- ID:
- ivo://CDS.VizieR/J/A+A/552/A40
- Title:
- MSX high-contrast IRDCs with NH_3_
- Short Name:
- J/A+A/552/A40
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Despite increasing research in massive star formation, little is known about its earliest stages. Infrared Dark Clouds (IRDCs) are cold, dense and massive enough to harbour the sites of future high-mass star formation. But up to now, mainly small samples have been observed and analysed. To understand the physical conditions during the early stages of high-mass star formation, it is necessary to learn more about the physical conditions and stability in relatively unevolved IRDCs. Thus, for characterising IRDCs studies of large samples are needed. We investigate a complete sample of 220 northern hemisphere high-contrast IRDCs using the ammonia (1,1)- and (2,2)-inversion transitions. We detected ammonia (1,1)-inversion transition lines in 109 of our IRDC candidates. Using the data we were able to study the physical conditions within the star-forming regions statistically. We compared them with the conditions in more evolved regions which have been observed in the same fashion as our sample sources. Our results show that IRDCs have, on average, rotation temperatures of 15K, are turbulent (with line width FWHMs around 2km/s), have ammonia column densities on the order of 10^14^cm^-2^ and molecular hydrogen column densities on the order of 10^22^cm^-2^. Their virial masses are between 100 and a few 1000M_{sun}_. The comparison of bulk kinetic and potential energies indicate that the sources are close to virial equilibrium. IRDCs are on average cooler and less turbulent than a comparison sample of high-mass protostellar objects, and have lower ammonia column densities. Virial parameters indicate that the majority of IRDCs are currently stable, but are expected to collapse in the future.
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Search Results
- 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/126/1423
- Title:
- MSX 8.3um fluxes of star-forming regions
- Short Name:
- J/AJ/126/1423
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have imaged seven nearby star-forming regions, the Rosette Nebula, the Orion Nebula, W3, the Pleiades, G300.2-16.8, S263, and G159.6-18.5, with the Spatial Infrared Imaging Telescope on the Midcourse Space Experiment (MSX) satellite at 18" resolution at 8.3, 12.1, 14.7, and 21.3{mu}m. The large angular scale of the regions imaged (~7.2-50deg^2^) makes these data unique in terms of the combination of size and resolution. In addition to the star-forming regions, two cirrus-free fields (MSXBG 160 and MSXBG 161) and a field near the south Galactic pole (MSXBG 239) were also imaged. Point sources have been extracted from each region, resulting in the identification over 500 new sources (i.e., no identified counterparts at other wavelengths), as well as over 1300 with prior identifications. The extended emission from the star-forming regions is described, and prominent structures are identified, particularly in W3 and Orion. The Rosette Nebula is discussed in detail. The bulk of the mid-infrared emission is consistent with that of photon-dominated regions, including the elephant trunk complex. The central clump, however, and a line of site toward the northern edge of the cavity show significantly redder colors than the rest of the Rosette complex.
- ID:
- ivo://CDS.VizieR/J/ApJ/833/85
- Title:
- Multi-wavelength analysis of the MIR bubble N37
- Short Name:
- J/ApJ/833/85
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have performed a multi-wavelength analysis of a mid-infrared (MIR) bubble N37 and its surrounding environment. The selected 15'x15' area around the bubble contains two molecular clouds (N37 cloud; V_lsr_~37-43km/s, and C25.29+0.31; V_lsr_~43-48km/s) along the line of sight. A total of seven OB stars are identified toward the bubble N37 using photometric criteria, and two of them are spectroscopically confirmed as O9V and B0V stars. The spectro-photometric distances of these two sources confirm their physical association with the bubble. The O9V star appears to be the primary ionizing source of the region, which is also in agreement with the desired Lyman continuum flux analysis estimated from the 20cm data. The presence of the expanding HII region is revealed in the N37 cloud, which could be responsible for the MIR bubble. Using the ^13^CO line data and photometric data, several cold molecular condensations as well as clusters of young stellar objects (YSOs) are identified in the N37 cloud, revealing ongoing star formation (SF) activities. However, the analysis of ages of YSOs and the dynamical age of the HII region do not support the origin of SF due to the influence of OB stars. The position-velocity analysis of ^13^CO data reveals that two molecular clouds are interconnected by a bridge-like structure, favoring the onset of a cloud-cloud collision process. The SF activities (i.e., the formation of YSO clusters and OB stars) in the N37 cloud are possibly influenced by the cloud-cloud collision.
