DOCSLIB.ORG

Exploring the Effect of Active Galactic Nuclei on Quenching, Morphological Transformation and Gas Flows with Simulations of Galaxy Evolution

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text

Load more

EXPLORING THE EFFECT OF ACTIVE GALACTIC NUCLEI ON QUENCHING, MORPHOLOGICAL TRANSFORMATION AND GAS FLOWS WITH SIMULATIONS OF GALAXY EVOLUTION By RYAN BRENNAN A dissertation submitted to the Graduate School—New Brunswick Rutgers, The State University of New Jersey in partial fulfillment of the requirements for the degree of Doctor of Philosophy Graduate Program in Physics and Astronomy written under the direction of Dr. Rachel Somerville and approved by New Brunswick, New Jersey October, 2017 ABSTRACT OF THE DISSERTATION Exploring the Effect of Active Galactic Nuclei on Quenching, Morphological Transformation and Gas Flows with Simulations of Galaxy Evolution By RYAN BRENNAN Dissertation Director: Dr. Rachel Somerville We study the evolution of simulated galaxies in the presence of feedback from active galactic nuclei (AGN). First, we present a study conducted with a semi-analytic model (SAM) of galaxy formation and evolution that includes prescriptions for bulge growth and AGN feedback due to galaxy mergers and disk instabilities. We find that with this physics included, our model is able to qualitatively reproduce a population of galaxies with the correct star-formation and morpho- logical properties when compared with populations of observed galaxies out to z ∼ 3. We also examine the characteristic histories of galaxies with different star-formation and morphological properties in our model in order to draw conclusions about the histories of observed galaxies. Next, we examine the structural properties of galaxies (morphology, size, surface density) as a ii function of distance from the “star-forming main sequence” (SFMS), the observed correlation between the star formation rates (SFRs) and stellar masses of star-forming galaxies. We find that, for observed galaxies, as we move from galaxies above the SFMS (higher SFRs) to those below it (lower SFRs), there exists a nearly monotonic trend towards more bulge-dominated morphology, smaller radius, lower SFR density, and higher stellar density. We find qualitatively similar results for our model galaxies, again driven by our prescriptions for bulge growth and AGN feedback. Next, we conduct a study of the effect of AGN feedback on the gas in individual galaxies using a suite of cosmological hydrodynamical simulations. We compare two sets of 24 galaxies 12 13.4 with halo masses of 10 - 10 M run with two different feedback models: one which includes stellar feedback via UV heating, stellar winds and supernovae, AGN feedback via momentum- driven winds and X-ray heating, and metal heating via photoelectric heating and cosmic X-ray background heating from accreting black holes in background galaxies (MrAGN), and another model which is identical except that it does not include any AGN feedback (NoAGN). We find that our AGN feedback prescription acts both “ejectively,” removing gas from galaxies in powerful outflows, and “preventatively”, suppressing the inflow of gas onto the galaxy. The histories of MrAGN galaxies are gas ejection-dominated, while the histories of NoAGN galaxies are gas recycling-dominated. This difference in gas cycles results in the quenching of star formation in MrAGN galaxies, while their NoAGN counterparts continue to form stars until z=0. Finally, we examine how this change in the baryon cycle affects the metal content of MrAGN galaxies relative to NoAGN galaxies and find that a combination of gas removal from and metal injection into the hot gas halo results in higher average halo metallicities in MrAGN galaxies. iii Acknowledgments First, I would like to thank my advisor, Rachel Somerville, for all of her support and guidance over the last six years. I would also like to thank my thesis committee (Alyson Brooks, Tad Pryor, Wim Kloet, and Thorsten Naab) for their insightful questions and suggestions. I would like to thank the Rutgers astronomy group: faculty, postdocs and graduate students past and present who have created a great atmosphere in which to work, even when things were difficult. Joel: Thanks for all of the office conversations and Babylon 5. Ena: Thanks for all of your help and never getting annoyed at how many emails I sent you. Sheehan, Jon, Carl, Jesse, Anna and especially Catie: thanks for everything. It was pretty fun most of the time. Thank you to my family, Patrick, Tracy and Daniel, for supporting me even when they weren’t exactly sure what it was I was doing. Portions of this work have appeared or will appear in publication elsewhere. Chapter 3 has been published as Brennan et al. (2015) and Chapter 4 has been published as Brennan et al. (2017). Chapter 5 has been submitted to MNRAS and Chapter 6 will soon be submitted. I would like to thank the CANDELS team for all of their advice and comments on Chapters 3 and 4, and I would like to thank all of my collaborators and co-authors (Viraj Pandya, Guillermo