DOCSLIB.ORG

Surveys for Planetary Nebulae in the Magellanic Clouds

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Surveys for Planetary Nebulae in the Magellanic Clouds Surveys for Planetary Nebulae in the Magellanic Clouds SMC LMC Where we simultaneously study stellar and galaxy evolution ESO Workshop: May 19-21, 2004 Orientation The View from Cerro Tololo SMC MW LMC ESO Workshop: May 19-21, 2004 Relationship to MW HI map from Putnam et al (2003) Magellanic Stream extends >90° across sky, but has few stars Distances: accurate to ±10% 50 kpc to LMC* 62 kpc to SMC *depth within LMC ±3% ESO Workshop: May 19-21, 2004 Extent of LMC: van de Marel 2001 SMP 78 24° 22° RGB and AGB counts indicate the LMC subtends ~130 sq. deg. ESO Workshop: May 19-21, 2004 Common Survey Techniques To identify PN candidates via – Direct imaging through filters (on-band and off-band) – Objective prism imaging (historically photographic) – Spectral “imaging” (PN Spectrograph) Other kinds of surveys – Follow-up High resolution imaging (HST, AO systems) – Follow-up spectroscopy • Candidate verification • Chemical composition • Central star atmospheric properties • Kinematic probe of host galaxy properties: dark matter? • Kinematic probe of nebula itself: expansion properties ESO Workshop: May 19-21, 2004 “Modern” SMC Surveys Survey Team Number Number Depth, Found New mags SMP 1978 28 3 3 Jacoby 1980 27 19 5 Sanduleak & Pesch 1981 6 6 3 Morgan & Good 1985 13 10 3 Meyssonnier & Azzopardi 93 62 18 4 Morgan 1995 62 9 3 Murphy & Bessel 2000 131 108 ? Jacoby & De Marco 2002 59 25 6 Galle, Winkler, & Smith* 69 13 4? Jacoby & De Marco 15 4 7 Magellanic Cloud Emission Line Survey * ESO Workshop: May 19-21, 2004 Technology Helps The Clouds are easy targets with large format CCD mosaic cameras on large telescopes ESO 2.2m CTIO 4m Example: MB 233 – but, probably not a PN CTIO 4m extends ~1 mag beyond ESO 2.2m ESO Workshop: May 19-21, 2004 SMC Completeness Most Recent Surveys 2+1 +1 3 Jacoby & De Marco (2002) • 10 fields of 0.5° each (2.2M) 2 5 6 2 +2 • Depth of ~6 mags 5 12 7 Jacoby & De Marco (in prep) • 6 fields, 3 new PN (CTIO 4m) 4 7 8 • Depth of ~7 mags • Not very productive more depth doesn’t help outer fields have few PN ESO Workshop: May 19-21, 2004 “Modern” LMC Surveys Survey Team Number Number Depth, Found New mags SMP 1978 28 3 3 Jacoby 1980 27 19 5 Sanduleak 1984 25 13 3 Morgan & Good 1992 98 86 5 Morgan 1994 265 54 5 Leisy, Francois, & Fouqué 10 4 9 Jacoby & De Marco 15 10 7 Reid & Parker ~1000* 136 7? *Candidates to be verified ESO Workshop: May 19-21, 2004 “Modern” LMC Surveys The pioneering surveys by Henize (1956), Lindsay (1961), Henize & Westerlund (1963), Lindsay & Mullan (1965), and Westerlund & Smith (1964) defined the extragalactic PN field. Survey Team Number Number Depth, Found New mags SMP 1978 28 3 3 Jacoby 1980 27 19 5 Sanduleak 1984 25 13 3 Morgan & Good 1992 98 86 5 Morgan 1994 265 54 5 Leisy, Francois, & Fouqué 10 4 9 Jacoby & De Marco 15 10 7 Reid & Parker ~1000* 136 7? Candidates to be verified * ESO Workshop: May 19-21, 2004 LMC Completeness Most Recent Surveys Reid & Parker (in prep) • 25 sq.deg.; 1000 candidates • Photographic Hα stacked Leisy et al (in prep) • Many fields & new PN (2.2m) Jacoby & De Marco (in prep) 5+10 • 1 field, 10 new PN (4m) • Depth of ~7 mags ESO Workshop: May 19-21, 2004 The Clouds are a Special Place Nearest (by 10X) large population of EG PN (50-70 kpc) – Distances known: 50 and 62 kpc (common for each sample) – Faintest PN are observable (unbiased statistical sample) – Central stars can be studied directly (photometry, spectra) • Masses for low-metallicity initial-to-final mass relation • Identify binaries via velocity variations – PN are easily resolved: from space or with AO facilities • Morphology • Physical radii allow expansion ages to be measured – High S/N spectroscopy allows studies for • Compositional analysis across full