Other
Scientific paper
Jan 2003
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2003eso..pres....2.&link_type=abstract
ESO Press Release, 01/2003
Other
Scientific paper
Subaru and VLT Join Forces in New Study of Virgo Galaxy Cluster [1]
Summary
At a distance of some 50 million light-years, the Virgo Cluster is the nearest galaxy cluster. It is located in the zodiacal constellation of the same name (The Virgin) and is a large and dense assembly of hundreds of galaxies.
The "intracluster" space between the Virgo galaxies is permeated by hot X-ray emitting gas and, as has become clear recently, by a sparse "intracluster population of stars".
So far, stars have been observed to form in the luminous parts of galaxies. The most massive young stars are often visible indirectly by the strong emission from surrounding cocoons of hot gas, which is heated by the intense radiation from the embedded stars. These "HII regions" (pronounced "Eitch-Two" and so named because of their content of ionized hydrogen) may be very bright and they often trace the beautiful spiral arms seen in disk galaxies like our own Milky Way.
New observations by the Japanese 8-m Subaru telescope and the ESO Very Large Telescope (VLT) have now shown that massive stars can also form in isolation, far from the luminous parts of galaxies. During a most productive co-operation between astronomers working at these two world-class telescopes, a compact HII region has been discovered at the very boundary between the outer halo of a Virgo cluster galaxy and Virgo intracluster space.
This cloud is illuminated and heated by a few hot and massive young stars. The estimated total mass of the stars in the cloud is only a few hundred times that of the Sun.
Such an object is rare at the present epoch. However, there may have been more in the past, at which time they were perhaps responsible for the formation of a fraction of the intracluster stellar population in clusters of galaxies. Massive stars in such isolated HII regions will explode as supernovae at the end of their short lives, and enrich the intracluster medium with heavy elements.
Observations of two other Virgo cluster galaxies, Messier 86 and Messier 84, indicate the presence of other isolated HII regions, thus suggesting that isolated star formation may occur more generally in galaxies. If so, this process may provide a natural explanation to the current riddle why some young stars are found high up in the halo of our own Milky Way galaxy, far from the star-forming clouds in the main plane.
The Virgo Cluster
ESO PR Photo 04a/03
ESO PR Photo 04a/03
[Preview - JPEG: 400 x 428 pix - 74k [Normal - JPEG: 800 x 855 pix - 408k] [Hi-Res - JPEG: 4252 x 4544 pix - 10.3M]
ESO PR Photo 04b/03
ESO PR Photo 04b/03
[Preview - JPEG: 433 x 400 pix - 60k [Normal - JPEG: 865 x 800 pix - 456k] [Hi-Res - JPEG: 3077 x 2847 pix - 4.2M]
Captions: PR Photo 04a/03 displays a sky field near some of the brighter galaxies in the Virgo Cluster. It was obtained in April 2000 with the Wide Field Imager (WFI) at the La Silla Observatory (exposure 6 x 5 min; red R-band; seeing 1.3 arcsec). The large elliptical galaxy at the centre is Messier 84; the elongated image of NGC 4388 (an active spiral galaxy, seen from the side) is in the lower left corner. The field measures 16.9 x 15.7 arcmin2. PR Photo 04b/03 shows a larger region of the Virgo cluster, with the galaxies Messier 86 (at the upper edge of the field, to the left of the centre), as well as Messier 84 (upper right) and NGC 4388 (just below the centre) that are also seen in PR Photo 04a/03. It is reproduced from a long-exposure Subaru Suprime-Cam image, obtained in the red light of ionized hydrogen (the H-alpha spectral line at wavelength 656.2 nm). In order to show the faintest possible hydrogen emitting objects embedded in the outskirts of bright galaxies, their smooth envelopes have been "subtracted" during the image processing. The field measures 34 x 27 arcmin2. Part of this sky field is shown in colour in PR Photo 04c/03.
