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<jats:title>Abstract</jats:title> <jats:p>A major question in the field of star formation is how molecular clouds form out of the diffuse interstellar medium (ISM). Recent advances in 3D dust mapping are revolutionizing our view of the structure of the ISM. Using the highest-resolution 3D dust map to date, we explore the structure of a nearby star-forming region, which includes the well-known Perseus and Taurus molecular clouds. We reveal an extended near-spherical shell, 156 pc in diameter (hereafter called the “Per-Tau Shell”), in which the Perseus and Taurus clouds are embedded. We also find a large ring structure at the location of Taurus (hereafter called the “Tau Ring”). We discuss a formation scenario for the Per-Tau Shell, in which previous stellar and supernova feedback events formed a large expanding shell, where the swept-up ISM has condensed to form both the shell and the Perseus and Taurus molecular clouds within it. We present auxiliary observations of H <jats:sc>i</jats:sc>, H<jats:italic>α</jats:italic>, <jats:sup>26</jats:sup>Al, and X-rays that further support this scenario, and estimate the Per-Tau Shell’s age to be ≈6–22 Myrs. The Per-Tau shell offers the first 3D observational view of a phenomenon long-hypothesized theoretically, molecular cloud formation and star formation triggered by previous stellar and supernova feedback.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We re-examine the physical relationship between extreme ultraviolet (EUV) waves and type II radio bursts. It has been thought that they are two observational aspects of a single coronal shock wave. However, a lack of their speed correlation hampers the understanding of their respective (or common) natures in a single phenomenon. Knowing the uncertainties in identifying true wave components from observations and measuring their speeds, we re-examine the speeds of EUV waves reported in previous literature and compare these with type II radio bursts and coronal mass ejections (CMEs). This confirms the inconsistency between the speeds of EUV waves and their associated type II radio bursts. Second, CME speeds are found to have a better correlation with type II radio bursts than EUV waves. Finally, type II speeds and their range tend to be much greater than those of EUV waves. We demonstrate that the speed inconsistency is in fact an intrinsic tendency and elucidate the nature of a coronal shock wave consisting of both driven and non-driven parts. This suggests that the speed inconsistency would remain even if all other uncertainties were removed.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We use high-precision neodymium isotope data for sequentially acid-leached components of the primitive carbonaceous chondrite Tagish Lake to identify a non-classical <jats:sup>150</jats:sup>Nd-rich presolar carrier phase that has not been identified as of yet in meteorites. The distinct isotopic signature of this carrier can be attributed to the intermediate neutron capture process (<jats:italic>i</jats:italic>-process) occurring in asymptotic giant branch (AGB), super-AGB, or post-AGB stars or, alternatively, the slow capture process (<jats:italic>s</jats:italic>-process) occurring in rotating massive stars. The <jats:sup>150</jats:sup>Nd-rich carrier appears to be heterogeneously distributed in the solar protoplanetary disk resulting in systematic isotope variations between carbonaceous and non-carbonaceous solar system materials. Carbonaceous chondrites that accreted in the outer disk are depleted in this carrier relative to non-carbonaceous materials that accreted in the terrestrial planet-forming region. Calcium-aluminum-rich inclusions that represent the earliest formed disk solids record the largest depletion of this carrier. This distribution pattern is contrary to that seen for the carriers of other neutron-rich isotope anomalies (<jats:sup>48</jats:sup>Ca, <jats:sup>54</jats:sup>Cr, <jats:sup>95,97</jats:sup>Mo, etc.) that have defined carbonaceous/non-carbonaceous isotope dichotomy so far. Irrespective of the exact astrophysical origin of these carriers, divergent distribution of presolar dust as a function of physicochemical processing in the solar protoplanetary disk best explains the solar system isotope dichotomy as opposed to changes in the composition of the infall.</jats:p>