Observations of the spatial structure of interstellar hydrogen

1967 ◽  
Vol 31 ◽  
pp. 45-46
Author(s):  
Carl Heiles
Keyword(s):  
High Resolution ◽  
Spatial Structure ◽  
Velocity Dispersion ◽  
Temperature Variations

High-resolution 21-cm line observations in a region aroundlII= 120°,b11= +15°, have revealed four types of structure in the interstellar hydrogen: a smooth background, large sheets of density 2 atoms cm-3, clouds occurring mostly in groups, and ‘Cloudlets’ of a few solar masses and a few parsecs in size; the velocity dispersion in the Cloudlets is only 1 km/sec. Strong temperature variations in the gas are in evidence.

A Method of Dispersion Compensation Based on Warped Frequency Transform

2013 ◽  
Vol 718-720 ◽  
pp. 2062-2067 ◽  
Author(s):  
Shang Chen Fu ◽  
Zhen Jian Lv ◽  
Ding Ma ◽  
Li Hua Shi
Keyword(s):  
High Resolution ◽  
Velocity Dispersion ◽  
Lamb Waves ◽  
Group Velocity Dispersion ◽  
Dispersion Compensation ◽  
Imaging Method ◽  
Finite Element Software ◽  
Damage Imaging ◽  
Resolution Imaging ◽  
Multi Mode

The use of Lamb waves for structural health monitoring (SHM) has complicated by its multi-mode character and dispersion effect, which impacts the damage positioning and high-resolution imaging. The group velocity dispersion curves of Lamb waves can be employed to warp the frequency axis, and then to establish warped frequency transform (WFT) to process Lamb waves. In this paper, received signals are directly compensated with warped frequency transform to suppress dispersion, and a new imaging method is proposed based on warped frequency transform. The propagation of Lamb waves in damaged aluminum plate is simulated by finite element software ABAQUS, results show that warped frequency transform can effectively compensate dispersive wave-packets, and high-resolution damage imaging can be obtained by the proposed method.

scholarly journals Planetary architectures in interacting stellar environments

2020 ◽  
Vol 496 (2) ◽  
pp. 1453-1470 ◽  
Author(s):  
Yi-Han Wang ◽  
Rosalba Perna ◽  
Nathan W C Leigh
Keyword(s):  
High Resolution ◽  
Cross Section ◽  
Cross Sections ◽  
Velocity Dispersion ◽  
Planetary System ◽  
Star Clusters ◽  
Exoplanetary Systems ◽  
The Cross ◽  
Star Binary ◽  
Strong Scattering

ABSTRACT The discovery of exoplanetary systems has challenged some of the theories of planet formation, which assume unperturbed evolution of the host star and its planets. However, in star clusters the interactions with fly-by stars and binaries may be relatively common during the lifetime of a planetary system. Here, via high-resolution N-body simulations of star–planet systems perturbed by interlopers (stars and binaries), we explore the reconfiguration to the planetary system due to the encounters. In particular, via an exploration focused on the strong scattering regime, we derive the fraction of encounters that result in planet ejections, planet transfers, and collisions by the interloper star/binary, as a function of the characteristics of the environment (density, velocity dispersion), and for different masses of the fly-by star/binary. We find that binary interlopers can significantly increase the cross-section of planet ejections and collisions, while they only slightly change the cross-section for planet transfers. Therefore, in environments with high binary fractions, floating planets are expected to be relatively common, while in environments with low binary fractions, where the cross-sections of planet ejection and transfer are comparable, the rate of planet exchanges between two stars will be comparable to the rate of production of free-floating planets.

scholarly journals Investigation into the Origin of Age-Velocity dispersion Relation by High Resolution Simulation

2016 ◽  
Vol 11 (S321) ◽  
pp. 124-124
Author(s):  
Jun Kumamoto ◽  
Junichi Baba ◽  
Takayuki R. Saitoh
Keyword(s):  
Dispersion Relation ◽  
High Resolution ◽  
Velocity Dispersion ◽  
Resolution Simulation

AbstractWe focused on the stellar age-velocity dispersion relation (AVR). We performed the N-body/SPH simulations to investigate the origin of AVR. As a results, we found that AVR is not consistent with simple stellar heating.