luminosity range • Internal dynamics Large samples: hundreds of PN can be studied Low/Intermediate metallicity sample ESO Workshop: May 19-21, 2004 Challenges for MC PN Surveys Contaminants in surveys – Compact HII regions, especially if low surface brightness – Novae (2 “PN” in SMC, 1 in LMC) – Background emission-line galaxies Faint nebulae are extended detection shifts from point source domain to surface brightness problem Very large area on sky – SMC: ~ 20 sq. deg. – LMC: ~130 sq. deg. ESO Workshop: May 19-21, 2004 Challenges for MC PN Surveys Confirmation and follow-up spectroscopy compromised by – Crowding from stars – Diffuse HII emission Nomenclature (Parker, Cibis) – Surveys began without naming convention – We have near-chaos today Accurate coordinates – objects may be extended 5-10 arcsec ESO Workshop: May 19-21, 2004 Galaxy Cluster Behind SMC Field 11 [OIII] Diff HST image of MA 1682 ESO Workshop: May 19-21, 2004 Spectroscopy is Complicated CTIO 4m spectrum of JD-17: Hα+[NII]+[SII] region Raw Sky subtracted Issues remain: • Incomplete subtraction from diffuse HII emission • Stellar spectra from background • Nebula resolves, so some flux falls off slit • Faintest PN will be lost in the stellar continuua • But, see Roth for instrumental solution ESO Workshop: May 19-21, 2004 SMC Luminosity Function Survey extends 8 mags down PNLF Dip seen in PNLF for first time Absent in models, generally Possibilities (Marigo/Girardi models) – Progenitors from multiple ages Hints from M33 (<1 and 8-10 Gyr) Age?, metallicity?, IMF? – Binary stars in old pops (common envelope evolution) ESO Workshop: May 19-21, 2004 How Many PN are There? Technically feasible to survey the SMC and LMC to the faintest PN and find them all, rather than extrapolate A “Complete” survey is “defined” to go 8 mags down LF SMC surveys are largely complete to ~7 mags 1.5X more LMC surveys are largely complete to 5 mags 3X more Currently known, entire SMC 84 With deeper survey (8 mags) 120-170 Currently known, entire LMC 350* With deeper survey (8 mags) 800-900 *sample is neither homogeneous in depth nor spatially complete; Reid and Parker survey will improve statistics significantly. ESO Workshop: May 19-21, 2004 Questions That MC PN Can Answer How many PN are in the Clouds, how do the counts compare to galaxy evolution models, & what are inferences for other galaxies? – Tests stellar and galaxy evolution theory, population mixes – Need to complete the surveys – Need follow-up spectra to confirm candidates What fraction of PN have binary CS? Maybe all of them ??? – De Marco et al (2004) – 11/12 Galactic PN are velocity variables – Need synoptic spectroscopy of PN CS at moderate resolution Velocities of Cloud PN can be accurate to 1 km/s – with forthcoming large samples, can we map the dark matter? – Need spectroscopy of nebulae at moderate resolution – Need kinematic models of the SMC and LMC (with GCs, HII, stellar velocities) ESO Workshop: May 19-21, 2004 Questions That MC PN Can Answer What is the distribution of central star masses, and what is the initial-to-final mass relation as a function of metallicity? – Need medium resolution spectroscopy of central star and nebula Do the brightest PN have the characteristics (CS mass, T*, L*, nebular age/size) predicted by PNLF models (e.g., Marigo et al) – Need specific model predictions – Need statistically complete HST (or ground AO) measurements of nebula (plus above bullet) ESO Workshop: May 19-21, 2004 Astrophysics from Cloud PN at this conference Stanghellini – HST observations of ~half the Cloud PN allow morphology of many PN to be studied in absolute terms (radius, age, shape, kinematics) to link to their progenitor stars Villaver, Arrieta – MV, T*, L*, mass, composition now can be measured directly for many central stars (from spectra) IFMR Shaw – 100 LMC & 30 SMC PN with HST imaging allow correlations of physical properties to explore