scholarly journals Interrelations Between Astrochemistry and Galactic Dynamics

2021 ◽  
Vol 8 ◽  
Author(s):  
Edgar Mendoza ◽  
Nicolas Duronea ◽  
Daniele Ronsó ◽  
Lia C. Corazza ◽  
Floris van der Tak ◽  
...  
Keyword(s):  
Latin American ◽  
Galactic Disk ◽  
Asymptotic Giant Branch ◽  
Structure Evolution ◽  
Galactic Dynamics ◽  
Chemical Abundance ◽  
Star Forming ◽  
Star Forming Regions ◽  
The Andes ◽  
External Galaxies

This paper presents a review of ideas that interconnect astrochemistry and galactic dynamics. Since these two areas are vast and not recent, each one has already been covered separately by several reviews. After a general historical introduction, and a needed quick review of processes such as stellar nucleosynthesis that gives the base to understand the interstellar formation of simple chemical compounds (e.g., H2, CO, NH3, and H2O), we focus on a number of topics that are at the crossing of the two big areas, dynamics and astrochemistry. Astrochemistry is a flourishing field that intends to study the presence and formation of molecules as well as the influence of them on the structure, evolution, and dynamics of astronomical objects. The progress in the knowledge on the existence of new complex molecules and of their process of formation originates from the observational, experimental, and theoretical areas that compose the field. The interfacing areas include star formation, protoplanetary disks, the role of the spiral arms, and the chemical abundance gradients in the galactic disk. It often happens that the physical conditions in some regions of the interstellar medium are only revealed by means of molecular observations. To organize a rough classification of chemical evolution processes, we discuss about how astrochemistry can act in three different contexts, namely, the chemistry of the early universe, including external galaxies, star-forming regions, and asymptotic giant branch (AGB) stars and circumstellar envelopes. We mention that our research is stimulated by plans for instruments and projects, such as the ongoing Large Latin American Millimeter Array (LLAMA), which consists in the construction of a 12 m sub-mm radio telescope in the Andes. Thus, modern and new facilities can play a key role in new discoveries not only in astrochemistry but also in radio astronomy and related areas. Furthermore, the research on the origin of life is also a stimulating perspective.

scholarly journals The Galactic Halo Ionising Field

1997 ◽  
Vol 14 (1) ◽  
pp. 59-63 ◽  
Author(s):  
J. Bland-Hawthorn ◽  
P. R. Maloney
Keyword(s):  
Galactic Halo ◽  
Galactic Disk ◽  
Line Emission ◽  
Young Stars ◽  
Star Forming ◽  
Star Forming Regions ◽  
Optical Line ◽  
The Mean ◽  
Alternative Sources ◽  
Magellanic Stream

AbstractThere has been much debate in recent decades as to what fraction of ionising photons from star-forming regions in the Galactic disk escape into the halo. The recent detection of the Magellanic Stream in optical line emission at the CTIO 4 m and the AAT 3·9 m telescopes may now provide the strongest evidence that at least some of the radiation escapes the disk completely. We present a simple model to demonstrate that, while the distance to the Magellanic Stream is uncertain, the observed emission measures (εm ≈ 0·5 – 1 cm−6 pc) are most plausibly explained by photoionisation due to hot, young stars. This model requires that the mean Lyman-limit opacity perpendicular to the disk is τLL ≈ 3, and the covering fraction of the resolved clouds is close to unity. Alternative sources (e.g. shock, halo, LMC or metagalactic radiation) contribute negligible ionising flux.

scholarly journals RadioAstron space-VLBI project: studies of masers in star forming regions of our Galaxy and megamasers in external galaxies

2017 ◽  
Vol 13 (S336) ◽  
pp. 417-421 ◽  
Author(s):  
A. M. Sobolev ◽  
N. N. Shakhvorostova ◽  
A. V. Alakoz ◽  
W. A. Baan
Keyword(s):  
Angular Resolution ◽  
Nearby Galaxy ◽  
Major Step ◽  
Maser Emission ◽  
Star Forming ◽  
Star Forming Regions ◽  
The Galaxy ◽  
External Galaxies ◽  
First Time ◽  
Water Maser

