outer Planets (interplanetary dust particles, cometary impacts, and local sources). In addition to these inter-connected objectives, serendipitous searches may further enhance our knowledge of the composition of planetary and cometary atmospheres. For further details see:
COSPAR Colloquia Series, 2002
The Astrophysical Journal, 1999
Spectra of interstellar CO 2 ice absorption features at a resolving power of λ/Δλ approx 1500-200... more Spectra of interstellar CO 2 ice absorption features at a resolving power of λ/Δλ approx 1500-2000 are presented for 14 lines of sight. The observations were made with the Short-Wavelength Spectrometer (SWS) of the Infrared Space Observatory (ISO). Spectral ...
Publications of the Astronomical Society of the Pacific, 2011
Water In Star-forming regions with Herschel' (WISH) is a key program on the Herschel Space Observ... more Water In Star-forming regions with Herschel' (WISH) is a key program on the Herschel Space Observatory designed to probe the physical and chemical structure of young stellar objects using water and related molecules and to follow the water abundance from collapsing clouds to planet-forming disks. About 80
Planetary and Space Science, 2000
The spectrum of Mars at 2.4–45μm has been observed on July 31, 1997 (Ls=157°) by the short-wavele... more The spectrum of Mars at 2.4–45μm has been observed on July 31, 1997 (Ls=157°) by the short-wavelength spectrometer of the Infrared Space Observatory. The data consist of a high signal to noise, complete grating spectrum (resolving power R∼1500–2500) and portions of the 20–40μm spectrum observed in Fabry–Perot mode (R∼31000). The data show the infrared bands of known martian atmospheric species
International Journal of Infrared and Millimeter Waves, 1981
International Journal of Infrared and Millimeter Waves, 1982
Icarus, 2000
A series of far infrared (FIR) spectra of Mars between 43 and 196 µm was taken with the Long Wave... more A series of far infrared (FIR) spectra of Mars between 43 and 196 µm was taken with the Long Wavelength Spectrometer (LWS) on board the European Space Agency's Infrared Space Observatory (ISO). Analysis of these medium-resolution data reveals a rotational modulation of the disk-averaged FIR brightness temperature. The observed variability of ±1.5% in the LWS wavelength range compares favorably with the predictions of a thermophysical model of the martian surface. A surface emissivity of ∼0.90 gives good agreement between the measured and the modeled brightness temperatures and leads to an improved estimate of the LWS photometric calibration uncertainty.
Astronomy and Astrophysics, 2010
Aims. Previous studies by the satellites SWAS and Odin provided stringent upper limits on the gas... more Aims. Previous studies by the satellites SWAS and Odin provided stringent upper limits on the gas phase water abundance of dark clouds (x(H 2 O) <7×10 −9 ). We investigate the chemistry of water vapor in starless cores beyond the previous upper limits using the highly improved angular resolution and sensitivity of Herschel and measure the abundance of water vapor during evolutionary stages just preceding star formation. Methods. High spectral resolution observations of the fundamental ortho water (o-H 2 O) transition (557 GHz) were carried out with the Heterodyne Instrument for the Far Infrared onboard Herschel toward two starless cores: Barnard 68 (hereafter B68), a Bok globule, and LDN 1544 (L1544), a prestellar core embedded in the Taurus molecular cloud complex. Detailed radiative transfer and chemical codes were used to analyze the data. Results. The rms in the brightness temperature measured for the B68 and L1544 spectra is 2.0 and 2.2 mK, respectively, in a velocity bin of 0.59 km s −1 . The continuum level is 3.5±0.2 mK in B68 and 11.4±0.4 mK in L1544. No significant feature is detected in B68 and the 3 σ upper limit is consistent with a column density of o-H 2 O N(o-H 2 O) < 2.5×10 13 cm −2 , or a fractional abundance x(o-H 2 O) < 1.3×10 −9 , more than an order of magnitude lower than the SWAS upper limit on this source. The L1544 spectrum shows an absorption feature at a 5 σ level from which we obtain the first value of the o-H 2 O column density ever measured in dark clouds: N(o-H 2 O) = (8±4)×10 12 cm −2 . The corresponding fractional abundance is x(o-H 2 O) 5×10 −9 at radii > 7000 AU and 2×10 −10 toward the center. The radiative transfer analysis shows that this is consistent with a x(o-H 2 O) profile peaking at 10 −8 , 0.1 pc away from the core center, where both freeze-out and photodissociation are negligible.