formation and evolutionary processes of PN that are not possible elsewhere Reid – complete surveys are possible to faintest PN for accurate counts, PN birth rates, tests of stellar evolution models Maciel – Composition correlations in SMC, LMC, and MW Peña – Detailed study of N66 in LMC Tsammis – Recombination and forbidden line analysis in SMC ESO Workshop: May 19-21, 2004 Conclusions Easy to find many PN in Clouds with current methods – this is the only large sample where all PN can be found! – SMC surveys are approaching completeness – LMC surveys could be complete soon (Reid & Parker, Leisy et al) Deficit at 2-4 mags in PNLF is a clue to stellar population content – need models that interpret this feature! Compare in LMC. Almost any kind of PN study can be done better in the Clouds (distances known, spatially resolved, relatively bright) ☺ Confrontation of observations and theory (Ciardullo/Girardi talks) may be solved, in part, with observations of Cloud PN – Models predict properties of bright PN and CS – test them! – Cloud PN derive from a range of metallicities and progenitor ages, the principal parameters driving the model PNLF cut-off ESO Workshop: May 19-21, 2004 END I have never in my life learned anything from anyone who agreed with me. Dudley Field Malone ESO Workshop: May 19-21, 2004 Stellar Abundances in the SMC Stars in SMC are diverse (Larson, Clausen, Storm 2000) From Stromgren photometry of fields stars in SMC ESO Workshop: May 19-21, 2004 Are Faint PN Different From Bright PN? Consider SMC … 1 (5.5% of 18) of SMP PN have [NII]/Hα > 1 7 (28% of 25) new Jacoby & De Marco PN have strong [NII] Fraction of PN with [NII]/Hα > 1, in bright (<2 mags) and intermediate (<6 mags) luminosity groups – LMC ratio = 1.9 (16% vs 31%) – SMC ratio = 4.3 (6% vs 26%) Type I PN in SMC are preferentially faint • They generate more dust (Ciardullo & Jacoby 1999) • Their central stars are massive and fade fast ESO Workshop: May 19-21, 2004 [NII]/Hα Ratios: PN 1 – 9 11 4 7 11 2 5 8 3 6 9 ESO Workshop: May 19-21, 2004 [NII]/Hα Ratios: JD 10 – 18 10 13 16 11 14 17 12 15 18 ESO Workshop: May 19-21, 2004 [NII]/Hα Ratios: PN 19 – 25 19 22 25 20 23 Nova 21 24 ESO Workshop: May 19-21, 2004.
Load more

Recommended publications
  • A New View of Supernova Remnants in the L\:Fagellanic Clouds from David Clark
    690 Nature Vol. 294 24/31 December 1981 Finally, whatofTRF4? Aftermanyyears functions early (proliferative phase). The given by a current report describing a start of difficulty, created in part by the ability relationship to the newly described B cell on molecular biological studies of IL2. of factors like IL2 and the B cell growth growth factor awaits further experiments. Given several T cell tumour lines which can factor to replace T cells indirectly, assays In both cases, a clearer understanding of be induced to generate high levels of IL2 which clearly distinguish between IL2 and the roles of several lymphokines now (several thousand times the amounts pro­ TRF are now in hand. And the take-home exists, and perhaps more important, the duced by normal lymphocytes), it has been message is that, indeed, TRF exists12 • It tools and approaches necessary for more possible to follow the lead of workers in the acts at the time when B cells, having sophisticated analysis are evident. interferon field, by looking for mRNA undergone clonal expansion following An indication of future directions is coding for the lymphokine, and then antigenic stimulation, are to begin attempting to clone its complementary secreting high levels of immunoglobulin. I. OiSabato, G .• Chen, 0.-M. & Erickson . .1.W. Cell. DNA. The EL4 variant cell line originally Then, as proposed years ago by Dutton and lmmun. 17,495 (1975). described by Farrar and colleagues at 2. Gillis. S. & Smith, K.A. Nature 268, 154 (1977). 13 colleagues, TRF can replace T cells in ). Ruscetti, F.W., Morgan, D.A. & Gallo, R.C.
