DOCSLIB.ORG

Discovering and Characterizing Embedded Stellar Clusters in the Near-Infrared

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Discovering and Characterizing Embedded Stellar Clusters in the Near-Infrared Discovering and Characterizing Embedded Stellar Clusters in the Near-Infrared Item Type text; Electronic Dissertation Authors Leistra, Andrea Publisher The University of Arizona. Rights Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author. Download date 28/09/2021 19:31:15 Link to Item http://hdl.handle.net/10150/193801 DISCOVERING AND CHARACTERIZING EMBEDDED STELLAR CLUSTERS IN THE NEAR-INFRARED by Andrea Lynn Leistra A Dissertation Submitted to the Faculty of the DEPARTMENT OF ASTRONOMY In Partial Fulfillment of the Requirements For the Degree of DOCTOR OF PHILOSOPHY In the Graduate College THE UNIVERSITY OF ARIZONA 2 0 0 6 2 THE UNIVERSITY OF ARIZONA GRADUATE COLLEGE As members of the Dissertation Committee, we certify that we have read the dissertation prepared by Andrea Lynn Leistra entitled “Discovering and Charac- terizing Embedded Stellar Clusters in the Near-Infrared” and recommend that it be accepted as fulfilling the dissertation requirement for the Degree of Doctor of Philosophy. Date: July 10, 2006 James Liebert Date: July 10, 2006 Philip Massey Date: July 10, 2006 George Rieke Date: July 10, 2006 Erick Young Final approval and acceptance of this dissertation is contingent upon the candi- date's submission of the final copies of the dissertation to the Graduate College. I hereby certify that I have read this dissertation prepared under my direction and recommend that it be accepted as fulfilling the dissertation requirement. Date: July 10, 2006 Dissertation Director: James Liebert 3 STATEMENT BY AUTHOR This dissertation has been submitted in partial fulfillment of requirements for an advanced degree at The University of Arizona and is deposited in the Univer- sity Library to be made available to borrowers under rules of the Library. Brief quotations from this dissertation are allowable without special permis- sion, provided that accurate acknowledgment of source is made. Requests for permission for extended quotation from or reproduction of this manuscript in whole or in part may be granted by the head of the major department or the Dean of the Graduate College when in his or her judgment the proposed use of the material is in the interests of scholarship. In all other instances, however, permission must be obtained from the author. SIGNED: Andrea Lynn Leistra 4 ACKNOWLEDGMENTS First, special thanks to my advisor, Jim Liebert. I've learned a great deal from Jim, and I'm always amazed at how much he knows, even outside his main ar- eas of research. Thanks also to my main collaborators, Angela Cotera and Phil Massey, for invaluable scientific insight and help with how to be a good scientist. Second, thanks to the astronomers whose instruments and telescope access made my research possible: Don McCarthy for the use of PISCES and Michael Burton for agreeing to collaborate to allow me to use the Anglo-Australian Telescope. Chris Tinney's instrument support for IRIS2 was invaluable. Thanks to all the astronomers whose comments helped make this thesis stronger, especially Margaret Hanson, Mike Meyer, and the referees for the papers that ap- pear as Chapters 2 and 3. Thanks to the current and former grad students of Steward Observatory who helped with computer and science issues, as well with keeping my sanity in- tact, especially Jeremy Bailin, Kris Eriksen, Craig Kulesa, Chris Groppi, Jackie Monkiewicz, and Jane