Astronomy and Astrophysics, 2010
We performed a sensitive search for the ground-state emission lines of ortho-and para-water vapor... more We performed a sensitive search for the ground-state emission lines of ortho-and para-water vapor in the DM Tau protoplanetary disk using the Herschel/HIFI instrument. No strong lines are detected down to 3σ levels in 0.5 km s −1 channels of 4.2 mK for the 1 10 -1 01 line and 12.6 mK for the 1 11 -0 00 line. We report a very tentative detection, however, of the 1 10 -1 01 line in the Wide Band Spectrometer, with a strength of T mb = 2.7 mK, a width of 5.6 km s −1 and an integrated intensity of 16.0 mK km s −1 . The latter constitutes a 6σ detection. Regardless of the reality of this tentative detection, model calculations indicate that our sensitive limits on the line strengths preclude efficient desorption of water in the UV illuminated regions of the disk. We hypothesize that more than 95-99% of the water ice is locked up in coagulated grains that have settled to the midplane.
Astronomy and Astrophysics, 2010
Astronomy and Astrophysics, 2010
Context. Water is a key molecule in the star formation process, but its spatial distribution in s... more Context. Water is a key molecule in the star formation process, but its spatial distribution in star-forming regions is not well known. Aims. We study the distribution of dust continuum and H 2 O and 13 CO line emission in DR21, a luminous star-forming region with a powerful outflow and a compact H ii region. Methods. Herschel-HIFI spectra near 1100 GHz show narrow 13 CO 10−9 emission and H 2 O 1 11 − 0 00 absorption from the dense core and broad emission from the outflow in both lines. The H 2 O line also shows absorption by a foreground cloud known from ground-based observations of low-J CO lines. Results. The dust continuum emission is extended over 36 ′′ FWHM, while the 13 CO and H 2 O lines are confined to ≈24 ′′ or less. The foreground absorption appears to peak further North than the other components. Radiative transfer models indicate very low abundances of ∼2×10 −10 for H 2 O and ∼8×10 −7 for 13 CO in the dense core, and higher H 2 O abundances of ∼4×10 −9 in the foreground cloud and ∼7×10 −7 in the outflow. Conclusions. The high H 2 O abundance in the warm outflow is probably due to the evaporation of water-rich icy grain mantles, while the H 2 O abundance is kept down by freeze-out in the dense core and by photodissociation in the foreground cloud.
Astronomy and Astrophysics, 2010
HERSCHEL-HIFI observations of water from the intermediate mass protostar NGC7129 FIRS 2 provide a... more HERSCHEL-HIFI observations of water from the intermediate mass protostar NGC7129 FIRS 2 provide a powerful diagnostic of the physical conditions in this star formation environment. Six spectral settings, covering four H 2 16 O and two H 2 18 O lines, were observed and all but one H 2 18 O line were detected. The four H 2 16 O lines discussed here share a similar morphology: a narrower, ≈ 6 km s −1 , component centered slightly redward of the systemic velocity of NGC7129 FIRS 2 and a much broader, ≈ 25 km s −1 component centered blueward and likely associated with powerful outflows. The narrower components are consistent with emission from water arising in the envelope around the intermediate mass protostar, and the abundance of H 2 O is constrained to ≈10 −7 for the outer envelope. Additionally, the presence of a narrow self-absorption component for the lowest energy lines is likely due to self-absorption from colder water in the outer envelope. The broader component, where the H 2 O/CO relative abundance is found to be ≈ 0.2, appears to be tracing the same energetic region that produces strong CO emission at high J.
