| 1. |
- Cederwall, Bo, et al.
(author)
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Evidence for a spin-aligned neutron-proton paired phase from the level structure of 92Pd
- 2011
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In: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 469:7328, s. 68-71
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Journal article (peer-reviewed)abstract
- Shell structure and magic numbers in atomic nuclei were generally explained by pioneering work(1) that introduced a strong spin-orbit interaction to the nuclear shell model potential. However, knowledge of nuclear forces and the mechanisms governing the structure of nuclei, in particular far from stability, is still incomplete. In nuclei with equal neutron and proton numbers (N = Z), enhanced correlations arise between neutrons and protons (two distinct types of fermions) that occupy orbitals with the same quantum numbers. Such correlations have been predicted to favour an unusual type of nuclear superfluidity, termed isoscalar neutron-proton pairing(2-6), in addition to normal isovector pairing. Despite many experimental efforts, these predictions have not been confirmed. Here we report the experimental observation of excited states in the N = Z = 46 nucleus Pd-92. Gamma rays emitted following the Ni-58(Ar-36,2n)Pd-92 fusion-evaporation reaction were identified using a combination of state-of-the-art high-resolution c-ray, charged-particle and neutron detector systems. Our results reveal evidence for a spin-aligned, isoscalar neutron-proton coupling scheme, different from the previous prediction(2-6). We suggest that this coupling scheme replaces normal superfluidity (characterized by seniority coupling(7,8)) in the ground and low-lying excited states of the heaviest N = Z nuclei. Such strong, isoscalar neutron-proton correlations would have a considerable impact on the nuclear level structure and possibly influence the dynamics of rapid proton capture in stellar nucleosynthesis.
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| 2. |
- Falgarone, E., et al.
(author)
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CH+(1-0) and 13CH+(1-0) absorption lines in the direction of massive star-forming regions
- 2010
-
In: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 521:1
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Journal article (peer-reviewed)abstract
- We report the detection of the ground-state rotational transition of the methylidyne cation CH+ and its isotopologue (CH+)-C-13 toward the remote massive star-forming regions W33A, W49N, and W51 with the HIFI instrument onboard the Herschel satellite. Both lines are seen only in absorption against the dust continuum emission of the star-forming regions. The CH+ absorption is saturated over almost the entire velocity ranges sampled by the lines-of-sight that include gas associated with the star-forming regions (SFR) and Galactic foreground material. The CH+ column densities are inferred from the optically thin components. A lower limit of the isotopic ratio [(CH+)-C-12]/[(CH+)-C-13]> 35.5 is derived from the absorptions of foreground material toward W49N. The column density ratio, N(CH+)/N(HCO+), is found to vary by at least a factor 10, between 4 and > 40, in the Galactic foreground material. Line-of-sight 12CH+ average abundances relative to total hydrogen are estimated. Their average value, N(CH+)/NH > 2.6 x 10(-8), is higher than that observed in the solar neighborhood and confirms the high abundances of CH+ in the Galactic interstellar medium. We compare this result to the predictions of turbulent dissipation regions (TDR) models and find that these high abundances can be reproduced for the inner Galaxy conditions. It is remarkable that the range of predicted N(CH+)/ N(HCO+) ratios, from 1 to similar to 50, is comparable to that observed.
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| 3. |
- Gerin, M., et al.
(author)
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Hydride spectroscopy of the diffuse interstellar medium: new clues on the gas fraction in molecular form and cosmic ray ionization rate in relation to H-3(+)
- 2012
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In: Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences. - : The Royal Society. - 1364-503X .- 1471-2962. ; 370:1978, s. 5174-5185
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Journal article (peer-reviewed)abstract
- The Herschel-guaranteed time key programme PRobing InterStellar Molecules with Absorption line Studies (PRISMAS)(1) is providing a survey of the interstellar hydrides containing the elements C, O, N, F and Cl. As the building blocks of interstellar molecules, hydrides provide key information on their formation pathways. They can also be used as tracers of important physical and chemical properties of the interstellar gas that are difficult to measure otherwise. This paper presents an analysis of two sight-lines investigated by the PRISMAS project, towards the star-forming regions W49N and W51. By combining the information extracted from the detected spectral lines, we present an analysis of the physical properties of the diffuse interstellar gas, including the electron abundance, the fraction of gas in molecular form, and constraints on the cosmic ray ionization rate and the gas density.
