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The Tilt of the Velocity Ellipsoid in the Milky Way with Gaia DR2 Jorrit H
Astronomy & Astrophysics manuscript no. aa c ESO 2019 November 10, 2019 The tilt of the velocity ellipsoid in the Milky Way with Gaia DR2 Jorrit H. J. Hagen1, Amina Helmi1, P. Tim de Zeeuw2; 3, and Lorenzo Posti1 1 Kapteyn Astronomical Institute, University of Groningen, Landleven 12, 9747 AD Groningen, The Netherlands e-mail: [email protected] 2 Sterrewacht Leiden, Leiden University, Postbus 9513, 2300 RA Leiden, The Netherlands 3 Max Planck Institute for Extraterrestrial Physics, Giessenbachstrasse 1, 85748 Garching, Germany Received 13 February 2019 / Accepted XX Month 2019 ABSTRACT The velocity distribution of stars is a sensitive probe of the gravitational potential of the Galaxy, and hence of its dark matter dis- tribution. In particular, the shape of the dark halo (e.g. spherical, oblate, prolate) determines velocity correlations, and different halo geometries are expected to result in measurable differences. We here explore and interpret the correlations in the (vR; vz)-velocity distribution as a function of position in the Milky Way. We select a high quality sample of stars from the Gaia DR2 catalog, and char- acterise the orientation of the velocity distribution or tilt angle, over a radial distance range of [3 − 13] kpc and up to 4 kpc away from the Galactic plane while taking into account the effects of the measurement errors. The velocity ellipsoid is consistent with spherical alignment at R ∼ 4 kpc, while it progressively becomes shallower at larger Galactocentric distances and is cylindrically aligned at R = 12 kpc for all heights probed. Although the systematic parallax errors present in Gaia DR2 likely impact our estimates of the tilt angle at large Galactocentric radii, possibly making it less spherically aligned, their amplitude is not enough to explain the deviations from spherical alignment. -
Roger A. Chevalier Curriculum Vitae Address
Roger A. Chevalier Curriculum Vitae Address Department of Astronomy, University of Virginia, P. O. Box 400325, Charlottesville, VA 22904 (434) 924–4889 (office); (434) 924–3104 (fax); [email protected] Education Ph.D. Astronomy, Princeton University, 1973 B.S. Astronomy, California Institute of Technology, 1970 Employment W. H. Vanderbilt Professor of Astronomy, University of Virginia, Charlottesville, VA, 1990– Professor of Astronomy, University of Virginia, 1985–90 Chair, Department of Astronomy, University of Virginia, 1985–88, 1989–92 Associate Professor of Astronomy, University of Virginia, 1979–85 Associate Astronomer, Kitt Peak National Observatory, Tucson, AZ, 1976–79 Assistant Astronomer, Kitt Peak National Observatory, Tucson, AZ, 1973–76 Honors NASA Public Service Group Achievement Award to Supernova Science Team (SN 1987A), 1989 Virginia’s Outstanding Scientist Award, 1991 President’s and Visitors’ Research Prize, University of Virginia, 1992 Dannie Heineman Prize for Astrophysics, 1996 Elected to National Academy of Sciences, 1996 Meeting “A Festival of Cosmic Explosions: Celebrating the Contributions and Ac- complishments of Roger Chevalier” held August 21-23, 2009, Caltech, Pasadena, CA Committees American Astronomical Society: High Energy Astrophysics Division Executive Committee (1985–86); Councilor (1988–91); Heineman Prize Committee (2001– 03; Chair 2003) Associated Universities for Research in Astronomy: Observatories Visiting Com- mittee (1999–2002; Chair 2002) National Science Foundation: Committee on Large Optical/Infrared Telescopes (1985–86); Committee of Visitors, Division of Astronomical Sciences (1990, 1993); Advisory Committee, Division of Astronomical Sciences (1991–93) National Aeronautics and Space Administration: Science Working Group on Su- pernova 1987A (1987–88) National Academy of Sciences/National Research Council: Committee on Space Astronomy and Astrophysics (1987–88); Theory Panel of Astronomy Survey 1 Committee for the 1990’s (1989–90); Committee on Astronomy and Astrophysics (1997–2002); Watson Prize Committee; U.S. -
Observational Aspects of Globular Cluster and Halo Stars in the GALAH Survey
