- ID:
- ivo://CDS.VizieR/J/MNRAS/409/29
- Title:
- Methanol line formation in outflow sources
- Short Name:
- J/MNRAS/409/29
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the first calculations of the spectrum of methanol, arising in shock waves in molecular outflows. The small grid of shock wave models that we have computed incorporates the results of very recent computations of the rate coefficients for the collisional excitation of methanol by ortho- and para-H2 and by He. The two strongest transitions, one of A- and the other of E-type methanol, are masers that have been observed in a Class I methanol maser source, which is believed to be related to a molecular outflow. The same collisional propensities that give rise to population inversion and maser action can, in other transitions, lead to population anti-inversion and the lines appearing in absorption against the cosmic background radiation. We attempted to model specifically the outflow source L1157 B1, in which transitions of methanol have been observed recently by means of the Herschel satellite. Comparison with the predictions of the shock wave models is complicated by uncertainty in the value of the beam filling factor that should be adopted.
Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/J/MNRAS/444/566
- Title:
- Methanol maser associated outflows
- Short Name:
- J/MNRAS/444/566
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have selected the positions of 54 6.7GHz methanol masers from the Methanol Multibeam Survey catalogue, covering a range of longitudes between 20{deg} and 34{deg} of the Galactic plane. These positions were mapped in the J=3-2 transition of both the ^13^CO and C^18^O lines. A total of 58 ^13^CO emission peaks are found in the vicinity of these maser positions. We search for outflows around all ^13^CO peaks, and find evidence for high-velocity gas in all cases, spatially resolving the red and blue outflow lobes in 55 cases. Of these sources, 44 have resolved kinematic distances, and are closely associated with the 6.7GHz masers, a subset referred to as Methanol Maser Associated Outflows (MMAOs). We calculate the masses of the clumps associated with each peak using 870{mu}m continuum emission from the ATLASGAL survey. A strong correlation is seen between the clump mass and both outflow mass and mechanical force, lending support to models in which accretion is strongly linked to outflow. We find that the scaling law between outflow activity and clump masses observed for low-mass objects, is also followed by the MMAOs in this study, indicating a commonality in the formation processes of low-mass and high-mass stars.
- ID:
- ivo://CDS.VizieR/J/ApJS/215/25
- Title:
- Methyl formate (HCOOCH_3_) observations
- Short Name:
- J/ApJS/215/25
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have surveyed a sample of massive star-forming regions located over a range of distances from the Galactic center for methyl formate, HCOOCH_3_, and its isotopologues H^13^COOCH_3_ and HCOO^13^CH_3_. The observations were carried out with the APEX telescope in the frequency range 283.4-287.4GHz. Based on the APEX observations, we report tentative detections of the ^13^C-methyl formate isotopologue HCOO^13^CH_3_toward the following four massive star-forming regions: Sgr B2(N-LMH), NGC 6334 IRS 1, W51 e2, and G19.61-0.23. In addition, we have used the 1mm ALMA science verification observations of Orion-KL and confirm the detection of the ^13^C-methyl formate species in Orion-KL and image its spatial distribution. Our analysis shows that the ^12^C/^13^C isotope ratio in methyl formate toward the Orion-KL Compact Ridge and Hot Core-SW components (68.4+/-10.1 and 71.4+/-7.8, respectively) are, for both the ^13^C-methyl formate isotopologues, commensurate with the average ^12^C/^13^C ratio of CO derived toward Orion-KL. Likewise, regarding the other sources, our results are consistent with the ^12^C/^13^C in CO. We also report the spectroscopic characterization, which includes a complete partition function, of the complex H^13^COOCH_3_ and HCOO^13^CH_3_species. New spectroscopic data for both isotopomers H^13^COOCH_3_and HCOO^13^CH_3_, presented in this study, have made it possible to measure this fundamentally important isotope ratio in a large organic molecule for the first time.
