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Dwarf Galaxy Types (≤ 1/100 L ; MV ≥ –18) the Galaxy Content of the Local Group

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[copyrighted background image removed] 27.08.2018 Grebel: Dwarf Galaxies in the Local Group 1 Dwarf Galaxy Types (≤ 1/100 L★; MV ≥ –18) The Galaxy Content of the Local Group ❏ Dwarf elliptical galaxies Certain or probable members: Early-type dwarfs. ≥ 104 galaxies within R ~ 1 Mpc. dEs ❏ Dwarf spheroidal galaxies Gas-deficient and now largely quiescent. 0 dIrrs § 3 spiral galaxies (~ 95% mass). dIrrs spirals ❏ Ultra-compact dwarf galaxies } High-density regions preferred. /dSphs § ≥ 101 dwarf and satellite galaxies ❏ Dwarf spirals / dwarf lenticulars Late-type dwarfs. (typically, MV ≥ –18). ❏ Dwarf irregular galaxies Gas-rich and usually star-forming. § Some satellites have own satellites... ❏ Blue compact dwarf galaxies Low-density regions preferred. } dE dSph dIrr dSphs ❏ Ultra-diffuse galaxies ❏ Tidal dwarf galaxies Pictures not on same scale dE dSph UCD dS0, dS dIrr BCD Gas-deficient, late-type dwarf galaxies: dwarf elliptical (dEs: 3; 1 cE) & dwarf spheroidal galaxies (dSphs: ≥ 83) Gas-rich, early-type dwarf galaxies: dwarf irregular galaxies (dIrrs: 9), transition types (dIrrs/dSphs: 5) 27.08.2018 Grebel: Dwarf Galaxies in the Local Group 2 27.08.2018 Grebel: Dwarf Galaxies in the Local Group 3 New Satellites of Size – Luminosity Relation Morphology- the Milky Way density ❑ New discoveries mainly have mainly very low surface brightnesses. and M31 by Year relation ❑ Note overlap between GC −2 ❑ and dSph locus in L (M ) After Muñoz et al. 2018 of Publication V Blue points: GCs. −2 −2 Mainly thanks to large = 18 mag arcsec 26 mag V imaging surveys in the μ arcsec northern hemisphere 22 mag arcsec Grebel 2017 (esp. SDSS, PAndAS, PS1). −2 Increasingly also southern 30 mag hemisphere (e.g., DES, arcsec VST-ATLAS, Subaru). Muñoz et al. 2018 Total satellite population of the Milky Way estimated (NB: In these two diagrams +53 Walker 2012 142−34 down to MV = 0 in some of the red crosses simulations (Newton et al. 2017). stand for GCs.) 27.08.2018 Grebel: Dwarf Galaxies in the Local Group 4 27.08.2018 Grebel: Dwarf Galaxies in the Local Group 5 At Low Masses: Distinguishing Galaxies & Star Clusters No general definition exists but conventionally the following criteria are used: Galaxies: Star clusters: q Gravitationally bound q Gravitationally bound q Contain dark matter q No dark matter Laevens 1 / Crater I q Considerable metallicity spread q Negligible metallicity spread McConnachie Willman & h 2012 Strader 2012 r within L / dyn M Globular clusters Dark matter Galaxies Sawala et al. 2016 MV 27.08.2018 Grebel: Dwarf Galaxies in the Local Group 6 27.08.2018 Grebel: Dwarf Galaxies in the Local Group 7 Black dots, black circles: Satellites not in the plane. Gaia Collaboration et al. 2018 Green circles, colored dots: Satellites in plane. Orbit backward integration Satellite Planes Satellite Planes for 2.5 Gyr. Thin planes of satellites ❑ Long-term survival of planes depends around MW and M31 ❑ on orientation of dwarfs’ orbit. (e.g., Kunkel & Demers 1976; ➙ Thin plane survives only if aligned with one of the semi-major or semi-minor axes Lynden-Bell 1976; Koch & Grebel 2006; Pawlowski et q of a triaxial halo, or in the polar or equatorial planes of a spherical halo. al. 2012; Ibata et al. 2013). (Bowden et al. 2013; Fernando et al. 2016). q Satellite planes at least partially fortuitous. ΛCDM simulations: q Planes may contain co-rotating pairs of satellites, but planes need not co-rotate. q Planes form through q Planes not kinematically coherent structures as a whole; transitory features. q accretion along large Buck et al. 2015 E.g., Cautun et al. 2015; Buck et al. 2015; Gillet et al. 2015; Bowden