Download or read book Ultracompact H II Regions Associated with Massive Star Formation written by Douglas Wood (Owen Starkey) and published by . This book was released on 1988 with total page 496 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Tracing Massive Star Formation Through a Galactic Census of Compact Ultracompact HII Regions written by Julie Djordjevic and published by . This book was released on 2019 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Ultracompact HII Regions written by Edward B. Churchwell and published by . This book was released on 1990 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book A Multiwavelength Study of Massive Star Formation Regions written by Marta Malgorzata Sewilo and published by . This book was released on 2006 with total page 258 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book A Study of the Hot Molecular Gas Associated with Ultracompact HII Regions written by Peter Höfner and published by . This book was released on 1995 with total page 422 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Understanding Spatial and Spectral Morphologies of Ultracompact H II Regions written by and published by . This book was released on 2010 with total page 15 pages. Available in PDF, EPUB and Kindle. Book excerpt: The spatial morphology, spectral characteristics, and time variability of ultracompact H II regions provide strong constraints on the process of massive star formation. We have performed simulations of the gravitational collapse of rotating molecular cloud cores, including treatments of the propagation of ionizing and non-ionizing radiation. We here present synthetic radio continuum observations of H II regions from our collapse simulations, to investigate how well they agree with observation, and what we can learn about how massive star formation proceeds. We find that intermittent shielding by dense filaments in the gravitationally unstable accretion flow around the massive star leads to highly variable H II regions that do not grow monotonically, but rather flicker, growing and shrinking repeatedly. This behavior appears able to resolve the well-known lifetime problem. We find that multiple ionizing sources generally form, resulting in groups of ultracompact H II regions, consistent with observations. We confirm that our model reproduces the qualitative H II region morphologies found in surveys, with generally consistent relative frequencies. We also find that simulated spectral energy distributions (SEDs) from our model are consistent with the range of observed H II region SEDs, including both regions showing a normal transition from optically thick to optically thin emission, and those with intermediate spectral slopes. In our models, anomalous slopes are solely produced by inhomogeneities in the H II region, with no contribution from dust emission at millimeter or submillimeter wavelengths. We conclude that many observed characteristics of ultracompact H II regions appear consistent with massive star formation in fast, gravitationally unstable, accretion flows.
Download or read book Astrophysical Masers and Their Environments IAU S242 written by International Astronomical Union. Symposium and published by Cambridge University Press. This book was released on 2008-02-14 with total page 564 pages. Available in PDF, EPUB and Kindle. Book excerpt: Astrophysical masers, naturally occurring microwave and radio-wave emissions, provide an important tool to investigate astrophysical environments. Several thousand maser sources have been observed in the interstellar medium and star formation regions, in the expanding winds from evolved stars, in the compressed shells of supernovae remnants, in comets and in the centers of galaxies. Masers are also useful for studying the structure and dynamics of our own galaxy, while masers in other galaxies are now used for cosmological studies and studies of galactic nuclei. This volume contains the latest research on the topic as presented at IAU Symposium 242, only the third international symposium on astrophysical masers. Over 125 astronomers from 18 different countries gathered in Alice Spring, Australia, for discussions on maser research.
Download or read book The Galactic Interstellar Medium written by W.B. Burton and published by Springer Science & Business Media. This book was released on 2006-04-18 with total page 409 pages. Available in PDF, EPUB and Kindle. Book excerpt: The previous Saas-Fee Advanced Course dedicated to the interstellar medium took place in 1972. The tremendous scientific advances that have occurred in this field since then, in particular owing to the availabihty of receivers working at completely unexplored wavelength bands, fuUy justified a new set of lectures. As a consequence, the members of the Swiss Society for Astrophysics and As tronomy voted that "The Galactic Interstellar Medium" should be the subject of the 1991 course. The 21st Saas Fee Advanced Course took place in Les Diablerets from 18 to 23 March 1991, gathering together about 80 participants from all over the world, but mostly from Europe. According to a rule that has proved to lead to success, but also to chal lenge the lecturers' energy, the format of a Saas-Fee Advanced Course consists traditionally of 28 lectures of 45 minutes which take place in the morning and late afternoon, leaving ample time for discussions, self-study, hiking or skiing. Despite the inordinate work load imposed, this year's lecturers felt that the subject was sufficiently dense to increase the lecture time by 1/3! This proved judicious and left more time for questions and discussions during the lectures.
Download or read book The Interplay Between Massive Star Formation the ISM and Galaxy Evolution written by D. Kunth and published by Atlantica Séguier Frontières. This book was released on 1996 with total page 668 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Hot Cores and HII Regions written by Chocolate Genius (Singer) and published by . This book was released on 1999 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Ionization Feedback in Massive Star Formation written by Thomas Peters and published by Sudwestdeutscher Verlag Fur Hochschulschriften AG. This book was released on 2010-11 with total page 152 pages. Available in PDF, EPUB and Kindle. Book excerpt: Understanding the origin of high-mass stars is central to modern astrophysics. We shed light on this problem using novel radiation-hydrodynamic simulations that consistently follow the gravitational collapse of a massive molecular cloud, the subsequent build-up and fragmentation of the accretion disk surrounding the nascent star, and, for the first time, the interaction between its intense UV radiation field and the infalling material. We show that ionization feedback can neither stop protostellar mass growth nor suppress fragmentation. We present a consistent picture of the formation and evolution of H II regions that explains the observed morphology, time variability, and ages of ultracompact H II regions, solving the long-standing lifetime problem.
