DOCSLIB.ORG

UNIFORM CHEMICAL ABUNDANCES of OPEN CLUSTERS USING the CANNON by AMY E. RAY Bachelor of Science, 2013 Mississippi State Universi

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
UNIFORM CHEMICAL ABUNDANCES of OPEN CLUSTERS USING the CANNON by AMY E. RAY Bachelor of Science, 2013 Mississippi State Universi UNIFORM CHEMICAL ABUNDANCES OF OPEN CLUSTERS USING THE CANNON by AMY E. RAY Bachelor of Science, 2013 Mississippi State University Mississippi State, MS Master of Science, 2017 Mississippi State University Mississippi State, MS Submitted to the Graduate Faculty of the College of Science and Engineering Texas Christian University in partial fulfillment of the requirements for the degree of Master of Science December 2018 ACKNOWLEDGEMENTS IwouldliketothankDr.Frinchaboyforbeinganexcellentadvisor. Thank you fellow graduate students, my committee, my parents, and my puppy Andromeda “Annie” Ray. I would like to acknowledge grant support for this research from the National Science Foundation (AST-1311835 & AST-1715662). Funding for SDSS-III has been provided by the Alfred P. Sloan Foundation, the Participating Institutions, the National Science Foundation, and the U.S. Department of Energy Office of Science. The SDSS-III web site is http://www.sdss3.org/. SDSS-III is managed by the Astrophysical Research Consortium for the Participating Institutions of the SDSS-III Collaboration including the University of Arizona, the Brazil- ian Participation Group, Brookhaven National Laboratory, Carnegie Mellon University, University of Florida, the French Participation Group, the German Participation Group, Harvard University, the Instituto de Astrofisica de Canarias, the Michigan State/Notre Dame/JINA Participation Group, Johns Hopkins University, Lawrence Berkeley National Laboratory, Max Planck Institute for Astrophysics, Max Planck Institute for Extraterres- trial Physics, New Mexico State University, New York University, Ohio State University, Pennsylvania State University, University of Portsmouth, Princeton University, the Span- ish Participation Group, University of Tokyo, University of Utah, Vanderbilt University, University of Virginia, University of Washington, and Yale University. Funding for the Sloan Digital Sky Survey IV has been provided by the Alfred P. Sloan Foundation, the U.S. Department of Energy Office of Science, and the Participating Institutions. SDSS-IV acknowledges support and resources from the Center for High- Performance Computing at the University of Utah. The SDSS web site is www.sdss.org. SDSS-IV is managed by the Astrophysical Research Consortium for the Participating Institutions of the SDSS Collaboration including the Brazilian Participation Group, the Carnegie Institution for Science, Carnegie Mellon University, the Chilean Participation Group, the French Participation Group, Harvard-Smithsonian Center for Astrophysics, Instituto de Astrofisica de Canarias, The Johns Hopkins University, Kavli Institute for the Physics and Mathematics of the Universe (IPMU)/University of Tokyo, Lawrence Berke- ley National Laboratory, Leibniz Institut fur Astrophysik Potsdam (AIP), Max-Planck- Institut fur Astronomie (MPIA Heidelberg), Max- Planck-Institut fur Astrophysik (MPA Garching), Max-Planck- Institut fur Extraterrestrische Physik (MPE), National Astro- nomical Observatories of China, New Mexico State University, New York University, University of Notre Dame, Observatario Nacional/MCTI, The Ohio State University, Pennsylvania State University, Shanghai Astronomical Observatory, United Kingdom Participation Group, Universidad Nacional Autonoma de Mexico, University of Arizona, University of Colorado Boulder, University of Oxford, University of Portsmouth, Univer- sity of Utah, University of Virginia, University of Washington, University of Wisconsin, Vanderbilt University, and Yale University. ii Contents ListofCommonAcronymsandTermsinAstronomy viii 1 Introduction 1 1.1 ChemicalAbundances(Metallicity) . 