Gemini: Cannibalistic Galaxy Reveals Its Monstrous Appetite

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Gemini: Cannibalistic Galaxy Reveals Its Monstrous Appetite

Post by bystander » Wed May 12, 2010 3:17 pm

Cannibalistic Galaxy Bends Light & Reveals Its Monstrous Appetite
Gemini Observatory - 12 May 2010
A newly discovered gravitational lens in a relatively nearby galaxy cluster is leading astronomers to conclude that the cluster hosts the most massive galaxy known in our local universe. The study also reaffirms that galactic cannibalism is one reason that this galaxy is so obese, tipping the scales at up to 30 trillion times the mass of our Sun.

The supermassive galaxy is located at the core of the galaxy cluster Abell 3827, which lies some 1.4 billion light-years away. This galaxy and hundreds of its smaller cluster companions are visible in a dramatic new image released by the Gemini Observatory. The image is part of an upcoming paper in The Astrophysical Journal Letters that reports on the study of the massive galaxy using the gravitational lens formed by its core (also visible in the image) to provide new measurements of the galaxy’s extreme mass.
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The exceptional galaxy was not simply born massive; it has grown by consuming its companions in perhaps the most extreme example of ongoing “galaxy cannibalism” known. “This unabashed cannibal is something of a messy eater, with the partially digested remains of at least four smaller galaxies still visible near its center,” said team member Michael West, astronomer at the European Southern Observatory who first observed this system more than a decade ago and says that he was immediately struck by the complex morphology of this giant cannibal galaxy (see West’s Astronomy Picture of the Day August 31, 1998). “Eventually this galaxy will grow even bigger judging by the number of nearby galaxies already within its gravitational grasp.”
Image
Gemini Legacy Image: R. Carrasco et al., Gemini Observatory/AURA
Central region of Abell 3827 as imaged using the Gemini Multi-Object Spectrograph on the Gemini South telescope in Chile. The central supermassive galaxy (ESO 146-IG 005) is clearly visible among its cluster companions as well as the remains of at least four nuclei that are being “digested” by the large galaxy. The central galaxy is thought to be the most massive galaxy in our local universe (out to about 1.5 billion light years). The field of view of this image is approximately 5 x 5 arcminutes and is a color composite made from g-, r- and i-band images combined and processed by Travis Rector (University of Alaska Anchorage). The inset (black on white image) is the single g-band image processed to reveal the gravitational lensed background galaxy arcs more clearly. Labeled on the inset are the most visible arcs from the closer background galaxy (z = 0.2 and labeled "A") and an arc from the more distant background galaxy (z = 0.4 and labeled "B").
Strong Gravitational Lensing by the Super-massive cD Galaxy in Abell 3827
We have discovered strong gravitational lensing features in the core of the nearby cluster Abell 3827 by analyzing Gemini South GMOS images. The most prominent strong lensing feature is a highly-magnified, ring-shaped configuration of four images around the central cD galaxy. GMOS spectroscopic analysis puts this source at z~0.2. Located ~20" away from the central galaxy is a secondary tangential arc feature which has been identified as a background galaxy with z~0.4. We have modeled the gravitational potential of the cluster core, taking into account the mass from the cluster, the BCG and other galaxies. We derive a total mass of (2.7 +- 0.4) x 10^13 Msun within 37 h^-1 kpc. This mass is an order of magnitude larger than that derived from X-ray observations. The total mass derived from lensing data suggests that the BCG in this cluster is perhaps the most massive galaxy in the nearby Universe.