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Structure of the Outer Galactic Disc with Gaia DR2 Ž
A&A 637, A96 (2020) Astronomy https://doi.org/10.1051/0004-6361/201937289 & c ESO 2020 Astrophysics Structure of the outer Galactic disc with Gaia DR2 Ž. Chrobáková1,2, R. Nagy3, and M. López-Corredoira1,2 1 Instituto de Astrofísica de Canarias, 38205 La Laguna, Tenerife, Spain e-mail: [email protected] 2 Departamento de Astrofísica, Universidad de La Laguna, 38206 La Laguna, Tenerife, Spain 3 Faculty of Mathematics, Physics, and Informatics, Comenius University, Mlynská dolina, 842 48 Bratislava, Slovakia Received 9 December 2019 / Accepted 31 March 2020 ABSTRACT Context. The structure of outer disc of our Galaxy is still not well described, and many features need to be better understood. The second Gaia data release (DR2) provides data in unprecedented quality that can be analysed to shed some light on the outermost parts of the Milky Way. Aims. We calculate the stellar density using star counts obtained from Gaia DR2 up to a Galactocentric distance R = 20 kpc with a deconvolution technique for the parallax errors. Then we analyse the density in order to study the structure of the outer Galactic disc, mainly the warp. Methods. In order to carry out the deconvolution, we used the Lucy inversion technique for recovering the corrected star counts. We also used the Gaia luminosity function of stars with MG < 10 to extract the stellar density from the star counts. Results. The stellar density maps can be fitted by an exponential disc in the radial direction hr = 2:07 ± 0:07 kpc, with a weak dependence on the azimuth, extended up to 20 kpc without any cut-off. -
Arxiv:1802.01493V7 [Astro-Ph.GA] 10 Feb 2021 Ceeainbtti Oe Eoe Rbeai Tselrsae.I Scales
Variable Modified Newtonian Mechanics II: Baryonic Tully Fisher Relation C. C. Wong Department of Electrical and Electronic Engineering, University of Hong Kong. H.K. (Dated: February 11, 2021) Recently we find a single-metric solution for a point mass residing in an expanding universe [1], which apart from the Newtonian acceleration, gives rise to an additional MOND-like acceleration in which the MOND acceleration a0 is replaced by the cosmological acceleration. We study a Milky Way size protogalactic cloud in this acceleration, in which the growth of angular momentum can lead to an end of the overdensity growth. Within realistic redshifts, the overdensity stops growing at a value where the MOND-like acceleration dominates over Newton and the outer mass shell rotational velocity obeys the Baryonic Tully Fisher Relation (BTFR) with a smaller MOND acceleration. As the outer mass shell shrinks to a few scale length distances, the rotational velocity BTFR persists due to the conservation of angular momentum and the MOND acceleration grows to the phenomenological MOND acceleration value a0 at late time. PACS numbers: ?? INTRODUCTION A common response to the non-Newtonian rotational curve of a galaxy is that its ”Newtonian” dynamics requires cold dark matter (DM) particles. However, the small observed scatter of empirical Baryonic Tully-Fisher Relation (BTFR) of gas rich galaxies, see McGaugh [2]-Lelli [3], Milgrom [4] and Sanders [5], continues to motivate the hunt for a non-Newtonian connection between the rotational speeds and the baryon mass. On the modified DM theory front, Khoury [6] proposes a DM Bose-Einstein Condensate (BEC) phase where DM can interact more strongly with baryons. -
An Extended Star Formation History in an Ultra-Compact Dwarf
MNRAS 451, 3615–3626 (2015) doi:10.1093/mnras/stv1221 An extended star formation history in an ultra-compact dwarf Mark A. Norris,1‹ Carlos G. Escudero,2,3,4 Favio R. Faifer,2,3,4 Sheila J. Kannappan,5 Juan Carlos Forte4,6 and Remco C. E. van den Bosch1 1Max Planck Institut fur¨ Astronomie, Konigstuhl¨ 17, D-69117 Heidelberg, Germany 2Facultad de Cs. Astronomicas´ y Geof´ısicas, UNLP, Paseo del Bosque S/N, 1900 La Plata, Argentina 3Instituto de Astrof´ısica de La Plata (CCT La Plata – CONICET – UNLP), Paseo del Bosque S/N, 1900 La Plata, Argentina 4Consejo Nacional de Investigaciones Cient´ıficas y Tecnicas,´ Rivadavia 1917, C1033AAJ Ciudad