2 1.2 Open Clusters . 4 1.3 Goals . 5 2 Data Collection and Interpretation 9 2.1 VictorBlancoTelescope ........................... 9 2.1.1 TheHydraMulti-FiberSpectrograph . 11 2.1.2 Data Preparation . 11 2.1.3 Cluster Membership Determination from (Frinchaboy & Majewski 2008) . 13 2.2 SpectralAnalysis ............................... 15 2.2.1 Line Broadening Mechanisms . 16 2.2.2 Curve of Growth . 19 2.2.3 Boltzmann Equation . 20 2.2.4 Saha Equation . 21 2.3 Important Stellar Parameters . 22 2.3.1 E↵ective Temperature . 23 2.3.2 Surface Gravity . 23 2.3.3 Metallicity . 24 2.3.4 Stellar Parameters and The Cannon ................ 25 3 Results 27 3.1 The Cannon .................................. 27 3.1.1 Training Set . 28 3.1.2 IndividualStatResultsandDataQuality. 31 3.1.3 Verification of Cluster Membership and Bulk Cluster Metallities . 33 3.2 TotalClusterSample ............................. 33 4 Discussion 35 4.1 Summary . 35 4.1.1 Comparison to Other Surveys . 36 4.1.2 Discrepancies . 42 iii 4.1.3 NewValues .............................. 44 4.2 Future Work . 44 A The Cluster Sample 46 Vita Abstract iv List of Figures 1.1 An example of a star cluster over time. The young cluster in the leftmost panel has most of its stars on the main sequence. With time, more stars move o↵the main sequence, and from the turno↵point an age can be estimated. 5 1.2 Average iron abundances for a sample of open clusters. The plus symbols connected by red lines indicate measurements for the same cluster. This highlights the wide scatter in abundances across surveys that are discussed in Yong et al. (2012). 6 2.1 The Blanco 4 m telescope at CTIO in Chile. 10 2.2 An example of a Cassegrain telescope. The Blanco 4 m has a similar setup. 10 2.3 The Hydra fiber positioner system that used to be on the Blanco 4 m. 11 2.4 A histogram from Frinchaboy & Majewski (2008) that shows the radial velocity distribution of all stars with proper motion data that are in the fieldofthecalibrationclusterNGC2682. 13 2.5 These graphs show the steps in the membership analysis process for NGC 2682 that was done by Frinchaboy & Majewski (2008). (a) shows the result of the radial velocity distribution convolution with a Gaussian kernel to smooth the histogram shown in Figure 2.4, (b) shows the same smoothing process that was done for stars that fall outside of the cluster radius of NGC 2682, (c) shows the probability distribution for the cluster where non- members appear ouside of the main peak, and (d) shows a 1D Gaussian fit to the cluster distribution in (c). 14 2.6 CMD showing all of the stars within the cluster radius for NGC 2682. The larger black circles are members from both RV and proper motion deter- minations, crosses are stars that were found to be non-members, triangles are stars with high RV, but no proper motion values and the small grey circles are other non-member stars (Frinchaboy & Majewski 2008). 15 2.7 This is an example of curve of growth for the Sun. The dashed lines are separating the three di↵erent regions of the three functional forms (CarrollOstlie). 20 2.8 An example of how surface gravity impacts the strength of lines. The surface gravity is lowest at the top spectrum and highest at the bottom spectrum. As surface gravity increases, the pressure broadening wings increase. 24 v 3.1 One-to-one plots showing a comparison between the values obtained using The Cannon and the APOGEE DR14 labels for the training set. 32 4.1 A one-to-one comparison of [Fe/H] values for open clusters in common between Santos et al. (2009) and this study. The grey shaded area indicates the 0.17 scatter above and below the blue one-to-one line. 37 4.2 A one-to-one± comparison of average [Fe/H] values obtained by Reddy et al. (2013; 2015) and this study for the open clusters in common. 