Astronomy and Astrophysics, 2010
Astronomy and Astrophysics, 2010
Aims. 'Water in Star-forming regions with Herschel' (WISH) is a Herschel Key Programme aimed at u... more Aims. 'Water in Star-forming regions with Herschel' (WISH) is a Herschel Key Programme aimed at understanding the physical and chemical structure of young stellar objects (YSOs) with a focus on water and related species. Methods. The low-mass protostar HH 46 was observed with the Photodetector Array Camera and Spectrometer (PACS) on the Herschel Space Observatory to measure emission in H 2 O, CO, OH, [O i], and [C ii] lines located between 63 and 186 µm. The excitation and spatial distribution of emission can disentangle the different heating mechanisms of YSOs, with better spatial resolution and sensitivity than previously possible. Results. Far-IR line emission is detected at the position of the protostar and along the outflow axis. The OH emission is concentrated at the central position, CO emission is bright at the central position and along the outflow, and H 2 O emission is concentrated in the outflow. In addition, [O i] emission is seen in low-velocity gas, assumed to be related to the envelope, and is also seen shifted up to 170 km s −1 in both the red-and blue-shifted jets. Envelope models are constructed based on previous observational constraints. They indicate that passive heating of a spherical envelope by the protostellar luminosity cannot explain the high-excitation molecular gas detected with PACS, including CO lines with upper levels at >2500 K above the ground state. Instead, warm CO and H 2 O emission is probably produced in the walls of an outflow-carved cavity in the envelope, which are heated by UV photons and non-dissociative C-type shocks. The bright OH and [O i] emission is attributed to J-type shocks in dense gas close to the protostar. In the scenario described here, the combined cooling by far-IR lines within the central spatial pixel is estimated to be 2×10 −2 L ⊙ , with 60-80% attributed to J-and C-type shocks produced by interactions between the jet and the envelope.
Astronomy and Astrophysics, 2010
A HIFI preview of warm molecular gas around χ Cygni: first detection of H2O emission toward an S-... more A HIFI preview of warm molecular gas around χ Cygni: first detection of H2O emission toward an S-type AGB star Justtanont, K.; Decin, L.; Schöier, F.L.; Maercker, M.; Olofsson, H.; Bujarrabal, V.; Marston, A.P.; Teyssier, D.; Alcolea, J.; Cernicharo, J.; Dominik, C.; de Koter, A.; Melnick, G.; Menten, K.; Neufeld, D.; Planesas, P.; Schmidt, M.; Szczerba, R.; Waters, L.B.F.M.; de Graauw, T.; Whyborn, N.; Finn, T.; Helmich, F.; Siebertz, O.; Schmülling, F.; Ossenkopf, V.; Lai, R.
Astronomy & Astrophysics, 2000
First detections of thermal water vapor absorption lines have been made toward Orion IRc2 using t... more First detections of thermal water vapor absorption lines have been made toward Orion IRc2 using the Short Wavelength Spectrometer (SWS) on board the Infrared Space Observatory (ISO). Grating spectra covering wavelengths 25-45 mu m yield 19 pure rotational lines, originating from energy levels 200-750 K above ground. Fabry-Perot spectra of 5 transitions resolve the line profiles and reveal the H2O
Ant Algorithms, 1998
We present ISO-SWS spectroscopy of the cool dusty envelopes surrounding two Planetary Nebulae wit... more We present ISO-SWS spectroscopy of the cool dusty envelopes surrounding two Planetary Nebulae with [WC] central stars, BD+30~3639 and He~2-113. The lambda < 15micron region is dominated by a rising continuum with prominent emission from C-rich dust (PAHs), while the long wavelength part shows narrow solid state features from crystalline silicates. This demonstrates that the chemical composition of both stars
ICMWFST'96. 1996 4th International Conference on Millimeter Wave and Far Infrared Science and Technology. Proceedings, 1996
There are great interests in developing Nb SIS mixers because of the extremely low noise temperat... more There are great interests in developing Nb SIS mixers because of the extremely low noise temperatures and because of the need of low local oscillator (LO) power. Several groups have demonstrated experimentally that Nb SIS mixers with integrated tuning elements can perform near the quantum noise limit up to the Nb gap frequency (~700 GHz). Beyond this frequency, a major loss will take place in the tuning elements, which are Nb-SiO2-Nb micro-striplines, because the incoming photons can break the Cooper-pairs, thus increasing the surface resistance of the Nb strips. Applying highly conductive Al instead of Nb for a stripline can reduce the loss since the former has a lower surface resistance at higher frequencies. In this work, we report the fabrication of waveguide Nb SIS mixers with Al striplines and heterodyne measurement results around 1 THz