Autonoma´ de Buenos Aires, Argentina 5Department of Physics and Astronomy UNC-Chapel Hill, CB 3255, Phillips Hall, Chapel Hill, NC 27599-3255, USA 6Planetario Galileo Galilei, Secretar´ıa de Cultura, Ciudad Autonoma´ de Buenos Aires, Argentina Accepted 2015 May 29. Received 2015 May 28; in original form 2015 April 2 ABSTRACT Downloaded from There has been significant controversy over the mechanisms responsible for forming compact stellar systems like ultra-compact dwarfs (UCDs), with suggestions that UCDs are simply the high-mass extension of the globular cluster population, or alternatively, the liberated nuclei of galaxies tidally stripped by larger companions. Definitive examples of UCDs formed by either route have been difficult to find, with only a handful of persuasive examples of http://mnras.oxfordjournals.org/ stripped-nucleus-type UCDs being known. In this paper, we present very deep Gemini/GMOS spectroscopic observations of the suspected stripped-nucleus UCD NGC 4546-UCD1 taken in good seeing conditions (<0.7 arcsec). -
Dusty Star-Forming Galaxies and Supermassive Black Holes at High Redshifts: in Situ Coevolution
SISSA - International School for Advanced Studies Dusty Star-Forming Galaxies and Supermassive Black Holes at High Redshifts: In Situ Coevolution Thesis Submitted for the Degree of “Doctor Philosophiæ” Supervisors Candidate Prof. Andrea Lapi Claudia Mancuso Prof. Gianfranco De Zotti Prof. Luigi Danese October 2016 ii To my fiancè Federico, my sister Ilaria, my mother Ennia, Gaia and Luna, my Big family. "Quando canterai la tua canzone, la canterai con tutto il tuo volume, che sia per tre minuti o per la vita, avrá su il tuo nome." Luciano Ligabue Contents Declaration of Authorship xi Abstract xiii 1 Introduction 1 2 Star Formation in galaxies 9 2.1 Initial Mass Function (IMF) and Stellar Population Synthesis (SPS) . 10 2.1.1 SPS . 12 2.2 Dust in galaxies . 12 2.3 Spectral Energy Distribution (SED) . 15 2.4 SFR tracers . 19 2.4.1 Emission lines . 20 2.4.2 X-ray flux . 20 2.4.3 UV luminosity . 20 2.4.4 IR emission . 21 2.4.5 UV vs IR . 22 2.4.6 Radio emission . 23 3 Star Formation Rate Functions 25 3.1 Reconstructing the intrinsic SFR function . 25 3.1.1 Validating the SFR functions via indirect observables . 29 3.1.2 Validating the SFRF via the continuity equation . 32 3.2 Linking to the halo mass via the abundance matching . 35 4 Hunting dusty star-forming galaxies at high-z 43 4.1 Selecting dusty galaxies in the far-IR/(sub-)mm band . 43 iii iv CONTENTS 4.2 Dusty galaxies are not lost in the UV band . -
Arxiv:2001.00331V2 [Astro-Ph.GA] 27 Feb 2020 Et Al
Draft version February 28, 2020 Typeset using LATEX twocolumn style in AASTeX62 The Carnegie-Irvine Galaxy Survey. IX. Classification of Bulge Types and Statistical Properties of Pseudo Bulges Hua Gao (高f),1, 2 Luis C. Ho,2, 1 Aaron J. Barth,3 and Zhao-Yu Li4 1Department of Astronomy, School of Physics, Peking University, Beijing 100871, China 2Kavli Institute for Astronomy and Astrophysics, Peking University, Beijing 100871, China 3Department of Physics and Astronomy, University of California at Irvine, 4129 Frederick Reines Hall, Irvine, CA 92697-4575, USA 4Department of Astronomy, Shanghai Jiao Tong University, Shanghai 200240, China ABSTRACT We study the statistical properties of 320 bulges of disk galaxies in the Carnegie-Irvine Galaxy Survey, using robust structural parameters of galaxies derived from image fitting. We apply the Kormendy relation to classify classical and pseudo bulges and characterize bulge dichotomy with respect to bulge structural properties and physical properties of host galaxies. We confirm previous findings that pseudo bulges on average have smaller S´ersic indices, smaller bulge-to-total ratios, and fainter surface brightnesses when compared with classical bulges. Our sizable sample statistically shows that pseudo bulges are more intrinsically flattened than classical bulges. Pseudo bulges are most frequent (incidence & 80%) in late-type spirals (later than Sc). Our measurements support the picture in which pseudo bulges arose from star formation induced by inflowing gas, while classical bulges were born out of violent processes such as mergers and coalescence of clumps. We reveal differences with the literature that warrant attention: (1) the bimodal distribution of S´ersicindices presented by previous studies is not reproduced in our study; (2) classical and pseudo bulges have similar relative bulge sizes; and (3) the pseudo bulge fraction is considerably smaller in early-type disks compared with previous studies based on one-dimensional surface brightness profile fitting. -
