ALMA detection of the dusty object silhouetted against the S0 galaxy NGC 3269 in the Antlia cluster

Context. An intriguing silhouette of a small dust patch can be seen against the disk of the S0 galaxy NGC 3269 in the Antlia cluster in optical images. The images do not provide any clue as to whether the patch is a local Jupiter mass-scale cloudlet or a large extragalactic dust complex. Aims. We aim to resolve the nature of this object: is it a small Galactic cloudlet or an extragalactic dust complex? Methods. ALMA and APEX spectroscopy and Gemini GMOS long-slit spectroscopy were used to measure the velocity of the patch and the NGC 3269 disk radial velocity curve. Results. A weak 16 ± 2.5 km s−1 wide 12CO(2 − 1) TMB 19 ± 2.5. mK line in a 2.″2 by 2.″12 beam associated with the object was detected with ALMA. The observed heliocentric velocity, Vr, hel = 3878 ± 5.0 km s−1, immediately establishes the extragalactic nature of the object. The patch velocity is consistent with the velocity of the nucleus of NGC 3269, but not with the radial velocity of the NGC 3269 disk of the galaxy at its position. The ∼4″ angular size of the patch corresponds to a linear size of ∼1 kpc at the galaxy’s Hubble distance of 50.7 Mpc. The mass estimated from the 12CO(2 − 1) emission is ∼1.4 × 106(d/50.7 Mpc)2 M⊙, while the attenuation derived from the optical spectrum implies a dust mass of ∼2.6 × 104(d/50.7 Mpc)2 M⊙. The derived attenuation ratio A′B/(A′B − A′R) of 1.6 ± 0.11 is substantially lower than the corresponding value for the mean Milky Way extinction curve for point sources (2.3). Conclusions. We established the extragalactic nature of the patch, but its origin remains elusive. One possibility is that the dust patch is left over from the removal of interstellar matter in NGC 3269 through the interaction with its neighbour, NGC 3268.

Small-scale star formation as revealed by VVVX galactic cluster candidates

ABSTRACT We report a search and analysis of obscured cluster candidates in the ‘VISTA Variables in the Via Lactea eXtended (VVVX)’ ESO Public Survey area encompassing the region between 229${_{.}^{\circ}}$4 < l < 295${_{.}^{\circ}}$2 and −4${_{.}^{\circ}}$3 < b < 4${_{.}^{\circ}}$4 of the southern Galactic disc. We discover and propose 88 new clusters. We improve the completeness of the embedded cluster population in this region, adding small size (linear diameters of 0.2–1.4 pc) and relatively far objects (heliocentric distance between 2 and 4 kpc) to existing catalogues. Nine candidates are proposed to be older open cluster candidates. Three of them (VVVX CL 204, CL 207, CL 208) have sufficient numbers of well-resolved stellar members to allow us to determine some basic cluster parameters. We confirm their nature as older, low-mass open clusters. Photometric analysis of 15 known clusters shows that they have ages above 20 Myr, and masses below 2000 M⊙: in general, their proper motions follow the motion of the disc. We outline some groups of clusters, most probably formed within the same dust complex. Broadly, our candidates follow the network of filamentary structure in the remaining dust. Thus, in this part of the southern disc of the Galaxy, we have found recent star formation, producing small size and young clusters, in addition to the well-known, massive young clusters, including NGC 3603, Westerlund 2, and the Carina Nebula Complex.

IMEM2: a meteoroid environment model for the inner solar system

Context. The interplanetary dust complex is currently understood to be largely the result of dust production from Jupiter-family comets, with contributions also from longer-period comets (Halley- and Oort-type) and collisionally produced asteroidal dust. Aims. Here we develop a dynamical model of the interplanetary dust cloud from these source populations in order to develop a risk and hazard assessment tool for interplanetary meteoroids in the inner solar system. Methods. The long-duration (1 Myr) integrations of dust grains from Jupiter-family and Halley-type comets and main belt asteroids were used to generate simulated distributions that were compared to COBE infrared data, meteor data, and the diameter distribution of lunar microcraters. This allowed the constraint of various model parameters. Results. We present here the first attempt at generating a model that can simultaneously describe these sets of observations. Extended collisional lifetimes are found to be necessary for larger (radius ≥ 150 μm) particles. The observations are best fit with a differential size distribution that is steep (slope = 5) for radii ≥ 150 μm, and shallower (slope = 2) for smaller particles. At the Earth the model results in ~ 90–98% Jupiter-family comet meteoroids, and small contributions from asteroidal and Halley-type comet particles. In COBE data we find an approximately 80% contribution from Jupiter-family comet meteoroids and 20% from asteroidal particles. The resulting flux at the Earth is mostly within a factor of about two to three of published measurements.

Integrated waste–free processing of the electricarc furnace dust

The article deals with issues of integrated waste-free processing of electric arc furnaces dust. It is shown that it is possible to obtain a whole range of valuable commodity products on both metal and non-metal bases as a result of the electric arc furnaces dust complex processing. Integrated waste–free processing reduces the arc furnaces dust impact on the environment and produces a number of valuable commercial products.

The influx rate of long-period comets in the Earth's neighborhood and their debris contribution to the interplanetary medium

We analyze the flux of new and evolved long-period comets (LPCs) reaching the Earth's neighborhood (perihelion distances q < 1.3 AU), their physical lifetimes, and their implications as regards to the amount of meteoritic matter that is being deposited in the near-Earth region. The flux of LPCs with q < 1.3 au is found to be of about 340 ± 40, brighter than absolute total magnitude 8.6 (radius R ~ 0.6 km) (Fernández and Sosa 2012). Bearing in mind that most of these comets disintegrate into meteoritic matter, this represents a large contribution to the interplanetary dust complex which requires an amount of matter of about 10 tons s−1 to keep it in steady state. These aspects, as well as the impact rate with Earth of meteoroids of LPC origin, will be discussed in this presentation.

Silicate, ruby, opal – Why gas giants keep their jewels in the atmosphere

Giant gas-planets - and brown dwarfs - form dust clouds in their atmospheres which are made of a variety of gemstone-like and possible liquid materials. Our theoretical approach, where we calculate homogeneous nucleation, heterogeneous growth/evaporation, gravitational settling, and element consumption for composite dust grains, allows to access the evolution of the dust complex in the cloud, and hence also the elements remaining in the gas phase. The cloud formation process is imprinted into these remaining elements. Following a (T, p) trajectory into the atmosphere we observe that 1. metals disappear, 2. dust forms, 3. metals re-appear, 4. dust disappears. For the first time, our kinetic cloud formation approach is coupled with an 1D atmosphere simulation and, hence, synthetic spectra can be produced based on detailed cloud micro-physics. Results are demonstrated for metal-poor gas giants and the strong influence of the dust modelling on alkali-line profile is shown.

Dynamical Models of Circumstellar Dust Shells around Long-Period Variables

We present dynamical models of circumstellar dust shells around long-period variables which include time-dependent hydrodynamics and a detailed treatment of dust formation, growth and evaporation. Important effects due to the complex interaction between the dynamics of the pulsating atmosphere and the dust complex are demonstrated.

Dynamical Modeling of Circumstellar Outflows

We review dynamical models of circumstellar dust shells around long-period variables which include time-dependent hydrodynamics and a detailed treatment of dust formation, growth and evaporation. Important effects caused by the complex interaction between the dynamics of the pulsating atmosphere and the dust complex which only can be revealed in the dynamical approach are summarized. Special emphasis is given to the treatment of the dust and gas opacity.