- ID:
- ivo://CDS.VizieR/J/ApJS/252/21
- Title:
- Multiwavelength survey of WR stars in LMC
- Short Name:
- J/ApJS/252/21
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Surveys of Wolf-Rayet (WR) stars in the Large Magellanic Cloud (LMC) have yielded a fairly complete catalog of 154 known stars. We have conducted a comprehensive, multiwavelength study of the interstellar/circumstellar environments of WR stars, using the Magellanic Cloud Emission Line Survey images in the H{alpha}, [OIII], and [SII] lines; Spitzer Space Telescope 8 and 24{mu}m images; Blanco 4m Telescope H{alpha} CCD images; and Australian Telescope Compact Array + Parkes Telescope HI data cube of the LMC. We have also examined whether the WR stars are in OB associations, classified the HII environments of WR stars, and used this information to qualitatively assess the WR stars' evolutionary stages. The 30 Dor giant HII region has active star formation and hosts young massive clusters, thus we have made statistical analyses for 30 Dor and the rest of the LMC both separately and altogether. Due to the presence of massive young clusters, the WR population in 30 Dor is quite different from that from elsewhere in the LMC. We find small bubbles (<50pc diameter) around ~12% of WR stars in the LMC, most of which are WN stars and not in OB associations. The scarcity of small WR bubbles is discussed. Spectroscopic analyses of abundances are needed to determine whether the small WR bubbles contain interstellar medium or circumstellar medium. Implications of the statistics of interstellar environments and OB associations around WR stars are discussed. Multiwavelength images of each LMC WR star are presented.
- ID:
- ivo://CDS.VizieR/J/AJ/130/1763
- Title:
- 11.7{mu}m point sources in Orion
- Short Name:
- J/AJ/130/1763
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a new 11.7{mu}m mosaic image of the inner Orion Nebula obtained with the T-ReCS instrument on Gemini South. The map covers 2.7'x1.6', with a diffraction-limited spatial resolution of 0.35"; it includes the BN/KL region, the Trapezium, and OMC-1 South. Excluding BN/KL, we detect 91 thermal-IR point sources, with 27 known proplyds and over 30 "naked" stars showing no extended structure in Hubble Space Telescope (HST) images.
- 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/641/A17
- Title:
- Musca APEX 12CO(2-1), 12CO(3-2) & 12CO(4-3) data
- Short Name:
- J/A+A/641/A17
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Observations with the Herschel Space Telescope have established that most star forming gas is organised in filaments, a finding that is supported by numerical simulations of the supersonic interstellar medium (ISM) where dense filamentary structures are ubiquitous. We aim to understand the formation of these dense structures by performing observations covering the ^12^CO(4-3), ^12^CO(3-2), and various CO(2-1) isotopologue lines of the Musca filament, using the APEX telescope. The observed CO intensities and line ratios cannot be explained by PDR (photodissociation region) emission because of the low ambient far-UV field that is strongly constrained by the non-detections of the [CII] line at 158um and the [OI] line at 63um, observed with the upGREAT receiver on SOFIA, as well as a weak [CI] 609um line detected with APEX. We propose that the observations are consistent with a scenario in which shock excitation gives rise to warm and dense gas close to the highest column density regions in the Musca filament. Using shock models, we find that the CO observations can be consistent with excitation by J-type low-velocity shocks. A qualitative comparison of the observed CO spectra with synthetic observations of dynamic filament formation simulations shows a good agreement with the signature of a filament accretion shock that forms a cold and dense filament from a converging flow. The Musca filament is thus found to be dense molecular post-shock gas. Filament accretion shocks that dissipate the supersonic kinetic energy of converging flows in the ISM may thus play a prominent role in the evolution of cold and dense filamentary structures.
- ID:
- ivo://CDS.VizieR/J/A+A/510/A54
- Title:
- NaI and CaII interstellar absorption
- Short Name:
- J/A+A/510/A54
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present new high resolution (R>50000) absorption measurements of the NaI doublet (5889-5895{AA}) along 482 nearby sight-lines, in addition to 807 new measurements of the CaII K (3933{AA}) absorption line. We have combined these new data with previously reported measurements to produce a catalog of absorptions towards a total of 1857 early-type stars located within 800pc of the Sun. Using these data we have determined the approximate 3-dimensional spatial distribution of neutral and partly ionized interstellar gas density within a distance-cube of 300pc from the Sun.
460. NaI in Local Bubble
- ID:
- ivo://CDS.VizieR/J/A+A/346/785
- Title:
- NaI in Local Bubble
- Short Name:
- J/A+A/346/785
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present preliminary results form a long-term program of mapping the neutral absorption characteristics of the local interstellar medium, taking advantage of Hipparcos stellar distances. Equivalent width of the NaI D-line doublet at 5890{AA} are presented for the lines-of-sight towards some 143 new target stars lying within 300pc of the Sun.
