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Author: Alexander John Mendez Publisher: ISBN: 9781321059892 Category : Languages : en Pages : 187
Book Description
This dissertation uses large galaxy redshift surveys and multi-wavelength imaging to place observational constraints on the evolution of galaxies and the supermassive black holes that they host since the Universe was roughly half its current age. In the first chapter, we use data from the AEGIS survey to present quantitative morphological measurements of green valley galaxies, to constrain the mechanism(s) responsible for quenching star formation in this transition population and creating elliptical galaxies. We show that green galaxies are generally massive (M.) ~ 1010·5 M/[sun]) disk galaxies with high concentrations of light. We find that major mergers are not the dominant mechanism responsible for quenching star formation, and we find that either more mild external processes or internal secular processes play a crucial role in halting star formation. In the second chapter, we use data from the PRIMUS survey to investigate Spitzer/IRAC and X-ray AGN selection techniques in order to quantify the overlap, uniqueness, contamination, and completeness of each AGN selection. For roughly similar depth IR and X-ray data, we find that ~75% of IR-selected AGN are also identified as X-ray AGN. For the deepest X-ray data, this fraction increases to ~90%, indicating that at most ~10% of IR-selected AGN may be heavily obscured. While similar overall, the IR-AGN samples preferentially contain more luminous AGN, while the X-ray AGN samples identify AGN with a wider range of accretion rates, where the host galaxy light dominates at IR wavelengths. A more complete AGN sample is created by combining both IR and X-ray selected AGN. Finally, we present a clustering study of X-ray AGN, radio AGN and IR AGN selected AGN using spectroscopic redshifts from the PRIMUS and DEEP2 redshift surveys. Using the cross-correlation of AGN with dense galaxy samples, we find differences in the clustering of AGN selected at different wavelengths. However, we find no significant differences in the clustering of each AGN sample with matched galaxy samples that have the same redshift, stellar mass, and star formation rate distributions. The differences in the clustering of AGN selected at different wavelengths can therefore be explained by the clustering differences of their host populations
Author: Alexander John Mendez Publisher: ISBN: 9781321059892 Category : Languages : en Pages : 187
Book Description
This dissertation uses large galaxy redshift surveys and multi-wavelength imaging to place observational constraints on the evolution of galaxies and the supermassive black holes that they host since the Universe was roughly half its current age. In the first chapter, we use data from the AEGIS survey to present quantitative morphological measurements of green valley galaxies, to constrain the mechanism(s) responsible for quenching star formation in this transition population and creating elliptical galaxies. We show that green galaxies are generally massive (M.) ~ 1010·5 M/[sun]) disk galaxies with high concentrations of light. We find that major mergers are not the dominant mechanism responsible for quenching star formation, and we find that either more mild external processes or internal secular processes play a crucial role in halting star formation. In the second chapter, we use data from the PRIMUS survey to investigate Spitzer/IRAC and X-ray AGN selection techniques in order to quantify the overlap, uniqueness, contamination, and completeness of each AGN selection. For roughly similar depth IR and X-ray data, we find that ~75% of IR-selected AGN are also identified as X-ray AGN. For the deepest X-ray data, this fraction increases to ~90%, indicating that at most ~10% of IR-selected AGN may be heavily obscured. While similar overall, the IR-AGN samples preferentially contain more luminous AGN, while the X-ray AGN samples identify AGN with a wider range of accretion rates, where the host galaxy light dominates at IR wavelengths. A more complete AGN sample is created by combining both IR and X-ray selected AGN. Finally, we present a clustering study of X-ray AGN, radio AGN and IR AGN selected AGN using spectroscopic redshifts from the PRIMUS and DEEP2 redshift surveys. Using the cross-correlation of AGN with dense galaxy samples, we find differences in the clustering of AGN selected at different wavelengths. However, we find no significant differences in the clustering of each AGN sample with matched galaxy samples that have the same redshift, stellar mass, and star formation rate distributions. The differences in the clustering of AGN selected at different wavelengths can therefore be explained by the clustering differences of their host populations
Author: T.J.-L. Courvoisier Publisher: Springer ISBN: 9789401095372 Category : Science Languages : en Pages : 0
Book Description
Active Galactic Nuclei radiate over the electro-magnetic spectrum from radio waves to gamma rays. Understanding the physics of these objects therefore requires the synthesis of results from many different domains of Astronomy. It was the aim of the conference "Active Galactic Nuclei across the Electromagnetic Spectrum" to provide a forum where this exchange could take place. Some 300 astronomers participated to the conference, 250 of them presented results either as oral papers or in the form of posters. Observations in all domains of the electro magnetic spectrum in which astronomical observations can be made from the ground or from space were presented. Many theoretical contributions were also given. There has been a tremendous growth in the number and quality of Astronomical obser vations in many spectral domains over the past several years. Students of Active Galactic Nuclei have been particularly keen to make use of the available facilities (both space born and on the ground), often in a very organised way, in order to obtain repeated simultane ous data covering large bands of the spectrum. This approach has produced a qualitatively new set of data for understanding the physics of Active Galactic Nuclei. The task of the meeting was to review this data in a coherent way.
