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Start Over Subject diffuse molecular clouds Publisher CDS
1. Catalog of bright diffuse Galactic nebulae
ID:
ivo://CDS.VizieR/VII/231
Title:
Catalog of bright diffuse Galactic nebulae
Short Name:
VII/231
Date:
21 Oct 2021
Publisher:
CDS
Description:
The Catalog of bright diffuse Galactic nebulae was compiled in the frame of a thesis investigating the spatial distribution and the geometrical properties of bright diffuse Galactic nebulae, together with some inquiries into the interstellar absorption problem. It is a mostly complete compilation of the knowledge about bright galactic nebulae around 1945. Global parameters derived for each nebula include a classification, the apparent dimensions, and distance estimations; the Catalog includes also extensive notes, and its bibliography covers the period 1877 to 1941.
2. Catalog of distances to molecular clouds
ID:
ivo://CDS.VizieR/J/ApJ/786/29
Title:
Catalog of distances to molecular clouds
Short Name:
J/ApJ/786/29
Date:
21 Oct 2021
Publisher:
CDS
Description:
Distance measurements to molecular clouds are important but are often made separately for each cloud of interest, employing very different data and techniques. We present a large, homogeneous catalog of distances to molecular clouds, most of which are of unprecedented accuracy. We determine distances using optical photometry of stars along lines of sight toward these clouds, obtained from PanSTARRS-1. We simultaneously infer the reddenings and distances to these stars, tracking the full probability distribution function using a technique presented in Green et al. (2014ApJ...783..114G). We fit these star-by-star measurements using a simple dust screen model to find the distance to each cloud. We thus estimate the distances to almost all of the clouds in the Magnani et al. (1985ApJ...295..402M, MBM) catalog, as well as many other well-studied clouds, including Orion, Perseus, Taurus, Cepheus, Polaris, California, and Monoceros R2, avoiding only the inner Galaxy. Typical statistical uncertainties in the distances are 5%, though the systematic uncertainty stemming from the quality of our stellar models is about 10%. The resulting catalog is the largest catalog of accurate, directly measured distances to molecular clouds. Our distance estimates are generally consistent with available distance estimates from the literature, though in some cases the literature estimates are off by a factor of more than two.
3. Dark dust and single-cloud sightlines in ISM
ID:
ivo://CDS.VizieR/J/A+A/641/A35
Title:
Dark dust and single-cloud sightlines in ISM
Short Name:
J/A+A/641/A35
Date:
21 Oct 2021
Publisher:
CDS
Description:
The precise characteristics of clouds and the nature of dust in the diffuse interstellar medium can only be extracted by inspecting the rare cases of single-cloud sightlines. In our nomenclature such objects are identified by interstellar lines, such as KI, that show at a resolving power of {lambda}{Delta}{lambda}~75000 one dominating Doppler component that accounts for more than half of the observed column density. We searched for such sightlines using high-resolution spectroscopy towards reddened OB stars for which far-UV extinction curves are known. We compiled a sample of 186 spectra, 100 of which were obtained specifically for this project with UVES. In our sample we identified 65 single-cloud sightlines, about half of which were previously unknown. We used the CH/CH^+^ line ratio of our targets to establish whether the sightlines are dominated by warm or cold clouds. We found that CN is detected in all cold (CH/CH^+^>1) clouds, but {is frequently absent} in warm clouds. We inspected the WISE (3-22um) observed emission morphology around our sightlines and excluded a circumstellar nature for the observed dust extinction. We found that most sightlines are dominated by cold clouds that are located far away from the heating source. For 132 stars, we derived the spectral type and the associated spectral type-luminosity distance. We also applied the interstellar CaII distance scale, and compared these two distance estimates with GAIA parallaxes. These distance estimates scatter by ~40%. By comparing spectral type-luminosity distances with those of GAIA, we detected a hidden dust component that amounts to a few mag of extinction for eight sightlines. This dark dust is populated by >~ 1um large grains and predominately appears in the field of the cold interstellar medium.