    [Show full text]
  • Large Magellanic Cloud, One of Our Busy Galactic Neighbors
    The Large Magellanic Cloud, One of Our Busy Galactic Neighbors www.nasa.gov Our Busy Galactic Neighbors also contain fewer metals or elements heavier than hydrogen and helium. Such an environment is thought to slow the growth The cold dust that builds blazing stars is revealed in this image of stars. Star formation in the universe peaked around 10 billion that combines infrared observations from the European Space years ago, even though galaxies contained lesser abundances Agency’s Herschel Space Observatory and NASA’s Spitzer of metallic dust. Previously, astronomers only had a general Space Telescope. The image maps the dust in the galaxy known sense of the rate of star formation in the Magellanic Clouds, as the Large Magellanic Cloud, which, with the Small Magellanic but the new images enable them to study the process in more Cloud, are the two closest sizable neighbors to our own Milky detail. Way Galaxy. Herschel is a European The Large Magellanic Cloud looks like a fiery, circular explosion Space Agency in the combined Herschel–Spitzer infrared data. Ribbons of dust cornerstone mission, ripple through the galaxy, with significant fields of star formation with science instruments noticeable in the center, center-left and top right. The brightest provided by consortia center-left region is called 30 Doradus, or the Tarantula Nebula, of European institutes for its appearance in visible light. and with important participation by NASA. NASA’s Herschel Project Office is based at NASA’s Jet Propulsion Laboratory, Pasadena, Calif. JPL contributed mission-enabling technology for two of Herschel’s three science instruments.
    [Show full text]
  • E+FW Abstract Book
    Elizabeth and Frederick White Conference on the Magellanic System SCIENTIFIC ORGANISING COMMITTEE Dr. Erik Muller ATNF, CSIRO Dr. Bärbel Koribalski ATNF, CSIRO Prof. Yasuo Fukui University of Nagoya Dr. Russell Cannon Anglo-Australian Observatory Prof. Lister Staveley-Smith Univeristy of Western Australia Dr. Kenji Bekki University of New South Wales LOCAL ORGANISING COMMITTEE Dr. Erik Muller ATNF, CSIRO Deanna Matthews La Trobe University / ATNF, CSIRO Vicki Fraser ATNF, CSIRO Miroslav Filipovic University of Western Sydney Elizabeth and Frederick White Conference on the Magellanic System PARTICIPANT LIST Bekki Kenji Univeristy of New South Wales Besla Gurtina Harvard-Smithsonian CfA Bland-Hawthorn Joss Anglo-Australian Observatory Bolatto Alberto UCB Bot Caroline California Institute of Technology Braun Robert Australia Telescope National Facility Brooks Kate Australia Telescope National Facility Cannon Russell Anglo-Australian Observatory Carlson Lynn Johns Hopkins University Cioni Maria-Rosa Institute for Astronomy, University of Edinburgh Da Costa Gary Research School of Astronomy & Astrophysics ANU Doi Yasuo University of Tokyo Ekers Ron Australia Telescope National Facility Filipovic Miroslav University of Western Sydney Fukui Yasuo Nagoya University Gaensler Bryan University of Sydney Harris Jason Steward Observatory Hitschfeld Marc University of Colgne Hughes Annie Centre for Astrophysics & Supercomputing, Swinburne University Hurley Jarrod Centre for Astrophysics & Supercomputing, Swinburne University Francisco Ibarra Javier
    [Show full text]
  • Galactic and Extragalactic Studies, Xxiii. Opacity of the Southern Milky Way Dust Clouds by Harlow Shapley and Jacqueline Sweeney
