The mm-wave spectrum of the C-star envelope IRC+10216 has been continuously surveyed between 129.0 and 172.5 GHz with the IRAM 30-m telescope. 380 lines are detected, of which 317 have been ...identified. The identified lines arise from 30 different molecules and radicals which, in their vast majority, are not observed in hot and dense interstellar clouds such as Orion A or W3(OH). Actually, half of the molecular species identified in the mm-wave spectrum of IRC+10216 were first observed in the course of this spectral survey. The new species include several carbon-chain molecules and radicals, as well as silicon and metallic compounds. They also include molecules containing rare isotopes of C, Mg, Si, S and Cl, whose elemental abundance ratios in the envelope are redetermined. We observe, in particular, four 13C isotopomers of C4H, three of C3N and HC3N, and four doubly-substituted isotopomers of SiS and CS. 63 lines remain unidentified. Probably, a large fraction of those are rotational transitions inside the excited bending states of the abundant species NaCN, C5H, and C6H. We can also expect some lines to be ground state transitions of poorly known silicon and metal compounds, such as the slightly asymmetrical top molecule SiCSi.
The molecular hydrogen explorer H2EX Boulanger, F.; Maillard, J. P.; Appleton, P. ...
Experimental astronomy,
03/2009, Volume:
23, Issue:
1
Journal Article
Peer reviewed
Open access
The Molecular Hydrogen Explorer,
H
2
EX
, was proposed in response to the ESA 2015 - 2025 Cosmic Vision Call as a medium class space mission with NASA and CSA participations. The mission, conceived ...to understand the formation of galaxies, stars and planets from molecular hydrogen, is designed to observe the first rotational lines of the H
2
molecule (28.2, 17.0, 12.3 and 9.7 μm) over a wide field, and at high spectral resolution.
H
2
EX
can provide an inventory of warm (≥ 100 K) molecular gas in a broad variety of objects, including nearby young star clusters, galactic molecular clouds, active galactic nuclei, local and distant galaxies. The rich array of molecular, atomic and ionic lines, as well as solid state features available in the 8 to 29 μm spectral range brings additional science dimensions to
H
2
EX
. We present the optical and mechanical design of the
H
2
EX
payload based on an innovative Imaging Fourier Transform Spectrometer fed by a 1.2 m telescope. The 20’×20’ field of view is imaged on two 1024×1024 Si:As detectors. The maximum resolution of 0.032 cm
− 1
(full width at half maximum) means a velocity resolution of 10 km s
− 1
for the 0 – 0 S(3) line at 9.7 μm. This instrument offers the large field of view necessary to survey extended emission in the Galaxy and local Universe galaxies as well as to perform unbiased extragalactic and circumstellar disks surveys. The high spectral resolution makes
H
2
EX
uniquely suited to study the dynamics of H
2
in all these environments. The mission plan is made of seven wide-field spectro-imaging legacy programs, from the cosmic web to galactic young star clusters, within a nominal two years mission. The payload has been designed to re-use the
Planck
platform and passive cooling design.
The inner layers of circumstellar envelopes around asymptotic giant branch stars are sites where a variety of processes such as thermochemical equilibrium, shocks induced by the stellar pulsation, ...and condensation of dust grains determine the chemical composition of the material that is expelled into the outer envelope layers and, ultimately, into interstellar space. The authors aim at studying the abundances, throughout the whole circumstellar envelope of the carbon star IRC +10216, of several molecules formed in the inner layers in order to constrain the different processes at work in such regions. Observations towards IRC +10216 of CS, SiO, SiS, NaCl, KCl, AlCl, AlF, and NaCN have been carried out with the IRAM 30-m telescope in the 80 GHz-357.5 GHz frequency range. They find that in the inner layers CS, SiO, and SiS have abundances relative to H sub( 2) of ... , ... , and ... , respectively, and that CS and SiS have significant lower abundances in the outer envelope. (ProQuest: ... denotes formulae/symbols omitted.)