Scaling Mass Profiles Around Elliptical Galaxies Observed with Chandra
Scaling Mass Profiles around Elliptical Galaxies Observed with Chandra and XMM-Newton Y. Fukazawa1, J. G. Betoya-Nonesa1, J. Pu1, A. Ohto1, and N. Kawano1 Department of Physical Science, School of Science, Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-8526 [email protected] ABSTRACT We investigated the dynamical structure of 53 elliptical galaxies, based on the Chandra archival X-ray data. In X-ray luminous galaxies, a temperature increases with radius and a gas density is systematically higher at the optical outskirts, indicating a presence of a significant amount of the group-scale hot gas. In contrast, X-ray dim galaxies show a flat or declining temperature profile against radius and the gas density is relatively lower at the optical outskirts. Thus it is found that X-ray bright and faint elliptical galaxies are clearly distinguished by the temperature and gas density profile. The mass profile is well scaled by a virial radius r200 rather than an optical-half radius re, and is quite similar at (0.001 − 0.03)r200 between X-ray luminous and dim galaxies, and smoothly connects to those of clusters of galaxies. At the inner region of (0.001 − 0.01)r200 or (0.1 − 1)re, the mass profile well traces a stellar mass with a constant mass-to- light ratio of M/LB =3 − 10(M⊙/L⊙). M/LB ratio of X-ray bright galaxies rises up steeply beyond 0.01r200, and thus requires a presence of massive dark matter halo. From the deprojection analysis combined with the XMM-Newton data, we arXiv:astro-ph/0509521v1 18 Sep 2005 found that X-ray dim galaxies, NGC 3923, NGC 720, and IC 1459, also have a high M/LB ratio of 20–30 at 20 kpc, comparable to that of X-ray luminous galaxies. -
The Milky Way Galaxy Contents Summary
UNESCO EOLSS ENCYCLOPEDIA The Milky Way galaxy James Binney Physics Department Oxford University Key Words: Milky Way, galaxies Contents Summary • Introduction • Recognition of the size of the Milky Way • The Centre • The bulge-bar • History of the bulge Globular clusters • Satellites • The disc • Spiral structure Interstellar gas Moving groups, associations and star clusters The thick disc Local mass density The dark halo • Summary Our Galaxy is typical of the galaxies that dominate star formation in the present Universe. It is a barred spiral galaxy – a still-forming disc surrounds an old and barred spheroid. A massive black hole marks the centre of the Galaxy. The Sun sits far out in the disc and in visible light our view of the Galaxy is limited by interstellar dust. Consequently, the large-scale structure of the Galaxy must be inferred from observations made at infrared and radio wavelengths. The central bar and spiral structure in the stellar disc generate significant non-axisymmetric gravitational forces that make the gas disc and its embedded star formation strongly non-axisymmetric. Molecular hydrogen is more centrally concentrated than atomic hydrogen and much of it is contained in molecular clouds within which stars form. Probably all stars are formed in an association or cluster, and energy released by the more massive stars quickly disperses gas left over from their birth. This dispersal of residual gas usually leads to the dissolution of the association or cluster. The stellar disc can be decomposed to a thin disc, which comprises stars formed over most of the Galaxy’s lifetime, and a thick disc, which contains only stars formed in about the Galaxy’s first gigayear. -
Monthly Newsletter of the Durban Centre - March 2018
