The New Boundaries of the Galaxy Concept
Date Issued
2016
Author(s)
D'ONOFRIO, MAURO
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Struck, Curtis
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Bianchi, Luciana
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Sulentic, Jack W.
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Tully, Brent R.
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Longair, Malcolm S.
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Matteucci, Francesca
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Ciotti, Luca
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Einasto, Jaan
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Kroupa, Pavel
Abstract
In Chapter 6 we outlined the research strategies implemented for the studies of high
redshift galaxies, briefly addressed their structures, morphologies and star formation,
discussed the ancestor problem and touched the theme of the origin of the first
galaxies. With this Chapter we certainly enter in the modern view of galaxies, as
members of a big society. Up to now we have essentially described and characterized
the properties of nearby isolated galaxies, that are sufficiently relaxed to show
their almost unperturbed properties. However the history of this society, not differently
from the man society, is full of conflicts and battles for surviving. The present
knowledge of the cosmic web, of the hierarchical nature of the structures in the Universe,
and of the galaxy components have clearly demonstrated that gravitational
interactions, gas accretion and outflows, as well as merging events and gravitational
interactions are the true past history of galaxies. Galaxies change their structure and
morphology across the Hubble time and many of their observed properties today
depend on their past history, as well as in many cases on the environment in which
they evolved.
The title of this Chapter reflects our tentative effort of looking at galaxies along
this viewpoint. What are the current boundaries of the galaxy concept? In other
words, to what extent the structures we see today were present in the past and what
are their limits in mass, luminosity, size, stellar populations and chemical enrichment
across the Hubble time? What is the role of the dark matter? In which way the energetic phenomena observed in the galaxy nuclei and in SNe have changed
the properties of galaxies? The suspect is that we have built the concept of galaxies
looking only at their mature appearance and not at their whole life. Can we speak
of man describing only its adult phase and not considering his interaction with the
whole society?
The following interviews will clarify several things connected to this new point
of view. We start in Sec. 7.2 with a nice review of the effects of gravitational interactions
and merging that will highlight the progresses done by simulations since
the early Toomre’ pioneering work. We then address in Sec. 7.3 the problem of the
disk assembling and the remarkable extended UV disks found in many galaxies.
The current limits in the mass function of galaxies, from dwarfs to giants, are discussed
in Sec. 7.4. The various effects of the presence of an AGN at the center of
galaxies are analyzed in Sec. 7.5, while the activity of SNe is addressed in Sec. 7.6.
Finally, Sec. 7.7 provide the different point of views on the role and nature of the
dark matter.
Coverage
From the Realm of the Nebulae to Populations of Galaxies
Volume
435
Start page
509
Ads BibCode
2016ASSL..435..509D
Rights
restricted
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