scholarly journals Systematically Peculiar Molecular Composition in M 82: Regarding the Formation Mechanisms

2005 ◽  
Vol 13 ◽  
pp. 875-878 ◽  
Author(s):  
S. Takano ◽  
N. Nakai ◽  
K. Kawaguchi ◽  
T Takano ◽  
P. Schilke ◽  
...  
Keyword(s):  
High Temperature ◽  
Molecular Composition ◽  
Formation Mechanisms ◽  
Starburst Galaxy ◽  
Surface Formation ◽  
Nearby Galaxies ◽  
Grain Surface

AbstractA systematically peculiar molecular composition has been found in a nearby starburst galaxy M 82. Molecules related to grain surface formation and to production reactions favorable at high-temperature are deficient in M 82 among nearby galaxies with rich gas. These molecules are SO, SiO, NH3, HNCO, CH3OH, and CH3CN. Possible reasons for this peculiarity are discussed.

scholarly journals Hydroxyl, water, ammonia, carbon monoxide and neutral carbon towards the Sgr A complex

2013 ◽  
Vol 9 (S303) ◽  
pp. 97-99
Author(s):  
R. Karlsson ◽  
Aa. Sandqvist ◽  
Å. Hjalmarson ◽  
A. Winnberg ◽  
K. Fathi ◽  
...  
Keyword(s):  
Carbon Monoxide ◽  
High Temperature ◽  
Open Access ◽  
Gas Phase ◽  
Combined Action ◽  
Circumnuclear Disk ◽  
Sgr A ◽  
Grain Surface ◽  
Very High ◽  
High Temperature Gas

AbstractWe observed Hydroxyl, water, ammonia, carbon monoxide and neutral carbon towards the +50 km s−1 cloud (M−0.02−0.07), the circumnuclear disk (CND) and the +20 km s−1 (M−0.13−0.08) cloud in the Sgr A complex with the VLA, Odin and SEST. Strong OH absorption, H2O emission and absorption lines were seen at all three positions. Strong C18O emissions were seen towards the +50 and +20 km s−1 clouds. The CND is rich in H2O and OH, and these abundances are considerably higher than in the surrounding clouds, indicating that shocks, star formation and clump collisions prevail in those objects. A comparison with the literature reveals that it is likely that PDR chemistry including grain surface reactions, and perhaps also the influences of shocks has led to the observed abundances of the observed molecular species studied here. In the redward high-velocity line wings of both the +50 and +20 km s−1 clouds and the CND, the very high H2O abundances are suggested to be caused by the combined action of shock desorption from icy grain mantles and high-temperature, gas-phase shock chemistry. Only three of the molecules are briefly discussed here. For OH and H2O three of the nine observed positions are shown, while a map of the C18O emission is provided. An extensive paper was recently published with Open Access (Karlsson et al. 2013, A&A 554, A141).

Formation Mechanisms of Iron Oxide and Iron Sulfide at High Temperature in Aqueous H2S Corrosion Environment

2018 ◽  
Vol 165 (3) ◽  
pp. C171-C179 ◽  
Author(s):  
Shujun Gao ◽  
Bruce Brown ◽  
David Young ◽  
Srdjan Nesic ◽  
Marc Singer
Keyword(s):  
High Temperature ◽  
Iron Oxide ◽  
Iron Sulfide ◽  
Formation Mechanisms ◽  
H2s Corrosion

scholarly journals High-Temperature Chemistry in External Galaxies

2017 ◽  
Vol 13 (S332) ◽  
pp. 25-36 ◽  
Author(s):  
Nanase Harada
Keyword(s):  
Black Holes ◽  
High Temperature ◽  
High Sensitivity ◽  
Cosmic Ray ◽  
Chemical Compositions ◽  
X Ray ◽  
Chemical Models ◽  
External Galaxies ◽  
Nearby Galaxies ◽  
High Temperature Chemistry

AbstractIn external galaxies, some galaxies have higher activities of star formation and central supermassive black holes. The interstellar medium in those galaxies can be heated by different mechanisms such as UV-heating, X-ray heating, cosmic-ray heating, and shock/mechanical heating. Chemical compositions can also be affected by those heating mechanisms. Observations of many molecular species in those nearby galaxies are now possible with the high sensitivity of Atacama Large Millimeter/sub-millimeter Array (ALMA). Here I cover different chemical models for those heating mechanisms. In addition, I present recent ALMA results of extragalactic astrochemistry including our results of a face-on galaxy M83 and an infrared-luminous merger NGC 3256.