Barro, Ned Taylor, Stijn Wuyts, Eric Bell, Avishai Dekel, Harry Ferguson, Dan McIntosh, Casey Papovich, Joel Primack, Asa Bluck, Sandy Faber, Anton Koekemoer, Peter Kurczynski, Jeffrey Newman, Michaela Hirschmann, Thorsten Naab and Jerry Ostriker). These works have been supported by HST Theory grant HST-AR-13270-A and the Downs- brough Fund, as well as by the Simons Foundation through a Simons Investigator grant to rss. iv Support for HST Programs GO-12060 and GO-12099 was provided by NASA through grants from the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555. v Dedication For Zorp the Surveyor vi Table of Contents Abstract ............................................. ii Acknowledgments ....................................... iv Dedication ............................................ vi List of Tables .......................................... x List of Figures ......................................... xi 1. Introduction ........................................ 1 1.1. Galaxy Formation . 1 1.2. Star Formation, Chemical Enrichment, and Morphology . 2 1.3. AGN Feedback . 7 1.4. Semi-analytic Models . 12 1.5. Hydrodynamical Simulations . 13 1.6. The Contents of This Thesis . 13 2. Simulations and Observational Data ......................... 17 2.1. Simulations . 17 2.2. Observational Data . 31 vii 3. Quenching and Morphological Transformation in CANDELS and a Semi- analytic Model ......................................... 34 3.1. Introduction . 34 3.2. Results . 40 3.3. Discussion . 56 3.4. Summary and Conclusions . 75 4. The Relationship Between Star-Formation Activity and Galaxy Structural Properties ............................................ 78 4.1. Introduction . 78 4.2. Evolution of Star-forming and Quiescent Galaxies in the SAM . 83 4.3. Distribution of Properties in the Star formation Rate-Stellar Mass Plane . 86 4.4. Distance from the Main Sequence . 97 4.5. Distribution of Distance as a Function of Galaxy Properties . 100 4.6. Discussion . 108 4.7. Summary and Conclusions . 118 5. Momentum-driven Winds from Radiatively Efficient Black Hole Accretion and Their Impact on Galaxies .................................. 121 5.1. Introduction . 121 5.2. Methods . 127 5.3. Results . 128 5.4. Discussion . 157 5.5. Summary . 165 6. The Effect of Mechanical AGN Feedback on Chemical Enrichment ...... 169 viii 6.1. Introduction . 169 6.2. Results . 170 6.3. Discussion . 191 6.4. Conclusions . 192 7. Conclusions ......................................... 194 Appendix A. Conversion from B/T to Sérsic Index in Chapter 3 ......... 198 Appendix B. Results of Chapter 3 Using B/T ..................... 202 Bibliography .......................................... 207 ix List of Tables 3.1. Coefficients for main sequence fit . 43 3.2. Slopes for star formation cut . 43 5.1. Final properties of three example galaxies . 130 x List of Figures 1.1. Local galaxy color bimodality . 4 1.2. Morphology in the SFR-M∗ plane. 7 1.3. The M-σ relation. 10 3.1. sSFR-M∗ distribution of galaxies. 45 3.2. Quiescent fraction of galaxies . 46 3.3. Quiescent fraction divided by mass . 48 3.4. Spheroid-dominated fraction of galaxies . 49 3.5. Spheroid-dominated fraction divided by mass . 50 3.6. Division of galaxies in the sSFR-n plane . 53 3.7. Sérsic index distribution . 54 3.8. sSFR distribution . 54 3.9. Fraction of galaxies in each sSFR-n subpopulation . 57 3.10. Subpopulation fraction with n = 2 cut . 58 3.11. Schematic overview of physical processes . 59 3.12. Fraction of galaxies that have been disturbed . 63 3.13. Evolution of simulated SFD galaxy . 64 3.14. Evolution of simulated QS galaxy . 66 3.15. Evolution of simulated SFS galaxy . 68 3.16. Evolution of simulated QD galaxy . 71 xi 4.1. Evolution of SFR for simulated present day star-forming and quiescent galaxies . 85 4.2. Distribution of galaxies in SFR-M∗ plane . 87 4.3. Distribution of median Sérsic index in SFR-M∗ plane . 90 4.4. Distribution of median Sérsic index in SFR-M∗ plane for noDI model . 91 4.5. Distribution of median effective radius in SFR-M∗ plane . 93 4.6. Distribution of median SFR density in SFR-M∗ plane . 94 4.7. Distribution of median stellar mass density in SFR-M∗ plane . 95 4.8. Distribution of various model properties in SFR-M∗ plane . 96 4.9. Median Sérsic index as a function of distance from the main sequence . 98 4.10. Median effective radius as a function of distance from the main sequence . 99 4.11. Median SFR density as a function of distance from the main sequence . 100 4.12. Median stellar mass density as a function of distance from the main sequence . 101 4.13. Distribution of SFR in galaxy property bins in SAM and Sloan . 103 4.14. Distribution of SFR in galaxy property bins in SAM . 104 4.15. Distribution of SFR in galaxy property bins at low redshift . 106 4.16. Distribution of SFR in galaxy property bins in middle redshift slice . 107 4.17. Distribution of SFR in galaxy property bins at high redshift . 109 5.1. History of galaxy m0163 . 131 5.2. History of galaxy m0329 . 133 5.3.
Recommended publications
  • Astrotalk: Behind the News Headlines

