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Author : Brian Robert McNamara
Publisher :
ISBN 13 :
Total Pages : 356 pages
Book Rating : 4.X/5 (2 download)
Download or read book Evidence for Cool Gas and Star Formation in Cluster Cooling Flows written by Brian Robert McNamara and published by . This book was released on 1991 with total page 356 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : Sravani Vaddi
Publisher :
ISBN 13 :
Total Pages : 342 pages
Book Rating : 4.:/5 (958 download)
Download or read book Regulation of Star Formation Amidst Heating and Cooling in Galaxies and Galaxy Clusters written by Sravani Vaddi and published by . This book was released on 2016 with total page 342 pages. Available in PDF, EPUB and Kindle. Book excerpt: "Galaxy clusters are the largest gravitationally bound systems in the Universe and often host the largest galaxies (known as the brightest cluster galaxies (BCG)) at its centers. These BCG’s are embedded in hot 1-10 keV X-ray gas. A subset of galaxy clusters known as cool-core clusters show sharply peaked X-ray emission and high central densities, demonstrating cooling of the surrounding halo gas in timescales much shorter than a Hubble time. These observations led to the development of a simple cooling flow model. In the absence of an external heating process, a cooling flow model predicts that the hot intracluster medium gas in these dense cores would hydrostatically cool, generating cooling flows in the center of the cluster. This cooled gas will eventually collapse to form stars and contribute to the bulk of galaxy mass. The rates of star formation actually observed in the clusters however are far less than predicted by the cooling flow model, suggesting a non-gravitational heating source. Active galactic nuclei (AGN), galaxies hosting a supermassive black hole that ejects outflows via accretion, is currently the leading heating mechanism (referred to as AGN feedback) explaining the observed deficit in the star formation rates. AGN feedback also offers an elegant explanation to the observed black hole and galaxy co- evolution. Much of the evidence for AGN feedback has been obtained from studies focussed on galaxy clusters and luminous massive systems with little evidence that it occurs in more typical systems in the local universe. Our research investigates this less explored area to address the importance of AGN heating in the regulation of star formation in typical early type galaxies in the local universe. We selected a sample of 200+ early type, low redshift galaxies and carried out a multiple wavelength study using archival observed in the UV, IR and radio. Our results suggest that early type galaxies in the current epoch are rarely powerful AGN and AGN feedback is constrained to be low in our sample of low redshift, typical early type galaxies. Although heating from the AGN is powerful enough to suppress the cooling of the hot gas, it does not completely offset gas cooling at all times and substantial cooler gas exists in the cores of some galaxy clusters (cool-core clusters), the gas properties of which are not explained by AGN heating models alone. The second part of our research focuses on unravelling the mystery of the unknown heating source regulating star formation in galaxy clusters. We have obtained deep FUV spectroscopy using the HST cosmic origins spectrograph of two cool-core clusters A2597 and Zw3146. FUV spectral lines provide the much needed diagnostics capable of discriminating between various heating models, which was difficult with the standard optical line diagnostics. We investigate several heating/ionization mechanisms namely stellar photoionization, AGN photoionization, and shock heating. We use pre-run Mappings III photoionization code results to model the ionizing radiation field. In general, we notice that there is no one single model that provides a satisfactory explanation for the ionization state of gas. How- ever, we show that stellar and AGN photoionization alone are not enough to ionize the nebula in A2597 and speculate that, shock heating is the likely ionizing source."--Abstract.
Author : A.C. Fabian
Publisher : Springer Science & Business Media
ISBN 13 : 9400929536
Total Pages : 377 pages
Book Rating : 4.4/5 (9 download)
Download or read book Cooling Flows in Clusters and Galaxies written by A.C. Fabian and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 377 pages. Available in PDF, EPUB and Kindle. Book excerpt: X-ray astronomers discovered the diffuse gas in clusters of galaxies about 20 years ago. It was later realized that the central gas density in some clusters, and in elliptical galaxies, is so high that radiative cooling is a significant energy loss. The cooling time of the gas decreases rapidly towards the centre of the cluster or galaxy and is less than a Hubble time within the innermost few hundred kiloparsecs. This results in a cooling flow in which the gas density rises in order to maintain pressure to support the weight of the overlying gas. The rate at which mass is deposited by the flow is inferred to be several hundreds of solar masses per year in some clusters. The fraction of clusters in which cooling flows are found may exceed 50 per cent. Small flows probably occur in most normal elliptical galaxies that are not in rich clusters. The implications of this simple phenomenon are profound, for we appear to be witnessing the ongoing formation of the central galaxy. In particular, since most of the gas is undetected once it cools below about 3 million K, it appears to form dark matter. There is no reason why it should be detectable with current techniques if each cooling proton only recombines once and the matter condenses into objects of low mass.
