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Posts Tagged ‘dwarf galaxies’

NASA’s Hubble And Chandra Find Evidence For Densest Nearby Galaxy

September 24, 2013 Leave a comment

The densest galaxy in the nearby part of the Universe may have been found. Packed with an extraordinary number of stars, this unusual galaxy is providing astronomers with clues to its intriguing past and how it fits into the galactic evolutionary chain.

The galaxy, known as M60-UCD1, is a type of “ultra-compact dwarf galaxy”. It was discovered with NASA’s Hubble Space Telescope and follow-up observations were done with NASA’s Chandra X-ray Observatory and ground-based optical telescopes.

Observations from the W. M. Keck Observatory on the summit of Mauna Kea, Hawaii, characterized it as the most luminous known galaxy of its type and one of the most massive, weighing 200 million times more than our Sun.

What makes M60-UCD1 so remarkable is that about half of this mass is found within a radius of only about 80 light years. This would make the density of stars about 15,000 times greater than found in Earth’s neighborhood in the Milky Way, meaning that the stars are about 25 times closer.

Link To Full Story.

NGC 602: Taken Under The “Wing” Of The Small Magellanic Cloud


Credit: X-ray: NASA/ CXC/ Univ.Potsdam/ L.Oskinova et al; Optical: NASA/STScI; Infrared: NASA/JPL-Caltech

Credit: X-ray: NASA/ CXC/ Univ.Potsdam/ L.Oskinova et al; Optical: NASA/STScI; Infrared: NASA/JPL-Caltech

The Small Magellanic Cloud (SMC) is one of the Milky Way’s closest galactic neighbors. Even though it is a small, or so-called dwarf galaxy, the SMC is so bright that it is visible to the unaided eye from the Southern Hemisphere and near the equator. Many navigators, including Ferdinand Magellan who lends his name to the SMC, used it to help find their way across the oceans.

Modern astronomers are also interested in studying the SMC (and its cousin, the Large Magellanic Cloud), but for very different reasons. Because the SMC is so close and bright, it offers an opportunity to study phenomena that are difficult to examine in more distant galaxies.

New Chandra data of the SMC have provided one such discovery: the first detection of X-ray emission from young stars with masses similar to our Sun outside our Milky Way galaxy. The new Chandra observations of these low-mass stars were made of the region known as the “Wing” of the SMC. In this composite image of the Wing the Chandra data is shown in purple, optical data from the Hubble Space Telescope is shown in red, green and blue and infrared data from the Spitzer Space Telescope is shown in red.

Full Story: http://www.chandra.harvard.edu/photo/2013/ngc602/

Where Are All The Dwarfs?

February 7, 2013 Leave a comment

Cosmic Web Stripping, Visualization Credits: Alejandro Benitez Llambay

Cosmic Web Stripping, Visualization Credits: Alejandro Benitez Llambay

Galaxies and matter in the universe clump in an intricate network of filaments and voids, known as the Cosmic Web. Computer experiments on massive supercomputers have shown that in such a Universe a huge number of small “dwarf” galaxies weighing just one thousandth of the Milky Way should have formed in our cosmic neighbourhood. Yet only a handful of these galaxies are observed orbiting around the Milky Way. The observed scarcity of dwarf galaxies is a major challenge to our understanding of galaxy formation.

An international team of researchers has studied this issue within the Constrained Local UniversE Simulations project (CLUES). The CLUES simulations use the observed positions and peculiar velocities of galaxies within Tens of Millions of light years of the Milky Way to accurately simulate the local environment of the Milky Way. “The main goal of this project is to simulate the evolution of the Local Group – the Andromeda and Milky Way galaxies and their low-mass neighbours – within their observed large scale environment”, said Stefan Gottlöber of the Leibniz Institute for Astrophysics Potsdam.

Analysing the CLUES simulations, the astronomers have now found that some of the far-out dwarf galaxies in the Local Group move with such high velocities with respect to the Cosmic Web that most of their gas can be stripped and effectively removed.