THE UNIVERSITY OF NEW SOUTH WALES DOCTORAL THESIS Observational aspects of globular cluster and halo stars in the GALAH survey Student: Supervisor: Mohd Hafiz MOHD SAADON Associate Professor Sarah MARTELL A thesis submitted in fulfillment of the requirements for the degree of Doctor of Philosophy in the School of Physics Faculty of Science The University of New South Wales 12 March 2021 i ii iii iv Declaration of Authorship I, Mohd Hafiz MOHD SAADON, declare that this thesis titled, “Observational aspects of globular cluster and halo stars in the GALAH survey” and the work presented in it are my own. I confirm that: • This work was done wholly or mainly while in candidature for a research degree at this University. • Where any part of this thesis has previously been submitted for a degree or any other qualification at this University or any other institution, this has been clearly stated. • Where I have consulted the published work of others, this is always clearly at- tributed. • Where I have quoted from the work of others, the source is always given. With the exception of such quotations, this thesis is entirely my own work. • I have acknowledged all main sources of help. Signed: Date: v “In loving memory of my grandmothers, Ramlah and Halijah, who wished to see me this far but could not be here anymore.” – your grandson. “To Amani, my sweet little angel, this thesis is your sibling.” – your father. vi THE UNIVERSITY OF NEW SOUTH WALES Abstract Doctor of Philosophy Observational aspects of globular cluster and halo stars in the GALAH survey by Mohd Hafiz MOHD SAADON This thesis is a study of the observational aspects of globular cluster and halo stars in the Galactic Archaeology with HERMES (GALAH) survey. -
"Southern Skies and Cosmic Questions" by Ed Bertschinger
Edmund Bertschinger Southern Skies and Cosmic Questions how big is the observable universe? what is it made of? why does space repel itself? n January 2006—the middle of summer in the i Southern hemisphere—a bus full of MIT alumni, family, and friends ascended a narrow, winding dirt road through the coastal range of Chile up to 2400 meters (8000 feet) elevation. After visiting European and American national observatory sites during the preceding days, the group figure 1 Wide-angle view of the Southern sky was eager to see the private observatory of which MIT is a part- taken from the Andes Mountains of Argentina on January 28, 2007. Visible ner: the Magellan Telescopes at Las Campanas Observatory. Only are Comet McNaught, the brightest comet in over 40 years; the splotchy Milky Way; and one traveler in the group had been there before: five years earlier, our two satellite galaxies, the Magellanic Clouds. (Photo credit and copyright: Miloslav Jane Pappalardo had attended the dedication of the newly built Druckmüller) telescopes. The author, serving as a scientific tour guide, was excited to arrive finally at the facility his colleague, MIT Magellan director Prof. Paul Schechter, had helped design and commission. After traveling a week through Northern Chile we had reached the summit of a remarkable trip. C H i L E — a th i n st r i P of L a n d between the Pacific Ocean and the crest of the Andes—is an astronomical mecca. The cold Humboldt ocean current flow- ing northward from Antarctica keeps the marine clouds low against the wall of coastal mountains. -
Curriculum Vitae of Robert J. Scherrer
CURRICULUM VITAE OF ROBERT J. SCHERRER Address: Department of Physics and Astronomy Vanderbilt University Nashville, TN 37235 phone: 615-343-3230/615-343-6419 email: [email protected] Education Sept. 1977 - June 1981: Princeton University, A.B. in physics, magna cum laude Sept. 1981 - Aug. 1983: Cambridge University, M.A. in physics. Sept. 1983 - Oct. 1986: University of Chicago, Ph.D. in physics (Thesis advisor: Prof. Michael S. Turner). Positions Held Oct. 1986 - Jun. 1987, Oct. 1987 - Jul. 1988: Harvard University, Postdoctoral Research Associate. Jun. 1987 - Oct. 1987, Jul. 1988 - Dec. 1988: Queen Mary College, University of London, NATO Postdoctoral Fellow. Jan. 1989 - Sept. 1993: Assistant Professor, Department of Physics, The Ohio State University. Oct. 1993 - Sept. 1998: Associate Professor, Department of Physics, The Ohio State University. Oct. 1996 - Sept. 1998: Associate Professor, Department of Astronomy, The Ohio State University. Sept. 1997 - May 1998: Visiting Scientist, Theoretical Astrophysics Group, Fermilab Oct. 1998 - Aug. 2003: Professor, Department of Physics and Department of Astronomy, The Ohio State University. Oct. 1999 - Aug. 2003: Vice-Chair for Undergraduate Studies, Department of Physics, The Ohio State University Sept. 2003 - present: Professor, Department of Physics and Astronomy, Vanderbilt University. Jan. 2004 - present: Chair, Department of Physics and Astronomy, Vanderbilt University Honors and Awards Marshall Scholarship (1981-83). McCormick Graduate Fellowship (University of Chicago 1983-86). NATO Postdoctoral Fellowship (1987-88). The Ohio State University Alumni Award for Distinguished Teaching (1999). Fellow of the American Physical Society (2001). 