Rigby. Many thanks to the Steward people who make everything work: Erin Carlson, Michelle Cournoyer, Catalina Diaz-Silva, Joy Facio, Jeff Fookson, and Neal Lau- ver. Thanks also to all the telescope operators at the 90”, the MMT, and the AAT for keeping things running smoothly and fixing them when they didn't. And finally, thanks to everyone who encouraged my interest in science in general and astronomy in particular before I ever got here. Most especially my parents, but also the great teachers I've had over the years from grade school through col- lege. They may never see this thesis but it wouldn't have been written without them. 5 DEDICATION For my partner, Jane Rigby, who kept me going. 6 TABLE OF CONTENTS LIST OF FIGURES . 8 LIST OF TABLES . 11 ABSTRACT . 13 CHAPTER 1 INTRODUCTION : : : : : : : : : : : : : : : : : : : : : : : : : : 15 CHAPTER 2 DISCOVERING INFRARED EMBEDDED CLUSTERS WITH 2MASS 24 2.1 Introduction . 24 2.2 Searching the 2MASS Catalog . 26 2.2.1 Algorithm . 26 2.2.2 Targeted Search . 27 2.2.3 Full-Sky Search . 28 2.3 Analysis . 35 2.3.1 False Cluster Detections . 35 2.3.2 Missed Clusters & Completeness of the Sample . 36 2.3.3 Embedded Cluster Candidates . 41 2.4 Limitations of Automated Searches and Implications for Future Studies . 43 2.5 Followup Observations of Cluster Candidates: False Detections . 45 2.5.1 DB11 Cluster Candidate . 46 2.5.2 DB41 Cluster Candidate . 52 2.6 Finding Embedded Clusters: Conclusions . 56 CHAPTER 3 SOUTHERN 2MASS-SELECTED YOUNG STELLAR CLUSTERS: PHOTOMETRY, SPECTROSCOPY, AND THE INITIAL MASS FUNCTION : : 57 3.1 INTRODUCTION . 57 3.2 OBSERVATIONS & DATA REDUCTION . 60 3.3 Analysis . 64 3.3.1 Spectroscopy . 64 3.3.2 Photometry . 79 3.4 The K Band Luminosity Function and the Initial Mass Function . 95 3.4.1 The G305.3+0.2 Cluster . 97 3.4.2 The KLF for the G353.4-0.36 cluster . 106 3.5 Summary . 108 CHAPTER 4 NORTHERN 2MASS-SELECTED YOUNG STELLAR CLUSTERS: PHOTOMETRY AND THE INITIAL MASS FUNCTION : : : : : : : : : : : : 110 4.1 INTRODUCTION . 110 4.2 OBSERVATIONS & DATA REDUCTION . 112 7 TABLE OF CONTENTS — Continued 4.3 Analysis . 114 4.3.1 Sh 2-217 Cluster . 114 4.3.2 IRAS 06058+2158 Cluster . 125 4.3.3 IRAS 06104+1524 Cluster . 128 4.3.4 Sh 2-288 . 136 4.3.5 Comparison of Methods for IMF Determination . 138 4.4 Summary . 142 CHAPTER 5 CONCLUSIONS AND FUTURE DIRECTIONS : : : : : : : : : : : 145 5.1 The Initial Mass Function of Embedded Stellar Clusters . 145 5.2 Discovering Embedded Stellar Clusters using 2MASS: Complete- ness and Distribution . 149 REFERENCES : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 153 8 LIST OF FIGURES 2.1 2MASS Ks image of an “extinction hole” detected as a cluster can- didate by the automated search. 37 2.2 2MASS Ks image of a sparse-field overdensity detected as a cluster by the automated search . 38 2.3 2MASS Ks image of a galaxy detected as a cluster candidate by the automated search. 39 2.4 Distribution of embedded cluster candidates in galactic coordinates. 42 2.5 Major axis (in arcmin) of cluster candidates as determined from 2MASS images. 44 2.6 80×80 K-band image of the DB11 cluster candidate from IRIS2/AAT. 47 2.7 80×80 K-band image of the DB41 cluster candidate from IRIS2/AAT. 48 2.8 All sources detected in the “field region” for the DB11 cluster can- didate. 49 2.9 All sources detected in the “cluster region” for the DB11 cluster candidate. 50 2.10 Statistically-corrected “cluster region” sources for the DB11 cluster candidate. 51 2.11 All sources detected in the “field region” for the DB41 cluster can- didate. 