IC 443

Supernova
name = [http://simbad.u-strasbg.fr/simbad/sim-id?protocol=html&Ident=ic+443 Supernova Remnant IC 443]


caption = Part of the northeastern shell of IC 443, aka the Jellyfish Nebula. Credit: Jean-Charles Cuillandre (CFHT), Hawaiian Starlight, CFHT.
epoch = J2000
type = SN II (?)
SNRtype= Mixed Morphology
host = Milky Way
constellation = Gemini
gal = G189.1+3.0
dist_ly = 5,000 ly
size_v = 45 arcmin
ra = 06h 17m 13s
dec = +22° 31′ 05′′
mag_v =
distance = 5000 light-years, or 1.5 kpc
discovery=
iauc=
notes = Interaction with molecular clouds

IC 443 (also known as the Jellyfish Nebula) is a Galactic supernova remnant (SNR) in the constellation Gemini. On the plan of the sky, it is located near the star Eta Geminorum. Its distance is roughly 5,000 light years (~5×1016 km) from Earth.
IC 443 is thought to be the remains of a supernova occurred 3,000 - 30,000 years ago.The same supernova event likely created the neutron star CXOU J061705.3+222127, the collapsed remnant of the stellar core.
IC 443 is one of the best-studied case of supernova remnant interacting with surrounding molecular clouds.

Global Properties

.In the image North is up, East is left. Credit: XMM-Newton/DSS]

IC 443 is an extended source, having an angular diameter of 50 arcmin (by comparison, the full moon is 30 arcmin across). At the estimated distance of 5,000 ly (1,500 parsec) from Earth, it corresponds to a physical size of roughly 70 light years (20 parsec).

The SNR optical and radio morphology is shell-like (e.g. a prototypical shell-like SNR is SN 1006), consisting of two connected sub-shells with different centers and radii. A third larger sub-shell, initially attributed to IC 443, is now recognized as a different and older (100,000 years) SNR, called G189.6+3.3 [cite journal
url = http://adsabs.harvard.edu/abs/1994A%26A...284..573A
author = Asaoka, I. & Aschenbach, B.
title = An X-ray study of IC 443 and the discovery of a new supernova remnant by ROSAT
journal = Astronomy & Astrophysics
volume = 284
pages = 573
year = 1994
] .
Notably, IC 443 X-ray morphology is centrally peaked and a very soft X-ray shell is barely visiblecite journal
url = http://adsabs.harvard.edu/abs/2006ApJ...649..258T
author = Troja, E., "et al."
title = XMM-Newton Observations of the SNR IC 443. I. Soft X-Ray Emission from Shocked Interstellar Medium
journal = Astrophysical Journal
volume = 649
pages = 258
year = 2006
] . Unlike plerion remnants, e.g. the Crab Nebula, the inner X-ray emission is not dominated by the central pulsar wind nebula. It has indeed a thermal origincite journal
url = http://adsabs.harvard.edu/abs/1988ApJ...335..215P
author = Petre, R., "et al."
title = A comprehensive study of the X-ray structure and spectrum of IC 443
journal = Astrophysical Journal
volume = 335
pages = 215
year = 1988
] . IC 443 shows very similar features to the class of mixed morphology [cite journal
url = http://adsabs.harvard.edu/abs/1998ApJ...503L.167R
author = Rho, J. & Petre, R.
title = Mixed-Morphology Supernova Remnants
journal = Astrophysical Journal Letters
volume = 503
pages = L167
year = 1998
] SNRs.
Both optical and X-ray emission are heavily absorbed by a giant molecular cloud in the foreground, crossing the whole remnant body from northwest to southeast.

The remnant's age is still uncertain. There is some agreement that the progenitor supernova happened between 3,000 and 30,000cite journal
url = http://adsabs.harvard.edu/abs/1999ApJ...511..798C
author = Chevalier, R.
title = Supernova Remnants in Molecular Clouds
journal = Astrophysical Journal
volume = 511
pages = 798
year = 1999
] years ago. Recent Chandra [cite journal
url = http://adsabs.harvard.edu/abs/2001ApJ...554L.205O
author = Olbert, C. M., "et al."
title = A Bow Shock Nebula around a Compact X-Ray Source in the Supernova Remnant IC 443
journal = Astrophysical Journal Letters
volume = 554
pages = L205
year = 2001
] and XMM-Newton [cite journal
url = http://adsabs.harvard.edu/abs/2001A%26A...376..248B
author = Bocchino, F. & Bykov, A. M.
title = The plerion nebula in IC 443: The XMM-Newton view
journal = Astronomy & Astrophysics
volume = 376
pages = 248
year = 2001
] observationsidentified a plerion nebula, close to the remnant southern rim. The point source near the apex of the nebula isa neutron star, relic of a SN explosion.The location in a star forming region and the presence ofa neutron star favor a Type II supernova, the ultimate fate of a massive star, as the progenitor explosion.

