We present ~2x2 spectral-maps of Orion BN/KL outflows taken with Herschel at ~12 resolution. For the first time in the far-IR domain, we spatially resolve the emission associated with the bright H2 shocked regions Peak 1 and Peak 2 from that of the H
ot Core and ambient cloud. We analyze the ~54-310um spectra taken with the PACS and SPIRE spectrometers. More than 100 lines are detected, most of them rotationally excited lines of 12CO (up to J=48-47), H2O, OH, 13CO, and HCN. Peaks 1/2 are characterized by a very high L(CO)/L(FIR)~5x10^{-3} ratio and a plethora of far-IR H2O emission lines. The high-J CO and OH lines are a factor ~2 brighter toward Peak 1 whereas several excited H2O lines are ~50% brighter toward Peak 2. A simplified non-LTE model allowed us to constrain the dominant gas temperature components. Most of the CO column density arises from Tk~200-500 K gas that we associate with low-velocity shocks that fail to sputter grain ice mantles and show a maximum gas-phase H2O/CO~10^{-2} abundance ratio. In addition, the very excited CO (J>35) and H2O lines reveal a hotter gas component (Tk~2500 K) from faster (v_S>25 km/s) shocks that are able to sputter the frozen-out H2O and lead to high H2O/CO>~1 abundance ratios. The H2O and OH luminosities cannot be reproduced by shock models that assume high (undepleted) abundances of atomic oxygen in the preshock gas and/or neglect the presence of UV radiation in the postshock gas. Although massive outflows are a common feature in other massive star-forming cores, Orion BN/KL seems more peculiar because of its higher molecular luminosities and strong outflows caused by a recent explosive event.
Using the IRAM 30m telescope we have surveyed a $1times0.8^{circ}$ part of the Orion molecular cloud in the $^{12}$CO and $^{13}$CO (2-1) lines with a maximal spatial resolution of $sim$11 and spectral resolution of $sim$ 0.4 km~s$^{-1}$. The cloud a
ppears filamentary, clumpy and with a complex kinematical structure. We derive an estimated mass of the cloud of 7700 M$_{text{Sun}}$ (half of which is found in regions with visual extinctions $A_V$ below $sim$10) and a dynamical age for the nebula of the order of 0.2 Myrs. The energy balance suggests that magnetic fields play an important role in supporting the cloud, at large and small scales. According to our analysis, the turbulent kinetic energy in the molecular gas due to outflows is comparable to turbulent kinetic energy resulting from the interaction of the cloud with the HII region. This latter feedback appears negative, i.e. the triggering of star formation by the HII region is inefficient in Orion. The reduced data as well as additional products such as the column density map are made available online at http://userpages.irap.omp.eu/~oberne/Olivier_Berne/Data.
We report on the detection of hydromagnesium isocyanide, HMgNC, in the laboratory and in the carbon rich evolved star IRC+10216. The J=1-0 and J=2-1 lines were observed in our microwave laboratory equipment in Valladolid with a spectral accuracy of 3
,KHz. The hyperfine structure produced by the Nitrogen atom was resolved for both transitions. The derived rotational constants from the laboratory data are $B_0$=5481.4333(6),MHz, $D_0$=2.90(8),KHz, and $eQq(N)$=-2.200(2),MHz. The predicted frequencies for the rotational transitions of HMgNC in the millimeter domain have an accuracy of 0.2-0.7,MHz. Four rotational lines of this species, J=8-7, J=10-9, J=12-11 and J=13-12, have been detected towards IRC+10216. The differences between observed and calculated frequencies are $<$0.5,MHz. The rotational constants derived from space frequencies are $B_0$=5481.49(3),MHz and $D_0$=3.2(1),KHz, i.e., identical to the laboratory ones. A merged fit to the laboratory and space frequencies provides $B_0$=5481.4336(4),MHz and $D_0$=2.94(5),KHz. We have derived a column density for HMgNC of (6$pm$2)$times10^{11}$,cm$^{-2}$. From the observed line profiles the molecule have to be produced produced in the layer where other metal-isocyanides have been already found in this source. The abundance ratio between MgNC and its hydrogenated variety, HMgNC, is $simeq$20.