38 4.3 A comparison of [Fe/H] values for open clusters in common from Netopil et al. (2016) and this study.......................... 40 4.4 A comparison of average [Fe/H] values for in common open clusters from this survey and from the literature compilation in Table 4.4. Blue stars are [Fe/H] averages for open clusters IC 4756 and orange diamonds are [Fe/H]averagesforopenclusterNGC5822. 41 vi List of Tables 1.1 The open clusters with no prior chemical abundance measurements. 7 1.2 The open clusters with chemical abundance measurements that will be used to verify the values obtained in this study for the 12 open clusters listed in Table 1.1. 8 3.1 Values for Teff ,logg, and [Fe/H] from APOGEE compared to The Cannon output for the training set. 28 4.1 Average in common open cluster iron abundance from Santos et al. (2009) compared to ( this study). 36 4.2 Average in common open cluster iron abundance comparison between Reddy et al. (2013; 2015) and this study..................38 4.3 Average iron abundances for open clusters in common between Netopil et al. (2016) and this study.......................... 39 4.4 Average open cluster iron abundance for open clusters in common between this study and other literature studies. 41 4.5 Average open cluster iron abundance for clusters with no prior measure- ments. .................................... 44 A.1 The output from The Cannon for every star in the open cluster sample. The errors for Teff ,logg, and [Fe/H] are 141 K, 0.29 dex, and 0.17 dex, respectively. Cluster members used in± the average± Fe/H cluster± de- termination are indicated by a “Y” in the last column and stars that were either non-members or dwarf stars are indicated by “N”. 46 vii List of Common Acronyms and Terms in Astronomy Metals – All elements heavier than hydrogen and helium • Metallicity – The mass fraction of metals in a star with respect to • hydrogen – [Fe/H] – Often used as a proxy for metallicity in stellar spectroscopic studies – [Fe/H] = log(Fe/H)star log(Fe/H) − dex – Decimal exponent (deprecated) • – Unit used for abundance value (e.g. [Fe/H] = 0.06 dex) LTE – Local
Load more

Recommended publications
  • Stellar Variability in Open Clusters. I. a New Class of Variable Stars in NGC
    Astronomy & Astrophysics manuscript no. ngc3766˙v3˙1b c ESO 2018 September 8, 2018 Stellar variability in open clusters I. A new class of variable stars in NGC 3766 N. Mowlavi1, F. Barblan1, S. Saesen1, and L. Eyer1 1Astronomy Department, Geneva Observatory, chemin des Maillettes, 1290 Versoix, Switzerland e-mail: [email protected] Accepted 16/04/2013 ABSTRACT Aims. We analyze the population of periodic variable stars in the open cluster NGC 3766 based on a 7-year multiband monitoring campaign conducted on the 1.2 m Swiss Euler telescope at La Silla, Chili. Methods. The data reduction, light curve cleaning, and period search procedures, combined with the long observation time line, allowed us to detect variability amplitudes down to the mmag level. The variability properties were complemented with the positions in the color-magnitude and color-color diagrams to classify periodic variable stars into distinct variability types. Results. We find a large population (36 stars) of new variable stars between the red edge of slowly pulsating B (SPB) stars and the blue edge of δ Sct stars, a region in the Hertzsprung-Russell (HR) diagram where no pulsation is predicted to occur based on standard stellar models. The bulk of their periods ranges from 0.1 to 0.7 d, with amplitudes between 1 and 4 mmag for the majority of them. About 20% of stars in that region of the HR diagram are found to be variable, but the number of members of this new group is expected to be higher, with amplitudes below our mmag detection limit.
