The Dwarf Spheroidal Galaxy DDO 44: Stellar Populations and Distance
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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. -
Statistics and Properties of Emission-Line Regions in the Local
Mon. Not. R. Astron. Soc. 000, 000–000 (0000) Printed 27 April 2020 (MN LATEX style file v2.2) Statistics and Properties of Emission-Line Regions in the Local Volume Dwarf Galaxies I. D. Karachentsev1⋆, S.S.Kaisin1† 1Special Astrophysical Observatory of the Russian Academy of Sciences, Nizhnij Arkhyz, KChR, 369167, Russia 27 April 2020 ABSTRACT We used the Hα images from a large sample of nearby late-type dwarf galaxies to investigate properties of their emission structure. The sample consists of three hundred galaxies of the irregular (Irr), Magellanic irregular (Im), blue compact dwarf (BCD), and transition (Tr) types situated within a distance of 11 Mpc. In each galaxy, we indicated: the number of compact HII-regions, the presence of bubble-like or filament-like structures, the presence of a faint diffuse emission, and a sign of the global burst. The larger luminosity of a galaxy, the greater number of compact HII-sources in it. The integral and specific star-formation rates of the dwarf increase steeply with the increase of the number of HII-regions showing the evidence of the epidemic character of star-formation process. The dwarf galaxies with emission-line bubbles, or filaments, or signs of the global star-formation burst have approximately the same hydrogen-mass-to-luminosity ratio as that of the whole sample objects. arXiv:2004.11550v1 [astro-ph.GA] 24 Apr 2020 However, their mean star-formation rate is significantly higher than that of other galaxies in the sample. Emission bubble-like structures are found in the nearby dwarfs with a frequency of 1 case per 4-5 galaxies. -
Una Aproximación Física Al Universo Local De Nebadon
4 1 0 2 local Nebadon de Santiago RodríguezSantiago Hernández Una aproximación física al universo (160.1) 14:5.11 La curiosidad — el espíritu de investigación, el estímulo del descubrimiento, el impulso a la exploración — forma parte de la dotación innata y divina de las criaturas evolutivas del espacio. Tabla de contenido 1.-Descripción científica de nuestro entorno cósmico. ............................................................................. 3 1.1 Lo que nuestros ojos ven. ................................................................................................................ 3 1.2 Lo que la ciencia establece ............................................................................................................... 4 2.-Descripción del LU de nuestro entorno cósmico. ................................................................................ 10 2.1 Universo Maestro ........................................................................................................................... 10 2.2 Gran Universo. Nivel Espacial Superunivesal ................................................................................. 13 2.3 Orvonton. El Séptimo Superuniverso. ............................................................................................ 14 2.4 En el interior de Orvonton. En la Vía Láctea. ................................................................................. 18 2.5 En el interior de Orvonton. Splandon el 5º Sector Mayor ............................................................ 19 -
Surface Brightness Fluctuation Distances for Nearby Dwarf Elliptical
