The Initial Conditions of Clustered Star Formation: an Observational Study of Dense Gas in the Ophiuchus Molecular Cloud

The Initial Conditions of Clustered Star Formation: an Observational Study of Dense Gas in the Ophiuchus Molecular Cloud
Author:
Publisher:
Total Pages:
Release: 2005
Genre:
ISBN:

In this dissertation I present a detailed survey of molecular line emission (including NH3, C2S, HC5N, N2H+, N2D+ and H2D+) towards clustered star forming Cores in the nearby Ophiuchus molecular cloud, with the aim of characterizing the distribution and kinematics of the dense gas within a clustered star forming environment and compare these results with those found in more isolated star forming regions. I show that the dense Oph Cores present characteristics of both isolated and clustered star forming regions in several key parameters, including Core kinematics, temperatures and chemistry. At the higher gas densities where the N2H+ emission is excited, I show that the presence of an embedded protostar is correlated with increased gas motions. I additionally present evidence of N2H+ depletion from the gas phase, suggesting that in higher density, clustered environments N2H+ may not accurately trace the physical conditions of the densest core gas. I present the distribution of H2D+ and N2D+ across the Oph B Core, and show the distribution is not simple or easily explained by chemical models of evolving, isolated cores. Finally, I summarize the results of this dissertation, the questions it raises concerning the exploration of how stars form in clusters, and discuss how these questions may be answered through upcoming observational surveys and by new telescope facilities.

The Physics of Star Formation and Early Stellar Evolution

The Physics of Star Formation and Early Stellar Evolution
Author: Charles J. Lada
Publisher: Springer Science & Business Media
Total Pages: 779
Release: 2012-12-06
Genre: Science
ISBN: 9401136424

The origin of stars is one of the principle mysteries of nature. During the last two decades advances in technology have enabled more progress to be made in the quest to understand stellar origins than at any other time in history. The study of star formation has developed into one of the most important branches of mod ern astrophysical research. A large body of observational data and a considerable literat ure now exist concerning this topic and a 1arge community of international astronomers and physicists devote their efforts attempting to decipher the secrets of stellar birth. Yet, the young astronomerjphysicist or more advanced researcher desiring to obtain a basic background in this area of research must sift through a very diverse and sometimes bewildering literature. A literature which includes research in many discip1ines and sub discip1ines of classical astrophysics from stel lar structure to the interstellar medium and encompasses the entire range of the electromagnetic spectrum from radio to gamma rays. Often, the reward of a suc cessfu1 foray through the current literature is the realization that the results can be obsolete and outdated as soon as the ink is dry in the journal or the conference proceeding in which they are published.

The Dynamical Evolution of Young Star Clusters

The Dynamical Evolution of Young Star Clusters
Author: Richard James Allison
Publisher:
Total Pages:
Release: 2010
Genre:
ISBN:

Stars form in large clouds of cold, dense molecular gas. In these clouds the majority of stars do not form in isolation, but instead form in clusters. The formation of stars and their hos~ clusters are intrinsically linked, and thus to fully understand how stars form we must also understand the formation and early evolution of stellar clusters. The formation of stars is thought to be governed by the turbulent conditions inside these molecular clouds, and due to this the initial conditions of star formation are likely to be spatially complex and dynamically cool. In this Thesis we use fractal spatial distributions (D = 1.6,2.0,2.6 and 3.0) to mimic the complex initial conditions of star formation to investigate how the dynamical evolution of star clusters is affected by variations in the amount of primordial structure. We also use varying initial virial ratios (Q = 0.3, 0.4 and 0.5) to investigate what affect the initial kinematics have on a clusters dynamical evolution. I present a new method, based on the minimum spanning tree, which is able to determine and quantify the presence of mass segregation. The method is applied to observations of the ONe, ,vhich we find to be complexly mass segregated, with different levels of mass segregation depending on stellar mass. We find, contrary to common belief, that mass segregation can occur through purely dynamical processes on a short timescale (rv the initial cluster crossing time). We also find that the amount of dynamical mass segregation that occurs is dependant on both the initial structure and virial ratio, where cooler and more structured initial conditions tend to lead to more dramatic dynamical evolution. Additionally, we find that the clumpy and cool initial conditions also lead to the dynamical formation of high-mass multiple systems, which in turn can lead to the ejection of high-mass stars and the destruction of the host cluster itself.

Present-day and Early Star Formation

Present-day and Early Star Formation
Author: Anne-Katharina Jappsen
Publisher: Sudwestdeutscher Verlag Fur Hochschulschriften AG
Total Pages: 152
Release: 2009
Genre:
ISBN: 9783838104171

Stars form from molecular cloud cores by gravoturbulent fragmentation. Understanding the angular momentum and the thermal evolution of cloud cores thus plays a fundamental role in completing the theoretical picture of star formation. This is true not only for current star formation as observed in regions like the Orion nebula or the -Ophiuchi molecular cloud but also for the formation of stars of the first or second generation in the universe. In this thesis we show how the angular momentum of prestellar and protostellar cores evolves and compare our results from hydrodynamical simulations with observed quantities. We find that collapse induced by gravoturbulent fragmentation is accompanied by a substantial loss of specific angular momentum. This eases the "angular momentum problem" in star formation. The distribution of stellar masses at birth (the initial mass function, IMF) is another aspect that any theory of star formation must explain. Our investigation generally supports the idea that the distribution of stellar masses depends mainly on the thermodynamic state of the gas.

Literature 1977, Part 2

Literature 1977, Part 2
Author: Siegfried Böhme
Publisher: Springer Science & Business Media
Total Pages: 796
Release: 2013-03-14
Genre: Science
ISBN: 366212310X

Astronomy and Astrophysics Abstracts, which has appeared in semi-annual volumes since 1969, is de voted to the recording, summarizing and indexing of astronomical publications throughout the world. It is prepared under the auspices of the International Astronomical Union (according to a resolution adopted at the 14th General Assembly in 1970). Astronomy and Astrophysics Abstracts aims to present a comprehensive documentation of literature in all fields of astronomy and astrophysics. Every effort will be made to ensure that the average time interval between the date of receipt of the original literature and publication of the abstracts will not exceed eight months. This time interval is near to that achieved by monthly abstracting journals, com pared to which our system of accumulating abstracts for about six months offers the advantage of greater convenience for the user. Volume 20 contains literature published in 1977 and received before February 20, 1978; some older literature which was received late and which is not recorded in earlier volumes is also included. We acknowledge with thanks contributions to this volume by Dr. J. BouSka, Prague, who surveyed journals and publications in Czech and supplied us with abstracts in English, and by Prof. P. Brosche, Bonn, who supplied us with literature concerning some border fields of astronomy.

From Dust To Stars

From Dust To Stars
Author: Norbert S. Schulz
Publisher: Springer Science & Business Media
Total Pages: 409
Release: 2007-03-06
Genre: Science
ISBN: 3540273212

Studies of stellar formation in galaxies have a profound impact on our understanding of the present and the early universe. The book describes complex physical processes involved in the creation of stars and during their young lives. It illustrates how these processes reveal themselves from radio wavelengths to high energy X-rays and gamma -rays, with special reference towards high energy signatures. Several sections devoted to key analysis techniques demonstrate how modern research in this field is pursued.