    [Show full text]
  • August 10Th 2019 August 2019 7:00Pm at the Herrett Center for Arts & Science College of Southern Idaho
    Snake River Skies The Newsletter of the Magic Valley Astronomical Society www.mvastro.org Membership Meeting MVAS President’s Message August 2019 Saturday, August 10th 2019 7:00pm at the Herrett Center for Arts & Science College of Southern Idaho. Colleagues, Public Star Party follows at the I hope you found the third week of July exhilarating. The 50th Anniversary of the first Centennial Observatory moon landing was the common theme. I capped my observance by watching the C- SPAN replay of the CBS broadcast. It was not only exciting to watch the landing, but Club Officers to listen to Walter Cronkite and Wally Schirra discuss what Neil Armstrong and Buzz Robert Mayer, President Aldrin was relaying back to us. It was fascinating to hear what we have either accepted or rejected for years come across as something brand new. Hearing [email protected] Michael Collins break in from his orbit above in the command module also reminded me of the major role he played and yet others in the past have often overlooked – Gary Leavitt, Vice President fortunately, he is now receiving the respect he deserves. If you didn’t catch that, [email protected] then hopefully you caught some other commemoration, such as Turner Classic Movies showing For All Mankind, a spellbinding documentary of what it was like for Dr. Jay Hartwell, Secretary all of the Apollo astronauts who made it to the moon. Jim Tubbs, Treasurer / ALCOR For me, these moments of commemoration made reading the moon landing’s [email protected] anniversary issue from the Association of Lunar and Planetary Observers (ALPO) 208-404-2999 come to life as they wrote about the features these astronauts were examining – including the little craters named after the three astronauts.
    [Show full text]
  • Arxiv:2012.09981V1 [Astro-Ph.SR] 17 Dec 2020 2 O
    Contrib. Astron. Obs. Skalnat´ePleso XX, 1 { 20, (2020) DOI: to be assigned later Flare stars in nearby Galactic open clusters based on TESS data Olga Maryeva1;2, Kamil Bicz3, Caiyun Xia4, Martina Baratella5, Patrik Cechvalaˇ 6 and Krisztian Vida7 1 Astronomical Institute of the Czech Academy of Sciences 251 65 Ondˇrejov,The Czech Republic(E-mail: [email protected]) 2 Lomonosov Moscow State University, Sternberg Astronomical Institute, Universitetsky pr. 13, 119234, Moscow, Russia 3 Astronomical Institute, University of Wroc law, Kopernika 11, 51-622 Wroc law, Poland 4 Department of Theoretical Physics and Astrophysics, Faculty of Science, Masaryk University, Kotl´aˇrsk´a2, 611 37 Brno, Czech Republic 5 Dipartimento di Fisica e Astronomia Galileo Galilei, Vicolo Osservatorio 3, 35122, Padova, Italy, (E-mail: [email protected]) 6 Department of Astronomy, Physics of the Earth and Meteorology, Faculty of Mathematics, Physics and Informatics, Comenius University in Bratislava, Mlynsk´adolina F-2, 842 48 Bratislava, Slovakia 7 Konkoly Observatory, Research Centre for Astronomy and Earth Sciences, H-1121 Budapest, Konkoly Thege Mikl´os´ut15-17, Hungary Received: September ??, 2020; Accepted: ????????? ??, 2020 Abstract. The study is devoted to search for flare stars among confirmed members of Galactic open clusters using high-cadence photometry from TESS mission. We analyzed 957 high-cadence light curves of members from 136 open clusters. As a result, 56 flare stars were found, among them 8 hot B-A type ob- jects. Of all flares, 63 % were detected in sample of cool stars (Teff < 5000 K), and 29 % { in stars of spectral type G, while 23 % in K-type stars and ap- proximately 34% of all detected flares are in M-type stars.