    GALACTIC AND EXTRAGALACTIC STUDIES, XXIII. OPACITY OF THE SOUTHERN MILKY WAY DUST CLOUDS BY HARLOW SHAPLEY AND JACQUELINE SWEENEY HARVARD COLLEGE OBSERVATORY Communicated June 3, 1955 The greater richness of the southern celestial hemisphere when compared with the northern is illustrated by its brightest constellations, Scorpius, Sagittarius, Centaurus, and Crux, and in such stellar giants of brightness and size as Sirius, Antares, Canopus, and Achernar. It is the hemisphere of the nearest external galaxies (the Magellanic Clouds) and of the central nucleus of our Milky Way. A consequence of the latter is that more than four-fifths of the known globular star clusters, including the two brightest, Omega Centauri and 47 Tucanae, are also southern, as is the heavily obscured Messier 4, probably the nearest of all globular clusters. But perhaps the most outstanding features of the southern sky are the brilliance of the gaseous nebulosities in Orion, Carina, and Sagittarius and the darkness of the large obscurations among the Milky Way star clouds, especially the darkness of the Coalsack and of the complex of obscurities around Rho Ophi- uchi. An examination of the opacity of these discrete dark nebulosities, and of the general cosmic dust that obscures the distant parts of the southern Milky Way, is reported in this communication. 1. On the basis of galaxy counts on photographs made with the Mount Wilson reflectors, E. P. Hubble published in 1934 his well-known picture of the distribution of faint galaxies. He was able to take his sampling survey southward only to dec- lination -30°. Hubble's work on northern galaxies is now being reinforced, or actually supplanted, by the full-coverage atlas of the northern sky by C.
    [Show full text]
  • A Synoptic View of the Magellanic Clouds: VMC, Gaia, and Beyond Held at ESO Headquarters, Garching, Germany, 9–13 September 2019
    Astronomical News DOI: 10.18727/0722-6691/5211 Report on the ESO Workshop A Synoptic View of the Magellanic Clouds: VMC, Gaia, and Beyond held at ESO Headquarters, Garching, Germany, 9–13 September 2019 Maria-Rosa L. Cioni 1 In this workshop, the most interesting of the system and use stellar population Martino Romaniello 2 discoveries emerging from the VMC and diagnostics across the Hertzsprung- Richard I. Anderson 2 other contemporary multi-wavelength Russell diagram with unprecedented pre- surveys were discussed. These results cision. Most of these developments will have cemented stellar populations as culminate in the early 2020s and discus- 1 Leibniz-Institut für Astrophysik Potsdam important diagnostics of galaxy proper- sions on how to formulate the most rele- (AIP), Germany ties. Cepheid stars have, for example, vant scientific questions are already 2 ESO revealed the three-dimensional structure advanced. of the system, giant stars have shown significantly extended populations, and The year 2019 marked the quincente- blue horizontal branch stars have indi- Summaries of talks and highlights from nary of the arrival in the southern hemi- cated protuberances and possible sessions sphere of Ferdinand Magellan, the streams in the outskirts of the galaxies. namesake of the Magellanic Clouds, The complementary view provided by The workshop revolved around eight our nearest example of dwarf galaxies RR Lyrae stars shows instead regular and scientific sessions at which a total of in the early stages of a minor merging ellipsoidal systems. The analysis of the 64 talks were presented and a summary event. These galaxies have been firmly star formation history suggests that the is given below.
