Sub-Doppler Investigations of the Spectra of Molecules Isotopologues NH2D and HC3N

With the help of the sub-Doppler spectrometer created at IAP RAS, the spectra of molecules of once-deuterated ammonia NH2D, including 15NH2D, as well as 13C and 15N isotopologues of the molecule HC3N, were studied. Due to measurements based on the Lamb dip, the experimental accuracy of transition frequencies in the range of 85—503 GHz is improved by comparing conventional spectroscopyby approximately two orders of magnitude. The data obtained are of great interest both in studies of physical parameters in star-forming regions and in the search for possible variations of the fundamental constants. The molecule of partially deuterated ammonia NH2D is of particular interest because of the inversion-rotational transitions that lie in the mm spectral range and have different sensitivity to variations in the ratio of the electron mass to the proton mass.При помощи созданного в ИПФ РАН субдоплеровского спектрометра выполнены исследования спектров молекул NH2D, 15NH2D, а также 13C и 15N, изотопологов HC3N. Благодаря измерениям на основе провала Лэмба экспериментальные точности частот переходов в диапазоне 85 503 ГГц улучшены в сравнении с традиционной спектроскопией примерно на два порядка. Полученные данные представляют большой интерес при исследованиях физических параметров в областях звездообразования и при поиске возможных вариаций фундаментальных констант. Молекула NH2D представляет особый интерес из-за инверсионно-вращательных переходов, лежащих в миллиметровой области спектра и обладающих различной чувствительностью к вариации отношения массы электрона к массе протона.Все лабораторные измерения были выполнены благодаря поддержке РФФИ (проект № 16–02–00761). Анализ данных поддержан грантом РНФ (проект № 17–12–01256)

Spatially Resolved Chemistry in Nearby Galaxies I. The Center of IC 342

We have imaged emission from the millimeter lines of eight molecules--C2H, C34S, N2H+, CH3OH, HNCO, HNC, HC3N, and SO--in the central half kpc of the nearby spiral galaxy IC 342. The 5" (~50 pc) resolution images were made with OVRO. Using these maps we obtain a picture of the chemistry within the nuclear region on the sizescales of individual GMCs. Bright emission is detected from all but SO. There are marked differences in morphology for the different molecules. A principal component analysis is performed to quantify similarities and differences among the images. This analysis reveals that while all molecules are to zeroth order correlated, that is, they are all found in dense molecular clouds, there are three distinct groups of molecules distinguished by the location of their emission within the nuclear region. N2H+, C18O, HNC and HCN are widespread and bright, good overall tracers of dense molecular gas. C2H and C34S, tracers of PDR chemistry, originate exclusively from the central 50-100 pc region, where radiation fields are high. The third group of molecules, CH3OH and HNCO, correlates well with the expected locations of bar-induced orbital shocks. The good correlation of HNCO with the established shock tracer molecule CH3OH is evidence that this molecule, whose chemistry has been uncertain, is indeed produced by processing of grains. HC3N is observed to correlate tightly with 3mm continuum emission, demonstrating that the young starbursts are the sites of the warmest and densest molecular gas. We compare our HNC images with the HCN images of Downes et al. (1992) to produce the first high resolution, extragalactic HCN/HNC map: the HNC/HCN ratio is near unity across the nucleus and the correlation of both of these gas tracers with the star formation is excellent. (Abridged).Comment: 54 pages including 10 figures and 8 tables. Accepted for publication in Ap

Searching for chameleon-like scalar fields with the ammonia method

(Abridged) The ammonia method, which has been proposed to explore the electron-to-proton mass ratio, mu = m_e/m_p, is applied to nearby dark clouds in the Milky Way. This ratio, which is measured in different physical environments of high (terrestrial) and low (interstellar) densities of baryonic matter is supposed to vary in chameleon-like scalar field models, which predict strong dependence of both masses and coupling constant on the local matter density. High resolution spectral observations of molecular cores in lines of NH3 (J,K) = (1,1), HC3N J = 2-1, and N2H+ J = 1-0 were performed at three radio telescopes to measure the radial velocity offsets, DeltaV = V_rot - V_inv, between the inversion transition of NH3 (1,1) and the rotational transitions of other molecules with different sensitivities to the parameter dmm = (mu_obs - mu_lab)/mu_lab. The measured values of DeltaV exhibit a statistically significant velocity offset of 23 +/- 4_stat +/- 3_sys m/s. When interpreted in terms of the electron-to-proton mass ratio variation, this infers that dmm = (2.2 +/- 0.4_stat +/- 0.3_sys)x10^{-8}. If only a conservative upper bound is considered, then the maximum offset between ammonia and the other molecules is |DeltaV| <= 30 m/s. This gives the most accurate reference point at z = 0 for dmm: |dmm| <= 3x10^{-8}.Comment: 23 pages, 11 figures, 6 tables. Accepted for publication in A&A. Title and text corrected, references update

TIMASSS: The IRAS16293-2422 Millimeter And Submillimeter Spectral Survey. I. Observations, calibration and analysis of the line kinematics

While unbiased surveys observable from ground-based telescopes have previously been obtained towards several high mass protostars, very little exists on low mass protostars. To fill up this gap, we carried out a complete spectral survey of the bands at 3, 2, 1 and 0.8 mm towards the solar type protostar IRAS16293-2422. The observations covered about 200\,GHz and were obtained with the IRAM-30m and JCMT-15m telescopes. Particular attention was devoted to the inter-calibration of the obtained spectra with previous observations. All the lines detected with more than 3 sigma and free from obvious blending effects were fitted with Gaussians to estimate their basic kinematic properties. More than 4000 lines were detected (with sigma \geq 3) and identified, yielding a line density of approximatively 20 lines per GHz, comparable to previous surveys in massive hot cores. The vast majority (~2/3) of the lines are weak and due to complex organic molecules. The analysis of the profiles of more than 1000 lines belonging 70 species firmly establishes the presence of two distinct velocity components, associated with the two objects, A and B, forming the IRAS16293-2422 binary system. In the source A, the line widths of several species increase with the upper level energy of the transition, a behavior compatible with gas infalling towards a ~1 Mo object. The source B, which does not show this effect, might have a much lower central mass of ~0.1 Mo. The difference in the rest velocities of both objects is consistent with the hypothesis that the source B rotates around the source A. This spectral survey, although obtained with single-dish telescope with a low spatial resolution, allows to separate the emission from 2 different components, thanks to the large number of lines detected. The data of the survey are public and can be retrieved on the web site http://www-laog.obs.ujf-grenoble.fr/heberges/timasss.Comment: 41 pages (26 pages of online Tables), 7 Tables and 6 Figure