DOCSLIB.ORG

TESTING MODELS of LOW-EXCITATION PHOTODISSOCIATION REGIONS with FAR-INFRARED OBSERVATIONS of REFLECTION NEBULAE Rolaine C

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
TESTING MODELS of LOW-EXCITATION PHOTODISSOCIATION REGIONS with FAR-INFRARED OBSERVATIONS of REFLECTION NEBULAE Rolaine C The Astrophysical Journal, 578:885–896, 2002 October 20 # 2002. The American Astronomical Society. All rights reserved. Printed in U.S.A. TESTING MODELS OF LOW-EXCITATION PHOTODISSOCIATION REGIONS WITH FAR-INFRARED OBSERVATIONS OF REFLECTION NEBULAE Rolaine C. Young Owl Department of Physics and Astronomy, University of California at Los Angeles, Mail Code 156205, Los Angeles, CA 90095-1562 Margaret M. Meixner1 and David Fong Department of Astronomy, University of Illinois, Urbana, IL 61801; [email protected], [email protected] Michael R. Haas NASA Ames Research Center, MS 245-6, Moffett Field, CA 94035-1000; [email protected] Alexander L. Rudolph1 Department of Physics, Harvey Mudd College, 301 East 12th Street, Claremont, CA 91711; [email protected] and A. G. G. M. Tielens Kapteyn Astronomical Institute, P.O. Box 800, 9700 AV Groningen, Netherlands; [email protected] Received 2001 August 2; accepted 2002 June 24 ABSTRACT This paper presents Kuiper Airborne Observatory observations of the photodissociation regions (PDRs) in nine reflection nebulae. These observations include the far-infrared atomic fine-structure lines of [O i]63 and 145 lm, [C ii] 158 lm, and [Si ii]35lm and the adjacent far-infrared continuum to these lines. Our analysis of these far-infrared observations provides estimates of the physical conditions in each reflection nebula. In our sample of reflection nebulae, the stellar effective temperatures are 10,000–30,000 K, the gas densities are 4  102 2  104 cmÀ3, the gas temperatures are 200–690 K, and the incident far-ultraviolet intensities are 300–8100 times the ambient interstellar radiation field strength (1:2  10À4 ergs cmÀ2 sÀ1 srÀ1). Our observations are compared with current theory for low-excitation PDRs. The [C ii] 158 lmto[Oi]63lm line ratio decreases with increasing incident far-ultraviolet intensity. This trend is due in part to a positive cor- relation of gas density with incident far-ultraviolet intensity. We show that this correlation arises from a bal- ance of pressure between the H ii region and the surrounding PDR. The [O i] 145 to 63 lm line ratio is higher (greater than 0.1) than predicted and is insensitive to variations in incident far-ultraviolet intensity and gas density. The stellar temperature has little effect on the heating efficiency that primarily had the value 3  10À3, within a factor of 2. This result agrees with a model that modifies the photoelectric heating theory to account for color temperature effects and predicts that the heating efficiencies would vary by less than a factor of 3 with the color temperature of the illuminating field. In addition to the single-pointing observations, an [O i]63lm scan was done across the molecular ridge of one of our sample reflection nebulae, NGC 1977. The result appears to support previous suggestions that the ionization front of this well-studied PDR is not purely edge-on. Subject headings: dust, extinction — infrared: ISM — ISM: lines and bands — reflection nebulae 1. INTRODUCTION Far-infrared (FIR) spectroscopy is a standard tool for studying the energetics of PDRs. FIR emission from the Photodissociation regions (PDRs) are regions of the fine-structure transitions of singly ionized atomic carbon interstellar medium in which the astrochemistry, structure, ([C ii] 158 m) and neutral atomic oxygen ([O i] 63 and 145 and physical processes are determined by the interaction of l lm) dominate the cooling of the PDR gas (Tielens & far-ultraviolet (FUV; h ¼ 6 13:6 eV) radiation with inter- Hollenbach 