Download or read book Multiwavelength Analysis of Star forming Galaxies and Active Galactic Nuclei in a Complete Redshift Survey written by Pietro M. Reviglio and published by . This book was released on 2003 with total page 206 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Multi wavelength Analysis of Active Galactic Nuclei and Host Galaxies Physical Properties written by Mojegan Azadi and published by . This book was released on 2017 with total page 209 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this dissertation we study the properties of active galactic nuclei (AGN), which are powered by the accretion activity of supermassive black holes residing at the centers of galaxies. While observations propose that growth of AGN and galaxies are globally tied, we investigate whether this connection exists in individual galaxies. We also investigate various AGN selection techniques and star formation rate (SFR) estimates using multi-wavelength data from Chandra, Spitzer and rest-frame optical spectra from the Keck telescope. We find that combining multi-wavelength identification techniques provides a more complete AGN sample, as each selection method suffers from selection biases. In particular, all selection techniques are biased against identifying AGN in lower mass galaxies. Once stellar mass selection biases are taken into account, we find that AGN reside in galaxies with similar physical properties (i.e., SFR) as inactive galaxies. We find that while AGN are prevalent in both star-forming and quiescent galaxies, AGN of a given accretion rate are more likely to reside in star-forming galaxies. The probability of fueling an AGN does not strongly depend on SFR for a star-forming galaxy, though it decreases when star formation is shut down in quiescent galaxies. We also find no evidence for a strong correlation between SFR or stellar mass of the host galaxy and AGN luminosity. These results indicate that while both AGN and galaxy growth are reliant on the same fuel, enhanced star formation activity does not necessarily go hand-in-hand with increased AGN activity. While the star formation activity of galaxies can be traced with various indicators, our investigations indicate that extrapolations from mid-infrared data using calibrations based on local galaxies overestimates SFRs at higher redshift. We show that a combination of mid-infrared and far-infrared data provide a more reliable SFR estimation than the mid-infrared data alone. We also find that the robustness of UV-based SFRs depends on the extinction correction method used. We find a relatively small fraction of z ∼ 2 galaxies have SFRs from infrared observations that are elevated relative to other SFR tracers, and we do not find any contribution from AGN in this excess.
Download or read book Multi wavelength Population Studies of Active Galactic Nuclei and Galaxies Using PRIMUS and AEGIS written by Alexander John Mendez and published by . This book was released on 2014 with total page 187 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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
Download or read book The X ray Background written by Xavier Barcons and published by Cambridge University Press. This book was released on 1992-07-31 with total page 328 pages. Available in PDF, EPUB and Kindle. Book excerpt: A review of the current observational knowledge and understanding of the cosmic X-ray background.
Download or read book Exploring the Interplay Between Star Formation and Active Galactic Nuclei and the Role of Environment in Galaxy Evolution written by Jonathan Florez and published by . This book was released on 2021 with total page 432 pages. Available in PDF, EPUB and Kindle. Book excerpt: One of the central goals of extragalactic astronomy is to understand how galaxies grow their stellar mass and central black holes, the connection between star formation and active galactic nuclei (AGN), and the impact of environment on this growth. In this thesis, I utilize multiwavelength surveys that are both deep and wide, advanced computational codes that model the spectral energy distributions of galaxies with and without AGN, as well as state-of-the-art simulations of galaxy evolution in order to explore how galaxy properties are impacted by their surrounding environment and AGN activity. These studies explore galaxies over a redshift range of 0.015 z 0.023 (lookback time of ~ 0.2 to ~ 0.3 Gyr), and over a redshift range of 0.5 z 3.0 (lookback time of ~ 5 to ~ 12 Gyr). The large-area surveys used here provide some of the largest and most statistically robust samples to-date of rare massive galaxies (with stellar mass M [subscript *] 1011 M☉) and extremely luminous AGN (with X-ray luminosity L [subscript X] 1044 erg s−1) out to z ~ 3, thereby limiting the effects of cosmic variance and Poisson statistics. I analyze the observed stellar masses and star formation rates of galaxies as a function of environment and AGN activity, compare the empirical results to theoretical models of galaxy evolution, and discuss the implications of such comparisons. This work will provide significant guidance and constraints to the future development of theoretical models of galaxy growth. In Chapter 2 (Florez et al. 2021, ApJ, 906, 97) I measure the environmental dependence, where environment is defined by the distance to the third nearest neighbor, of multiple galaxy properties inside the Environmental COntext (ECO) catalog. I focus primarily on void galaxies at redshifts z = 0.015 - 0.023, which I define as the 10% of galaxies having the lowest local density. I compare the properties of void and non-void galaxies: baryonic mass, color, fractional stellar mass growth rate (FSMGR), morphology, and gas-to-stellar-mass ratio. The void galaxies typically have lower baryonic masses than galaxies in denser environments, and they display the properties expected of a lower mass