* Astronomy

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RE: Distant Galaxies

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Massive galaxies

Blobrana · L

RE: Distant Galaxies

Blobrana · L

Hubble and ESO's VLT provide unique 3D views of remote galaxies
Astronomers have obtained exceptional 3D views of distant galaxies, seen when the Universe was half its current age, by combining the twin strengths of the NASA/ESA Hubble Space Telescope's acute eye, and the capacity of ESO's Very Large Telescope to probe the motions of gas in tiny objects. By looking at this unique "history book" of our Universe, at an epoch when the Sun and the Earth did not yet exist, scientists hope to solve the puzzle of how galaxies formed in the remote past.

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Colours of Quasars Reveal a Dusty Universe
The vast expanses of intergalactic space appear to be filled with a haze of tiny, smoke-like "dust" particles that dim the light from distant objects and subtly change their colours, according to a team of astronomers from the Sloan Digital Sky Survey (SDSS-II).

"Galaxies contain lots of dust, most of it formed in the outer regions of dying stars. The surprise is that we are seeing dust hundreds of thousands of light-years outside of the galaxies, in intergalactic space" - team leader Brice Ménard of the Canadian Institute for Theoretical Astrophysics.

The new findings are reported in a paper titled "Measuring the galaxy-mass and galaxy-dust correlations through magnification and reddening," submitted to the journal Monthly Notices of the Royal Astronomical Society, and posted today on the web site arXiv.org.
To discover this intergalactic dust, the team analysed the colours of distant quasars whose light passes in the vicinity of foreground galaxies on its way to the Earth.

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Title: Measuring the galaxy-mass and galaxy-dust correlations through magnification and reddening
Authors: Brice Ménard, Ryan Scranton, Masataka Fukugita, Gordon Richards

We present a simultaneous detection of gravitational magnification and dust reddening effects due to galactic halos and large-scale structure. The measurement is based on correlating the brightness of ~85,000 quasars at z>1 with the position of 20 million galaxies at z~0.3 derived from the Sloan Digital Sky Survey and is used to constrain the galaxy-mass and galaxy-dust correlation functions up to cosmological scales.
The presence of dust is detected from 20 kpc to several Mpc, and we find its projected density to follow: Sigma_dust ~ theta^-0.8, a distribution similar to mass. The amount of dust in galactic halos is found to be comparable to that in disks. On large scales its wavelength dependence is described by R_V=3.9±2.6, consistent with interstellar dust. We estimate the resulting opacity of the Universe as a function of redshift and find A_V~0.03 mag up to z=0.5. This, in turn, implies a cosmic dust density of Omega_dust ~ 5x10^-6, roughly half of which comes from dust in halos of ~L* galaxies.
We present magnification measurements, corrected for dust extinction, from which the galaxy-mass correlation function is inferred. The mean mass profile around galaxies is found to be Sigma ~ 30 (theta/arcmin)^-0.8 h M_sun/pc² up to a radius of 10 Mpc, in agreement with gravitational shear estimates.

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A chicken or egg question about the early universe has been answered by astronomers who say black holes came before galaxies.
Most if not all galaxies, including our own the Milky Way, are believed to have massive black holes at their cores. But did the black holes come first, helping to build galaxies by pulling material towards them, or did they arise in the centre of already formed galaxies?
According to new research focusing on the first billion years of the universe's history, the former is most likely to be true.

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Les galaxies ne sont pas des univers îles
Une équipe d'astronomes de l'Observatoire de Paris a établi de nouvelles contraintes sur les scénarios de formation des galaxies en étudiant la proportion en oxygène dans le gaz des galaxies lointaines. A partir de données issues du Very Large Telescope au Chili, l'équipe dirigée par F. Hammer a observé une centaine de galaxies massives situées à une distance comprise entre 4 et 8 milliards d'années-lumière; c'est à dire que l'on perçoit aujourd'hui la lumière que ces astres ont émis lorsque l'Univers avait la moitié de son âge actuel. Le contenu en oxygène du gaz a pu être mesuré avec une précision inégalée.

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University of Wisconsin-Madison students stumble on - a new galaxy

For five astronomy students this semester, a research project became a portal to worlds far removed from a campus library.
And now, instead of thinking up a title for their final paper, they're trying to come up with a name for the galaxy they found in a little known part of the universe.
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yawn

-- Edited by Blobrana at 13:22, 2008-11-28

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'Missing link' galaxies discovered
Astronomers at The University of Nottingham have identified a type of galaxy that could be the missing link in our understanding of galaxy evolution.
The STAGES study led by the Universitys Centre for Astronomy and Particle Theory examines galaxy evolution using images from the Hubble Space Telescope. A separate project Galaxy Zoo uses volunteers from the general public to classify galaxies. Both teams have identified a population of unusual red spiral galaxies that are setting out on the road to retirement after a lifetime of forming stars.
Astronomers place most normal galaxies into two camps according to their visual appearance: either disk-like systems like our own Milky Way, or round, rugby-ball shaped collections of stars known as ellipticals. In most cases, a galaxy's shape matches its colour; spiral galaxies appear blue because they are still vigorously forming hot young stars. Elliptical galaxies, on the other hand, are mostly old, dead and red, and tend to cluster together in crowded regions of space.
The Galaxy Zoo team examined the connection between the shapes and colours of over a million galaxies using images from the largest ever survey of the local universe the Sloan Digital Sky Survey and the help of hundreds of thousands of volunteers. A key ingredient to their success was reliably classifying the appearance of galaxies by actually looking at them, rather than relying on error-prone computer measurements. They found that many of the red galaxies in crowded regions are actually spiral galaxies, bucking the trend for red galaxies to be elliptical in shape.

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The deepest ultraviolet image of the Universe yet
This uniquely beautiful patchwork image, with its myriad of brightly coloured galaxies, shows the Chandra Deep Field South (CDF-S), arguably the most observed and best studied region in the entire sky. The CDF-S is one of the two regions selected as part of the Great Observatories Origins Deep Survey (GOODS), an effort of the worldwide astronomical community that unites the deepest observations from ground- and space-based facilities at all wavelengths from X-ray to radio. Its primary purpose is to provide astronomers with the most sensitive census of the distant Universe to assist in their study of the formation and evolution of galaxies.
The new image released by ESO combines data obtained with the VIMOS instrument in the U- and R-bands, as well as data obtained in the B-band with the Wide-Field Imager (WFI) attached to the 2.2 m MPG/ESO telescope at La Silla, in the framework of the GABODS survey.

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