High-resolution X-ray Imaging Of The Center Of Ic 342

摘要

We present the results of a high-resolution (θ_(FWHM) ～ 0.5") 12 ks Chandra HRC-I observation of the starburst galaxy IC 342 taken on 2006 April 2. We identify 23 X-ray sources within the central 30' × 30' region of IC 342 and resolve the historical ultraluminous X-ray source (ULX), X3, near the nucleus into two sources, namely, C12 and C13. The brighter source C12, with L_(0.08-10 keV) = (6.66 ± 0.45) × 10~(38) erg s~(-1), is spatially extended (≈82 pc × 127 pc). From the astrometric registration of the X-ray image, C12 is at R.A. = 03~h46~m48.43~s, decl. = +68°05'47.45", and is closer to the nucleus than C13. Thus, we conclude that source is not an ULX and must instead be associated with the nucleus. The fainter source C13, with L_(0.08-10 keV) = (5.1 ± 1.4) × 10~(37) erg s~(-1), is consistent with a point source located at 6.51" (position angle P.A. ≈ 240°) of C12. We also analyzed astrometrically corrected optical Hubble Space Telescope (HST) and radio Very Large Array images; a comparison with the X-ray image showed similarities in their morphologies. Regions of star formation within the central region of IC 342 are clearly visible in the HST Hα image, which contains three optical star clusters and our detected X-ray source C12. We find that the observed X-ray luminosity of C12 is very close to the predicted X-ray emission from a starburst, suggesting that the nuclear X-ray emission of IC 342 is dominated by a starburst. Furthermore, we discuss the possibility of active galactic nucleus (AGN) emission in the nucleus of IC 342, which we can neither prove nor discard with our data.