    [Show full text]
  • The Magellanic Stream As a Probe of Astrophysics
    Astro2020 Science White Paper The Magellanic Stream as a Probe of Astrophysics Thematic Areas: ☐ Planetary Systems ☐ Star and Planet Formation ☐Formation and Evolution of Compact Objects ☐ Cosmology and Fundamental Physics ☐Stars and Stellar Evolution ☐Resolved Stellar Populations and their Environments ☒Galaxy Evolution ☐Multi-Messenger Astronomy and Astrophysics Principal Author: Andrew J Fox, Space Telescope Science Institute, [email protected], 410 338 5083 Co-authors: Kathleen A. Barger, Texas Christian University, [email protected] Joss Bland-Hawthorn, University of Sydney, [email protected] Dana Casetti-Dinescu, Southern Connecticut State University, [email protected] Elena d’Onghia, University of Wisconsin-Madison, [email protected] Felix J. Lockman, Green Bank Observatory, [email protected] Naomi McClure-Griffiths, Australian National University, [email protected] David Nidever, University of Montana, [email protected] Mary Putman, Columbia University, [email protected] Philipp Richter, University of Potsdam, [email protected] Snezana Stanimirovic, University of Wisconsin-Madison, [email protected] Thorsten Tepper-Garcia, University of Sydney, [email protected] Abstract: Extending for over 200 degrees across the sky, the Magellanic Stream together with its Leading Arm is the most spectacular example of a gaseous stream in the local Universe. The Stream is an interwoven tail of filaments trailing the Magellanic Clouds as they orbit the Milky Way. Thought to be created by tidal forces, ram pressure, and halo interactions, the Stream is a benchmark for dynamical models of the Magellanic System, a case study for gas accretion and dwarf-galaxy accretion onto galaxies, a probe of the outer halo, and the bearer of more gas mass than all other Galactic high velocity clouds combined.
    [Show full text]
  • Model Nebulae and Determination of the Chemical Composition of the Magellanic Clouds (Gaseous Nebulae/Galaxies) L
    Proc. NatI. Acad. Sci. USA Vol. 76, No. 4, pp. 1525-1528, April 1979 Astronomy Model nebulae and determination of the chemical composition of the Magellanic Clouds (gaseous nebulae/galaxies) L. H. ALLER*, C. D. KEYES*, AND S. J. CZYZAKt *Department of Astronomy, University of California, Los Angeles, California 90024; and tDepartment of Astronomy, Ohio State University, Columbus, Ohio 43210 Contributed by Lawrence H. Aller, December 18, 1978 ABSTRACT An analysis of previously presented photo- exchange. One then calculates the radiation field, the changing electric spectrophotometry of HII regions (emission-line diffuse pattern of excitation and ionization, and emissivities in spectral nebulae) in the two Magellanic Clouds is carried out with the lines as a function of distance from the central star. The pro- aid of theoretical nebular models, which are used primarily as interpolation devices. Some advantages and limitations of such gram gives the spectral line emission integrated over the nebula, theoretical models are discussed. A comparison of the finally for each transition of interest; it also gives the fraction of atoms obtained chemical compositions with those found by other of each relevent element in each of its ionization stages. In- observers shows generally a good agreement, suggesting that tensities of forbidden lines depend not only on the ionic con- it is possible to obtain reliable chemical compositions from low centration but also on the electron temperature, which in turn excitation gaseous nebulae in our own galaxy as well as in dis- tant stellar is fixed by energy balance considerations (9). systems. Thus, one adjusts the available parameters-density distri- Diffuse gaseous nebulae, often called HII regions, are of con- bution, ultraviolet flux of radiation from the illuminating star, siderable value in studies of the chemical compositions of spiral and the chemical composition-in an effort to reproduce the and irregular galaxies.
