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Fuente A.,Observatorio Astronomico Nacional OAN IGN | Cernicharo J.,CSIC - National Institute of Aerospace Technology | Agundez M.,CSIC - National Institute of Aerospace Technology | Agundez M.,University of Bordeaux 1 | Agundez M.,French National Center for Scientific Research
Astrophysical Journal Letters | Year: 2012

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+ toward the binary star GV Tau. The 3.4 mm observations did not resolve the binary components, 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 toward the individual disk of GV Tau N, and the emission of the HCO+ 3→2 line toward 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 photochemical processes in the warm (>400 K) and dense (n > 107 cm-3) disk surface. © 2012. The American Astronomical Society. All rights reserved.

Goicoechea J.R.,CSIC - Institute of Materials Science | Teyssier D.,Herschel Science Center | Etxaluze M.,CSIC - Institute of Materials Science | Etxaluze M.,Rutherford Appleton Laboratory | And 24 more authors.
Astrophysical Journal | Year: 2015

We present the first ∼7.′5 11.′5 velocity-resolved (∼0.2 km s-1) map of the [C ii] 158 μm line toward the Orion molecular cloud 1 (OMC 1) taken with the Herschel/HIFI instrument. In combination with far-IR (FIR) photometric images and velocity-resolved maps of the H41α hydrogen recombination and CO J = 2-1 lines, this data set provides an unprecedented view of the intricate small-scale kinematics of the ionized/photodissociation region (PDR)/molecular gas interfaces and of the radiative feedback from massive stars. The main contribution to the [C ii] luminosity (∼85%) is from the extended, FUV-illuminated face of the cloud (G0 > 500, 5 103 cm-3) and from dense PDRs ( 104, 105 cm-3) at the interface between OMC 1 and the H ii region surrounding the Trapezium cluster. Around ∼15% of the [C ii] emission arises from a different gas component without a CO counterpart. The [C ii] excitation, PDR gas turbulence, line opacity (from [13C ii]), and role of the geometry of the illuminating stars with respect to the cloud are investigated. We construct maps of the L[C ii]/ and / ratios and show that L[C ii]/ decreases from the extended cloud component (∼10-2-10-3) to the more opaque star-forming cores (∼1010-4). The lowest values are reminiscent of the "[C ii] deficit" seen in local ultraluminous IR galaxies hosting vigorous star formation. Spatial correlation analysis shows that the decreasing L[C ii]/ ratio correlates better with the column density of dust through the molecular cloud than with /. We conclude that the [C ii]-emitting column relative to the total dust column along each line of sight is responsible for the observed L[C ii]/ variations through the cloud. © 2015. The American Astronomical Society. All rights reserved..

Fuente A.,Observatorio Astronomico Nacional OAN IGN | Cernicharo J.,CSIC - Institute of Materials Science | Caselli P.,Max Planck Institute for Extraterrestrial Physics | McCoey C.,University of Waterloo | And 9 more authors.
Astronomy and Astrophysics | Year: 2014

Context. This paper is dedicated to the study of the chemistry of the intermediate-mass (IM) hot core NGC 7129 FIRS 2, probably the most compact warm core found in the 2-8 M⊙ stellar mass range. Aims. Our aim is to determine the chemical composition of the IM hot core NGC 7129 FIRS 2, and to provide new insights on the chemistry of hot cores in a more general context. Methods. NGC 7129 FIRS 2 (hereafter, FIRS 2) is located at a distance of 1250 pc and high spatial resolution observations are required to resolve the hot core at its center. We present a molecular survey from 218 200 MHz to 221 800 MHz carried out with the IRAM Plateau de Bure Interferometer (PdBI). These observations were complemented with a long integration single-dish spectrum taken with the IRAM 30 m telescope in Pico de Veleta (Spain). We used a local thermodynamic equilibrium (LTE) single temperature code to model the whole dataset. Results. The interferometric spectrum is crowded with a total of 300 lines from which a few dozen remain unidentified. 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 (CH3OCH 3), 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 CH 3CN, CH3OCHO, CH3OH, OCS, HC3N, and CH3CHO proves the existence of gas and dust at high temperatures. The gas kinetic temperature estimated from the vibrational lines of CH 3CN, ∼405-67 +100 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. Conclusions. 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 and collapse phase in the case of Orion) and/or different crossing times of the gas in the hot core can explain this behavior. We discuss these two scenarios. © ESO, 2014.

Hillen M.,Catholic University of Leuven | Kluska J.,University of Exeter | Le Bouquin J.-B.,CNRS Grenoble Institute for Particle Astrophysics and Cosmology Laboratory | Van Winckel H.,Catholic University of Leuven | And 3 more authors.
Astronomy and Astrophysics | Year: 2016

Aims. We present the first near-IR milli-arcsecond-scale image of a post-AGB binary that is surrounded by hot circumbinary dust. Methods. A very rich interferometric data set in six spectral channels was acquired of IRAS 08544-4431 with the new RAPID camera on the PIONIER beam combiner at the Very Large Telescope Interferometer (VLTI). A broadband image in the H-band was reconstructed by combining the data of all spectral channels using the SPARCO method. Results. We spatially separate all the building blocks of the IRAS 08544-4431 system in our milliarcsecond-resolution image. Our dissection reveals a dust sublimation front that is strikingly similar to that expected in early-stage protoplanetary disks, as well as an unexpected flux signal of ~4% from the secondary star. The energy output from this companion indicates the presence of a compact circum-companion accretion disk, which is likely the origin of the fast outflow detected in Hα. Conclusions. Our image provides the most detailed view into the heart of a dusty circumstellar disk to date. Our results demonstrate that binary evolution processes and circumstellar disk evolution can be studied in detail in space and over time. © ESO, 2016.

Hacar A.,University of Vienna | Kainulainen J.,Max Planck Institute for Astronomy | Tafalla M.,Observatorio Astronomico Nacional OAN IGN | Beuther H.,Max Planck Institute for Astronomy | Alves J.,University of Vienna
Astronomy and Astrophysics | Year: 2016

Filaments play a central role in the molecular clouds' evolution, but their internal dynamical properties remain poorly characterized. To further explore the physical state of these structures, we have investigated the kinematic properties of the Musca cloud. We have sampled the main axis of this filamentary cloud in 13CO and C18O (2-1) lines using APEX observations. The different line profiles in Musca shows that this cloud presents a continuous and quiescent velocity field along its ∼6.5 pc of length. With an internal gas kinematics dominated by thermal motions (i.e. σNT/cs ≲ 1) and large-scale velocity gradients, these results reveal Musca as the longest velocity-coherent, sonic-like object identified so far in the interstellar medium. The transonic properties of Musca present a clear departure from the predicted supersonic velocity dispersions expected in the Larson's velocity dispersion-size relationship, and constitute the first observational evidence of a filament fully decoupled from the turbulent regime over multi-parsec scales. © ESO, 2016.

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