population: they have more late-types, are bluer, have higher FSMGR, and are more gas rich. I also control for baryonic mass and investigate the extent to which void galaxies are different at fixed mass. I find that void galaxies are bluer, more gas-rich, and more star forming at fixed mass than non-void galaxies, which is a possible signature of galaxy assembly bias and other environmental processes. Furthermore, I show that these trends persist even at fixed mass and morphology, and I find that voids host a distinct population of early-types that are bluer and more star-forming than the typical red and quenched early-types. In addition to these empirical observational results, I also present theoretical results from mock catalogs with built-in galaxy assembly bias. I show that a simple matching of galaxy properties to (sub)halo properties, such as mass and age, can recover the observed environmental trends in the local galaxy population. In Chapter 3 (Florez et al. 2020, MNRAS, 497, 3273) I investigate the relation between AGN and star formation activity at 0.5 z 3 by analyzing 898 galaxies with high X-ray luminosity AGN (L [subscript X] 1044 erg s−1) and a large comparison sample of ~ 320,000 galaxies without such AGN. My samples are selected from a large (11.8 deg2) area in Stripe 82 that has multi-wavelength (X-ray to far-IR) data. The enormous comoving volume (~ 0.3 Gpc3) at 0.5
Download or read book A Multi Wavelength Census of Star Formation at Redshift Z 2 written by Naveen Reddy and published by Universal-Publishers. This book was released on 2006 with total page 208 pages. Available in PDF, EPUB and Kindle. Book excerpt: We examine the census of star-forming galaxies and their extinction properties at redshift z 2, when a large fraction of the stellar mass in the universe formed. We find a good agreement between the X-ray, radio, and de-reddened UV estimates of the average star formation rate (SFR) for our sample of z 2 galaxies of 50 Msun/yr, indicating that the locally calibrated SFR relations appear to be statistically valid from redshifts 1.5
Download or read book Radio Galaxies and the Role of Environment written by Lu Shen and published by . This book was released on 2019 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation describes research performed in the field of observational astrophysics as part of the Observations of Redshift Evolution in Large Scale Environment (ORELSE) survey, an ongoing multi-wavelength imaging and spectroscopic campaign investigating galaxyevolution in the environments of large scale structures (LSSs) surrounding 16 known clusters at the redshift range of $0.6 [less than or equal to] z [less than or equal to] 1.3. The aim of this dissertation is to contextualize how environment influences galaxy evolution among radio-emitting galaxies and radio Active Galactic Nucleus (RAGN) in a wide dynamic range of environments over cosmic time. In each of the three main chapters I present a sample of radio galaxies and an analysis of the connection to their environments. In the first part of this dissertation I describe the context of radio galaxies, galaxy environments, and the current state of the ORELSE survey. This initial section will set the framework for the variety of studies presented in this thesis. In the second part of this dissertation I present three studies undertaken to investigate various aspects of radio galaxies and the role of there environments. The first of these studies is an investigation of radio galaxies that are cross-matched to spectroscopically-confirmed galaxies in the large scale structures in the five fields of the ORELSE survey. To appropriately classify radio galaxies and study the properties of them separately, a two stage classification method is designed, where radio galaxies are classified into three sub-classes: active galactic nucleus (AGN), Hybrid, and star-forming galaxy (SFG). AGN tend to be preferentially located in locally dense environments and in the cores of clusters/groups, while SFGs exhibit a strong preference for intermediate-density global environments, with these preferences persisting when comparing to galaxies of similar color and stellar mass. These result has important consequences for galaxy evolutionary scenarios, as these two types of galaxies are thought to be the beginning and the end of galaxy evolution. The second of these studies is an investigation of the quenching effect of radio AGN (RAGN) on their neighboring galaxies. In this study, an elevated fraction of quenched RAGN neighbors was found in the most dense local and cluster environments, compared to those of non-RAGN control samples matched to the RAGN population in colour, stellar mass, and local environment. This result suggests that RAGN residing within clusters might heat the intracluster medium (ICM) affecting both in situ star formation and any inflowing gas that remains in their neighbors. This work has important consequences for understanding AGN feedback out of their host galaxies, which is the subject of much debate among astronomers.The final study in this dissertation is a full investigation of the co-evolution of AGN and star formation in radio galaxies in eight ORELSE fields. This study was first motivated by the Hybrid population analyzed in the first study, whose properties suggested that they have coeval star-formation and AGN activity with high accretion efficiency. Combining radio with mid-infrared and far-infrared data available in the ORELSE survey, the AGN and star formation contributions to the total infrared luminosity are well constrained. I present evidence for AGN quenching of the star formation in a rapid timescale in an orbital motion around the clusters/groups. This result has important consequences for galaxy evolutionary scenarios by connecting the two processes that are difficult to separate observationally and are thought to be related.