Author : A C Fabian
Publisher :
ISBN 13 : 9789400929548
Total Pages : 410 pages
Book Rating : 4.9/5 (295 download)
Download or read book Cooling Flows in Clusters and Galaxies written by A C Fabian and published by . This book was released on 1988-05-31 with total page 410 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : Avery Abraham Meiksin
Publisher :
ISBN 13 :
Total Pages : 406 pages
Book Rating : 4.:/5 (34 download)
Download or read book Cooling Flows in Clusters of Galaxies written by Avery Abraham Meiksin and published by . This book was released on 1988 with total page 406 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : Noam Soker
Publisher :
ISBN 13 :
Total Pages : 256 pages
Book Rating : 4.3/5 (91 download)
Download or read book Galactic and Cluster Cooling Flows written by Noam Soker and published by . This book was released on 1997 with total page 256 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : Grant Russell Tremblay
Publisher :
ISBN 13 :
Total Pages : 440 pages
Book Rating : 4.:/5 (749 download)
Download or read book Feedback Regulated Star Formation in Cool Core Clusters of Galaxies written by Grant Russell Tremblay and published by . This book was released on 2011 with total page 440 pages. Available in PDF, EPUB and Kindle. Book excerpt: "The classical 'cooling flow' model historically associated with 'cool core' clusters of galaxies fails in the absence of an external, non-gravitational heating mechanism needed to offset catastrophic radiative losses of the X-ray bright intracluster medium (ICM). Numerous proposed solutions exist, including feedback from active galactic nuclei (AGN), which may elegantly calibrate fundamental relationships such as the coupled co-evolution of black holes and the stellar component of their host galaxies. AGN feedback cannot completely offset cooling at all times, however, as the brightest cluster galaxies (BCGs) in cool core clusters harbor extensive warm (~104 K) and cold (10
Author : Adrian Vantyghem
Publisher :
ISBN 13 :
Total Pages : 170 pages
Book Rating : 4.:/5 (15 download)
Download or read book Atacama Large Millimeter Submillimeter Array View of Molecular Gas in Brightest Cluster Galaxies written by Adrian Vantyghem and published by . This book was released on 2018 with total page 170 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this thesis I use ALMA observations to map the distribution and kinematics of molecular gas in the brightest cluster galaxies of three galaxy clusters: 2A0335+096, RXJ0821+0752, and RXCJ1504-0248. The goal is to understand how the coldest gas in clusters is formed, identify any long-lived structures that could fuel sustained black hole accretion, and explore star formation in cluster environments. I use the J=1-0 and J=3-2 rotational transitions of carbon monoxide (CO) as tracers of the total molecular gas distribution. The two transitions provide different resolutions and fields of view. The molecular gas in all three central galaxies are complex and disturbed. None show evidence for rotationally-supported nuclear structures, such as a disk or ring, that would be expected from either a merger origin or long-lived cooling flow. Instead, the molecular gas is either clumpy with no clear velocity structure or extends away from the galactic center in filaments that are several kiloparsecs long. The molecular filaments are coincident with nebular and bright X-ray emission, suggesting that they have condensed out of the hot intracluster medium. They are also generally associated with cavities in the X-ray emission inflated by the active galactic nucleus (AGN), suggesting that AGN feedback has stimulated the formation of molecular gas. The narrow velocity gradients along the filaments are only consistent with freefall if the filament is situated close to the plane of the sky. This is a common feature in brightest cluster galaxies. Since ram pressure is ineffective at slowing dense molecular clouds, the filaments must either be pinned to the hot atmosphere by magnetic fields or have condensed in-situ relatively recently. In RXCJ1504-0248 I combine the ALMA analysis with spatially-resolved ultraviolet emission tracing young stars. The central gas falls on the Kennicutt-Schmidt relation, while the filament has elevated star formation surface densities. The ongoing consumption of a finite fuel supply by