Radio Galaxies and Quasars
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A Study of Giant Radio Galaxies at Ratan-600 173
Bull. Spec. Astrophys. Obs., 2011, 66, 171–182 c Special Astrophysical Observatory of the Russian AS, 2018 A Study of Giant Radio Galaxies at RATAN-600 M.L. Khabibullinaa, O.V. Verkhodanova, M. Singhb, A. Piryab, S. Nandib, N.V. Verkhodanovaa a Special Astrophysical Observatory of the Russian AS, Nizhnij Arkhyz 369167, Russia; b Aryabhatta Research Institute of Observational Sciences, Manora Park, Nainital 263 129, India Received July 28, 2010; accepted September 15, 2010. We report the results of flux density measurements in the extended components of thirteen giant radio galaxies, made with the RATAN-600 in the centimeter range. Supplementing them with the WENSS, NVSS and GB6 survey data we constructed the spectra of the studied galaxy components. We computed the spectral indices in the studied frequency range and demonstrate the need for a detailed account of the integral contribution of such objects into the background radiation. Key words: Radio lines: galaxies—techniques: radar astronomy 1. INTRODUCTION than the one, expected from the evolutional models. As noted in [8], such radio galaxies may affect the According to the generally accepted definition, gi- processes of galaxy formation, since the pressure of ant radio galaxies (GRGs) are the radio sources with gas, outflowing from the radio source, may compress linear sizes greater than 1 Mpc, i.e. the largest ra- the cold gas clouds thus initiating the development dio sources in the Universe. They mostly belong to of stars on the one hand, and stop the formation of the morphological type FR II [1] and are identified galaxies on the other hand. -
Essential Radio Astronomy
February 2, 2016 Time: 09:25am chapter1.tex © Copyright, Princeton University Press. No part of this book may be distributed, posted, or reproduced in any form by digital or mechanical means without prior written permission of the publisher. 1 Introduction 1.1 AN INTRODUCTION TO RADIO ASTRONOMY 1.1.1 What Is Radio Astronomy? Radio astronomy is the study of natural radio emission from celestial sources. The range of radio frequencies or wavelengths is loosely defined by atmospheric opacity and by quantum noise in coherent amplifiers. Together they place the boundary be- tween radio and far-infrared astronomy at frequency ν ∼ 1 THz (1 THz ≡ 1012 Hz) or wavelength λ = c/ν ∼ 0.3 mm, where c ≈ 3 × 1010 cm s−1 is the vacuum speed of light. The Earth’s ionosphere sets a low-frequency limit to ground-based radio astronomy by reflecting extraterrestrial radio waves with frequencies below ν ∼ 10 MHz (λ ∼ 30 m), and the ionized interstellar medium of our own Galaxy absorbs extragalactic radio signals below ν ∼ 2 MHz. The radio band is very broad logarithmically: it spans the five decades between 10 MHz and 1 THz at the low-frequency end of the electromagnetic spectrum. Nearly everything emits radio waves at some level, via a wide variety of emission mechanisms. Few astronomical radio sources are obscured because radio waves can penetrate interstellar dust clouds and Compton-thick layers of neutral gas. Because only optical and radio observations can be made from the ground, pioneering radio astronomers had the first opportunity to explore a “parallel universe” containing unexpected new objects such as radio galaxies, quasars, and pulsars, plus very cold sources such as interstellar molecular clouds and the cosmic microwave background radiation from the big bang itself. -
The Jansky Very Large Array
The Jansky Very Large Array To ny B e a s l e y National Radio Astronomy Observatory Atacama Large Millimeter/submillimeter Array Expanded Very Large Array Robert C. Byrd Green Bank Telescope Very Long Baseline Array EVLA EVLA Project Overview • The EVLA Project is a major upgrade of the Very Large Array. Upgraded array JanskyVLA • The fundamental goal is to improve all the observational capabilities of the VLA (except spatial resolution) by at least an order of magnitude • The project will be completed by early 2013, on budget and schedule. • Key aspect: This is a leveraged project – building upon existing infrastructure of the VLA. Key EVLA Project Goals EVLA • Full frequency coverage from 1 to 50 GHz. – Provided by 8 frequency bands with cryogenic receivers. • Up to 