We perform a sensitive (line confusion limited), single-side band spectral survey towards Orion KL with the IRAM 30 m telescope, covering the following frequency ranges: 80–115.5 GHz, 130–178 GHz, ...and 197–281 GHz. We detect more than 14 400 spectral features of which 10 040 have been identified up to date and attributed to 43 different molecules, including 148 isotopologues and lines from vibrationally excited states. In this paper, we focus on the study of OCS, HCS+, H2CS, CS, CCS, C3S, and their isotopologues. In addition, we map the OCS J = 18–17 line and complete complementary observations of several OCS lines at selected positions around Orion IRc2 (the position selected for the survey). We report the first detection of OCS ν2 = 1 and ν3 = 1 vibrationally excited states in space and the first detection of C3S in warm clouds. Most of CCS, and almost all C3S, line emission arises from the hot core indicating an enhancement of their abundances in warm and dense gas. Column densities and isotopic ratios have been calculated using a large velocity gradient (LVG) excitation and radiative transfer code (for the low density gas components) and a local thermal equilibrium (LTE) code (appropriate for the warm and dense hot core component), which takes into account the different cloud components known to exist towards Orion KL, the extended ridge, compact ridge, plateau, and hot core. The vibrational temperature derived from OCS ν2 = 1 and ν3 = 1 levels is $\simeq$210 K, similar to the gas kinetic temperature in the hot core. These OCS high energy levels are probably pumped by absorption of IR dust photons. We derive an upper limit to the OC3S, H2CCS, HNCS, HOCS+, and NCS column densities. Finally, we discuss the D/H abundance ratio and infer the following isotopic abundances: 12C/13C = 45 ± 20, 32S/34S = 20 ± 6, 32S/33S = 75 ± 29, and 16O/18O = 250 ± 135.
The high-resolution spectrum of the nu sub(4) band of NH sub(3)D super(+) has been measured by difference frequency IR laser spectroscopy in a multipass hollow cathode discharge cell. From the set of ...molecular constants obtained from the analysis of the spectrum, a value of 262817 + or - 6 MHz (+ or -3sigma) has been derived for the frequency of the 1 sub(0)-0 sub(0) rotational transition. This value supports the assignment to NH sub(3)D super(+) of lines at 262816.7 MHz recorded in radio astronomy observations in Orion-IRc2 and the cold prestellar core B1-bS.
The high-resolution spectrum of the {nu}{sub 4} band of NH{sub 3}D{sup +} has been measured by difference frequency IR laser spectroscopy in a multipass hollow cathode discharge cell. From the set of ...molecular constants obtained from the analysis of the spectrum, a value of 262817 {+-} 6 MHz ({+-}3{sigma}) has been derived for the frequency of the 1{sub 0}-0{sub 0} rotational transition. This value supports the assignment to NH{sub 3}D{sup +} of lines at 262816.7 MHz recorded in radio astronomy observations in Orion-IRc2 and the cold prestellar core B1-bS.
Disks around hot stars in the Trifid nebula Lefloch, B.; Cernicharo, J.; Cesarsky, D. ...
Astronomy and astrophysics (Berlin),
03/2001, Volume:
368, Issue:
3
Journal Article
Peer reviewed
Open access
We report on mid-IR observations of the central region in the Trifid nebula, carried out with ISOCAM in several broad-band infrared filters and in the low resolution spectroscopic mode provided by ...the circular variable filter. Analysis of the emission indicates the presence of a hot dust component (500 to 1000 K) and a warm dust component at lower temperatures (~$150{-}200$ K) around several members of the cluster exciting the H II region, and other stars undetected at optical wavelengths. Complementary VLA observations suggest that the mid-IR emission could arise from a dust cocoon or a circumstellar disk, evaporated under the ionization of the central source and the exciting star of the nebula. In several sources the $\rm 9.7 \mu m$ silicate band is seen in emission. One young stellar source shows indications of crystalline silicates in the circumstellar dust.
A full spectral survey was carried out towards the giant molecular cloud complex, Sagittarius B2 (Sgr B2), using the Infrared Space Observatory (ISO) Long Wavelength Spectrometer (LWS) Fabry–Pérot ...mode. This provided complete wavelength coverage in the range 47–196 μm (6.38–1.53 THz) with a spectral resolution of 30–40 km s−1. This is a unique data set covering wavelengths inaccessible from the ground. It is an extremely important region of the spectrum as it contains both the peak of the thermal emission from dust, and crucial spectral lines of key atomic (O i, C ii, O iii, N ii and N iii) and molecular species (NH3, NH2, NH, H2O, OH, H3O+, CH, CH2, C3, HF and H2D+). In total, 95 spectral lines have been identified and 11 features with absorption depth greater than 3σ remain unassigned. Most of the molecular lines are seen in absorption against the strong continuum, whereas the atomic and ionic lines appear in emission (except for absorption in the O i 63 μm and C ii 158 μm lines). Sgr B2 is located close to the Galactic Centre and so many of the features also show a broad absorption profile due to material located along the line of sight. A full description of the survey data set is given with an overview of each detected species and final line lists for both assigned and unassigned features.
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