Studies on Modified Gravity Theory
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Astronomie in Theorie Und Praxis 8. Auflage in Zwei Bänden Erik Wischnewski
Astronomie in Theorie und Praxis 8. Auflage in zwei Bänden Erik Wischnewski Inhaltsverzeichnis 1 Beobachtungen mit bloßem Auge 37 Motivation 37 Hilfsmittel 38 Drehbare Sternkarte Bücher und Atlanten Kataloge Planetariumssoftware Elektronischer Almanach Sternkarten 39 2 Atmosphäre der Erde 49 Aufbau 49 Atmosphärische Fenster 51 Warum der Himmel blau ist? 52 Extinktion 52 Extinktionsgleichung Photometrie Refraktion 55 Szintillationsrauschen 56 Angaben zur Beobachtung 57 Durchsicht Himmelshelligkeit Luftunruhe Beispiel einer Notiz Taupunkt 59 Solar-terrestrische Beziehungen 60 Klassifizierung der Flares Korrelation zur Fleckenrelativzahl Luftleuchten 62 Polarlichter 63 Nachtleuchtende Wolken 64 Haloerscheinungen 67 Formen Häufigkeit Beobachtung Photographie Grüner Strahl 69 Zodiakallicht 71 Dämmerung 72 Definition Purpurlicht Gegendämmerung Venusgürtel Erdschattenbogen 3 Optische Teleskope 75 Fernrohrtypen 76 Refraktoren Reflektoren Fokus Optische Fehler 82 Farbfehler Kugelgestaltsfehler Bildfeldwölbung Koma Astigmatismus Verzeichnung Bildverzerrungen Helligkeitsinhomogenität Objektive 86 Linsenobjektive Spiegelobjektive Vergütung Optische Qualitätsprüfung RC-Wert RGB-Chromasietest Okulare 97 Zusatzoptiken 100 Barlow-Linse Shapley-Linse Flattener Spezialokulare Spektroskopie Herschel-Prisma Fabry-Pérot-Interferometer Vergrößerung 103 Welche Vergrößerung ist die Beste? Blickfeld 105 Lichtstärke 106 Kontrast Dämmerungszahl Auflösungsvermögen 108 Strehl-Zahl Luftunruhe (Seeing) 112 Tubusseeing Kuppelseeing Gebäudeseeing Montierungen 113 Nachführfehler -
The Puzzle of the Strange Galaxy Made of 99.9% Dark Matter Is Solved 13 October 2020
The puzzle of the strange galaxy made of 99.9% dark matter is solved 13 October 2020 The galaxy Dragonfly 44 was discovered in a deep survey of the Coma cluster, a cluster with several thousand galaxies. From the start, the galaxy was considered remarkable by the researchers because the quantity of dark matter they inferred was almost as much as that in the Milky Way, the equivalent of a billion solar masses. However, instead of containing around a hundred thousand million stars, as has the Milky Way, DF44 has only a hundred million stars, a thousand times Image and amplification (in color) of the ultra-diffuse fewer. This means that the amount of dark matter galaxy Dragonfly 44 taken with the Hubble space was ten thousand times greater than that of its telescope. Credit: Teymoor Saifollahi and NASA/HST. stars. If this had been true, it would have been a unique object, with almost 100 times as much dark matter as that expected from the number of its stars. At present, the formation of galaxies is difficult to understand without the presence of a ubiquitous, Nevertheless, by an exhaustive analysis of the but mysterious component, termed dark matter. system of globular cluster around Dragonfly 44, the Astronomers have measure how much dark matter researchers have detected that the total number of there is around galaxies, and have found that it globular clusters is only 20, and that the total varies between 10 and 300 times the quantity of quantity of dark matter is around 300 times that of visible matter. -
A High Stellar Velocity Dispersion and ~100 Globular Clusters for the Ultra
