Early Stages of Massive Star Formation at High Spatial Resolution PDF Download

Author: Elena Puga
Publisher:
ISBN:
Category :
Languages : en
Pages : 0

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Author: Elena Puga Antolín
Publisher:
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Category :
Languages : en
Pages : 0

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Category :
Languages : en
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Massive star formation takes place under harsh observational conditions; as time passes, the already formed stars produce an ionised region and dissipate the surrounding molecular cloud, becoming accessible in the NIR. For this reason one of the earliest phases to observationally study massive stars is the UCHII-region phase. This thesis investigates the ionising stars and kinematics of UCHII regions at high spatial and spectral resolution. NIR-polarimetric maps of the reflection nebula that are generally found around these objects are used to rule out the presence of deeply embedded companions of a Young Stellar Object (S106) and to identify multiplicity in the main illuminating sources (also candidates to be the ionising sources) inside G77.96-0.01. This last result could also explain the relationship between some UCHIIs and their detected extended halos. An extensive analysis of a complex UCHII (G61.48+0.09) shows the problem of completeness of the detected stellar content in the NIR, and thanks to a K-band polarimetric map, the internal ionisation model for the smaller component is predicted and the corresponding stellar counterpart is detected at 3.5 (mu)m. The spectral energy distribution and the presence of Br(gamma) emission in the stellar spectra translates into the possible presence of a supergiant as part of the population inside this UCHII. The confirmation of the existence of evolved stars in these objects is an evidence of longer lifetimes than expected by the simple expansion of the Strömgren sphere. Finally the study of the kinematical structure of G5.89-0.39, the paradigm of shell-type UCHII and most massive outflow of the Galaxy, reveals that the confirmed shocked molecular hydrogen emission is compatible with a north-south orientation of the outflow, whereas the ionised material seems to trace a secondary outflow structure and therefore a possible secondary star inside G5.89-0.39. The short dynamical age derived for this object (

Author: Ilaria Pascucci
Publisher:
ISBN:
Category :
Languages : en
Pages : 100

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Author: Ke Wang
Publisher: Springer
ISBN: 3662449692
Category : Science
Languages : en
Pages : 160

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This thesis presents an in-depth, high-resolution observational study on the very beginning of the formation process: the fragmentation of dense molecular clouds known as infrared dark clouds (IRDCs). Using the Submillimeter Array (SMA) and Very Large Array (VLA) radio interferometers, the author has discovered a common picture of hierarchical fragmentation that challenges some of the leading theoretical models and suggests a new, observation-driven understanding of how massive star formation in clustered environments may begin: it is initiated by the hierarchical fragmentation of a dense filament from 10 pc down to 0.01 pc, and the stellar mass buildup is simultaneously fed by hierarchical accretion at similar scales. The new scenario points out the importance of turbulence and filamentary structure, which are now receiving increasing attention and further tests from both observers and theorists.

Author: Derek Ward-Thompson
Publisher: Cambridge University Press
ISBN: 1139494473
Category : Science
Languages : en
Pages : 229

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Guiding the reader through all the stages that lead to the formation of a star such as our Sun, this advanced textbook provides students with a complete overview of star formation. It examines the underlying physical processes that govern the evolution from a molecular cloud core to a main-sequence star, and focuses on the formation of solar-mass stars. Each chapter combines theory and observation, helping readers to connect with and understand the theory behind star formation. Beginning with an explanation of the interstellar medium and molecular clouds as sites of star formation, subsequent chapters address the building of typical stars and the formation of high-mass stars, concluding with a discussion of the by-products and consequences of star formation. This is a unique, self-contained text with sufficient background information for self-study, and is ideal for students and professional researchers alike.

Author: Paul A. Crowther
Publisher:
ISBN:
Category : Stars
Languages : en
Pages : 524

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Author: Edvige Corbelli
Publisher: Taylor & Francis
ISBN: 9781402034060
Category : Science
Languages : en
Pages : 584

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This book presents the proceedings of a conference held in celebration of the 50th anniversary of the introduction of the Initial Mass Function (IMF) concept by Ed Salpeter along with Ed Salpeter's 80th birthday. It provides a vast amount of information, and updates the Herstmonceux book on the IMF. This volume goes far beyond a regular proceedings in that it presents a large collection of long reviews on IMF determinations in the Galaxy, in galaxies, and in the Early Universe. In addition, the book includes reviews on the deep implications of the IMF on star formation theories, and on the physical conditions of the gas before and after star formation. As a consequence, the reader will find a lot of basic information needed for graduate courses on Stellar Evolution, Star Formation, Interstellar Medium, Galactic Dynamics, Formation and Evolution of Galaxies. The book covers all aspects of the current research in this field, as testified by the large number of contributing scientists.

Author: Erica June Nelson
Publisher:
ISBN:
Category : Galaxies
Languages : en
Pages : 282

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A high resolution measurement of the distribution of star formation within galaxies is key to understanding the emergence of galactic structure. The aim of this thesis is to understand how the structure of galaxies is built by developing a new method to spatially resolve their star formation. Using Ha maps for 2676 galaxies, this thesis shows where star formation is distributed in galaxies during the epoch 0.7 z 1.5 when a third of the total star formation in the history of the universe occurred. Across the star formation rate - stellar mass plane (the "main sequence"), star formation is `spatially coherent': in galaxies with higher than average star formation rates, Ha is enhanced throughout the disk; similarly, in galaxies with low star formation rates Ha is depressed throughout the disk. This places constraints both on the mechanisms for enhancing and quenching star formation as well as on how the structure of galaxies is built. The disk scale length of star formation in galaxies is larger than that of the stars, a direct demonstration that the disks of galaxies grow inside-out. While most star formation in most galaxies occurs in disks, not all of it does. With the first spatially resolved measurement of the Balmer decrement at z 1, it can be seen that galaxies with M* 1010M have significant dust attenuation toward their centers. This means that we are witnessing the build-up of the dense stellar cores of massive galaxies through dust-obscured in-situ star formation. The most massive galaxies are thought to have formed their dense stellar cores at even earlier cosmic epochs. This thesis presents the first confirmed example of a massive galaxy core in the process of formation at z = 2.3. It has one of the highest velocity dispersions ever measured for a normal star forming galaxy and also appears to be building through very dense, dust-enshrouded star formation.

Author: Bo Reipurth
Publisher: University of Arizona Press
ISBN: 9780816526543
Category : Science
Languages : en
Pages : 994

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'Protostars and Planets V' builds on the latest results from recent advances in ground and space-based astronomy and in numerical computing techniques to offer the most detailed and up-to-date picture of star and planet formation - including the formation and early evolution of our own solar system.