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Stephan's quintet

This image combines 24 separate images: 3 at each of 3 dithered positions, in each of B,V,R, and luminance filters of between 2-5 minutes. The observations were taken robotically with our first 1m telescope at McDonald Observatory, Texas.
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Title: The star formation efficiency in Stephan's Quintet intragroup regions
Authors: G. Natale, R. J. Tuffs, C. K. Xu, C. C. Popescu, J. Fischera, U. Lisenfeld, N. Lu, P. Appleton, M. Dopita, P.-A. Duc, Y. Gao, W. Reach, J. Sulentic, M. Yun

We investigated the star formation efficiency for all the dust emitting sources in Stephan's Quintet (SQ). We inferred star formation rates using Spitzer MIR/FIR and GALEX FUV data and combined them with gas column density measurements by various authors, in order to position each source in a Kennicutt-Schmidt diagram. Our results show that the bright IGM star formation regions in SQ present star formation efficiencies consistent with those observed within local galaxies. On the other hand, star formation in the intergalactic shock region seems to be rather inhibited.

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Title: New insights on Stephan's Quintet: exploring the shock in three dimensions
Authors: J. Iglesias-Páramo (1,2), L. López-Martín (3,4), J. M. Vílchez (1), V. Petropoulou (1), J. W. Sulentic (1) ((1) Instituto de Astrofísica de Andalucía - CSIC, Granada, Spain, (2) Centro Astronómico Hispano Alemán, Almería, Spain, (3) Instituto de Astrofísica de Canarias, Tenerife, Spain, (4) Universidad de La Laguna, Tenerife, Spain)

We carried out IFU optical spectroscopy on three pointings in and near the SQ shock. We used PMAS on the 3.5m Calar Alto telescope to obtain measures of emission lines that provide insight into physical properties of the gas. Severe blending of H\alpha\ and [NII]6548,6583A emission lines in many spaxels required the assumption of at least two kinematical components in order to extract fluxes for the individual lines. Main results from our study include: (a) detection of discrete emission features in the new intruder velocity range 5400-6000km/s showing properties consistent with HII regions, (b) detection of a low velocity component spanning the range 5800-6300km/s with properties resembling a solar metallicity shocked gas and (c) detection of a high velocity component at ~6600km/s with properties consistent with those of a low metallicity shocked gas. The two shocked components are interpreted as products of a collision between NGC7318b new intruder and a debris field in its path. This has given rise to a complex structure of ionised gas where several components with different kinematical and physical properties coexist although part of the original ISM associated with NGC7318b is still present and remains unaltered. Our observations suggest that the low velocity ionised component might have existed before the new intruder collision and could be associated with the NW-LV HI component of Williams et al. (2002). The high velocity ionised component might fill the gap between the HI complexes observed in SQ-A and NGC7319's tidal filament (NW-HV, Arc-N and Arc-S in Williams et al. 2002).

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A shockingly beautiful image of a galactic smash-up known as Stephan's Quintet highlights the powerful shock wave created by a cosmic bullet.
The compact galaxy group, 230 million light-years from Earth in the constellation Pegasus, is one of the favourite targets for astronomers studying gravitational interactions on a grand scale. It was discovered in 1877 by French astronomer Edouard Stephan.

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Stephan's Quintet

This beautiful image gives a new look at Stephan's Quintet, a compact group of galaxies discovered about 130 years ago and located about 280 million light years from Earth.
The curved, light blue ridge running down the center of the image shows X-ray data from the Chandra X-ray Observatory. Four of the galaxies in the group are visible in the optical image (yellow, red, white and blue) from the Canada-France-Hawaii Telescope. A labeled version identifies these galaxies (NGC 7317, NGC 7318a, NGC 7318b and NGC 7319) as well as a prominent foreground galaxy (NGC 7320) that is not a member of the group. The galaxy NGC 7318b is passing through the core of galaxies at almost 2 million miles per hour, and is thought to be causing the ridge of X-ray emission by generating a shock wave that heats the gas.

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Space scientists have snapped a spectacular cosmic pile-up - a collision involving four galaxies and many billions of stars. The crash scene lies 280 million light years from Earth in the constellation of Pegasus, the winged horse.

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This false-colour composite image of the Stephan's Quintet galaxy cluster clearly shows one of the largest shock waves ever seen (green arc), produced by one galaxy falling toward another at over a million miles per hour. It is made up of data from NASA's Spitzer Space Telescope and a ground-based telescope in Spain.

Four of the five galaxies in this image are involved in a violent collision 300 million light-years away in the constellation Pegasus, which has already stripped most of the hydrogen gas from the interiors of the galaxies. The centres of the galaxies appear as bright yellow-pink knots inside a blue haze of stars, and the galaxy producing all the turmoil, NGC7318b, is the left of two small bright regions in the middle right of the image. One galaxy, the large spiral at the bottom left of the image, is a foreground object and is not associated with the cluster.


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Position (2000): RA: 22h35m57s Dec: +33d57m36s

This image is composed of three data sets: near-infrared light (blue) and visible light called H-alpha (green) from the Calar Alto Observatory in Spain, operated by the Max Planck Institute in Germany; and 8-micron infrared light (red) from Spitzer's infrared array camera.

The titanic shock wave, larger than our own Milky Way galaxy, was detected by the ground-based telescope using visible-light wavelengths. It consists of hot hydrogen gas. As NGC7318b collides with gas spread throughout the cluster, atoms of hydrogen are heated in the shock wave, producing the green glow.
Spitzer pointed its infrared spectrograph at the peak of this shock wave (middle of green glow) to learn more about its inner workings. This instrument breaks light apart into its basic components. Data from the instrument are referred to as spectra and are displayed as curving lines that indicate the amount of light coming at each specific wavelength.
The Spitzer spectrum showed a strong infrared signature for incredibly turbulent gas made up of hydrogen molecules. This gas is caused when atoms of hydrogen rapidly pair-up to form molecules in the wake of the shock wave. Molecular hydrogen, unlike atomic hydrogen, gives off most of its energy through vibrations that emit in the infrared.
This highly disturbed gas is the most turbulent molecular hydrogen ever seen. Astronomers were surprised not only by the turbulence of the gas, but by the incredible strength of the emission. The reason the molecular hydrogen emission is so powerful is not yet completely understood.

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Stephan's Quintet: interacting galaxies


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Stephan's Quintet is located 300 million light-years away in the Pegasus constellation.

-- Edited by Blobrana at 04:21, 2006-03-03

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