    Astrotalk: Behind the News Headlines

    AstroTalk: Behind the news headlines Richard de Grijs (何锐思) (Macquarie University, Sydney, Australia) The Gaia ‘Sausage’ galaxy Our Milky Way galaxy has most likely collided or otherwise interacted with numerous other galaxies during its lifetime. Indeed, such interactions are common cosmic occurrences. Astronomers can deduce the history of mass accretion onto the Milky Way from a study of debris in the halo of the galaxy left as the tidal residue of such episodes. That approach has worked particularly well for studies of the most recent merger events, like the infall of the Sagittarius dwarf galaxy into the Milky Way’s centre a few billion years ago, which left tidal streamers of stars visiBle in galaxy maps. The damaging effects these encounters can cause to the Milky Way have, however, not been as well studied, and events even further in the past are even less obvious as they Become Blurred By the galaxy’s natural motions and evolution. Some episodes in the Milky Way’s history, however, were so cataclysmic that they are difficult to hide. Scientists have known for some time that the Milky Way’s halo of stars drastically changes in character with distance from the galactic centre, as revealed by the chemical composition—the ‘metallicity’—of the stars, the stellar motions, and the stellar density. Harvard astronomer Federico Marinacci and his colleagues recently analysed a suite of cosmological computer simulations and the galaxy interactions in them. In particular they analysed the history of galaxy halos as they evolved following a merger event. They concluded that six to ten Billion years ago the Milky Way merged in a head- on collision with a dwarf galaxy containing stars amounting to about one-to-ten billion solar masses, and that this collision could produce the character changes in stellar populations currently observed in the Milky Way’s stellar halo.
  • The Evolution of Galaxy Structure Over Cosmic Time