Author: Volker Beckmann Publisher: John Wiley & Sons ISBN: 352766680X Category : Science Languages : en Pages : 390
Book Description
Active Galactic Nuclei This AGN textbook gives an overview on the current knowledge of the Active Galacitc Nuclei phenomenon. The spectral energy distribution will be discussed, pointing out what can be observed in different wavebands. The different physical models are presented together with formula important for the understanding of AGN physics. Furthermore, the authors discuss the AGN with respect to its environment, host galaxy, feedback in galaxies and in clusters of galaxies, variability, etc. and finally the cosmological evolution of the AGN phenomenon. This book includes phenomena based on new results in the X-Ray and gamma-ray domain from new telescopes such as Chandra, XMM-Newton, the Fermi Gamma-Ray Space Telescope, and the VHE regime not mentioned so far in AGN books. Those and other new developments as well as simulations of AGN merging events and formations, enabled through latest super-computing capabilities. From the contents: The observational picture of AGN Radiative processes The central engine AGN types and unification AGN through the electromagnetic spectrum AGN variability Environment Quasars and cosmology Formation, evolution and the ultimate fate of AGN What we do not know (yet)
Author: Bradley M. Peterson Publisher: ISBN: Category : Science Languages : en Pages : 568
Book Description
Annotation Papers from a June 2000 meeting discuss multiwavelength monitoring methods for studying active galactic nuclei, the potential of dedicated facilities for multiwavelength monitoring, and future multiwavelength programs. Some topics discussed are multiwavelength observations of blazars, time delays of blazar flares observed at different wavebands, low radiative-efficiency accretion flows, spectrochronography, and variability of the intrinsic UV absorption lines in Seyfert galaxies. Other topics are the variable diffuse continuum emission of broad-line clouds, the MIDEX concept, and the mission. Peterson teaches astronomy at The Ohio State University. This volume lacks a subject index. Annotation c. Book News, Inc., Portland, OR (booknews.com)
Author: T.J.-L. Courvoisier Publisher: Springer ISBN: 9780792327455 Category : Science Languages : en Pages : 534
Book Description
Active Galactic Nuclei radiate over the electro-magnetic spectrum from radio waves to gamma rays. Understanding the physics of these objects therefore requires the synthesis of results from many different domains of Astronomy. It was the aim of the conference "Active Galactic Nuclei across the Electromagnetic Spectrum" to provide a forum where this exchange could take place. Some 300 astronomers participated to the conference, 250 of them presented results either as oral papers or in the form of posters. Observations in all domains of the electro magnetic spectrum in which astronomical observations can be made from the ground or from space were presented. Many theoretical contributions were also given. There has been a tremendous growth in the number and quality of Astronomical obser vations in many spectral domains over the past several years. Students of Active Galactic Nuclei have been particularly keen to make use of the available facilities (both space born and on the ground), often in a very organised way, in order to obtain repeated simultane ous data covering large bands of the spectrum. This approach has produced a qualitatively new set of data for understanding the physics of Active Galactic Nuclei. The task of the meeting was to review this data in a coherent way.
Author: Anson Lam Publisher: ISBN: Category : Languages : en Pages : 211
Book Description
Traditional methods of identifying active galactic nuclei (AGNs) rely on UV and optical color criteria, but these methods exclude AGNs that are highly optically obscured by surrounding dust. This bias causes underestimates in the number of obscured AGNs in the Universe, and is problematic for our understanding of galaxy evolution and computing luminosity functions. Since much of the radiation absorbed by dust is re-radiated in the IR, mid-IR color selection provides a much more robust method of identifying AGNs that is not biased against highly dust obscured galaxies. The Wide-field Infrared Survey Explorer (WISE) has provided an all-sky mid-IR survey in four passbands, and the photometry from this catalog can be used to identify AGN candidates. We select AGNs from the catalog using a WISE $W1-W2>0.8$ color cut, and perform follow-up observations with the Keck DEIMOS optical spectrograph for redshift and emission line measurements. We spectroscopically confirm that mid-IR color selection does indeed identify obscured AGNs that are missed by the largest existing optical surveys, and targeted observations are necessary to find these objects. Combining WISE data with the AKARI far-IR all-sky catalog, we also perform SED analysis to characterize the physical properties of dusty AGNs and their surrounding obscuring medium. Using only photometry, we are able to extract a number of physical properties (ex. dust temperature and masses) without the need for time and resource-intensive spectroscopy. Finally, we test the effects of using different SED and color criteria to select different populations of AGNs from the 3D-HST catalog and compute their luminosity functions. We find that SED fitting can identify a large number of AGNs that are missed by traditional color selection methods, and this can potentially increase the sample size of AGNs available for analysis by several factors.
Author: Itziar Aretxaga Publisher: World Scientific ISBN: 981449108X Category : Science Languages : en Pages : 387
Book Description
A group of leading experts in the field of starbursts and active galactic nuclei have joined hands to produce this review volume which covers the starburst-AGN connection, and the tests to be carried out with the upcoming new astronomical facilities to ascertain the relevance of both components to the formation and evolution of galaxies.The book is addressed to advanced graduate students and researchers in the fields of active galactic nuclei and young galaxies.
Author: Alexander John Mendez
Author: Alexander John Mendez
Author: T.J.-L. Courvoisier
Author: Volker Beckmann
Author: Bradley M. Peterson
Author: Thierry Jean-Louis Courvoisier
Author: T.J.-L. Courvoisier
Author: John Edward Dyson
Author: Anson Lam
Author: Itziar Aretxaga
Author: Professor R. D. Blandford