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Star Formation in the Perseus Molecular Cloud: a Detailed Look at Star-Forming Clumps with Herschel by Sarah I. Sadavoy B.Sc., Y

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Star Formation in the Perseus Molecular Cloud: a Detailed Look at Star-Forming Clumps with Herschel by Sarah I. Sadavoy B.Sc., Y Star Formation in the Perseus Molecular Cloud: A Detailed Look at Star-Forming Clumps with Herschel by Sarah I. Sadavoy B.Sc., York University, 2007 M.Sc., University of Victoria, 2009 A Dissertation Submitted in Partial Fulfillment of the Requirements for the Degree of DOCTOR OF PHILOSOPHY in the Department of Physics and Astronomy c Sarah Sadavoy, 2013 University of Victoria All rights reserved. This dissertation may not be reproduced in whole or in part, by photocopying or other means, without the permission of the author. ii Star Formation in the Perseus Molecular Cloud: A Detailed Look at Star-Forming Clumps with Herschel by Sarah I. Sadavoy B.Sc., York University, 2007 M.Sc., University of Victoria, 2009 Supervisory Committee Dr. J. Di Francesco, Co-Supervisor (Physics and Astronomy) Dr. S. Ellison, Co-Supervisor (Physics and Astronomy) Dr. K. Venn, Departmental Member (Physics and Astronomy) Dr. N. Frank, Outside Member (Chemistry) iii Supervisory Committee Dr. J. Di Francesco, Co-Supervisor (Physics and Astronomy) Dr. S. Ellison, Co-Supervisor (Physics and Astronomy) Dr. K. Venn, Departmental Member (Physics and Astronomy) Dr. N. Frank, Outside Member (Chemistry) ABSTRACT This dissertation presents new Herschel observations at 70 µm, 160 µm, 250 µm, 350 µm, and 500 µm of the Perseus molecular cloud from the Herschel Gould Belt Survey. The Perseus molecular cloud is a nearby star-forming region consisting of seven main star-forming clumps. The Herschel observations are used to characterize and contrast the properties of these clumps, and to study their embedded core popu- lations. First, we probed the exceptionally young clump, B1-E. Using complementary molecular line data, we demonstrate that B1-E is likely fragmenting into a first gener- ation of dense cores in relative isolation. Such a core formation region has never been observed before. Second, we use complementary long wavelength observations at 850 µm to study the dust properties in the larger, more active B1 clump. We find that Herschel data alone cannot constrain well the dust properties of cold dust emission and that long wavelength observations are needed. Additionally, we find evidence of dust grain growth towards the dense cores in B1, where the dust emissivity index, β, varies from the often assumed value of β = 2. In the absence of long wavelength observations, however, assuming β = 2 is preferable over measuring β with the Her- schel-only bands. Finally, we use the source extraction code, getsources, to identify the core populations within each clump from the Herschel data. In addition, we use complementary archival infrared observations to study their populations of young iv stellar objects (YSOs). We find that the more massive clumps have an excess of older stage YSOs, suggesting that these regions contracted first. Starless cores are typi- cally associated with peaks in the column density, where those found towards regions of higher column density also have higher average densities and colder temperatures. Starless cores associated with a strong, local interstellar radiation field, however, have higher temperatures. We find that the clumps with the most prominent high column density tails also had the highest fractions of early-stage YSOs. This relation sug- gests that the quantity of high column density material corresponds to recent star formation activity. v Contents Supervisory Committee ii Abstract iii Table of Contents v List of Tables ix List of Figures xii Acknowledgements xv Dedication xvi 1 Introduction 1 2 Instrumentation and Data 15 2.1 Instrumentation.............................. 15 2.2 ObservationsandReduction . 17 3 Cloud Structure: B1-East 20 3.1 Introduction................................ 20 3.2 Data.................................... 22 3.2.1 Herschel Observations ...................... 22 3.2.2 GBTObservations ........................ 24 3.3 Results................................... 25 3.3.1 SED Fitting to Herschel Data.................. 25 3.3.2 ColumnDensityProfiles . 28 3.3.3 Substructures ........................... 31 3.3.4 LineEmission........................... 33 vi 3.4 Discussion................................. 37 3.4.1 Comparison with Jeans Instability . 38 3.4.2 TimeScaleforInteractions. 39 3.4.3 Comparison with Virial Equlibrium . 40 3.4.4 Comparison with Other Star Forming Regions . 42 3.4.5 Comparison with Core Formation Models . 43 3.5 Conclusions ................................ 45 4 Dust Properties: B1 47 4.1 Introduction................................ 47 4.2 Data.................................... 49 4.2.1 HerschelObservations . 49 4.2.2 SCUBA-2Observations. 