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| 4. |
- Gerin, M., et al.
(author)
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Interstellar CH absorption in the diffuse interstellar medium along the sight-lines to G10.6-0.4 (W31C), W49N, and W51
- 2010
-
In: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 521:1, s. Article Number: L16-
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Journal article (peer-reviewed)abstract
- We report the detection of the ground state N, J = 1, 3/2 -> 1, 1/2 doublet of the methylidyne radical CH at similar to 532 GHz and similar to 536 GHz with the Herschel/ HIFI instrument along the sight-line to the massive star-forming regions G10.6-0.4 (W31C), W49N, and W51. While the molecular cores associated with these massive star-forming regions show emission lines, clouds in the diffuse interstellar medium are detected in absorption against the strong submillimeter background. The combination of hyperfine structure with emission and absorption results in complex profiles, with overlap of the different hyperfine components. The opacities of most of the CH absorption features are linearly correlated with those of CCH, CN, and HCO+ in the same velocity intervals. In specific narrow velocity intervals, the opacities of CN and HCO+ deviate from the mean trends, giving rise to more opaque absorption features. We propose that CCH can be used as another tracer of the molecular gas in the absence of better tracers, with [CCH]/[H2] similar to 3.2 +/- 1.1 x 10-8. The observed [CN]/[CH], [CCH]/[CH] abundance ratios suggest that the bulk of the diffuse matter along the lines of sight has gas densities nH = n(H) + 2n(H2) ranging between 100 and 1000 cm-3).
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| 5. |
- Gerin, M., et al.
(author)
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Interstellar OH+, H2O+ and H3O+ along the sight-line to G10.6-0.4
- 2010
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In: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 518:4, s. 110-
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Journal article (peer-reviewed)abstract
- We report the detection of absorption lines by the reactive ions OH+, H2O+ and H3O+ along the line of sight to the submillimeter continuum source G10.6$-$0.4 (W31C). We used the Herschel HIFI instrument in dual beam switch mode to observe the ground state rotational transitions of OH+ at 971 GHz, H2O+ at 1115 and 607 GHz, and H3O+ at 984 GHz. The resultant spectra show deep absorption over a broad velocity range that originates in the interstellar matter along the line of sight to G10.6$-$0.4 as well as in the molecular gas directly associated with that source. The OH+ spectrum reaches saturation over most velocities corresponding to the foreground gas, while the opacity of the H2O+ lines remains lower than 1 in the same velocity range, and the H3O+ line shows only weak absorption. For LSR velocities between 7 and 50 kms$^{-1}$ we estimate total column densities of $N$(OH+) $> 2.5 \times 10^{14}$ cm$^{-2}$, $N$(H2O+) $\sim 6 \times 10^{13}$ cm$^{-2}$ and $N$(H3O+) $\sim 4.0 \times 10^{13}$ cm$^{-2}$. These detections confirm the role of O$^+$ and OH$^+$ in initiating the oxygen chemistry in diffuse molecular gas and strengthen our understanding of the gas phase production of water. The high ratio of the OH+ by the H2O+ column density implies that these species predominantly trace low-density gas with a small fraction of hydrogen in molecular form.
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| 6. |
- Lis, D. C., et al.
(author)
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Herschel/HIFI measurements of the ortho/para ratio in water towards Sagittarius B2(M) and W31C
- 2010
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In: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 521:1, s. Article Number: L26 -
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Journal article (peer-reviewed)abstract
- We present Herschel/HIFI observations of the fundamental rotational transitions of ortho- and para-H216O and H218O in absorption towards Sagittarius B2(M) and W31C. The ortho/para ratio in water in the foreground clouds on the line of sight towards these bright continuum sources is generally consistent with the statistical high-temperature ratio of 3, within the observational uncertainties. However, somewhat unexpectedly, we derive a low ortho/para ratio of 2.35 +/- 0.35, corresponding to a spin temperature of similar to 27 K, towards Sagittarius B2(M) at velocities of the expanding molecular ring. Water molecules in this region appear to have formed with, or relaxed to, an ortho/para ratio close to the value corresponding to the local temperature of the gas and dust.