53 2.12 All sources detected in the “field region” for the DB41 cluster can- didate. 54 2.13 Statistically-corrected “cluster region” sources for the DB41 cluster candidate. 55 3.1 JHK image of the G305+00.2 cluster. 62 3.2 JHK image of the G353.4-0.2 cluster. 63 3.3 Spectra for the cluster stars in the G305.3+0.2 cluster. 67 3.4 Spectroscopically classified sources marked on the G305.3+0.2 clus- ter. 68 3.5 K-band image of the G305.3+0.2 cluster region with 8 µm contours from the MSX mission. 70 3.6 Spectra for sources in the G353.4-0.36 cluster. 75 3.7 Maser positions from the literature overlaid on the G353.4-0.36 clus- ter K-band image. 76 3.8 Nebular spectrum from the G353.4-0.36 cluster region. 77 3.9 K vs H-K for the G305.3+0.2 cluster region. 88 LIST OF FIGURES — CONTINUED 9 3.10 K vs H-K for a randomly selected control field for G305.3+0.2, with the same area as the cluster field. 89 3.11 Corrected K vs. H-K for the G305.3+0.2 cluster region with ZAMS overplotted. 91 3.12 Corrected J − H vs. H − K for the G305.3+0.2 cluster region. 93 3.13 K vs H-K for the G353.4-0.36 cluster region. 96 3.14 Completeness fraction determined by artificial-star tests for the G305.3+0.2 cluster region. 98 3.15 K-band luminosity functions for G305.3+0.2 cluster (solid) and field (dashed), normalized to the same total number of stars. 99 3.16 Completeness-corrected K-band luminosity function for G305.3+0.2 cluster. 100 3.17 The completeness-corrected IMF for the G305.3+0.2 cluster. 104 3.18 The raw (solid line) and completeness-corrected (dashed line) KLF for the G353.4-0.36 cluster. 107 4.1 K-band image of the Sh 2-217 cluster center (North=up, East=left). 115 4.2 K vs. H − K color-magnitude diagram for the cluster near Sh2-217. 118 4.3 Statistically-corrected K vs. H − K color-magnitude diagram for the cluster near Sh2-217. 119 4.4 K luminosity function for the Sh2-217 cluster. 120 4.5 K vs.
Load more

Recommended publications
  • The Low-Mass Content of the Massive Young Star Cluster RCW&Thinsp
    MNRAS 471, 3699–3712 (2017) doi:10.1093/mnras/stx1906 Advance Access publication 2017 July 27 The low-mass content of the massive young star cluster RCW 38 Koraljka Muziˇ c,´ 1,2‹ Rainer Schodel,¨ 3 Alexander Scholz,4 Vincent C. Geers,5 Ray Jayawardhana,6 Joana Ascenso7,8 and Lucas A. Cieza1 1Nucleo´ de Astronom´ıa, Facultad de Ingenier´ıa, Universidad Diego Portales, Av. Ejercito 441, Santiago, Chile 2SIM/CENTRA, Faculdade de Ciencias de Universidade de Lisboa, Ed. C8, Campo Grande, P-1749-016 Lisboa, Portugal 3Instituto de Astrof´ısica de Andaluc´ıa (CSIC), Glorieta de la Astronoma´ s/n, E-18008 Granada, Spain 4SUPA, School of Physics & Astronomy, St. Andrews University, North Haugh, St Andrews KY16 9SS, UK 5UK Astronomy Technology Centre, Royal Observatory Edinburgh, Blackford Hill, Edinburgh EH9 3HJ, UK 6Faculty of Science, York University, 355 Lumbers Building, 4700 Keele Street, Toronto, ON M3J 1P2, Canada 7CENTRA, Instituto Superior Tecnico, Universidade de Lisboa, Av. Rovisco Pais 1, P-1049-001 Lisbon, Portugal 8Departamento de Engenharia F´ısica da Faculdade de Engenharia, Universidade do Porto, Rua Dr. Roberto Frias, s/n, P-4200-465 Porto, Portugal Accepted 2017 July 24. Received 2017 July 24; in original form 2017 February 3 ABSTRACT RCW 38 is a deeply embedded young (∼1 Myr), massive star cluster located at a distance of 1.7 kpc. Twice as dense as the Orion nebula cluster, orders of magnitude denser than other nearby star-forming regions and rich in massive stars, RCW 38 is an ideal place to look for potential differences in brown dwarf formation efficiency as a function of environment.