Page 1 Monthly Newsletter of the Durban Centre - March 2018 Page 2 Table of Contents Chairman’s Chatter …...…………………….……….………..….…… 3 Andrew Gray …………………………………………...………………. 5 The Hyades Star Cluster …...………………………….…….……….. 6 At the Eye Piece …………………………………………….….…….... 9 The Cover Image - Antennae Nebula …….……………………….. 11 Galaxy - Part 2 ….………………………………..………………….... 13 Self-Taught Astronomer …………………………………..………… 21 The Month Ahead …..…………………...….…….……………..…… 24 Minutes of the Previous Meeting …………………………….……. 25 Public Viewing Roster …………………………….……….…..……. 26 Pre-loved Telescope Equipment …………………………...……… 28 ASSA Symposium 2018 ………………………...……….…......…… 29 Member Submissions Disclaimer: The views expressed in ‘nDaba are solely those of the writer and are not necessarily the views of the Durban Centre, nor the Editor. All images and content is the work of the respective copyright owner Page 3 Chairman’s Chatter By Mike Hadlow Dear Members, The third month of the year is upon us and already the viewing conditions have been more favourable over the last few nights. Let’s hope it continues and we have clear skies and good viewing for the next five or six months. Our February meeting was well attended, with our main speaker being Dr Matt Hilton from the Astrophysics and Cosmology Research Unit at UKZN who gave us an excellent presentation on gravity waves. We really have to be thankful to Dr Hilton from ACRU UKZN for giving us his time to give us presentations and hope that we can maintain our relationship with ACRU and that we can draw other speakers from his colleagues and other research students! Thanks must also go to Debbie Abel and Piet Strauss for their monthly presentations on NASA and the sky for the following month, respectively. -
Structural Parameters of Compact Stellar Systems
Structural Parameters of Compact Stellar Systems Juan Pablo Madrid Presented in fulfillment of the requirements of the degree of Doctor of Philosophy May 2013 Faculty of Information and Communication Technology Swinburne University Abstract The objective of this thesis is to establish the observational properties and structural parameters of compact stellar systems that are brighter or larger than the “standard” globular cluster. We consider a standard globular cluster to be fainter than M 11 V ∼ − mag and to have an effective radius of 3 pc. We perform simulations to further un- ∼ derstand observations and the relations between fundamental parameters of dense stellar systems. With the aim of establishing the photometric and structural properties of Ultra- Compact Dwarfs (UCDs) and extended star clusters we first analyzed deep F475W (Sloan g) and F814W (I) Hubble Space Telescope images obtained with the Advanced Camera for Surveys. We fitted the light profiles of 5000 point-like sources in the vicinity of NGC ∼ 4874 — one of the two central dominant galaxies of the Coma cluster. Also, NGC 4874 has one of the largest globular cluster systems in the nearby universe. We found that 52 objects have effective radii between 10 and 66 pc, in the range spanned by extended star ∼ clusters and UCDs. Of these 52 compact objects, 25 are brighter than M 11 mag, V ∼ − a magnitude conventionally thought to separate UCDs and globular clusters. We have discovered both a red and a blue subpopulation of Ultra-Compact Dwarf (UCD) galaxy candidates in the Coma galaxy cluster. Searching for UCDs in an environment different to galaxy clusters we found eleven Ultra-Compact Dwarf and 39 extended star cluster candidates associated with the fossil group NGC 1132. -
Disk Galaxy Rotation Curves and Dark Matter Distribution
View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by CERN Document Server Disk galaxy rotation curves and dark matter distribution by Dilip G. Banhatti School of Physics, Madurai-Kamaraj University, Madurai 625021, India [Based on a pedagogic / didactic seminar given by DGB at the Graduate College “High Energy & Particle Astrophysics” at Karlsruhe in Germany on Friday the 20 th January 2006] Abstract . After explaining the motivation for this article, we briefly recapitulate the methods used to determine the rotation curves of our Galaxy and other spiral galaxies in their outer parts, and the results of applying these methods. We then present the essential Newtonian theory of (disk) galaxy rotation curves. The next two