AbstractObservations of the masers in the course of RadioAstron mission yielded detections of fringes for a number of sources in both water and hydroxyl maser transitions. Several sources display numerous ultra-compact details. This proves that implementation of the space VLBI technique for maser studies is possible technically and is not always prevented by the interstellar scattering, maser beaming and other effects related to formation, transfer, and detection of the cosmic maser emission. For the first time, cosmic water maser emission was detected with projected baselines exceeding Earth Diameter. It was detected in a number of star-forming regions in the Galaxy and two megamaser galaxies NGC 4258 and NGC 3079. RadioAstron observations provided the absolute record of the angular resolution in astronomy. Fringes from the NGC 4258 megamaser were detected on baseline exceeding 25 Earth Diameters. This means that the angular resolution sufficient to measure the parallax of the water maser source in the nearby galaxy LMC was directly achieved in the cosmic maser observations. Very compact features with angular sizes about 20\muas\, have been detected in star-forming regions of our Galaxy. Corresponding linear sizes are about 5-10 million kilometers. So, the major step from milli- to micro-arcsecond resolution in maser studies is achieved by the RadioAstron mission. The existence of the features with extremely small angular sizes is established. Further implementations of the space–VLBI maser instrument for studies of the nature of cosmic objects, studies of the interaction of extremely high radiation field with molecular material and studies of the matter on the line of sight are planned.

scholarly journals Warm ionized ISM in the bulge of Andromeda galaxy

2009 ◽  
Vol 5 (H15) ◽  
pp. 296-296
Author(s):  
Marat Gilfanov ◽  
Akos Bogdan
Keyword(s):  
Galactic Disk ◽  
Broad Band ◽  
Young Stellar Objects ◽  
Stellar Objects ◽  
Spiral Arms ◽  
X Ray ◽  
Star Forming ◽  
Star Forming Regions ◽  
Broad Band Emission ◽  
Band Emission

AbstractWe demonstrate that unresolved X-ray emission from the bulge of M31 is composed of at least three different components: (i) Broad-band emission from a large number of faint sources – mainly accreting white dwarfs and active binaries, associated with the old stellar population, similar to the Galactic Ridge X-ray emission of the Milky Way. (ii) Soft emission from ionized gas with temperature of about ~ 300 eV and mass of ~ 4 × 106 M⊙. The gas distribution is significantly elongated along the minor axis of the galaxy suggesting that it may be outflowing in the direction perpendicular to the galactic disk. The shadows cast on the gas by spiral arms and the 10-kpc star-forming ring confirm large off-plane extent of the gas. (iii) Hard unresolved emission from spiral arms, most likely associated with protostars and young stellar objects located in the star-forming regions.

scholarly journals Herschel/HIFI Discoveryof a Far-Infrared DIB Analog

2013 ◽  
Vol 9 (S297) ◽  
pp. 197-202
Author(s):  
H. S. P. Müller ◽  
P. Schilke ◽  
M. Gerin ◽  
D. C. Lis ◽  
E. A. Bergin ◽  
...  
Keyword(s):  
Interstellar Medium ◽  
Molecular Clouds ◽  
Galactic Center ◽  
Galactic Disk ◽  
Far Infrared ◽  
Line Of Sight ◽  
Absorption Feature ◽  
Substantial Part ◽  
Star Forming ◽  
Star Forming Regions