50 4.2.3 HARPObservations . .. .. 52 4.3 Results................................... 54 4.3.1 SCUBA-2 and HARP Analyses . 54 4.3.2 Herschel-OnlyResults . 56 4.4 Determining β ............................... 60 4.4.1 β UsingFilteredMaps ...................... 62 4.4.2 β UsingUnfilteredMaps . 68 4.4.3 Comparison of the Techniques . 70 4.5 Discussion................................. 71 4.5.1 Submillimeter Dust Opacity and Dust Masses . 71 4.5.2 Temperature and β ........................ 75 4.5.3 TheAdditionofSCUBA-2Data. 76 4.5.4 High Resolution Extinction Maps . 77 4.6 Summary ................................. 77 5 Analysis of the Perseus Molecular Cloud 80 5.1 Introduction................................ 81 5.2 Data.................................... 82 5.2.1 HerschelObservations . 82 5.2.2 ArchivalData........................... 83 5.3 HerschelSources ............................. 87 5.3.1 SourceExtraction. .. .. 87 vii 5.3.2 SourceSelection.......................... 89 5.3.3 GalaxyContamination . 91 5.4 Results................................... 93 5.4.1 Clumps .............................. 93 5.4.2 SourceProperties . .. .. 97 5.4.3 SourceClassification . 102 5.4.4 BoundandUnboundStarlessCores . 103 5.4.5 YSOClassification . 106 5.4.6 YSOCoincidences . .. .. 110 5.4.7 Source Classification Summary . 114 5.5 Discussion ................................. 115 5.5.1 Robustness of Source Selections . 115 5.5.2 Column Density and Extinction . 116 5.5.3 StarlessCoreProperties . 120 5.5.4 Starless Cores and Questionably Starless Cores . ... 122 5.5.5 ProtostellarCores. 126 5.5.6 Tbol withHerschel......................... 129 5.5.7 Lbol withHerschel......................... 130 5.5.8 GlobalYSOPopulations . 133 5.5.9 Core and YSO Populations with Clump . 136 5.6 Summary ................................. 141 6 Conclusions 144 A Acronyms and Symbols 152 B SCUBA-2 Filtering 154 C CO Line Contamination 156 D Herschel Colour Corrections 158 E Measuring β from Unfiltered Maps 160 E.1 OffsetCase ................................ 160 E.2 SpatialFactorCase............................ 164 F Source Temperatures 167 viii G YSO Extinction 169 H Source Tables 173 Bibliography 231 ix List of Tables Table 3.1 Target information for the Green Bank Telescope. ....... 26 Table 3.2 Properties of the nine substructures. ..... 32 Table 3.3 Measured properties from the NH3 spectra. ........... 36 Table 3.4 Results from a virial analysis. ... 41 Table 4.1 Adopted colour corrections and flux uncertainties for the Herschel bands. ................................ 58 Table4.2 Estimatesofcoremasses. 74 Table 5.1 Extragalactic Contamination Counts . .... 93 Table 5.2 Adopted colour corrections and flux uncertainties for the Perseus Clumps. ............................... 94 Table5.3 ClumpProperties . .. .. 97 Table5.4 SourceColourCorrections . 99 Table5.5 SourceSEDProperties. 101 Table5.6 SED-FittingStatistics . 102 Table5.7 SourceClassification . 103 Table 5.8 Source Classification Statistics . .... 103 Table 5.9 Virial Classification Statistics . ..... 106 Table 5.10 YSO Classification Comparison . 112 Table 5.11 Average Starless Core Properties . .... 120 Table 5.12 YSO Classification Comparison . 131 Table5.13YSOCountComparison . 135 Table 5.14 Core and YSO Populations in Perseus Clumps . .... 137 TableA.1CommonAcronyms . 152 Table A.2 Common Symbols and Constants . 153 TableG.1 ExtinctionRatios. 170 x TableH.1ResultsFromSEDFitting . 175 TableH.1ResultsFromSEDFitting . 176 TableH.1ResultsFromSEDFitting . 177 TableH.1ResultsFromSEDFitting . 178 TableH.1ResultsFromSEDFitting . 179 TableH.1ResultsFromSEDFitting . 180 TableH.1ResultsFromSEDFitting . 181 TableH.1ResultsFromSEDFitting . 182 TableH.1ResultsFromSEDFitting . 183 TableH.1ResultsFromSEDFitting . 184 TableH.1ResultsFromSEDFitting . 185 TableH.1ResultsFromSEDFitting . 186 TableH.1ResultsFromSEDFitting . 187 TableH.1ResultsFromSEDFitting . 188 TableH.1ResultsFromSEDFitting . 189 TableH.1ResultsFromSEDFitting . 190 TableH.1ResultsFromSEDFitting . 191 TableH.1ResultsFromSEDFitting . 192 TableH.1ResultsFromSEDFitting . 193 TableH.1ResultsFromSEDFitting . 194 TableH.1ResultsFromSEDFitting . 195 TableH.1ResultsFromSEDFitting . 196 Table H.2 Classification of Herschel Objects ................. 198 Table H.2 Classification of Herschel Objects ................. 199 Table H.2 Classification of Herschel Objects ................. 200 Table H.2 Classification of Herschel Objects ................. 201 Table H.2 Classification of Herschel Objects ................. 202 Table H.2 Classification of Herschel Objects ................. 203 Table H.2 Classification of Herschel Objects ................. 204 Table H.2 Classification of Herschel Objects ................. 205 Table H.2 Classification of Herschel Objects ................. 206 Table H.2 Classification of Herschel Objects ................. 207 Table H.2 Classification of Herschel Objects ................. 208 Table H.2
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