scholarly journals A method for mapping the aliphatic hydrocarbon content of interstellar dust towards the Galactic Centre

2020 ◽  
Vol 493 (1) ◽  
pp. 1109-1119
Author(s):  
B Günay ◽  
M G Burton ◽  
M Afşar ◽  
T W Schmidt
Keyword(s):  
Interstellar Dust ◽  
Elemental Carbon ◽  
Total Carbon ◽  
Galactic Centre ◽  
Absorption Feature ◽  
Ir Camera ◽  
Carbon Abundance ◽  
The Galaxy ◽  
Aliphatic Carbon

ABSTRACT In the interstellar medium, the cosmic elemental carbon abundance includes the total carbon in both gas and solid phases. The aim of the study was to trial a new method for measuring the amount and distribution of aliphatic carbon within interstellar dust over wide fields of view of our Galaxy. This method is based on the measurement of the 3.4-$\mu$m absorption feature from aliphatic carbonaceous matter. This can readily be achieved for single sources using infrared (IR) spectrometers. However, making such measurements over wide fields requires an imaging IR camera, equipped with narrow-band filters that are able to sample the spectrum. While this cannot produce as good a determination of the spectra, the technique can be applied to potentially tens to hundreds of sources simultaneously, over the field of view of the camera. We examined this method for a field in the centre of the Galaxy, and produced a map showing the variation of 3.4-$\mu$m optical depth across it.

scholarly journals The Arches cluster revisited

2019 ◽  
Vol 623 ◽  
pp. A84 ◽  
Author(s):  
J. S. Clark ◽  
M. E. Lohr ◽  
L. R. Patrick ◽  
F. Najarro
Keyword(s):  
Main Sequence ◽  
Mass Function ◽  
Initial Mass Function ◽  
Galactic Centre ◽  
Complete Dataset ◽  
Subsequent Determination ◽  
The Galaxy ◽  
First Time ◽  
Massive Clusters

The Arches is one of the youngest, densest and most massive clusters in the Galaxy. As such it provides a unique insight into the lifecycle of the most massive stars known and the formation and survival of such stellar aggregates in the extreme conditions of the Galactic Centre. In a previous study we presented an initial stellar census for the Arches and in this work we expand upon this, providing new and revised classifications for ∼30% of the 105 spectroscopically identified cluster members as well as distinguishing potential massive runaways. The results of this survey emphasise the homogeneity and co-evality of the Arches and confirm the absence of H-free Wolf-Rayets of WC sub-type and predicted luminosities. The increased depth of our complete dataset also provides significantly better constraints on the main sequence population; with the identification of O9.5 V stars for the first time we now spectroscopically sample stars with initial masses ranging from ∼16 M⊙ to ≥120 M⊙. Indeed, following from our expanded stellar census we might expect ≳50 stars within the Arches to have been born with masses ≳60 M⊙, while all 105 spectroscopically confirmed cluster members are massive enough to leave relativistic remnants upon their demise. Moreover the well defined observational properties of the main sequence cohort will be critical to the construction of an extinction law appropriate for the Galactic Centre and consequently the quantitative analysis of the Arches population and subsequent determination of the cluster initial mass function.

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.

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 Planetary nebulae in the central region of the Galaxy

1964 ◽  
Vol 20 ◽  
pp. 41-45 ◽  
Author(s):  
L. Perek
Keyword(s):  
Central Region ◽  
Surface Brightness ◽  
Large Scale ◽  
Direct Determination ◽  
Planetary Nebulae ◽  
Galactic Centre ◽  
Large Numbers ◽  
The Galaxy ◽  
Objective Prism

Planetary nebulae are convenient objects for studying the large-scale structure of the Galaxy. Firstly, they are easily recognized up to considerable distances on plates taken through an objective prism, and secondly, methods have been devised by various authors to determine their distances from two observable quantities: angular diameter and surface brightness. The importance of the subsystem of planetary nebulae has been accentuated especially by the discoveries by Minkowski and Haro of large numbers of planetaries in the direction of the galactic centre. The distribution of planetaries on the sphere suggests that they are connected with the galactic nucleus, but no direct determination of their distances, which would either confirm or contradict this statement, is available. The most serious obstacle in studying the subsystem of planetaries is the lack of observing data. The aim of the reported paper (Perek 1963) is to give a tentative outline of the distribution of planetaries in space based on extensive new observing material.

scholarly journals 6. The distribution of atomic hydrogen in the inner parts of the Galaxy

1957 ◽  
Vol 4 ◽  
pp. 37-41
Author(s):  
M. Schmidt
Keyword(s):  
Radial Velocity ◽  
Atomic Hydrogen ◽  
Galactic Centre ◽  
The Sun ◽  
The Galaxy ◽  
Latitude Distribution ◽  
Inner Parts