scholarly journals The intrinsic shape of bulges in the CALIFA survey

2018 ◽  
Vol 609 ◽  
pp. A132 ◽  
Author(s):  
L. Costantin ◽  
J. Méndez-Abreu ◽  
E. M. Corsini ◽  
M. C. Eliche-Moral ◽  
T. Tapia ◽  
...  
Keyword(s):  
Formation Mechanisms ◽  
Massive Galaxies ◽  
Barred Galaxies ◽  
Total Luminosity ◽  
Prolate Spheroids ◽  
Intrinsic Shape ◽  
Binary Mergers ◽  
Crucial Information ◽  
Nearby Galaxies ◽  
Heterogeneous Class

Context.The intrinsic shape of galactic bulges in nearby galaxies provides crucial information to separate bulge types.Aims.We aim to derive accurate constraints to the intrinsic shape of bulges to provide new clues on their formation mechanisms and set new limitations for future simulations.Methods.We retrieved the intrinsic shape of a sample of CALIFA bulges using a statistical approach. Taking advantage of GalMer numerical simulations of binary mergers we estimated the reliability of the procedure. Analyzing thei-band mock images of resulting lenticular remnants, we studied the intrinsic shape of their bulges at different galaxy inclinations. Finally, we introduced a new (B/A,C/A) diagram to analyze possible correlations between the intrinsic shape and the properties of bulges.Results.We tested the method on simulated lenticular remnants, finding that for galaxies with inclinations of 25° ≤θ≤ 65° we can safely derive the intrinsic shape of their bulges. We found that our CALIFA bulges tend to be nearly oblate systems (66%), with a smaller fraction of prolate spheroids (19%), and triaxial ellipsoids (15%). The majority of triaxial bulges are in barred galaxies (75%). Moreover, we found that bulges with low Sérsic indices or in galaxies with low bulge-to-total luminosity ratios form a heterogeneous class of objects; additionally, bulges in late-type galaxies or in less massive galaxies have no preference for being oblate, prolate, or triaxial. On the contrary, bulges with high Sérsic index, in early-type galaxies, or in more massive galaxies are mostly oblate systems.Conclusions.We concluded that various evolutionary pathways may coexist in galaxies, with merging events and dissipative collapse being the main mechanisms driving the formation of the most massive oblate bulges and bar evolution reshaping the less massive triaxial bulges.

Surface Formation Mechanisms in Selective Laser Melting of Cobalt-Chromium-Molybdenum Powder

2020 ◽  
Vol 839 ◽  
pp. 73-78
Author(s):  
Alexander A. Saprykin ◽  
Yuriy P. Sharkeev ◽  
Natalya A. Saprykina ◽  
Egor A. Ibragimov
Keyword(s):  
Selective Laser Melting ◽  
Marangoni Effect ◽  
Powdered Material ◽  
Formation Mechanisms ◽  
Cobalt Chromium ◽  
Laser Melting ◽  
Movement Velocity ◽  
Surface Formation ◽  
Preheating Temperature ◽  
Cobalt Chromium Molybdenum

Selective laser melting (SLM) is a manufacturing technology of metal parts of any shapes with target mechanical properties by means of laser melting. This paper discusses the effect of SLM parameters: laser output power, laser movement velocity, scanning pitch and preheating temperature of a powdered material on surface formation mechanism, namely, its physical configuration when melting cobalt-chromium-molybdenum powdered material Со28Cr3Mo. The study points at structural differences of melted surfaces even under identical process parameters. Several types of surface formation are identified, e.g. homogenous melt, coagulated particles, and shapeless particles. Vapor pressure, Marangoni effect, and heat effect of a melted powder are stated to be key reasons for rough surface. This research is of high importance for understanding the effect of SLM parameters on formation of a target quality surface, positive stability and repeatable accuracy of the process.

scholarly journals Molecular Abundances in Comets

1994 ◽  
Vol 160 ◽  
pp. 313-326 ◽  
Author(s):  
Jacques Crovisier
Keyword(s):  
Remote Sensing ◽  
Critical Review ◽  
Molecular Composition ◽  
Formation Mechanisms ◽  
Basic Information ◽  
Molecular Abundances