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| 7. |
- Mookerjea, B., et al.
(author)
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Excitation and abundance of C3 in star forming cores Herschel/HIFI observations of the sight-lines to W31C and W49N
- 2010
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In: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 521:1, s. Article Number: L13 -
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Journal article (peer-reviewed)abstract
- We present spectrally resolved observations of triatomic carbon (C-3) in several ro-vibrational transitions between the vibrational ground state and the low-energy nu(2) bending mode at frequencies between 1654-1897 GHz along the sight-lines to the submillimeter continuum sources W31C and W49N, using Herschel's HIFI instrument. We detect C-3 in absorption arising from the warm envelope surrounding the hot core, as indicated by the velocity peak position and shape of the line profile. The sensitivity does not allow to detect C-3 absorption due to diffuse foreground clouds. From the column densities of the rotational levels in the vibrational ground state probed by the absorption we derive a rotation temperature (T-rot) of similar to 50-70 K, which is a good measure of the kinetic temperature of the absorbing gas, as radiative transitions within the vibrational ground state are forbidden. It is also in good agreement with the dust temperatures for W31C and W49N. Applying the partition function correction based on the derived T-rot, we get column densities N(C-3) similar to 7-9 x 10(14) cm(-2) and abundance x(C-3) similar to 10(-8) with respect to H-2. For W31C, using a radiative transfer model including far-infrared pumping by the dust continuum and a temperature gradient within the source along the line of sight we find that a model with x(C-3) = 10(-8), T-kin = 30-50 K, N(C-3) = 1.5 x 10(15) cm(-2) fits the observations reasonably well and provides parameters in very good agreement with the simple excitation analysis.
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| 8. |
- Neufeld, D. A., et al.
(author)
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Herschel/HIFI observations of interstellar OH+ and H2O+ towards W49N: a probe of diffuse clouds with a small molecular fraction
- 2010
-
In: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 521:1, s. Article Number: L10-
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Journal article (peer-reviewed)abstract
- We report the detection of absorption by interstellar hydroxyl cations and water cations, along the sight-line to the bright continuum source W49N. We have used Herschel's HIFI instrument, in dual beam switch mode, to observe the 972 GHz N = 1-0 transition of OH+ and the 1115 GHz 1(11)-0(00) transition of ortho-H2O+. The resultant spectra show absorption by ortho-H2O+, and strong absorption by OH+, in foreground material at velocities in the range 0 to 70 km s(-1) with respect to the local standard of rest. The inferred OH+/H2O+ abundance ratio ranges from similar to 3 to similar to 15, implying that the observed OH+ arises in clouds of small molecular fraction, in the 2-8% range. This conclusion is confirmed by the distribution of OH+ and H2O+ in Doppler velocity space, which is similar to that of atomic hydrogen, as observed by means of 21 cm absorption measurements, and dissimilar from that typical of other molecular tracers. The observed OH+/H abundance ratio of a few x10(-8) suggests a cosmic ray ionization rate for atomic hydrogen of 0.6-2.4 x 10(-16) s(-1), in good agreement with estimates inferred previously for diffuse clouds in the Galactic disk from observations of interstellar H-3(+) and other species.
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| 9. |
- Neufeld, D.A., et al.
(author)
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Strong absorption by interstellar hydrogen fluoride: Herschel/HIFI observations of the sight-line to G10.6-0.4 (W31C)
- 2010
-
In: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 518:4, s. 108-
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Journal article (peer-reviewed)abstract
- We report the detection of strong absorption by interstellar hydrogen fluoride along the sight-line to the submillimeter continuum source G10.6-0.4 (W31C). We have used Herschel's HIFI instrument, in dual beam switch mode, to observe the 1232.4763 GHz J=1-0 HF transition in the upper sideband of the Band 5a receiver. The resultant spectrum shows weak HF emission from G10.6-0.4 at LSR velocities in the range -10 to -3 km/s, accompanied by strong absorption by foreground material at LSR velocities in the range 15 to 50 km/s. The spectrum is similar to that of the 1113.3430 GHz 1(11)-0(00) transition of para-water, although at some frequencies the HF (hydrogen fluoride) optical depth clearly exceeds that of para-H2O. The optically-thick HF absorption that we have observed places a conservative lower limit of 1.6E+14 cm-2 on the HF column density along the sight-line to G10.6-0.4. Our lower limit on the HF abundance, 6E-9 relative to hydrogen nuclei, implies that hydrogen fluoride accounts for between ~ 30 and 100% of the fluorine nuclei in the gas phase along this sight-line. This observation corroborates theoretical predictions that - because the unique thermochemistry of fluorine permits the exothermic reaction of F atoms with molecular hydrogen - HF will be the dominant reservoir of interstellar fluorine under a wide range of conditions.