    [Show full text]
  • On the Metallicity of Open Clusters II. Spectroscopy
    Astronomy & Astrophysics manuscript no. OCMetPaper2 c ESO 2013 November 12, 2013 On the metallicity of open clusters II. Spectroscopy U. Heiter1, C. Soubiran2, M. Netopil3, and E. Paunzen4 1 Institutionen för fysik och astronomi, Uppsala universitet, Box 516, 751 20 Uppsala, Sweden e-mail: [email protected] 2 Université Bordeaux 1, CNRS, Laboratoire d’Astrophysique de Bordeaux UMR 5804, BP 89, 33270 Floirac, France 3 Institut für Astrophysik der Universität Wien, Türkenschanzstrasse 17, 1180 Wien, Austria 4 Department of Theoretical Physics and Astrophysics, Masaryk University, Kotlárskᡠ267/2, 611 37 Brno, Czech Republic Received 29 August 2013 / Accepted 20 October 2013 ABSTRACT Context. Open clusters are an important tool for studying the chemical evolution of the Galactic disk. Metallicity estimates are available for about ten percent of the currently known open clusters. These metallicities are based on widely differing methods, however, which introduces unknown systematic effects. Aims. In a series of three papers, we investigate the current status of published metallicities for open clusters that were derived from a variety of photometric and spectroscopic methods. The current article focuses on spectroscopic methods. The aim is to compile a comprehensive set of clusters with the most reliable metallicities from high-resolution spectroscopic studies. This set of metallicities will be the basis for a calibration of metallicities from different methods. Methods. The literature was searched for [Fe/H] estimates of individual member stars of open clusters based on the analysis of high-resolution spectra. For comparison, we also compiled [Fe/H] estimates based on spectra with low and intermediate resolution.
    [Show full text]
  • UBVRI-KC Photometry of NGC~ 2323 and NGC~ 2539 Open Clusters
    J. Astrophys. Astr. (0000) 000: #### DOI UBV(RI)KC Photometry of NGC 2323 and NGC 2539 Open Clusters Inci˙ Akkaya Oralhan1,*, Raul´ Michel2, William J. Schuster2,Yuksel¨ Karatas¸3,Yonca Karslı1 and Carlos Chavarr´ıa2 1Erciyes University, Astronomy and Space Science Observatory, TR-38039, Kayseri, Turkey 2Observatorio Astronomico Nacional, Universidad Nacional Autonoma de Mexico,´ Apartado Postal 106, C.P. 22800, Ensenada, B.C., Mexico.´ 3Department of Astronomy and Space Sciences, Science Faculty, Istanbul University, 34119, Istanbul, Turkey. *Corresponding author. E-mail: [email protected] MS received ?? ?? 2019; accepted ?? ?? 2019 Abstract. The open clusters NGC 2323 and NGC 2539 have been analysed using CCD UBV(RI)KC photo- metric data, observed at the San Pedro Martir´ Observatory. Cluster memberships have been determined with the proper motion and parallax measures from the GaiaDR2 astrometric data release. Photometric metal and heavy element abundances have been obtained as ([M=H]; Z) = (−0:10; 0:012) (NGC 2323) and (−0:31; 0:007) (NGC 2539), from the δ(U–B) technique in the two colour diagrams, which are used to select the appropriate PARSEC isochrones. The estimated reddening of NGC 2323 is E(B-V)=0.23±0.04 using 11 early type stars. For NGC 2539, we find E(B-V)= 0.02±0.06. For (B–V) colour, distance moduli and distances for NGC 2323 and NGC 2539 are de- rived as (V0–MV, d (pc)) = (10.00±0.10, 1000±50) and (V0–MV, d (pc)) = (10.00±0.04, 1000±20), respectively. The median GaiaDR2 distance d=1000±140 pc ($=0.998±0.136 mas) for the likely members of NGC 2323 is in concordance with its four colour photometric distances 910–1000 pc.