Planetary and Space Science, 2009
This Guaranteed Time Key Programme, approved by the European Space Agency, aims at determining th... more This Guaranteed Time Key Programme, approved by the European Space Agency, aims at determining the distribution, the evolution and the origin of water in Mars, the Outer Planets, Titan, Enceladus and Comets, using the three Herschel instruments HIFI, PACS and SPIRE. It addresses the broad topic of water and its isotopologues in planetary and cometary atmospheres. The nature of cometary activity and the thermodynamics of cometary comae will be investigated by studying water excitation in a sample of comets. The D/H ratio, the key parameter for constraining the origin and evolution of Solar System species, will be measured for the first time in a Jupiter-family comet. A comparison with existing and new measurements of D/H in Oort-cloud comets will constrain the composition of pre-solar cometary grains and possibly the dynamics of the protosolar nebula. New measurements of D/H in Giant Planets, similarly constraining the composition of proto-planetary ices, will be obtained. The D/H and other isotopic ratios, diagnostic of Mars' atmosphere evolution, will be accurately measured in H 2 O and CO. The role of water vapour in Mars' atmospheric chemistry will be studied by monitoring vertical profiles of H 2 O and HDO and by searching for several other species (and CO and H 2 O isotopes). A detailed study of the source of water in the upper atmosphere of the Giant Planets and Titan will be performed. By monitoring the water abundance, vertical profile, and input fluxes in the various objects, and when possible with the help of mapping observations, we will discriminate between the possible sources of water in the Outer Planets (interplanetary dust particles, cometary impacts, and local sources). In addition to these inter-connected objectives, serendipitous searches may further enhance our knowledge of the composition of planetary and cometary atmospheres. For further details see:
COSPAR Colloquia Series, 2002
The Astrophysical Journal, 1999
Spectra of interstellar CO 2 ice absorption features at a resolving power of λ/Δλ approx 1500-200... more Spectra of interstellar CO 2 ice absorption features at a resolving power of λ/Δλ approx 1500-2000 are presented for 14 lines of sight. The observations were made with the Short-Wavelength Spectrometer (SWS) of the Infrared Space Observatory (ISO). Spectral ...
Publications of the Astronomical Society of the Pacific, 2011
Water In Star-forming regions with Herschel' (WISH) is a key program on the Herschel Space Observ... more Water In Star-forming regions with Herschel' (WISH) is a key program on the Herschel Space Observatory designed to probe the physical and chemical structure of young stellar objects using water and related molecules and to follow the water abundance from collapsing clouds to planet-forming disks. About 80
Planetary and Space Science, 2000
The spectrum of Mars at 2.4–45μm has been observed on July 31, 1997 (Ls=157°) by the short-wavele... more The spectrum of Mars at 2.4–45μm has been observed on July 31, 1997 (Ls=157°) by the short-wavelength spectrometer of the Infrared Space Observatory. The data consist of a high signal to noise, complete grating spectrum (resolving power R∼1500–2500) and portions of the 20–40μm spectrum observed in Fabry–Perot mode (R∼31000). The data show the infrared bands of known martian atmospheric species
International Journal of Infrared and Millimeter Waves, 1981
International Journal of Infrared and Millimeter Waves, 1982
Icarus, 2000
A series of far infrared (FIR) spectra of Mars between 43 and 196 µm was taken with the Long Wave... more A series of far infrared (FIR) spectra of Mars between 43 and 196 µm was taken with the Long Wavelength Spectrometer (LWS) on board the European Space Agency's Infrared Space Observatory (ISO). Analysis of these medium-resolution data reveals a rotational modulation of the disk-averaged FIR brightness temperature. The observed variability of ±1.5% in the LWS wavelength range compares favorably with the predictions of a thermophysical model of the martian surface. A surface emissivity of ∼0.90 gives good agreement between the measured and the modeled brightness temperatures and leads to an improved estimate of the LWS photometric calibration uncertainty.
