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| Author | : Sean McBride |
| Publisher | : |
| Total Pages | : 0 |
| Release | : |
| Genre | : Cosmic dust |
| ISBN | : |
| Author | : Tony Wong |
| Publisher | : Cambridge University Press |
| Total Pages | : 0 |
| Release | : 2013-04-11 |
| Genre | : Science |
| ISBN | : 9781107033818 |
Our knowledge of the molecular gas content in galaxies has advanced rapidly in the past decade with systematic surveys from ground-based radio facilities, coupled with advances in observations and modeling of the thermal dust emission associated with the gas. This Symposium Proceedings provides a timely overview of the latest observations of molecular gas and dust in the Milky Way and in other galaxies. It also covers related topics including the initial conditions for star formation, observational tracers of star formation and interstellar conditions, and simulations of the turbulent, multiphase interstellar medium. Featuring ten review articles by leaders in the field, and including early results and prospects for the ALMA observatory, this volume will prove especially useful for graduate students or scientists who are pursuing or planning research in this area.
| Author | : Sedona H. Price |
| Publisher | : |
| Total Pages | : 141 |
| Release | : 2017 |
| Genre | : |
| ISBN | : |
Understanding the physical processes governing galaxy growth and evolution remains an outstanding challenge in astronomy. Constraining these processes requires observations at multiple epochs, but despite exquisite observations of galaxies in the local universe, relatively little is known about galaxies at early times. In the last decade, large photometric surveys have revealed many details about galaxies across the past 10 billion years. However, fully understanding galaxies in the early universe and how they connect to today's galaxy population requires observations of their physical properties through spectroscopy as well as photometry. Recent instrumentation advances have now paved the way for spectroscopic surveys of large samples of distant galaxies, which provide key insights into the earlier phases of galaxy evolution. In this dissertation, I use detailed photometric and spectroscopic observations and simulations to investigate the dust content, masses, and kinematic structures of star-forming galaxies at z~1.5-3, near the peak of cosmic star formation. I present results using Hubble Space Telescope (HST) grism observations of an unbiased sample of galaxies at z~1.5 from the 3D-HST survey to measure the relation between nebular and stellar dust attenuation. These constraints on the dust content of distant galaxies enable accurate measurements of star formation rates, and help to characterize the dust distribution in early galaxies. I also investigate the internal kinematics of galaxies at z~1.5-3 using moderate-resolution near-infrared spectra from the MOSDEF survey with Keck/MOSFIRE together with high spatial-resolution HST imaging. I develop a set of models to measure and interpret kinematics from spectra taken with galaxy-slit misalignments, including galaxies without spatially-resolved spectra. I then use these models to derive independent, dynamical estimates of the galaxy masses, and to constrain the amount of support from ordered versus random motions for hundreds of galaxies with Mstar ~ 10^9 - 10^11.5 Msun. Additionally, I explore the correlation of kinematic structure with other properties and constrain how the dark matter fraction in star-forming galaxies changes over time. Finally, I use mock observations of galaxies from the high-resolution MassiveFIRE cosmological simulation suite to determine how well intrinsic galaxy sizes and stellar masses are recovered from observations. I also explore the impact of random viewing angles on observed galaxy properties, which has implications for the interpretation of the scatter in galaxy scaling relations.
