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High Redshift Star-Forming Galaxies in Absorption and Emission

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High Redshift Star-Forming Galaxies in Absorption and Emission University of Cambridge Institute of Astronomy a dissertation submitted to the University of Cambridge for the degree of Doctor of Philosophy High Redshift Star-Forming Galaxies in Absorption and Emission Anna Marie Quider Churchill College Submitted to the Board of Graduate Studies June 2011 Under the Supervision of Professor Max Pettini Dedicated to: G. Alec Stewart, William Stuckwisch, and Timothy Williamson Inspirational educators and friends \The teacher who is indeed wise does not bid you to enter the house of his wisdom but rather leads you to the threshold of your mind." { Khalil Gibran i ii DECLARATION OF ORIGINALITY I, Anna Marie Quider, declare that this thesis titled, `High Redshift Star-Forming Galax- ies in Absorption and Emission' and the work presented in it are my own. I confirm that: • This work was done wholly while in candidature for a research degree at this Uni- versity. • This thesis has not previously been submitted for a degree or any other qualification at this University or any other institution. • Where I have consulted the published work of others, this is always clearly at- tributed, especially in Chapter 1 which serves as an introduction and largely draws on work in the literature. • Where I have quoted from the work of others, the source is always given. With the exception of quotations or figures that are credited to others, this thesis is entirely my own work. • I have acknowledged all main sources of help in the Acknowledgements. • Where the thesis is based on work done by myself jointly with others, I have made clear exactly what was done by others and what I have contributed myself. All writing has been put together by myself. • The length of this thesis does not exceed the stated limit of the Degree Committee of Physics and Chemistry of 60,000 words. Signed Date iii iv Summary High Redshift Star-Forming Galaxies in Absorption and Emission Anna M. Quider Galaxies in the redshift range 1 < z < 3 existed during the most vigorous period of star formation in the history of the Universe. In the past 15 years, large rest-frame UV spectroscopic samples of z ∼ 3 star-forming galaxies have been assembled. However, this particular redshift range, the so-called Redshift Desert, has only begun to be character- ized. Most studies involve low resolution, low signal-to-noise spectra because the small 00 angular size (δ ≤ 1 ) and faintness (RAB = 24 − 25:5) of high redshift galaxies limit what can be accomplished with a reasonable investment of observing time, even using the world's largest optical telescopes. One way to circumvent these two issues is to study gravitationally lensed galaxies. The magnification boost (up to a factor of 30×) and morphological distortion of a high redshift galaxy by an intervening mass concentration allow for the study of the high redshift Universe in unprecedented detail. I present a detailed analysis of the rest-UV spectrum of two gravitationally lensed galaxies: the `Cosmic Horseshoe' (zsys = 2:38115) and the `Cosmic Eye' (zsys = 3:07331). The characterization of the stellar populations and the interstellar gas geometry, kinematics, and composition which I achieve is a preview of the type of information that will be available for unlensed high redshift galaxies with the next generation of optical telescopes. I probe the lower redshift end of the Redshift Desert with a study of Fe ii and Mg ii features in the rest-frame near-UV spectrum of 96 star-forming galaxies in the redshift range 1 < z < 2. Stacked spectra are used to explore average outflow and line profile trends with stellar mass and reddening. I also investigate the phenomenon of emission filling of absorption lines which has implications for the line strength and velocity offset of interstellar absorption lines. Individual galaxies are used to assess the range of outflow velocities as well as the prevalence of emission filling in galaxies from this epoch. This is the first large scale study of fine-structure emission from Fe ii in high redshift galaxies, both in stacked and individual galaxy spectra. An alternative to investigating galaxies by collecting their light is to study them as seen in absorption against a cosmic backlight, such as a quasar. The Sloan Digital Sky Survey, an imaging and spectroscopic survey which covers about one-quarter of the night sky, has collected many thousands of quasar spectra. I search ∼ 44 600 of these spectra, up through Data Release 4, for Mg ii λλ2796,2803 absorption doublets. The final catalog includes ∼ 16 700 Mg ii absorption line systems in the redshift range 0:36 ≤ z ≤ 2:28. Measurements of the absorption redshift and rest equivalent widths of the Mg ii doublet as well as select