    [Show full text]
  • First Embedded Cluster Formation in California Molecular Cloud
    DRAFT VERSION MARCH 24, 2020 Typeset using LATEX twocolumn style in AASTeX62 First embedded cluster formation in California molecular cloud JIN-LONG XU,1, 2 YE XU,3 PENG JIANG,1, 2 MING ZHU,1, 2 XIN GUAN,1, 2 NAIPING YU,1 GUO-YIN ZHANG,1 AND DENG-RONG LU3 1National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100101, China 2CAS Key Laboratory of FAST, National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100101, China 3Purple Mountain Observatory, Chinese Academy of Sciences, Nanjing 210008, China (Received xx xx, 2019; Revised xx xx, 2019; Accepted xx xx, 2019) ABSTRACT We performed a multi-wavelength observation toward LkHα 101 embedded cluster and its adjacent 850× 600 region. The LkHα 101 embedded cluster is the first and only one significant cluster in California molecular cloud (CMC). These observations have revealed that the LkHα 101 embedded cluster is just located at the projected intersectional region of two filaments. One filament is the highest-density section of the CMC, the other is a new identified filament with a low-density gas emission. Toward the projected intersection, we find the bridging features connecting the two filaments in velocity, and identify a V-shape gas structure. These agree with the scenario that the two filaments are colliding with each other. Using the Five-hundred-meter Aperture Spherical radio Telescope (FAST), we measured that the RRL velocity of the LkH 101 H II region is 0.5 km s−1, which is related to the velocity component of the CMC filament. Moreover, there are some YSOs distributed outside the intersectional region.
    [Show full text]
  • A Case Study of the Galactic H Ii Region M17 and Environs: Implications for the Galactic Star Formation Rate
    A Case Study of the Galactic H ii Region M17 and Environs: Implications for the Galactic Star Formation Rate by Matthew Samuel Povich A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy (Astronomy) at the University of Wisconsin – Madison 2009 ii Abstract Determinations of star formation rates (SFRs) in the Milky Way and other galaxies are fundamentally based on diffuse emission tracers of ionized gas, such as optical/near-infrared recombination lines, far- infrared continuum, and thermal radio continuum, that are sensitive only to massive OB stars. OB stars dominate the ionization of H II regions, yet they make up <1% of young stellar populations. SFRs therefore depend upon large extrapolations over the stellar initial mass function (IMF). The primary goal of this Thesis is to obtain a detailed census of the young stellar population associated with a bright Galactic H II region and to compare the resulting star formation history with global SFR tracers. The main SFR tracer considered is infrared continuum, since it can be used to derive SFRs in both the Galactic and extragalactic cases. I focus this study on M17, one of the nearest giant H II regions to the Sun (d =2.1kpc),fortwo reasons: (1) M17 is bright enough to serve as an analog of observable extragalactic star formation regions, and (2) M17 is associated with a giant molecular cloud complex, ∼100 pc in extent. The M17 complex is a significant star-forming structure on the Galactic scale, with a complicated star formation history. This study is multiwavelength in nature, but it is based upon broadband mid-infrared images from the Spitzer/GLIMPSE survey and complementary infrared Galactic plane surveys.