Aims. Excitation of far-infrared and submillimetric molecular lines may originate from nonreactive collisions, chemical formation, or far infrared, near-infrared, and optical fluorescences. As a template, we investigate the impact of each of these pr
ocesses on the excitation of the methylidyne cation CH+ and on the intensities of its rotational transitions recently detected in emission in dense photodissociation regions (PDRs) and in planetary nebulae. Methods. We have developed a nonlocal thermodynamic equilibrium (non-LTE) excitation model that includes the entire energy structure of CH+, i.e. taking into account the pumping of its vibrational and bound and unbound electronic states by near-infrared and optical photons. The model includes the theoretical cross-sections of nonreactive collisions with H, H2, He, and e-, and a Boltzmann distribution is used to describe the probability of populating the excited levels of CH+ during its chemical formation by hydrogenation of C+. To confirm our results we also performed an extensive analytical study, which we use to predict the main excitation process of several diatomic molecules, namely HF, HCl, SiO, CS, and CO. Results. At densities nH = 10^4 cm-3, the excitation of the rotational levels of CH+ is dominated by the radiative pumping of its electronic, vibrational, and rotational states if the intensities of the radiation field at sim 0.4, sim 4, and sim 300 mum are stronger than 10^5, 10^8, and 10^4 times those of the local interstellar radiation field (ISRF). Below these values, the chemical pumping is the dominant source of excitation of the J > 1 levels, even at high kinetic temperatures (sim 1000 K). The far-infrared emission lines of CH+ observed in the Orion Bar and the NGC 7027 PDRs are consistent with the predictions of our excitation model assuming an incident far-ultraviolet (FUV) radiation field of sim 3 times 10^4 (in Draines unit) and densities of sim 5 times 10^4 and sim 2 times 10^5 cm-3. In the case of NGC 7027, the estimate of the density is 10 to 100 times lower than those deduced by traditional excitation codes. Applying our model to other X1Sigma+ ground state diatomic molecules, we find that HF, and SiO and HCl are the species the most sensitive to the radiative pumping of their vibrational and bound electronic states. In both cases, the minimal near-infrared and optical/UV radiation field intensities required to modify their rotational level populations are sim 10^3 times those of the local ISRF at densities nH = 10^4 cm-3. All these results point towards interstellar and circumstellar media with densities lower than previously established and cast doubts on the clumpiness of well-studied molecular clouds.
The Plateau de Bure Interferometer has been used to map the continuum emission at 3.4 mm and 1.1 mm together with the J=1->0 and J=3->2 lines of HCN and HCO+ towards the binary star GV Tau. The 3.4 mm observations did not resolve the binary component
s and the HCN J=1->0 and HCO+ J=1->0 line emissions trace the circumbinary disk and the flattened envelope. However, the 1.1 mm observations resolved the individual disks of GV Tau N and GV Tau S and allowed us to study their chemistry. We detected the HCN 3->2 line only towards the individual disk of GV Tau N, and the emission of the HCO+ 3->2 line towards GV Tau S. Simple calculations indicate that the 3->2 line of HCN is formed in the inner R<12 AU of the disk around GV Tau N where the HCN/HCO+ abundance ratio is >300. On the contrary, this ratio is <1.6 in the disk around GV Tau S. The high HCN abundance measured in GV Tau N is well explained by photo-chemical processes in the warm (>400K) and dense disk surface.
We present time dependent chemical models for a dense and warm O-rich gas exposed to a strong far ultraviolet field aiming at exploring the formation of simple organic molecules in the inner regions of protoplanetary disks around T Tauri stars. An up
-to-date chemical network is used to compute the evolution of molecular abundances. Reactions of H2 with small organic radicals such as C2 and C2H, which are not included in current astrochemical databases, overcome their moderate activation energies at warm temperatures and become very important for the gas phase synthesis of C-bearing molecules. The photodissociation of CO and release of C triggers the formation of simple organic species such as C2H2, HCN, and CH4. In timescales between 1 and 10,000 years, depending on the density and FUV field, a steady state is reached in the model in which molecules are continuously photodissociated but also formed, mainly through gas phase chemical reactions involving H2. The application of the model to the upper layers of inner protoplanetary disks predicts large gas phase abundances of C2H2 and HCN. The implied vertical column densities are as large as several 10^(16) cm^(-2) in the very inner disk (< 1 AU), in good agreement with the recent infrared observations of warm C2H2 and HCN in the inner regions of IRS 46 and GV Tau disks. We also compare our results with previous chemical models studying the photoprocessing in the outer disk regions, and find that the gas phase chemical composition in the upper layers of the inner terrestrial zone (a few AU) is predicted to be substantially different from that in the upper layers of the outer disk (> 50 AU).
