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Posts: 131433
Date:
PGC 26034
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Title: Superwind evolution: the young starburst-driven wind galaxy NGC 2782
Author: Jimena Bravo-Guerrero (1), Ian R. Stevens (2) ((1) Universidad Iberoamericana, Mexico, (2) University of Birmingham, UK)

We present results from a 30 ksec Chandra observation of the important starburst galaxy NGC 2782, covering the 0.3-10keV energy band. We find evidence of a superwind of small extent, that is likely in an early stage of development. We find a total of 27 X-ray point sources within a region of radius 2D25 of the galaxy centre and which are likely associated with the galaxy. Of these, 13 are ULXs (LX \geq 10^39 ergs^-1) and a number have likely counterparts. The X-ray luminosities of the ULX candidates are 1.2 - 3.9 x 10^39 ergs^-1. NGC2782 seems to have an unusually large number of ULXs. Central diffuse X-ray emission extending to ~ 3kpc from the nuclear region has been detected. We also find an X-ray structure to the south of the nucleus, coincident with H{\alpha} filaments and with a 5 GHz radio source. We interpret this as a blow-out region of a forming superwind. This X-ray bubble has a total luminosity (0.3-10 keV) of 5 x 10^39ergs^-1 (around 15% of the total luminosity of the extended emission), and an inferred wind mass of 1.5 x 10^6 solar masses. We also discuss the nature of the central X-ray source in NGC2782, and conclude that it is likely a low-luminosity AGN (LLAGN), with a total X-ray luminosity of LX=6 x 10^40 ergs^-1 with strong Fe line emission at 6.4 keV.

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Posts: 131433
Date:
Arp 215
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NGC 2782 (also Arp 215, UGC 4862, MCG +07-19-36, and PGC 26034) is a magnitude +11.4 face-on barred spiral galaxy located 122 million light-years away in the constellation Lynx.
The galaxy is a Seyfert galaxy with a small but bright nucleus where new stars are forming.

NGC 2782 was discovered by German-British astronomer William Herschel using a 47.5 cm (18.7 inch) f/13 speculum reflector at Windsor Road, Slough, on the 18th March 1787.

The galaxy hosted supernova 1994ak

Right ascension 09h 14m 05.12s, Declination +40 06' 49.68"

NGC 2782


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Posts: 131433
Date:
NGC 2782
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Title: NGC 2782: a merger remnant with young stars in its gaseous tidal tail
Authors: S. Torres-Flores, C. Mendes de Oliveira, D. F. de Mello, S. Scarano Jr, F. Urrutia-Viscarra

We have searched for young star-forming regions around the merger remnant NGC 2782. By using GALEX FUV and NUV imaging and HI data we found seven UV sources, located at distances greater than 26 kpc from the center of NGC 2782, and coinciding with its western HI tidal tail. These regions were resolved in several smaller systems when Gemini/GMOS r-band images were used. We compared the observed colours to stellar population synthesis models and we found that these objects have ages of ~1 to 11 Myr and masses ranging from 10^3.9 to 10^4.6 Solar masses. By using Gemini/GMOS spectroscopic data we confirm memberships and derive high metallicities for three of the young regions in the tail (12+log(O/H)=8.740.20, 8.810.20 and 8.780.20). These metallicities are similar to the value presented by the nuclear region of NGC 2782 and also similar to the value presented for an object located close to the main body of NGC 2782. The high metallicities measured for the star-forming regions in the gaseous tidal tail of NGC 2782 could be explained if they were formed out of highly enriched gas which was once expelled from the center of the merging galaxies when the system collided. An additional possibility is that the tail has been a nursery of a few generations of young stellar systems which ultimately polluted this medium with metals, further enriching the already pre-enriched gas ejected to the tail when the galaxies collided.

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NGC2782
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Astronomers have discovered a population of what appear to be young star clusters where they aren't supposed to be. The newborn stars appear to have formed in the debris of the NGC 2782 galaxy collision -- debris that lacks what astronomers believe are some important ingredients needed to form stars.

A large, Milky Way-type galaxy collided with a much smaller galaxy in the NGC 2782 collision. It's an example of the most common type of galaxy collision in the universe. Scientists believe that such collisions played an important role in the build-up of large galaxies in the early universe.
If confirmed, these newly discovered young star clusters and their environment could help shed light on the process of star formation, especially in the early universe in regions far from the crowded, active centres of galaxies.
Karen Knierman, a graduate student and Arizona/NASA Space Grant Fellow at the University of Arizona, and Patricia Knezek of the WIYN Consortium in Tucson, Ariz., are reporting the research at the American Astronomical Society meeting in Washington, D.C., US.
The astronomers found the star clusters by taking deep images of the galaxy collision with the 4 Megapixel CCD camera of the 1.8 meter Vatican Advanced Technology Telescope (VATT) at Mount Graham International Observatory in Arizona.


Position(2000): RA 09 14 05.27 Dec +40 06 47.0
Magnitude 11.5
Size 14'1 x 14'1

The starburst galaxy NGC 2782 lies about 111 million light years away toward the Lynx constellation. When the two galaxies of unequal mass collided about 200 million years ago, their gravitational pull ripped out two tails of debris with very different properties.

Beverly Smith of Eastern Tennessee University and collaborators studied the optical and gas properties of these two tails and published their results in 1994 and 1999. Studying the gas properties tells astronomers about neutral hydrogen gas and molecular gas -- both important ingredients in star formation. Smith and collaborators found that the optically bright eastern tail has some neutral hydrogen gas and molecular gas at the base of the tail, and an optically bright, but gas-poor concentration at the end of the tail. The optically faint western tail is rich in neutral hydrogen gas, but has no molecular gas.
Knierman and Knezek found blue star clusters younger than 100 million years along both tails, indicating that those stars formed within the tails after the galaxy collision began.


Optical image of the galaxy merger NGC 2782 showing the location of young star clusters which formed in the sweeping tails of debris after the collision. Even though the gas properties of the two tails are different, both tails show unexpectedly similar populations of young star clusters. This material was presented to the American Astronomical Society meeting in Washington, D.C. on January 11, 2006. (Photo: Karen Knierman, UA Steward Observatory, and Patricia Knezek, WIYN/NOAO)

"That's surprising because the western tail lacks molecular gas, one of the key ingredients for star formation" - Karen Knierman.

Star clusters are thought to form from the collapse of giant molecular gas clouds. If this were the case, astronomers would expect to see remnants of the molecular gas which helped give birth to the stars.
Given Smith's earlier observations of gas in the debris tails, Knierman and Knezek expected they might see star formation in the eastern tail, where molecular gas is clearly present. But they didn't expect to see star formation in the western tail, where no molecular gas was detected. Finding young star clusters in the western tail should prompt astronomers to question their current models of star formation.

"Do we still need a model of giant molecular gas clouds? Or do we need a different model - perhaps one with smaller clumps of molecular gas that might have been destroyed or blown away when these energetic young stars formed?" - Karen Knierman.

Finding unexpected young star clusters in the western tail could help explain why stars form in other places where there may be little molecular gas, like the outer edges of the Milky Way galaxy or in the debris of other galaxy collisions.

"This has important implications in how star formation proceeded when our universe was young and galaxy collisions were much more common than they are today" - Karen Knierman.

"Only recently have we become aware of the importance of the merging of small galaxies with larger systems in creating galaxies like our own Milky Way" - Patricia Knezek.

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