The FIRST STARS in the UNIVERSE WERE TYPICALLY MANY TIMES More Massive and Luminous Than the Sun
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A Multimessenger View of Galaxies and Quasars from Now to Mid-Century M
A multimessenger view of galaxies and quasars from now to mid-century M. D’Onofrio 1;∗, P. Marziani 2;∗ 1 Department of Physics & Astronomy, University of Padova, Padova, Italia 2 National Institute for Astrophysics (INAF), Padua Astronomical Observatory, Italy Correspondence*: Mauro D’Onofrio [email protected] ABSTRACT In the next 30 years, a new generation of space and ground-based telescopes will permit to obtain multi-frequency observations of faint sources and, for the first time in human history, to achieve a deep, almost synoptical monitoring of the whole sky. Gravitational wave observatories will detect a Universe of unseen black holes in the merging process over a broad spectrum of mass. Computing facilities will permit new high-resolution simulations with a deeper physical analysis of the main phenomena occurring at different scales. Given these development lines, we first sketch a panorama of the main instrumental developments expected in the next thirty years, dealing not only with electromagnetic radiation, but also from a multi-messenger perspective that includes gravitational waves, neutrinos, and cosmic rays. We then present how the new instrumentation will make it possible to foster advances in our present understanding of galaxies and quasars. We focus on selected scientific themes that are hotly debated today, in some cases advancing conjectures on the solution of major problems that may become solved in the next 30 years. Keywords: galaxy evolution – quasars – cosmology – supermassive black holes – black hole physics 1 INTRODUCTION: TOWARD MULTIMESSENGER ASTRONOMY The development of astronomy in the second half of the XXth century followed two major lines of improvement: the increase in light gathering power (i.e., the ability to detect fainter objects), and the extension of the frequency domain in the electromagnetic spectrum beyond the traditional optical domain. -
An Overview of New Worlds, New Horizons in Astronomy and Astrophysics About the National Academies
2020 VISION An Overview of New Worlds, New Horizons in Astronomy and Astrophysics About the National Academies The National Academies—comprising the National Academy of Sciences, the National Academy of Engineering, the Institute of Medicine, and the National Research Council—work together to enlist the nation’s top scientists, engineers, health professionals, and other experts to study specific issues in science, technology, and medicine that underlie many questions of national importance. The results of their deliberations have inspired some of the nation’s most significant and lasting efforts to improve the health, education, and welfare of the United States and have provided independent advice on issues that affect people’s lives worldwide. To learn more about the Academies’ activities, check the website at www.nationalacademies.org. Copyright 2011 by the National Academy of Sciences. All rights reserved. Printed in the United States of America This study was supported by Contract NNX08AN97G between the National Academy of Sciences and the National Aeronautics and Space Administration, Contract AST-0743899 between the National Academy of Sciences and the National Science Foundation, and Contract DE-FG02-08ER41542 between the National Academy of Sciences and the U.S. Department of Energy. Support for this study was also provided by the Vesto Slipher Fund. Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the authors and do not necessarily reflect the views of the agencies that provided support for the project. 2020 VISION An Overview of New Worlds, New Horizons in Astronomy and Astrophysics Committee for a Decadal Survey of Astronomy and Astrophysics ROGER D. -
Exors and the Stellar Birthline Mackenzie S