Download or read book A Multiwavelength Analysis of Star forming Galaxies at Z 1 5 Both on and Off the Galaxy Main Sequence written by Brittany N. Vanderhoof and published by . This book was released on 2023 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Galaxies at High Redshift written by I. Pérez-Fournon and published by Cambridge University Press. This book was released on 2003-03-20 with total page 302 pages. Available in PDF, EPUB and Kindle. Book excerpt: This volume presents lectures of the XI Canary Islands Winter School of Astrophysics written by experts in the field.
Download or read book Stellar Populations Outflows and Morphologies of High redshift Galaxies written by Katherine Anne Kornei and published by . This book was released on 2012 with total page 232 pages. Available in PDF, EPUB and Kindle. Book excerpt: Understanding the regulation and environment of star formation across cosmic time is critical to tracing the build-up of mass in the Universe and the interplay between the stars and gas that are the constituents of galaxies. Three studies are presented in this thesis, each examining a different aspect of star formation at a specific epoch. The first study presents the results of a photometric and spectroscopic survey of 321 Lyman break galaxies (LBGs) at z = 3 to investigate systematically the relationship between Ly & alpha; emission and stellar populations. Ly & alpha; equivalent widths were calculated from rest-frame UV spectroscopy and optical/near-infrared/Spitzer photometry was used in population synthesis modeling to derive the key properties of age, dust extinction, star formation rate (SFR), and stellar mass. We directly compare the stellar populations of LBGs with and without strong Ly & alpha; emission, where we designate the former group (Ly & alpha; equivalent widths greater than 20 & Aring;) as Ly & alpha;-emitters (LAEs) and the latter group (Ly & alpha; equivalent widths fewer than 20 & Aring;) as non-LAEs. This controlled method of comparing objects from the same UV luminosity distribution represents an improvement over previous studies in which the stellar populations of LBGs and narrowband-selected LAEs were contrasted, where the latter were often intrinsically fainter in broadband filters by an order of magnitude simply due to different selection criteria. Using a variety of statistical tests, we find that Ly & alpha; equivalent width and age, SFR, and dust extinction, respectively, are significantly correlated in the sense that objects with strong Ly & alpha; emission also tend to be older, lower in star formation rate, and less dusty than objects with weak Ly & alpha; emission, or the line in absorption. We accordingly conclude that, within the LBG sample, objects with strong Ly & alpha; emission represent a later stage of galaxy evolution in which supernovae-induced outflows have reduced the dust covering fraction. We also examined the hypothesis that the attenuation of Ly & alpha; photons is lower than that of the continuum, as proposed by some, but found no evidence to support this picture. The second study focuses specifically on galactic-scale outflowing winds in 72 star-forming galaxies at z = 1 in the Extended Groth Strip. Galaxies were selected from the DEEP2 survey and follow-up LRIS spectroscopy was obtained covering SiII, CIV, FeII, MgII, and MgI lines in the rest-frame ultraviolet. Using GALEX, HST, and Spitzer imaging available for the Extended Groth Strip, we examine galaxies on a per-object basis in order to better understand both the prevalence of galactic outflows at z = 1 and the star-forming and structural properties of objects experiencing outflows. Gas velocities, measured from the centroids of FeII interstellar absorption lines, are found to span the interval -217, +155 km s-1. We find that approximately 40% (10%) of the sample exhibits blueshifted FeII lines at the 1 & sigma; (3 & sigma;) level. We also measure maximal outflow velocities using the profiles of the FeII and MgII lines; we find that MgII frequently traces higher velocity gas than FeII. Using quantitative morphological parameters derived from the HST imaging, we find that mergers are not a prerequisite for driving outflows. More face-on galaxies also show stronger winds than highly inclined systems, consistent with the canonical picture of winds emanating perpendicular to galactic disks. In light of clumpy galaxy morphologies, we develop a new physically-motivated technique for estimating areas corresponding to star formation. We use these area measurements in tandem with GALEX-derived star-formation rates to calculate star-formation rate surface densities. At least 70% of the sample exceeds a star-formation rate surface density of 0.1 solar masses yr-1 kpc-2, the threshold necessary for driving an outflow in local starbursts. At the same time, the outflow detection fraction of only 40% in FeII absorption provides further evidence for an outflow geometry that is not spherically symmetric. We see a 3 & sigma; trend between outflow velocity and star-formation rate surface density, but no significant trend between outflow velocity and star-formation rate. Higher resolution data are needed in order to test the scaling relations between outflow velocity and both star-formation rate and star-formation rate surface density predicted by theory. Galactic winds are further explored in the third study of this thesis, where we present a study at z = 1 of the prevalence and kinematics of ultraviolet emission lines from fine-structure FeII* transitions and resonance MgII transitions. Utilizing a multiwavelength