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Optical Outflows Associated with Herbig Ae/Be Stars

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Optical Outflows Associated with Herbig Ae/Be Stars Optical Outflows associated with Herbig Ae/Be Stars by David Corcoran B.Sc. (Hons.) A thesis submitted for the degree of Doctor of Philosophy Supervisors: Prof. T.P. Ray, Prof. D.M. Heffernan. School of Physical Sciences, Dublin City University, Dublin 9, September 1993. DECLARATION I hereby certify that this material, which I now submit for assessment on the programme of study leading to the award of Doctor of Philosophy is entirely my own work and has not been taken from the work of others save and to the extent that such work has been cited and acknowledged within the text of my work. David Corcoran ii C ontents 1 Introduction 1 1.1 Historical Background ............................................................................................. 1 1.2 The Evolution of Intermediate Mass Stars: A Theoretical Perspective . 4 1.2.1 Stellar Evolution of H A E B E S s....................................... 4 1.2.2 Activity in H A E B E S s............................................................................... 7 1.3 Have Her big Ae/Be Stars Circumstellar D isks? ....................................................10 1.4 O utflow s........................................................................................................................ 14 1.4.1 Observational Properties of Optical Outflows: Herbig-Haro ob­ jects and Jets .................................................................... 14 1.4.2 Theoretical Aspects of Optical Outflows...................................................17 1.4.3 Outflows from High Luminosity Sources...................................................22 1.4.4 F o rw a rd ..............................................................................................................26 2 The V3&0 Orion Region 28 2.1 Introduction......................................................................................................................28 iii 2.1.1 NGC 1999 and its s o u r c e ............................................... 29 2.1.2 The Spectral Energy Distribution of V380 Ori ........................................30 2.1.3 The Outflow of V380 Ori ..............................................................................30 2.1.4 Other Outflows near V380 Ori .............................................................. 32 2.2 Observational Details and Data Reduction............................................................34 2.2.1 Direct Im a g in g ........................................................................................... 34 2.2.2 Spectroscopy ............................................................................................... 37 2.3 Results for V380 Ori and nearby outflows............................................................ 40 2.3.1 Large scale HH emission about V380 Ori .................................................. 40 2.3.2 HH emission close to V380 O r i .................................................................... 41 2.3.3 Spectroscopy of HH objects near V380 Ori ...........................................43 2.3.4 The Spectrum of V380 Ori and the Background HII Region .... 46 2.3.5 Other stars in NGC 1999 ........................................................................ 50 2.4 Other Optical Outflows in the Vicinity of V380 O ri............................................51 2.4.1 HH 147 ......................................................................................................... 51 2.4.2 HH 130 and HH 3 6 ..................................................................................... 53 2.5 Discussion................................................................................................................... 55 2.5.1 The Possible Outflow Sources in NGC 1999 ....................................... 55 2.5.2 The Geometry and Orientation of the Outflow from V380 Ori . 56 iv 2.5.3 A Model for the Outflow of V3S0 Ori ......................................................57 2.5.4 The Spectrum of V380 Ori ............................................................. 62 2.5.5 Other Optical Outflows: HH1 4 7 .......................................................... 63 2.5.6 Other Optical Outflows: HH 130 .................................................63 3 Cepheus A 67 3.1 Introduction...................................................................................................................67 3.1.1 Optical and Near-Infrared observations ................................................. 68 3.1.2 Molecular Observations ...............................................................................69 3.2 Observational Details and Data Reduction........................................................... 70 3.2.1 Direct Im a g in g ............................................................................................ 70 3.2.2 Spectroscopy............................................................................................... 71 3.3 Results......................................................................................................................... 72 3.3.1 Imaging ......................................................................................................... 72 3.3.2 Spectral Analysis......................................................................................... 73 3.4 Discussion................................................................................................................... 75 3.4.1 The Bipolar Optical Outflow of Cep A .......................................................75 3.4.2 The Question of Molecular Outflows in Cep A ? 78 3.4.3 HH-NE and HH-NE2...................................................................................... 79 v 4 LkHft 198 and V376 Cas 82 4.1 Introduction....................................................................................................................82 4.1.1 Outflows in the LkHa 198 and V376 Cas Re g io n ....................................83 4.1.2 The Local Environment of LkHa 198 and V376 Cas: Polarisation Studies ..............................................................................................................85 4.1.3 The Local Environment of LkHa 198 and V376 Cas: Photometry . 86 4.2 Observation Details and Data Reduction............................................................... 88 4.2.1 Direct Imaging ................................................................................................ 88 4.2.2 Spectroscopy ....................................................................................................89 4.3 Results.......................................................................................................................... 90 4.3.1 Optical Imaging ......................................................................................... 90 4.3.2 Infrared Imaging ......................................................................................... 92 4.3.3 Spectral Analysis......................................................................................... 92 4.4 Discussion........................................................................................................................96 4.4.1 LkHa 198 and its Companion LkHa 198B ................................................. 96 4.4.2 The Optical Outflow from LkHa 198B .......................................................96 4.4.3 The Origin of the Reflection “Loop” N ebulae ..........................................97 4.4.4 The Optical Outflow from LkHa 198 .......................................................... 98 4.4.5 The Origin of the Molecular Outflow .......................................................... 98 vi 4.4.6 The Polarimetric Data of the LkHa 198 Region:An Explanation . 99 4.4.7 Has LkHa 198 a Far-Infrared h alo ?...........................................................101 4.4.8 V376 Cas and its Surrounding Region .......................... 102 5 Summary and Conclusions 103 5.1 The V380 Ori Region ...............................................................................................103 5.2 Cep A ............................................................................................................................ 106 5.3 LkHa 198 and V376 C as ........................................................................................... 107 5.4 The Question of Poorly collimated Optical Outflows from Intermediate/High Luminosity Sources? ..................................................................................................109 6 Acknowledgements 114 7 References 116 vii A bstract Optical outflows (HH objects and jets) have only recently been found to be associated with high luminosity sources (> 50 L®) such as the Herbig Ae/Be stars. In this thesis, using deep narrow band CCD imaging, the regions about three Herbig Ae/Be stars, V380 Ori, LkHa 198 and V376 Cas, together with one high luminosity embedded infrared source Cepheus A, have been examined in detail. In most cases, these young stellar objects, have been known or have been suspected in the past to be associated with HH objects. However, each of these regions is found to be considerably more complex than previously thought with the detection of at least twenty new HH objects, many of which are examined by spectroscopy. For LkHa 198, a bright HH knot previously thought to be associated with it, is in fact, not related. This object appears to be part of an optical outflow, the source of which is a newly discovered star located 5" to the northeast. A jet is seen
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