Cores to Clusters (eBook)

Contents 7
Foreword 12
I REVIEW ARTICLES 15
PHYSICAL PROPERTIES OF PRESTELLAR CORES 16
Introduction 16
Basic Ideas 17
Determining Physical Parameters of Star Forming Regions 20
Mass determinations 21
Temperatures 21
Densities 23
Magnetic Field and Ionization Degree 24
Future Prospects 25
Acknowledgments 25
References 25
IMPULSIVELY TRIGGERED STAR FORMATION 28
Introduction 28
Fragmentation of a shock-compressed layer 29
Larson’s scaling relations and the clump mass spectrum 30
The critical pressure for rapid star formation 32
The minimum mass for star formation 33
The fragmentation of shells swept up by expanding nebulae 36
Pre-existing cores subjected to a sudden increase in external pressure 37
Forming free-floating brown dwarves and planetary-mass objects by photo-erosion 38
Forming low-mass companions and free-.oating objects in interactions between protostellar discs 39
Conclusions 40
Acknowledgments 40
References 41
STARLESS CORES 44
Introduction 44
“Classical” studies of starless cores 45
Starless cores studies in the 1990s 46
The internal structure of the l1498 and L1517B cores 48
Density 50
Turbulence 52
Molecular composition 53
Tracing core evolution with molecular freeze out 55
L1521E: the youngest starless core? 57
Acknowledgments 58
References 58
CHEMICAL PROCESSES IN STAR FORMING REGIONS 60
Introduction 60
Basic concepts in astrochemistry 61
Gas–phase chemistry 62
Surface chemistry 64
References 74
PROTOSTELLAR JETS: A HIGH ANGULAR RESOLUTION PERSPECTIVE 80
Introduction 80
Properties of stellar jets 82
High angular resolution observations 84
Optical, NIR and Sub-mm Interferometry 87
Conclusions: universality of the accretion/ejection engine 88
Acknowledgments 89
References 89
NON-ISOTHERMAL GRAVOTURBULENT FRAGMENTATION 90
Introduction 91
Thermal properties of star-forming clouds 92
Numerical Approach 93
Dependency of the Characteristic Mass 94
Summary 96
Acknowledgments 98
References 98
THE BIRTH OF MASSIVE STARS AND STAR CLUSTERS 100
Introduction 100
Overview of physical properties 101
Setting up initial conditions for star cluster formation 102
How do stars form within clusters? 104
Formation of Cores 104
Accretion to Stars 105
Assumptions and Predictions of the McKee-Tan Model 106
Observational Evidence for Massive Star Formation from Cores and Accretion Disks 108
The timescale of star cluster formation 110
How does feedback affect the formation process? 111
Feedback in Individual Cores 111
Feedback during Star Cluster Formation 112
Feedback on GMCs 113
Acknowledgments 113
References 114
PRECURSORS OF UCHII REGIONS AND THE EVOLUTION OF MASSIVE OUTFLOWS 118
Precursors of UCHii regions 118
High-Mass Protostellar Objects (HMPOs) 119
High-Mass Starless Cores (HMSCs) 123
Massive molecular out.ows: an evolutionary scenario 124
Summary of observational constraints 124
A potential evolutionary scenario 127
Discussion and potential caveats 129
References 130
OBSERVATIONS OF ACCRETION ONTO HIGH MASS STARS 134
Introduction 134
Observations 137
The Accretion Flow 137
A simple model of the accretion .ow 140
Implications for star formation by accretion 142
References 142
DISKS AROUND MASSIVE (PROTO)STARS 144
The dividing line between high- and low-mass stars 144
Possible scenarios for high-mass star formation 145
Evidence for disks in massive (proto)stars 146
Disks traced by maser lines 146
Disks traced by continuum emission 147
Disks traced by thermal line emission 148
Conclusions 151
References 152
EMBEDDED CLUSTERS 154
Introduction 154
Importance of Embedded Clusters 155
Global Properties of Embedded Clusters 158
Embedded Cluster Mass Function 158
Embedded Cluster Birthrate and Survival 159
Role of Embedded Clusters in Understanding Star and Planet Formation 161
Protoplanetary, Circumstellar Disks 162
Acknowledgments 164
References 165
MASSIVE PROTOSTARS AND SMALL PROTOCLUSTERS 167
Massive Protostars 167
Clustering around candidate precursors to massive stars 168
NIR counterparts to candidate massive protostars 170
H2 emission around massive protostars 172
Scenario for massive star formation 173
Small proto-clusters 174
FutureWork 176
Acknowledgments 177
References 177
PRE-MAIN-SEQUENCE EVOLUTIONAND BROWNDWARFS BEYOND THE SOLAR VICINITY. 179
Introduction 179
Observations 181
Results 181
The luminosity and mass functions 184
Summary and .nal remarks 187
Acknowledgments 188
References 188
BROWN DWARFS 189
Introduction 189
Brown dwarfs and new Spectral types 191
Companions to stars 192
Searches in star clusters and young stellar associations: the brown dwarf mass function 192
Multiplicity 194
Formation mechanisms 195
Acknowledgments 196
References 196
II CONTRIBUTED POSTER ARTICLES 200
REVEALING THE STRUCTURE OF LUPINE DARKNESS: FROM CORES TO CLUSTERS 201
Abstract 201
Introduction 201
Observations and Data Reduction 202
Results 202
Analysis and Discussion 204
Acknowledgments 206
References 206
INFRARED STUDY OF THE SOUTHERN GALACTIC STAR FORMING REGION ASSOCIATED WITH IRAS 10049-5657 207
Introduction 207
Observations 207
Results and discussion 208
Radiative transfer modelling 210
Summary 211
References 212
STUDYING PROTOSTELLAR JETS THROUGH A COMBINED INFRARED/OPTICAL SPECTRAL ANALYSIS 213
Introduction 214
Variation of the physical parameters along the jet 214
Depletion of refractory species and presence of dust in the jet beam 215
Mass flux estimates and their implications 216
References 218
Introduction 219
Observations and data reduction 220
Results 220
Acknowledgments 221
References 222
Index 225