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| 10. |
- Persson, Carina, 1964, et al.
(author)
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First detection of [NII] 205 μm absorption in interstellar gas. Herschel-HIFI observations towards W31C, W49N, W51, and G34.3+0.1.
- 2014
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In: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 568, s. 37-
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Journal article (peer-reviewed)abstract
- We present high resolution [N II] 205 μm (3^P_1 − 3^P_0) spectra obtained with Herschel-HIFI towards a small sample of far-infrared bright star forming regions in the Galactic plane: All sources display an emission line profile associated directly with the H II regions themselves. For the first time we also detect absorption of the [N II] 205 μm line by extended low-density foreground material towards W 31C and W 49N over a wide range of velocities. We attribute this absorption to the warm ionised medium (WIM) and find N(N+) ≈ 1.5×10^17 cm^-2 towards both sources. This is in agreement with recent Herschel-HIFI observations of [C II] 158 μm, also observed in absorption in the same sight-lines, if ≈7–10% of all C + ions exist in the WIM on average. Using an abundance ratio of [N]/[H] = 6.76×10^-5 in the gas phase we find that the mean electron and proton volume densities are ∼0.1–0.3 cm^-3 assuming a WIM volume filling fraction of 0.1–0.4 with a corresponding line-of-sight filling fraction of 0.46–0.74. A low density and a high WIM filling fraction are also supported by RADEX modelling of the [N II] 205 μm absorption and emission together with visible emission lines attributed mainly to the WIM. The detection of the 205 μm line in absorption emphasises the importance of a high spectral resolution, and also offers a new tool for investigation of the WIM.
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| 11. |
- Persson, Carina, 1964, et al.
(author)
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Nitrogen hydrides in interstellar gas Herschel/HIFI observations towards G10.6-0.4 (W31C)
- 2010
-
In: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 521:1, s. Article Number: L45 -
-
Journal article (peer-reviewed)abstract
- The HIFI instrument on board the Herschel Space Observatory has been used to observe interstellar nitrogen hydrides along the sight-line towards G10.6-0.4 in order to improve our understanding of the interstellar chemistry of nitrogen. We report observations of absorption in NH N = 1
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| 12. |
- Persson, Carina, 1964, et al.
(author)
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Nitrogen hydrides in interstellar gas II. Analysis of Herschel/HIFI observations towards W49N and G10.6-0.4 (W31C)
- 2012
-
In: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 543:Article Number: A145, s. 145-179
-
Journal article (peer-reviewed)abstract
- As a part of the Herschel key programme PRISMAS, we have used the Herschel-HIFI instrument to observe interstellar nitrogen hydrides along the sight-lines towards eight high-mass star-forming regions in order to elucidate the production pathways leading to nitrogen-bearing species in diffuse gas. Here, we report observations towards W49N of the NH N = 1 - 0, J = 2 - 1, and J = 1 - 0, ortho-NH2 N_(Ka, K_c) J = 1_(1,1) 3/2 - 0_(0,0) 1/2, ortho-NH3 J_K = 1_0 - 0_0 and 2_0 - 1_0, para-NH3 J_K = 2_1 - 1_1 transitions, and unsuccessful searches for NH+. All detections show absorption by foreground material over a wide range of velocities, as well as absorption associated directly with the hot-core source itself. As in the previously published observations towards G10.6-0.4, the NH, NH2 and NH3 spectra towards W49N show strikingly similar and non-saturated absorption features. We decompose the absorption of the foreground material towards W49N into different velocity components in order to investigate whether the relative abundances vary among the velocity components, and, in addition, we re-analyse the absorption lines towards G10.6-0.4 in the same manner. Abundances, with respect to molecular hydrogen, in each velocity component are estimated using CH, which is found to correlate with H2 in the solar neighbourhood diffuse gas. The analysis points to a co-existence of the nitrogen hydrides in diffuse or translucent interstellar gaswith a high molecular fraction. Towards both sources, we find that NH is always at least as abundant as both o-NH2 and o-NH3, in sharp contrast to previous results for dark clouds. We find relatively constant N(NH)/N(o-NH3) and N(o-NH2)/N(o-NH3) ratios with mean values of 3.2 and 1.9 towards W49N, and 5.4 and 2.2 towards G10.6-0.4, respectively. The mean abundance of o-NH4 is ~2x10^-9 towards both sources. The nitrogen hydrides also show linear correlations with CN and HNC towards both sources, and looser correlations with CH. The upper limits on the NH+ abundance indicate column densities
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| 13. |
- Scott, J. K., et al.