1985a, hereafter TH85). Because dust grains stellar gas and dust. PDR chemistry is dominated by FUV absorb FUV photons and reemit the energy in the FIR, the photodissociation of molecular bonds. Many important FIR continuum dust emission is proportional to the inci- chemical reactions in PDRs are initiated by FUV-pumped dent FUV flux. Hence, PDRs in massive star-forming vibrationally excited molecular hydrogen. Most of the inci- regions were productive sites for early FIR analysis because dent FUV flux (e99%) is absorbed by dust grains and ree- mitted in the infrared continuum. A small percentage of their very bright FIR line and continuum emission. The regions proximal to massive stars contain very dense (e105 (d1%) of the incident FUV photons cause the photoejec- cmÀ3) gas being illuminated by very strong UV fields tion of electrons from small dust grains and large molecules; G e 5 G these electrons then collisionally heat the PDR gas. Energy ( 0 10 , where 0 is in units of the average interstellar radiation field [ISRF] intensity of 1:2 10À4 ergs cmÀ2 sÀ1 balance is maintained by radiative cooling, predominantly  srÀ1; Habing 1968). FIR observations of massive star-form- through line emission in the far-infrared ( 30 200 lm). ing regions in Orion (Melnick, Gull, & Harwit 1979; Russell et al. 1980; Genzel & Stutzki 1989 and references therein; Stacey et al. 1993; Herrmann et al. 1997; Luhman et al. 1 NSF CAREER Fellow. 1997) and M17 SW (Storey, Watson, & Townes 1979; 885 886 YOUNG OWL ET AL. Vol. 578 Russell et al. 1981; Harris et al. 1987; Stutzki et al. 1988; illuminated by stars of spectral type ranging from B0 to Meixner et al. 1992) have been well modeled by the theory B9.5. The results are compared with predictions from the low- of dense PDRs (TH85; Sternberg & Dalgarno 1995; Hollen- density PDR theory of Hollenbach, Takahashi, & Tielens bach & Tielens 1997 and references therein). Because the (1991, hereafter HTT91) and from Spaans et al. (1994). 2 À2 5 sensitivity of FIR detectors has continued to increase stead- HTT91 modeled PDRs with density 10 cm < n0 < 10 À2 3 ily over the past 25 yr, it has become possible to extend the cm and incident FUV intensity 1 G0 10 . Spaans et FIR study of PDR energetics to the lower energy and lower al. (1994) modeled the effects of color temperature on the density regimes more commonly found in the interstellar energetics of PDRs around cool stars. medium (ISM). An initial focus was on the lower excitation PDRs found in reflection nebulae illuminated by early B stars (e.g., Makinen et al. 1985; Chokshi et al. 1988; Howe 2. OBSERVATIONS AND RESULTS et al. 1991; Steiman-Cameron, Haas, & Tielens 1997). Table 1 lists our target sample consisting of nine reflection Visual reflection nebulae are expected to be excellent can- nebulae illuminated by stars of spectral type ranging from didates for studying low-excitation PDRs. The stars illumi- B0 to B9.5 and effective temperatures 10,000–30,000 K. nating them are usually type B or later stars, compared to These sources were chosen to study the neutral work func- the O-type stars that illuminate massive star-forming tion and photoelectric yield of interstellar dust grains under regions. Because of the lower UV flux emitted from later- a range of low-excitation conditions. The sample consists of type stars, the ionization of atomic hydrogen is expected to six quiescent reflection nebulae, two reflection nebulae near balance recombination at a smaller Stro¨mgren radius than active star-forming regions (NGC 1333 and NGC 1977), for O-type stars, resulting in a smaller H ii region. More- and a reflection nebula illuminated by a post–asymptotic over, confusion caused by shock-excited [O i] is less likely, giant branch (AGB) star (Red Rectangle). The observations because the gas is more quiescent (i.e., the