- ID:
- ivo://CDS.VizieR/J/A+A/496/153
- Title:
- Molecular hydrogen flows along Ori A cloud
- Short Name:
- J/A+A/496/153
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A census of molecular hydrogen flows across the entire Orion A giant molecular cloud is sought. With this paper we aim to associate each flow with its progenitor and associated molecular core, so that the characteristics of the outflows and outflow sources can be established. We present wide-field near-infrared images of Orion A, obtained with the Wide Field Camera, WFCAM, on the United Kingdom Infrared Telescope. Broad-band K and narrow-band H_2_ 1-0S(1) images of a contiguous ~8 square degree region are compared to mid-IR photometry from the Spitzer Space Telescope and (sub)millimetre dust-continuum maps obtained with the MAMBO and SCUBA bolometer arrays. Using previously-published H_2_ images, we also measured proper motions for H_2_ features in 33 outflows, and use these data to help associate flows with existing sources and/or dust cores.
Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/570/A51
- Title:
- Molecular lines in 4 IRCS clumps
- Short Name:
- J/A+A/570/A51
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The earliest phases of high-mass star formation are poorly understood. Aims. Our goal is to determine the physical conditions and kinematic structure of massive starforming cloud clumps. We analyse H_2_O 557GHz line profiles observed with HIFI toward four positions in two infrared-dark cloud clumps. By comparison with ground-based C_17_O, N_2_H^+^, CH_3_OH, and NH_3_ line observations, we constrain the volume density and kinetic temperature of the gas and estimate the column density and abundance of H_2_O and N_2_H^+^. The observed water lines are complex with emission and absorption components. The absorption is redshifted and consistent with a cold envelope, while the emission is interpreted as resulting from proto-stellar outflows. The gas density in the clumps is ~10^7^cm^-3^. The o-H_2_O outflow column density is 0.3-3.0x10^14^cm^-2^. The o-H_2_O absorption column density is between 1.5x10^14^ and 2.6x10^15^cm^-2^ with cold o-H_2_O abundances between 1.5x10^-9^ and 3.1x10^-8^. All clumps have high gas densities (~10^7^cm^-3^) and display infalling gas. Three of the four clumps have outflows. The clumps form an evolutionary sequence as probed by H_2_O N_2_H+, NH_3_, and CH_3_OH. We find that G28-MM is the most evolved, followed by G11-MM and then G28-NH3. The least evolved clump is G11-NH3 which shows no signposts of starformation; G11-NH3 is a high-mass pre-stellar core.
- ID:
- ivo://CDS.VizieR/J/ApJ/780/85
- Title:
- Molecular line study of infrared dark clouds
- Short Name:
- J/ApJ/780/85
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- It is currently assumed that infrared dark clouds (IRDCs) represent the earliest evolutionary stages of high-mass stars (>8M_{sun}_). Submillimeter and millimeter-wave studies performed over the past 15yr show that IRDCs possess a broad variety of properties, and hence a wide range of problems and questions that can be tackled. In this paper, we report an investigation of the molecular composition and chemical processes in two groups of IRDCs. Using the Mopra, APEX, and IRAM radio telescopes over the last four years, we have collected molecular line data for CO, H_2_CO, HNCO, CH_3_CCH, CH_3_OH, CH_3_CHO, CH_3_OCHO, and CH_3_OCH_3_. For all of these species we estimated molecular abundances. We then undertook chemical modeling studies, concentrating on the source IRDC028.34+0.06, and compared observed and modeled abundances. This comparison showed that to reproduce observed abundances of complex organic molecules, a zero-dimensional gas-grain model with constant physical conditions is not sufficient. We achieved greater success with the use of a warm-up model, in which warm-up from 10K to 30K occurs following a cold phase.
