A lownoise 665 GHz SIS quasi-particle waveguide receiver

Kooi, J.; Walker, Christopher K.; Leduc, H. G.; Schaffer, P. L.; Hunter, T. R.; Benford, Dominic J.; Phillips, T. G.

doi:10.1007/bf02096231

Cited by 24 publications

(10 citation statements)

References 18 publications

(20 reference statements)

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“…The 12CO J \ 6È5 data were obtained with the Caltech Submillimeter Observatory (CSO)12 using the sensitive 650 GHz receiver of Kooi et al (1994) in double-sideband mode. Two acousto-optical spectrometers with resolutions of 0.05 and 0.5 km s~1 were used as the back ends.…”

Section: Co Observationsmentioning

confidence: 99%

H₂and CO Emission from Disks around T Tauri and Herbig Ae Pre–Main‐Sequence Stars and from Debris Disks around Young Stars: Warm and Cold Circumstellar Gas

Thi

Dishoeck

Blake

et al. 2001

ApJ

187

197

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We present ISO Short-Wavelength Spectrometer observations of pure-rotational line emission H 2 from the disks around low-and intermediate-mass preÈmain-sequence stars as well as from young stars thought to be surrounded by debris disks. The preÈmain-sequence sources have been selected to be isolated from molecular clouds and to have circumstellar disks revealed by millimeter interferometry. We detect "" warm ÏÏ (T B 100È200 K) gas around many sources, including tentatively the debris-disk H 2 objects. The mass of this warm gas ranges from D10~4 up to 8 ] 10~3 and can constitute a M _ M _ nonnegligible fraction of the total disk mass. Complementary single-dish 12CO 3È2, 13CO 3È2, and 12CO 6È5 observations have been obtained as well. These transitions probe cooler gas at T B 20È80 K. Most objects show a double-peaked CO emission proÐle characteristic of a disk in Keplerian rotation, consistent with interferometer data on the lower J lines. The ratios of the 12CO 3È2/13CO 3È2 integrated Ñuxes indicate that 12CO 3È2 is optically thick but that 13CO 3È2 is optically thin or at most moderately thick. The 13CO 3È2 lines have been used to estimate the cold gas mass. If a conversion H 2 /CO factor of 1 ] 104 is adopted, the derived cold gas masses are factors of 10È200 lower than those deduced from 1.3 millimeter dust emission assuming a gas/dust ratio of 100, in accordance with previous studies. These Ðndings conÐrm that CO is not a good tracer of the total gas content in disks since it can be photodissociated in the outer layers and frozen onto grains in the cold dense part of disks, but that it is a robust tracer of the disk velocity Ðeld. In contrast, can shield itself from photodissociation even in H 2 low-mass "" optically thin ÏÏ debris disks and can therefore survive longer. The warm gas is typically 1%È10% of the total mass deduced from millimeter continuum emission, but it can increase up to 100% or more for the debris-disk objects. Thus, residual molecular gas may persist into the debris-disk phase. No signiÐcant evolution in the CO, or dust masses is found for stars with ages in the range of H 2 , 106È107 yr, although a decrease is found for the older debris-disk star b Pictoris. The large amount of warm gas derived from raises the question of the heating mechanism(s). Radiation from the central H 2 star as well as the general interstellar radiation Ðeld heat an extended surface layer of the disk, but existing models fail to explain the amount of warm gas quantitatively. The existence of a gap in the disk can increase the area of material inÑuenced by radiation. Prospects for future observations with ground-and space-borne observations are discussed. Subject headings : circumstellar matter È infrared : stars È planetary systems : protoplanetary disks 1 Based in part on observations with ISO, an ESA project with instruments funded by ESA member states (especially the PI countries : France, Germany, Netherlands, and the United Kingdom) and with participation of ISAS and NASA.

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Section: Co Observationsmentioning

confidence: 99%

H₂and CO Emission from Disks around T Tauri and Herbig Ae Pre–Main‐Sequence Stars and from Debris Disks around Young Stars: Warm and Cold Circumstellar Gas

Thi

Dishoeck

Blake

et al. 2001

ApJ

187

197

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“…12 CO and 13 CO 6 -5 spectra toward TMR-1 (IRAS 04361ϩ2547) were obtained in a 11Љ (1500 AU) beam with the Caltech Submillimeter Observatory 2 in 1994 December using the SIS receiver of Kooi et al (1994). 12 CO 4 -3 spectra were obtained in a similar beam in the same period using the James Clark Maxwell Telescope 3 with the facility receiver C2.…”