A&A 380, 90–101 (2001) Astronomy DOI: 10.1051/0004-6361:20011408 & c ESO 2001 Astrophysics Surface brightness fluctuation distances for nearby dwarf elliptical galaxies? H. Jerjen1,R.Rekola2, L. Takalo2, M. Coleman1, and M. Valtonen2 1 Research School of Astronomy and Astrophysics, The Australian National University, Mt Stromlo Observatory, Cotter Road, Weston ACT 2611, Australia 2 Tuorla Observatory, University of Turku, V¨ais¨al¨antie 20, 21500 Piikki¨o, Finland Received 12 July 2001 / Accepted 2 October 2001 Abstract. We obtained deep B and R-band CCD images for the dwarf elliptical (dE) galaxies DDO 44, UGC 4998, KK98 77, DDO 71, DDO 113, and UGC 7356 at the Nordic Optical Telescope. Employing Fourier analysis technique we measure stellar R-band surface brightness fluctuations (SBFs) and magnitudes in 29 different fields of the galaxies. Independent tip of the red giant branch distances for DDO 44, KK98 77, DDO 71 are used to convert their set of apparent into absolute SBF magnitudes. The results are combined with the corresponding local (B −R) colours and compared with the (B −R)−M R relation for mainly old, metal-poor stellar populations as predicted by Worthey’s population synthesis models using Padova isochrones. While the colour dependency of the theoretical relation is confirmed by the empirical data, we find a systematic zero point offset between observations and theory in the sense that models are too faint by 0.13 (0.02) mag. Based on these findings we establish a new semiempirical calibration of the SBF method as distance indicator for dE galaxies with an estimated uncertainty of ≈10%. -
An Observational Limit on the Dwarf Galaxy Population of the Local Group
An Observational Limit on the Dwarf Galaxy Population of the Local Group Alan B. Whiting1 Cerro Tololo Inter-American Observatory Casilla 603, La Serena, Chile [email protected] George K. T. Hau University of Durham Mike Irwin University of Cambridge Miguel Verdugo Institut f¨ur Astrophysik G¨ottingen, Germany ABSTRACT We present the results of an all-sky, deep optical survey for faint Local Group dwarf galaxies. Candidate objects were selected from the second Palomar survey (POSS-II) and ESO/SRC survey plates and follow-up observations performed to determine whether they were indeed overlooked members of the Local Group. arXiv:astro-ph/0610551v1 18 Oct 2006 Only two galaxies (Antlia and Cetus) were discovered this way out of 206 candi- dates. Based on internal and external comparisons, we estimate that our visual survey is more than 77% complete for objects larger than one arc minute in size and with a surface brightness greater than an extremely faint limit over the 72% of the sky not obstructed by the Milky Way. Our limit of sensitivity cannot be calculated exactly, but is certainly fainter than 25 magnitudes per square arc second in R, probably 25.5 and possibly approaching 26. We conclude that there are at most one or two Local Group dwarf galaxies fitting our observational cri- teria still undiscovered in the clear part of the sky, and roughly a dozen hidden behind the Milky Way. Our work places the “missing satellite problem” on a firm quantitative observational basis. We present detailed data on all our candidates, including surface brightness measurements. -
The Dwarf Galaxy Abundances and Radial-Velocities Team (DART) Large Programme – a Close Look at Nearby Galaxies
Reports from Observers The Dwarf galaxy Abundances and Radial-velocities Team (DART) Large Programme – A Close Look at Nearby Galaxies Eline Tolstoy1 The dwarf galaxies we have studied are nearby galaxies. The modes of operation, Vanessa Hill 2 the lowest-luminosity (and mass) galax- the sensitivity and the field of view are Mike Irwin ies that have ever been found. It is likely an almost perfect match to requirements Amina Helmi1 that these low-mass dwarfs are the most for the study of Galactic dSph galaxies. Giuseppina Battaglia1 common type of galaxy in the Universe, For example, it is now possible to meas- Bruno Letarte1 but because of their extremely low ure the abundance of numerous elements Kim Venn surface brightness our ability to detect in nearby galaxies for more than 100 stars Pascale Jablonka 5,6 them diminishes rapidly with increasing over a 25;-diameter field of view in one Matthew Shetrone 7 distance. The only place where we can shot. A vast improvement on previous la- Nobuo Arimoto 8 be reasonably sure to detect a large