Captions: PR Photo 04a/03 displays a sky field near some of the brighter galaxies in the Virgo Cluster. It was obtained in April 2000 with the Wide Field Imager (WFI) at the La Silla Observatory (exposure 6 x 5 min; red R-band; seeing 1.3 arcsec). The large elliptical galaxy at the centre is Messier 84; the elongated image of NGC 4388 (an active spiral galaxy, seen from the side) is in the lower left corner. The field measures 16.9 x 15.7 arcmin2. PR Photo 04b/03 shows a larger region of the Virgo cluster, with the galaxies Messier 86 (at the upper edge of the field, to the left of the centre), as well as Messier 84 (upper right) and NGC 4388 (just below the centre) that are also seen in PR Photo 04a/03. It is reproduced from a long-exposure Subaru Suprime-Cam image, obtained in the red light of ionized hydrogen (the H-alpha spectral line at wavelength 656.2 nm). In order to show the faintest possible hydrogen emitting objects embedded in the outskirts of bright galaxies, their smooth envelopes have been "subtracted" during the image processing. The field measures 34 x 27 arcmin2. Part of this sky field is shown in colour in PR Photo 04c/03.
The galaxies in the Universe are rarely isolated - they prefer company. Many are found within dense structures, referred to as galaxy clusters, cf. e.g., ESO PR Photo 16a/99.
The galaxy cluster nearest to us is seen in the direction of the zodiacal constellation Virgo (The Virgin), at a distance of approximately 50 million light-years. PR Photo 04a/03 (from the Wide Field Imager camera at the ESO La Silla Observatory) shows a small sky region near the centre of this cluster with some of the brighter cluster galaxies. PR Photo 04b/03 displays an image of a larger field (partially overlapping Photo 04a/03) in the light of ionized hydrogen - it was obtained by the Japanese 8.2-m Subaru telescope on Mauna Kea (Hawaii, USA). The field includes some of the large galaxies in this cluster, e.g., Messier 86, Messier 84 and NGC 4388. In order to show the faintest possible hydrogen emitting objects embedded in the outskirts of bright galaxies, their smooth envelopes have been "subtracted" during the image processing. This is why they look quite different in the two photos.
Clusters of galaxies are believed to have formed because of the strong gravitational pull from dark and luminous matter. The Virgo cluster is considered to be a relatively young cluster, because studies of the distribution of its member galaxies and X-ray investigations of hot cluster gas have revealed small "subclusters of galaxies" around the major galaxies Messier 87, Messier 86 and Messier 49. These subclusters are yet to merge to form a dense and smooth galaxy cluster.
The Virgo cluster is apparently cigar-shaped, with its longest dimension of about 10 million light-years near the line-of-sight direction - we see it "from the end".
Stars in intracluster space
Galaxy clusters are dominated by dark matter. The largest fraction of the luminous (i.e. "visible") cluster mass is made up of the hot gas that permeates all of the cluster. Recent observations of "intracluster" stars have confirmed that, in addition to the individual galaxies, the Virgo cluster also contains a so-called "diffuse stellar component", which is located in the space between the cluster galaxies.
The first hint of this dates back to 1951 when Swiss astronomer Fritz Zwicky (1898-1974), working at the 5-m telescope at Mount Palomar in California (USA), claimed the discovery of diffuse light coming from the space between the galaxies in another large cluster of galaxies, the Coma cluster. The brightness of this intracluster light is 100 times fainter than the average night-sky brightness on the ground (mostly caused by the glow of atoms in the upper terrestrial atmosphere) and its measurement is difficult even with present technology. We now know that this intracluster glow comes from individual stars in that region.
Planetary nebulae
More recently, astronomers have undertaken a new and different approach to detect the elusive intracluster stars. They now search for Sun-like stars in their final dying phase during which they eject their outer layers into surrounding space. At the same time they unveil their s
No affiliations
No associations
LandOfFree
Isolated Star-Forming Cloud Discovered in Intracluster Space does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with Isolated Star-Forming Cloud Discovered in Intracluster Space, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Isolated Star-Forming Cloud Discovered in Intracluster Space will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-1526813