Section: Tmr-1 As An Examplementioning

confidence: 99%

Photon Heating of Envelopes around Young Stellar Objects: An Explanation for CO [ITAL]J[/ITAL] = 6–5 Emission

Spaans

Hogerheijde

Mundy

et al. 1995

The Astrophysical Journal

131

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We propose that the narrow 12 CO and 13 CO J ϭ 6-5 emission observed toward many low-mass young stellar objects is produced in molecular material in the circumstellar envelope, which is heated by the 10,000 K radiation field generated in the inner part of the accretion disk. Ultraviolet photons traveling through the biconical cavity evacuated by the bipolar outflow are scattered by dust grains present in the low-density material in the cavity. These photons are not energetic enough to photodissociate H 2 and CO, but can heat the envelope surrounding the cavity. The temperature structure and the CO excitation of this photon-dominated region are computed using two-dimensional Monte Carlo methods. It is found that the material is heated up to a few hundred K close to the cavity wall, and that the observed low-velocity mid-J CO emission can be well explained by our model for a wide range in envelope density and stellar luminosity. Emergent CO spectra are compared to observations of the embedded low-mass YSO IRAS 04361ϩ2547 (TMR-1).

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“…The liquid-helium-cooled SIS mixer receiver described by Kooi et al (1994) was used in doublesideband (DSB) mode, with the lower sideband (LSB) centered at the frequency of the 2 ϭ 1, 1 10 3 1 01 transition of H 2 O. The rest frequency of this line is 658.00655 GHz and has an uncertainty =0.1 MHz, corresponding to a radial velocity uncertainty of less than 0.05 km s Ϫ1 (Helminger, Messer, & De Lucia 1983;Pearson et al 1991).…”

Section: Observationsmentioning

confidence: 99%

Discovery of Strong Vibrationally Excited Water Masers at 658 GH[CLC]z[/CLC] toward Evolved Stars

Menten

1995

The Astrophysical Journal

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We report the astronomical discovery of the 1 10 3 1 01 rotational transition within the 2 ϭ 1 vibrationally excited state of water vapor (H 2 O). Using the 10.4 m telescope of the Caltech Submillimeter Observatory, we detect strong maser emission in this line, which has a frequency near 658 GHz, toward a diverse sample of oxygen-rich red giant and supergiant stars. In circumstellar envelopes these 658 GHz H 2 O masers appear to be as common as SiO masers and H 2 O masers in other transitions, while we fail to detect 658 GHz H 2 O emission toward the W49 N and W51 N star-forming regions. For all of the 11 stars detected, the luminosity in the 658 GHz H 2 O transition is comparable to or higher than the luminosity of any other known SiO or H 2 O maser line.

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A lownoise 665 GHz SIS quasi-particle waveguide receiver

Cited by 24 publications

References 18 publications

H₂and CO Emission from Disks around T Tauri and Herbig Ae Pre–Main‐Sequence Stars and from Debris Disks around Young Stars: Warm and Cold Circumstellar Gas

H₂and CO Emission from Disks around T Tauri and Herbig Ae Pre–Main‐Sequence Stars and from Debris Disks around Young Stars: Warm and Cold Circumstellar Gas

Photon Heating of Envelopes around Young Stellar Objects: An Explanation for CO [ITAL]J[/ITAL] = 6–5 Emission

Discovery of Strong Vibrationally Excited Water Masers at 658 GH[CLC]z[/CLC] toward Evolved Stars

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A lownoise 665 GHz SIS quasi-particle waveguide receiver

Cited by 24 publications

References 18 publications

H2and CO Emission from Disks around T Tauri and Herbig Ae Pre–Main‐Sequence Stars and from Debris Disks around Young Stars: Warm and Cold Circumstellar Gas

H2and CO Emission from Disks around T Tauri and Herbig Ae Pre–Main‐Sequence Stars and from Debris Disks around Young Stars: Warm and Cold Circumstellar Gas

Photon Heating of Envelopes around Young Stellar Objects: An Explanation for CO [ITAL]J[/ITAL] = 6–5 Emission

Discovery of Strong Vibrationally Excited Water Masers at 658 GH[CLC]z[/CLC] toward Evolved Stars

Contact Info

Product

Resources

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H₂and CO Emission from Disks around T Tauri and Herbig Ae Pre–Main‐Sequence Stars and from Debris Disks around Young Stars: Warm and Cold Circumstellar Gas

H₂and CO Emission from Disks around T Tauri and Herbig Ae Pre–Main‐Sequence Stars and from Debris Disks around Young Stars: Warm and Cold Circumstellar Gas