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A Submillimeter Imaging Survey of Ultracompact HII Regions

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A Submillimeter Imaging Survey of Ultracompact HII Regions A Submillimeter Imaging Survey of Ultracompact HI I Regions Thesis by To dd R Hunter In Partial Fulllment of the Requirements for the Degree of Do ctor of Philosophy I T U T E O T F S N T I E C A I H N N R O O 1891 L F O I L G A Y C California Institute of Technology Pasadena California Submitted Septemb er ii c To dd R Hunter All Rights Reserved iii Comet Hyakutake photographed on March at Joshua Tree National Park California iv Acknowledgements Much of the success of this thesis can b e traced to Larry Ramsey and Je Hall for intro ducing me to instrumentation work at Penn State My exp erience as a VLA summer student in also inuenced me immeasurably by bringing radio astronomy to life in the Land of Enchantment where I made some lifelong friends Lo oking back I am pleased that Craig Walker convinced me to apply to Caltech I thank my graduate advisor Tom Phillips for teaching me how to tune SIS receivers at CSO and welcoming me into the submillimeter group a unique collection of p eople that always manages to nish rst when it counts Thanks to Pat Schaer and Jacob Ko oi for the worlds b est receivers and all those lab to ols of theirs that I didnt steal Sp ecial thanks go to Harvey Moseleys family and colleagues at NASAGo ddard for all their help and hospitality For answering my frequent computer and scientic questions Darek Lis deserves sp ecial mention Similar recognition go es to Gene Serabyn for help with optics and for constructive comments on this manuscript and to Ning Wang whose determination led to the timely commissioning of SHARC Thanks also to Maryvonne Gerin and Peter Schilke for showing me all the neat features of GRAPHIC For keeping the telescop e running thanks to the CSO sta esp ecially Taco a dep endable source of advice and humorous stories To Greg Taylor thanks for your lessons on VLA data and intro ducing me to the memb ers of the Arcetri group Thanks to Natalie Merchant and the kM for audio encouragement during long summer days of programming SHARC at the summit of Mauna Kea where by the force of will my lungs were lled Thanks to Eric Howard for his nearinfrared data on S Chris DePree for his radio data on K and Debra Shepherd and Peter Hofner for sharing their millimeter and radio data on G and G Much of the research rep orted here was augmented by the patient advice and frequent noggin usage of Dominic Benford and Rob ert Knop Finally with all the encouragement and help from my family back East these past ve years have b een well worth the eort v Abstract This research explores the pro cess of massive star formation in the Galaxy through submillimeter continuum and sp ectral line observations of ultracompact HI I UCHI I regions First I describ e the design and op eration of the Submillimeter High Angular Resolution Camera SHARCa pixel b olometer array camera for broadband con tinuum imaging at and m at the Caltech Submillimeter Observatory CSO Detailed information is included on the reective oaxis optical design and the in strument control software interface Second I present to resolution SHARC images of and m continuum emission from a sample of UCHI I regions with dierent radio morphologies Although the dust emission typically p eaks at or near the UCHI I region additional sources are often present sometimes coincident with the p osition of H O masers The combination of submillimeter millimeter and IRAS farinfrared ux densities forms the basis of greyb o dy mo dels of the sp ectral energy distributions The average dust temp erature is K and the average grain emissivity index is Using a radiative transfer program that solves for the dust temp erature versus radius the distribution of dust around UCHI I regions is mo deled with a p owerlaw spherical density prole to match the observed radial ux density proles By xing the source b oundary at the outer limit of the p submillimeter emission the resulting density proles nr r can b e classied into four categories regions exhibit p isothermal sphere exhibit p dynamical collapse exhibit p in the outer regions and p in the inner regions and exhibit p logatropic Although these simplied mo dels may not b e unique a go o d correlation b etween the dust luminositytomass ratio and the temp erature indicates that the more centrallycondensed sources exhibit higher star formation rates Third I present to resolution CO maps which reveal bip olar outows from out of UCHI I regions The outow mechanical luminosities and mass ejection rates follow the scaling relations with b olometric luminosity established vi for less luminous premain sequence stars However in contrast to lower luminosity sources the momentum from stellar radiation pressure is comparable to that required to drive the outows Many regions show evidence of separate overlapping outows In a nal detailed study resolution images obtained with the Owens Valley Mil limeter Array reveal multiple outows emanating from the molecular core containing the UCHI I region G while simultaneous outow and infall motion is seen toward the neighb oring lessevolved core containing G vii Contents Acknowledgements iv Abstract v Intro duction and Background Massive star formation Thesis outline The Submillimeter High Angular Resolution Camera SHARC Instrument overview Optical design Optical p erformance Instrument control system Data reduction Sensitivity Submillimeter Continuum Images of UCHI I Regions The characteristics of interstellar dust Computation of dust column density and mass from submillimeter ux density HIRES IRAS images Calibration and p ointing accuracy of the SHARC images SHARC images of cometary UCHI I regions SHARC images of shelllike UCHI I regions SHARC images of unresolved UCHI I regions SHARC image of the G Complex ON Greyb o dy mo dels viii Density proles Luminosity to mass ratios Summary Molecular Outows from UCHI I Regions Characteristics of molecular outows Possible mechanisms of jetdriven outows Outows from highmass starforming regions CO sp ectra CO outow maps Calculation of outow energetics Scaling relations Summary Active Star Formation toward the G and G UCHI I Regions Intro duction Observations Molecular outows Continuum emission Discussion Conclusions Summary References App endix A SHARC Cryostat Manual App endix B SHARC Software Manual App endix C Input parameters for the OUTFLOW program ix List of Figures Photograph of the b olometer array detector Layout of the ellipsoid reimager Strehl ratios versus chopp er angle Sp ot diagrams across the SHARC fo cal plane Sketch of the internal cryostat optics SHARC lter arrangement Strehl ratio versus dewar rotation angle CSOSHARC b eam map at m SHARC lter transmission curves SHARC Server computer display OTF map computer display SHARC NEFD s achieved at and m SHARC sensitivity vs integration time at m Mean ux densityweighted grain radius for the na a distribution HIRES IRAS maps of G HIRES IRAS maps of G HIRES IRAS maps of G HIRES IRAS maps of G HIRES IRAS maps of the K complex HIRES IRAS maps of G HIRES IRAS maps of WOH HIRES IRAS maps of G HIRES IRAS maps of G HIRES IRAS maps of Mono ceros R HIRES IRAS maps of GGD x HIRES IRAS maps of the S complex HIRES IRAS maps of G cm radio continuum image of G cm radio continuum image of G and m images of G H CO map around GSE H CO sp ectrum of GSE cm radio continuum image of G m image of G m image of G cm radio continuum image of G m image of G m image of G cm VLA image of GGD m image of the GGD cm radio continuum image of Mon R m image of the Mon R complex VLA cm image of the K complex m image of the K complex SHARC m image of the K complex cm radio continuum image of WOH m image of WOH m image of WOH m image of G m image of G m image of the G complex m image of the S complex m image of the S complex CS J image of the S complex K band m image of SFIR xi m image of G cm radio continuum image of G m image of the G complex m image of the.
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