A&A 600, A133 (2017) Astronomy DOI: 10.1051/0004-6361/201630196 & c ESO 2017 Astrophysics EXors and the stellar birthline Mackenzie S. L. Moody1 and Steven W. Stahler2 1 Department of Astrophysical Sciences, Princeton University, Princeton, NJ 08544, USA e-mail: [email protected] 2 Astronomy Department, University of California, Berkeley, CA 94720, USA e-mail: [email protected] Received 6 December 2016 / Accepted 23 February 2017 ABSTRACT We assess the evolutionary status of EXors. These low-mass, pre-main-sequence stars repeatedly undergo sharp luminosity increases, each a year or so in duration. We place into the HR diagram all EXors that have documented quiescent luminosities and effective temperatures, and thus determine their masses and ages. Two alternate sets of pre-main-sequence tracks are used, and yield similar results. Roughly half of EXors are embedded objects, i.e., they appear observationally as Class I or flat-spectrum infrared sources. We find that these are relatively young and are located close to the stellar birthline in the HR diagram. Optically visible EXors, on the other hand, are situated well below the birthline. They have ages of several Myr, typical of classical T Tauri stars. Judging from the limited data at hand, we find no evidence that binarity companions trigger EXor eruptions; this issue merits further investigation. We draw several general conclusions. First, repetitive luminosity outbursts do not occur in all pre-main-sequence stars, and are not in themselves a sign of extreme youth. They persist, along with other signs of activity, in a relatively small subset of these objects. -
Star Formation in the “Gulf of Mexico”
A&A 528, A125 (2011) Astronomy DOI: 10.1051/0004-6361/200912671 & c ESO 2011 Astrophysics Star formation in the “Gulf of Mexico” T. Armond1,, B. Reipurth2,J.Bally3, and C. Aspin2, 1 SOAR Telescope, Casilla 603, La Serena, Chile e-mail: [email protected] 2 Institute for Astronomy, University of Hawaii at Manoa, 640 N. Aohoku Place, Hilo, HI 96720, USA e-mail: [reipurth;caa]@ifa.hawaii.edu 3 Center for Astrophysics and Space Astronomy, University of Colorado, Boulder, CO 80309, USA e-mail: [email protected] Received 9 June 2009 / Accepted 6 February 2011 ABSTRACT We present an optical/infrared study of the dense molecular cloud, L935, dubbed “The Gulf of Mexico”, which separates the North America and the Pelican nebulae, and we demonstrate that this area is a very active star forming region. A wide-field imaging study with interference filters has revealed 35 new Herbig-Haro objects in the Gulf of Mexico. A grism survey has identified 41 Hα emission- line stars, 30 of them new. A small cluster of partly embedded pre-main sequence stars is located around the known LkHα 185-189 group of stars, which includes the recently erupting FUor HBC 722. Key words. Herbig-Haro objects – stars: formation 1. Introduction In a grism survey of the W80 region, Herbig (1958) detected a population of Hα emission-line stars, LkHα 131–195, mostly The North America nebula (NGC 7000) and the adjacent Pelican T Tauri stars, including the little group LkHα 185 to 189 located nebula (IC 5070), both well known for the characteristic shapes within the dark lane of the Gulf of Mexico, thus demonstrating that have given rise to their names, are part of the single large that low-mass star formation has recently taken place here. -
SXP 1062, a Young Be X-Ray Binary Pulsar with Long Spin Period⋆
A&A 537, L1 (2012) Astronomy DOI: 10.1051/0004-6361/201118369 & c ESO 2012 Astrophysics Letter to the Editor SXP 1062, a young Be X-ray binary pulsar with long spin period Implications for the neutron star birth spin F. Haberl1, R. Sturm1, M. D. Filipovic´2,W.Pietsch1, and E. J. Crawford2 1 Max-Planck-Institut für extraterrestrische Physik, Giessenbachstraße, 85748 Garching, Germany e-mail: [email protected] 2 University of Western Sydney, Locked Bag 1797, Penrith South DC, NSW1797, Australia Received 31 October 2011 / Accepted 1 December 2011 ABSTRACT Context. The Small Magellanic Cloud (SMC) is ideally suited to investigating the recent star formation history from X-ray source population studies. It harbours a large number of Be/X-ray binaries (Be stars with an accreting neutron star as companion), and the supernova remnants can be easily resolved with imaging X-ray instruments. Aims. We search for new supernova remnants in the SMC and in particular for composite remnants with a central X-ray source. Methods. We study the morphology of newly found candidate supernova remnants using radio, optical and X-ray images and inves- tigate their X-ray spectra. Results. Here we report on the discovery of the new supernova remnant around the recently discovered Be/X-ray binary pulsar CXO J012745.97−733256.5 = SXP 1062 in radio and X-ray images. The Be/X-ray binary system is found near the centre of the supernova remnant, which is located at the outer edge of the eastern wing of the SMC. The remnant is oxygen-rich, indicating that it developed from a type Ib event. -
