Physical conditions in the Protoplanetary Nebula CRL 618 derived from observations of vibrationally excited HCCCN

We used the Effelsberg 100m and IRAM 30m telescopes to observe vibrationally excited cyanoacetylene (HCCCN) in several rotational transitions toward the proto-planetary nebula CRL618. Lines from 9 different vibrationally excited states with energies ranging up to 1600 K above ground were detected. The lines show P Cygni profiles indicating that the HCCCN emission originates from an expanding and accelerating molecular envelope. The HCCCN rotational temperature varies with velocity, peaks at 520 K, 3 km/s blue-shifted from the systemic velocity and decreases with higher blueshift of the gas. The column density of the absorbing HCCCN is 3-6 x 1E17 cm^2. We modeled spectra based on spherical models of the expanding envelope which provide an excellent fit to the observations, and discuss the implications of the models. Additionally, lines from 13C substituted cyanoacetylene were observed. They can be used to constrain the 12C/13C ratio in this source to 10+-2.Comment: 27 pages, 9 figures, to appear in Ap

Hot HCN around young massive stars at 0.1" resolution

Massive stars form deeply embedded in dense molecular gas, which they stir and heat up and ionize. During an early phase, the ionization is confined to hypercompact HII regions, and the stellar radiation is entirely absorbed by dust, giving rise to a hot molecular core. To investigate the innermost structure of such high-mass star-forming regions, we observed vibrationally excited HCN (via the direct $\ell$-type transition of v2=1, $\Delta J$=0, J=13, which lies 1400 K above ground) toward the massive hot molecular cores G10.47+0.03, SgrB2-N, and SgrB2-M with the Very Large Array (VLA) at 7 mm, reaching a resolution of about 1000 AU (0.1"). We detect the line both in emission and in absorption against HII regions. The latter allows to derive lower limits on the column densities of hot HCN, which are several times $10^{19}$ cm$^{-2}$. We see indication of expansion motions in G10.47+0.03 and detect velocity components in SgrB2-M at 50, 60, and 70 km/s relative to the Local Standard of Rest. The emission originates in regions of less than 0.1 pc diameter around the hypercompact HII regions G10.47+0.03 B1 and SgrB2-N K2, and reaches brightness temperatures of more than 200 K. Using the three-dimensional radiative transfer code RADMC-3D, we model the sources as dense dust cores heated by stars in the HII regions, and derive masses of hot (>300 K) molecular gas of more than 100 solar masses (for an HCN fractional abundance of 10$^{-5}$), challenging current simulations of massive star formation. Heating only by the stars in the HII regions is sufficient to produce such large quantities of hot molecular gas, provided that dust is optically thick to its own radiation, leading to high temperatures through diffusion of radiation.Comment: 12 pages, 14 figures, accepted for publication in A&

Rotational Spectroscopy of PAHs: Acenaphthene, Acenaphthylene and Fluorene

Pure rotational spectra of three polycyclic aromatic hydrocarbons - acenaphthene, acenaphthylene and fluorene - have been obtained by Fourier transform microwave spectroscopy of a molecular beam and subsequently by millimeter wave absorption spectroscopy for acenaphthene and fluorene. The data presented here will be useful for deep radio astronomical searches for PAHs employing large radio telecopes.Comment: 2 pages, 1 figure (uses iaus.sty), to appear in IAU Symposium No. 231, Astrochemistry - Recent Successes and Current Challenges, eds. D. C. Lis, G. A. Blake & E. Herbst (Cambridge Univ. Press

New ammonia masers towards NGC6334I

We report the detection of new ammonia masers in the non-metastable (8,6) and (11,9) transitions towards the massive star forming region NGC6334I. Observations were made with the ATCA interferometer and the emitting region appears unresolved in the 2.7" x 0.8" beam, with deconvolved sizes less than an arcsecond. We estimate peak brightness temperatures of 7.8 x 10^5 and 1.2 x 10^5 K for the (8,6) and (11,9) transitions, respectively. The masers appear coincident both spatially and in velocity with a previously detected ammonia (6,6) maser. We also suggest that emission in the (10,9), (9,9) and (7,6) transitions may also be masers, based on their narrow line widths and overlapping velocity ranges with the above masers, as observed with the single-dish Mopra radiotelescope

PURE ROTATIONAL SPECTRUM OF CN+

The pure rotational spectrum of the elusive CN$^+$ cation has been observed for the first time using the cryogenic ion trap apparatus Coltrap by applying an action spectroscopy scheme. For the $^{12}$C$^{14}$N$^+$ species, the three lowest rotational transitions have been observed each of which exhibits hyperfine structure from the presence of the $^{14}$N nucleus. The rare $^{12}$C$^{15}$N$^+$ isotopolog has been studied up to the $J=4-3$ transition. The observations conclusively confirm CN$^+$ to occupy a $^1\Sigma^+$ electronic ground state. Given the ubiquity of the CN radical in space, CN$^+$ is an appealing candidate for future radio astronomical searches

Submillimeter spectroscopy of southern hot cores: NGC6334(I) and G327.3-0.6

High-mass star-forming regions are known to have a rich molecular spectrum from many species. Some of the very highly excited lines are emitted from very hot and dense gas close to the central object(s). The physics and chemistry of the inner cores of two high mass star forming regions, NGC6334(I) and G327.3-0.6, shall be characterized. Submillimeter line surveys with the APEX telescope provide spectra which sample many molecular lines at high excitation stages. Partial spectral surveys were obtained, the lines were identified, physical parameters were determined through fitting of the spectra. Both sources show similar spectra that are comparable to that of the only other high mass star forming region ever surveyed in this frequency range}, Orion-KL, but with an even higher line density. Evidence for very compact, very hot sources is found.Comment: APEX A&A special issue, accepte

A 1.3 cm line survey toward IRC +10216

IRC +10216 is the prototypical carbon star exhibiting an extended molecular circumstellar envelope. Its spectral properties are therefore the template for an entire class of objects. The main goal is to systematically study the $\lambda$ $\sim$1.3 cm spectral line characteristics of IRC +10216. We carried out a spectral line survey with the Effelsberg-100 m telescope toward IRC +10216. It covers the frequency range between 17.8 GHz and 26.3 GHz (K-band). In the circumstellar shell of IRC +10216, we find 78 spectral lines, among which 12 remain unidentified. The identified lines are assigned to 18 different molecules and radicals. A total of 23 lines from species known to exist in this envelope are detected for the first time outside the Solar System and there are additional 20 lines first detected in IRC +10216. The potential orgin of "U" lines is also discussed. Assuming local thermodynamic equilibrium (LTE), we then determine rotational temperatures and column densities of 17 detected molecules. Molecular abundances relative to H$_{2}$ are also estimated. A non-LTE analysis of NH$_{3}$ shows that the bulk of its emission arises from the inner envelope with a kinetic temperature of 70$\pm$20 K. Evidence for NH$_{3}$ emitting gas with higher kinetic temperature is also obtained, and potential abundance differences between various $^{13}$C-bearing isotopologues of HC$_{5}$N are evaluated. Overall, the isotopic $^{12}$C/$^{13}$C ratio is estimated to be 49$\pm$9. Finally, a comparison of detected molecules in the $\lambda$ $\sim$1.3 cm range with the dark cloud TMC-1 indicates that silicate-bearing molecules are more predominant in IRC +10216.Comment: 32 pages, 9 figures, Accepted by A&