The determination of the distribution of hydrogen from 21-cm. observations in parts of the Galaxy, which are nearer to the centre than the sun, is seriously handicapped by the fact that the observed radial velocity of the hydrogen clouds determines only the distance to the galactic centre. So two possible values of the distance to the sun correspond to one value of the frequency. We have used as a criterion to separate the contributions from the two regions the latitude distribution of the radiation.

scholarly journals Interstellar Extinction in the Magellanic Clouds

1984 ◽  
Vol 108 ◽  
pp. 341-351
Author(s):  
K. Nandy
Keyword(s):  
Interstellar Dust ◽  
Interstellar Extinction ◽  
Magellanic Clouds ◽  
Absorption Feature ◽  
Early Type ◽  
Distribution Law ◽  
Broad Absorption ◽  
Grain Sizes ◽  
The Galaxy ◽  
The Difference

The extinction properties of interstellar dust in the Large and Small Magellanic Clouds have been systematically investigated, using recent UV observations of early type Cloud members along with complementary visible data. The extinction curves differ systematically from the standard Galactic curve. The latter shows a broad absorption feature centred near 2200Å in virtually all sight lines but this is absent or only weakly present in the SMC; also the SMC extinction in the far UV is the largest known relative to EB-V. Dust in the LMC appears to be intermediate in extinction properties between the SMC and normal Galactic material. However, exceptions from the average extinction curves have been found in both Clouds.Model computations show that the range of grain sizes and their number distribution law may not be significantly different in the Clouds and the Galaxy; the difference in extinction laws can be accounted for by varying the graphite contribution relative to silicate.

scholarly journals Aliphatic hydrocarbon content of interstellar dust

2019 ◽  
Vol 15 (S350) ◽  
pp. 241-244
Author(s):  
T. W. Schmidt ◽  
B. Günay ◽  
M. G. Burton ◽  
A. Rawal
Keyword(s):  
Absorption Coefficient ◽  
Column Density ◽  
Interstellar Dust ◽  
Aliphatic Hydrocarbon ◽  
Line Of Sight ◽  
Absorption Feature ◽  
Astronomical Observations ◽  
Hydrocarbon Content ◽  
Aliphatic Carbon ◽  
C Nmr

AbstractThe mid-IR spectrum of the interstellar medium contains both aromatic and aliphatic hydrocarbon features. These are generally attributed to carbonaceous dust. The aliphatic component is of particular interest because it produces a significant 3.4 μm absorption feature. The optical depth of this feature is related to the number and type of aliphatic carbon C–H bonds in the line of sight. It is possible to estimate the column density of aliphatic carbon from quantitative analysis of the 3.4 μm interstellar feature, providing that the absorption coefficient of interstellar aliphatic hydrocarbon is known. We produced interstellar dust analogues with spectra closely matching astronomical observations. Using a combination of FTIR and 13C NMR spectroscopy, we determined an integrated absorption coefficient of the aliphatic component. The results thus obtained permit direct calibration of astronomical observations, providing rigorous estimates of the amount of aliphatic carbon in the ISM.

Interstellar gas in the central region of the Galaxy

1967 ◽  
Vol 31 ◽  
pp. 239-251 ◽  
Author(s):  
F. J. Kerr
Keyword(s):  
Central Region ◽  
Galactic Plane ◽  
Neutral Hydrogen ◽  
Continuum Emission ◽  
Galactic Centre ◽  
Interstellar Gas ◽  
Hydrogen Recombination ◽  
The Galaxy ◽  
Centre Region ◽  
The Relationship

A review is given of information on the galactic-centre region obtained from recent observations of the 21-cm line from neutral hydrogen, the 18-cm group of OH lines, a hydrogen recombination line at 6 cm wavelength, and the continuum emission from ionized hydrogen.Both inward and outward motions are important in this region, in addition to rotation. Several types of observation indicate the presence of material in features inclined to the galactic plane. The relationship between the H and OH concentrations is not yet clear, but a rough picture of the central region can be proposed.

Galactic orbits of stars

1966 ◽  
Vol 25 ◽  
pp. 93-97
Author(s):  
Richard Woolley
Keyword(s):  
Globular Cluster ◽  
Potential Field ◽  
High Velocity ◽  
Velocity Vector ◽  
Variable Stars ◽  
The Sun ◽  
Proper Motions ◽  
Rr Lyrae ◽  
The Galaxy

It is now possible to determine proper motions of high-velocity objects in such a way as to obtain with some accuracy the velocity vector relevant to the Sun. If a potential field of the Galaxy is assumed, one can compute an actual orbit. A determination of the velocity of the globular clusterωCentauri has recently been completed at Greenwich, and it is found that the orbit is strongly retrograde in the Galaxy. Similar calculations may be made, though with less certainty, in the case of RR Lyrae variable stars.

Sign in / Sign up

Export Citation Format

Share Document