ionization shock were carried out in 1989 March and in 1992 January, June, fronts are weaker). Another advantage to observing reflec- and July using the 91 cm telescope of the Kuiper Airborne tion nebulae is that even though the IR surface brightness Observatory (KAO) with the facility cryogenic grating spec- may be lower than in very luminous high-density PDRs, trometer (CGS; Erickson et al. 1984). Each reflection nebula reflection nebulae PDRs are likely to be more spatially was observed at the peak in its FIR continuum emission. extended because of more gradual FUV attenuation, allow- Guiding was done using offsets D (arcsec), D (arcsec) from ing the structure to be spatially resolved. A reflection nebula the illuminating star. The exception was NGC 1333, where PDR is expected to be less dense by a factor of 10–104 than BD +30549 was the guide star instead of SVS 3, which the PDR in a massive star-forming region such as Orion, illuminates the FIR peak. 5 6 À3 which has n0 10 10 cm . Standard chopping techniques were employed through- In this paper, FIR analysis following the method in out; the chopper amplitude was 50–90, and the chopper Chokshi et al. (1988) is used to estimate the physical condi- rotation angle was individually selected for each source to tions in reflection nebula PDRs and to test how spectral type avoid background contamination (see Table 2). The detec- affects PDR energetics. FIR line and continuum observa- tor arrays were flat-fielded by dividing each spectrum by tions were conducted for a group of reflection nebulae that of a known calibration source (Table 2). In 1989 March TABLE 1 Target Reflection Nebulae for FIR Spectroscopy Offsets R.A. Decl. L* (arcsec) Distance a Name Illuminating Source (B1950.0) (B1950.0) Stellar (L ) (D , D) (pc) Reference NGC 1977........................................ 42 Ori 05 32 55.1 À04 52 11 B1 V 29,000 À176, À284.b 450 Æ 40 0.70 1, 2 À190, À283.c 450 Æ 40 0.70 1, 2 À249, À211.d 450 Æ 40 0.70 1, 2 NGC 2068........................................ HD 38563N 05 44 10.9 00 04 17 B2 IIÀIII 3,000 0, 0 500 Æ 100 0.65 3, 4, 5 IC 446 .............................................
Load more

Recommended publications
  • Midterm Results the Milky Way in the Infrared
    3/2/10 Lecture 13 : Midterm Results The Interstellar Medium and Cosmic Recycling A2020 Prof. Tom Megeath The Milk The Milky Way in the Infrared Way from Above (artist conception) The Milky Way appears to have a bar and four spiral arms. Star formation and hot blue stars concentrated in arms. View from the Earth: Edge On Infrared light penetrates the clouds and shows the entire galaxy 1 3/2/10 NGC 7331: the Milky Way’s Twins The Interstellar Medium The space between the stars is not empty, but filled with a very low density of matter in the form of: •Atomic hydrogen •Ionized hydrogen •Molecular Hydrogen •Cosmic Rays •Dust grains •Many other molecules (water, carbon monoxide, formaldehyde, methanol, etc) •Organic molecules like polycyclic aromatic hydrocarbons How do we know the gas is there? Review: Kirchoff Laws Remainder of the Lecture Foreground gas cooler, absorption 1. How we observe and study the interstellar medium 2. The multiwavelength Milky Way Absorbing gas hotter, 3. Cosmic Recycling emission lines (and (or cooler blackbody) blackbody) If foreground gas and emitting blackbody the same temperature: perfect blackbody (no lines) Picture from Nick Strobel’s astronomy notes: www.astronomynotes.com 2 3/2/10 Observing the ISM through Absorption Lines • We can determine the composition of interstellar gas from its absorption lines in the spectra of stars • 70% H, 28% He, 2% heavier elements in our region of Milky Way Picture from Nick Strobel’s astronomy notes: www.astronomynotes.com Emission Lines Emission Line Nebula M27 Emitted by atoms and ions in planetary and HII regions.