Full Story: http://www.aip.de/en/news/press/dwarfs

Nearby Dwarf Galaxy And Possible Protogalaxy Discovered: Optical And Radio Telescopes Lead To Finds, Reconstruction Of Intergalactic Traffic Jam

January 18, 2013 Leave a comment

Peering deep into the dim edges of a distorted pinwheel galaxy in the constellation Ursa Major (the Great Bear), astronomers at Case Western Reserve University and their colleagues have discovered a faint dwarf galaxy and another possible young dwarf caught before it had a chance to form any stars.

Within the faint trails of intergalactic traffic, the researchers also found more evidence pointing to two already known dwarf galaxies as probable forces that pulled the pinwheel-shaped disk galaxy known as M101 out of shape.

M101 is the dominant member in a group of 15 galaxies in Ursa Major. Most galaxies reside in such small-group environments, which means the factors shaping M101 are likely the same shaping most galaxies throughout the universe, the researchers say.

Full Story: http://blog.case.edu/think/2013/01/11/nearby_dwarf_galaxy_and_possible_protogalaxy_discovered_optical_and_radio_telescopes_lead_to_finds_reconstruction_of_intergalactic_traffic_jam

Most Distant Dwarf Galaxy Detected

January 18, 2012 Leave a comment

Credit: D. Lagattuta / W. M. Keck Observatory

Scientists have long struggled to detect the dim dwarf galaxies that orbit our own galaxy. So it came as a surprise on Jan. 18 when a team of astronomers using Keck II telescope’s adaptive optics has announced the discovery of a dwarf galaxy halfway across the universe.

The new dwarf galaxy found by MIT’s Dr. Simona Vegetti and colleagues is a satellite of an elliptical galaxy almost 10 billion light-years away from Earth. The team detected it by studying how the massive elliptical galaxy, called JVAS B1938 + 666, serves as a gravitational lens for light from an even more distant galaxy directly behind it. Their discovery was published in the Jan. 18 online edition of the journal Nature.

Like all supermassive elliptical galaxies, JVAS B1938 + 666’s gravity can deflect light passing by it. Often the light from a background galaxy gets deformed into an arc around the lens galaxy, and sometimes what’s called an Einstein ring. In this case, the ring is formed mainly by two lensed images of the background galaxy. The size, shape and brightness of the Einstein ring depends on the distribution of mass throughout the foreground lensing galaxy.

Full Story: http://keckobservatory.org/news/most_distant_dwarf_galaxy_detected/

Ultra-Compact Dwarf Galaxies Are Bright Star Clusters

December 19, 2011 Leave a comment

Astronomy & Astrophysics is publishing a new statistical study of the so-called ‘ultra-compact dwarf galaxies’ (UCDs), which are still mysterious objects. A team of astronomers has investigated how many of these UCDs exist in nearby galaxy clusters and groups. They show that the properties of UCDs match those of bright star clusters.

Astronomy & Astrophysics is publishing the results of a detailed investigation of how many ‘ultra-compact dwarf galaxies’ (UCDs) can be found in nearby galaxy clusters. UCDs were recognized as a populous and potentially distinct class of stellar systems about a decade ago. But they are still mysterious objects that are characterized by a compact morphology (30-300 light-years in size) and high masses (more than one million solar masses). More generally, their properties (e.g., their size, shape, or luminosity) are similar to those of both star clusters and dwarf galaxies. Several hundred UCDs have been found to date. Two main formation channels for these puzzling objects have been proposed so far. UCDs might either be very massive star clusters or be ‘normal’ dwarf galaxies transformed by tidal effects.

S. Mieske, M. Hilker, and I. Misgeld (ESO) present a statistical study of the UCD population: they define new statistical tools that relate the number of UCDs to the total luminosity of their host environment. This allows them to use statistical arguments to test the hypothesis that UCDs are bright star clusters. They predict that if UCDs are bright star clusters, we would expect to find only one or two UCDs around the Milky Way, which corresponds to what is seen, as omega Centauri is the only Milky Way satellite that can be considered a UCD.

Full Story: http://www.aanda.org/index.php?option=com_content&task=view&id=788&Itemid=277&lang=en_GB.utf8%2C+en_GB.UT