(author)
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Centralization of services for children born with orofacial clefts in the United kingdom : a cross-sectional survey
- 2014
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In: Cleft Palate Craniofac J. - 1545-1569 (Electronic) 1055-6656 (Linking) ; 51:5, s. e102-9
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Journal article (peer-reviewed)abstract
- Objective : To examine current provision of cleft lip and/or palate services in the U.K. and compliance with recommendations made by the Clinical Standards Advisory Group (CSAG) in 1998. Design : Cross-sectional questionnaire survey. Setting : All 11 services within the U.K. providing care for children born with a cleft lip and palate. Participants : Members from each healthcare specialty in each U.K. cleft team. Interventions : Self-administered postal questionnaires enquired about the provision of cleft services. Data were collected about the overall cleft service, team coordination, hearing, orthodontics, pediatric dentistry, primary cleft surgery, psychology, restorative dentistry, secondary surgery, specialist cleft nursing, and speech and language therapy. Results : Questionnaires were returned from members of 130/150 cleft teams (87%) and these showed that U.K. cleft services have been restructured to 11 centralized services with 17 primary operative sites and 61 peripheral sites. All services provide care through a multidisciplinary (MDT) model, but the composition of each team varies. Primary cleft surgery and orthodontics were the only specialties that were represented in all cleft teams. Specialties may be represented in a team but their attendance at MDT clinics is variable. Only one team met all of the CSAG recommendations. Conclusions : Our survey shows that cleft services have centralized over the last 10 years, and an MDT model of care has been adopted. Further research is needed to show how this has influenced outcomes and to see whether some models of centralized care are associated with better outcomes.
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| 14. |
- Sonnentrucker, P., et al.
(author)
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Detection of hydrogen fluoride absorption in diffuse molecular clouds with Herschel/HIFI: an ubiquitous tracer of molecular gas
- 2010
-
In: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 521:1, s. Article Number: L12-
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Journal article (peer-reviewed)abstract
- We discuss the detection of absorption by interstellar hydrogen fluoride (HF) along the sight line to the submillimeter continuum sources W49N and W51. We have used Herschel's HIFI instrument in dual beam switch mode to observe the 1232.4762 GHz J = 1-0 HF transition in the upper sideband of the band 5a receiver. We detected foreground absorption by HF toward both sources over a wide range of velocities. Optically thin absorption components were detected on both sight lines, allowing us to measure - as opposed to obtain a lower limit on - the column density of HF for the first time. As in previous observations of HF toward the source G10.6-0.4, the derived HF column density is typically comparable to that of water vapor, even though the elemental abundance of oxygen is greater than that of fluorine by four orders of magnitude. We used the rather uncertain N(CH) - N(H-2) relationship derived previously toward diffuse molecular clouds to infer the molecular hydrogen column density in the clouds exhibiting HF absorption. Within the uncertainties, we find that the abundance of HF with respect to H-2 is consistent with the theoretical prediction that HF is the main reservoir of gas-phase fluorine for these clouds. Thus, hydrogen fluoride has the potential to become an excellent tracer of molecular hydrogen, and provides a sensitive probe of clouds of small H-2 column density. Indeed, the observations of hydrogen fluoride reported here reveal the presence of a low column density diffuse molecular cloud along the W51 sight line, at an LSR velocity of similar to 24 km s(-1), that had not been identified in molecular absorption line studies prior to the launch of Herschel.
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