Astronomy and Astrophysics, 2010
Aims. Previous studies by the satellites SWAS and Odin provided stringent upper limits on the gas... more Aims. Previous studies by the satellites SWAS and Odin provided stringent upper limits on the gas phase water abundance of dark clouds (x(H 2 O) <7×10 −9 ). We investigate the chemistry of water vapor in starless cores beyond the previous upper limits using the highly improved angular resolution and sensitivity of Herschel and measure the abundance of water vapor during evolutionary stages just preceding star formation. Methods. High spectral resolution observations of the fundamental ortho water (o-H 2 O) transition (557 GHz) were carried out with the Heterodyne Instrument for the Far Infrared onboard Herschel toward two starless cores: Barnard 68 (hereafter B68), a Bok globule, and LDN 1544 (L1544), a prestellar core embedded in the Taurus molecular cloud complex. Detailed radiative transfer and chemical codes were used to analyze the data. Results. The rms in the brightness temperature measured for the B68 and L1544 spectra is 2.0 and 2.2 mK, respectively, in a velocity bin of 0.59 km s −1 . The continuum level is 3.5±0.2 mK in B68 and 11.4±0.4 mK in L1544. No significant feature is detected in B68 and the 3 σ upper limit is consistent with a column density of o-H 2 O N(o-H 2 O) < 2.5×10 13 cm −2 , or a fractional abundance x(o-H 2 O) < 1.3×10 −9 , more than an order of magnitude lower than the SWAS upper limit on this source. The L1544 spectrum shows an absorption feature at a 5 σ level from which we obtain the first value of the o-H 2 O column density ever measured in dark clouds: N(o-H 2 O) = (8±4)×10 12 cm −2 . The corresponding fractional abundance is x(o-H 2 O) 5×10 −9 at radii > 7000 AU and 2×10 −10 toward the center. The radiative transfer analysis shows that this is consistent with a x(o-H 2 O) profile peaking at 10 −8 , 0.1 pc away from the core center, where both freeze-out and photodissociation are negligible.
Astronomy and Astrophysics, 2010
We performed a sensitive search for the ground-state emission lines of ortho-and para-water vapor... more We performed a sensitive search for the ground-state emission lines of ortho-and para-water vapor in the DM Tau protoplanetary disk using the Herschel/HIFI instrument. No strong lines are detected down to 3σ levels in 0.5 km s −1 channels of 4.2 mK for the 1 10 -1 01 line and 12.6 mK for the 1 11 -0 00 line. We report a very tentative detection, however, of the 1 10 -1 01 line in the Wide Band Spectrometer, with a strength of T mb = 2.7 mK, a width of 5.6 km s −1 and an integrated intensity of 16.0 mK km s −1 . The latter constitutes a 6σ detection. Regardless of the reality of this tentative detection, model calculations indicate that our sensitive limits on the line strengths preclude efficient desorption of water in the UV illuminated regions of the disk. We hypothesize that more than 95-99% of the water ice is locked up in coagulated grains that have settled to the midplane.
Astronomy and Astrophysics, 2010
Astronomy and Astrophysics, 2010
Context. Water is a key molecule in the star formation process, but its spatial distribution in s... more Context. Water is a key molecule in the star formation process, but its spatial distribution in star-forming regions is not well known. Aims. We study the distribution of dust continuum and H 2 O and 13 CO line emission in DR21, a luminous star-forming region with a powerful outflow and a compact H ii region. Methods. Herschel-HIFI spectra near 1100 GHz show narrow 13 CO 10−9 emission and H 2 O 1 11 − 0 00 absorption from the dense core and broad emission from the outflow in both lines. The H 2 O line also shows absorption by a foreground cloud known from ground-based observations of low-J CO lines. Results. The dust continuum emission is extended over 36 ′′ FWHM, while the 13 CO and H 2 O lines are confined to ≈24 ′′ or less. The foreground absorption appears to peak further North than the other components. Radiative transfer models indicate very low abundances of ∼2×10 −10 for H 2 O and ∼8×10 −7 for 13 CO in the dense core, and higher H 2 O abundances of ∼4×10 −9 in the foreground cloud and ∼7×10 −7 in the outflow. Conclusions. The high H 2 O abundance in the warm outflow is probably due to the evaporation of water-rich icy grain mantles, while the H 2 O abundance is kept down by freeze-out in the dense core and by photodissociation in the foreground cloud.