- ID:
- ivo://CDS.VizieR/J/A+A/606/A123
- Title:
- Molecular maps of NGC1333
- Short Name:
- J/A+A/606/A123
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Are the initial conditions for clustered star formation the same as for non-clustered star formation? To investigate the initial gas properties in young proto-clusters we carried out a comprehensive and high-sensitivity study of the internal structure, density, temperature, and kinematics of the dense gas content of the NGC1333 region in Perseus, one of the nearest and best studied embedded clusters. The analysis of the gas velocities in the Position-Position-Velocity space reveals an intricate underlying gas organization both in space and velocity. We identified a total of 14 velocity-coherent, (tran-)sonic structures within NGC1333, with similar physical and kinematic properties than those quiescent, star-forming (aka fertile) fibers previously identified in low-mass star-forming clouds. These fibers are arranged in a complex spatial network, build-up the observed total column density, and contain the dense cores and protostars in this cloud. Our results demonstrate that the presence of fibers is not restricted to low-mass clouds but can be extended to regions of increasing mass and complexity. We propose that the observational dichotomy between clustered and non-clustered star-forming regions might be naturally explained by the distinct spatial density of fertile fibers in these environments.
- ID:
- ivo://CDS.VizieR/J/A+A/453/923
- Title:
- Morphologies in the Cepheus Flare region
- Short Name:
- J/A+A/453/923
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- These tables contain the data of the cloud sample on which the study of the relationships between cloud morphology, optical and IR properties, and star formation is based. The sample was defined using the extinction map of the Cepheus Flare region covering ~256 square degrees created from the B band star counts of the USNO-A2.0 catalogue (Cat. <I/252>) with a typical resolution of 3 arcminutes on a 1.5 arcminute grid. Cloud definition and description was carried out using automatized methods. The main table lists the positions, peak extinctions, sizes, morphological parameters and classes, distances, mass estimations, parent cloud complexes, and the number of YSO candidates associated. An additional table with the names of the previously catalogued associated clouds and their references is also available.
- ID:
- ivo://CDS.VizieR/J/A+A/575/A9
- Title:
- M17-SW datacubes in C and CO lines
- Short Name:
- J/A+A/575/A9
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We probe the column densities and masses traced by the ionized [CII] and neutral [CI] atomic carbon with spectrally resolved maps, and compare them to the diffuse and dense molecular gas traced by [CI] and low-J CO lines toward the star-forming region M17 SW. We mapped a 4.1pcx4.7pc region in the [CI] 609{mu}m line using the APEX telescope, as well as the CO isotopologues with the IRAM 30m telescope. Data are analyzed based on velocity channel maps that are 1km/s wide. We correlate their spatial distribution with that of the [CII] map obtained with SOFIA/GREAT. Optically thin approximations were used to estimate the column densities of [CI] and [CII] in each velocity channel.
- ID:
- ivo://CDS.VizieR/J/ApJ/639/227
- Title:
- MSX IRDC candidate catalog
- Short Name:
- J/ApJ/639/227
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We use 8.3{mu}m mid-infrared images acquired with the Midcourse Space Experiment satellite to identify and catalog infrared dark clouds (IRDCs) in the first and fourth quadrants of the Galactic plane. Because IRDCs are seen as dark extinction features against the diffuse Galactic infrared background, we identify them by first determining a model background from the 8.3{mu}m images and then searching for regions of high decremental contrast with respect to this background. IRDC candidates in our catalog are defined by contiguous regions bounded by closed contours of a 2{sigma} decremental contrast threshold. We identify 10,931 candidate IRDCs. For each IRDC, we also catalog cores. These cores, defined as localized regions with at least 40% higher extinction than the cloud's average extinction, are found by iteratively fitting two-dimensional elliptical Gaussian functions to the contrast peaks. We identify 12,774 cores. The catalog contains the position, angular size, orientation, area, peak contrast, peak contrast signal-to-noise, and integrated contrast of the candidate IRDCs and their cores.