frac- borious (but valiant) efforts with single-slit Tom Abel 9 tion of these objects is in the Local spectrographs to observe a handful of Francesca Primas10 Group, and even here, ‘complete sam- stars per galaxy (e.g., Tolstoy et al. 200; Andreas Kaufer10 ples’ are added to each year. Within Shetrone et al. 200; Geisler et al. 2005). Thomas Szeifert10 250 kpc of our Galaxy there are nine low- Patrick Francois 2 mass galaxies (seven observable from The DART Large Programme has meas- Kozo Sadakane11 the southern hemisphere), including Sag- ured abundances and velocities for sev- ittarius which is in the process of merging eral hundred individual stars in a sample with our Galaxy. -
The Variable Star Population in the Sextans Dwarf Spheroidal Galaxy
TheThe variablevariable starstar populationpopulation inin thethe SextansSextans dwarfdwarf spheroidalspheroidal galaxygalaxy Kathy Vivas Cerro Tololo Interamerican Observatory La Serena, Chile In collaboration with Javier Alonso-García (U. of Antofagasta, Chile) Mario Mateo (U. of Michigan, USA) Alistair Walker (CTIO, Chile) David Nidever (NOAO, USA) DECam Community Science Workshop 2018 1 The Role of Variable Stars ● Tracers of different stellar populations ● Standard candles → Distance Scale Variable stars in the Carina dwarf spheroidal galaxy (Vivas & Mateo 2013) DECam Community Science Workshop 2018 2 Properties of the Satellites of the Milky Way Drlica-Wagner et al., 2015 The new discoveries are likely to be ultra-faint dwarf galaxies. Gallart et al. 2015 Classical dwarfs display a variety of SFRs DECam Community Science Workshop 2018 3 CMDs of Satellite Dwarfs Brown et al 2014 On the other hand, ultra-faint dwarfs seem Monelli et al 2003 to be consistent with only and old Galaxies like Carina show obvious population signs of multiple bursts of star formation DECam Community Science Workshop 2018 4 Leo T: a UFD with extended star formation Clementini et al (2012) DECam Community Science Workshop 2018 5 Helium-Burning Pulsating Stars 3.0 Anomalous Cepheids 2.0 0.7 RR Lyrae Stars Variable stars and theoretical isochrones in Leo I (Fiorentino et al 2012) DECam Community Science Workshop 2018 6 Dwarf Cepheid Stars (collective name for δ Scuti or SX Phe) Intermediate age population TO Old Population TO Coppola et al 2015, Vivas & Mateo 2013 DECam Community Science Workshop 2018 7 Dwarf Cepheids as distance indicators Need to study more systems! Cohen et al (2012) P-L relationship (independent of metallicity) → standard candles DECam Community Science Workshop 2018 8 Dwarf Cepheids in other galaxies 85 dwarf cepheids in Fornax A few thousand in (Poretti et al. -
Aaron J. Romanowsky Curriculum Vitae (Rev. 1 Septembert 2021) Contact Information: Department of Physics & Astronomy San
Aaron J. Romanowsky Curriculum Vitae (Rev. 1 Septembert 2021) Contact information: Department of Physics & Astronomy +1-408-924-5225 (office) San Jose´ State University +1-409-924-2917 (FAX) One Washington Square [email protected] San Jose, CA 95192 U.S.A. http://www.sjsu.edu/people/aaron.romanowsky/ University of California Observatories +1-831-459-3840 (office) 1156 High Street +1-831-426-3115 (FAX) Santa Cruz, CA 95064 [email protected] U.S.A. http://www.ucolick.org/%7Eromanow/ Main research interests: galaxy formation and dynamics – dark matter – star clusters Education: Ph.D. Astronomy, Harvard University Nov. 1999 supervisor: Christopher Kochanek, “The Structure and Dynamics of Galaxies” M.A. Astronomy, Harvard University June 1996 B.S. Physics with High Honors, June 1994 College of Creative Studies, University of California, Santa Barbara Employment: Professor, Department of Physics & Astronomy, Aug. 2020 – present San Jose´ State University Associate Professor, Department of Physics & Astronomy, Aug. 2016 – Aug. 2020 San Jose´ State University Assistant Professor, Department of Physics & Astronomy, Aug. 2012 – Aug. 2016 San Jose´ State University Research Associate, University of California Observatories, Santa