dataset of 212 star-forming galaxies, we investigate how the strength and kinematics of FeII* and MgII emission lines vary as a function of galaxy properties. We find that FeII* emission is prevalent in the sample; composite spectra assembled on the basis of a variety of galaxy properties all show FeII* emission, particularly in the stronger 2396 and 2626 & Aring; lines. This prevalence of emission is in contrast to observations of local galaxies; the lack of FeII* emission in the small star-forming regions targeted by spectroscopic observations at z = 0 may imply that FeII* emission arises in more extended galaxy halos. The strength of FeII* emission is most strongly modulated by star-formation rate, dust attenuation, and [OII] equivalent width, such that systems with lower star-formation rates, lower dust levels, and larger [OII] equivalent widths show stronger FeII* emission. MgII emission, while not observed in a spectral stack of all the data in our sample, is seen in 30% of individual objects. We find that objects showing MgII emission have preferentially larger [OII] equivalent widths, bluer U-B colors, and lower stellar masses than the sample as a whole. Active galactic nuclei are not likely responsible for the MgII emission in our sample, since we have excluded active galaxies from our dataset. We also do not observe the NeV emission line at 3425 & Aring; characteristic of active galaxies in our co-added spectra. We find that the kinematics of FeII* emission lines are consistent with the systemic velocity. This result does not necessarily imply that these lines arise from star-forming regions, however, as an optically thin galactic wind could show blueshifted and redshifted FeII* emission lines centered around 0 km s-1. We note that FeII* emission arising from extended gas is consistent with the hypothesis that slit losses are responsible for the lack of FeII* emission in local samples. We propose that dust is primarily responsible for the correlations between FeII* strength and galaxy properties, as objects with lower star-formation rates and larger [OII] equivalent widths also exhibit lower dust attenuations, on average. The strong MgII emission seen in systems with larger [OII] equivalent widths, bluer U-B colors, and lower stellar masses may also be the result of low dust attenuation in these objects. Larger studies composed of high signal-to-noise observations will be critical for testing the hypothesis that dust is the primary modulator of fine-structure and resonance emission.
Download or read book Multiwavelength Analysis of the Active Galactic Nuclei s Feedback on the Evolution of Quasar Host Galaxies written by Aishwarya Girdhar and published by . This book was released on 2023 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Understanding the Connection Between Active Galactic Nuclei and Host Star Formation Through Multi wavelength Population Synthesis Modeling written by Aden R. Draper and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Probing the Physics of Active Galactic Nuclei by Multiwavelength Monitoring written by Bradley M. Peterson and published by . This book was released on 2001 with total page 568 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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)
Download or read book Probing Galaxy Evolution Through Deep Radio Continuum Observations written by Hansung Gim and published by . This book was released on 2018 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: One of the most important questions in modern astrophysics is how galaxies form and evolve. There are numerous processes involved in galaxy evolution, but the stellar mass buildup and supermassive black hole growth are two main drivers in galaxy evolution. Those activities are heavily obscured by dust, so we need another tracer without dust attenuation: low-frequency radio continuum observation. We understand the galaxy evolution through the deep radio continuum observations on the Great Observatories Origins Deep Survey (GOODS)-North, -South, and the COSMOS HI Large Extragalactic Survey (CHILES) fields. Exploiting the multi-wavelength dataset, we define the radio populations such as star-formation (SF) dominated, active galactic nuclei (AGN)-dominated, and passive galaxies by applying new selection criteria. Populations are defined according to the relative contributions of SF and AGN luminosities to the bolometric luminosities of host galaxies and star formation properties. We explore the physical properties of radio populations, interpret their properties in the context of galaxy evolution, and show that our results of radio populations are consistent with the galaxy evolution scenarios. These results are the same for the GOODS and CHILES fields. Our investigation of the radio spectral index and radio-FIR correlation for the GOODS fields show that the radio spectral index is characteristic of each population and the radio-FIR correlation is a robust tracer of star formation activity. The analysis of radio spectral index shows the prominence of steep spectrum sources at faint flux density first as expected in the Euclidean normalized number counts. We also show that the radio spectral index should be calculated by matching the beam sizes of images. The evolution of the radio-FIR correlation in SF-dominated galaxies is not found significantly with our data. On the other hand, the analysis of radio spectral index for the CHILES is not consistent with the result of the GOODS due to the larger difference of beam area. This inconsistency gives important implications for the future works.
