The hot core towards the intermediate mass protostar NGC7129 FIRS 2: Chemical similarities with Orion KL

NGC 7129 FIRS 2 (hereafter FIRS 2) is an intermediate-mass (2 to 8 Msun) protostar located at a distance of 1250 pc. High spatial resolution observations are required to resolve the hot core at its center. We present a molecular survey from 218200 MHz to 221800 MHz carried out with the IRAM Plateau de Bure Interferometer. These observations were complemented with a long integration single-dish spectrum taken with the IRAM 30m telescope. We used a Local Thermodynamic Equilibrium (LTE) single temperature code to model the whole dataset. The interferometric spectrum is crowded with a total of ~300 lines from which a few dozens remain unidentified yet. The spectrum has been modeled with a total of 20 species and their isomers, isotopologues and deuterated compounds. Complex molecules like methyl formate (CH3OCHO), ethanol (CH3CH2OH), glycolaldehyde (CH2OHCHO), acetone (CH3COCH3), dimethyl ether (CH3OCH3), ethyl cyanide (CH3CH2CN) and the aGg' conformer of ethylene glycol (aGg'-(CH2OH)_2) are among the detected species. The detection of vibrationally excited lines of CH3CN, CH3OCHO, CH3OH, OCS, HC3N and CH3CHO proves the existence of gas and dust at high temperatures. In fact, the gas kinetic temperature estimated from the vibrational lines of CH3CN, ~405 K, is similar to that measured in massive hot cores. Our data allow an extensive comparison of the chemistry in FIRS~2 and the Orion hot core. We find a quite similar chemistry in FIRS 2 and Orion. Most of the studied fractional molecular abundances agree within a factor of 5. Larger differences are only found for the deuterated compounds D2CO and CH2DOH and a few molecules (CH3CH2CN, SO2, HNCO and CH3CHO). Since the physical conditions are similar in both hot cores, only different initial conditions (warmer pre-collapse phase in the case of Orion) and/or different crossing time of the gas in the hot core can explain this behavior.Comment: 30 pages, 9 figure

Spin properties of dense near-surface ensembles of nitrogen-vacancy centres in diamond

We present a study of the spin properties of dense layers of near-surface nitrogen-vacancy (NV) centres in diamond created by nitrogen ion implantation. The optically detected magnetic resonance contrast and linewidth, spin coherence time, and spin relaxation time, are measured as a function of implantation energy, dose, annealing temperature and surface treatment. To track the presence of damage and surface-related spin defects, we perform in situ electron spin resonance spectroscopy through both double electron-electron resonance and cross-relaxation spectroscopy on the NV centres. We find that, for the energy ($4-30$~keV) and dose ($5\times10^{11}-10^{13}$~ions/cm$^2$) ranges considered, the NV spin properties are mainly governed by the dose via residual implantation-induced paramagnetic defects, but that the resulting magnetic sensitivity is essentially independent of both dose and energy. We then show that the magnetic sensitivity is significantly improved by high-temperature annealing at $\geq1100^\circ$C. Moreover, the spin properties are not significantly affected by oxygen annealing, apart from the spin relaxation time, which is dramatically decreased. Finally, the average NV depth is determined by nuclear magnetic resonance measurements, giving $\approx10$-17~nm at 4-6 keV implantation energy. This study sheds light on the optimal conditions to create dense layers of near-surface NV centres for high-sensitivity sensing and imaging applications.Comment: 12 pages, 7 figure

Herschel observations in the ultracompact HII region Mon R2: Water in dense Photon-dominated regions (PDRs)