AbstractThe Herschel Space Observatory carried out observations at far-infrared wavelengths, which significantly increased our knowledge of the interstellar medium and the star-formation process in the Milky Way and external galaxies, as well as our understanding of astrochemistry.Absorption features, known, e.g., from observations at millimeter wavelengths, are more commonly observed in the far-infrared, in particular toward strong dust continuum sources. The lowest energy transitions are not only observed at LSR-velocities related to the source, but often also at velocities associated with diffuse molecular clouds along the line of sight toward the background source.Unbiased spectral line surveys of the massive and very luminous Galactic Center sources Sagittarius B2(M) and (N) were carried out across the entire frequency range of the high-resolution Heterodyne Instrument for Far-Infrared Astronomy (HIFI). An absorption feature was detected toward both sources at about 617.531 GHz, corresponding to 20.599 cm−1, 485.47 μm, or 2.5539 meV. This feature is unique in its appearance at all velocity components associated with diffuse foreground molecular clouds, together with its conspicuous absence at velocities related to the sources themselves. The carriers of at least a substantial part of the DIBs are thought to reside in the diffuse interstellar medium. Therefore, we consider this absorption feature to be a far-infrared DIB analog.Subsequent dedicated observations confirmed that the line is present only in the foreground clouds on the line of sight toward other massive star-forming regions in the Galactic disk. There is indication that the feature has substructure, possibly of fine or hyperfine nature. Attempts to assign the feature to atomic or molecular species have been unsuccessful so far.

scholarly journals The Distribution of Young Stars in Nearby Galaxies

1986 ◽  
Vol 116 ◽  
pp. 61-80 ◽  
Author(s):  
W. L. Freedman
Keyword(s):  
Spatial Distribution ◽  
Milky Way ◽  
Young Stars ◽  
Panoramic View ◽  
Star Forming ◽  
Individual Stars ◽  
Star Forming Regions ◽  
The Galaxy ◽  
External Galaxies ◽  
Nearby Galaxies

Although luminous stars are relatively rare, they can potentially be studied out to large distances. In our own Milky Way, this advantage is offset by obscuration due to dust in the plane of the Galaxy. In addition, distances to these individual stars are extremely difficult to determine. The study of external galaxies allows a panoramic view of the system and its individually brightest stars which are all at a common distance. The spatial distribution of star forming regions is immediately apparent, and the effects of obscuration are minimized. Nearby resolved galaxies therefore provide a rich resource for examining the properties of the intrinsically brightest stars and their relation to other components of the galaxy.

scholarly journals Using deuterated H 3 + and other molecular species to understand the formation of stars and planets

2012 ◽  
Vol 370 (1978) ◽  
pp. 5186-5199 ◽  
Author(s):  
F. F. S. van der Tak
Keyword(s):  
Line Emission ◽  
Rotational Line ◽  
High Electron ◽  
Interstellar Gas ◽  
Warm Up ◽  
Star Forming ◽  
Physical Conditions ◽  
Star Forming Regions ◽  
Direct Observations ◽  
External Galaxies

The ion plays a key role in the chemistry of dense interstellar gas clouds where stars and planets are forming. The low temperatures and high extinctions of such clouds make direct observations of impossible, but lead to large abundances of H 2 D + and D 2 H + that are very useful probes of the early stages of star and planet formation. Maps of H 2 D + and D 2 H + pure rotational line emission towards star-forming regions show that the strong deuteration of is the result of near-complete molecular depletion of CNO-bearing molecules onto grain surfaces, which quickly disappears as cores warm up after stars have formed. In the warmer parts of interstellar gas clouds, transfers its proton to other neutrals such as CO and N 2 , leading to a rich ionic chemistry. The abundances of such species are useful tracers of physical conditions such as the radiation field and the electron fraction. Recent observations of HF line emission towards the Orion Bar imply a high electron fraction, and we suggest that observations of OH + and H 2 O + emission may be used to probe the electron density in the nuclei of external galaxies.

scholarly journals Methanol Maser Parallaxes and Proper Motions

2012 ◽  
Vol 8 (S287) ◽  
pp. 368-376
Author(s):  
Y. Xu ◽  
M. J. Reid ◽  
L. Moscadelli ◽  
K. M. Menten ◽  
X. W. Zheng ◽  
...  
Keyword(s):  
Massive Star ◽  
Galactic Disk ◽  
Slow Motion ◽  
Class Ii ◽  
Star Forming ◽  
Gas Kinematics ◽  
Star Forming Regions ◽  
Time Class ◽  
Exciting Star ◽  
Motion Measurements

