Several faint and sparse knots are detected over all the field of observations, especially around the systemic velocity of IC443 vLSR = −4.5 km s−1 (Hewitt et al. 2006). These structures, noticeable between v = −7.5 km s−1 and v = −1.5 km s−1, might either correspond to a slice of turbulent medium driven by the SN shockwave and/or belong to the ambient gas associated with the NW-SE molecular cloud in which IC443G is embedded (Lee et al. 2012). Other than that, the description of the region probed by our observations can be divided into the following six distinct structures:

1.Cloudlet: in the upper part of the field we observe a large (~ 5′ × 2′, i.e., ~ 2.8 × 1.1 pc) elongated cloudlet detected between v = −7.0 km s−1 and v = −5.5 km s−1 (indicated by the letter “A” in Fig. 2), which is also detected in 12CO(3–2). This structure was labeled G1 by Zhang et al. (2010), as part of the double-peaked morphology of the extended G region. The 13CO J = 1–0 counterpart of this structure is much brighter than the other main structures in the field, and it is also detected in the transitions J = 2–1 and J = 3–2, and in C18O J = 1–0 and J = 2–1. This structure was also presented and characterized by Lee et al. (2012) who proposed the label SC 03, among a total of 12 SCs (of size ~1′) found in IC443.
2.Ring-like structure: a ring-like structure seemingly lying in the center of the field (indicated by the letter “B” in Fig. 2), appearing between v = −5.5 km s−1 and v = −4.5 km s−1 and also detected in 12CO(3–2). It has a semimajor axis of 1.5′, or 0.8 pc. This structure might be spurious and is likely to be physically connected to the elongated cloudlet as both are spatially contiguous and their emission lines are spectrally close. It is partially detected as well in our observations of 13CO J = 1–0, J = 2–1 and J = 3–2, and also has a faint, partial counterpart in C18O J = 1–0 and J = 2–1. To understand the nature of this region we searched for counterparts in Spitzer Multiband Imaging Photometer (MIPS), WISE, DSS and XMM-Newton data; and in near-infrared and optical point source catalogs (Sect. 5), without success. Owing to projection effects, this apparent circular shape could also be explained by an unresolved and clumpy distribution of gas.
3.Shocked clump: in the lower part of the field we identify a very bright clump emitting between v = −31.0 km s−1 and v = 16 km s−1. This structure of size ~2′ × 0.75′ (~ 1.1 × 0.4 pc), which is detected in the 12CO(3–2) transition as well, belongs to the southwestern ridge of the molecular shell of the SNR and has been described as a shocked molecular structure by several studies (van Dishoeck et al. 1993; Cesarsky et al. 1999; Snell et al. 2005; Shinn et al. 2011; Zhang et al. 2010). The core of the shocked clump (indicated by the letter “C” in Fig. 2) is also detected in 13CO in the transitions J = 1–0, J = 2–1, and J = 3–2, and in C18O J = 1–0 and J = 2–1.
4.Shocked knot: an additional shocked knot (indicated by the letter “D” in Fig. 2) is also detected to the west of the previously described structure. This fainter and smaller structure is spatially separated from the main shocked clump.
5.At the same position as the shocked clump and extending southward and westward, we find a faint, elongated clump emitting between v = 5.0 km s−1 and v = 7.5 km s−1. This structure (indicated by the symbol “*” in Fig. 2) spatially coincides with the shocked clump, yet the peak velocity is not exactly the same (see developments on kinematics of the region in Sect. 3.3). It has a faint counterpart in 13CO(1–0). Observations of the ambient molecular cloud by Lee et al. (2012) indicate this structure as part of a faint NE-SW complex of molecular gas in the velocity range +3 km s−1 vLSR  +10 km s−1.
6.Finally, the 13CO(1–0) map (Fig. 4, right panel and Fig. D.2) indicates a large clump of gas extending from the bottom center to the right end of the field, with a bright knot in the bottom right corner of the field. However, this structure has no bright, well-defined counterpart in any of the 12CO transitions maps. It is spatially and kinematically correlated with the faint and diffuse 12CO J = 1–0 and J = 2–1 emission seen in the velocity range −5.5 km s−1 vLSR  −2 km s−1. From the comparison with the 12CO observations of Lee et al. (2012) and 13CO observations of Su et al. (2014) toward the SNR, we conclude that this structure is part of the western molecular complex observed in the velocity range −10 km s−1 vLSR  0 km s−1.
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