The SNR environment

thumb|left|320px">
IC 443 wide field image. The stars η (right) and μ (left) Geminorum, the diffuse emission from S249 (north), and the G189.6+3.3 partial shell (center) are visible. Credit: Giovanni Benintende

The SNR IC 443 is located in the Galactic anticenter direction (l=189.1°), close to the Galacatic plane (b=+3.0°). Many objects lie in the same region of sky: the HII region S249, several young stars members of the GEM OB1 association, and an older SNR (G189.6+3.3).

The remnant is evolving in a rich and complex environment, which strongly affects its morphology. Multi-wavelenght observations show the presence of sharp density gradients and different clouds geometriesin the surroundings of IC 443. Massive stars are known to be short lived (roughly 30 million years), ending their life when they are still embedded within the progenitor cloud. The more massive stars ("O-type") probably clear the circum-stellar environment by powerful stellar winds or photoionizing radiation. Early "B-type" stars, with a typical mass between 8 and 12 solar masses, are not capable of this, and they likely interact with the primordial molecular cloud when they explode.Thus, it is not surprising that the SNR IC 443, which is thought to be the aftermath of a stellar explosion,evolved in such complex environment. For instance, an appreciable fraction of supernova remnants lies close to dense molecular clouds (~50 out of 265 in the Green catalogue [Green, D. A (2006), " [http://www.mrao.cam.ac.uk/surveys/snrs/ A Catalogue of Galactic Supernova Remnants (2006 April version)] ", Astrophysics Group, Cavendish Laboratory, Cambridge, United Kingdom] ), and most of them (~60%) show clear signs of interaction with the adjacent cloud.

X-ray and the optical images are characterized by a dark lane, crossing IC 443 from northwest to southeast.Emission from quiescent molecular gas has been observed toward the same direction [cite journal
url = http://adsabs.harvard.edu/abs/1977A%26A....54..889C
author = Cornett, R. H. "et al."
title = Observations of CO emission from a dense cloud associated with the supernova remnant IC 443
journal = Astronomy & Astrophysics
volume = 54
pages = 889
year = 1977
] , and it is likely due to a giant molecular cloud, located between the remnant and the observer. This is the main source of extinction of the low energy SNR emission.


thumb|right|200px|2MASS Atlas Image of IC 443. In this false-color infrared image, blue marks expanding gas where emission is dominated by excited iron atoms; the southern ridge (in red) is dominated by molecular hydrogen emission. In the image North is up, East is left.">Credit: 2MASS Collaboration, U. Mass., IPAC

In the southeast the blast wave is interacting with a very dense (~10,000 cm-3) and clumpy molecular cloud, such that the emitting shocked gas has a ring-like shape. The blast wave has been strongly deceleratedby the cloud and is moving with an estimated velocity of roughly 30-40 km s-1cite journal
url = http://adsabs.harvard.edu/abs/2001ApJ...547..885R
author = Rho, J., "et al."
title = Near-Infrared Imaging and OI Spectroscopy of IC 443 using Two Micron All Sky Survey and Infrared Space Observatory
journal = Astrophysical Journal
volume = 547
pages = 885
year = 2001
] .OH (1720 MHz) maser emission, which is a robust tracer of interaction between SNRs and dense molecular clouds,has been detected in this region [cite journal
url = http://adsabs.harvard.edu/abs/2006ApJ...652.1288H
author = Hewitt, J. W., "et al."
title = Green Bank Telescope Observations of IC 443: The Nature of OH (1720 MHz) Masers and OH Absorption
journal = Astrophysical Journal
volume = 652
pages = 1288
year = 2006
] .Interestingly, a source of gamma-ray radiationcite journal
url = http://adsabs.harvard.edu/abs/2007ApJ...664L..87A
author = Albert, J., "et al."
title = Discovery of Very High Energy Gamma Radiation from IC 443 with the MAGIC Telescope
journal = Astrophysical Journal Letters
volume = 664
pages = L87
year = 2007
] is spatially coincident with IC 443 and the maser emission region, though is not well understood whether it is physically associated with the remnant or not.

In the northeast, where the brightest optical filaments are located, the SNR is interacting with a very different environment. The forward shock has encountered with a wall of neutral hydrogen (HI),and is propagating into a less dense medium (~10-1,000 cm-3) with a much higher velocity (80-100 km s-1) than in the southern ridge.

In the western region, the shock wave breakouts into a more homogeneous and rarefied medium.

ee also

* CXOU J061705.3+222127, the neutron star embedded within supernova remnant IC 443.

References

External links

* [http://www.sciencedaily.com/releases/2006/06/060601212933.htm The Case Of The Neutron Star With A Wayward Wake] Chandra X-ray Center (ScienceDaily) June 1, 2006
* [http://antwrp.gsfc.nasa.gov/apod/ap060602.html APOD, 2006 June 2]


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