star formation, or spatial variations in the CO-to-H2 conversion factor, may be diminishing the molecular gas surface density to produce this effect. Despite their drastic differences in morphology and environment, the molecular gas in clusters is still converted into stars following the same relation as in spirals and starbursts. I have also detected the J=3-2 transition from 13CO, an optically thin isotopologue of 12CO, in RXJ0821.0+0752. This enables a measurement of the conversion between CO intensity and molecular column density for the first time in a galaxy cluster. The CO-to-H2 conversion factor in RXJ0821+0752 is half of the Galactic value. If this value applies to other clusters, then it would alleviate the high coupling efficiencies required for molecular filaments to be uplifted by X-ray cavities. This analysis also provides reassurance that the molecular gas masses measured in BCGs are unlikely to be overwhelmingly biased by adopting the Galactic conversion factor.
Author : Gregory Alain Ashe
Publisher :
ISBN 13 :
Total Pages : 74 pages
Book Rating : 4.X/5 (2 download)
Download or read book Steady state cooling flow models with star formation for normal galaxies written by Gregory Alain Ashe and published by . This book was released on 1988 with total page 74 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author :
Publisher :
ISBN 13 :
Total Pages : 464 pages
Book Rating : 4.:/5 (3 download)
Download or read book Scientific and Technical Aerospace Reports written by and published by . This book was released on 1995 with total page 464 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author :
Publisher :
ISBN 13 :
Total Pages : 280 pages
Book Rating : 4.:/5 (319 download)
Download or read book NASA Technical Memorandum written by and published by . This book was released on 1963 with total page 280 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : Hans Böhringer
Publisher : Springer Science & Business Media
ISBN 13 : 3540734848
Total Pages : 453 pages
Book Rating : 4.5/5 (47 download)
Download or read book Heating versus Cooling in Galaxies and Clusters of Galaxies written by Hans Böhringer and published by Springer Science & Business Media. This book was released on 2007-09-27 with total page 453 pages. Available in PDF, EPUB and Kindle. Book excerpt: This volume documents recent developments that have advanced our understanding of the heating and cooling mechanisms in galaxies and galaxy clusters. Chapters detail results from multi-wavelength observations and advances in numerical hydrodynamical simulations. An additional section covers new research findings on feedback and self-regulatory mechanisms during cosmic structure formation in general and in galaxy formation in particular.
Author : A.C. Fabian
Publisher : Springer
ISBN 13 : 9789027727077
Total Pages : 406 pages
Book Rating : 4.7/5 (27 download)
Download or read book Cooling Flows in Clusters and Galaxies written by A.C. Fabian and published by Springer. This book was released on 1988-05-31 with total page 406 pages. Available in PDF, EPUB and Kindle. Book excerpt: X-ray astronomers discovered the diffuse gas in clusters of galaxies about 20 years ago. It was later realized that the central gas density in some clusters, and in elliptical galaxies, is so high that radiative cooling is a significant energy loss. The cooling time of the gas decreases rapidly towards the centre of the cluster or galaxy and is less than a Hubble time within the innermost few hundred kiloparsecs. This results in a cooling flow in which the gas density rises in order to maintain pressure to support the weight of the overlying gas. The rate at which mass is deposited by the flow is inferred to be several hundreds of solar masses per year in some clusters. The fraction of clusters in which cooling flows are found may exceed 50 per cent. Small flows probably occur in most normal elliptical galaxies that are not in rich clusters. The implications of this simple phenomenon are profound, for we appear to be witnessing the ongoing formation of the central galaxy. In particular, since most of the gas is undetected once it cools below about 3 million K, it appears to form dark matter. There is no reason why it should be detectable with current techniques if each cooling proton only recombines once and the matter condenses into objects of low mass.