5th Prize, Gravity Research Foundation Essay Competition (2007). Klopsteg Memorial Award, American Association of Physics Teachers (2010). Books Quantum Mechanics: An Accessible Introduction Robert J. -
THEO MURPHY INTERNATIONAL SCIENTIFIC MEETING on Testing
THEO MURPHY INTERNATIONAL SCIENTIFIC MEETING ON Testing general relativity with cosmology Monday 28 February – Tuesday 1 March 2011 The Kavli Royal Society International Centre, Chicheley Hall, Buckinghamshire Organised by Professor Pedro Ferreira, Professor Rachel Bean and Professor Andrew Taylor - Programme and abstracts - Speaker biographies The abstracts that follow are provided by the presenters and the Royal Society takes no responsibility for their content. Testing general relativity with cosmology Monday 28 February – Tuesday 1 March 2011 The Kavli Royal Society Centre, Chicheley Hall, Buckinghamshire Organised by Professor Pedro Ferreira, Professor Rachel Bean and Professor Andrew Taylor Day 1 – Monday 28 February 2011 09.15 Welcome by Professor Sir Peter Knight FRS , Principal, The Kavli Royal Society Centre Welcome by Professor Pedro Ferreira , Organiser 09.30 Constraining the cosmic growth history with large scale structure Professor Rachel Bean, Cornell University, USA 10.00 Discussion 10.15 One gravitational potential or two? Forecasts and tests Professor Edmund Bertschinger, Massachusetts Institute of Technology, USA 10.45 Discussion 11.00 Coffee 11.30 Cosmological tests of gravity Dr Constantinos Skordis, The University of Nottingham, UK 12.00 Discussion 12.15 Testing modified gravity with next generation weak lensing experiments Dr Thomas Kitching, University of Edinburgh, UK 12.45 Discussion 13.00 Lunch 14.00 Model independent tests of cosmic gravity Professor Eric Linder, University of California at Berkeley, USA 14.30 -
New Perspectives in Understanding the Galactic Halo
New perspectives in understanding the Galactic halo Amina Helmi New perspectives in understanding the Galactic halo In collaboration with Facundo Gomez, Andrew Cooper, Simon White, Anthony Brown, Yang-Shyang Li Why care about stellar halos? • Most metal-poor and ancient stars in the MW • window into the early Universe • Orbiting outskirts of galaxies: good mass probes • Can form from the superposition of disrupted satellites • stars retain memory of their origin -> merger history Helmi, Cooper et al. (2010) Outer Stellar halo - Substructure common in the halo (SDSS, 2MASS…) -> mergers Broad, diffuse streams (large progenitors? …but beware of biases) -> overdensities -> nature not always clear Belokurov et al 2007 Belokurov Some questions • What are the properties of stellar halos and satellites in ΛCDM? How do they compare to the Milky Way or M31? • What are models predictions for future surveys? • What do we learn about the history of a galaxy from its stellar halo? Stellar halo and Substructure in ΛCDM – Aquarius project: very high-resolution simulations of formation of 6 different dark matter halos ressembling the Milky Way (by mass) - Cooper et al. (2009) combined with phenomenological galaxy formation model -> predict properties of (accreted) stellar halos in CDM See also Bullock & Johnston 2005; De Lucia & Helmi 2008 Springel et al. 2008 Aquarius stellar halos - 1% most bound particles represent stars/stellar pops in these objects - Follow the history, their present-day location and dynamics Stellar halo formation in the Aquarius simulations Cooper et al. 2010 Helmi, Cooper et al. 2010 Aquarius “accreted” stellar halos Large variation from halo to halo -> reflects different histories Large amount of substructure -> history may be recovered Cooper et al. -
Elemental Abundances in the Local Group: Tracing the Formation History of the Great Andromeda Galaxy
