Are Old Galaxies Really Red and Dead? - Leo Blitz (SETI Talks)
Δημοσιεύτηκε στις 30 Οκτ 2015
Galaxies
are broadly divided into two classes: spiral and elliptical. Unlike the
spirals, the ellipticals, often referred to as early-type galaxies, are
largely composed of old stars that give them a reddish color, They
typically have little interstellar material with which to form new
stars; these galaxies are often referred to as “red and dead.” We will
see, however, that a substantial fraction of these galaxies contain
surprising amounts of neutral hydrogen and these do form stars, albeit
at a reduced rate compared to their spiral cousins. Early-type galaxies
outside of clusters can be seen to be accreting gas from their
surroundings, which is the source of at least some of the gas fueling
star-formation taking place within them. In addition, the galaxies are
seen to contain super-massive black holes in their centers. The black
holes appear to be responsible for ejecting much of the gas that falls
into the nuclei of these galaxies, reenergizing the intergalactic
medium.
are broadly divided into two classes: spiral and elliptical. Unlike the
spirals, the ellipticals, often referred to as early-type galaxies, are
largely composed of old stars that give them a reddish color, They
typically have little interstellar material with which to form new
stars; these galaxies are often referred to as “red and dead.” We will
see, however, that a substantial fraction of these galaxies contain
surprising amounts of neutral hydrogen and these do form stars, albeit
at a reduced rate compared to their spiral cousins. Early-type galaxies
outside of clusters can be seen to be accreting gas from their
surroundings, which is the source of at least some of the gas fueling
star-formation taking place within them. In addition, the galaxies are
seen to contain super-massive black holes in their centers. The black
holes appear to be responsible for ejecting much of the gas that falls
into the nuclei of these galaxies, reenergizing the intergalactic
medium.
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