- ID:
- ivo://CDS.VizieR/J/AJ/121/2673
- Title:
- 3{mu}m survey of the Chamaeleon I dark cloud
- Short Name:
- J/AJ/121/2673
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We describe an L-band photometric survey of ~0.5deg^2^ of the Chamaeleon I dark cloud. The survey has a completeness limit of L<11.0. Our survey detects 124 sources, including all known pre-main-sequence stars with L<=11. The fraction of sources with near-IR excess emission is 58%+/-4% for K=9-11. Cha I sources have bluer H-K and K-L colors than pre-main-sequence stars in Taurus-Auriga. These sources also have a strong correlation between EW(H{alpha} and K-L. Stars with K-L<=0.6 have weak H{alpha} emission; stars with K-L>=0.6 have strong H{alpha]mission. Because many Cha I sources are heavily reddened, this division between weak emission T Tauri stars and classical T Tauri stars occurs at a redder K-L than in Taurus-Auriga. We acquired L-band photometry of Cha I sources and standard stars using the South Pole Infrared Explorer (SPIREX) during the 1999 March-October observing season. The SPIREX 60cm telescope developed by CARA for observations at the South Pole was equipped with the NOAO/KPNO Abu infrared camera, which includes a first generation 1024x1024 InSb detector array.
- ID:
- ivo://CDS.VizieR/J/A+A/644/A27
- Title:
- Musca APEX 12CO(2-1), 13CO(2-1) and C18O(2-1) data
- Short Name:
- J/A+A/644/A27
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Dense molecular filaments are ubiquituous in the interstellar medium, yet their internal physical conditions and the role of gravity, turbulence, the magnetic field, radiation, and the ambient cloud during their evolution remain debated. We study the kinematics and physical conditions in the Musca filament, the ambient cloud, and the Chamaeleon-Musca complex to constrain the physics of filament formation. We produced CO(2-1) isotopologue maps with the APEX telescope that cut through the Musca filament. We further study a NANTEN2 ^12^CO(1-6>0) map of the full Musca cloud, HI emission of the Chamaeleon-Musca complex, a Planck polarisation map, line radiative tranfer models, Gaia data, and synthetic observations from filament formation simulations. The Musca cloud, with a size of ~3-6pc, contains multiple velocity components. Radiative transfer modelling of the CO emission indicates that the Musca filament consists of a cold (~10K), dense (n_H2_~10^4^cm^-3^) crest, which is best described with a cylindrical geometry. Connected to the crest, a separate gas component at T~15K and n_H2_~10^3^cm^-3^ is found, the so-called strands. The velocity-coherent filament crest has an organised transverse velocity gradient that is linked to the kinematics of the nearby ambient cloud. This velocity gradient has an angle >=30{deg} with respect to the local magnetic field orientation derived from Planck, and the magnitude of the velocity gradient is similar to the transonic linewidth of the filament crest. Studying the large scale kinematics, we find coherence of the asymmetric kinematics from the 50pc HI cloud down to the Musca filament. We also report a strong [C^18^O]/[^13^CO] abundance drop by an order of magnitude from the filament crest to the strands over a distance <0.2pc in a weak ambient far-ultraviolet (FUV) field. The dense Musca filament crest is a long-lived (several crossing times), dynamic structure that can form stars in the near future because of continuous mass accretion replenishing the filament. This mass accretion on the filament appears to be triggered by a HI cloud-cloud collision, which bends the magnetic field around dense filaments. This bending of the magnetic field is then responsible for the observed asymmetric accretion scenario of the Musca filament, which is, for instance, seen as a V-shape in the position-velocity (PV) diagram.
- ID:
- ivo://CDS.VizieR/J/A+A/489/533
- Title:
- M83 volume densities of giant molecular clouds
- Short Name:
- J/A+A/489/533
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using observed GALEX far-ultraviolet (FUV) fluxes and VLA images of the 21-cm HIcolumn densities, along with estimates of the local dust abundances, we measure the volume densities of a sample of actively star-forming giant molecular clouds (GMCs) in the nearby spiral galaxy M83 on a typical resolution scale of 170 pc. Our approach is based on an equilibrium model for the cycle of molecular hydrogen formation on dust grains and photodissociation under the influence of the FUV radiation on the cloud surfaces of GMCs. We find a range of total volume densities on the surface of GMCs in M83, namely 0.1-400cm^-3^ inside R_25_, 0.5-50cm^-3^ outside R_25_. Our data include a number of GMCs in the HI-ring surrounding this galaxy. Finally, we discuss the effects of observational selection, which may bias our results.