4. Diffuse ionized gas in the Antennae galaxy
ID:
ivo://CDS.VizieR/J/A+A/611/A95
Title:
Diffuse ionized gas in the Antennae galaxy
Short Name:
J/A+A/611/A95
Date:
21 Oct 2021
Publisher:
CDS
Description:
The Antennae galaxy (NGC 4038/39) is the closest major interacting galaxy system and is therefore often studied as a merger prototype. We present the first comprehensive integral field spectroscopic dataset of this system, observed with the MUSE instrument at the ESO VLT. We cover the two regions in this system which exhibit recent star formation: the central galaxy interaction and a region near the tip of the southern tidal tail. In these fields, we detect HII regions and diffuse ionized gas to unprecedented depth. About 15% of the ionized gas was undetected by previous observing campaigns. This newly detected faint ionized gas is visible everywhere around the central merger, and shows filamentary structure. We estimate diffuse gas fractions of about 60% in the central field and 10% in the southern region. We are able to show that the southern region contains a significantly different population of HII regions, showing fainter luminosities. By comparing HII region luminosities with the HST catalog of young star clusters in the central field, we estimate that there is enough Lyman-continuum leakage in the merger to explain the amount of diffuse ionized gas that we detect. We compare the Lyman-continuum escape fraction of each HII region against emission line ratios that are sensitive to the ionization parameter. While we find no systematic trend between these properties, the most extreme line ratios seem to be strong indicators of density bounded ionization. Extrapolating the Lyman-continuum escape fractions to the southern region, we conclude that simply from the comparison of the young stellar populations to the ionized gas there is no need to invoke other ionization mechanisms than Lyman-continuum leaking HII regions for the diffuse ionized gas in the Antennae.
5. Dust extinction map of the Nessie filament
ID:
ivo://CDS.VizieR/J/A+A/616/A78
Title:
Dust extinction map of the Nessie filament
Short Name:
J/A+A/616/A78
Date:
21 Oct 2021
Publisher:
CDS
Description:
An increasing number of hundred-parsec scale, high line-mass filaments have been detected in the Galaxy. Their evolutionary path, including fragmentation towards star formation, is virtually unknown. We characterize the fragmentation within the Nessie filament, covering size-scales between 0.1-100pc. We also connect the small-scale fragments to the star-forming potential of the cloud. We combine near-infrared data from the VVV survey with mid-infrared GLIMPSE data to derive a high-resolution dust extinction map and apply a wavelet decomposition technique on it to analyze the fragmentation characteristics of the cloud, which are compared with predictions from fragmentation models. We compare the detected objects to those identified in 10 times coarser resolution from ATLASGAL data. We present a high-resolution extinction map of Nessie. We estimate the mean line-mass of Nessie to be 627M_{sun}_/pc and the distance to be 3.5kpc. We find that Nessie shows fragmentation at multiple size scales. The nearest-neighbour separations of the fragments at all scales are within a factor of 2 of the Jeans' length at that scale. However, the relationship between the mean densities of the fragments and their separations is significantly shallower than expected for Jeans' fragmentation. The relationship is similar to the one predicted for a filament that exhibits a Larson-like scaling between size-scale and velocity dispersion; such a scaling may result from turbulent support. Based on the number of YSOs in Nessie, we estimate that the star formation rate is 371M_{sun}_/Myr; similar values result if using the number of dense cores, or the amount of dense gas, as the proxy of star formation. The star formation efficiency is 0.017. These numbers indicate that Nessie's star-forming content is comparable to the Solar neighborhood giant molecular clouds like Orion A.
6. Extinction map of OMC-1
ID:
ivo://CDS.VizieR/J/A+A/533/A38
Title:
Extinction map of OMC-1
Short Name:
J/A+A/533/A38
Date:
21 Oct 2021
Publisher:
CDS
Description:
The Orion Nebula and its associated young stellar cluster are located at the front-side of the optically thick OMC-1 molecular cloud. In order to disentangle the cluster members from background contamination, it is important to know the extinction provided by the OMC-1, which is poorly known, the available measurements yielding contradictory results. Our main goal is to derive a new extinction map of the OMC-1, obtaining information about the structure of the OMC-1 and the Orion Nebula Cluster. The most recent near-infrared catalog of stars is used to study the distribution of reddening across a 0.3deg^2^ area covering the Orion Nebula Cluster. On the basis of the observed (H,H-Ks) diagram, we establish a criterion for disentangling contaminants from bona-fide cluster members. For contaminant stars, interstellar reddenings are estimated by comparison with a synthetic galactic model. A statistical analysis is then performed to consistently account for local extinction, reddening and star-counts analysis. We derive the extinction map of the OMC-1 with angular resolution <5'. We also assemble a sample of candidate cluster members, for which we measure the extinction provided by the nebular environment. These extinction measurements are analyzed similarly to the contaminant sample, and an extinction map of the Orion Nebula is derived. The extinction provided by the OMC-1 is variable on spatial scales of a few arcminutes, while showing a general increase from the outskirts (A_V_~6) to the direction of the Trapezium asterism (A_V_>30). The Orion Nebula extinction map is more irregular and optically thinner, with Av of the order of a few magnitudes. Both maps are consistent with the optical morphology, in particular the Dark Bay to the north-east of the Trapezium. Both maps also show the presence of a north-south high-density ridge, which confirms the filamentary structure of the Orion molecular complex inside which star formation is still taking place.