    The Evolution of Galaxy Structure Over Cosmic Time

    Annu. Rev. Astron. Astrophy. 2014 1056-8700/97/0610-00 The Evolution of Galaxy Structure over Cosmic Time Christopher J. Conselice Centre for Astronomy and Particle Theory School of Physics and Astronomy University of Nottingham, United Kingdom Key Words galaxy evolution, galaxy morphology, galaxy structure Abstract I present a comprehensive review of the evolution of galaxy structure in the universe from the first galaxies we can currently observe at z ∼ 6 down to galaxies we see in the local universe. I further address how these changes reveal galaxy formation processes that only galaxy structural analyses can provide. This review is pedagogical and begins with a de- tailed discussion of the major methods in which galaxies are studied morphologically and structurally. This includes the well-established visual method for morphology; S´ersic fitting to measure galaxy sizes and surface brightness profile shapes; non-parametric structural methods including the concentration (C), asymmetry (A), clumpiness (S) (CAS) method, the Gini/M20 parameters, as well as newer structural indices. Included is a discussion of how these structural indices measure fundamental properties of galaxies such as their scale, star formation rate, and ongoing merger activity. Extensive observational results are shown demonstrating how broad galaxy morphologies and structures change with time up to z ∼ 3, from small, compact and peculiar systems in the distant universe to the formation of the Hubble sequence dominated by spirals and ellipticals we find today. This review further addresses how structural methods accurately identify galaxies in mergers, and allow mea- arXiv:1403.2783v1 [astro-ph.GA] 12 Mar 2014 surements of the merger history out to z ∼ 3.
  • Unequal-Mass Galaxy Merger Remnants: Spiral-Like Morphology but Elliptical-Like Kinematics

    Unequal-Mass Galaxy Merger Remnants: Spiral-Like Morphology but Elliptical-Like Kinematics

    A&A 418, L27–L30 (2004) Astronomy DOI: 10.1051/0004-6361:20040114 & c ESO 2004 Astrophysics Unequal-mass galaxy merger remnants: Spiral-like morphology but elliptical-like kinematics F. Bournaud1,2,F.Combes1, and C. J. Jog3 1 Observatoire de Paris, LERMA, 61 Av. de l’Observatoire, 75014 Paris, France Letter to the Editor 2 Ecole´ Normale Sup´erieure, 45 rue d’Ulm, 75005 Paris, France 3 Department of Physics, Indian Institute of Science, Bangalore 560012, India Received 14 January 2004 / Accepted 12 March 2004 Abstract. It is generally believed that major galaxy mergers with mass ratios in the range 1:1–3:1 result in remnants that have properties similar to elliptical galaxies, and minor mergers below 10:1 result in disturbed spiral galaxies. The intermediate range of mass ratios 4:1–10:1 has not been studied so far. Using N-body simulations, we show that such mergers can result in very peculiar systems, that have the morphology of a disk galaxy with an exponential profile, but whose kinematics is closer to that of elliptical systems. These objects are similar to those recently observed by Jog & Chitre (2002). We present two cases with mass ratios 4.5:1 and 7:1, and show that the merging causes major heating and results in the appearance of elliptical-type kinematics, while surprisingly the initial spiral-like mass profile is conserved. Key words. galaxies: interaction – galaxies: formation – galaxies: evolution – galaxies: kinematics 1. Introduction regarded as elliptical galaxies with faint outer disks. Among the class II objects, Jog & Chitre (2002) have pointed out sys- Numerical simulations commonly show that the merging of tems with kinematical properties typical of elliptical galaxies: two equal-mass spiral galaxies results in the formation of an they have velocity dispersions as large or larger than rotation r1/4 elliptical galaxy with an radial profile consistent with ob- velocity, while spiral disks are usually supported by rotation.
  • Using Transfer Learning to Detect Galaxy Mergers