et al. 2013; Fernando et al. 2016; q filaments of DM around galaxies at high redshift. Lipnicky & Chakrabarti 2017. q Dwarf galaxy accretion is highly anisotropic, takes place preferentially in the plane ❑ HST & Gaia proper motions: MW q determined by the major and intermediate axes of the DM host halo shape, and, ❑ dwarfs not on single narrow plane. q within this plane, is clustered along the shape major axis. ❑ Orbits typically ^ to MW disk, but Gaia Colla- q High-concentration massive halos tend to have thinner and richer planes. ❑ span broad range of orientations Different boration colors: et al. ❑ (of 39, 11 co-orbit, 6 counter-orbit). different 2018 q Most satellites were accreted along the richest filaments. Galactic ➙ Single major event excluded, but potentials q Group accretion (multiple satellites) is more common for fainter satellites. ❑ multiple infall along cosmic web . q Degree of anisotropic accretion higher for most massive satellites. ❑ filament aligned with Z-axis possible. (Gaia Collaboration et al. 2018; Fritz et al. 2018; Simon E.g., Libeskind et al. 2015; Buck et al. 2015, Shao et al. 2018. ❑ 2018; Casetti-Dinescu et al. 2018, Sohn et al. 2017; Massari & Helmi 2018; Kallivayalil et al. 2018). 27.08.2018 Grebel: Dwarf Galaxies in the Local Group 8 27.08.2018 Grebel: Dwarf Galaxies in the Local Group 9 Infall of Dwarf Groups ❑ Proper ❑ motions ❑ (Gaia DR2) ❑ and radial ❑ velocities ❑ of ultra- ❑ faint dSphs ❑ near MCs: § 4 (Hor 1, § Car 2, 3, § Hyd 1) § came in with Conn et al. 2018 § MCs. § Possibly [copyrighted background image removed] § also Hyd 2, Dra 2. 3 (Ret 2, Tuc 2, Gru 1) uncertain. § 4 are unlikely (Tuc 3, Cra 2, Tri 2, Aqu 2). § Remaining ones: no proper motions yet. (Kallivayalil et al. 2018) § 4 – 6 LMC satellites: Consistent with expectations from ΛCDM. 27.08.2018 Grebel: Dwarf Galaxies in the Local Group 10 27.08.2018 Grebel: Dwarf Galaxies in the Local Group 11 Kirby et al. 2013 De Lucia & Helmi 2008; Cooper et al. 2010 accreted stars (ex situ) in-situ stars Metallicity Scaling Relations Stellar Halo Origins ❑ (Dwarf) galaxies: clear metallicity – luminosity relation q Stellar halos composed in part of ❑ Signature of galaxies’ ability to retain metals in their grav. ❑ potential wells or of correlation between SF efficiency and stellar mass. q accreted stars and in part of stars ❑ GCs: No such relation. Also, don’t extend to as low [Fe/H] as ultrafaint dSphs. q formed in situ. Rodriguez- ❑ Even ultrafaint, very metal-poor dSphs show metallicity spread and extended SFHs. q Halos grow from “from inside out”. Gomez et al. 2016 GCs q Wide variety of satellite accretion histories from smooth growth to discrete events. Dwarf galaxies 8 9 q ≤ 5 luminous satellites (10 – 10 M¤) are the main contributors to stellar halos. q Merged > 9 Gyr ago (inner halo). Satellite accretion mainly between 1 < z < 3. Pillepich et al. 2015 ω Cen M54 Possibly flattening present-day ex-situ stars present-day at metal-poor end? (incl. those still in in-situ stars self-bound satellites) Simon et al. 2017 27.08.2018 Grebel: Dwarf Galaxies in the Local Group 12 27.08.2018 Grebel: Dwarf Galaxies in the Local Group 13 [Fe/H] vs. [α/Fe] in Dwarfs Trends in Individual Element Abundance Ratios Position of turnover (“α knee”) shows how far r-process: n-rich nuclei Beniamini et al. 2016 enrichment could proceed until onset of SNe Ia. formeD rapidly in massive Measure of SFE and retention of enriched ejecta. stars via n-capture (~104s) Sgr dSph: Position of “knee” shows: early accretion and b decay, e.g., Eu: (before knee formed) of Sgr-like galaxies could have q Eu mass in ultra- contributed metal-rich parts of inner MW halo. q faint dSphs and SN II Beniamini et al. 2016 α α Fe SN Ia q large scatter in Fe α q abundances of Stochasticity begins q r - process elements to