    [Show full text]
  • The Discovery of an Embedded Cluster of High-Mass Starts Near
    Clemson University TigerPrints Publications Physics and Astronomy Spring 4-10-2000 The Discovery of an Embedded Cluster of High- Mass Starts near SGR 1900+14 Frederick J. Vbra US Naval Observatory, Flagstaff tS ation Arne A. Henden US Naval Observatory, Flagstaff tS ation Christian B. Luginbuhl US Naval Observatory, Flagstaff tS ation Harry H. Guetter US Naval Observatory, Flagstaff tS ation Dieter H. Hartmann Department of Physics and Astronomy, Clemson University, [email protected] See next page for additional authors Follow this and additional works at: https://tigerprints.clemson.edu/physastro_pubs Recommended Citation Please use publisher's recommended citation. This Article is brought to you for free and open access by the Physics and Astronomy at TigerPrints. It has been accepted for inclusion in Publications by an authorized administrator of TigerPrints. For more information, please contact [email protected]. Authors Frederick J. Vbra, Arne A. Henden, Christian B. Luginbuhl, Harry H. Guetter, Dieter H. Hartmann, and Sylvio Klose This article is available at TigerPrints: https://tigerprints.clemson.edu/physastro_pubs/117 The Astrophysical Journal, 533:L17±L20, 2000 April 10 q 2000. The American Astronomical Society. All rights reserved. Printed in U.S.A. THE DISCOVERY OF AN EMBEDDED CLUSTER OF HIGH-MASS STARS NEAR SGR 1900114 Frederick J. Vrba, Arne A. Henden,1 Christian B. Luginbuhl, and Harry H. Guetter US Naval Observatory, Flagstaff Station, Flagstaff, AZ 86002-1149 Dieter H. Hartmann Department of Physics and Astronomy, Clemson University, Clemson, SC 29634-0978 and Sylvio Klose ThuÈringer Landessternwarte Tautenburg, D-07778 Tautenburg, Germany Received 1999 November 19; accepted 2000 February 23; published 2000 March 17 ABSTRACT Deep I-band imaging toI ¼ 26.5 of the soft gamma-ray repeater SGR 1900114 region has revealed a compact cluster of massive stars located only a few arcseconds from the fading radio source thought to be the location of the soft gamma-ray repeater (SGR).
    [Show full text]
  • The Youngest Globular Clusters
    To appear in Int’l Journal Mod. Physics D, vol 24 (2015) The Youngest Globular Clusters Sara Beck School of Physics and Astronomy and the Wise Observatory, Tel Aviv University, Ramat Aviv, Israel [email protected] ABSTRACT It is likely that all stars are born in clusters, but most clusters are not bound and disperse. None of the many protoclusters in our Galaxy are likely to develop into long-lived bound clusters. The Super Star Clusters (SSCs) seen in starburst galaxies are more massive and compact and have better chances of survival. The birth and early development of SSCs takes place deep in molecular clouds, and during this crucial stage the embedded clusters are invisible to optical or UV observations but are studied via the radio-infared supernebulae (RISN) they excite. We review observations of embedded clusters and identify RISN within 10 6 3 Mpc whose exciting clusters have ≈ 10 M⊙ or more in volumes of a few pc and which are likely to not only survive as bound clusters, but to evolve into objects as massive and compact as Galactic globulars. These clusters are distinguished by very high star formation efficiency η, at least a factor of 10 higher than the few percent seen in the Galaxy, probably due to violent disturbances their host galaxies have undergone. We review recent observations of the kinematics of the ionized gas in RISN showing outflows through low-density channels in arXiv:1412.0769v1 [astro-ph.GA] 2 Dec 2014 the ambient molecular cloud; this may protect the cloud from feedback by the embedded H ii region.