scholarly journals High resolution infrared maps of IRAS galaxies

1991 ◽  
Vol 147 ◽  
pp. 411-412
Author(s):  
S. K. Ghosh ◽  
T. N. Rengarajan ◽  
R. P. Verma
Keyword(s):  
High Resolution ◽  
Spatial Structure ◽  
Maximum Entropy ◽  
Maximum Entropy Method ◽  
Entropy Method ◽  
The Cross

IRAS has provided infrared maps of a large number of galaxies. However the size of IRAS survey detectors is quite large (∼5′ in the cross-scan direction) and there is a need for improving the resolution of these maps. In order to understand the spatial structure of galaxies, we have generated high resolution maps of 18 large galaxies by deconvolving the IRAS pointed observations from survey detectors as well as from Chopped Photometric Channel (CPC) using Maximum Entropy Method (MEM).

scholarly journals Kinematic Masses of Super Star Clusters in NGC 1569

2002 ◽  
Vol 207 ◽  
pp. 471-473
Author(s):  
Andrea M. Gilbert ◽  
James R. Graham
Keyword(s):  
High Resolution ◽  
Velocity Dispersion ◽  
Dwarf Galaxy ◽  
Star Clusters ◽  
Stellar Velocity ◽  
Super Star Clusters ◽  
Ngc 1569

We summarize recent results from our study of the massive young super star clusters (SSCs) in the dwarf galaxy NGC 1569, and present new high-resolution NIRSPEC spectra that permit the measurement of a cluster's intrinsic stellar velocity dispersion. Thus we derive kinematic masses for the two brightest SSCs: 2.3 × 105 Msun for SSC B, and 3.9 × 105 and 4.4 × 105 Msun for the two components of SSC A.

scholarly journals A longslit spectroscopic survey of bulges in disc galaxies

2012 ◽  
Vol 10 (H16) ◽  
pp. 345-345
Author(s):  
Maximilian Fabricius ◽  
Roberto Saglia ◽  
David Fisher ◽  
Niv Drory ◽  
Ralf Bender ◽  
...  
Keyword(s):  
High Resolution ◽  
Velocity Dispersion ◽  
Low Resolution ◽  
Present Evidence ◽  
Counter Rotation ◽  
Two Systems ◽  
Velocity Dispersions ◽  
First Time ◽  
Disc Galaxies

AbstractWe use the Marcario Low Resolution Spectrograph (LRS) at the Hobby-Eberly-Telescope (HET) to study the kinematics of pseudobulges and classical bulges in 45 S0-Sc type galaxies in the nearby universe. Our high-resolution (instrumental σ ≈ 39 km s−1) spectra allo only to resolve the typical velocity dispersions of our targets but also to derive the h3 and h4 Gauss-Hermite moments. We demonstrate for the first time that purely kinematic diagnostics of the bulge dichotomy agree systematically with those based on Sérsic index. Low Sérsic index bulges have both increased rotational support (higher v/σ values) and on average lower central velocity dispersions. Pseudobulges have systematically shallower velocity dispersion profiles. The same correlation also holds when visual morphologies are used to diagnose bulge type. Finally, we present evidence for formerly undetected counter rotation in the two systems NGC 3945 and NGC 4736. With these, a total of 16% of the systems in or sample show signs for stellar counter rotation.

scholarly journals Substructure within galactic spiral arms as derived from studies at 21 cm

1959 ◽  
Vol 9 ◽  
pp. 355-359
Author(s):  
R. D. Davies
Keyword(s):  
Fine Structure ◽  
High Resolution ◽  
Velocity Dispersion ◽  
Detailed Structure ◽  
Hydrogen Line ◽  
Spiral Arms ◽  
Frequency Structure ◽  
Galactic Spiral ◽  
Spiral Arm

Detailed structure within the spiral arms of our Galaxy is suggested by hydrogen-line spectra taken with high resolution in frequency [1]. The spectra show much detail in each maximum (spiral arm). It is not clear, however, if this frequency structure refers to fine structure in depth or in velocity dispersion or in both. Fine structure in position and depth has been inferred from 21-cm drift curves taken across the nearby spiral arms. The results of three investigations will be discussed. Two have been published in some detail [2, 3] and will only be summarized here.

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