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Post Info TOPIC: Elliptical Galaxies
Blobrana


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Giant elliptical galaxies
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NASA's Hubble Finds Evidence of Galaxy Star Birth Regulated by Black-Hole Fountain

Astronomers have uncovered a unique process for how the universe's largest elliptical galaxies continue making stars long after their peak years of star birth. NASA's Hubble Space Telescope's exquisite high resolution and ultraviolet-light sensitivity allowed the astronomers to see brilliant knots of hot, blue stars forming along the jets of active black holes found in the centers of giant elliptical galaxies.
Combining Hubble data with observations from a suite of ground-based and space telescopes, two independent teams found that the black hole, jets, and newborn stars are all parts of a self-regulating cycle. High-energy jets shooting from the black hole heat a halo of surrounding gas, controlling the rate at which the gas cools and falls into the galaxy.
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Blobrana


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RE: Elliptical Galaxies
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Giant Galaxies Die from the Inside Out

Astronomers have shown for the first time how star formation in "dead" galaxies sputtered out billions of years ago. ESO's Very Large Telescope and the NASA/ESA Hubble Space Telescope have revealed that three billion years after the Big Bang, these galaxies still made stars on their outskirts, but no longer in their interiors. The quenching of star formation seems to have started in the cores of the galaxies and then spread to the outer parts. The results will be published in the 17 April 2015 issue of the journal Science.
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Blobrana


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Elliptical Galaxies: Chandra Helps Explain "Red and Dead Galaxies"

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NASA's Chandra X-ray Observatory has shed new light on the mystery of why giant elliptical galaxies have few, if any, young stars. This new evidence highlights the important role that supermassive black holes play in the evolution of their host galaxies.
Because star-forming activity in many giant elliptical galaxies has shut down to very low levels, these galaxies mostly house long-lived stars with low masses and red optical colors. Astronomers have therefore called these galaxies "red and dead". 
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Blobrana


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Title: Elliptical galaxy masses out to five effective radii: the realm of dark matter
Authors: A. J. Deason, V. Belokurov, N.W. Evans, I.G. McCarthy (IoA, Cambridge)

We estimate the masses of elliptical galaxies out to five effective radii using planetary nebulae and globular clusters as tracers. A sample of 15 elliptical galaxies with a broad variation in mass is compiled from the literature. A distribution function-maximum likelihood analysis is used to estimate the overall potential slope, normalisation and velocity anisotropy of the tracers. We assume power-law profiles for the potential and tracer density and a constant velocity anisotropy. The derived potential power-law indices lie in between the isothermal and Keplerian regime and vary with mass: there is tentative evidence that the less massive galaxies have steeper potential profiles than the more massive galaxies. We use stellar mass-to-light ratios appropriate for either a Chabrier/KTG (Kroupa, Tout & Gilmore) or Salpeter initial mass function to disentangle the stellar and dark matter components. The fraction of dark matter within five effective radii increases with mass, in agreement with several other studies. We employ simple models to show that a combination of star formation efficiency and baryon extent are able to account for this trend. These models are in good agreement with both our measurements out to five effective radii and recent SLACS measurements within one effective radii when a universal Chabrier/KTG initial mass function is adopted.

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Blobrana


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Title: Distances and stellar population properties for 12 elliptical galaxies
Author(s): Michele Cantiello, E. Brocato and M. Capaccioli

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Blobrana


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Elliptical galaxies are not "dead"

Initial results from research carried out as part of the Atlas3D project on two elliptical galaxies could, if they are confirmed, call into question the current model of the formation of galaxies. An international team of astronomers, including in particular CNRS, CEA, the CFHT, the Observatoire de Lyon, ENS de Lyon and Claude Bernard Lyon 1 et Paris-Diderot universities, are due to publish their initial observations in the journal Monthly Notices of The Royal Astronomical Society.
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Blobrana


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Elliptical galaxies much younger than previously thought?

The standard model for elliptical galaxies formation is challenged by a new result uncovered by an international team of astronomers from the Atlas3D collaboration. Team members from CNRS, CEA, CFHT, and the Observatoire de Lyon published in the scientific journal Monthly Notices of the Royal Astronomical Society the first results from their study on two elliptical galaxies exhibiting features characteristic of a fairly recent merging, suggesting they are five times younger than commonly thought.
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Blobrana


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ATLAS3D project
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The ATLAS3D project: Replacing the handle of Hubble's tuning fork

A team of 25 astronomers from Europe and Northern America, including ASTRON astronomers Morganti, Oosterloo, and Serra, has shown that many galaxies, which are normally classified as spheroid galaxies according to the 70 year old Hubble classification scheme, are in fact spiral galaxies. The so-called ATLAS3D team observed a sample of 260 galaxies with the SAURON spectrograph on the 4.2-meter William Herschel Telescope on La Palma, which allowed them to determine the movements of the stars in these carefully selected galaxies. The results are important because it gives astronomers more information about the way galaxies form.
The team proposed a revised scheme in which the vast majority of spheroid galaxies, also known as early-type galaxies, are close relatives of spiral galaxies and for this reason form a parallel sequence to them. The new paradigm highlights a much closer connection between early-type and spiral galaxies than previously thought, and this will need to be considered in future models of how galaxies form. The above results were presented in three ATLAS3D team papers which will appear this month on the journal Monthly Notices of the Royal Astronomical Society.

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Blobrana


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Elliptical Galaxies
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Most elliptical galaxies are 'like spirals'

The majority of 'elliptical' galaxies are not spherical but disc-shaped, resembling spiral galaxies such as our own Milky Way with the gas and dust removed, new observations suggest.
The results come from Atlas3D, a survey of all 260 early-type ('elliptical' and 'lenticular') galaxies in a well-defined volume of the nearby universe. Atlas3D shows a much closer link between 'elliptical' galaxies and spiral galaxies than previously thought. The findings are likely to change our ideas of how galaxies form and see astronomy text-books rewritten.
A report of the research, by the international Atlas3D team, is published in an upcoming issue of Monthly Notices of the Royal Astronomical Society.
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Title: A Fundamental Line for Elliptical Galaxies
Authors: Preethi Nair, Sidney van den Bergh, Roberto G. Abraham

Recent studies have shown that massive galaxies in the distant universe are surprisingly compact, with typical sizes about a factor of three smaller than equally massive galaxies in the nearby universe. It has been suggested that these massive galaxies grow into systems resembling nearby galaxies through a series of minor mergers. In this model the size growth of galaxies is an inherently stochastic process, and the resulting size-luminosity relationship is expected to have considerable environmentally-dependent scatter. To test whether minor mergers can explain the size growth in massive galaxies, we have closely examined the scatter in the size-luminosity relation of nearby elliptical galaxies using a large new database (Nair & Abraham 2010) of accurate visual galaxy classifications. We demonstrate that this scatter is much smaller than has been previously assumed, and may even be so small as to challenge the plausibility of the merger driven hierarchical models for the formation of massive ellipticals.

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