    [Show full text]
  • The Structure and Evolution of Young Stellar Clusters
    Allen et al.: Structure and Evolution of Young Stellar Clusters 361 The Structure and Evolution of Young Stellar Clusters Lori Allen, S. Thomas Megeath, Robert Gutermuth, Philip C. Myers, and Scott Wolk Harvard-Smithsonian Center for Astrophysics Fred C. Adams University of Michigan James Muzerolle and Erick Young University of Arizona Judith L. Pipher University of Rochester We examine the properties of embedded clusters within 1 kpc using new data from the Spitzer Space Telescope, as well as recent results from 2MASS and other groundbased near-infrared surveys. We use surveys of entire molecular clouds to understand the range and distribution of cluster membership, size, and surface density. The Spitzer data demonstrate clearly that there is a continuum of star-forming environments, from relative isolation to dense clusters. The number of members of a cluster is correlated with the cluster radius, such that the average sur- face density of clusters having a few to a thousand members varies by a factor of only a few. The spatial distributions of Spitzer-identified young stellar objects frequently show elongation, low density halos, and subclustering. The spatial distributions of protostars resemble the dis- tribution of dense molecular gas, suggesting that their morphologies result directly from the fragmentation of the natal gas. We also examine the effects of the cluster environments on star and planet formation. Although far-UV (FUV) and extreme-UV (EUV) radiation from massive stars can truncate disks in a few million years, fewer than half the young stars in our sample (embedded clusters within 1 kpc) are found in regions of strong FUV and EUV fields.
    [Show full text]
  • 10- and 17-F.Lm Test Images of the Galactic Centre: Massive Protostars Near Sgra*?
    spiral galaxies with the 64-m Parkes Ra­ at the approximate centre of the GA Wall - including the nearby Pavo, Indus dio Telescope. overdensity. Although very massive as a clusters below the Galactic plane and Within the Abell radius of the cluster cluster, its mass contributes only about the shallow overdensity in Vela above A3627, 109 velocities have so far been 10% of the total mass predicted for the the Galactic plane at 6000 km/so This reduced leading to a mean velocity of < Great Attractor. Hence, it is not "the" whole large-scale structure embodies what has been dubbed in 1987 the then vobs > =4882 km/s and a dispersion of 0' Great Attractor as such, but it is the = 903 km/so This puts the cluster weil prime candidate for being the hitherto unseen Great Attractor. within the predicted velocity range of the unidentified centre of this large-scale GA. The large dispersion of A3627 sug­ overdensity. This is supported by the re­ References gests it to be quite massive. Applying the cent analysis of the ROSAT PSPG data vi rial theorem yields a mass of - 5 x 1015 of A3627 by Böhringer et al. (1996) Böhringer, H., Neumann, D.M., Schindler, S., Mev, Le. a cluster on par with the rich, which finds this cluster to be the 6th & Kraan-Korteweg, R.C., 1996, ApJ, in press. well-known Goma cluster - yet consider­ brightest X-ray cluster in the sky for the Felenbok, P, Guerin, J., Fernandez, A., Cay­ ably c1oser. In fact, simulations show, ROSAT spectral band and confirms its atte, V., Balkowski, C., & Kraan-Korteweg, that if Goma were at the position of vi rial mass.
    [Show full text]
  • Orion and Cep OB3
    Mapping the Nearest High Mass Forming Clouds with Spitzer: Orion and Cep OB3 Cepheus OB3: 712 pc Orion: 414 pc Spitzer Surveys of Embedded Clusters and Giant Molecular Clouds in the Nearest Kiloparsec Thirty Young Stellar Cluster surveyed with < 0.25 sq degree fields as part of Guaranteed Time Observations Ten Molecular Cloud surveyed (several square degrees) as part of Guaranteed Time, Legacy, and General Observer programs. More clouds now being surveyed for the Gould Belt Program These surveys cover 90% of the known young stellar groups and clusters within 1 kpc My three questions: I. What are the demographics of star formation? II. Does environment matter? III. What is a cluster anyhow? Focus on massive star forming regions - why? I. Produce stars of all masses in a variety of environments II. Needed for comparison