    Using Transfer Learning to Detect Galaxy Mergers

    MNRAS 000,1{12 (2017) Preprint 30 May 2018 Compiled using MNRAS LATEX style file v3.0 Using transfer learning to detect galaxy mergers Sandro Ackermann,1 Kevin Schawinski,1 Ce Zhang,2 Anna K. Weigel1 and M. Dennis Turp1 1Institute for Particle Physics and Astrophysics, Department of Physics, ETH Zurich, Wolfgang-Pauli-Strasse 27, CH-8093, Zurich,¨ Switzerland 2Systems Group, Department of Computer Science, ETH Zurich, Universit¨atstrasse 6, CH-8006, Zurich,¨ Switzerland Accepted XXX. Received YYY; in original form ZZZ ABSTRACT We investigate the use of deep convolutional neural networks (deep CNNs) for auto- matic visual detection of galaxy mergers. Moreover, we investigate the use of transfer learning in conjunction with CNNs, by retraining networks first trained on pictures of everyday objects. We test the hypothesis that transfer learning is useful for im- proving classification performance for small training sets. This would make transfer learning useful for finding rare objects in astronomical imaging datasets. We find that these deep learning methods perform significantly better than current state-of-the-art merger detection methods based on nonparametric systems like CAS and GM20. Our method is end-to-end and robust to image noise and distortions; it can be applied directly without image preprocessing. We also find that transfer learning can act as a regulariser in some cases, leading to better overall classification accuracy (p = 0:02). Transfer learning on our full training set leads to a lowered error rate from 0.038±1 down to 0.032±1, a relative improvement of 15%. Finally, we perform a basic sanity- check by creating a merger sample with our method, and comparing with an already existing, manually created merger catalogue in terms of colour-mass distribution and stellar mass function.
  • Fast Outflows and Star Formation Quenching in Quasar Host Galaxies

    Fast Outflows and Star Formation Quenching in Quasar Host Galaxies

    A&A 591, A28 (2016) Astronomy DOI: 10.1051/0004-6361/201528037 & c ESO 2016 Astrophysics Fast outflows and star formation quenching in quasar host galaxies?,?? S. Carniani1; 2; 3; 4, A. Marconi1; 2, R. Maiolino3; 4, B. Balmaverde1, M. Brusa5; 6, M. Cano-Díaz7, C. Cicone8, A. Comastri6, G. Cresci2, F. Fiore9, C. Feruglio9; 10; 11, F. La Franca12, V. Mainieri13, F. Mannucci2, T. Nagao14, H. Netzer15, E. Piconcelli9, G. Risaliti2, R. Schneider9, and O. Shemmer16 1 Dipartimento di Fisica e Astronomia, Università di Firenze, via G. Sansone 1, 50019 Sesto Fiorentino (Firenze), Italy 2 INAF–Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, 50125 Firenze, Italy 3 Cavendish Laboratory, University of Cambridge, 19 J. J. Thomson Ave., Cambridge CB3 0HE, UK 4 Kavli Institute for Cosmology, University of Cambridge, Madingley Road, Cambridge CB3 0HA, UK 5 Dipartimento di Fisica e Astronomia, Università di Bologna, viale Berti Pichat 6/2, 40127 Bologna, Italy 6 INAF–Osservatorio Astronomico di Bologna, via Ranzani 1, 40127 Bologna, Italy 7 Instituto de Astronomía, Universidad Nacional Autónoma de México, Apartado Postal 70-264, 04510 Mexico D.F., Mexico 8 Institute for Astronomy, Department of Physics, ETH Zurich, Wolfgang-Pauli-Strasse 27, 8093 Zurich, Switzerland 9 INAF–Osservatorio Astronomico di Roma, via Frascati 33, 00040 Monteporzio Catone, Italy 10 Scuola Normale Superiore, Piazza dei Cavalieri 7, 56126 Pisa, Italy 11 IRAM–Institut de RadioAstronomie Millimétrique, 300 rue de la Piscine, 38406 Saint-Martin d’Hères, France 12 Dipartimento di Matematica e Fisica, Universitá Roma Tre, via della Vasca Navale 84, 00146 Roma, Italy 13 European Southern Observatory, Karl-Schwarzschild-str.
  • Neutral Hydrogen in Local Group Dwarf Galaxies