Author : Peter Schneider
Publisher : Springer
ISBN 13 : 364254083X
Total Pages : 637 pages
Book Rating : 4.6/5 (425 download)
Download or read book Extragalactic Astronomy and Cosmology written by Peter Schneider and published by Springer. This book was released on 2014-10-08 with total page 637 pages. Available in PDF, EPUB and Kindle. Book excerpt: This second edition has been updated and substantially expanded. Starting with the description of our home galaxy, the Milky Way, this cogently written textbook introduces the reader to the astronomy of galaxies, their structure, active galactic nuclei, evolution and large scale distribution in the Universe. After an extensive and thorough introduction to modern observational and theoretical cosmology, the focus turns to the formation of structures and astronomical objects in the early Universe. The basics of classical astronomy and stellar astrophysics needed for extragalactic astronomy are provided in the appendix. While this book has grown out of introductory university courses on astronomy and astrophysics and includes a set of problems and solutions, it will not only benefit undergraduate students and lecturers; thanks to the comprehensive coverage of the field, even graduate students and researchers specializing in related fields will appreciate it as a valuable reference work.
Author : Andre Balogh
Publisher : Springer
ISBN 13 : 149393547X
Total Pages : 357 pages
Book Rating : 4.4/5 (939 download)
Download or read book Multi-scale Structure Formation and Dynamics in Cosmic Plasmas written by Andre Balogh and published by Springer. This book was released on 2016-02-02 with total page 357 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book offers eleven coordinated reviews on multi-scale structure formation in cosmic plasmas in the Universe. Observations and theories of plasma structures are presented in all relevant astrophysical contexts, from the Earth’s magnetosphere through heliospheric and galactic scales to clusters of galaxies and the large scale structure of the Universe. Basic processes in cosmic plasmas starting from electric currents and the helicity concept governing the dynamics of magnetic structures in planet magnetospheres, stellar winds, and relativistic plasma outflows like pulsar wind nebulae and Active Galactic Nuclei jets are covered. The multi-wavelength view from the radio to gamma-rays with modern high resolution telescopes discussed in the book reveals a beautiful and highly informative picture of both coherent and chaotic plasma structures tightly connected by strong mutual influence. The authors are all leading scientists in their fields, making this book an authoritative, up‐to‐date and enduring contribution to astrophysics.
Author : Roman Schrittwieser
Publisher : World Scientific
ISBN 13 : 981455295X
Total Pages : 318 pages
Book Rating : 4.8/5 (145 download)
Download or read book Current Research On Fusion, Laboratory, And Astrophysical Plasmas - Proceedings Of The 1991 International Workshop On Plasma Physics written by Roman Schrittwieser and published by World Scientific. This book was released on 1993-08-12 with total page 318 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book covers recent advances in the physics of nucleon resonances, including new experimental results from laboratories in the USA, Europe, and Asia, and new developments in effective field theories, quark models, and lattice gauge theory.
Author : D. Lynden-Bell
Publisher : Springer Science & Business Media
ISBN 13 : 9400905653
Total Pages : 301 pages
Book Rating : 4.4/5 (9 download)
Download or read book Baryonic Dark Matter written by D. Lynden-Bell and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 301 pages. Available in PDF, EPUB and Kindle. Book excerpt: The visible universe is a small perturbation on the material universe. Zwicky and Sinclair Smith in the 1930s gave evidence of invisible mass in the Coma and Virgo Clusters of Galaxies. Better optical data has only served to confound their critics and the X-ray data confirms that the gravitational potentials are many times larger than those predicted on the basis of the observed stars. Dynamical analyses of individual galaxies have found that significant extra mass is needed to explain their rotational velocities. On much larger scales, tens of megaparsecs, there is suggestive evidence that there is even more mass per unit luminosity. What is this non-luminous stuff of which the universe is made'? How much of it is there? Need there be only one kind of stuff? There are three basic possi bili ties:- all of it is ordinary (baryonic) matter, all of it is some other kind of (non-baryonic) matter, or some of it is baryonic and some is non-baryonic.