metal lines are available in the catalog. This is the largest publicly available catalog of its kind and its combination of large size and well understood statistics make it ideal for precision studies of the low-ionization and neutral gas regions of galaxies. I conclude this thesis by suggesting several avenues for extending the studies of high redshift star-forming galaxies presented herein. v vi Acknowledgments As with so many things, this thesis is more than the sum of its parts. It represents the many people I've known and the many experiences I've had, all leaving their mark on me and contributing in large and small ways to this document. At the forefront are G. Alec \Doc" Stewart, Bill Stuckwisch, and Tim Williamson: three extraordinary educators who have significantly shaped how I think about the world (both natural and otherwise) and my connection to it. Their curiosity, passion, joyfulness, and belief in me have continually inspired and sustained me throughout the years. I am particularly indebted to Mr Stuckwisch for his supervision of my first independent science experiment; perhaps someday I'll live down the horse manure I accidentally spilled in the GIHS chemistry lab. My scientific mentors and collaborators have greatly contributed to this work. Thank you to Max Pettini for his patient guidance, tireless encouragement, and knowledgable conversations throughout the past four years. The Pittsburgh Quasar Research Group has been like a second family to me|particularly Dave Turnshek, Sandhya Rao, and Dan Nestor|and I have enjoyed our many years of scientific discourse and friendship. I am also indebted to my collaborators: Joe Busche, Dawn Erb, Alaina Henry, Crystal Martin, Eric Monier, Alice Shapley, Dan Stark, Chuck Steidel, and Anja Weyant. I am fortunate to have many, many wonderful people in my life. My family is possibly the most loving and enthusiastic group of people ever assembled. Their unwavering love and encouragement have buoyed me while pursuing this degree and living abroad. My fantastic officemates Matt and James deserve a standing ovation for adapting to life in very close quarters with me (including my inability to speak with an `inside' voice) and for helping me sort out nearly every manner of problem imaginable. My life has been incredibly enriched by amazing friendships. I could not have completed this journey without having friends from both sides of the ocean along for the ride. There are numerous institutions/organizations which have made this work possible. Thank you to Churchill College, and Rebecca Sawalmeh in particular, for making me feel at home in this country. The administrative staff of the Institute of Astronomy (Si^an, Margaret, and Bev) are phenomenal miracle-workers who kept this whole operation on course. Generous funding for this work was provided by the Marshall Aid Commemora- tion Commission, the National Science Foundation Graduate Research Fellowship, and the Cambridge Overseas Trusts. Taking a broader perspective, the completion of this thesis is founded on the excellent education I received from the Bennett Park Montessori Center (Buffalo PS#32), Grand Island Middle School, Grand Island High School, and the University of Pittsburgh. Thank you to all the dedicated educators I have learned from along the way. Finally, I can't help but be struck by the incredible good fortune that has led me to complete this thesis. An unfortunate reality is that an education is not available to all who desire it. I applaud those people who fight for their right to develop their intellectual potential in any area they choose. I mourn those people who cannot fulfill their potential, in particular my good friend Jon Kaufman who passed away while a Physics Ph.D. student. Thoughts of these individuals have motivated me throughout this work. vii viii Contents 1 Introduction 1 1.1 Why Care About the Young Universe? . .1 1.2 LBG Photometric Selection Technique . .3 1.3 Low Resolution UV Spectra . .6 1.3.1 Individual spectra . .6 1.3.2 Composite spectra . .8 1.4 High Resolution Rest-UV Spectroscopy . .9 1.4.1 Gravitational lensing: nature's telescope . 10 1.4.2 The galaxy MS 1512−cB58 . 12 1.5 Quasar Absorption Lines . 16 1.6 Organisational Notes . 21 2 Instruments and Data Processing 23 2.1 Keck Telescopes . 23 2.1.1 Echellette Spectrograph and Imager (ESI) . 23 2.1.2 DEep Imaging Multi-Object Spectrograph (DEIMOS) . 32 2.2 Sloan Digital Sky Survey (SDSS) . 35 3 Rest-Frame UV Spectrum of `The Cosmic Horseshoe' 39 3.1 Introduction . 39 3.2 The Cosmic Horseshoe . 41 3.3 Observations and Data Reduction . 42 3.4 The Stellar Spectrum . 42 3.4.1 The systemic redshift of the Cosmic Horseshoe . 44 3.4.2 Photospheric lines . 44 3.4.3 Wind lines . 47 3.5 The Interstellar Spectrum . 50 3.5.1 Kinematics of the absorbing gas . 50 3.5.2 Partial coverage and column densities . 52 3.6 The Lyα Line .
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