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RE: IC 342
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Hubble's Hidden Galaxy

IC 342 is a challenging cosmic target. Although it is bright, the galaxy sits near the equator of the Milky Way's galactic disk, where the sky is thick with glowing cosmic gas, bright stars, and dark, obscuring dust. In order for astronomers to see the intricate spiral structure of IC 342, they must gaze through a large amount of material contained within our own galaxy - no easy feat! As a result IC 342 is relatively difficult to spot and image, giving rise to its intriguing nickname: the 'Hidden Galaxy.'
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Giraffe galaxy
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Twisted magnetic loop in the Giraffe galaxy IC 342

Magnetic fields exist everywhere in the Universe, but there is still little idea how important they are for the evolution of cosmic objects. Radio waves are an ideal means to measure magnetic fields in galaxies. In a long-standing effort, Rainer Beck from the Max Planck Institute for Radio Astronomy (MPIfR) in Bonn, Germany, gathered a huge data set of the nearby galaxy IC 342 from observations with two of the world's largest radio telescopes, NRAO's Very Large Array and the 100-m radio telescope of the MPIfR, in four different wavelength bands, from 2.8 cm to 21 cm. An ordered magnetic field mostly aligned along the optical spiral arms was discovered. The discovery helps to explain how galactic spiral arms are formed. The same study also shows how gas can be funneled inward toward the center of IC 342.
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Title: Magnetic fields in the nearby spiral galaxy IC 342: A multifrequency radio polarisation study
Author: Rainer Beck

The total and polarised radio continuum emission of IC 342 was observed in four wavelength bands with the Effelsberg and VLA telescopes. The frequency-dependent radial scale length of the diffuse radio synchrotron disk is indicative of propagation of cosmic-ray electrons via the streaming instability. The equipartition strength of the total magnetic field is typically 15 muG, that of the ordered field 5 muG. Faraday rotation reveals an underlying regular field of only about 0.5 muG strength with an axisymmetric spiral pattern, signature of a mean-field dynamo, and an about 10x stronger field that fluctuates on scales of a few 100 pc. The magnetic field around the bar in the central region of IC 342 resembles that of large barred galaxies; its regular spiral field is directed outwards, opposite to that in the disk. The polarised emission in the disk is concentrated in: (1) a narrow arm of about 300 pc width, displaced inwards with respect to the eastern arm by about 200 pc, indicating magnetic fields compressed by a density wave, (2) a broad arm of 300-500 pc width around the northern arm with systematic variations of polarised emission, polarisation angles and Faraday rotation measures on a scale of about 2 kpc, indicative of a helically twisted flux tube generated by the Parker instability, (3) a rudimentary "magnetic arm" in an interarm region in the north-west, (4) several broad spiral arms in the outer galaxy, related to spiral arms in the total neutral gas, indicative of fast MHD density waves, (5) short features in the outer south-western galaxy, probably distorted by tidal interaction. - The generation and development of "magnetic arms" by a mean-field dynamo probably needs a spiral pattern that is stable over a few galactic rotation periods. The dynamo in IC 342 is slow and weak, probably disturbed by the bar, tidal interaction or a transient spiral pattern.

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IC 342 X-1
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Title: Discovery of a Quasi-Periodic Oscillation in the Ultraluminous X-ray Source IC 342 X-1: XMM-Newton Results
Author: V.K. Agrawal, Anuj Nandi

We report the discovery of a quasi-periodic oscillation (QPO) at 642 mHz in an XMM-Newton observation of the ultraluminous X-ray source (ULX) IC 342 X-1. The QPO has a centroid at QPO=64220 mHz, a coherence factor of Q=11.6, and an amplitude (rms) of 4.1% with significance of 3.6sigma. The energy dependence study shows that the QPO is stronger in the energy range 0.3 - 5.0 keV. A subsequent observation (6 days later) does not show any signature of the QPO in the power density spectrum. The broadband energy spectra (0.3 - 40.0 keV) obtained by quasi-simultaneous observations of XMM-Newton and NuSTAR can be well described by an absorbed diskbb plus cutoffpl model. The best fitted spectral parameters are power-law index (Gamma) ~ 1.1, cutoff energy (Ec) ~ 7.9 keV and disc temperature (kTin) ~ 0.33 keV, where the QPO is detected. The unabsorbed bolometric luminosity is ~ 5.34 x 1039 erg~s-1. Comparing with the well known X-ray binary GRS 1915+105, our results are consistent with the mass of the compact object in IC 342 X-1 being in the range ~20-65 solar masses. We discuss the possible implications of our results.