Cruz Oct. 2012 – present Associate Specialist, University of California Observatories, Santa Cruz July 2007 – Sep. 2012 Researcher in Astronomy, Department of Physics, Oct. 2004 – June 2007 University of Concepcion´ Visiting Adjunct Professor, Faculty of Astronomical and May 2005 Geophysical Sciences, National University of La Plata Postdoctoral Research Fellow, School of Physics and Astronomy, June 2002 – Oct. 2004 University of Nottingham Postdoctoral Fellow, Kapteyn Astronomical Institute, Oct. 1999 – May 2002 Rijksuniversiteit Groningen Research Fellow, Harvard-Smithsonian Center for Astrophysics June 1994 – Oct. -
Gas Accretion from Minor Mergers in Local Spiral Galaxies⋆
A&A 567, A68 (2014) Astronomy DOI: 10.1051/0004-6361/201423596 & c ESO 2014 Astrophysics Gas accretion from minor mergers in local spiral galaxies? E. M. Di Teodoro1 and F. Fraternali1;2 1 Department of Physics and Astronomy, University of Bologna, 6/2, Viale Berti Pichat, 40127 Bologna, Italy e-mail: [email protected] 2 Kapteyn Astronomical Institute, Postbus 800, 9700 AV Groningen, The Netherlands Received 7 February 2014 / Accepted 28 May 2014 ABSTRACT We quantify the gas accretion rate from minor mergers onto star-forming galaxies in the local Universe using Hi observations of 148 nearby spiral galaxies (WHISP sample). We developed a dedicated code that iteratively analyses Hi data-cubes, finds dwarf gas-rich satellites around larger galaxies, and estimates an upper limit to the gas accretion rate. We found that 22% of the galaxies have at least one detected dwarf companion. We made the very stringent assumption that all satellites are going to merge in the shortest possible time, transferring all their gas to the main galaxies. This leads to an estimate of the maximum gas accretion rate of −1 0.28 M yr , about five times lower than the average star formation rate of the sample. Given the assumptions, our accretion rate is clearly an overestimate. Our result strongly suggests that minor mergers do not play a significant role in the total gas accretion budget in local galaxies. Key words. galaxies: interactions – galaxies: evolution – galaxies: kinematics and dynamics – galaxies: star formation – galaxies: dwarf 1. Introduction structures in the Universe grow by several inflowing events and have increased their mass content through a small number of The evolution of galaxies is strongly affected by their capabil- major mergers, more common at high redshifts, and through an ity of retaining their gas and accreting fresh material from the almost continuous infall of dwarf galaxies (Bond et al. -
Draft181 182Chapter 10
Chapter 10 Formation and evolution of the Local Group 480 Myr <t< 13.7 Gyr; 10 >z> 0; 30 K > T > 2.725 K The fact that the [G]alactic system is a member of a group is a very fortunate accident. Edwin Hubble, The Realm of the Nebulae Summary: The Local Group (LG) is the group of galaxies gravitationally associ- ated with the Galaxy and M 31. Galaxies within the LG have overcome the general expansion of the universe. There are approximately 75 galaxies in the LG within a 12 diameter of ∼3 Mpc having a total mass of 2-5 × 10 M⊙. A strong morphology- density relation exists in which gas-poor dwarf spheroidals (dSphs) are preferentially found closer to the Galaxy/M 31 than gas-rich dwarf irregulars (dIrrs). This is often promoted as evidence of environmental processes due to the massive Galaxy and M 31 driving the evolutionary change between dwarf galaxy types. High Veloc- ity Clouds (HVCs) are likely to be either remnant gas left over from the formation of the Galaxy, or associated with other galaxies that have been tidally disturbed by the Galaxy. Our Galaxy halo is about 12 Gyr old. A thin disk with ongoing star formation and older thick disk built by z ≥ 2 minor mergers exist. The Galaxy and M 31 will merge in 5.9 Gyr and ultimately resemble an elliptical galaxy. The LG has −1 vLG = 627 ± 22 km s with respect to the CMB. About 44% of the LG motion is due to the infall into the region of the Great Attractor, and the remaining amount of motion is due to more distant overdensities between 130 and 180 h−1 Mpc, primarily the Shapley supercluster. -
