scholarly journals DIBs, Interstellar Dust, and Extinction

2013 ◽  
Vol 9 (S297) ◽  
pp. 147-152 ◽  
Author(s):  
G. C. Clayton
Keyword(s):  
Interstellar Medium ◽  
Interstellar Dust ◽  
Dust Grains ◽  
Weak Correlation ◽  
Interstellar Clouds ◽  
The Galaxy ◽  
The Relationship

AbstractThe relationship between DIBs and dust is still unknown. The correlation between reddening and DIB strength means that the DIBs are mixed in with the dust and gas in interstellar clouds. The DIBs are relatively stronger in the diffuse interstellar medium than in dense clouds. There is only a weak correlation between the DIBs and the UV extinction parameters including the 2175 Å bump strength and the far-UV rise. In addition, the bump dust grains are sometimes polarized, while the DIBs are not. However, observations of DIBs in the SMC show that when the 2175 Å bump is weak or missing so are the DIBs. Two of the four sightlines that deviate strongly from the CCM UV extinction in the Galaxy show weak DIBs.

scholarly journals Photodesorption from Interstellar Dust Grains

1973 ◽  
Vol 52 ◽  
pp. 413-419 ◽  
Author(s):  
Lawrence T. Greenberg
Keyword(s):  
Interstellar Medium ◽  
Interstellar Dust ◽  
Quartz Substrate ◽  
Dust Grains ◽  
Interstellar Clouds ◽  
Interstellar Dust Grains ◽  
Fused Quartz ◽  
Uv Photons ◽  
Molecular Abundances ◽  
Vacuum Uv

An experiment to measure the photodesorption of physisorbed gases from a cold fused quartz substrate by near UV photons is described. The observed yield (mol photon–1) is as large as 10–5, a higher yield is likely in the vacuum UV. Included is a discussion of the photodesorption process and some applications to the interstellar medium. The observed yield is enough to maintain molecular abundances in moderate density interstellar clouds in equilibrium.

scholarly journals Magnesium and silicon in interstellar dust: X-ray overview

2020 ◽  
Vol 641 ◽  
pp. A149
Author(s):  
D. Rogantini ◽  
E. Costantini ◽  
S. T. Zeegers ◽  
M. Mehdipour ◽  
I. Psaradaki ◽  
...  
Keyword(s):  
Cross Sections ◽  
Interstellar Dust ◽  
Galactic Centre ◽  
X Rays ◽  
Dust Grains ◽  
Large Reservoir ◽  
X Ray ◽  
Synchrotron Facility ◽  
The Galaxy ◽  
X Ray Binaries

Context. The dense Galactic environment is a large reservoir of interstellar dust. Therefore, this region represents a perfect laboratory to study the properties of cosmic dust grains. X-rays are the most direct way to detect the interaction of light with dust present in these dense environments. Aims. The interaction between the radiation and the interstellar matter imprints specific absorption features on the X-ray spectrum. We study them with the aim of defining the chemical composition, the crystallinity, and structure of the dust grains that populate the inner regions of the Galaxy. Methods. We investigated the magnesium and the silicon K-edges detected in the Chandra /HETG spectra of eight bright X-ray binaries, distributed in the neighbourhood of the Galactic centre. We modelled the two spectral features using accurate extinction cross-sections of silicates, which we measured at the synchrotron facility Soleil, France. Results. Near the Galactic centre, magnesium and silicon show abundances similar to the solar ones and they are highly depleted from the gas phase (δMg > 0.90 and δSi > 0.96). We find that amorphous olivine with a composition of MgFeSiO4 is the most representative compound along all lines of sight according to our fits. The contribution of Mg-rich silicates and quartz is low (less than 10%). On average we observe a percentage of crystalline dust equal to 11%. For the extragalactic source LMC X-1, we find a preference for forsterite, a magnesium-rich olivine. Along this line of sight we also observe an under-abundance of silicon ASi∕ALMC = 0.5 ± 0.2.