8 GHz instantaneous bandwidth – All digital design to maximize instrumental stability and repeatability. • New correlator with 8 GHz/polarization capability – Designed, funded, and constructed by HIA/DRAO – Unprecedented flexibility in matching resources to attain science goals. • <3 Jy/beam (1-, 1-Hr) continuum sensitivity at most bands. • <1 mJy/beam (1-, 1-Hr, 1-km/sec) line sensitivity at most bands. • Noise-limited, full-field imaging in all Stokes parameters for most observational fields. Jansky VLA-VLA Comparison EVLA Parameter VLA EVLA Factor Current Point Source Cont. Sensitivity (1,12hr.) 10 Jy 1 Jy 10 2 Jy Maximum BW in each polarization 0.1 GHz 8 GHz 80 2 GHz # of frequency channels at max. BW 16 16,384 1024 4096 Maximum number of freq. channels 512 4,194,304 8192 12,288 Coarsest frequency resolution 50 MHz 2 MHz 25 2 MHz Finest frequency resolution 381 Hz 0.12 Hz 3180 .12 Hz # of full-polarization spectral windows 2 64 32 16 (Log) Frequency Coverage (1 – 50 GHz) 22% 100% 5 100% EVLA Project Status EVLA • Installation of new wideband receivers now complete at: – 4 – 8 GHz (C-Band) – 18 – 27 GHz (K-Band) – 27 – 40 GHz (Ka-Band) – 40 – 50 GHz (Q-Band) • Installation of remaining four bands completed late-2012: – 1 – 2 GHz (L-Band) 19 now, completed end of 2012. -
Gigantic Galaxies Discovered with the Meerkat Telescope
18 January 2021 Gigantic galaxies discovered with the MeerKAT telescope The two giant radio galaxies found with the MeerKAT telescope. In the background is the sky as seen in optical light. Overlaid in red is the radio light from the enormous radio galaxies, as seen by MeerKAT. Left: MGTC J095959.63+024608.6. Right: MGTC J100016.84+015133.0. Image: I. Heywood (Oxford/Rhodes/SARAO) Two giant radio galaxies have been discovered with South Africa's powerful MeerKAT telescope. These galaxies are amongst the largest single objects in the universe and are thought to be quite rare. The discovery has been published online in the Monthly Notices of the Royal Astronomical Society. The detection of two of these monsters by MeerKat, in a relatively small patch of sky suggests that these scarce giant radio galaxies may actually be much more common than previously thought. This gives astronomers vital clues about how galaxies have changed and evolved throughout cosmic history. Many galaxies have supermassive black holes residing in their midst. When large amounts of interstellar gas start to orbit and fall in towards the black hole, the black hole becomes 'active' and huge amounts of energy are released from this region of the galaxy. In some active galaxies, charged particles interact with the strong magnetic fields near the black hole and release huge beams, or 'jets' of radio light. The radio jets of these so-called 'radio galaxies' can be many times larger than the galaxy itself and can extend vast distances into intergalactic space. Dr Jacinta Delhaize, a Research Fellow at the University of Cape Town (UCT) and lead author of the work, said: "Many hundreds of thousands of radio galaxies have already been discovered. -
Data Fusion from Diverse Resources for Optical Identification Of
Astronomical Data Analysis Software and Systems XIII ASP Conference Series, Vol. 314, 2004 F. Ochsenbein, M. Allen, and D. Egret, eds. Data Fusion from Diverse Resources for Optical Identification of Radio Sources. O. P. Zhelenkova and V. V. Vitkovskij Informatics Department, Special Astrophysical Observatory of RAS Nizhnij Arkhyz, Russia, Email: [email protected] Abstract. Optical identification of the SS sample of the RC radio source catalogue was impossible without the use of additional astronom- ical resources. The volume of information for each source grew from the 100 bytes for each RC-catalogue row up to 10MB including radio and optical observations, information from catalogues and surveys, data pro- cessing results and files for Internet publication. Such work pushes us to find a solution for integration of heterogeneous data and realization of the discovery procedure. The experience gained in this project has allowed formalization of a procedure for distant radio galaxy discovery in the subject mediator context. 1. Introduction The BIG TRIO (Goss et al. 1992, 1994) project to investigate distant radio galaxies was carried out at the Special Astrophysical Observatory of RAS. The list of objects for research consisted of radio sources from the deep survey of the sky strip observed with RATAN-600 (Parijskij et al. 1991, 1992). 104 radio galaxies were selected from the 1145 objects in the RC catalogue. The candidates were selected by radio source parameters including steep spectra and FRII morphology (Parijskij et al. 1996). Most of the RC catalogue radio sources have flux densities between 5 and 50 mJy. 10% of sources have a steep spectrum (α ≥ 0.9) and 70% have double radio structure. -