San Jose State University From the SelectedWorks of Aaron J. Romanowsky 2016 A High Stellar Velocity Dispersion and ~100 Globular Clusters for the Ultra-Diffuse Galaxy Dragonfly 44 Pieter van Dokkum, Yale University Roberto Abraham, University of Toronto Jean P. Brodie, University of California Observatories Charlie Conroy, Harvard-Smithsonian Center for Astrophysics Shany Danieli, Yale University, et al. Available at: https://works.bepress.com/aaron_romanowsky/117/ The Astrophysical Journal Letters, 828:L6 (6pp), 2016 September 1 doi:10.3847/2041-8205/828/1/L6 © 2016. The American Astronomical Society. All rights reserved. A HIGH STELLAR VELOCITY DISPERSION AND ∼100 GLOBULAR CLUSTERS FOR THE ULTRA-DIFFUSE GALAXY DRAGONFLY 44 Pieter van Dokkum1, Roberto Abraham2, Jean Brodie3, Charlie Conroy4, Shany Danieli1, Allison Merritt1, Lamiya Mowla1, Aaron Romanowsky3,5, and Jielai Zhang2 1 Astronomy Department, Yale University, New Haven, CT 06511, USA 2 Department of Astronomy & Astrophysics, University of Toronto, 50 St. George Street, Toronto, ON M5S 3H4, Canada 3 University of California Observatories, 1156 High Street, Santa Cruz, CA 95064, USA 4 Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA, USA 5 Department of Physics and Astronomy, San José State University, San Jose, CA 95192, USA Received 2016 June 20; revised 2016 July 14; accepted 2016 July 15; published 2016 August 25 ABSTRACT Recently a population of large, very low surface brightness, spheroidal galaxies was identified in the Coma cluster. The apparent survival of these ultra-diffuse galaxies (UDGs) in a rich cluster suggests that they have very high masses. Here, we present the stellar kinematics of Dragonfly44, one of the largest Coma UDGs, using a 33.5 hr fi +8 -1 integration with DEIMOS on the Keck II telescope. -
Revisiting the Cooling Flow Problem in Galaxies, Groups, and Clusters of Galaxies
Revisiting the Cooling Flow Problem in Galaxies, Groups, and Clusters of Galaxies The MIT Faculty has made this article openly available. Please share how this access benefits you. Your story matters. Citation McDonald, Michael et. al., "Revisiting the Cooling Flow Problem in Galaxies, Groups, and Clusters of Galaxies." Astrophysical Journal 858, 1 (May 2018): no. 45 doi. 10.3847/1538-4357/AABACE ©2018 Authors As Published 10.3847/1538-4357/AABACE Publisher American Astronomical Society Version Final published version Citable link https://hdl.handle.net/1721.1/125311 Terms of Use Article is made available in accordance with the publisher's policy and may be subject to US copyright law. Please refer to the publisher's site for terms of use. The Astrophysical Journal, 858:45 (15pp), 2018 May 1 https://doi.org/10.3847/1538-4357/aabace © 2018. The American Astronomical Society. All rights reserved. Revisiting the Cooling Flow Problem in Galaxies, Groups, and Clusters of Galaxies M. McDonald1 , M. Gaspari2,5 , B. R. McNamara3 , and G. R. Tremblay4 1 Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139, USA; [email protected] 2 Department of Astrophysical Sciences, Princeton University, 4 Ivy Lane, Princeton, NJ 08544-1001, USA 3 Department of Physics & Astronomy, University of Waterloo, Canada 4 Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA Received 2018 January 6; revised 2018 March 13; accepted 2018 March 27; published 2018 May 3 Abstract We present a study of 107 galaxies, groups, and clusters spanning ∼3 orders of magnitude in mass, ∼5 orders of magnitude in central galaxy star formation rate (SFR), ∼4 orders of magnitude in the classical cooling rate (MMrrt˙ coolº< gas() cool cool) of the intracluster medium (ICM), and ∼5 orders of magnitude in the central black hole accretion rate. -
Spatially Resolved Stellar Kinematics of the Ultra-Diffuse Galaxy Dragonfly 44