Download or read book The Physics and Evolution of Active Galactic Nuclei written by Hagai Netzer and published by Cambridge University Press. This book was released on 2013-09-16 with total page 369 pages. Available in PDF, EPUB and Kindle. Book excerpt: A comprehensive introduction to the theory underpinning our study of active galactic nuclei and the ways we observe them.
Download or read book Galaxy Transformation Under Extreme Conditions written by Brian Clark Lemaux and published by . This book was released on 2011 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation describes research performed in the field of observational astrophysics as part of the Observations of Redshift Evolution in Large Scale Environment (ORELSE) survey. The general motivation of the research presented in this dissertation is to investigate the processes responsible for the evolution of galaxies in a wide range of physical conditions over cosmic time. Throughout this dissertation, galaxy populations will be considered in the very nearby universe (i.e., within one billion light years from Earth), the middle-aged universe (i.e., eight billion years ago), and in the very early universe (i.e., just one billion years after the beginning of the universe). In each chapter I present unique data from observations taken and analyzed specifically for the ORELSE survey. In the first part of this dissertation I describe the context, aims, and current state of the ORELSE survey. The studies presented in this dissertation span a large range of galaxy samples and investigate a variety of different astrophysical phenomena. As all of these studies fall under the context of galaxy evolution, these initial sections will set the framework for the variety of studies presented in this thesis. In the second part of this dissertation I present four studies undertaken to investigate various aspects of galaxy evolution. The first of these studies is an investigation of a large population of very distant galaxies detected in one of the ORELSE fields. The survey in this field represents the deepest survey of a particular kind of very distant galaxy population known as Lyman[alpha] Emitter (LAEs). The number of LAEs found in this survey far exceeded expectations for such galaxies and are shown to be in excess of every other survey of similar galaxies at similar distances. This result has important consequences for galaxy evolution studies, as it suggests that faint LAEs may be much more numerous than previously thought. This work also has important consequences for a process in the early universe known as reionization, which is the subject of much debate amongst astronomers. The second and third of these studies are investigations using near-infrared spectroscopy of X-ray bright and red galaxies that exhibit optical spectra with prominent emission features. These studies are the first systematic investigations of both galaxy populations in the middle-aged universe using near-infrared spectroscopy. In both studies I conclude the dominant mechanism giving rise to optical emission line features are processes associated with the presence of an Active Galactic Nuclei (AGN) rather than normal star formation. This result has important consequences for galaxy evolutionary scenarios, as the two processes are typically difficult to separate observationally and are thought to be related. The final study in this presentation is a full investigation of the processes driving galaxy evolution in one of the ORELSE fields, the Cl1604 supercluster. In this study I present the wealth of astronomical observations available to the ORELSE survey on the member galaxies of this supercluster. Several transitional populations of galaxies are detected in the supercluster environment, and their properties are analyzed in the context of galaxy evolution. Processing of the galaxy population is found to be significant in both the densest environments in the supercluster and the lower-density regions. One of the major conclusions of this work relates to the efficiency of these transformative processes and the global environment in which a galaxy resides. I present evidence for a process termed "dynamical downsizing", in which efficient transforming of galaxies occurs earliest in structures of galaxies that are observed to be relaxed (i.e., virialized) in their dynamics.
Download or read book Observations and Multiwavelength Modelling of Active Galactic Nuclei and Starburst Galaxies written by Amanda Burston and published by . This book was released on 2001 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