    [Show full text]
  • Arxiv:1907.02264V2 [Astro-Ph.GA] 10 Jul 2019 Also Found in the Magellanic Bridge Area (Noel¨ Et Al
    Astronomy & Astrophysics manuscript no. aa c ESO 2019 July 12, 2019 On the nature of a shell of young stars in the outskirts of the Small Magellanic Cloud David Mart´ınez-Delgado1, A. Katherina Vivas2, Eva K. Grebel1, Carme Gallart3;4, Adriano Pieres5;6, Cameron P. M. Bell7, Paul Zivick8, Bertrand Lemasle1, L. Clifton Johnson9, Julio A. Carballo-Bello10;11, Noelia E. D. Noel¨ 12, Maria-Rosa L. Cioni7, Yumi Choi13;14, Gurtina Besla13, Judy Schmidt15, Dennis Zaritsky13, Robert A. Gruendl16;17, Mark Seibert18, David Nidever19, Laura Monteagudo3;4, Mateo Monelli3;4, Bernhard Hubl20, Roeland van der Marel21;22, Fernando J. Ballesteros23, Guy Stringfellow24, Alistair Walker2, Robert Blum19, Eric F. Bell25, Blair C. Conn26, Knut Olsen19, Nicolas Martin27;28, You-Hua Chu29;30, Laura Inno28, Thomas J. L. Boer12, Nitya Kallivayalil8, Michele De Leo12, Yuri Beletsky31, Ricardo R. Munoz˜ 32 (Affiliations can be found after the references) ABSTRACT Context. Understanding the evolutionary history of the Magellanic Clouds requires an in-depth exploration and characterization of the stellar content in their outer regions, which ultimately are key to tracing the epochs and nature of past interactions. Aims. We present new deep images of a shell-like over-density of stars in the outskirts of the Small Magellanic Cloud (SMC). The shell, also detected in photographic plates dating back to the fifties, is located at ∼ 1:9◦ from the center of the SMC in the north-east direction. Methods. The structure and stellar content of this feature were studied with multi-band, optical data from the Survey of the MAgellanic Stellar History (SMASH) carried out with the Dark Energy Camera on the Blanco Telescope at Cerro Tololo Inter-American Observatory.
    [Show full text]
  • 1992Apj. . .384. .508R the Astrophysical Journal, 384:508-522
    .508R The Astrophysical Journal, 384:508-522,1992 January 10 © 1992. The American Astronomical Society. All rights reserved. Printed in U.S.A. .384. 1992ApJ. ABUNDANCES OF THE HEAVY ELEMENTS IN THE MAGELLANIC CLOUDS. III. INTERPRETATION OF RESULTS Stephen C. Russell Dublin Institute for Advanced Studies, School of Cosmic Physics, 5 Merrion Square, Dublin 2, Ireland AND Michael A. Dopita Mount Stromlo and Siding Spring Observatories, Institute of Advanced Studies, The Australian National University, Private Bag, Weston Creek P.O., Canberra, ACT 2611, Australia Received 1990 June 4; accepted 1991 July 19 ABSTRACT This paper presents chemical and structural evolutionary models for the Magellanic Clouds assuming bi- modal star formation and gas infall. The models are discussed in relation to the observed chemical abun- dances of the Clouds and are compared with our own Galaxy. The detailed abundances derived from previous work are investigated for any obvious trends with metallicity or differences compared with the Galaxy. Con- sidering all the data, conclusions are drawn on the possible star formation histories of the Magellanic Clouds and the implications for our own Galaxy. The following conclusions were reached in this work. The interstellar medium (ISM) of the LMC has a mean metallicity 0.2 dex lower than the local Galactic ISM, and the metallicity of the SMC is 0.6 dex lower. However, the interstellar media of both the Magellanic Clouds and the Galaxy have significantly nonsolar elemental ratios. This is most evident when considering the lightest and the heaviest of the elements. The s-process appears to have been less effective at forming the heavy neutron-capture elements in the Magellanic Clouds than in the Galaxy.