sections present two numerical simulation schemes and brief results. Finally, attempts to apply Einsteinian general relativity to the dynamics are described. The article ends with a summary and prospects for further work in this area. Recent observations and models of the very inner central parts of galaxian rotation curves are omitted, as also attempts to apply modified Newtonian dynamics to the outer parts. Motivation . Extensive radio observations determined the detailed rotation curve of our Milky Way Galaxy as well as other (spiral) disk galaxies to be flat much beyond their extent as seen in the optical band. Assuming a balance between the gravitational and centrifugal forces within Newtonian mechanics, the orbital speed V is expected to fall with the galactocentric distance r as V 2 = GM/r beyond the physical extent of the galaxy of mass M, G being the gravitational constant. -
ALABAMA University Libraries
THE UNIVERSITY OF ALABAMA University Libraries O VI In Elliptical Galaxies: Indicators of Cooling Flows Joel N. Bregman – University of Michigan Eric D. Miller – MIT Alex E. Athey – Carnegie Institution of Washington Jimmy A. Irwin – University of Michigan Deposited 09/13/2018 Citation of published version: Bregman, J., Miller, E., Athey, A., Irwin, J. (2005): O VI In Elliptical Galaxies: Indicators of Cooling Flows The Astrophysical Journal, 635(2). DOI: 10.1086/497421 © 2005. The American Astronomical Society. All rights reserved. Printed in U.S.A. The Astrophysical Journal, 635:1031–1043, 2005 December 20 # 2005. The American Astronomical Society. All rights reserved. Printed in U.S.A. O vi IN ELLIPTICAL GALAXIES: INDICATORS OF COOLING FLOWS Joel N. Bregman Department of Astronomy, University of Michigan, Ann Arbor, MI 48109; [email protected] Eric D. Miller Kavli Institute for Astrophysics and Space Science, MIT, Cambridge, MA 02139; [email protected] Alex E. Athey The Observatories, Carnegie Institution of Washington, Pasadena, CA 91101; [email protected] and Jimmy A. Irwin Department of Astronomy, University of Michigan, Ann Arbor, MI 48109; [email protected] Received 2005 April 25; accepted 2005 August 23 ABSTRACT Early-type galaxies often contain a hot X-ray–emitting interstellar medium [(3 8) ; 106 K] with an apparent radiative cooling time much less than a Hubble time. If unopposed by a heating mechanism, the gas will radiatively 4 À1 cool to temperatures P10 K at a rate proportional to LX /TX , typically 0.03–1 M yr . We can test whether gas is cooling through the 3 ; 105 K range by observing the O vi doublet, whose luminosity is proportional to the cooling rate. -
X-Ray Luminosities for a Magnitude-Limited Sample of Early-Type Galaxies from the ROSAT All-Sky Survey
Mon. Not. R. Astron. Soc. 302, 209±221 (1999) X-ray luminosities for a magnitude-limited sample of early-type galaxies from the ROSAT All-Sky Survey J. Beuing,1* S. DoÈbereiner,2 H. BoÈhringer2 and R. Bender1 1UniversitaÈts-Sternwarte MuÈnchen, Scheinerstrasse 1, D-81679 MuÈnchen, Germany 2Max-Planck-Institut fuÈr Extraterrestrische Physik, D-85740 Garching bei MuÈnchen, Germany Accepted 1998 August 3. Received 1998 June 1; in original form 1997 December 30 Downloaded from https://academic.oup.com/mnras/article/302/2/209/968033 by guest on 30 September 2021 ABSTRACT For a magnitude-limited optical sample (BT # 13:5 mag) of early-type galaxies, we have derived X-ray luminosities from the ROSATAll-Sky Survey. The results are 101 detections and 192 useful upper limits in the range from 1036 to 1044 erg s1. For most of the galaxies no X-ray data have been available until now. On the basis of this sample with its full sky coverage, we ®nd no galaxy with an unusually low ¯ux from discrete emitters. Below log LB < 9:2L( the X-ray emission is compatible with being entirely due to discrete sources. Above log LB < 11:2L( no galaxy with only discrete emission is found. We further con®rm earlier ®ndings that Lx is strongly correlated with LB. Over the entire data range the slope is found to be 2:23 60:12. We also ®nd a luminosity dependence of this correlation. Below 1 log Lx 40:5 erg s it is consistent with a slope of 1, as expected from discrete emission.