with other galaxies III. Our Sun formed in a massive star forming region Why Spitzer: Good for identifying and classifying sources Not good for finding core or star masses!!!!! The IRAC Survey of Orion A & B Lynds 1622 (Orion B) NGC 2068/2071 (Orion B) NGC 2024/2023 (Orion B) Orion Nebula Cluster (Orion A) L1641 (Orion A) Blue: Source detected at 3.6 and 4.5 microns Red: 12 CO map from Wilson et al. 90279 sources over 7 sq deg. Green: 2260 IR-excess sources L1641 Cloud Images L1641 South Cohen Kuhi N Red: 8 micron, Green: 4.5 micron, Blue:3.6 micron L1641 Cloud Images Small Green Circles: IR-ex sources, Big Green/Blue Circles: IRAC selected Protostars N Red: 8 micron, Green: 4.5 micron, Blue:3.6 micron L1641 Cloud Images
    [Show full text]
  • Star Clusters E NCYCLOPEDIA of a STRONOMY and a STROPHYSICS
    Star Clusters E NCYCLOPEDIA OF A STRONOMY AND A STROPHYSICS Star Clusters the Galaxy can be used to derive the cluster distance, independently of parallax measurements. Even a small telescope shows obvious local concentrations Afinal category of clusters has recently been identified of stars scattered around the sky. These star clusters are based on observations with infrared detectors. These are not chance juxtapositions of unrelated stars. They are, the embedded clusters—star clusters still in the process of instead, physically associated groups of stars, moving formation, and still embedded in the clouds out of which together through the Galaxy. The stars in a cluster are they formed. Because it is possible to see through the dust held together either permanently or temporarily by their much better at infrared wavelengths than in the optical, mutual gravitational attraction. these clusters have suddenly become observable. The classic, and best known, example of a star cluster Star clusters are of considerable astrophysical impor- is the Pleiades, visible in the evening sky in early winter tance to probe models of stellar evolution and dynamics, (from the northern hemisphere) as a group of 7–10 stars explore the star formation process, calibrate the extragalac- (depending on one’s eyesight). More than 600 Pleiades tic distance scale and most importantly to measure the age members have been identified telescopically. and evolution of the Galaxy. Clusters are generally distinguished as being either Definition of a star cluster—cluster catalogs GALACTIC OPEN CLUSTERS or GLOBULAR CLUSTERS, corresponding Just what is a cluster? How many stars does it take to to their appearance as seen through a moderate-aperture make a cluster? Trumpler in 1930 defined open clusters telescope.
    [Show full text]
  • Multi-Generation Massive Star-Formation in NGC3576
    A&A 504, 139–159 (2009) Astronomy DOI: 10.1051/0004-6361/200811358 & c ESO 2009 Astrophysics Multi-generation massive star-formation in NGC 3576 C. R. Purcell1,2, V. Minier3,4, S. N. Longmore2,5,6, Ph. André3,4,A.J.Walsh2,7,P.Jones2,8,F.Herpin9,10, T. Hill2,11,12, M. R. Cunningham2, and M. G. Burton2 1 Jodrell Bank Centre for Astrophysics, Alan Turing Building, School of Physics and Astronomy, The University of Manchester, Oxford Road, Manchester M13 9PL, UK e-mail: [email protected] 2 School of Physics, University of New South Wales, Sydney, NSW 2052, Australia 3 CEA, DSM, IRFU, Service d’Astrophysique, 91191 Gif-sur-Yvette, France 4 Laboratoire AIM, CEA/DSM - CNRS - Université Paris Diderot, IRFU/Service d’Astrophysique, CEA-Saclay, 91191 Gif-sur-Yvette, France 5 Harvard-Smithsonian Centre For Astrophysics, 60 Garden Street, Cambridge, MA, 02138, USA 6 CSIRO Australia Telescope National Facillity, PO Box 76, Epping, NSW 1710, Australia 7 Centre for Astronomy, James Cook University, Townsville, QLD 4811, Australia 8 Departmento de Astronoma, Universidad de Chile, Casilla 36-D, Santiago, Chile 9 Université de Bordeaux, Laboratoire d’Astrophysique de Bordeaux, 33000 Bordeaux, France 10 CNRS/INSU, UMR 5804, BP 89, 33271 Floirac Cedex, France 11 School of Physics, University of Exeter, Stocker Road, EX4 4QL, Exeter, UK 12 Leiden Observatory, Leiden University, PO BOX 9513, 2300 RA Leiden, the Netherlands Received 16 November 2008 / Accepted 3 July 2009 ABSTRACT Context. Recent 1.2-mm continuum observations have shown the giant H II region NGC 3576 to be embedded in the centre of an extended filamentary dust-cloud.
