- ID:
- ivo://CDS.VizieR/J/AJ/138/1380
- Title:
- Dust clumps in the Galactic Plane
- Short Name:
- J/AJ/138/1380
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present imaging observations of continuum emission from interstellar dust at 850 and 1200um of a section of the Galactic Plane covering 2deg^2^ centered at l=44{deg}. Complementary jiggle-mapping and fast-scanning techniques were used, respectively, at these two wavelengths. The mapped area includes the well-known star formation regions W49 and G45.1/45.5. Using an automated clump-finding routine, we identify 132 compact 850um emission features within the region above a completeness level of about 200mJy/beam. The positions of the latter objects were used to determine fluxes from the 1200um image. Spectral line data were subsequently obtained with the same observing beamwidth as at 850um for almost half of the objects; these were either imaged in the ^13^CO (3-2) line, or basic characteristics determined using the ^12^CO (3-2) transition. We use these data, supplemented by existing ^13^CO (1-0) and HI survey data, to determine distances and hence derive masses for the dust clump ensemble, assuming a uniform dust temperature of 15K. From these data we find that the number-mass relationship for clumps in the field is similar to that found for individual star-forming regions.
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- ID:
- ivo://CDS.VizieR/J/A+A/502/845
- Title:
- Dust coagulation in molecular clouds
- Short Name:
- J/A+A/502/845
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The cores in molecular clouds are the densest and coldest regions of the interstellar medium (ISM). In these regions ISM-dust grains have the potential to coagulate. This study investigates the collisional evolution of the dust population by combining two models: a binary model that simulates the collision between two aggregates and a coagulation model that computes the dust size distribution with time. In the first, results from a parameter study quantify the outcome of the collision - sticking, fragmentation (shattering, breakage, and erosion) - and the effects on the internal structure of the particles in tabular format. These tables are then used as input for the dust evolution model, which is applied to an homogeneous and static cloud of temperature 10K and gas densities between 10^3^ and 10^7^cm^-3^.
- ID:
- ivo://CDS.VizieR/J/A+A/447/221
- Title:
- Dust continuum emission from IRAS sources
- Short Name:
- J/A+A/447/221
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In an ongoing effort to identify and study high-mass protostellar candidates we have observed in various tracers a sample of 235 sources selected from the IRAS Point Source Catalog (Cat. <II/125>), mostly with delta<-30{deg}, with the SEST antenna at millimeter wavelengths. The sample contains 142 Low sources and 93 High, which are believed to be in different evolutionary stages. Both sub-samples have been studied in detail by comparing their physical properties and morphologies.
- ID:
- ivo://CDS.VizieR/J/MNRAS/442/2543
- Title:
- Dust disks around star in young clusters
- Short Name:
- J/MNRAS/442/2543
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We derived the intermediate-mass (=~1.5-7M_{sun}_) disc fraction (IMDF) in the near-infrared JHK photometric bands as well as in the mid-infrared (MIR) bands for young clusters in the age range of 0 to ~10Myr. From the JHK IMDF, the lifetime of the innermost dust disc (~0.3au; hereafter the K disc) is estimated to be ~3Myr, suggesting a stellar mass (M*) dependence of K-disc lifetime (=~1.5-7M_{sun}_). However, from the MIR IMDF, the lifetime of the inner disc (~5au; hereafter the MIR disc) is estimated to be ~6.5Myr, suggesting a very weak stellar mass dependence (M*). The much shorter K-disc lifetime compared to the MIR-disc lifetime for intermediate-mass (IM) stars suggests that IM stars with transition discs, which have only MIR excess emission but no K-band excess emission, are more common than classical Herbig Ae/Be stars, which exhibit both. We suggest that this prominent early disappearance of the K disc for IM stars is due to dust settling/growth in the protoplanetary disc, and it could be one of the major reasons for the paucity of close-in planets around IM stars.