| Author | : Xinnan Du |
| Publisher | : |
| Total Pages | : 191 |
| Release | : 2018 |
| Genre | : |
| ISBN | : |
Rest-frame ultraviolet (UV) and optical spectroscopy provides valuable information on the physical properties of the neutral and ionized interstellar medium (ISM) in star-forming galaxies. Such observations probe both the systemic interstellar component originating from H II regions, and the multi-phase outflowing component that is associated with star-formation feedback and can ultimately contribute to the circumgalactic and even intergalactic medium (CGM and IGM, respectively). In this dissertation, I investigate the physical properties of ionized gas in star-forming regions, and the kinematics and evolution of the multi-phase outflowing ISM/CGM in distant star-forming galaxies spanning the redshift range z ~ 1-4. This work consists of three studies that examine different aspects of the ISM and CGM, which collectively improve our understanding of the gas content in galaxies and the processes associated with the formation of massive stars near the peak of the star-formation-rate (SFR) density in the universe. I present a comparison of kinematics between the low- and high-ionization absorption features at z ~ 1, and demonstrate that the apparent larger blueshift of interstellar C IV relative to the low-ionization features is likely a result from the nature of resonant transitions instead of an evidence of the faster motion of the highly ionized gas. I further investigate the origin of the highly ionized gas by examining the correlations between the spectral properties of C IV and various galaxy properties. Both the blueshift and equivalent width (EW) of C IV are modulated by SFR and specific SFR, suggesting a direct connection between the highly ionized gas and the formation of massive stars. Nebular emission features provide valuable insights into the physical conditions of the ionized gas in H II regions, as well as the properties of young, massive stars. I show that the nebular C III] emission at z ~ 1 is much weaker compared to the detections from galaxies observed during the epoch of reionization (z > 6), and explore the factors that modulate the strength of this nebular feature. In combination with the results from photoionization models, I further infer the gas-phase metallicity and abundance pattern in the z ~ 1 star-forming galaxies based on the observed rest-frame C III] EW. Studying the lower-redshift analogs of the z > 6 C III] emitters is an alternative way to obtain more detailed information on the physical properties of these extreme-emission-line-galaxies (EELGs). By assembling a sample of EELGs at z ~ 1-2 and examining C III] and other nebular emission features, I aim to characterize the physical conditions of the z > 6 galaxies that are likely responsible for the cosmic reionization. Finally, with carefully constructed samples and uniform measurements, I investigate the evolution of the ISM/CGM at z ~ 2-4 as probed by rest-UV spectroscopy. I discover redshift-independent correlations among Lya emission, low-ionization interstellar absorption lines, and dust extinction. I further show that the covering fraction of neutral gas decreases with increasing redshift at multiple fixed galaxy properties. Gaining a full understanding of galaxy evolution requires further studies of the ISM/CGM in a systemic manner at higher redshifts. With exceptional capabilities in the near-IR and excellent spectroscopic sensitivity, the next generation of large telescopes will enable rest-UV and rest-optical spectroscopic studies of star-forming galaxies out to z > 10. Answering key questions regarding the interplay among massive stars, their contribution to the ionizing background, and feedback will deliver a clear picture of the formation and evolution of these distant star-forming galaxies.
| Author | : Seiji Fujimoto |
| Publisher | : Springer Nature |
| Total Pages | : 163 |
| Release | : 2022-01-05 |
| Genre | : Science |
| ISBN | : 9811649790 |
This book presents the cold side of the Universe illustrated by the rest-frame, far-infrared emission with Atacama Large Millimeter/submillimeter Array (ALMA). The author constructed the largest-ever ALMA sample and dataset, which enables them to identify very faint, rest-frame, far-infrared dust continuums as well as the carbon fine-structure line emission from distant galaxies that have been missed in previous surveys. The observational findings described in this book reveal for the first time where and how much of the star formation, traced by the rest-frame far-infrared emission, is ongoing, from inter-stellar and circum-galactic media to cosmic structures. Moreover, since some of the findings are unexpected and as such challenge the current galaxy formation models, the book provides exciting questions that should be addressed in the next decades.
| Author | : William Cowley |
| Publisher | : Springer |
| Total Pages | : 221 |
| Release | : 2017-10-02 |
| Genre | : Science |
| ISBN | : 3319667483 |
This thesis combines a theoretical model of galaxy formation with a treatment of the radiative transfer in the titular dusty star-forming galaxies. Embedding this within the well-established ΛCDM (Lambda cold dark matter) cosmology, the author was able to simulate galaxy populations from which realistic observational images were synthesised. Based on further analysis, he shows that there is a good correspondence with observations from new instruments such as the SCUBA2 bolometric camera and the Atacama Large Millimeter Array (ALMA) interferometer, and reveals some novel aspects of this exciting galaxy population. In particular, he shows that blending of these galaxies in the imaging produces an artificial enhancement in their clustering, which he dubs “blending bias”. This implies that the host dark matter halo masses for these galaxies have previously been significantly overestimated. He also presents amongst the first predictions from a galaxy formation model for observations of these galaxies that will be made by the James Webb Space Telescope (the successor to the Hubble Space Telescope).