    [Show full text]
  • A History of the Magellanic Clouds and the European Exploration of the Southern Hemisphere Michel Dennefeld1 1 Institut D'astr
    A History of the Magellanic Clouds and the European Exploration of the Southern Hemisphere Michel Dennefeld1 1 Institut d’Astrophysique de Paris (IAP), CNRS & Sorbonne Université, France The Magellanic Clouds were known before Magellan's voyage exactly 500 years ago, and were not given that name by Magellan himself or his chronicler Antonio Pigafetta. They were, of course, already known by local populations in South America, such as the Mapuche and Tupi-Guaranis. The Portuguese called them Clouds of the Cape, and scientific circles had long used the name of Nubecula Minor and Major. We trace how and when the name Magellanic Clouds came into common usage by following the history of exploration of the southern hemisphere and the southern sky by European explorers. While the name of Magellan was quickly associated to the Strait he discovered (within about 20 years only), the Clouds got their final scientific name only at the end of the 19th century, when scientists finally abandoned Latin as their communication language. This year we celebrate the 500th anniversary of the discovery of the navigable sea route that separates mainland South America from Tierra del Fuego — now known as the Strait of Magellan — by Fernão de Magalhães (Ferdinand Magellan in English) and his companions. It therefore seems an appropriate time to examine the “history” of the Magellanic Clouds, not least because the study of the Clouds was one of the main reasons for the foundation of astronomical observatories in Chile. Magellan’s expedition entered the strait at Cabo de las Virgenes on 21 October 1520 and exited via Cabo Deseado on 28 November.
    [Show full text]
  • The “Ugly Duckling”, in the Realm of the Galaxies
    The \ugly duckling", in the realm of the galaxies Domingos Soares The galaxies that most call our attention to are the spiral galaxies | es- pecially because of the beauty of the spiral arms | and the elliptical galaxies, which present an uniform and smooth light distribution against the sky back- ground. There is, though, a type of galaxy, whose attractiveness is precisely the fact of not presenting harmony or regularity on its shape. It is the \ugly duckling" of the realm of the galaxies, and the representatives of that type are called very appropriately \irregular galaxies". Irregular galaxies tend to be smaller than spirals and ellipticals and are even called \dwarf" galaxies. Actually, the term \irregular galaxy" is applied both to dwarf spiral galaxies, with disturbed structure, as our companion, the Large Magellanic Cloud, and to all other galaxies that do not fit on any of the types that have a regular structure. Incidentally, the Magellanic Clouds | the Large and the Small | are satellite galaxies of our Milky Way, being easily seen with the naked eye on the southern hemisphere skies. They were discovered by the Portuguese navigator Ferdinand Magellan (1480-1521), in 1520, when he undertook his Earth's circumnavigation voyage. When Edwin Hubble (1889-1953) put forward his classification scheme of galaxies | known as Hubble's tuning fork |, he simply classified all galaxies that did not fit on the types spiral and elliptical as \irregular". Presently, irregular themselves have an internal classification distinction, as we shall see. Now, Hubble called \Irr I" the irregular galaxies in which he could discern at least some sign of a structure, for example, indications of a spiral arm.
    [Show full text]
  • Distribution of the High-Velocity Clouds in the Galactic Halo
    A&A 485, 457–473 (2008) Astronomy DOI: 10.1051/0004-6361:20077556 & c ESO 2008 Astrophysics Distribution of the high-velocity clouds in the Galactic halo C. A. Olano? Universidad Nacional de La Plata, Facultad de Ciencias Astronómicas y Geofísicas, Paseo del Bosque, 1900 La Plata, Argentina e-mail: [email protected] Received 27 March 2007 / Accepted 19 March 2008 ABSTRACT Context. There is a connection between the kinematics and sky distribution of the high velocity clouds (HVCs) and the spatial velocity and orbital plane of the Magellanic Clouds (MCs) that allow us to conclude that most HVCs were ejected from the Clouds, some hundreds of Myrs ago, probably by an encounter between the Large (LMC) and Small Magellanic Cloud (SMC). Aims. Based on the idea that HVCs have progenitors in the MCs, we attempt determine theoretical distances to the HVCs using observed data of the sky positions and radial velocities, and thus to map the spatial distribution of the HVCs. Methods. i) In the context of a kinematical model we have found an analytical formula that gives the distance of an HVC; ii) we have developed two dynamical models in order to study the orbits of the HVCs under the gravitational forces exerted by the Galaxy and the MCs and forces of resistance due to the movement of the HVCs through the Galactic gaseous disk. We have adopted the gravitational potential of the Milky Way given by a dark matter halo (Model 1) plus a massive thick disk partially composed by dark matter (Model 2).
    [Show full text]