dominate q (anD Derivatives, mass q number A ≥ 90) Hendricks et al. 2014 in metal-poor dSphs (anD in metal-poor stars in MW): ProDuceD in rare events! Possibly in neutron star mergers. (Beniamini et al. 2016) As with α elements, we see contributions from inDiviDual events. Position of “α knee” correlates r-process retention when events not too energetic. Low r-process frequency (models: Sgr α knee: −1.3 dex. with dSph luminosity (or stellar ~ 0.07 of u.f. dSphs) µ with σ([Eu/Fe]) in MW metal-poor stars. (Beniamini et al. 2018) de Boer et al. 2014 MW α knee: −1.0 dex. mass). MoDels suggest that in an initial, metal-poor ISM stochastic effects dominate. Inhomogeneous pollution, few SNe (Marcolini et al. 2008). 27.08.2018 Grebel: Dwarf Galaxies in the Local Group 14 27.08.2018 Grebel: Dwarf Galaxies in the Local Group 15 Trends in Individual Element Abundance Ratios For –4 ≤ [Fe/H] ≤ –2 (small sample sizes still): q a elements in classical dSphs and MW halo q very similar. Plateau at [a/Fe] ≈ 0.3. q Enrichment by massive stars with “normal” IMF. q Fe peak, Al, Na in dSphs follow MW halo trends ➙ Produced in same nucleosynthetic processes [copyrighted background image removed] (C burning) independent of host galaxy mass. q Ultra-faint dSphs (Boo I, Leo IV) show evidence q for pollution by SNe Ia (SF must have lasted q at least about 1 Gyr). ➙ “Long-lasting” SF. q Ultra-faint dSph UMa II: No SN Ia enrichment! n-capture elements Sr, Ba: Mashonkina et al. 2017 q Classical dSphs and MW halo show large q dispersion in [Sr/Fe] below [Fe/H] ~ –3. (see also Tafelmeyer et al. 2010; Koch et al. 2013; q Same [Sr/Ba] dichotomy in classical dSphs and MW halo: Frebel & Norris 2015; ➙ two nucleosynthesis channels for Sr. Battaglia et al. 2017) q Ultra-faint dSphs: mainly distinctly low [Sr/Ba] values. Lack 2nd channel of Sr q production. Possibly due to undersampling of IMF at high-mass end.
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    COMMISSION H1 THE LOCAL UNIVERSE (L’UNIVERS LOCAL) PRESIDENT Dante Minniti VICE-PRESIDENT Grazina Tautvaisiene PAST PRESIDENT Eva K. Grebel SECRETARY Aoki Wako ORGANIZING COMMITTEE Evangelie Athanassoula, John Beckman, Maria-Rosa Cioni, Yasuo Fukui, Eva K. Grebel, Margaret Meixner, Dante Minniti, Grazina Tautvaisiene, Aoki Wako, Gang Zhao ANNUAL SUMMARY REPORT 2019 1. Introduction The IAU Commission H1 on “The Local Universe (L'Univers Local)” is one of the three commissions of Division H, “Interstellar Matter and Local Universe”. This Commission H1 was established in mid-2015, and it was presided by Eva Grebel (Germany) during its first triennial period. IAU Commission H1 presently counts with 331 members. Our Commission focuses on studies of the Milky Way and nearby galaxies, where we can resolve galaxies into stars. A range of observational and theoretical research on the stellar populations, interstellar medium, dark matter of local galaxies, etc. are covered in order to understand galaxy formation, history and evolution. Recent and future photometric, spectroscopic, and astrometric surveys (both ground-based and space- based) contribute to the knowledge revolution that this field is experiencing. Current and forthcoming facilities will yield an even deeper understanding of our local Universe. 2. Activities 2019 This past year 2019 organizing committee members attended several international meetings and workshops worldwide, representing the IAU and giving invited/contributed talks and posters. Among the major developments on the area of Milky Way and Nearby galaxies that occurred during the year 2019, we can mention as examples the data releases and important publications from the following large surveys (in random order, incomplete list): * Astrometry - Continuing research on the Gaia DR2 released on April 2018 yielding a number of publications.