    [Show full text]
  • 10 MK GAS in M17 and the ROSETTE NEBULA: X-RAY FLOWS in GALACTIC H Ii REGIONS Leisa K
    The Astrophysical Journal, 593:874–905, 2003 August 20 # 2003. The American Astronomical Society. All rights reserved. Printed in U.S.A. 10 MK GAS IN M17 AND THE ROSETTE NEBULA: X-RAY FLOWS IN GALACTIC H ii REGIONS Leisa K. Townsley,1 Eric D. Feigelson,1,2 Thierry Montmerle,2 Patrick S. Broos,1 You-Hua Chu,3 and Gordon P. Garmire1 Received 2003 January 10; accepted 2003 April 28 ABSTRACT We present the first high spatial resolution X-ray images of two high-mass star forming regions, the Omega Nebula (M17) and the Rosette Nebula (NGC 2237–2246), obtained with the Chandra X-Ray Observatory Advanced CCD Imaging Spectrometer instrument. The massive clusters powering these H ii regions are resolved at the arcsecond level into more than 900 (M17) and 300 (Rosette) stellar sources similar to those seen in closer young stellar clusters. However, we also detect soft diffuse X-ray emission on parsec scales that is spatially and spectrally distinct from the point-source population. The diffuse emission has luminosity 33 À1 LX ’ 3:4 Â 10 ergs s in M17 with plasma energy components at kT ’ 0:13 and ’0.6 keV (1.5 and 7 32 À1 MK), while in Rosette it has LX ’ 6 Â 10 ergs s with plasma energy components at kT ’ 0:06 and ’0.8 keV (0.7 and 9 MK). This extended emission most likely arises from the fast O star winds thermalized either by wind-wind collisions or by a termination shock against the surrounding media. We establish that only a small portion of the wind energy and mass appears in the observed diffuse X-ray plasma; in these blister H ii regions, we suspect that most of it flows without cooling into the low-density interstellar medium.
    [Show full text]
  • Arxiv:1709.10448V1 [Astro-Ph.GA] 29 Sep 2017
    Draft version November 7, 2018 Preprint typeset using LATEX style AASTeX6 v. 1.0 THE STELLAR CONTENT OF THE INFALLING MOLECULAR CLUMP G286.21+0.17 M. Andersen Gemini Observatory, Casilla 603, La Serena, Chile P. J, Barnes Department of Astronomy, University of Florida, Gainesville, FL 32611, USA and School of Science and Technology, University of New England, Armidale NSW 2351, Australia J. C. Tan Departments of Physics & Astronomy, University of Florida, Gainesville, FL 32611, USA J. Kainulainen Max-Planck-Institut fur¨ Astronomie, Konigstuhl¨ 17, 69117 Heidelberg, Germany G. de Marchi Research & Scientific Support Department, ESA ESTEC, Keplerlaan 1, 2200 AG Noordwijk, The Netherlands ABSTRACT The early evolution during massive star cluster formation is still uncertain. Observing embedded clusters at their earliest stages of formation can provide insight into the spatial and temporal distribution of the stars and thus probe different star cluster formation models. We present near-infrared imaging of an 80×130 (5.4pc×8.7pc) region around the massive infalling clump G286.21+0.17 (also known as BYF73). The stellar content across the field is determined and photometry is derived in order to obtain stellar parameters for the cluster members. We find evidence for some sub-structure (on scales less than a pc diameter) within the region with apparently at least three different sub-clusters associated with the molecular clump based on differences in extinction and disk fractions. At the center of the clump we identify a deeply embedded sub-cluster. Near-infrared excess is detected for 39-44% in the two sub-clusters associated with molecular material and 27% for the exposed cluster.
    [Show full text]