ABOUT THIS IMAGE:

Summary:

This stunning image of NGC 1275 was taken using the NASA/ESA Hubble Space Telescope's Advanced Camera for Surveys in July and August 2006. It provides amazing detail and resolution of the fragile filamentary structures, which show up as a reddish lacy structure surrounding the central bright galaxy NGC 1275. These filaments are cool despite being surrounded by gas that is around 55 million degrees Celsius hot. They are suspended in a magnetic field which maintains their structure and demonstrates how energy from the central black hole is transferred to the surrounding gas.

By observing the filamentary structure, astronomers were, for the first time, able to estimate the magnetic field's strength. Using this information they demonstrated how the extragalactic magnetic fields have maintained the structure of the filaments against collapse caused by either gravitational forces or the violence of the surrounding cluster during their 100-million-year lifetime.

This is the first time astronomers have been able to differentiate the individual threads making up such filaments to this degree. Astonishingly, they distinguished threads a mere 200 light-years across. By contrast, the filaments seen here can be a gaping 200 000 light-years long. The entire image is approximately 260 000 light-years across.

Also seen in the image are impressive lanes of dust from a separate spiral galaxy. It lies partly in front of the giant elliptical central cluster galaxy and has been completely disrupted by the tidal gravitational forces within the galaxy cluster. Several striking filaments of blue newborn stars are seen crossing the image.

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NASA's Hubble Space Telescope has found the answer to a long-standing puzzle by resolving giant but delicate filaments shaped by a strong magnetic field around the active galaxy NGC 1275. It is the most striking example of the influence of these immense tentacles of extragalactic magnetic fields, say researchers.

At a distance of 230 million light-years, NGC 1275 is one of the closest giant elliptical galaxies and lies at the center of the Perseus Cluster of galaxies. It is an active galaxy, hosting a supermassive black hole at its core, which blows bubbles of radio-wave emitting material into the surrounding galactic cluster. Its most spectacular feature is the lacy filigree of gaseous filaments reaching out beyond the galaxy into the multi-million degree X-ray emitting gas that fills the cluster.

These filaments are the only visible-light manifestation of the intricate relationship between the central black hole and the surrounding cluster gas. They provide important clues about how giant black holes affect their surrounding environment.

A team of astronomers using the NASA/ESA Hubble Space Telescope Advanced Camera for Surveys have for the first time resolved individual threads of gas which make up the filaments. The amount of gas contained in a typical thread is around one million times the mass of our own Sun. They are only 200 light-years wide, are often surprisingly straight, and extend for up to 20,000 light-years. The filaments are formed when cold gas from the galaxy's core is dragged out in the wake of rising bubbles blown by the black hole.

It has been a challenge for astronomers to understand how the delicate structures withstood the hostile high-energy environment of the galaxy cluster for more than 100 million years. They should have heated up, dispersed, and evaporated over a very short period of time, or collapsed under their own gravity to form stars. Even more puzzling is the fact that they haven't been ripped apart by the strong tidal pull of gravity in the cluster's core.

A new study led by Andy Fabian from the University of Cambridge, UK, published in Nature on 21 August 2008 proposes that the magnetic fields hold the charged gas in place and resist forces that would distort the filaments. This skeletal structure has been able to contain and suspend these peculiarly long threads for over 100 million years. "We can see that the magnetic fields are crucial for these complex filaments - both for their survival and for their integrity", said Fabian.

The new Hubble data also allowed the strength of the magnetic fields in the filaments to be determined from their size. Thinner filaments are more fragile, requiring stronger magnetic fields for support. However, the finer the filaments, the more difficult they are to observe.

The filamentary system in NGC 1275 provides the most striking example of the workings of extragalactic magnetic fields so far and is a spectacular by-product of the complex interaction between the cluster gas and the supermassive black hole at the galaxy's heart. Similar networks of filaments are found around many other, even more remote, central cluster galaxies. They cannot be observed in anything like the detail of NGC 1275, so the team will apply the understanding gained here to interpret observations of these more distant galaxies.

Color:

This image is a composite of separate exposures made by the ACS instrument on the Hubble Space Telescope. Three filters were used to sample various broad wavelength ranges. The color results from assigning different hues (colors) to each monochromatic image. In this case, the assigned colors are:

F435W (B) blue      F550M (V) green      F625W (r) red

From Wikipedia:

NGC 1275 (also known as Perseus A or Caldwell 24) is a type 1.5 Seyfert galaxy located around 237 million light-years away in the direction of the constellation Perseus. NGC 1275 corresponds to the radio galaxy Perseus A and is situated near the center of the large Perseus Cluster of galaxies.

NGC 1275 consists of two galaxies, a central type-cD galaxy in the Perseus Cluster, and a so-called "high velocity system" (HVS) which lies in front of it. The HVS is moving at 3000 km/s towards the dominant system, and is believed to be merging with the Perseus Cluster. The HVS is not affecting the cD galaxy as it lies at least 200 thousand light years from it, however tidal interactions are disrupting it and ram-pressure stripping produced by its interaction with the intracluster medium of Perseus is stripping its gas as well as producing large amounts of star formation within it.

The central cluster galaxy contains a massive network of spectral line emitting filaments, which apparently are being dragged out by rising bubbles of relativistic plasma generated by the central active galactic nucleus. Long gaseous filaments made up of threads of gas stretch out beyond the galaxy, into the multimillion-degree, X-ray-emitting gas that fills the cluster. The amount of gas contained in a typical thread is approximately one million times the mass of our own Sun. They are only 200 light-years wide, are often very straight, and extend for up to 20,000 light-years.

The existence of the filaments poses a problem. As they are much cooler than the surrounding intergalactic cloud, it is unclear how they have existed for such a long time, or why they have not warmed, dissipated or collapsed to form stars. One possibility is that weak magnetic fields (about one-ten-thousandth the strength of Earth's field) exert enough force on the ions within the threads to keep them together.

NGC 1275 contains 13 billion solar masses of molecular hydrogen that seems to be infalling from Perseus' intracluster medium in a cooling flow, both feeding its active nucleus and fueling significant amounts of star formation.

A supermassive black hole with a mass 340 million times that of our Sun may be present in NGC 1275's center.