The Birth and Evolution of Brown Dwarfs
The Birth and Evolution of Brown Dwarfs Tutorial for the CSPF, or should it be CSSF (Center for Stellar and Substellar Formation)? Eduardo L. Martin, IfA Outline • Basic definitions • Scenarios of Brown Dwarf Formation • Brown Dwarfs in Star Formation Regions • Brown Dwarfs around Stars and Brown Dwarfs • Final Remarks KumarKumar 1963; 1963; D’Antona D’Antona & & Mazzitelli Mazzitelli 1995; 1995; Stevenson Stevenson 1991, 1991, Chabrier Chabrier & & Baraffe Baraffe 2000 2000 Mass • A brown dwarf is defined primarily by its mass, irrespective of how it forms. • The low-mass limit of a star, and the high-mass limit of a brown dwarf, correspond to the minimum mass for stable Hydrogen burning. • The HBMM depends on chemical composition and rotation. For solar abundances and no rotation the HBMM=0.075MSun=79MJupiter. • The lower limit of a brown dwarf mass could be at the DBMM=0.012MSun=13MJupiter. SaumonSaumon et et al. al. 1996 1996 Central Temperature • The central temperature of brown dwarfs ceases to increase when electron degeneracy becomes dominant. Further contraction induces cooling rather than heating. • The LiBMM is at 0.06MSun • Brown dwarfs can have unstable nuclear reactions. Radius • The radii of brown dwarfs is dominated by the EOS (classical ionic Coulomb pressure + partial degeneracy of e-). • The mass-radius relationship is smooth -1/8 R=R0m . • Brown dwarfs and planets have similar sizes. Thermal Properties • Arrows indicate H2 formation near the atmosphere. Molecular recombination favors convective instability. • Brown dwarfs are ultracool, fully convective, objects. • The temperatures of brown dwarfs can overlap with those of stars and planets. Density • Brown dwarfs and planets (substellar-mass objects) become denser and cooler with time, when degeneracy dominates. -
Chapter 1 a Theoretical and Observational Overview of Brown
Chapter 1 A theoretical and observational overview of brown dwarfs Stars are large spheres of gas composed of 73 % of hydrogen in mass, 25 % of helium, and about 2 % of metals, elements with atomic number larger than two like oxygen, nitrogen, carbon or iron. The core temperature and pressure are high enough to convert hydrogen into helium by the proton-proton cycle of nuclear reaction yielding sufficient energy to prevent the star from gravitational collapse. The increased number of helium atoms yields a decrease of the central pressure and temperature. The inner region is thus compressed under the gravitational pressure which dominates the nuclear pressure. This increase in density generates higher temperatures, making nuclear reactions more efficient. The consequence of this feedback cycle is that a star such as the Sun spend most of its lifetime on the main-sequence. The most important parameter of a star is its mass because it determines its luminosity, ef- fective temperature, radius, and lifetime. The distribution of stars with mass, known as the Initial Mass Function (hereafter IMF), is therefore of prime importance to understand star formation pro- cesses, including the conversion of interstellar matter into stars and back again. A major issue regarding the IMF concerns its universality, i.e. whether the IMF is constant in time, place, and metallicity. When a solar-metallicity star reaches a mass below 0.072 M ¡ (Baraffe et al. 1998), the core temperature and pressure are too low to burn hydrogen stably. Objects below this mass were originally termed “black dwarfs” because the low-luminosity would hamper their detection (Ku- mar 1963). -
The UV Perspective of Low-Mass Star Formation
galaxies Review The UV Perspective of Low-Mass Star Formation P. Christian Schneider 1,* , H. Moritz Günther 2 and Kevin France 3 1 Hamburger Sternwarte, University of Hamburg, 21029 Hamburg, Germany 2 Massachusetts Institute of Technology, Kavli Institute for Astrophysics and Space Research; Cambridge, MA 02109, USA; [email protected] 3 Department of Astrophysical and Planetary Sciences Laboratory for Atmospheric and Space Physics, University of Colorado, Denver, CO 80203, USA; [email protected] * Correspondence: [email protected] Received: 16 January 2020; Accepted: 29 February 2020; Published: 21 March 2020 Abstract: The formation of low-mass (M? . 