- ID:
- ivo://CDS.VizieR/J/A+A/587/L4
- Title:
- Methyl isocyanate in Orion
- Short Name:
- J/A+A/587/L4
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The recent analysis of the composition of the frozen surface of comet 67P/Churyumov-Gerasimenko has revealed a significant number of complex organic molecules. Methyl isocyanate (CH_3_NCO) is one of the more abundant species detected on the comet surface. In this work we report extensive characterization of its rotational spectrum resulting in a list of 1269 confidently assigned laboratory lines and its detection in space towards the Orion clouds where 399 lines of the molecule have been unambiguously identified. We find that the limited mm-wave laboratory data reported prior to our work require some revision. The abundance of CH_3_NCO in Orion is only a factor of ten below those of HNCO and CH_3_CN. Unlike the molecular abundances in the coma of comets, which correlate with those of warm molecular clouds, molecular abundances in the gas phase in Orion are only weakly correlated with those measured on the comet surface. We also compare our abundances wit those derived recently for this molecule towards Sgr B2 (Halfen et al., 2015ApJ...812L...5H). A more accurate abundance of CH_3_NCO is provided for this cloud based on our extensive laboratory work.
- ID:
- ivo://CDS.VizieR/J/A+A/578/A63
- Title:
- MHD shock code mhd_vode
- Short Name:
- J/A+A/578/A63
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The planar MHD shock code_mhd vode has been developed in order to simulate both "continuous" (C) type shock waves and "jump" (J) type shock waves in the interstellar medium. The physical and chemical state of the gas in steady-state may also be computed and used as input to a shock wave model. The code is written principally in FORTRAN 90, although some routines remain in FORTRAN 77. The documented program and its input data are described and provided as supplementary material, and the results of exemplary test runs are presented. Our intention is to enable the interested user to run the code for any sensible parameter set and to comprehend the results. With applications to molecular outflow sources in mind, we have computed, and are making available as supplementary material, integrated atomic and molecular line intensities for grids of C- and J-type models; these computations are summarized in the Appendices.
526. M31 Herschel images
- ID:
- ivo://CDS.VizieR/J/A+A/567/A71
- Title:
- M31 Herschel images
- Short Name:
- J/A+A/567/A71
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Dust and stars play a complex game of interactions in the interstellar medium and around young stars. The imprints of these processes are visible in scaling relations between stellar characteristics, star formation parameters, and dust properties. Aims. In the present work, we aim to examine dust scaling relations on a sub-kpc resolution in the Andromeda galaxy (M31). The goal is to investigate the properties of M31 on both a global and local scale and compare them to other galaxies of the local universe. Methods. New Herschel observations are combined with available data from GALEX, SDSS, WISE, and Spitzer to construct a dataset covering UV to submm wavelengths. All images were brought to the beam size and pixel grid of the SPIRE 500um frame. This divides M31 in 22437 pixels of 36 arcseconds in size on the sky, corresponding to physical regions of 137x608pc in the galaxy's disk. A panchromatic spectral energy distribution was modelled for each pixel and maps of the physical quantities were constructed. Several scaling relations were investigated, focussing on the interactions of dust with starlight. Results. We find, on a sub-kpc scale, strong correlations between Mdust/M* and NUV-r, and between Mdust/M* and mu* (the stellar mass surface density). Striking similarities with corresponding relations based on integrated galaxies are found. We decompose M31 in four macro-regions based on their FIR morphology; the bulge, inner disk, star forming ring, and the outer disk region. In the scaling relations, all regions closely follow the galaxy-scale average trends and behave like galaxies of different morphological types. The specific star formation characteristics we derive for these macro-regions give strong hints of an inside-out formation of the bulge-disk geometry, as well as an internal downsizing process. Within each macro-region, however, a great diversity in individual micro-regions is found, regardless of the properties of the macro-regions. Furthermore, we confirm that dust in the bulge of M31 is heated only by the old stellar populations. Conclusions. In general, the local dust scaling relations indicate that the dust content in M31 is maintained by a subtle interplay of past and present star formation. The similarity with galaxy-based relations strongly suggests that they are in situ correlations, with underlying processes that must be local in nature.
527. MHO Catalogue
- ID:
- ivo://CDS.VizieR/J/A+A/511/A24
- Title:
- MHO Catalogue
- Short Name:
- J/A+A/511/A24
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a catalogue of Molecular Hydrogen emission-line Objects (MHOs) in outflows from young stars, most of which are deeply embedded. All objects are identified in the near-infrared lines of molecular hydrogen, all reside in the Milky Way, and all are associated with jets or molecular outflows. Objects in both low and high-mass star forming regions are included. This catalogue complements the existing database of Herbig-Haro objects; indeed, for completeness, HH objects that are detected in H_2_ emission are included in the MHO catalogue.