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Black holes seen by new X-ray eye

The highest-energy orbiting X-ray observatory ever devised has begun to share its unique view on the cosmos.
The Nuclear Spectroscopic Telescope Array, or Nustar, was launched in June 2012, but is already bearing fruit.
Researchers reporting at the 221st American Astronomical Society meeting released two striking Nustar images.

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Caldwell 5
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NASA's NuSTAR Catches Black Holes in Galaxy Web

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NASA's Nuclear Spectroscopic Telescope Array, or NuSTAR, set its X-ray eyes on a spiral galaxy and caught the brilliant glow of two black holes lurking inside.
The new image is being released Monday along with NuSTAR's view of the supernova remnant Cassiopeia A, at the American Astronomical Society meeting in Long Beach, Calif.

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IC 342
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Spitzer's Spider Web of Stars

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Those aren't insects trapped in a spider's web -- they're stars in our own Milky Way galaxy, lying between us and another spiral galaxy called IC 342. NASA's Spitzer Space Telescope captured this picture in infrared light, revealing the galaxy's bright patterns of dust.
At a distance of about 10 million light-years from Earth, IC 342 is relatively close by galaxy standards. However, our vantage point places it directly behind the disk of our own Milky Way. The intervening dust makes it difficult to see in visible light, but infrared light penetrates this veil easily. While stars in our own galaxy appear as blue/white dots, the blue haze is from IC 342's collective starlight. Red shows the dust structures, which contain clumps of new stars.

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Title: Giant Molecular Clouds in the Spiral Arm of IC 342
Authors: Akihiko Hirota, Nario Kuno, Naoko Sato, Hiroyuki Nakanishi, Tomoka Tosaki, Kazuo Sorai

We present results of 12CO (1-0) and 13CO (1-0) observations of the northeastern spiral arm segment of IC 342 with a ~ 50pc resolution carried out with the Nobeyama Millimeter Array. Zero-spacing components were recovered by combining with the existing data taken with the Nobeyama 45m telescope. Prime target is to investigate the variation of cloud properties across the spiral arm with a resolution comparable to size of giant molecular clouds (GMCs). The observations cover a 1 kpc x 1.5 kpc region located ~2 kpc away from the galactic center, where a giant molecular association (GMA) is located at trailing side and associated star forming regions at leading side. The spiral arm segment was resolved into a number of clouds whose size, temperature and surface mass density are comparable to typical GMCs in the Galaxy. 26 clouds were identified from the combined data cube and the identified clouds followed the linewidth-size relation of the Galactic GMCs. The identified GMCs were divided into two categories according to whether they are associated with star formation activity or not. Comparison between both categories indicated that the active GMCs are more massive, have smaller linewidth, and are closer to virial equilibrium compared to the quiescent GMCs. These variations of the GMC properties suggest that dissipation of excess kinetic energy of GMC is a required condition for onset of massive star formation.

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A leggy cosmic creature comes out of hiding in this new infrared view from NASA's Wide-field Infrared Survey Explorer, or WISE. The spiral beauty, called IC 342 and sometimes the "hidden galaxy," is shrouded behind our own galaxy, the Milky Way. Stargazers and professional astronomers have a hard time seeing the galaxy through the Milky Way's bright band of stars, dust and gas. WISE's infrared vision cuts through this veil, offering a crisp view.
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IC 342 is an intermediate spiral galaxy in the constellation Camelopardalis. The galaxy is located near the galactic equator where dust obscuration makes it a difficult object for both amateur and professional astronomers to observe.
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