- ID:
- ivo://CDS.VizieR/J/A+A/557/A137
- Title:
- Dust effects on photometric parameters in spirals
- Short Name:
- J/A+A/557/A137
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present results of a study to quantify the effects of dust on the derived photometric parameters of disk and bulges obtained from bulge-disk decomposition: scale-length, effective radius, Sersic index, disk axis-ratio, and bulge-to-disk ratio. The dust induced changes in these parameters were obtained by fitting simulated images of composite systems (containing a disk and a bulge) produced using radiative transfer calculations. The simulations were fitted with the GALFIT 3.0.2 data analysis algorithm. Fits were done with both a combination of an exponential plus a variable- index Sersic function as well as with a combination of two variable-index Sersic functions.
- ID:
- ivo://CDS.VizieR/J/A+A/553/A80
- Title:
- Dust effects on photometric parameters in spirals
- Short Name:
- J/A+A/553/A80
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present results of a study made to quantify the effects of dust on the derived photometric parameters of disks (old and young stellar disks) and bulges: disk scale-lengths, axis-ratios, central surface-brightness, bulge effective radii, and Sersic indices. The changes in the derived photometric parameters from their intrinsic values (as would be seen in the absence of dust) were obtained by fitting simulated images of disks and bulges produced using radiative transfer calculations. The simulations were fitted with the GALFIT 3.0.2 data analysis algorithm and the fitted models were the commonly used infinitely thin disks described by exponential, general Sersic and de Vaucouleurs distributions.
- ID:
- ivo://CDS.VizieR/J/ApJ/697/182
- Title:
- Dust emission from unobscured AGN
- Short Name:
- J/ApJ/697/182
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We use mid-infrared (MIR) spectroscopy of unobscured active galactic nuclei (AGNs) to reveal their native dusty environments. We concentrate on Seyfert 1 galaxies, observing a sample of 31 with the Infrared Spectrograph aboard the Spitzer Space Telescope, and compare them with 21 higher luminosity quasar counterparts.
- ID:
- ivo://CDS.VizieR/J/A+A/622/A132
- Title:
- Dust emission profiles of DustPedia galaxies
- Short Name:
- J/A+A/622/A132
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Most radiative transfer models assume that dust in spiral galaxies is distributed exponentially. In this paper our goal is to verify this assumption by analysing the two-dimensional large-scale distribution of dust in galaxies from the DustPedia sample. For this purpose, we have made use of Herschel imaging in five bands, from 100 to 500um, in which the cold dust constituent is primarily traced and makes up the bulk of the dust mass in spiral galaxies. For a subsample of 320 disc galaxies, we successfully performed a simultaneous fitting with a single Sersic model of the Herschel images in all five bands using the multi-band modelling code GALFITM. We report that the Sersic index n, which characterises the shape of the Sersic profile, lies systematically below 1 in all Herschel bands and is almost constant with wavelength. The average value at 250um is 0.67+/-0.37 (187 galaxies are fitted with n^250^<=0.75, 87 galaxies have 0.75<n^250^<=1.25, and 46 - with n^250^>1.25). Most observed profiles exhibit a depletion in the inner region (at r<0.3-0.4 of the optical radius r25) and are more or less exponential in the outer part. We also find breaks in the dust emission profiles at longer distances (0.5-0.6)r25 which are associated with the breaks in the optical and near-infrared. We assumed that the observed deficit of dust emission in the inner galaxy region is related to the depression in the radial profile of the HI surface density in the same region because the atomic gas reaches high enough surface densities there to be transformed into molecular gas. If a galaxy has a triggered star formation in the inner region (for example, because of a strong bar instability, which transfers the gas inwards to the centre, or a pseudobulge formation), no depletion or even an excess of dust emission in the centre is observed.
- 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.
- ID:
- ivo://CDS.VizieR/J/A+A/357/572
- Title:
- Dust formation in WC stars
- Short Name:
- J/A+A/357/572
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The following table gives the ratefile of the chemical model. Columns {alpha}, {beta} and {gamma} give the rate k at temperature T in the Arrhenius form: k = {alpha} * (T/300)^{beta}^ * exp(-{gamma}/T) The arrows indicate reversible reactions.