- ID:
- ivo://CDS.VizieR/J/A+A/636/A16
- Title:
- M43, Horsehead, MonR2, M17SW [CII]158um spectra
- Short Name:
- J/A+A/636/A16
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The [CII] 158um FIR fine-structure line is one of the most important cooling lines of the star-forming ISM. It is used as a tracer of star formation efficiency in external galaxies and to study feedback effects in parental clouds. High spectral resolution observations have shown complex structures in the line profiles of the [CII] emission. To determine whether the complex profiles observed in [^12^CII] are due to individual velocity components along the line-of-sight or due to self-absorption, one has to compare the [^12^CII] and isotopic [^13^CII] line profiles. Deep integrations with the SOFIA/upGREAT 7-pixel array receiver in the sources M43, Horsehead PDR, Monoceros R2 and M17 SW allow to detect with high S/N the optically thin [^13^CII] and simultaneously the [^12^CII] emission lines. We first derive the [^12^CII] optical depth and the [CII] column density from a single component model. However, the complex line profiles observed require a double layer model with an emitting background and an absorbing foreground. A multi-component velocity fit allows to derive the physical conditions of the [CII] gas: column density and excitation temperature. We find moderate to high [^12^CII] optical depths in all four sources, and self-absorption of [^12^CII] in Mon R2 and M17 SW. The high column density of the warm background emission corresponds to an equivalent Av of up to 41mag. The foreground absorption requires substantial column densities of cold and dense [CII] gas, with an equivalent Av ranging up to about 13mag. The column density of the warm background material requires multiple PDR surfaces stacked along the line of sight and in velocity. The substantial column density of dense and cold foreground [CII] gas detected in absorption cannot be explained with any known scenario and we can only speculate about its origin.
- ID:
- ivo://CDS.VizieR/J/ApJ/844/38
- Title:
- MHOs toward 22 regions with H2 fluxes
- Short Name:
- J/ApJ/844/38
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of a narrow-band near-infrared imaging survey for Molecular Hydrogen emission-line Objects (MHOs) toward 26 regions containing high-mass protostellar candidates and massive molecular outflows. We have detected a total of 236 MHOs, 156 of which are new detections, in 22 out of the 26 regions. We use H_2_2.12{mu}m/H_2_2.25{mu}m flux ratios, together with morphology, to separate the signatures of fluorescence associated with photo- dissociation regions (PDRs) from shocks associated with outflows in order to identify the MHOs. PDRs have typical low flux ratios of ~1.5-3, while the vast majority of MHOs display flux ratios typical of C-type shocks (~6-20). A few MHOs exhibit flux ratios consistent with expected values for J-type shocks (~3-4), but these are located in regions that may be contaminated with fluorescent emission. Some previously reported MHOs have low flux ratios, and are likely parts of PDRs rather than shocks indicative of outflows. We identify a total of 36 outflows across the 22 target regions where MHOs were detected. In over half these regions, MHO arrangements and fluorescent structures trace features present in CO outflow maps, suggesting that the CO emission traces a combination of dynamical effects, which may include gas entrained in expanding PDRs as well as bipolar outflows. Where possible, we link MHO complexes to distinct outflows and identify candidate driving sources.
- ID:
- ivo://CDS.VizieR/J/A+A/558/A6
- Title:
- Microwave spectrum of 2-pentynenitrile (C2H5CCCN)
- Short Name:
- J/A+A/558/A6
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- New radiotelescopes, such as the very sensitive ALMA, will enable the detection of interstellar molecules in much lower concentrations than previously possible. A successful identification of an interstellar molecule requires that laboratory microwave and millimeter-wave spectra are investigated. Several cyanopolyynes and alkynylcarbonitriles have already been detected in the interstellar medium (ISM). Cyanoacetylene (HCCCN) is abundant in the ISM and its methyl derivative, 2-butynenitrile (CH3CCCN), is also present. The next derivative, ethyl cyanoacetylene, (2-pentynenitrile C_2_H_5_CCCN) may also be present in interstellar space. We report the rotational spectrum of the ethyl cyanoacetylene (C_2_H_5_CCCN). This is hoped to facilitate identifying gaseous ethyl cyanoacetylene in the ISM.