Mon R2, at a distance of 830 pc, is the only ultracompact HII region (UC HII) where the photon-dominated region (PDR) between the ionized gas and the molecular cloud can be resolved with Herschel. HIFI observations of the abundant compounds 13CO, C18O, o-H2-18O, HCO+, CS, CH, and NH have been used to derive the physical and chemical conditions in the PDR, in particular the water abundance. The 13CO, C18O, o-H2-18O, HCO+ and CS observations are well described assuming that the emission is coming from a dense (n=5E6 cm-3, N(H2)>1E22 cm-2) layer of molecular gas around the UC HII. Based on our o-H2-18O observations, we estimate an o-H2O abundance of ~2E-8. This is the average ortho-water abundance in the PDR. Additional H2-18O and/or water lines are required to derive the water abundance profile. A lower density envelope (n~1E5 cm-3, N(H2)=2-5E22 cm-2) is responsible for the absorption in the NH 1_1-0_2 line. The emission of the CH ground state triplet is coming from both regions with a complex and self-absorbed profile in the main component. The radiative transfer modeling shows that the 13CO and HCO+ line profiles are consistent with an expansion of the molecular gas with a velocity law, v_e =0.5 x (r/Rout)^{-1} km/s, although the expansion velocity is poorly constrained by the observations presented here.Comment: 4 pages, 5 figure

Polarisation Observations of VY Canis Majoris Water Vapour 5{32}-4{41} 620.701 GHz Maser Emission with HIFI

CONTEXT: Water vapour maser emission from evolved oxygen-rich stars remains poorly understood. Additional observations, including polarisation studies and simultaneous observation of different maser transitions may ultimately lead to greater insight. AIMS: We have aimed to elucidate the nature and structure of the VY CMa water vapour masers in part by observationally testing a theoretical prediction of the relative strengths of the 620.701 GHz and the 22.235 GHz maser components of ortho water vapour. METHODS: In its high-resolution mode (HRS) the Herschel Heterodyne Instrument for the Infrared (HIFI) offers a frequency resolution of 0.125 MHz, corresponding to a line-of-sight velocity of 0.06 km/s, which we employed to obtain the strength and linear polarisation of maser spikes in the spectrum of VY CMa at 620.701 GHz. Simultaneous ground based observations of the 22.235 GHz maser with the Max-Planck-Institut f\"ur Radioastronomie 100-meter telescope at Effelsberg, provided a ratio of 620.701 GHz to 22.235 GHz emission. RESULTS:We report the first astronomical detection to date of water vapour maser emission at 620.701 GHz. In VY CMa both the 620.701 and the 22.235 GHz polarisation are weak. At 620.701 GHz the maser peaks are superposed on what appears to be a broad emission component, jointly ejected asymmetrically from the star. We observed the 620.701 GHz emission at two epochs 21 days apart, both to measure the potential direction of linearly polarised maser components and to obtain a measure of the longevity of these components. Although we do not detect significant polarisation levels in the core of the line, they rise up to approximately 6% in its wings

Spitzer imaging of the jet driving the NGC 2264 G outflow

We present new infrared imaging of the NGC 2264 G protostellar outflow region, obtained with the InfraRed Array Camera (IRAC) on-board the Spitzer Space Telescope. A jet in the red outflow lobe (eastern lobe) is clearly detected in all four IRAC bands and, for the first time, is shown to continuously extend over the entire length of the red outflow lobe traced by CO observations. The redshifted jet also extends to a deeply embedded Class 0 source, VLA 2, confirming previous suggestions that it is the driving source of the outflow (Gomez et al. 1994). The images show that the easternmost part of the redshifted jet exhibits what appear to be multiple changes of direction. To understand the redshifted jet morphology we explore several mechanisms that could generate such apparent changes of direction. From this analysis, we conclude that the redshifted jet structure and morphology visible in the IRAC images can be largely, although not entirely, explained by a slowly precessing jet (period ~8000 yr) that lies mostly on the plane of the sky. It appears that the observed changes in the redshifted jet direction may be sufficient to account for a significant fraction of the broadening of the outflow lobe observed in the CO emission.Comment: Accepted for publication in MNRAS. The paper has 7 pages and 4 figures. Preprint with high resolution images is available at http://www.cfa.harvard.edu/~pteixeir/publications.htm

Hydrides in Young Stellar Objects: Radiation tracers in a protostar-disk-outflow system