High Resolution Radio Astronomy Using Very Long Baseline Interferometry
IOP PUBLISHING REPORTS ON PROGRESS IN PHYSICS Rep. Prog. Phys. 71 (2008) 066901 (32pp) doi:10.1088/0034-4885/71/6/066901 High resolution radio astronomy using very long baseline interferometry Enno Middelberg1 and Uwe Bach2 1 Astronomisches Institut, Universitat¨ Bochum, 44801 Bochum, Germany 2 Max-Planck-Institut fur¨ Radioastronomie, Auf dem Hugel¨ 69, 53121 Bonn, Germany E-mail: [email protected] and [email protected] Received 3 December 2007, in final form 11 March 2008 Published 2 May 2008 Online at stacks.iop.org/RoPP/71/066901 Abstract Very long baseline interferometry, or VLBI, is the observing technique yielding the highest-resolution images today. Whilst a traditionally large fraction of VLBI observations is concentrating on active galactic nuclei, the number of observations concerned with other astronomical objects such as stars and masers, and with astrometric applications, is significant. In the last decade, much progress has been made in all of these fields. We give a brief introduction to the technique of radio interferometry, focusing on the particularities of VLBI observations, and review recent results which would not have been possible without VLBI observations. This article was invited by Professor J Silk. Contents 1. Introduction 1 2.9. The future of VLBI: eVLBI, VLBI in space and 2. The theory of interferometry and aperture the SKA 10 synthesis 2 2.10. VLBI arrays around the world and their 2.1. Fundamentals 2 capabilities 10 2.2. Sources of error in VLBI observations 7 3. Astrophysical applications 11 2.3. The problem of phase calibration: 3.1. Active galactic nuclei and their jets 12 self-calibration 7 2.4. -
O. Ivy Wong – Radio Galaxy Zoo: Data Release 1
The Radio Galaxy Zoo Data Release 1: classifications for 75,589 sources O. Ivy Wong & Radio Galaxy Zoo Team ICRAR/University of Western Australia SPARCS VII – the precursors awaken, 19 July 2017 1 Norris+ 2012 Norris+ 2012 All-sky below deg All-sky declinations +20 Expect 70 million 70 radio Expect sources riding on the EMU'sback... on riding Survey Area Sensitivity limit (mJy) 2 Motivation There is nothing quite as useless as a radio source. – Condon, 2013 Translation: to understand how galaxies grow supermassive black holes & evolve, one needs context from multiwavelength observations 3 How to match 70 million radio sources to their hosts? ✔ humans (astronomers/their students) ✔ software matching algorithms - current matching algorithms work for 90% of sources (Norris'12) … so what about the other 7 million sources ? ➔ advance machine learning algorithms ➔ more humans? 4 Path ahead ... Clear need for new automated methods to make accurate cross-ids But, there exists many exotic radio morphologies that are not well catalogued/documented Step 1: create a large dataset with different radio source morphologies 5 radio.galaxyzoo.org 6 Combining archival datasets + Cutri+ 2013 Becker, White & Helfand 1995 + Franzen+ 2015, Norris+2006 Lonsdale+ 2003 7 Citizen scientists (radio.galaxyzoo.org) ✘ ✓ 8 radio.galaxyzoo.org 1) Examine radio & IR images 2) Identify radio source components 3) Mark location of host galaxy … stay tuned for Julie's talk 9 Radio Galaxy Zoo Data Release 1 ✔ Classifications between Dec 2013 & March 2016 ✔ 11,214 registered -
Help Find the Location of Newly Discovered Black Holes in the LOFAR Radio Galaxy Zoo Project 26 February 2020
