Gaussian decomposition of H i surveys: IV. Galactic intermediate- and high-velocity clouds

被引：0

作者：

Haud, U. ^{[1
]}

机构：

[1] Tartu Observatory, 61602 Tõravere, Tartumaa, Estonia

来源：

Astronomy and Astrophysics | 2008年 / 483卷 / 02期

关键词：

Context. Traditionally intermediate- (IVC) and high-velocity hydrogen clouds (HVC) were defined to be concentrations of H I gas; with line-of-sight velocities that are inconsistent with data on the differential rotation of the Galaxy.Aims. We attempt to demonstrate that IVCs and HVCs can be identified from density enhancements in parameter distributions of Galactic H I 21 cm radio lines.Methods. To investigate the properties of the 21 cm radio lines; the profiles of The Leiden/Argentine/Bonn (LAB) Survey of Galactic H I are decomposed into Gaussian components using a fully automatic algorithm. We focus on some regions with an increased number of Gaussians in phase space; defined by the component central velocity () and the full width at the level of half maximum (FWHM). To separate the Gaussians responsible for the phase-space density enhancements; we model the width distributions of Gaussian components at equally-populated velocity intervals; using lognormal distributions.Results. We study the Gaussians; which parameters fall into the regions of the phase-space density enhancements at and; where the indexes indicate the half widths at the level of half maximum (HWHM) of the enhancements. The sky distribution of the Gaussians; corresponding to the first two concentrations; very well represents the sky distribution of HVCs; as obtained on the basis of the traditional definition of these objects. The Gaussians of the last concentration correspond to IVCs. Based on this identification; the division line between IVCs and HVCs can be drawn at about = |Vc| = 74 kms-1; and IVCs can be identified down to velocities of about = 24 kms-1. Traces of both IVCs and HVCs can also be seen in the sky distribution of Gaussians with FWHM 7.3 km s-1. In HVCs; these cold cores have small angular dimensions and low observed brightness temperatures . In IVCs; the cores are both larger and brighter.Conclusions. When neglecting the general decrease in the amount of gas at higher; the IVCs and HVCs are observed as distinctive maxima in the distribution of the Gaussians; representing the structure of the 21 cm radio lines of the Galactic H I. This definition is less dependant than the traditional one; on the differential rotation model of the Galaxy. The consideration of line-width information may enable IVCs and HVCs to be better distinguished from each other; and from the ordinary Galactic H I. © 2008 ESO;

D O I：

暂无

中图分类号：

学科分类号：

摘要：

Journal article (JA)

引用

下载

页码：461 / 469

共 50 条

[1] Gaussian decomposition of HI surveys - IV. Galactic intermediate- and high-velocity clouds
Haud, U.
ASTRONOMY & ASTROPHYSICS, 2008, 483 (02): : 461 - 469
[2] Distance limits to intermediate- and high-velocity clouds
Smoker, J. V.
Fox, A. J.
Keenan, F. P.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, 2011, 415 (02) : 1105 - 1118
[3] A SENSITIVE SEARCH FOR GALACTIC HIGH-VELOCITY H-I CLOUDS
MURPHY, EM
LOCKMAN, FJ
SAVAGE, BD
ASTROPHYSICAL JOURNAL, 1995, 447 (02): : 642 - 645
[4] Optical observations of three Galactic halo stars: evidence for cloudlets in intermediate- and high-velocity interstellar clouds
Lehner, N
Sembach, KR
Lambert, DL
Ryans, RSI
Keenan, FP
ASTRONOMY & ASTROPHYSICS, 1999, 352 (01) : 257 - 265
[5] Intermediate- and high-velocity clouds in the Milky Way - I. Covering factors and vertical heights
Lehner, Nicolas
Howk, J. Christopher
Marasco, Antonino
Fraternali, Filippo
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, 2022, 513 (03) : 3228 - 3240
[6] HIGH-VELOCITY CLOUDS AND H I SUPERSHELLS
HEILES, C
PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF THE PACIFIC, 1979, 91 (543) : 611 - 611
[7] High-velocity clouds and galactic evolution
VanWoerden, H
Schwarz, UJ
Peletier, RF
Wakker, BP
NEW LIGHT ON GALAXY EVOLUTION, 1996, (171): : 464 - 464
[8] THE GALACTIC FOUNTAIN OF HIGH-VELOCITY CLOUDS
BREGMAN, JN
ASTROPHYSICAL JOURNAL, 1980, 236 (02): : 577 - 591
[9] The high-velocity clouds: Galactic or intergalactic?
Van Woerden, H
Schwarz, UJ
Peletier, RF
Wakker, BP
Kalberla, PMW
GALAXY INTERACTIONS AT LOW AND HIGH REDSHIFT, 1999, (186): : 58 - 58
[10] VERY HIGH-VELOCITY H-I CLOUDS - AN INTER-GALACTIC POPULATION
GIOVANELLI, R
ASTRONOMICAL JOURNAL, 1981, 86 (10): : 1468 - 1479

← 1 2 3 4 5 →