排序方式： 共有13条查询结果，搜索用时 15 毫秒
1.
2.
The SKA will revolutionise the study of the principles underlying star formation (SF), resolving interstellar cloud complexes which are the birthplaces of stars and answering such questions as which are the sufficient and necessary conditions for SF to commence. Also, massive SF is intimately related to stellar death. The SKA will be able to study the structure of the ISM at 100 pc resolution out to distances of up to 20 Mpc and will quantify the impact the demise of massive stars has on their environment. Importantly, the SKA will probe the transition region between ISM and IGM, linking star formation and stellar death in the disks of galaxies to faint HI structures further afield, such as “anomalous gas” and (Compact) High Velocity Clouds. Lastly, the superb sensitivity of the SKA will result in some hundred background sources per square degree against which HI absorption lines can be searched for, probing not only the relative importance of the different phases of the gas in galaxies but also the low density gas in the outskirts and between galaxies. 相似文献
3.
4.
E. Brinks E.D. Skillman R.J. Terlevich E. Terlevich 《Astrophysics and Space Science》1997,248(1-2):23-31
Neutral hydrogen is an important tracer of galactic dynamics. Hence, observations of the detailed structure and kinematics
of HI are vital in order to determine the relationship between AGN and their host galaxy.
We describe high resolution VLA emission line observations of NGC 1068 at about 600 pc linear resolution and 5.2 km s-1 velocity
resolution. We present the HI morphology of this Seyfert galaxy and discuss its peculiar rotation curve and speculate how
its shape might be related to the Seyfert activity. Related to this, we will highlight the pronounced HI ring within which
the tightly wound CO spiral arms are found, and discuss the high, up to 55 km s-1, velocity dispersions which are found there.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
5.
R. Auld R. F. Minchin J. I. Davies B. Catinella W. van Driel P. A. Henning S. Linder E. Momjian E. Muller K. O'Neil S. Sabatini S. Schneider G. Bothun L. Cortese M. Disney G. L. Hoffman M. Putman J. L. Rosenberg M. Baes W. J. G. de Blok A. Boselli E. Brinks N. Brosch J. Irwin I. D. Karachentsev V. A. Kilborn B. Koribalski K. Spekkens † 《Monthly notices of the Royal Astronomical Society》2006,371(4):1617-1640
6.
7.
High-resolution observations of the star forming dwarf galaxies Haro 21 and Markarian 314 are presented and are compared with a set of narrow band (H) CCD images. TheHi system related to Haro 21 measures about 12 kpc in diameter and is much more extended than the optical emission. The optical light follows that of an exponential disk and has a scale length of only 600 pc. TheHi distribution shows a lack of neutral gas near its centre where most of the H emission is found. The velocity field is regular and shows the characteristics of a disk in differential rotation. The rotation curve is rising out to the last measured point and the total mass is estimated to be about 1.5×1010
M
. This implies that Haro 21 is a galaxy which is dominated by Dark Matter.Partly based on observations collected at the European Southern Observatory, La Silla, Chile. 相似文献
8.
9.
Until recently, few unequivocal detections had been reported of the hot, X-ray emitting gas thought to be associated with
the large, coherent structures variously described as supershells or superbubbles in dwarf irregular (dIrr) galaxies. In this
contribution we report follow-up XMM-Newton and Chandra observations of our ROSAT detection of X-ray emission associated with the supergiant shell in the nearby dIrr galaxy IC 2574, a member of the M 81
group of galaxies. The spectral properties of the X-ray source suggest that we are dealing with a young (age < 2000 yr) supernova
remnant (SNR). This SNR is most likely one of the many supernovae which have exploded in that region and which have created
the impressive supergiant HI shell.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
10.
Jonathan Braine P.-A. Duc U. Lisenfeld V. Charmandaris O. Vallejo S. Leon E. Brinks 《Astrophysics and Space Science》2002,281(1-2):407-408
We investigate the process of galaxy formation as can be observed in the only currently forming galaxies - the so-called Tidal
Dwarf Galaxies, hereafter TDGs - through observations of the molecular gas detected via its CO (Carbon Monoxide) emission.
These objects are formed of material torn off of the outer parts of a spiral disk due to tidal forces in a collision between
two massive galaxies. Molecular gas is a key element in the galaxy formation process, providing the link between a cloud of
gas and a bona fide galaxy. We have detected CO in 8 TDGs (Braine, Lisenfeld, Duc and Leon, 2000: Nature
403, 867; Braine, Duc, Lisenfeld, Charmandaris, Vallejo, Leon and Brinks: 2001, A&A
378, 51), with an overall detection rate of 80%, showing that molecular gas is abundant in TDGs, up to a few 108
M
⊙. The CO emission coincides both spatially and kinematically with the HI emission, indicating that the molecular gas forms
from the atomic hydrogen where the HI column density is high. A possible trend of more evolved TDGs having greater molecular
gas masses is observed, in accord with the transformation of HI into H2. Although TDGs share many of the properties of small irregulars, their CO luminosity is much greater (factor ∼ 100) than
that of standard dwarf galaxies of comparable luminosity. This is most likely a consequence of the higher metallicity (≳sim
1/3 solar) of TDGs which makes CO a good tracer of molecular gas. This allows us to study star formation in environments ordinarily
inaccessible due to the extreme difficulty of measuring the molecular gas mass. The star formation efficiency, measured by
the CO luminosity per Hα flux, is the same in TDGs and full-sized spirals. CO is likely the best tracer of the dynamics of
these objects because some fraction of the HI near the TDGs may be part of the tidal tail and not bound to the TDG. Although
uncertainties are large for individual objects, as the geometry is unknown, our sample is now of eight detected objects and
we find that the ‘dynamical’ masses of TDGs, estimated from the CO line widths, seem not to be greater than the ‘visible’
masses (HI + H2 + a stellar component). Although higher spatial resolution CO (and HI) observations would help reduce the uncertainties,
we find that TDGs require no dark matter, which would make them the only galaxy-sized systems where this is the case. Dark
matter in spirals should then be in a halo and not a rotating disk. Most dwarf galaxies are dark matter-rich, implying that
they are not of tidal origin. We provide strong evidence that TDGs are self-gravitating entities, implying that we are witnessing the
ensemble of processes in galaxy formation: concentration of large amounts of gas in a bound object, condensation of the gas,
which is atomic at this point, to form molecular gas and the subsequent star formation from the dense molecular component.
This revised version was published online in September 2006 with corrections to the Cover Date. 相似文献