- ID:
- ivo://CDS.VizieR/J/A+A/607/A39
- Title:
- 7 FU Orionis-type stars CO spectral cubes
- Short Name:
- J/A+A/607/A39
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- FU Orionis-type objects are pre-main sequence, low-mass stars with large outbursts in visible light that last for several years or decades. They are thought to represent an evolutionary phase during the life of every young star when accretion from the circumstellar disk is enhanced during recurring time periods. These outbursts are able to rapidly build up the star while affecting the physical conditions inside the circumstellar disk and thus the ongoing or future planet formation. In many models, infall from a circumstellar envelope seems to be necessary to trigger the outbursts. We characterise the morphology and the physical parameters of the circumstellar material around FU Orionis-type stars using the emission of millimetre-wavelength molecular tracers. The high-spatial-resolution study provides insight into the evolutionary state of the objects, the distribution of parameters in the envelopes and the physical processes forming the environment of these stars. We observed the J=1-0 rotational transition of ^13^CO and C^18^O towards eight northern FU Orionis-type stars (V1057 Cyg, V1515 Cyg, V2492 Cyg, V2493 Cyg, V1735 Cyg, V733 Cep, RNO 1B and RNO 1C) and determine the spatial and velocity structure of the circumstellar gas on a scale of a few thousand AU. We derive temperatures and envelope masses and discuss the kinematics of the circumstellar material.
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/527/A135
- Title:
- Gas dynamics in Massive Dense Cores in Cygnus-X
- Short Name:
- J/A+A/527/A135
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We studied the kinematic properties of dense gas surrounding massive protostars in a sample of five Massive Dense Cores (MDCs) in Cygnus-X. The aim is to investigate whether turbulent support plays a major role in stabilizing the cores against a rapid fragmentation into Jeans-mass objects. Alternatively the observed kinematics could indicate a high level of dynamics suggesting that the cores are actually not in equilibrium and dynamical processes could be the main driver to build up the final stellar masses.
- ID:
- ivo://CDS.VizieR/J/ApJ/899/158
- Title:
- Gas structure comparison; NGC 253 and Milky Way
- Short Name:
- J/ApJ/899/158
- Date:
- 14 Mar 2022 07:10:20
- Publisher:
- CDS
- Description:
- We compare molecular gas properties in the starbursting center of NGC253 and the Milky Way Galactic center (GC) on scales of ~1-100pc using dendrograms and resolution-, area-, and noise-matched data sets in CO(1-0) and CO(3-2). We find that the size-line width relations in NGC253 and the GC have similar slope, but NGC253 has larger line widths by factors of ~2-3. The {sigma}2/R dependency on column density shows that, in the GC, on scales of 10-100pc the kinematics of gas over N>3x1021/cm^2^ are compatible with gravitationally bound structures. In NGC253 this is only the case for column densities N>3x1022/cm^2^. The increased line widths in NGC253 originate in the lower column density gas. This high velocity dispersion, not gravitationally self-bound gas, is likely in transient structures created by the combination of high average densities and feedback in the starburst. The high densities turn the gas molecular throughout the volume of the starburst, and the injection of energy and momentum by feedback significantly increases the velocity dispersion at a given spatial scale over what is observed in the GC.
- ID:
- ivo://CDS.VizieR/J/A+A/633/A14
- Title:
- GaussPy+ decomposition of Galactic Ring Survey
- Short Name:
- J/A+A/633/A14
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The analysis of large molecular line surveys of the Galactic plane is essential for our understanding of the gas kinematics on Galactic scales and, in particular, its link with the formation and evolution of dense structures in the interstellar medium. An approximation of the emission peaks with Gaussian functions allows for an efficient and straightforward extraction of useful physical information contained in the shape and Doppler-shifted frequency of the emission lines contained in these enormous data sets. In this work, we present an overview and the first results of a Gaussian decomposition of the entire Galactic Ring Survey (GRS) ^13^CO (1-0) data that consists of about 2.3 million spectra. We performed the decomposition with the fully automated GaussPy+ algorithm and fitted about 4.6 million Gaussian components to the GRS spectra. These decomposition results enable novel and unexplored ways to interpret and study the gas velocity structure. We discuss the statistics of the fit components and relations between the fitted intensities, velocity centroids, and velocity dispersions. We find that the magnitude of the velocity dispersion values increase towards the inner Galaxy and around the Galactic midplane, which we speculate is partly due to the influence of the Galactic bar and regions with higher non-thermal motions located in the midplane, respectively. We also used our decomposition results to infer global properties of the gas emission and find that the number of fit components used per spectrum is indicative of the amount of structure along the line of sight. We find that the emission lines from regions located on the far side of the Galaxy show increased velocity dispersion values, which are likely due to beam averaging effects. We demonstrate how this trend has the potential to aid in characterising Galactic structure by disentangling emission that belongs to the nearby Aquila Rift molecular cloud from emission that is more likely associated with the Perseus and Outer spiral arms. With this work, we also make our entire decomposition results available.