Help find the location of newly discovered black holes in the LOFAR Radio Galaxy Zoo project 26 February 2020 Scientists are asking for the public's help to find the origin of hundreds of thousands of galaxies that have been discovered by the largest radio telescope ever built: LOFAR. Where do these mysterious objects that extend for thousands of light-years come from? A new citizen science project, LOFAR Radio Galaxy Zoo, gives anyone with a computer the exciting possibility to join the quest to find out where the black holes at the center of these galaxies are located. Astronomers use radio telescopes to make images of the radio sky, much like optical telescopes like the Hubble space telescope make maps of stars and galaxies. The difference is that the images made with a radio telescope show a sky that is very different from the sky that an optical telescope sees. In the radio sky, stars and galaxies are not directly seen but instead an abundance of complex structures linked to massive black holes at the centers of galaxies are detected. Most dust and gas surrounding a supermassive black hole gets consumed by the black hole, but part of the material will escape and gets ejected into deep space. This material forms large plumes of extremely hot gas, it is this gas that forms large structures that is observed by radio telescopes. The Low Frequency Array (LOFAR) telescope, As an example, take the case of the famous radio operated by the Netherlands Institute for Radio source 3C236. The upper image is the radio source, the Astronomy (ASTRON), is continuing its huge middle one an optical image showing many stars and survey of the radio sky and 4 million radio sources galaxies and the lower image an overlay of the radio and the optical image. -
Active Galactic Nuclei Imaging Programs of the Radioastron Mission
Active galactic nuclei imaging programs of the RadioAstron mission Gabriele Brunia,∗, Tuomas Savolainenb,c,d , Jose Luis G´omeze, Andrei P. Lobanovd, Yuri Y. Kovalevf,g,d , on behalf of the RadioAstron AGN imaging KSP teams aINAF - Istituto di Astrofisica e Planetologia Spaziali, via del Fosso delCavaliere 100, 00133 Rome, Italy bAalto University Department of Electronics and Nanoengineering, PL 15500, FI-00076 Aalto, Finland cAalto University Mets¨ahovi Radio Observatory, Mets¨ahovintie 114, 02540 Kylm¨al¨a, Finland dMax-Planck-Institut f¨ur Radioastronomie, Auf dem H¨ugel 69, 53121 Bonn, Germany eInstituto de Astrof´ısica de Andaluc´ıa, CSIC, Glorieta de la Astronom´ıa s/n, 18008 Granada, Spain f Astro Space Center of Lebedev PhysicalInstitute, Profsoyuznaya St. 84/32, 117997 Moscow, Russia gInstitute of Physics and Technology, Dolgoprudny, Institutsky per., 9, Moscow region, 141700, Russia Abstract Imaging relativistic jets in active galactic nuclei (AGN) at angular resolu- tion significantly surpassing that of the ground-based VLBI at centimetre wavelengths is one ofthe key science objectives ofthe RadioAstron space- VLBI mission. There are three RadioAstron imaging key science programs that target both nearby radio galaxies and blazars, with one of the programs specifically focusing on polarimetry of the jets. The first images from these programs reach angular resolution of a few tens of microarcseconds and reveal unprecedented details about the jet collimation profile, magnetic field con- figuration, and Kelvin-Helmholtz instabilities along the flow in some of the ∗Corresponding author Email addresses:[email protected] (Gabriele Bruni), [email protected] (Tuomas Savolainen), [email protected] (Jose Luis G´omez), [email protected] (Andrei P. -
Relativistic Effects
Relativistic Effects 1 Introduction The radio-emitting plasma in AGN contains electrons with relativistic energies. The Lorentz factors of the emitting elec- trons are of order 1026– . We now know that the bulk motion of the plasma is also moving relativistically – at least in some regions although probably “only” with Lorentz factors about 10 or so. However, this has an important effect on the prop- erties of the emitted radiation – principally through the ef- fects of relativistic beaming and doppler shifts in frequency. This in turn affects the inferred parameters of the plasma. Relativistic Effects ©Geoffrey V. Bicknell 2 Summary of special relativity For a more complete summary of 4-vectors and Special Rel- ativity, see Rybicki and Lightman, Radiative Processes in As- trophysics, or Rindler, Special Relativity High Energy Astrophysics: Relativistic Effects 2/93 2.1 The Lorentz transformation y S y S V x x The primed frame is moving wrt to the unprimed frame with a velocity v in the x–direction. The coordinates in the primed frame are related to those in the unprimed frame by: High Energy Astrophysics: Relativistic Effects 3/93 Vx x= xvt– t= t – ------ c2 y = y