    Neutral Hydrogen in Local Group Dwarf Galaxies

    Neutral Hydrogen in Local Group Dwarf Galaxies Jana Grcevich Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy in the Graduate School of Arts and Sciences COLUMBIA UNIVERSITY 2013 c 2013 Jana Grcevich All rights reserved ABSTRACT Neutral Hydrogen in Local Group Dwarfs Jana Grcevich The gas content of the faintest and lowest mass dwarf galaxies provide means to study the evolution of these unique objects. The evolutionary histories of low mass dwarf galaxies are interesting in their own right, but may also provide insight into fundamental cosmological problems. These include the nature of dark matter, the disagreement be- tween the number of observed Local Group dwarf galaxies and that predicted by ΛCDM, and the discrepancy between the observed census of baryonic matter in the Milky Way’s environment and theoretical predictions. This thesis explores these questions by studying the neutral hydrogen (HI) component of dwarf galaxies. First, limits on the HI mass of the ultra-faint dwarfs are presented, and the HI content of all Local Group dwarf galaxies is examined from an environmental standpoint. We find that those Local Group dwarfs within 270 kpc of a massive host galaxy are deficient in HI as compared to those at larger galactocentric distances. Ram- 4 3 pressure arguments are invoked, which suggest halo densities greater than 2-3 10− cm− × out to distances of at least 70 kpc, values which are consistent with theoretical models and suggest the halo may harbor a large fraction of the host galaxy’s baryons. We also find that accounting for the incompleteness of the dwarf galaxy count, known dwarf galaxies whose gas has been removed could have provided at most 2.1 108 M of HI gas to the Milky Way.
  • Stellar Streams Discovered in the Dark Energy Survey

    Stellar Streams Discovered in the Dark Energy Survey

    Draft version January 9, 2018 Typeset using LATEX twocolumn style in AASTeX61 STELLAR STREAMS DISCOVERED IN THE DARK ENERGY SURVEY N. Shipp,1, 2 A. Drlica-Wagner,3 E. Balbinot,4 P. Ferguson,5 D. Erkal,4, 6 T. S. Li,3 K. Bechtol,7 V. Belokurov,6 B. Buncher,3 D. Carollo,8, 9 M. Carrasco Kind,10, 11 K. Kuehn,12 J. L. Marshall,5 A. B. Pace,5 E. S. Rykoff,13, 14 I. Sevilla-Noarbe,15 E. Sheldon,16 L. Strigari,5 A. K. Vivas,17 B. Yanny,3 A. Zenteno,17 T. M. C. Abbott,17 F. B. Abdalla,18, 19 S. Allam,3 S. Avila,20, 21 E. Bertin,22, 23 D. Brooks,18 D. L. Burke,13, 14 J. Carretero,24 F. J. Castander,25, 26 R. Cawthon,1 M. Crocce,25, 26 C. E. Cunha,13 C. B. D'Andrea,27 L. N. da Costa,28, 29 C. Davis,13 J. De Vicente,15 S. Desai,30 H. T. Diehl,3 P. Doel,18 A. E. Evrard,31, 32 B. Flaugher,3 P. Fosalba,25, 26 J. Frieman,3, 1 J. Garc´ıa-Bellido,21 E. Gaztanaga,25, 26 D. W. Gerdes,31, 32 D. Gruen,13, 14 R. A. Gruendl,10, 11 J. Gschwend,28, 29 G. Gutierrez,3 B. Hoyle,33, 34 D. J. James,35 M. D. Johnson,11 E. Krause,36, 37 N. Kuropatkin,3 O. Lahav,18 H. Lin,3 M. A. G. Maia,28, 29 M. March,27 P. Martini,38, 39 F. Menanteau,10, 11 C.
  • Tidal Dwarf Galaxies and Missing Baryons