2 M ) stars in molecular clouds involves accretion disks and jets, which are of broad astrophysical interest. Accreting stars represent the closest examples of these phenomena. Star and planet formation are also intimately connected, setting the starting point for planetary systems like our own. The ultraviolet (UV) spectral range is particularly suited for studying star formation, because virtually all relevant processes radiate at temperatures associated with UV emission processes or have strong observational signatures in the UV range. In this review, we describe how UV observations provide unique diagnostics for the accretion process, the physical properties of the protoplanetary disk, and jets and outflows. Keywords: star formation; ultraviolet; low-mass stars 1. Introduction Stars form in molecular clouds. When these clouds fragment, localized cloud regions collapse into groups of protostars. Stars with final masses between 0.08 M and 2 M , broadly the progenitors of Sun-like stars, start as cores deeply embedded in a dusty envelope, where they can be seen only in the sub-mm and far-IR spectral windows (so-called class 0 sources). -
3 Star and Planet Formation
3 Star and planet formation Part I: Star formation Abstract: All galaxies with a significant mass fraction of molecular gas show continuous formation of new stars. To form stars out of molecular clouds the physical properties of the gas have to change dramatically. Star formation is therefore all about: Initiating the collapse (Jeans criterion, demagnetization by ambipolar diffusion, external triggering) Compression of the gas by self-gravity Losing angular momentum (magnetic braking and fragmentation) 3.1 Criteria for gravitational collapse The basic idea to cause a molecular cloud to collapse due to its own gravity is to just make it massive enough, but the details are quite tricky. We look first at the Jeans criterion that gives the order of magnitude mass necessary for gravitational collapse. Then we consider the influence of a magnetic field before we discuss mechanisms for triggering a collapse by external forces. Jeans criterion (Sir James Jeans, 1877–1946): Let us consider the Virial theorem 20EEkin pot It describes the (time-averaged) state of a stable, gravitationally bound (and ergodic) system. Collins (1978) wrote a wonderful book on the Virial theorem including its derivation and applications in astrophysics, which has also been made available online (http://ads.harvard.edu/books/1978vtsa.book/). The Virial theorem applies to a variety of astrophysical objects including self-gravitating gas clouds, stars, planetary systems, stars in galaxies, and clusters of galaxies. Basically it describes the equilibrium situation of a gas for which pressure and gravitational forces are in balance. Depending on the values of kinetic and potential energies the following behavior results: Astrobiology: 3 Star and planet formation S.V. -
15.1 Galaxy Formation: Introduction
15.1 Galaxy Formation: Introduction Galaxy Formation • The early stages of galaxy evolution - but there is no clear-cut boundary, and it also has two principal aspects: assembly of the mass, and conversion of gas into stars • Must be related to large-scale (hierarchical) structure formation, plus the dissipative processes - it is a very messy process, much more complicated than LSS formation and growth • Probably closely related to the formation of the massive central black holes as well • Generally, we think of massive galaxy formation at high redshifts (z ~ 3 - 10, say); dwarfs may be still forming now • Observations have found populations of what must be young galaxies (ages < 1 Gyr), ostensibly progenitors of large galaxies today, at z ~ 5 - 7 • The frontier is now at z ~ 7 - 20, the so-called Reionization Era 2 A General Outline • The smallest scale density fluctuations keep collapsing, with baryons falling into the potential wells dominated by the dark matter, achieving high densties through cooling – This process starts right after the recombination at z ~ 1100 • Once the gas densities are high enough, star formation ignites – This probably happens around z ~ 20 - 30 – By z ~ 6, UV radiation from young galaxies reionizes the unverse • These protogalactic fragments keep merging, forming larger objects in a hierarchical fashion ever since then • Star formation enriches the gas, and some of it is expelled in the intergalactic medium, while more gas keeps falling in • If a central massive black hole forms, the energy release from accretion -
Second Parameter Globulars and Dwarf Spheroidals Around the Local Group Massive Galaxies: What Can They Evidence?