  • A New Faint Milky Way Satellite Discovered in the Pan-STARRS1 3 Survey', Astrophysical Journal Letters, Vol

    A New Faint Milky Way Satellite Discovered in the Pan-STARRS1 3 Survey', Astrophysical Journal Letters, Vol

    Edinburgh Research Explorer A New Faint Milky Way Satellite Discovered in the Pan-STARRS1 3 Survey Citation for published version: Laevens, BPM, Martin, NF, Ibata, RA, Rix, H, Bernard, EJ, Bell, EF, Sesar, B, Ferguson, AMN, Schlafly, EF, Slater, CT, Burgett, WS, Chambers, KC, Flewelling, H, Hodapp, KA, Kaiser, N, Kudritzki, R, Lupton, RH, Magnier, EA, Metcalfe, N, Morgan, JS, Price, PA, Tonry, JL, Wainscoat, RJ & Waters, C 2015, 'A New Faint Milky Way Satellite Discovered in the Pan-STARRS1 3 Survey', Astrophysical Journal Letters, vol. 802, no. 2, 18. https://doi.org/10.1088/2041-8205/802/2/L18 Digital Object Identifier (DOI): 10.1088/2041-8205/802/2/L18 Link: Link to publication record in Edinburgh Research Explorer Document Version: Publisher's PDF, also known as Version of record Published In: Astrophysical Journal Letters General rights Copyright for the publications made accessible via the Edinburgh Research Explorer is retained by the author(s) and / or other copyright owners and it is a condition of accessing these publications that users recognise and abide by the legal requirements associated with these rights. Take down policy The University of Edinburgh has made every reasonable effort to ensure that Edinburgh Research Explorer content complies with UK legislation. If you believe that the public display of this file breaches copyright please contact [email protected] providing details, and we will remove access to the work immediately and investigate your claim. Download date: 24. Sep. 2021 The Astrophysical Journal Letters, 802:L18 (6pp), 2015 April 1 doi:10.1088/2041-8205/802/2/L18 © 2015.
  • The Rotation of the Halo of NGC6822 Determined from the Radial Velocities of Carbon Stars

    The Rotation of the Halo of NGC6822 Determined from the Radial Velocities of Carbon Stars

    The rotation of the halo of NGC6822 determined from the radial velocities of carbon stars { Graham Peter Thompson { Centre for Astrophysics Research School of Physics, Astronomy and Mathematics University of Hertfordshire Submitted to the University of Hertfordshire in part fulfilment of the requirements of the degree of Master of Philosophy in Astrophysics Supervisor: Professor Sean G. Ryan { April 2016 { Declaration I hereby certify that this dissertation has been written by me in the School of Physics, Astronomy and Mathematics, University of Hertfordshire, Hatfield, Hertfordshire, and that it has not been submitted in any previous application for a higher degree. The core of the dissertation is based on original work conducted at the University of Hertfordshire, and some of the ideas for further work are drawn from topics studied during an earlier Master of Science. All material in this dissertation which is not my own work has been properly acknowledged. { Graham Peter Thompson { ii Acknowledgements I thank Professor Ryan for his invaluable support and patient guidance as my super- visor, throughout this study. His incisive questioning, thoughtful comments, helpful suggestions and, at times, hands-on assistance throughout the study, preparation of a paper to MNRAS and the writing of this dissertation have been invaluable. I thank also Dr Lisette Sibbons, whose work on the spectral classification of carbon stars in NGC 6822 was the genesis of my study. Dr Sibbons was responsible for the acquisition and reduction of the spectra I used in the study. She also provided me with background information related to the stars in the sample, and general advice.