| Author | : Richard J. Tuffs |
| Publisher | : Cambridge University Press |
| Total Pages | : 533 |
| Release | : 2012-08-30 |
| Genre | : Science |
| ISBN | : 9781107019843 |
Recent observational developments are providing the first truly panchromatic view of galaxies, extending from the radio to TeV gamma-rays. This is motivating the development of new models for the interpretation of spectral energy distributions (SEDs) of galaxies in terms of the formation, evolution and emission of stellar and accretion-driven sources of photons, the interaction of the photons with the gaseous and dust components of the interstellar medium, and high-energy processes involving cosmic rays. IAU Symposium 284 details progress in the development of such models, their relation to fundamental theory, and their application to the interpretation of the panchromatic emission from the Milky Way and nearby galaxies, connecting the latter with models for the evolution of the SEDs of distant galaxies, and the extragalactic background light. IAU S284 is a useful resource for all researchers working with the copious amounts of multiwavelength data for galaxies now becoming available.
| Author | : Houjun Mo |
| Publisher | : Cambridge University Press |
| Total Pages | : 841 |
| Release | : 2010-05-20 |
| Genre | : Science |
| ISBN | : 0521857937 |
A coherent introduction for researchers in astronomy, particle physics, and cosmology on the formation and evolution of galaxies.
| Author | : Hagai Netzer |
| Publisher | : Cambridge University Press |
| Total Pages | : 369 |
| Release | : 2013-09-16 |
| Genre | : Science |
| ISBN | : 1107021510 |
A comprehensive introduction to the theory underpinning our study of active galactic nuclei and the ways we observe them.
| Author | : Skarleth M. Motino Flores |
| Publisher | : |
| Total Pages | : 136 |
| Release | : 2021 |
| Genre | : Blue Compact Dwarf Galaxy |
| ISBN | : |
The universe is constantly changing, astronomers learn about its evolution through carefulobservation of the physical processes happening. For instance, observing our own galaxy we nd star-forming regions, where stars are born after the gravitational collapse of large gas clouds. The life of a star is extended until there is no more gas to burn. Massive stars die with a tremendous supernova explosion, potentially forming black-holes, releasing heavy elements into the interstellar medium in this process. Star formation converts gas into stars, and without gas available is not possible to form stars. The entire life cycle of a star occurs inside a galaxy. Understanding the physical processes driving galaxy formation and evolution is one of the most important goals of observational cosmology. It is also one of the most dicult problems to address due to the large distances and time scales involved. When observing the most distant universe, also known as the high-redshift (high-z) universe, we are observing the young universe, where the rst galaxies were formed. The faintness and small sizes of galaxies in the early universe make detailed observations extremely challenging with current telescopes. An alternative and complementary approach is to identify nearby galaxies that are analogs to distant galaxies, where the physical processes can be studied in greater detail than what is possible in high-z galaxies. I have therefore selected a sample of nearby star-forming galaxies that are potential local analogs to high-z galaxies. These local galaxies are young, star-forming, have low metallicities, and are likely to have star formation histories (SFH) similar to the high-z galaxies. In order to characterize these galaxies, I use observations with the SOFIA telescope together with ancillary data, to study their dust properties and how it is related to the star formation activity. I also use FIR fiine-structure lines to identify the neutral and ionized gas components in the galaxies. My overall aim is to produce a detailed characterization of the properties of the local galaxies and determine their SFH and analyze their connection with photometric and spectroscopic results for high-z galaxies obtained with Herschel and ALMA. In this thesis, I present the dust emission characterization through a two-component black-body, derived using infrared observations with SOFIA/HAWC+ instrument and ancillary data from Spitzer, Herschel, among others. Then I present the spectral energy distribution (SED) from ultraviolet to far-infrared wavelengths for the local analogs to high-z galaxies, which is derived using the fitting procedure Lightning. Also, the ionized gas is characterized by the [CII]-158m and [OIII]-88m fine-structure lines using the SOFIA/FIFI-LS integral eld unit (IFU). These lines are accessible with ALMA for high-z objects and my results for the local analogs can be used to infer the interstellar medium properties of the high-z galaxies.