    Tidal Dwarf Galaxies and Missing Baryons

    Tidal Dwarf Galaxies and missing baryons Frederic Bournaud CEA Saclay, DSM/IRFU/SAP, F-91191 Gif-Sur-Yvette Cedex, France Abstract Tidal dwarf galaxies form during the interaction, collision or merger of massive spiral galaxies. They can resemble “normal” dwarf galaxies in terms of mass, size, and become dwarf satellites orbiting around their massive progenitor. They nevertheless keep some signatures from their origin, making them interesting targets for cosmological studies. In particular, they should be free from dark matter from a spheroidal halo. Flat rotation curves and high dynamical masses may then indicate the presence of an unseen component, and constrain the properties of the “missing baryons”, known to exist but not directly observed. The number of dwarf galaxies in the Universe is another cosmological problem for which it is important to ascertain if tidal dwarf galaxies formed frequently at high redshift, when the merger rate was high, and many of them survived until today. In this article, I use “dark matter” to refer to the non-baryonic matter, mostly located in large dark halos – i.e., CDM in the standard paradigm. I use “missing baryons” or “dark baryons” to refer to the baryons known to exist but hardly observed at redshift zero, and are a baryonic dark component that is additional to “dark matter”. 1. Introduction: the formation of Tidal Dwarf Galaxies A Tidal Dwarf Galaxy (TDG) is, per definition, a massive, gravitationally bound object of gas and stars, formed during a merger or distant tidal interaction between massive spiral galaxies, and is as massive as a dwarf galaxy [1] (Figure 1).
  • Evolution of Magnetic Fields in Galaxies and Future Observational

    Evolution of Magnetic Fields in Galaxies and Future Observational

    A&A 494, 21–32 (2009) Astronomy DOI: 10.1051/0004-6361:200810964 & c ESO 2009 Astrophysics Evolution of magnetic fields in galaxies and future observational tests with the Square Kilometre Array T. G. Arshakian1,R.Beck1, Marita Krause1,andD.Sokoloff2 1 Max-Planck-Institut für Radioastronomie, Bonn, Germany e-mail: [tarshakian;rbeck;mkrause]@mpifr-bonn.mpg.de 2 Department of Physics, Moscow State University, Russia e-mail: [email protected] Received 14 September 2008 / Accepted 16 October 2008 ABSTRACT Aims. In the context of models of galaxy formation and evolution, we investigate the cosmological evolution of large- and small-scale magnetic fields inside galaxies. Methods. We use the dynamo theory to derive the timescales of amplification and ordering of magnetic fields in disk and puffy galaxies. Turbulence in protogalactic halos generated by thermal virialization can drive an efficient turbulent dynamo. Results from simulations of hierarchical structure formation cosmology provide a tool to develop an evolutionary model of regular magnetic fields coupled with galaxy formation and evolution. Results. The turbulent (small-scale) dynamo was able to amplify a weak seed magnetic field in halos of protogalaxies to a few μG strength within a few 108 yr. This turbulent field served as a seed to the mean-field (large-scale) dynamo. Galaxies similar to the Milky Way formed their disks at z ≈ 10 and regular fields of μG strength and a few kpc coherence length were generated within 2 Gyr (at z ≈ 3), but field-ordering on the coherence scale of the galaxy size required an additional 6 Gyr (at z ≈ 0.5).
  • Galactic Star Formation and Supermassive Black Hole Masses 2 June 2020

    Galactic Star Formation and Supermassive Black Hole Masses 2 June 2020

    Galactic star formation and supermassive black hole masses 2 June 2020 be responsible (or at least an important contributor) as could strong stellar winds. Verifying these various alternatives is hence a key goal of galactic research. CfA astronomers Bryan Terrazas, Rainer Weinberger and Lars Hernquist and their colleagues used the large-scale hydrodynamic simulation called IllustrisTNG to trace the development of galaxies and their black holes, in particular to investigate the correlations between black hole feedback and the suppression of star formation. Although the details of black hole accretion are still only sketchily understood, the simulation allows scientists to vary many input parameters of the simulation to test a range of alternatives. The astronomers find that galaxies in the local A simulation of the stellar content of the universe today universe with more than about ten billion masses of seen across one hundred million light-years. stars will indeed tend to quench star production Astronomers used this simulation to investigate how once the energy in the winds from black hole accretion onto a supermassive black hole quenches accretion becomes larger than the gravitational galaxy star formation. Credit: The IllustrisTNG Project energy in the gas, and that this tends to happen when the mass of the supermassive black hole exceeds about one hundred and sixty million solar masses. This value appears to be quite sharply Astronomers studying how star formation evolved delineated: 90% of galaxies with smaller black over cosmic time have discovered that quiescent holes are actively star forming and 90% of galaxies galaxies (galaxies that are currently not making with larger black holes are quiescent.
  • Discerning the Difficult-To-Detect: Star Formation in Dwarf and Low Surface Brightness Galaxies