    [Show full text]
  • Arxiv:0804.4630V1 [Astro-Ph] 29 Apr 2008 I Ehnv20;Ficao 06) Ti Nti Oeas Role This in Is It 2006A)
    DRAFT VERSION NOVEMBER 9, 2018 Preprint typeset using LATEX style emulateapj v. 05/04/06 OPEN CLUSTERS AS GALACTIC DISK TRACERS: I. PROJECT MOTIVATION, CLUSTER MEMBERSHIP AND BULK THREE-DIMENSIONAL KINEMATICS PETER M. FRINCHABOY1,2,3 AND STEVEN R. MAJEWSKI2 Department of Astronomy, University of Virginia, P.O. Box 400325, Charlottesville, VA 22904-4325, USA Draft version November 9, 2018 ABSTRACT We have begun a survey of the chemical and dynamical properties of the Milky Way disk as traced by open star clusters. In this first contribution, the general goals of our survey are outlined and the strengths and limita- tions of using star clusters as a Galactic disk tracer sample are discussed. We also present medium resolution (R 15,0000) spectroscopy of open cluster stars obtained with the Hydra multi-object spectrographs on the Cerro∼ Tololo Inter-American Observatory 4-m and WIYN 3.5-m telescopes. Here we use these data to deter- mine the radial velocities of 3436 stars in the fields of open clusters within about 3 kpc, with specific attention to stars having proper motions in the Tycho-2 catalog. Additional radial velocity members (without Tycho-2 proper motions) that can be used for future studies of these clusters were also identified. The radial velocities, proper motions, and the angular distance of the stars from cluster center are used to derive cluster member- ship probabilities for stars in each cluster field using a non-parametric approach, and the cluster members so-identified are used, in turn, to derive the reliable bulk three-dimensional motion for 66 of 71 targeted open clusters.
    [Show full text]
  • A Wild Animal by Magda Streicher
    deepsky delights Lupus a wild animal by Magda Streicher [email protected] Image source: Stellarium There is a true story behind this month’s constellation. “Star friends” as I call them, below in what might be ‘ground zero’! regularly visit me on the farm, exploiting “What is that?” Tim enquired in a brave the ideal conditions for deep-sky stud- voice, “It sounds like a leopard catching a ies and of course talking endlessly about buck”. To which I replied: “No, Timmy, astronomy. One winter’s weekend the it is much, much more dangerous!” Great Coopers from Johannesburg came to visit. was our relief when the wrestling match What a weekend it turned out to be. For started disappearing into the distance. The Tim it was literally heaven on earth in the altercation was between two aardwolves, dark night sky with ideal circumstances to wrestling over a bone or a four-legged study meteors. My observatory is perched lady. on top of a building in an area consisting of mainly Mopane veld with a few Baobab The Greeks and Romans saw the constel- trees littered along the otherwise clear ho- lation Lupus as a wild animal but for the rizon. Ascending the steps you are treated Arabians and Timmy it was their Leopard to a breathtaking view of the heavens in all or Panther. This very ancient constellation their glory. known as Lupus the Wolf is just east of Centaurus and south of Scorpius. It has no That Saturday night Tim settled down stars brighter than magnitude 2.6.
    [Show full text]
  • The Gaia-ESO Survey: Membership Probabilities for Stars in 32 Open Clusters from 3D Kinematics