z = z (1) v 1 = -- = ------------------- c 1 – 2 We put the space-time coordinates on an equal footing by putting x0 = ct. The the xt– part of the Lorentz transforma- tion can be written: x= x – x0 x0= x0 – x (2) The reverse transformation is: High Energy Astrophysics: Relativistic Effects 4/93 x = x + Vt yy= zz= Vx (3) t = t + -------- c2 i.e., x = x+ x0 x0 = x0+ x (4) High Energy Astrophysics: Relativistic Effects 5/93 2.2 Lorentz–Fitzgerald contraction 2.3 Time dilation y y V S S x x High Energy Astrophysics: Relativistic Effects 6/93 y y S S V L0 x x 2 1 x – x = L0 2 1 x – x = x2 – x1 – Vt2 – t1 –1 L0 = L L = L0 High Energy Astrophysics: Relativistic Effects 7/93 Consider a clock at a stationary position in the moving frame which registers a time interval T0. -
Analysis of Kepler Active Galactic Nuclei Using a Revised Kirk, Rieger, Mastichiadis (1998) Model Sarah M
Florida International University FIU Digital Commons FIU Electronic Theses and Dissertations University Graduate School 6-12-2014 Analysis of Kepler Active Galactic Nuclei Using A Revised Kirk, Rieger, Mastichiadis (1998) Model Sarah M. Dhalla Florida International University, [email protected] DOI: 10.25148/etd.FI14071133 Follow this and additional works at: https://digitalcommons.fiu.edu/etd Recommended Citation Dhalla, Sarah M., "Analysis of Kepler Active Galactic Nuclei Using A Revised Kirk, Rieger, Mastichiadis (1998) Model" (2014). FIU Electronic Theses and Dissertations. 1521. https://digitalcommons.fiu.edu/etd/1521 This work is brought to you for free and open access by the University Graduate School at FIU Digital Commons. It has been accepted for inclusion in FIU Electronic Theses and Dissertations by an authorized administrator of FIU Digital Commons. For more information, please contact [email protected]. FLORIDA INTERNATIONAL UNIVERSITY Miami, Florida ANALYSIS OF KEPLER ACTIVE GALACTIC NUCLEI USING A REVISED KIRK, RIEGER, MASTICHIADIS (1998) JET MODEL A thesis submitted in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE in PHYSICS by Sarah Mohammed Dhalla 2014 To: Interim Dean Michael R. Heithaus College of Arts and Sciences This thesis, written by Sarah Mohammed Dhalla, and entitled Analysis of Kepler Active Galactic Nuclei Using a Revised Kirk, Rieger, & Mastichiadis (1998) Jet Model, having been approved in respect to style and intellectual content, is referred to you for judgment. We have read this thesis and recommend that it be approved. Caroline Simpson Walter Van Hamme James R. Webb, Major Professor Date of Defense: June 12, 2014 The thesis of Sarah Mohammed Dhalla is approved. -
11 Jets and Gamma-Ray Burst Unification Schemes
11 Jets and Gamma-Ray Burst Unification Schemes Jonathan Granot1 and Enrico Ramirez-Ruiz2 (1) Centre for Astrophysics Research, University of Hertfordshire, College Lane, Hatfield, Herts, AL10 9AB, UK (2) Astronomy and Astrophysics Department, University of California, Santa Cruz, CA 95064, USA 11.1 Evidence for bulk relativistic motion in gamma-ray bursts The first line of evidence for ultra-relativistic bulk motion of the outflows that produce GRBs arises from the compactness argument. It relies on the observed short and intense pulses of gamma rays and their non-thermal en- ergy spectrum that often extends up to high photon energies. Together, these facts imply that the emitting region must be moving relativistically. In order to understand this better, let us first consider a source that is either at rest or moves at a Newtonian velocity, β v/c 1, corresponding to a ≡ ≪ bulk Lorentz factor Γ (1 β2)−1/2 1. For such a source the observed ≡ − ≈ variability timescale (e.g., the width of the observed pulses) ∆t, implies a typical source size or radius R < c∆t, due to light time travel effects (for sim- plicity we ignore here cosmological effects, such as redshift or time dilation). GRBs often show significant variability down to millisecond timescales, im- plying R< 3 107(∆t/ 1 ms) cm. At cosmological distances their isotropic × equivalent luminosity, L, is typically in the range of 1050 1053 ergs−1. − In addition, the (observed part of the) εFε GRB spectrum typically peaks around a dimensionless photon energy of ε E /m c2 1, so that (for ≡ ph e ∼ a Newtonian source) a good fraction of the total radiated energy is carried by photons that can pair produce with other photons of similar energy.