Interstellar Probe: A Mission to the Heliospheric Boundary and Interstellar Medium for the Next Decade

2021 ◽  
Author(s):  
Pontus Brandt ◽  
Ralph McNutt ◽  
Elena Provornikova ◽  
Carey Lisse ◽  
Kathleen Mandt ◽  
...  
Keyword(s):  
Interstellar Medium ◽  
Space Exploration ◽  
Launch Vehicles ◽  
Applied Physics ◽  
Gravity Assist ◽  
Interstellar Clouds ◽  
The Galaxy ◽  
Historic Data ◽  
Near Term ◽  
Interstellar Probe

<p>An Interstellar Probe mission to the Very Local Interstellar Medium (VLISM) would bring new scientific discoveries of the mechanisms upholding our vast heliosphere and directly sample the unexplored Local Interstellar Clouds that our Sun is moving through in relatively short galactic timescales. As such, it would represent Humanity's first explicit step in to the galaxy and become perhaps NASA's boldest step in space exploration. Such a mission has been discussed and studied since 1960, but the stumbling block has often been propulsion. Now this hurdle has been overcome by the availability of new and larger launch vehicles. An international team of scientists and experts are now progressing towards the final year of a NASA-funded study led by The Johns Hopkins University Applied Physics Laboratory (APL) to develop pragmatic example mission concepts for an Interstellar Probe with a nominal design lifetime of 50 years. Together with the Space Launch System (SLS) Office at the NASA Marshall Space Flight Center, the team has analyzed dozens of launch configurations and demonstrate that asymptotic speeds in excess of 7.5 Astronomical Units (AU) per year can be achieved using existing or near-term propulsion stages with a powered or passive Jupiter Gravity Assist (JGA). These speeds are more than twice that of the fastest escaping man-made spacecraft to date, which is Voyager 1 currently at 3.59 AU/year. An Interstellar Probe would therefore reach the Termination Shock (TS) in less than 12 years and cross the Heliopause into the VLISM after about 16 years from launch.</p><p>In this presentation we provide an overview and update of the study, the science mission concept, discuss the compelling discoveries that await, and the associated example science payload, measurements and operations ensuring a historic data return that would push the boundaries of space exploration by going where no one has gone before.</p>

scholarly journals Origin and evolution of the Galactic inventories of interstellar dust and its composition

2020 ◽  
Vol 494 (3) ◽  
pp. 4149-4167
Author(s):  
Anuj Gupta ◽  
Sandeep Sahijpal
Keyword(s):  
Interstellar Dust ◽  
Galactic Centre ◽  
Dust Grains ◽  
Thermodynamical Equilibrium ◽  
Origin And Evolution ◽  
Isotopic Signatures ◽  
Interstellar Dust Grains ◽  
Wide Range ◽  
Dust Mass ◽  
The Galaxy

ABSTRACT Interstellar dust is a significant component of matter in the galaxies. The dust owns its origin and reprocessing in a wide range of astrophysical environments. In order to understand the origin and evolution of the distinct types of interstellar dust grains, we have attempted a comprehensive correlated study of the thermodynamics condensation of dust grains in distinct stellar environments with the Galactic chemical evolution of the Milky Way Galaxy. The Galaxy is evolved in terms of elemental evolution resulting from stellar nucleosynthetic contributions of several generations of stars. Based on the elemental composition of the evolving Galaxy, the relative abundances of the major constituents of interstellar dust are assessed. The major aim is to redistribute the various condensable elements at any epoch during the evolution of the Galaxy into various grain constituents and understand their abundance evolution based on a mass-balance formalism. We also performed thermodynamical equilibrium condensation calculations to understand the stellar origin of various grain constituents that could carry the isotopic signatures of the various stellar nucleosynthetic sources. This is perhaps a novel attempt to estimate the bulk dust mass budget in the evolving Galaxy. The normalized mass of the Galactic dust is predicted to decrease with the increase in distance from the Galactic centre. It increases over time. The supernovae SNe Ia are predicted as the most prominent sources of Fe-dust mass, the supernova SN II+Ib/c produces oxides- and silicate-dust mass, and the AGB stars contribute to carbonaceous dust mass.

scholarly journals Giant molecular clouds in the galaxy: distribution, mass, size and age