    MNRAS 496, 4701–4716 (2020) doi:10.1093/mnras/staa1749 Advance Access publication 2020 June 19 The Gaia-ESO Survey: membership probabilities for stars in 32 open clusters from 3D kinematics R. J. Jackson,1‹ R. D. Jeffries,1‹ N. J. Wright,1 S. Randich,2 G. Sacco,2 E. Pancino ,2 T. Cantat-Gaudin,3 G. Gilmore,4 A. Vallenari,5 T. Bensby,6 A. Bayo,7,10 M. T. Costado,8 E. Franciosini,2 A. Gonneau,4 A. Hourihane,4 J. Lewis,4 L. Monaco,9 L. Morbidelli2 and C. Worley4 Downloaded from https://academic.oup.com/mnras/article/496/4/4701/5859956 by Universidad Andres Bello user on 27 August 2021 1Astrophysics Group, Keele University, Keele, Staffordshire ST5 5BG, UK 2INAF – Osservatorio Astrofisco di Arcetri, Largo E. Fermi, 5, I-50125 Firenze, Italy 3Institut de Ciencies` del Cosmos, Universitat de Barcelona (IEEC-UB), Mart´ı i Franques` 1, E-08028 Barcelona, Spain 4Institute of Astronomy, Cambridge University, Madingley Road, Cambridge CB3 0H, UK 5INAF – Osservatorio Astronomico di Padova, Vicolo dell’Osservatorio 5, I-35122 Padova, Italy 6Lund Observatory, Department of Astronomy and Theoretical Physics, Box 43, SE-221 00 Lund, Sweden 7Instituto de F´ısica y Astronom´ıa, Facultad de Ciencias, Universidad de Valpara´ıso, Av. Gran Bretana˜ 1111, 5030 Casilla, Valpara´ıso, Chile 8Departamento de Didactica,´ Universidad de Cadiz,´ E-11519 Puerto Real, Cadiz,´ Spain 9Departamento de Ciencias Fisicas, Universidad Andres Bello, Fernandez Concha 700, Las Condes, Santiago, Chile 10Nucleo´ Milenio Formacion´ Planetaria - NPF, Universidad de Valpara´ı Avenida Errazuriz´ 1834, Valpara´ıso, Chile Accepted 2020 June 12.
    [Show full text]
  • A Photometric and Spectroscopic Study of the Southern Open Clusters Pismis 18, Pismis 19, Ngc 6005, and Ngc 6253 Andre S E
    THE ASTRONOMICAL JOURNAL, 116:801È812, 1998 August ( 1998. The American Astronomical Society. All rights reserved. Printed in U.S.A. A PHOTOMETRIC AND SPECTROSCOPIC STUDY OF THE SOUTHERN OPEN CLUSTERS PISMIS 18, PISMIS 19, NGC 6005, AND NGC 6253 ANDRE S E. PIATTI1,2 AND JUAN J. CLARIA 2 Observatorio Astrono mico, Universidad Nacional de Co rdoba, Laprida 854, 5000 Co rdoba, Argentina; andres=oac.uncor.edu, claria=oac.uncor.edu EDUARDO BICA2 Departamento de Astronomia, Universidade Federal do Rio Grande do Sul, C.P. 15051, Porto Alegre, 91500-970, RS, Brazil; bica=if.ufrgs.br DOUG GEISLER Kitt Peak National Observatory, National Optical Astronomy Observatories, P.O. Box 26732, Tucson, AZ 85726; doug=noao.edu AND DANTE MINNITI Lawrence Livermore National Laboratory, L-413, P.O. Box 808, Livermore, CA 94550; dminniti=igpp.llnl.gov Received 1997 October 3; revised 1998 April 24 ABSTRACT CCD observations in the B, V , and I passbands have been used to generate color-magnitude diagrams (CMDs) for the southern open cluster candidates Pismis 18, Pismis 19, and NGC 6005, as well as for the old open cluster NGC 6253. The sample consists of about 1550 stars reaching down to V D 19 mag. From analysis of the CMDs, the physical reality of the three cluster candidates is conÐrmed and their reddening, distance, and age are derived, as well as those of NGC 6253. In addition, integrated spectra for Pismis 18, Pismis 19, and NGC 6253 covering a range from 3500 to 9200A were obtained. The reddening, age, and metallicity of these three clusters were derived from Balmer and Ca II triplet equiva- lent widths by comparing the observed spectra with those of template clusters.