Download or read book Physics of Star Formation in Galaxies written by F. Palla and published by Springer Science & Business Media. This book was released on 2006-07-06 with total page 242 pages. Available in PDF, EPUB and Kindle. Book excerpt: The book begins with a historical introduction, "Star Formation: The Early History", that presents new material of interest for students and historians of science. This is followed by two long articles on "Pre-Main-Sequence Evolution of Stars and Young Clusters" and "Observations of Young Stellar Objects". These articles on the fascinating problem of star formation from interstellar matter give a thorough overview of present-day theories and observations. The articles contain material so far unpublished in the astronomical literature. The book addresses graduate students and can be used as a textbook for advanced courses in stellar astrophysics.
Download or read book Radio Emission Toward Regions of Massive Star Formation in the Large Magellanic Cloud written by Adam Johanson and published by . This book was released on 2015 with total page 77 pages. Available in PDF, EPUB and Kindle. Book excerpt: Four regions of massive star formation in the Large Magellanic Cloud (LMC) were observed for water and methanol maser emission and radio continuum emission. A total of 42 radio detections were made including 27 new radio sources, four water masers, and eight compact HII regions. The lobes of a radio galaxy were resolved for the first time, and the host galaxy identified. Seven sources were associated with known massive young stellar objects (YSOs). A multi-wavelength analysis using both the infrared and radio spectrum was used to characterize the sources. Mid-infrared color-magnitude selection criteria for ultracompact HII (UCHII) regions in the LMC are presented, yielding 136 UCHII region candidates throughout that galaxy. New maser detections identified two previously unknown massive YSOs. No methanol masers were detected, consistent with previous studies and supporting the hypothesis that the LMC may be deficient in these molecules. These discoveries contribute to the history of star formation in the LMC, which will lead to a better understanding of star formation in the Milky Way and throughout the universe.
Download or read book Scientific and Technical Aerospace Reports written by and published by . This book was released on 1991 with total page 268 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Diffuse Matter from Star Forming Regions to Active Galaxies written by T.W. Hartquist and published by Springer Science & Business Media. This book was released on 2007-05-02 with total page 354 pages. Available in PDF, EPUB and Kindle. Book excerpt: John Dyson has contributed to the study of the hydrodynamic processes that govern a wide variety of astrophysical sources which he has helped explain. In this volume dedicated to him, introductory reviews to a number of the key processes and to the sources themselves are given by leading experts. The book provides a coherent introduction to the astrophysics of diffuse sources suitable for postgraduate students and researchers in astrophysics.
Download or read book Physical Processes in the Interstellar Medium written by Lyman Spitzer, Jr. and published by John Wiley & Sons. This book was released on 2008-11-20 with total page 335 pages. Available in PDF, EPUB and Kindle. Book excerpt: Physical Processes in the Interstellar Medium discusses the nature of interstellar matter, with a strong emphasis on basic physical principles, and summarizes the present state of knowledge about the interstellar medium by providing the latest observational data. Physics and chemistry of the interstellar medium are treated, with frequent references to observational results. The overall equilibrium and dynamical state of the interstellar gas are described, with discussions of explosions produced by star birth and star death and the initial phases of cloud collapse leading to star formation.
Download or read book Insights Into High Mass Star Formation from Methanol Maser Observations written by Hontas Freeman Farmer and published by . This book was released on 2013 with total page 63 pages. Available in PDF, EPUB and Kindle. Book excerpt: We present high angular resolution data on Class I and Class II methanol masers, together with other tracers of star formation like H2O masers, ultracompact (UC) ionized hydrogen (H II) regions, and 4.5 μm infrared sources, taken from the literature. The aim is to study what these data tell us about the process of high mass star formation; in particular, whether disk-outflow systems are compatible with the morphology exhibited by Class I and Class II methanol masers. Stars form in the dense cores inside molecular clouds, and while the process of the formation of stars like our Sun is reasonably well understood, details of the formation of stars with masses eight times that of our Sun or greater, the so-called high mass stars, remain a mystery. Being compact and bright sources, masers provide an excellent way to observe high mass star forming regions. In particular, Class II methanol masers are found exclusively in high mass star forming regions. Based on the positions of the Class I and II methanol and H2O masers, UC H II regions and 4.5 μm infrared sources, and the center velocities (vLSR) of the Class I methanol and H2O masers, compared to the vLSR of the Class II methanol masers, we propose three disk-outflow models that may be traced by methanol masers. In all three models, we have located the Class II methanol maser near the protostar, and the Class I methanol maser in the outflow, as is known from observations during the last twenty years. In our first model, the H2O masers trace the linear extent of the outflow. In our second model, the H2O masers are located in a circumstellar disk. In our third model, the H2O masers are located in one or more outflows near the terminating shock where the outflow impacts the ambient interstellar medium. Together, these models reiterate the utility of coordinated high angular resolution observations of high mass star forming regions in maser lines and associated star formation tracers.