- ID:
- ivo://CDS.VizieR/J/A+A/619/A140
- Title:
- g'G'Ag-CH3CH2CHOHCH2OH transition frequencies
- Short Name:
- J/A+A/619/A140
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The continuously enhanced sensitivity of radioastronomical observations allows the detection of increasingly complex organic molecules. These systems often exist in a large number of isomers leading to very congested spectra. We explore the conformational space of 1,2-butanediol and provide sets of spectroscopic parameters to facilitate searches for this molecule at millimeter wavelengths. We recorded the rotational spectrum of 1,2-butanediol in the 59.6-103.6GHz frequency region (5.03-2.89mm) using a free-jet millimeter-wave absorption spectrometer, and we analyzed the properties of 24 isomers with quantum chemical calculations. Selected measured transition lines were then searched on publicly available ALMA Band 3 data on IRAS 16293-2422 B. We assigned the spectra of six conformers, namely aG'Ag, gG'Aa, g'G'Ag, aG'G'g, aG'Gg, and g'GAa, to yield the rotational constants and centrifugal distortion constants up to the fourth or sixth order. The most intense signal belong to the aG'Ag species, that is the global minimum. Search for the corresponding 30_x,30_-29_x,29_ transition lines toward IRAS 16293-2422 B was unsuccessful. Our present data will be helpful for identifying 1,2-butanediol at millimeter wavelengths with radio telescope arrays. Among all possible conformers, first searches should be focused on the aG'Ag conformers in the 400-800GHz frequency spectral range.
- ID:
- ivo://CDS.VizieR/J/ApJ/846/160
- Title:
- 6.7GHz Class II methanol maser survey
- Short Name:
- J/ApJ/846/160
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We performed a systematic 6.7GHz Class II methanol maser survey using the Shanghai Tianma Radio Telescope toward targets selected from the all-sky Wide-Field Infrared Survey Explorer (WISE) point catalog. In this paper, we report the results from the survey of those at high Galactic latitudes, i.e., |b|>2{deg}. Of 1473 selected WISE point sources at high latitude, 17 point positions that were actually associated with 12 sources were detected with maser emission, reflecting the rarity (1%-2%) of methanol masers in the region away from the Galactic plane. Out of the 12 sources, 3 are detected for the first time. The spectral energy distribution at infrared bands shows that these new detected masers occur in the massive star-forming regions. Compared to previous detections, the methanol maser changes significantly in both spectral profiles and flux densities. The infrared WISE images show that almost all of these masers are located in the positions of the bright WISE point sources. Compared to the methanol masers at the Galactic plane, these high-latitude methanol masers provide good tracers for investigating the physics and kinematics around massive young stellar objects, because they are believed to be less affected by the surrounding cluster environment.
- ID:
- ivo://CDS.VizieR/J/A+A/653/A108
- Title:
- Globules and pillars in Cygnus X
- Short Name:
- J/A+A/653/A108
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- IRAS 20319+3958 in Cygnus X South is a rare example of a free-floating globule (mass ~240M_{sun}_, length ~1.5pc) with an internal HII region created by the stellar feedback of embedded intermediate-mass stars, in particular, one Herbig Be star. In Schneider et al. (2012A&A...542L..18S) and Djupvik et al. (2017A&A...599A..37D, Cat. J/A+A/599/A37), we proposed that the emission of the far-infrared (FIR) lines of [CII] at 158um and [OI] at 145um in the globule head are mostly due to an internal photodissociation region (PDR). Here, we present a Herschel/HIFI [CII] 158um map of the whole globule and a large set of other FIR lines (mid-to high-J CO lines observed with Herschel/PACS and SPIRE, the [OI] 63um line and the ^12^CO 16->15 line observed with upGREAT on SOFIA), covering the globule head and partly a position in the tail. The [CII] map revealed that the whole globule is probably rotating. Highly collimated, high-velocity [CII] emission is detected close to the Herbig Be star. We performed a PDR analysis using the KOSMA-{tau}PDR code for one position in the head and one in the tail. The observed FIR lines in the head can be reproduced with a two-component model: an extended, non-clumpy outer PDR shell and a clumpy, dense, and thin inner PDR layer, representing the interface between the HII region cavity and the external PDR. The modelled internal UV field of ~2500Go is similar to what we obtained from the Herschel FIR fluxes, but lower than what we estimated from the census of the embedded stars. External illumination from the ~30pc distant Cyg OB2 cluster, producing an UV field of ~150-600Go as an upper limit, is responsible for most of the [CII] emission. For the tail, we modelled the emission with a non-clumpy component, exposed to a UV-field of around 140Go.