Elemental Abundances in the Local Group: Tracing the Formation History of the Great Andromeda Galaxy Thesis by Ivanna A. Escala In Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy CALIFORNIA INSTITUTE OF TECHNOLOGY Pasadena, California 2020 Defended 2020 May 29 ii © 2020 Ivanna A. Escala ORCID: 0000-0002-9933-9551 All rights reserved iii Para mi familia, y para mi iv ACKNOWLEDGEMENTS I would like to thank the many people that have provided me with guidance through- out my thesis, and who have helped me reach the point in my life defined by this achievement. It would have been infinitely more challenging without you all, and I am grateful beyond words. First and foremost, I would like to thank my thesis advisor, Evan N. Kirby, for always making his students a priority. He has been an invaluable mentor, teacher, collaborator, and friend. I am especially thankful that Evan had enough trust in my ability as a competent and independent scientist to be supportive of my extended visit to Princeton. I am privileged to have him as an advisor. I would also like to thank my various mentors throughout my undergraduate edu- cation at the University of California, San Diego, to whom I am indebted: Adam J. Burgasser, who granted me my first opportunity to do research in astronomy, and who believed in me when I most needed it; Dušan Kereš, who helped me develop my skills as a nascent researcher with immeasurable patience and kindness; and Alison Coil, who provided me with much appreciated advice and support on the challenges of navigating a career in astronomy. -
Mass and Shape of the Milky Way's Dark Matter Halo with Globular
A&A 621, A56 (2019) Astronomy https://doi.org/10.1051/0004-6361/201833355 & c ESO 2019 Astrophysics Mass and shape of the Milky Way’s dark matter halo with globular clusters from Gaia and Hubble Lorenzo Posti and Amina Helmi Kapteyn Astronomical Institute, University of Groningen, PO Box 800, 9700 AV Groningen, The Netherlands e-mail: [email protected] Received 3 May 2018 / Accepted 5 November 2018 ABSTRACT Aims. We estimate the mass of the inner (<20 kpc) Milky Way and the axis ratio of its inner dark matter halo using globular clusters as tracers. At the same time, we constrain the distribution in phase-space of the globular cluster system around the Galaxy. Methods. We use the Gaia Data Release 2 catalogue of 75 globular clusters’ proper motions and recent measurements of the proper motions of another 20 distant clusters obtained with the Hubble Space Telescope. We describe the globular cluster system with a distribution function (DF) with two components: a flat, rotating disc-like one and a rounder, more extended halo-like one. While fixing the Milky Way’s disc and bulge, we let the mass and shape of the dark matter halo and we fit these two parameters, together with six others describing the DF, with a Bayesian method. +0:18 11 +0:18 Results. We find the mass of the Galaxy within 20 kpc to be M(<20 kpc) = 1:91−0:17 × 10 M , of which MDM(<20 kpc) = 1:37−0:17 × 11 10 M is in dark matter, and the density axis ratio of the dark matter halo to be q = 1:30 ± 0:25. -
Curriculum Vitae of Prof. Dr. Amina Helmi
Curriculum Vitae of Prof. Dr. Amina Helmi Kapteyn Astronomical Institute University of Groningen Landleven 12, 9747 AG Groningen – The Netherlands Phone: +31 50 3634045 e-mail: [email protected] Date and place of birtH: 6/10/1970, BaHia Blanca (Argentina) Nationality: Argentina/NetHerlands Education PhD in Astronomy (2000), The formation of tHe Galactic Halo Leiden University (“Cum Laude”), supervisors: P.T. de Zeeuw and S.D.M. WHite MSc in Astronomy (1994), specialization in THeoretical PHysics, University of La Plata (9.94/10) Work experience since completing PhD Professor of Dynamics, Structure and Evolution of the Milky Way, Univ. of Groningen 2003 – to-date NOVA Postdoctoral Fellow, Univ. of UtrecHt: 2002 – 2003 Postdoctoral Fellow, Max Planck Inst. for Astrophysics: 2001 – 2002 Postdoctoral Fellow, University of La Plata: 2000 Research Interests: Structure, evolution and dynamics of tHe Milky Way and its satellites; dark matter Honours and prizes Member, Royal NetHerlands Academy of Sciences (KNAW, elected in 2017) Member, Royal Holland Society of Sciences and Humanities (KHMW, elected in 2016) VICI researcH grant (Innovation ScHeme, NWO) 2015 Pastoor Schmeits prize, 2010 ERC Starting Grant (European Science Foundation) 2009 Member, THe Young Academy, Royal NetHerlands Academy of Sciences (elected in 2007) Member, International Astronomical Union Christiaan Huygens Prize, 2004 VIDI researcH grant (Innovation ScHeme, NWO) 2003 CJ Kok prize, University of Leiden, 2000 Amelia EarHart FellowsHip Award, 1995 and 1997 Academic staff supervised Former PhD students: H. Tian (2017), T. K. Starkenburg (2016), J. T. Buist (2015), G. Monari (2014), M. Breddels (2013), C. Vera-Ciro (2013), E. Starkenburg (2011, witH E. -