AbstractDue to their compactness, persistence and slow motion, Class II CH3OH masers are excellent targets for parallax and proper motion measurements for massive star-forming regions in the Galactic Disk. These measurements can be used to improve our understanding of the spiral structure and dynamics of the Milky Way. At the same time, Class II CH3OH masers can also be used to study gas kinematics close to the exciting star, tracing rotation, infall and/or outflow motions.

scholarly journals Astrochemistry During the Formation of Stars

2020 ◽  
Vol 58 (1) ◽  
pp. 727-778
Author(s):  
Jes K. Jørgensen ◽  
Arnaud Belloche ◽  
Robin T. Garrod
Keyword(s):  
Solar System ◽  
Organic Molecules ◽  
Galactic Center ◽  
Galactic Disk ◽  
System Size ◽  
High Mass ◽  
Star Forming ◽  
Star Forming Regions ◽  
Chemical Models ◽  
Complex Organic

Star-forming regions show a rich and varied chemistry, including the presence of complex organic molecules—in both the cold gas distributed on large scales and the hot regions close to young stars where protoplanetary disks arise. Recent advances in observational techniques have opened new possibilities for studying this chemistry. In particular, the Atacama Large Millimeter/submillimeter Array has made it possible to study astrochemistry down to Solar System–size scales while also revealing molecules of increasing variety and complexity. In this review, we discuss recent observations of the chemistry of star-forming environments, with a particular focus on complex organic molecules, taking context from the laboratory experiments and chemical models that they have stimulated. The key takeaway points include the following: ▪  The physical evolution of individual sources plays a crucial role in their inferred chemical signatures and remains an important area for observations and models to elucidate. ▪  Comparisons of the abundances measured toward different star-forming environments (high-mass versus low-mass, Galactic Center versus Galactic disk) reveal a remarkable similarity, which is an indication that the underlying chemistry is relatively independent of variations in their physical conditions. ▪  Studies of molecular isotopologues in star-forming regions provide a link with measurements in our own Solar System, and thus may shed light on the chemical similarities and differences expected in other planetary systems.

scholarly journals Tracing pumping routes in OH

2007 ◽  
Vol 3 (S242) ◽  
pp. 17-24 ◽  
Author(s):  
Malcolm D. Gray ◽  
D. A. Howe ◽  
B. M. Lewis
Keyword(s):  
Local Thermodynamic Equilibrium ◽  
Large Fraction ◽  
Numerical Algorithms ◽  
Asymptotic Giant Branch ◽  
Agb Stars ◽  
Star Forming ◽  
Star Forming Regions ◽  
Red Supergiants ◽  
Non Local ◽  
General Method

AbstractWe introduce a general method of restoring detailed information about the population flow in molecules under non-local-thermodynamic-equilibrium (NLTE) conditions. This information is usually discarded in numerical algorithms which generate only a solution. We apply the method to tracing the pumping schemes for OH in models that represent three common astrophysical maser environments: the envelopes of asymptotic-giant-branch (AGB) stars, the envelopes of red supergiants, and Galactic star-forming regions. In all three of these cases, we show that a large fraction, typically 0.8 or more, of the maser inversion can be recovered from a set of routes that depend on a much smaller fraction (considerably less than 0.1) of the total number of input coefficients to the model. Therefore, these cases display underlying simplicity in the pumping scheme.

scholarly journals Identification of extragalactic star forming complexes

2021 ◽  
Author(s):  
D. D. Lisitsin ◽  
◽  
A. V. Kuzin ◽  
Keyword(s):  
Star Formation ◽  
Dust Emission ◽  
Young Star ◽  
Star Forming ◽  
Star Forming Regions ◽  
Spectral Bands ◽  
Polycyclic Aromatic ◽  
Hydrocarbon Emission ◽  
External Galaxies ◽  
Nearby Galaxies

We developed a technique for selecting star forming complexes in external galaxies based on an analysis of radiation maps in various spectral bands. Using this method, we identified star formation complex candidates in 17 nearby galaxies applying three criteria. These criteria are polycyclic aromatic hydrocarbon emission, dust emission, and ultraviolet young star emission. Relating the information derived from these criteria, we made a sample of star forming regions suitable for revealing correlations between various star formation tracers.

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