Abstract
Abstract We present Herschel SPIRE and PACS maps of the Cepheus Flare clouds L1157, L1172, L1228, L1241, and L1251, observed by the Herschel Gould Belt Survey of nearby star-forming molecular clouds. Through modified blackbody fits to the SPIRE and PACS data, we determine typical cloud column densities of (0.5–1.0) × 1021 cm−2 and typical cloud temperatures of 14–15 K. Using the getsources identification algorithm, we extract 832 dense cores from the SPIRE and PACS data at 160–500 μm. From placement in a mass versus size diagram, we consider 303 to be candidate prestellar cores, and 178 of these to be “robust” prestellar cores. From an independent extraction of sources at 70 μm, we consider 25 of the 832 dense cores to be protostellar. The distribution of background column densities coincident with candidate prestellar cores peaks at (2–4) × 1021 cm−2. About half of the candidate prestellar cores in Cepheus may have formed as a result of the widespread fragmentation expected to occur within filaments of “transcritical” line mass. The lognormal robust prestellar core mass function (CMF) drawn from all five Cepheus clouds peaks at 0.56 M ⊙ and has a width of ∼0.5 dex, similar to that of Aquila’s CMF. Indeed, the width of Cepheus’s aggregate CMF is similar to the stellar system initial mass function (IMF). The similarity of CMF widths in different clouds and the system IMF suggests a common, possibly turbulent origin for seeding the fluctuations that evolve into prestellar cores and stars.
Highlights
Understanding the process of star formation is a major cornerstone of modern astrophysics
The paper contains three appendices: in Appendix A, we provide the images of all five clouds at 70, 160, 250, 350, and 500 μm; in Appendix B, we provide the criteria applied to sources detected by the getsources algorithm for reliability; and in Appendix C, we list the information provided in online material, including catalogs of the observed and derived physical properties of all dense cores identified in the Cepheus clouds studied and thumbnail images of each core at 70–500 μm and in H2 column density
Benedettini et al (2018) identify ∼30% fewer numbers of cores in Lupus than what we find over all five Cepheus clouds, e.g., 532 dense cores, of which 102 are candidate prestellar cores
Summary
Understanding the process of star formation is a major cornerstone of modern astrophysics. Key results from the HGBS so far include the identification of the ubiquity of filamentary substructure in molecular clouds, the close association of prestellar cores in some clouds with filaments of average column density greater than a fiducial threshold or transition of ∼7 × 1021 cm−2, and the universality of the lognormal morphology of the prestellar core mass function (André et al 2014). With Herschel data, we have access to far-infrared/ submillimeter emission from the Cepheus clouds of high sensitivity and resolution over a wide range of spatial scales, sampling both faint and diffuse and bright and compact emission sources With such capability, we can examine filamentary structure in these clouds previously undetected from ground-based emission or extinction map studies. The paper contains three appendices: in Appendix A, we provide the images of all five clouds at 70, 160, 250, 350, and 500 μm; in Appendix B, we provide the criteria applied to sources detected by the getsources algorithm for reliability; and in Appendix C, we list the information provided in online material, including catalogs of the observed and derived physical properties of all dense cores identified in the Cepheus clouds studied and thumbnail images of each core at 70–500 μm and in H2 column density
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