THE ONCE and FUTURE MILKY WAY Data from the Gaia Spacecraft Are Radically Transforming How We See the Evolution of Our Galaxy
THE ONCE AND FUTURE MILKY WAY Data from the Gaia spacecraft are radically transforming how we see the evolution of our Galaxy. BY ADAM MANN ast April, Amina Helmi felt goose bumps while shape, these non-conformists were moving backwards, in driving to work in the northern Netherlands. It had orbits that were carrying them out of the Galactic plane. nothing to do with the weather — it was pure anticipa- Within weeks, the team had worked out that the Ltion. Just days earlier, a flood of data had been released luminous horde pointed to a long-hidden and especially from Gaia, a European Space Agency (ESA) mission that tumultuous chapter in the Milky Way’s history: a smash- has been mapping the Milky Way for five years. The Univer- up between the young Galaxy and a colossal companion1. sity of Groningen astronomer and her team were racing to That beast once circled the Milky Way like a planet around comb through the data for insights about the Galaxy before a star, but some 8 billion to 11 billion years ago, the two 3.0 IGO CC BY-SA ESA/GAIA/DPAC, others got there first. collided, massively altering the Galactic disk and scatter- Working on fast-forward, unable to sleep from the ing stars far and wide. It is the last-known major crash the excitement, Helmi and her colleagues sensed they Galaxy experienced before it assumed the familiar spiral were on to something. The team had spotted a set of shape seen today. 30,000 renegade stars. Unlike other objects in the main Although the signal of that ancient crash had been hiding body of the Milky Way, which orbit in a relatively flat disk in plain sight for billions of years, it was only through Gaia’s 284 | NATURE | VOL 565 | 17 JANUARY 2019 ©2019 Spri nger Nature Li mited. -
Halo Streams As Relicts from the Formation of the Milky Way 3 Consist of 300 – 500 Stellar Streams with Internal Velocity Dispersions of ∼ 5 Km S−1
Dynamics of Star Clusters and the Milky Way ASP Conference Series, Vol. 000, 2000 S. Deiters, B. Fuchs, A. Just, R. Spurzem, and R. Wielen, eds. Halo streams as relicts from the formation of the Milky Way Amina Helmi Leiden Observatory, P.O. Box 9513, 2300 RA Leiden, The Netherlands Abstract. In this contribution we discuss the expected properties of our halo if our Galaxy had been built from mergers of smaller systems. Using both analytic arguments and high-resolution simulations, we find that the Galactic halo in the Solar neighbourhood should have a smooth spatial distribution and that its stellar velocity ellipsoid should consist of several hundred kinematically cold streams, relicts from the different merging events. We also discuss observational evidence which supports this hierarchical picture: two stellar streams originating in the same sys- tem that probably fell onto the Milky Way about ten Gyr ago. Finally we address what future astrometric missions like FAME or GAIA may reveal by observing the motions of nearby halo stars. 1. Introduction In recent years, considerable theoretical effort has been put into understanding the properties of galaxies within the hierarchical paradigm of structure formation in the Universe (e.g. Kauffmann et al. 1999). Our own Galaxy can play a very important role in constraining these models. For the Milky Way we have access to kinematics, distances, ages and chemical compositions of individual stars, information which is available for no other system. Thus observable substructure leftover by the different merging events could be just at hand. The natural place to look for the stars of the various systems that merged to arXiv:astro-ph/0008086v1 4 Aug 2000 build up the Milky Way is the Galactic halo, since as such systems disrupt they leave trails of stars along their orbits.