First Results from the MADCASH Survey: a Faint Dwarf Galaxy
Draft version August 10, 2016 Preprint typeset using LATEX style AASTeX6 v. 1.0 FIRST RESULTS FROM THE MADCASH SURVEY: A FAINT DWARF GALAXY COMPANION TO THE LOW MASS SPIRAL GALAXY NGC 2403 AT 3.2 MPC 1 Jeffrey L. Carlin2, David J. Sand3, Paul Price4, Beth Willman2, Ananthan Karunakaran5, Kristine Spekkens5,6, Eric F. Bell7, Jean P. Brodie8, Denija Crnojevic´3, Duncan A. Forbes9, Jonathan Hargis10, Evan Kirby11, Robert Lupton4, Annika H. G. Peter12, Aaron J. Romanowsky8, 13, and Jay Strader14 1Based in part on data collected at Subaru Telescope, which is operated by the National Astronomical Observatory of Japan. 2LSST and Steward Observatory, 933 North Cherry Avenue, Tucson, AZ 85721, USA; Haverford College, Department of Astronomy, 370 Lancaster Avenue, Haverford, PA 19041, USA; jeff[email protected] 3Texas Tech University, Physics Department, Box 41051, Lubbock, TX 79409-1051, USA 4Department of Astrophysical Sciences, Princeton University, Princeton, NJ 08544, USA 5Department of Physics, Engineering Physics and Astronomy, Queen’s University, Kingston, Ontario, Canada, K7L 3N6 6Department of Physics, Royal Military College of Canada, P.O. Box 17000, Station Forces, Kingston, ON K7L 7B4, Canada 7Department of Astronomy, University of Michigan, 1085 South University Ave, Ann Arbor, MI 48109, USA 8University of California Observatories, 1156 High Street, Santa Cruz, CA 95064, USA 9Centre for Astrophysics and Supercomputing, Swinburne University, Hawthorn VIC 3122, Australia 10Space Telescope Science Institute, 3700 San Martin Drive, -
Subaru Telescope —History, Active/Adaptive Optics, Instruments, and Scientific Achievements—
No. 7] Proc. Jpn. Acad., Ser. B 97 (2021) 337 Review Subaru Telescope —History, active/adaptive optics, instruments, and scientific achievements— † By Masanori IYE*1, (Contributed by Masanori IYE, M.J.A.; Edited by Katsuhiko SATO, M.J.A.) Abstract: The Subaru Telescopea) is an 8.2 m optical/infrared telescope constructed during 1991–1999 and has been operational since 2000 on the summit area of Maunakea, Hawaii, by the National Astronomical Observatory of Japan (NAOJ). This paper reviews the history, key engineering issues, and selected scientific achievements of the Subaru Telescope. The active optics for a thin primary mirror was the design backbone of the telescope to deliver a high-imaging performance. Adaptive optics with a laser-facility to generate an artificial guide-star improved the telescope vision to its diffraction limit by cancelling any atmospheric turbulence effect in real time. Various observational instruments, especially the wide-field camera, have enabled unique observational studies. Selected scientific topics include studies on cosmic reionization, weak/strong gravitational lensing, cosmological parameters, primordial black holes, the dynamical/chemical evolution/interactions of galaxies, neutron star mergers, supernovae, exoplanets, proto-planetary disks, and outliers of the solar system. The last described are operational statistics, plans and a note concerning the culture-and-science issues in Hawaii. Keywords: active optics, adaptive optics, telescope, instruments, cosmology, exoplanets largest telescope in Asia and the sixth largest in the 1. Prehistory world. Jun Jugaku first identified a star with excess 1.1. Okayama 188 cm telescope. In 1953, UV as an optical counterpart of the X-ray source Yusuke Hagiwara,1 director of the Tokyo Astronom- Sco X-1.1) Sco X-1 was an unknown X-ray source ical Observatory, the University of Tokyo, empha- found at that time by observations using an X-ray sized in a lecture the importance of building a modern collimator instrument invented by Minoru Oda.2, 2) large telescope.