Astronomy and Astrophysics, 2010
HERSCHEL-HIFI observations of water from the intermediate mass protostar NGC7129 FIRS 2 provide a... more HERSCHEL-HIFI observations of water from the intermediate mass protostar NGC7129 FIRS 2 provide a powerful diagnostic of the physical conditions in this star formation environment. Six spectral settings, covering four H 2 16 O and two H 2 18 O lines, were observed and all but one H 2 18 O line were detected. The four H 2 16 O lines discussed here share a similar morphology: a narrower, ≈ 6 km s −1 , component centered slightly redward of the systemic velocity of NGC7129 FIRS 2 and a much broader, ≈ 25 km s −1 component centered blueward and likely associated with powerful outflows. The narrower components are consistent with emission from water arising in the envelope around the intermediate mass protostar, and the abundance of H 2 O is constrained to ≈10 −7 for the outer envelope. Additionally, the presence of a narrow self-absorption component for the lowest energy lines is likely due to self-absorption from colder water in the outer envelope. The broader component, where the H 2 O/CO relative abundance is found to be ≈ 0.2, appears to be tracing the same energetic region that produces strong CO emission at high J.
Astronomy and Astrophysics, 2010
Astronomy and Astrophysics, 2010
Aims. 'Water in Star-forming regions with Herschel' (WISH) is a Herschel Key Programme aimed at u... more Aims. 'Water in Star-forming regions with Herschel' (WISH) is a Herschel Key Programme aimed at understanding the physical and chemical structure of young stellar objects (YSOs) with a focus on water and related species. Methods. The low-mass protostar HH 46 was observed with the Photodetector Array Camera and Spectrometer (PACS) on the Herschel Space Observatory to measure emission in H 2 O, CO, OH, [O i], and [C ii] lines located between 63 and 186 µm. The excitation and spatial distribution of emission can disentangle the different heating mechanisms of YSOs, with better spatial resolution and sensitivity than previously possible. Results. Far-IR line emission is detected at the position of the protostar and along the outflow axis. The OH emission is concentrated at the central position, CO emission is bright at the central position and along the outflow, and H 2 O emission is concentrated in the outflow. In addition, [O i] emission is seen in low-velocity gas, assumed to be related to the envelope, and is also seen shifted up to 170 km s −1 in both the red-and blue-shifted jets. Envelope models are constructed based on previous observational constraints. They indicate that passive heating of a spherical envelope by the protostellar luminosity cannot explain the high-excitation molecular gas detected with PACS, including CO lines with upper levels at >2500 K above the ground state. Instead, warm CO and H 2 O emission is probably produced in the walls of an outflow-carved cavity in the envelope, which are heated by UV photons and non-dissociative C-type shocks. The bright OH and [O i] emission is attributed to J-type shocks in dense gas close to the protostar. In the scenario described here, the combined cooling by far-IR lines within the central spatial pixel is estimated to be 2×10 −2 L ⊙ , with 60-80% attributed to J-and C-type shocks produced by interactions between the jet and the envelope.
Astronomy and Astrophysics, 2010
A HIFI preview of warm molecular gas around χ Cygni: first detection of H2O emission toward an S-... more A HIFI preview of warm molecular gas around χ Cygni: first detection of H2O emission toward an S-type AGB star Justtanont, K.; Decin, L.; Schöier, F.L.; Maercker, M.; Olofsson, H.; Bujarrabal, V.; Marston, A.P.; Teyssier, D.; Alcolea, J.; Cernicharo, J.; Dominik, C.; de Koter, A.; Melnick, G.; Menten, K.; Neufeld, D.; Planesas, P.; Schmidt, M.; Szczerba, R.; Waters, L.B.F.M.; de Graauw, T.; Whyborn, N.; Finn, T.; Helmich, F.; Siebertz, O.; Schmülling, F.; Ossenkopf, V.; Lai, R.