A&A 396, 117–123 (2002) Astronomy DOI: 10.1051/0004-6361:20021404 & c ESO 2002 Astrophysics Second parameter globulars and dwarf spheroidals around the Local Group massive galaxies: What can they evidence? V. K ravtsov Sternberg Astronomical Institute, University Avenue 13, 119899 Moscow, Russia Received 29 April 2002 / Accepted 28 August 2002 Abstract. We suggest that the majority of the “young”, so–called “second parameter” globular clusters (SPGCs) have origi- nated in the outer Galactic halo due to a process other than a tidal disruption of the dwarf spheroidal (dSph) galaxies. Basic observational evidence regarding both the dSphs and the SPGCs, coupled with the latest data about a rather large relative num- ber of such clusters among globulars in M 33 and their low portion in M 31, seems to be consistent with the suspected process. It might have taken place within the system of the most massive galaxies of the Local Group (LG) at the earliest stages of their formation and evolution. We argue that the origin and basic characteristics of the SPGCs can naturally be explained as a result of mass outflow from M 31, during and due to formation of its Pop. II stars, and subsequent accretion of gas onto its massive companions, the Galaxy and M 33. An amount of the gas accreted onto the Milky Way is expected to have been quite enough for the formation in the outer Galactic halo not only of the clusters under consideration but also a number of those dSph galaxies which are as young as the SPGCs. A less significant, but notable mass transfer from the starbursting protoGalaxy to the massive members of the LG might have occurred, too. -
Open Thesis10.Pdf
The Pennsylvania State University The Graduate School The Eberly College of Science POPULATION SYNTHESIS AND ITS CONNECTION TO ASTRONOMICAL OBSERVABLES A Thesis in Astronomy and Astrophysics Michael S. Sipior c 2003 Michael S. Sipior Submitted in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy May 2003 We approve the thesis of Michael S. Sipior Date of Signature Michael Eracleous Assistant Professor of Astronomy and Astrophysics Thesis Advisor Chair of Committee Steinn Sigurdsson Assistant Professor of Astronomy and Astrophysics Gordon P. Garmire Evan Pugh Professor of Astronomy and Astrophysics W. Niel Brandt Associate Professor of Astronomy and Astrophysics L. Samuel Finn Professor of Physics Peter I. M´esz´aros Distinguished Professor of Astronomy and Astrophysics Head of the Department of Astronomy and Astrophysics Abstract In this thesis, I present a model used for binary population synthesis, and 8 use it to simulate a starburst of 2 10 M over a duration of 20 Myr. This × population reaches a maximum 2{10 keV luminosity of 4 1040 erg s−1, ∼ × attained at the end of the star formation episode, and sustained for a pe- riod of several hundreds of Myr by succeeding populations of XRBs with lighter companion stars. An important property of these results is the min- imal dependence on poorly-constrained values of the initial mass function (IMF) and the average mass ratio between accreting and donating stars in XRBs. The peak X-ray luminosity is shown to be consistent with recent observationally-motivated correlations between the star formation rate and total hard (2{10 keV) X-ray luminosity.