The Astrophysical Journal, 880:91 (26pp), 2019 August 1 https://doi.org/10.3847/1538-4357/ab2914 © 2019. The American Astronomical Society. All rights reserved. Spatially Resolved Stellar Kinematics of the Ultra-diffuse Galaxy Dragonfly 44. I. Observations, Kinematics, and Cold Dark Matter Halo Fits Pieter van Dokkum1 , Asher Wasserman2 , Shany Danieli1 , Roberto Abraham3 , Jean Brodie2 , Charlie Conroy4 , Duncan A. Forbes5, Christopher Martin6, Matt Matuszewski6, Aaron J. Romanowsky2,7 , and Alexa Villaume2 1 Astronomy Department, Yale University, 52 Hillhouse Avenue, New Haven, CT 06511, USA 2 University of California Observatories, 1156 High Street, Santa Cruz, CA 95064, USA 3 Department of Astronomy & Astrophysics, University of Toronto, 50 St. George Street, Toronto, ON M5S 3H4, Canada 4 Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA, USA 5 Centre for Astrophysics and Supercomputing, Swinburne University, Hawthorn, VIC 3122, Australia 6 Cahill Center for Astrophysics, California Institute of Technology, 1216 East California Boulevard, Mail Code 278-17, Pasadena, CA 91125, USA 7 Department of Physics and Astronomy, San José State University, San Jose, CA 95192, USA Received 2019 March 31; revised 2019 May 25; accepted 2019 June 5; published 2019 July 30 Abstract We present spatially resolved stellar kinematics of the well-studied ultra-diffuse galaxy (UDG) Dragonfly44, as determined from 25.3 hr of observations with the Keck Cosmic Web Imager. The luminosity-weighted dispersion +3 −1 within the half-light radius is s12= 33-3 km s , lower than what we had inferred before from a DEIMOS spectrum in the Hα region. There is no evidence for rotation, with Vmax áñ<s 0.12 (90% confidence) along the major axis, in possible conflict with models where UDGs are the high-spin tail of the normal dwarf galaxy distribution. -
The Extragalactic Distance Scale
The Extragalactic Distance Scale Published in "Stellar astrophysics for the local group" : VIII Canary Islands Winter School of Astrophysics. Edited by A. Aparicio, A. Herrero, and F. Sanchez. Cambridge ; New York : Cambridge University Press, 1998 Calibration of the Extragalactic Distance Scale By BARRY F. MADORE1, WENDY L. FREEDMAN2 1NASA/IPAC Extragalactic Database, Infrared Processing & Analysis Center, California Institute of Technology, Jet Propulsion Laboratory, Pasadena, CA 91125, USA 2Observatories, Carnegie Institution of Washington, 813 Santa Barbara St., Pasadena CA 91101, USA The calibration and use of Cepheids as primary distance indicators is reviewed in the context of the extragalactic distance scale. Comparison is made with the independently calibrated Population II distance scale and found to be consistent at the 10% level. The combined use of ground-based facilities and the Hubble Space Telescope now allow for the application of the Cepheid Period-Luminosity relation out to distances in excess of 20 Mpc. Calibration of secondary distance indicators and the direct determination of distances to galaxies in the field as well as in the Virgo and Fornax clusters allows for multiple paths to the determination of the absolute rate of the expansion of the Universe parameterized by the Hubble constant. At this point in the reduction and analysis of Key Project galaxies H0 = 72km/ sec/Mpc ± 2 (random) ± 12 [systematic]. Table of Contents INTRODUCTION TO THE LECTURES CEPHEIDS BRIEF SUMMARY OF THE OBSERVED PROPERTIES OF CEPHEID -
The Luminosity Function of the Milky Way Satellites