1979 ◽  
Vol 84 ◽  
pp. 35-52 ◽  
Author(s):  
P. M. Solomon ◽  
D. B. Sanders ◽  
N. Z. Scoville
Keyword(s):  
Interstellar Medium ◽  
Molecular Clouds ◽  
Galactic Disk ◽  
Free Fall ◽  
Major Constituent ◽  
Giant Molecular Clouds ◽  
Interstellar Clouds ◽  
Dominant Component ◽  
The Galaxy ◽  
Galactic Distribution

Millimeter wave observations of emission from the CO molecule have become, over the past eight years, the dominant method for determining the physical properties of dense interstellar clouds, composed primarily of molecular hydrogen and for exploring the structure and kinematics of the galactic disk. In this paper we briefly review the CO survey results in the literature (Section 2) and then present new results (Section 3-7) of an extensive 13CO and 12CO survey of the galactic distribution, size, mass and age of molecular clouds. The interpretation of this survey leads to a new picture of the interstellar medium dominated by very massive stable long-lived clouds which we refer to as Giant Molecular Clouds. We find that Giant Molecular Clouds (GMC's) with M = 105–3 × 106M⊙ are a major constituent of the galactic disk, the dominant component of the interstellar medium in the galaxy interior to the sun and the most massive objects in the galaxy. We find that the interstellar medium and star formation are dominated by massive gravitationally bound clouds in which stars and associations are forming but at a very low rate in comparison to the free fall time. The galactic distribution of the molecules as traced by CO emission is interpreted as the distribution of GMC's. As the most massive objects in the galaxy they are also basic to the dynamics of the disk.

scholarly journals Modelling interstellar physics and chemistry: implications for surface and solid-state processes

2013 ◽  
Vol 371 (1994) ◽  
pp. 20110587 ◽  
Author(s):  
David Williams ◽  
Serena Viti
Keyword(s):  
Solid State ◽  
Interstellar Medium ◽  
Crucial Role ◽  
Interstellar Dust ◽  
Milky Way ◽  
Computational Study ◽  
Dust Grains ◽  
Theoretical Approaches ◽  
Interstellar Dust Grains ◽  
The Universe

We discuss several types of regions in the interstellar medium of the Milky Way and other galaxies in which the chemistry appears to be influenced or dominated by surface and solid-state processes occurring on or in interstellar dust grains. For some of these processes, for example, the formation of H 2 molecules, detailed experimental and theoretical approaches have provided excellent fundamental data for incorporation into astrochemical models. In other cases, there is an astrochemical requirement for much more laboratory and computational study, and we highlight these needs in our description. Nevertheless, in spite of the limitations of the data, it is possible to infer from astrochemical modelling that surface and solid-state processes play a crucial role in astronomical chemistry from early epochs of the Universe up to the present day.

scholarly journals Chemical Kinetics Simulations of Ice Chemistry on Porous Versus Non-Porous Dust Grains

2021 ◽  
Vol 8 ◽  
Author(s):  
Drew A. Christianson ◽  
Robin T. Garrod
Keyword(s):  
Chemical Kinetics ◽  
Interstellar Dust ◽  
Three Dimensional ◽  
Binding Energies ◽  
Inert Gases ◽  
Chemical Effect ◽  
Dust Grains ◽  
Interstellar Clouds ◽  
Dust Grain ◽  
Grain Surface

The degree of porosity in interstellar dust-grain material is poorly defined, although recent work has suggested that the grains could be highly porous. Aside from influencing the optical properties of the dust, porosity has the potential to affect the chemistry occurring on dust-grain surfaces, via increased surface area, enhanced local binding energies, and the possibility of trapping of molecules within the pores as ice mantles build up on the grains. Through computational kinetics simulations, we investigate how interstellar grain-surface chemistry and ice composition are affected by the porosity of the underlying dust-grain material. Using a simple routine, idealized three-dimensional dust-grains are constructed, atom by atom, with varying degrees of porosity. Diffusive chemistry is then simulated on these surfaces using the off-lattice microscopic Monte Carlo chemical kinetics model, MIMICK, assuming physical conditions appropriate to dark interstellar clouds. On the porous grain surface, the build-up of ice mantles, mostly composed of water, leads to the covering over of the pores, leaving empty pockets. Once the pores are completely covered, the chemical and structural behavior is similar to non-porous grains of the same size. The most prominent chemical effect of the presence of grain porosity is the trapping of molecular hydrogen, formed on the grain surfaces, within the ices and voids inside the grain pores. Trapping of H2 in this way may indicate that other volatiles, such as inert gases not included in these models, could be trapped within dust-grain porous structures when ices begin to form.