    Discerning the Difficult-To-Detect: Star Formation in Dwarf and Low Surface Brightness Galaxies

    DISCERNING THE DIFFICULT-TO-DETECT: STAR FORMATION IN DWARF AND LOW SURFACE BRIGHTNESS GALAXIES By ANNA CHARLENE WRIGHT A dissertation submitted to the School of Graduate Studies Rutgers, The State University of New Jersey in partial fulfillment of the requirements for the degree of Doctor of Philosophy Graduate Program in Physics and Astronomy written under the direction of Alyson Brooks and approved by New Brunswick, New Jersey October, 2020 ABSTRACT OF THE DISSERTATION Discerning the Difficult-to-Detect: Star Formation in Dwarf and Low Surface Brightness Galaxies By ANNA CHARLENE WRIGHT Dissertation Director: Alyson Brooks In this work, we use cosmological simulations to study patterns of star formation in galaxies that have traditionally been underrepresented in surveys of galaxy formation across cosmic history. Because simulations have typically not been tuned to produce them, dwarf galaxies and low surface brightness galaxies provide a unique opportunity to test whether or not the models that we use to make bright, high mass galaxies are universal. We find that our simulations are able to reproduce a broad range of dwarf galaxy star formation histories, as well as low surface brightness galaxies, and we use these results to interpret the origin of specific types of galaxies. We identify a population of star-forming dwarf galaxies in our simulations that have experienced long periods of little to no star formation and whose properties are consistent with several dwarf galaxies observed in the local universe. We find that star formation can be reignited in these galaxies even billions of years after a quenching event through interactions with streams of gas in the intergalactic medium that compress hot halo gas.
  • Powerful Outflows and Feedback from Active Galactic Nuclei

    Powerful Outflows and Feedback from Active Galactic Nuclei

    AA53CH04-King ARI 27 July 2015 7:13 Powerful Outflows and Feedback from Active Galactic Nuclei Andrew King and Ken Pounds Department of Physics and Astronomy, University of Leicester, Leicester LE1 7RH, United Kingdom; email: [email protected], [email protected] Annu. Rev. Astron. Astrophys. 2015. 53:115–54 Keywords First published online as a Review in Advance on supermassive black holes, accretion, M−σ relation, X-ray winds, molecular April 10, 2015 outflows, quenching of star formation The Annual Review of Astronomy and Astrophysics is online at astro.annualreviews.org Abstract This article’s doi: Active galactic nuclei (AGNs) represent the growth phases of the supermas- 10.1146/annurev-astro-082214-122316 Access provided by California Institute of Technology on 01/11/17. For personal use only. Annu. Rev. Astron. Astrophys. 2015.53:115-154. Downloaded from www.annualreviews.org sive black holes in the center of almost every galaxy. Powerful, highly ionized Copyright c 2015 by Annual Reviews. winds, with velocities ∼0.1–0.2c, are a common feature in X-ray spectra of All rights reserved luminous AGNs, offering a plausible physical origin for the well-known connections between the hole and properties of its host. Observability con- straints suggest that the winds must be episodic and detectable only for a few percent of their lifetimes. The most powerful wind feedback, establishing the M−σ relation, is probably not directly observable at all. The M−σ relation signals a global change in the nature of AGN feedback. At black hole masses below M−σ , feedback is confined to the immediate vicinity of the hole.