Draft version June 3, 2018 A Preprint typeset using LTEX style emulateapj v. 02/07/07 THE LUMINOSITY FUNCTION OF THE MILKY WAY SATELLITES S. Koposov1,2, V. Belokurov2, N.W. Evans2, P.C. Hewett2, M.J. Irwin2, G. Gilmore2, D.B. Zucker2, H.-W. Rix1, M. Fellhauer2, E.F. Bell1, E.V. Glushkova3 Draft version June 3, 2018 ABSTRACT We quantify the detectability of stellar Milky Way satellites in the Sloan Digital Sky Survey (SDSS) Data Release 5. We show that the effective search volumes for the recently discovered SDSS–satellites depend strongly on their luminosity, with their maximum distance, Dmax, substantially smaller than the Milky Way halo’s virial radius. Calculating the maximum accessible volume, Vmax, for all faint detected satellites, allows the calculation of the luminosity function for Milky Way satellite galaxies, accounting quantitatively for their detectability. We find that the number density of satellite galaxies continues to rise towards low luminosities, but may flatten at MV 5; within the uncertainties, the ∼− 0.1(MV +5) luminosity function can be described by a single power law dN/dMV = 10 10 , spanning × luminosities from MV = 2 all the way to the luminosity of the Large Magellanic Cloud. Comparing these results to several semi-analytic− galaxy formation models, we find that their predictions differ significantly from the data: either the shape of the luminosity function, or the surface brightness distributions of the models, do not match. Subject headings: Galaxy: halo – Galaxy: structure – Galaxy: formation – Local Group 1. INTRODUCTION ing satellite” problem. First identified by Klypin et al. In Cold Dark Matter (CDM) models, large spiral (1999) and Moore et al. -
The Origin of Ultra Diffuse Galaxies: Stellar Feedback and Quenching
MNRAS 478, 906–925 (2018) doi:10.1093/mnras/sty1153 Advance Access publication 2018 May 4 The origin of ultra diffuse galaxies: stellar feedback and quenching T. K. Chan,1‹ D. Keres,ˇ 1 A. Wetzel,2,3,4† P. F. Hopkins,2 C.-A. Faucher-Giguere,` 5 K. El-Badry,6 S. Garrison-Kimmel2 and M. Boylan-Kolchin7 1Department of Physics, Center for Astrophysics and Space Sciences, University of California at San Diego, 9500 Gilman Drive, La Jolla, CA 92093, USA 2TAPIR, Mailcode 350-17, California Institute of Technology, Pasadena, CA 91125, USA 3The Observatories of the Carnegie Institution for Science, Pasadena, CA 91101, USA 4Department of Physics, University of California, Davis, CA 95616, USA 5Department of Physics and Astronomy and CIERA, Northwestern University, 2145 Sheridan Road, Evanston, IL 60208, USA 6Department of Astronomy and Theoretical Astrophysics Center, University of California Berkeley, Berkeley, CA 94720, USA 7Department of Astronomy, The University of Texas at Austin, 2515 Speedway, Stop C1400, Austin, TX 78712-1205, USA Accepted 2018 May 1. Received 2018 March 21; in original form 2017 November 12 ABSTRACT We test if the cosmological zoom-in simulations of isolated galaxies from the FIRE project reproduce the properties of ultra diffuse galaxies (UDGs). We show that outflows that dy- namically heat galactic stars, together with a passively aging stellar population after imposed quenching, naturally reproduce the observed population of red UDGs, without the need for high spin haloes, or dynamical influence from their host cluster. We reproduce the range of surface brightness, radius, and absolute magnitude of the observed red UDGs by quenching simulated galaxies at a range of different times. -
And Ecclesiastical Cosmology