scholarly journals Modeling of Interstellar Dust Grains

2008 ◽  
Vol 7 (2) ◽  
pp. 78-87
Author(s):  
Nagalakshmi A. Rao
Keyword(s):  
Interstellar Medium ◽  
Interstellar Dust ◽  
Interstellar Extinction ◽  
Dipole Approximation ◽  
Dust Grains ◽  
Scattering Parameters ◽  
Light Passing ◽  
Interstellar Dust Grains ◽  
Blue Wavelength ◽  
Dust Grain

Dust has two major effects on light passing through the Interstellar Medium - Interstellar Extinction and Reddening. Interstellar dust grains are typically a fraction of a micron, approximately the wavelength of blue light and hence light passing through dust is depleted in blue wavelength, causing Interstellar Reddening. Dust Grain Models are mainly based on the analysis of interstellar extinction and polarization curves. Discrete Dipole Approximation (DDA) is the best studied model to compute scattering parameters of the grain.

scholarly journals Dust evolution in the star forming turbulent interstellar medium

2006 ◽  
Vol 2 (S237) ◽  
pp. 47-52
Author(s):  
François Boulanger
Keyword(s):  
Interstellar Medium ◽  
Interstellar Dust ◽  
Dust Particles ◽  
Interstellar Clouds ◽  
Star Forming ◽  
Interstellar Turbulence ◽  
Star Forming Regions ◽  
Potential Impact ◽  
Dust Evolution ◽  
Small Dust

AbstractUnderstanding interstellar dust evolution is a major challenge underlying the interpretation of Spitzer observations of interstellar clouds, star forming regions and galaxies. I illustrate on-going work along two directions. I outline the potential impact of interstellar turbulence on the abundance of small dust particles in the diffuse interstellar medium and translucent sections of molecular clouds. I present results from an analysis of ISO and Spitzer observations of the central part of 30 Doradus, looking for dust evolution related to the radiative and dynamical impact of the R136 super star cluster on its parent molecular cloud.

scholarly journals Modelling the properties of interstellar dust using the Si K-edge

2019 ◽  
Vol 15 (S350) ◽  
pp. 259-263
Author(s):  
Sascha Zeegers ◽  
Elisa Costantini ◽  
Daniele Rogantini ◽  
Cor de Vries ◽  
Harald Mutschke ◽  
...  
Keyword(s):  
Interstellar Medium ◽  
Cross Sections ◽  
Interstellar Dust ◽  
X Rays ◽  
X Ray ◽  
Synchrotron Facility ◽  
The Galaxy ◽  
Main Components ◽  
Distribution Composition ◽  
X Ray Binaries

AbstractThe properties of interstellar dust (ID) can be studied in great detail by making use of X-ray spectroscopy techniques. The radiation of X-rays sources is scattered and absorbed by dust grains in the interstellar medium. The X-ray band is especially suitable to study silicates - one of the main components of ID -since it contains the absorption edges of Si, Mg, O and Fe. In the Galaxy, we can use absorption features in the spectra of X-ray binaries to study the size distribution, composition and crystalline structure of grains. In order to derive these properties, it is necessary to acquire a database of detailed extinction cross sections models, that reflects the composition of the dust in the interstellar medium. We present the extinction profiles of a set of newly acquired measurements of 14 dust analogues at the Soleil Synchrotron facility in Paris, where we focus on silicates and the Si-K edge in particular, which is modelled with unprecedented accuracy. These models are used to analyse ID in the dense environments of the Galaxy.

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