The molecular composition of cometary volatiles is a basic information on the nature of comets and a clue to their formation mechanisms. It is only recently that direct identifications of cometary volatiles were obtained through in situ exploration as well as from remote sensing at UV, IR and radio wavelengths. An inventory of known cometary volatiles is presented, with a critical review of the evaluations of their abundances.

scholarly journals New Formation Mechanisms of Pores and Cracks in Micro-arc Oxidation Coatings on 6061 Aluminum Alloy with High Temperature Oxide Prefab Film

2021 ◽  
Vol 27 (1) ◽  
pp. 37-41
Author(s):  
Guo-rui WU ◽  
Dong-dong WANG ◽  
Xin-tong LIU ◽  
Mingjia WANG ◽  
Dong CHEN ◽  
...  
Keyword(s):  
Aluminum Alloy ◽  
High Temperature ◽  
Phase Interface ◽  
Oxide Phase ◽  
Formation Mechanisms ◽  
Coating Materials ◽  
6061 Aluminum Alloy ◽  
High Temperature Oxide ◽  
Micro Arc Oxidation ◽  
Temperature Oxide

Prior to micro-arc oxidation (MAO) treatment, a layer of high temperature oxide (HTO) prefab film was fabricated on the surface of 6061 aluminum alloy specimens. The formation mechanisms of the cracks and pores in the MAO coatings were investigated by means of Mg element as the tracer. The results showed that there were several different formation mechanisms for the pores and cracks formed in the MAO coatings as follows. Some of pores were attributed to the residual micro-discharge channels, and the others were attributed to the residual uncovered concave regions locating among the surrounding convex regions. The difference in oxide phase composition caused by the compositional fluctuations in the coating weakened the bond strength at the phase interface and resulted in forming cracks between every two convex regions. Some of cracks were resulted from the solidification and shrinkage of molten coating materials, and the others were resulted from the poor connection between every two convex regions. The surface morphology and the content of each element of the MAO coating were determined using scanning electron microscopy (SEM) equipped with energy dispersive X-ray spectroscopy (EDS).

scholarly journals Preservation or piracy: Diagnosing low-relief, high-elevation surface formation mechanisms: REPLY

Geology ◽  
2017 ◽  
Vol 45 (8) ◽  
pp. e422-e422 ◽  
Author(s):  
Kelin X. Whipple ◽  
Roman A. DiBiase ◽  
William B. Ouimet ◽  
Adam M. Forte
Keyword(s):  
High Elevation ◽  
Formation Mechanisms ◽  
Surface Formation

scholarly journals Booms and Busts: the Burstiness of Star Formation in Nearby Dwarf Galaxies

2010 ◽  
Vol 27 (3) ◽  
pp. 234-241 ◽  
Author(s):  
A. A. Cole
Keyword(s):  
Galaxy Evolution ◽  
Local Group ◽  
Dwarf Galaxies ◽  
Starburst Galaxy ◽  
Ic 10 ◽  
Irregular Galaxies ◽  
Magnitude Diagram ◽  
Nearby Galaxies ◽  
Dwarf Irregular Galaxies ◽  
The Universe

AbstractIn this review I summarise recent advances in our understanding of the importance of starburst events to the evolutionary histories of nearby galaxies. Ongoing bursts are easily diagnosed in emission-line surveys, but assessing the timing and intensity of fossil bursts requires more effort, usually demanding color–magnitude diagrams or spectroscopy of individual stars. For ages older than ∼1 Gyr, this type of observation is currently limited to the Local Group and its immediate surroundings. However, if the Local Volume is representative of the Universe as a whole, then studies of the age and metallicity distributions of star clusters and resolved stellar populations should give statistical clues as to the frequency and importance of bursts to the histories of galaxies in general. Based on starburst statistics in the literature and synthetic colour-magnitude diagram studies of Local Group galaxies, I attempt to distinguish between systemic starbursts that strongly impact galaxy evolution and stochastic bursts that can appear impressive but are ultimately of little significance on gigayear timescales. As a specific case, it appears as though IC 10, the only starburst galaxy in the Local Group, falls into the latter category and is not fundamentally different from other nearby dwarf irregular galaxies.

Sign in / Sign up

Export Citation Format

Share Document