GSJ: VOLUME 6, ISSUE 3, MARCH 2018 101 GSJ: Volume 6, Issue 3, March 2018, Online: ISSN 2320-9186 www.globalscientificjournal.com DEMOLITION HUBBLE'S LAW, BIG BANG THE BASIS OF "MODERN" AND ECCLESIASTICAL COSMOLOGY Author: Weitter Duckss (Slavko Sedic) Zadar Croatia Pусскй Croatian „If two objects are represented by ball bearings and space-time by the stretching of a rubber sheet, the Doppler effect is caused by the rolling of ball bearings over the rubber sheet in order to achieve a particular motion. A cosmological red shift occurs when ball bearings get stuck on the sheet, which is stretched.“ Wikipedia OK, let's check that on our local group of galaxies (the table from my article „Where did the blue spectral shift inside the universe come from?“) galaxies, local groups Redshift km/s Blueshift km/s Sextans B (4.44 ± 0.23 Mly) 300 ± 0 Sextans A 324 ± 2 NGC 3109 403 ± 1 Tucana Dwarf 130 ± ? Leo I 285 ± 2 NGC 6822 -57 ± 2 Andromeda Galaxy -301 ± 1 Leo II (about 690,000 ly) 79 ± 1 Phoenix Dwarf 60 ± 30 SagDIG -79 ± 1 Aquarius Dwarf -141 ± 2 Wolf–Lundmark–Melotte -122 ± 2 Pisces Dwarf -287 ± 0 Antlia Dwarf 362 ± 0 Leo A 0.000067 (z) Pegasus Dwarf Spheroidal -354 ± 3 IC 10 -348 ± 1 NGC 185 -202 ± 3 Canes Venatici I ~ 31 GSJ© 2018 www.globalscientificjournal.com GSJ: VOLUME 6, ISSUE 3, MARCH 2018 102 Andromeda III -351 ± 9 Andromeda II -188 ± 3 Triangulum Galaxy -179 ± 3 Messier 110 -241 ± 3 NGC 147 (2.53 ± 0.11 Mly) -193 ± 3 Small Magellanic Cloud 0.000527 Large Magellanic Cloud - - M32 -200 ± 6 NGC 205 -241 ± 3 IC 1613 -234 ± 1 Carina Dwarf 230 ± 60 Sextans Dwarf 224 ± 2 Ursa Minor Dwarf (200 ± 30 kly) -247 ± 1 Draco Dwarf -292 ± 21 Cassiopeia Dwarf -307 ± 2 Ursa Major II Dwarf - 116 Leo IV 130 Leo V ( 585 kly) 173 Leo T -60 Bootes II -120 Pegasus Dwarf -183 ± 0 Sculptor Dwarf 110 ± 1 Etc. -
Highlighting Ultra Diffuse Galaxies: VCC 1287 and Dragonfly 44 AS DISCUSSED in VAN DOKKUM ET AL
Highlighting Ultra Diffuse Galaxies: VCC 1287 and Dragonfly 44 AS DISCUSSED IN VAN DOKKUM ET AL. 2016, BEASLEY ET AL. 2016 PRESENTED BY MICHAEL SANDOVAL Overview §Brief Overview of Galactic Structure and Globular Clusters (GCs) §Background of Ultra Diffuse Galaxies (UDGs) §The Search Process: Challenges and Importance §Dragonfly 44 §VCC 1287 §Big Picture: what do the results mean? Crash Course: Galactic Structure and GCs §Focusing on two features: § Globular Clusters (GCs) § Dark Matter Halo (DMH) §GCs extend to the outer halo and are used for dynamics measurements §DMH extends passed the visible structure What is a UDG? •Galaxies the size of the Milky Way, but significantly less bright •Problem: Act like they have very high mass, but have very little mass….? •Large dark matter fractions •Relatively featureless, but round and red •Not sure how they are formed • Perhaps they are “failed” galaxies? • Maybe from tidal forces? Reference: van Dokkum et al. 2016 Reference: Sandoval et al. 2015 Search Process – The Dragonfly •The Dragonfly Telephoto Array • Collaboration between Yale and University of Toronto in 2013 • Designed by Pieter van Dokkum & Roberto Abraham • Multi-lens array designed for ultra-low brightness visible astro • 400mm Canon lenses – as of 2016 Dragonfly has 48 lenses • Cold Dark Matter (CDM) cosmology Reference: Abraham & van Dokkum 2014 Search Process – Computational Method •Utilize images from Canada France Hawaii Telescope (CFHT) •MegaPrime/MegaCam is the wide-field optical imaging facility at CFHT. •Comparable to the Sloan Digital Sky Survey’s (SDSS) navigation tool. •Search through optical images looking for diffuse galaxies. •Analyze photometry The Early Discoveries •47 UDGs found with the Dragonfly in 2014 in the Coma cluster • Combined data with SDSS, CFHT • Radial velocity measurements (Coma: cz ∼ 7090 km/s) •Stony Brook, National Astronomical Observatory of Japan (NAOJ) follow up • Discovery of 854 UDGs in the Coma cluster • Analyzed data from the Subaru Reference: van Dokkum et al. -