Context: Hydrides of the most abundant heavier elements are fundamental molecules in cosmic chemistry. Some of them trace gas irradiated by UV or X-rays. Aims: We explore the abundances of major hydrides in W3 IRS5, a prototypical region of high-mass star formation. Methods: W3 IRS5 was observed by HIFI on the Herschel Space Observatory with deep integration (about 2500 s) in 8 spectral regions. Results: The target lines including CH, NH, H3O+, and the new molecules SH+, H2O+, and OH+ are detected. The H2O+ and OH+ J=1-0 lines are found mostly in absorption, but also appear to exhibit weak emission (P-Cyg-like). Emission requires high density, thus originates most likely near the protostar. This is corroborated by the absence of line shifts relative to the young stellar object (YSO). In addition, H2O+ and OH+ also contain strong absorption components at a velocity shifted relative to W3 IRS5, which are attributed to foreground clouds. Conclusions: The molecular column densities derived from observations correlate well with the predictions of a model that assumes the main emission region is in outflow walls, heated and irradiated by protostellar UV radiation.Comment: Astronomy and Astrophysics Letters, in pres

Sensitive limits on the abundance of cold water vapor in the DM Tau protoplanetary disk

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 3sigma levels in 0.5 km/s 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 and an integrated intensity of 16.0 mK km/s. The latter constitutes a 6sigma 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.Comment: 5 pages, 3 figures. Accepted for publication in the Herschel HIFI special issue of A&

Water in Star-Forming Regions with the Herschel Space Observatory (WISH): Overview of key program and first results

`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 sources are targeted covering a wide range of luminosities and evolutionary stages, from cold pre-stellar cores to warm protostellar envelopes and outflows to disks around young stars. Both the HIFI and PACS instruments are used to observe a variety of lines of H2O, H218O and chemically related species. An overview of the scientific motivation and observational strategy of the program is given together with the modeling approach and analysis tools that have been developed. Initial science results are presented. These include a lack of water in cold gas at abundances that are lower than most predictions, strong water emission from shocks in protostellar environments, the importance of UV radiation in heating the gas along outflow walls across the full range of luminosities, and surprisingly widespread detection of the chemically related hydrides OH+ and H2O+ in outflows and foreground gas. Quantitative estimates of the energy budget indicate that H2O is generally not the dominant coolant in the warm dense gas associated with protostars. Very deep limits on the cold gaseous water reservoir in the outer regions of protoplanetary disks are obtained which have profound implications for our understanding of grain growth and mixing in disks.Comment: 71 pages, 10 figures, PASP, in pres

Discovery of water vapour in the carbon star V Cygni from observations with Herschel/HIFI

We report the discovery of water vapour toward the carbon star V Cygni. We have used Herschel's HIFI instrument, in dual beam switch mode, to observe the 1(11) - 0(00) para-water transition at 1113.3430 GHz in the upper sideband of the Band 4b receiver. The observed spectral line profile is nearly parabolic, but with a slight asymmetry associated with blueshifted absorption, and the integrated antenna temperature is 1.69 \pm 0.17 K km/s. This detection of thermal water vapour emission, carried out as part of a small survey of water in carbon-rich stars, is only the second such detection toward a carbon-rich AGB star, the first having been obtained by the Submillimeter Wave Astronomy Satellite toward IRC+10216. For an assumed ortho-to-para ratio of 3 for water, the observed line intensity implies a water outflow rate ~ (3 - 6) E-5 Earth masses per year and a water abundance relative to H2 of ~ (2-5) E-6. This value is a factor of at least 1E+4 larger than the expected photospheric abundance in a carbon-rich environment, and - as in IRC+10216 - raises the intriguing possibility that the observed water is produced by the vapourisation of orbiting comets or dwarf planets. However, observations of the single line observed to date do not permit us to place strong constraints upon the spatial distribution or origin of the observed water, but future observations of additional transitions will allow us to determine the inner radius of the H2O-emitting zone, and the H2O ortho-to-para ratio, and thereby to place important constraints upon the origin of the observed water emission.Comment: Accepted for publication in A&A (HIFI special issue