7. Fluctuations of UV background from GALEX
ID:
ivo://CDS.VizieR/J/A+A/631/A59
Title:
Fluctuations of UV background from GALEX
Short Name:
J/A+A/631/A59
Date:
21 Oct 2021
Publisher:
CDS
Description:
The all sky survey run by the Galaxy Evolution Explorer (GALEX AIS) mapped about 85 % of the Galaxy at ultraviolet (UV) wavelengths and detected the diffuse UV background produced by the scattering of the radiation from OBA stars by interstellar dust grains. Against this background, diffuse weak structures are detected as well as the UV counterparts to nebulae and molecular clouds. To make full profit of the survey, unsupervised and semi-supervised procedures need to be implemented. The main objective of this work is to implement and analyze the results of the method developed by us for the blind detection of ISM features in the GALEX AIS. Most ISM features are detected at very low signal levels (dark filaments, globules) against the already faint UV background. We have defined an index the UV background fluctuations index (or UBF index) to identify areas of the sky where these fluctuations are detected. The algorithm is applied to the images obtained in the FUV (1344-1786{AA}) band since this is less polluted by stellar sources, facilitating the automated detection. The UBF index is shown to be sensitive to the main star forming regions within the Gould's Belt, as well as to some prominent loops like Loop I or the Eridanus and Monogem areas. The catalogue with the UBF index values is made available on-line to the community.
8. GASS HVCs in the Magellanic Leading Arm region
ID:
ivo://CDS.VizieR/J/ApJ/764/74
Title:
GASS HVCs in the Magellanic Leading Arm region
Short Name:
J/ApJ/764/74
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a catalog of high-velocity clouds in the region of the Magellanic Leading Arm. The catalog is based on neutral hydrogen (H I) observations from the Parkes Galactic All-Sky Survey. Excellent spectral resolution allows clouds with narrow-line components to be resolved. The total number of detected clouds is 419. We describe the method of cataloging and present the basic parameters of the clouds. We discuss the general distribution of the high-velocity clouds and classify the clouds based on their morphological type. The presence of a significant number of head-tail clouds and their distribution in the region is discussed in the context of Magellanic System simulations. We suggest that ram-pressure stripping is a more important factor than tidal forces for the morphology and formation of the Magellanic Leading Arm and that different environmental conditions might explain the morphological difference between the Magellanic Leading Arm and Magellanic Stream. We also discuss a newly identified population of clouds that forms the LA IV and a new diffuse bridge-like feature connecting the LA II and III complexes.
9. HI clouds around the Galactic Center
ID:
ivo://CDS.VizieR/J/ApJ/770/L4
Title:
HI clouds around the Galactic Center
Short Name:
J/ApJ/770/L4
Date:
21 Oct 2021
Publisher:
CDS
Description:
We describe a population of small, high-velocity, atomic hydrogen clouds, loops, and filaments found above and below the disk near the Galactic center. The objects have a mean radius of 15pc, velocity widths of ~14km/s, and are observed at |z| heights up to 700pc. The velocity distribution of the clouds shows no signature of Galactic rotation. We propose a scenario where the clouds are associated with an outflow from a central star-forming region at the Galactic center. We discuss the clouds as entrained material traveling at ~200km/s in a Galactic wind.
10. High-velocity clouds from GASS. I.
ID:
ivo://CDS.VizieR/J/ApJS/209/12
Title:
High-velocity clouds from GASS. I.
Short Name:
J/ApJS/209/12
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a catalog of high-velocity clouds (HVCs) from the Galactic All Sky Survey (GASS) of southern sky neutral hydrogen, which has 57mK sensitivity and 1 km/s velocity resolution and was obtained with the Parkes Telescope. Our catalog has been derived from the stray-radiation-corrected second release of GASS. We describe the data and our method of identifying HVCs and analyze the overall properties of the GASS population. We catalog a total of 1693 HVCs at declinations <0{deg}, including 1111 positive velocity HVCs and 582 negative velocity HVCs. Our catalog also includes 295 anomalous velocity clouds (AVCs). The cloud line-widths of our HVC population have a median FWHM of ~19 km/s, which is lower than that found in previous surveys. The completeness of our catalog is above 95% based on comparison with the HIPASS catalog of HVCs upon which we improve by an order of magnitude in spectral resolution. We find 758 new HVCs and AVCs with no HIPASS counterpart. The GASS catalog will shed unprecedented light on the distribution and kinematic structure of southern sky HVCs, as well as delve further into the cloud populations that make up the anomalous velocity gas of the Milky Way.

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