High Velocity Clouds: Galactic or Extragalactic?
نویسندگان
چکیده
منابع مشابه
Compact High Velocity Clouds
We summarize the observed properties of the CHVC population, which provide strong evidence for source distances in the range 200– 1000 kpc. At these distances, the population corresponds to strongly dark-matter dominated sub-dwarf galaxies still accreting onto the more massive Local Group systems. Recent searches for faint associated stellar populations have revealed red-giant candidates for wh...
متن کاملLate Gas Accretion onto Primordial Minihalos: a Model for Leo T and Extragalactic High-velocity Clouds
In this letter we show that primordial minihalos with vcir < 20 km s −1 stop accreting gas after reionization, as is usually assumed, but in virtue of their increasing concentration and the decreasing temperature of the intergalactic medium as redshift decreases, they have a recent phase of gas accretion and possibly star formation. We expect that some pre-reionization fossils that evolved on t...
متن کاملHighly Ionized High Velocity Clouds
We have recently used the Hubble Space Telescope to study a pair of high velocity clouds in the direction of Mrk 509 that have unusual ionization properties. They exhibit strong C iv absorption with little or no low ion absorption or H i 21 cm emission. As the closest known analog to the outer diffuse halos of damped Lyα absorbers and the low N(H i) metal line absorption systems seen in the spe...
متن کاملHighly Ionized High Velocity Clouds: Intergalactic Gas in the Local Group or Distant Gas in the Galactic Halo?
In the course of our studies of the gaseous halo surrounding the Milky Way, we have recently identified several high velocity (VLSR < -100 km s ) clouds in the directions of Mrk 509 and PKS 2155-304 that have unusual ionization properties. The clouds exhibit strong C IV absorption with little or no detectable low ion (C II, Si II) absorption or H I 21 cm emission down to very sensitive levels. ...
متن کاملCompact High–velocity Clouds at High Resolution
Six examples of the compact, isolated high–velocity clouds catalogued by Braun & Burton (1999) and identified with a dynamically cold ensemble of primitive objects falling towards the barycenter of the Local Group have been imaged with the Westerbork Synthesis Radio Telescope; an additional ten have been imaged with the Arecibo telescope. The imaging reveals a characteristic core/halo morpholog...
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ژورنال
عنوان ژورنال: Symposium - International Astronomical Union
سال: 1978
ISSN: 0074-1809
DOI: 10.1017/s0074180900143918