- ID:
- ivo://CDS.VizieR/J/A+A/635/A4
- Title:
- HCN-to-HNC intensity ratio
- Short Name:
- J/A+A/635/A4
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The gas kinetic temperature (TK) determines the physical and chemical evolution of the interstellar medium (ISM). However, obtaining reliable TK estimates usually requires expensive observations including the combination of multi-line analysis and dedicated radiative transfer calculations. This work explores the use of HCN and HNC observations, and particularly the I(HCN)-to-I(HNC) intensity ratio (I(HCN)/I(HNC)) of their J=1-0 lines, as direct probe of the gas kinetic temperature in the molecular ISM. We obtained a new set of large-scale observations of the HCN and HNC (1-0) lines throughout the Integral Shape Filament (ISF) in Orion. In combination with ancillary gas and dust temperature measurements, we find a systematic temperature dependence of the observed I(HCN)-to-I(HNC) intensity ratio throughout our maps. Additional comparisons with chemical models demonstrate that these observed I(HCN)/I(HNC) variations are driven by the effective destruction and isomerization mechanisms of HNC under low-energy barriers. The observed variations of I(HCN)/I(HNC) with TK can be described with a two-part linear function. This empirical calibration is then used to create a temperature map of the entire ISF. Comparisons with similar dust temperature measurements in this cloud, as well as in other regions and galactic surveys, validate this simple technique for obtaining direct estimates of the gas kinetic temperature in a wide range of physical conditions and scales with an optimal working range between 15K<TK<=40K. Both observations and models demonstrate the strong sensitivity of the I(HCN)/I(HNC) ratio to the gas kinetic temperature. Since these lines are easily obtained in observations of local and extragalactic sources, our results highlight the potential use of this observable as new chemical thermometer for the ISM.
- ID:
- ivo://CDS.VizieR/J/ApJ/779/119
- Title:
- HCOOCH_2_D detection in Orion KL
- Short Name:
- J/ApJ/779/119
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Based on new measurements carried out in the laboratory from 0.77 to 1.2THz and on a line-frequency analysis of these new data, along with previously published data, we build a line list for HCOOCH_2_D that leads to its first detection in the Orion KL nebula. The observed lines, both in space and in the laboratory, involve the cis D-in-plane and trans D-out-of-plane conformations of HCOOCH_2_D and the two tunneling states arising from the large-amplitude motion connecting the two trans configurations. The model used in the line position calculation accounts for both cis and trans conformations, as well as the large-amplitude motion.
- ID:
- ivo://CDS.VizieR/J/A+A/606/A102
- Title:
- Herschel cold clumps CO survey
- Short Name:
- J/A+A/606/A102
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The physical state of cold cloud clumps has a great impact on the process and efficiency of star formation and the masses of the forming stars inside these objects. The sub-millimetre survey of the Planck space observatory and the far-infrared follow-up mapping of the Herschel space telescope provide an unbiased, large sample of these cold objects. We have observed ^12^CO(1-0) and ^13^CO(1-0) emission in 35 high-density clumps in 26 Herschel fields sampling different environments in the Galaxy. We derive the physical properties of the objects and estimate their gravitational stability. The densities and temperatures of the clumps were calculated from both the dust continuum and the molecular line data. Kinematic distances were derived using ^13^CO(1-0) line velocities to verify previous distance estimates and the sizes and masses of the objects were calculated by fitting 2D Gaussian functions to their optical depth distribution maps on 250um. The masses and virial masses were estimated assuming an upper and lower limit on the kinetic temperatures and considering uncertainties due to distance limitations.