Radial Temperature Profiles for a Large Sample of Galaxy Clusters Observed with XMM-Newton
A&A 486, 359–373 (2008) Astronomy DOI: 10.1051/0004-6361:200809538 & c ESO 2008 Astrophysics Radial temperature profiles for a large sample of galaxy clusters observed with XMM-Newton A. Leccardi1,2 and S. Molendi2 1 Università degli Studi di Milano, Dip. di Fisica, via Celoria 16, 20133 Milano, Italy 2 INAF-IASF Milano, via Bassini 15, 20133 Milano, Italy e-mail: [email protected] Received 8 February 2008 / Accepted 8 April 2008 ABSTRACT Aims. We measure radial temperature profiles as far out as possible for a sample of ≈50 hot, intermediate redshift galaxy clusters, selected from the XMM-Newton archive, keeping systematic errors under control. Methods. Our work is characterized by two major improvements. First, we used background modeling, rather than background subtraction, and the Cash statistic rather than the χ2. This method requires a careful characterization of all background components. Second, we assessed systematic effects in detail. We performed two groups of tests. Prior to the analysis, we made use of extensive simulations to quantify the impact of different spectral components on simulated spectra. After the analysis, we investigated how the measured temperature profile changes, when choosing different key parameters. Results. The mean temperature profile declines beyond 0.2 R180. For the first time, we provide an assessment of the source and the magnitude of systematic uncertainties. When comparing our profile with those obtained from hydrodynamic simulations, we find the slopes beyond ≈0.2 R180 to be similar. Our mean profile is similar but somewhat flatter with respect to those obtained by previous observational works, possibly as a consequence of a different level of characterizing systematic effects. -
Astroph0807.3345 Ful
Draft version July 22, 2008 A Preprint typeset using LTEX style emulateapj v. 08/13/06 THE INVISIBLES: A DETECTION ALGORITHM TO TRACE THE FAINTEST MILKY WAY SATELLITES S. M. Walsh1, B. Willman2, H. Jerjen1 Draft version July 22, 2008 ABSTRACT A specialized data mining algorithm has been developed using wide-field photometry catalogues, en- abling systematic and efficient searches for resolved, extremely low surface brightness satellite galaxies in the halo of the Milky Way (MW). Tested and calibrated with the Sloan Digital Sky Survey Data Release 6 (SDSS-DR6) we recover all fifteen MW satellites recently detected in SDSS, six known MW/Local Group dSphs in the SDSS footprint, and 19 previously known globular and open clusters. In addition, 30 point source overdensities have been found that correspond to no cataloged objects. The detection efficiencies of the algorithm have been carefully quantified by simulating more than three million model satellites embedded in star fields typical of those observed in SDSS, covering a wide range of parameters including galaxy distance, scale-length, luminosity, and Galactic latitude. We present several parameterizations of these detection limits to facilitate comparison between the observed Milky Way satellite population and predictions. We find that all known satellites would be detected with > 90% efficiency over all latitudes spanned by DR6 and that the MW satellite census within DR6 is complete to a magnitude limit of MV ≈−6.5 and a distance of 300 kpc. Assuming all existing MW satellites contain an appreciable old stellar population and have sizes and luminosities comparable to currently known companions, we predict a lower limit total of 52 Milky Way dwarf satellites within ∼ 260 kpc if they are uniformly distributed across the sky.