    [Show full text]
  • February 14, 2015 7:00Pm at the Herrett Center for Arts & Science Colleagues, College of Southern Idaho
    Snake River Skies The Newsletter of the Magic Valley Astronomical Society www.mvastro.org Membership Meeting President’s Message Saturday, February 14, 2015 7:00pm at the Herrett Center for Arts & Science Colleagues, College of Southern Idaho. Public Star Party Follows at the It’s that time of year when obstacles appear in the sky. In particular, this year is Centennial Obs. loaded with fog. It got in the way of letting us see the dance of the Jovian moons late last month, and it’s hindered our views of other unique shows. Still, members Club Officers reported finding enough of a clear sky to let us see Comet Lovejoy, and some great photos by members are popping up on the Facebook page. Robert Mayer, President This month, however, is a great opportunity to see the benefit of something [email protected] getting in the way. Our own Chris Anderson of the Herrett Center has been using 208-312-1203 the Centennial Observatory’s scope to do work on occultation’s, particularly with asteroids. This month’s MVAS meeting on Feb. 14th will give him the stage to Terry Wofford, Vice President show us just how this all works. [email protected] The following weekend may also be the time the weather allows us to resume 208-308-1821 MVAS-only star parties. Feb. 21 is a great window for a possible star party; we’ll announce the location if the weather permits. However, if we don’t get that Gary Leavitt, Secretary window, we’ll fall back on what has become a MVAS tradition: Planetarium night [email protected] at the Herrett Center.
    [Show full text]
  • Open Clusters in Gaia
    Sede Amministrativa: Università degli Studi di Padova Dipartimento di Fisica e Astronomia “G. Galilei” Corso di Dottorato di Ricerca in Astronomia Ciclo XXX OPEN CLUSTERS IN GAIA ERA Coordinatore: Ch.mo Prof. Giampaolo Piotto Supervisore: Dr.ssa Antonella Vallenari Dottorando: Francesco Pensabene i Abstract Context. Open clusters (OCs) are optimal tracers of the Milky Way disc. They are observed at every distance from the Galactic center and their ages cover the entire lifespan of the disc. The actual OC census contain more than 3000 objects, but suffers of incom- pleteness out of the solar neighborhood and of large inhomogeneity in the parameter deter- minations present in literature. Both these aspects will be improved by the on-going space mission Gaia . In the next years Gaia will produce the most precise three-dimensional map of the Milky Way by surveying other than 1 billion of stars. For those stars Gaia will provide extremely precise measure- ment of proper motions, parallaxes and brightness. Aims. In this framework we plan to take advantage of the first Gaia data release, while preparing for the coming ones, to: i) move the first steps towards building a homogeneous data base of OCs with the high quality Gaia astrometry and photometry; ii) build, improve and test tools for the analysis of large sample of OCs; iii) use the OCs to explore the prop- erties of the disc in the solar neighborhood. Methods and Data. Using ESO archive data, we analyze the photometry and derive physical parameters, comparing data with synthetic populations and luminosity functions, of three clusters namely NGC 2225, NGC 6134 and NGC 2243.
    [Show full text]
  • A Basic Requirement for Studying the Heavens Is Determining Where In
    Abasic requirement for studying the heavens is determining where in the sky things are. To specify sky positions, astronomers have developed several coordinate systems. Each uses a coordinate grid projected on to the celestial sphere, in analogy to the geographic coordinate system used on the surface of the Earth. The coordinate systems differ only in their choice of the fundamental plane, which divides the sky into two equal hemispheres along a great circle (the fundamental plane of the geographic system is the Earth's equator) . Each coordinate system is named for its choice of fundamental plane. The equatorial coordinate system is probably the most widely used celestial coordinate system. It is also the one most closely related to the geographic coordinate system, because they use the same fun­ damental plane and the same poles. The projection of the Earth's equator onto the celestial sphere is called the celestial equator. Similarly, projecting the geographic poles on to the celest ial sphere defines the north and south celestial poles. However, there is an important difference between the equatorial and geographic coordinate systems: the geographic system is fixed to the Earth; it rotates as the Earth does . The equatorial system is fixed to the stars, so it appears to rotate across the sky with the stars, but of course it's really the Earth rotating under the fixed sky. The latitudinal (latitude-like) angle of the equatorial system is called declination (Dec for short) . It measures the angle of an object above or below the celestial equator. The longitud inal angle is called the right ascension (RA for short).
    [Show full text]