    [Show full text]
  • A Photometric Study of Be Stars Located in the Seismology fields of COROT
    A&A 476, 927–933 (2007) Astronomy DOI: 10.1051/0004-6361:20078252 & c ESO 2007 Astrophysics A photometric study of Be stars located in the seismology fields of COROT J. Gutiérrez-Soto1,2,J.Fabregat1,2,J.Suso3, M. Lanzara3, R. Garrido4, A.-M. Hubert2, and M. Floquet2 1 Observatorio Astronómico, Universidad de Valencia, edificio Institutos de Investigación, polígono la Coma, 46980 Paterna, Valencia, Spain e-mail: [email protected] 2 GEPI, Observatoire de Paris, CNRS, Université Paris Diderot; place Jules Janssen 92195 Meudon Cedex, France 3 GACE-ICMUV, edificio Institutos de Investigación, polígono la Coma, 46980 Paterna, Valencia, Spain 4 Instituto de Astrofísica de Andalucía (CSIC), calle Camino Bajo de Huétor, 24. 18008, Granada, Spain Received 10 July 2007 / Accepted 28 September 2007 ABSTRACT Context. In preparation for the COROT mission, an exhaustive photometric study of Be stars located in the seismology fields of the mission has been performed. The very precise and long-time-spanned photometric observations gathered by the COROT satellite will give important clues on the origin of the Be phenomenon. Aims. The aim of this work is to find short-period variable Be stars located in the seismology fields of COROT, and to study and characterise their pulsational properties. Methods. Light curves obtained at the Observatorio de Sierra Nevada, together with data from Hipparcos and ASAS-3 for a total of 84 Be stars, were analysed in order to search for short-term variations. We applied standard Fourier techniques and non-linear least-square fitting to the time series. Results. We found 7 multiperiodic, 21 mono-periodic and 26 non-variable Be stars.
    [Show full text]
  • Stars Chien-De Lee (李建德)1, Wen-Ping Chen (陳文屏)1, 2, and Sheng-Yuan Liu (呂聖元)3
    A&A 592, A130 (2016) Astronomy DOI: 10.1051/0004-6361/201628332 & c ESO 2016 Astrophysics Evolutionary status of isolated B[e] stars Chien-De Lee (Nú·)1, Wen-Ping Chen (s文O)1; 2, and Sheng-Yuan Liu (BVC)3 1 Graduate Institute of Astronomy, National Central University, 300 Jhongda Road, 32001 Jhongli, Taiwan e-mail: [email protected] 2 Department of Physics, National Central University, 300 Jhongda Road, 32001 Jhongli, Taiwan 3 Institute of Astronomy and Astrophysics, Academia Sinica, 10617 Taipei, Taiwan Received 18 February 2016 / Accepted 18 May 2016 ABSTRACT Aims. We study a sample of eight B[e] stars with uncertain evolutionary status to shed light on the origin of their circumstellar dust. Methods. We performed a diagnostic analysis on the spectral energy distribution beyond infrared wavelengths, and conducted a census of neighboring region of each target to ascertain its evolutionary status. Results. In comparison to pre-main sequence Herbig stars, these B[e] stars show equally substantial excess emission in the near- infrared, indicative of existence of warm dust, but much reduced excess at longer wavelengths, so the dusty envelopes should be compact in size. Isolation from star-forming regions excludes the possibility of their pre-main sequence status. Six of our targets, including HD 50138, HD 45677, CD−24 5721, CD−49 3441, MWC 623, and HD 85567, have been previously considered as FS CMa stars, whereas HD 181615/6 and HD 98922 are added to the sample by this work. We argue that the circumstellar grains of these isolated B[e] stars, already evolved beyond the pre-main sequence phase, should be formed in situ.
    [Show full text]
  • Classification of Planetary Nebulae Through Deep Transfer Learning
    galaxies Article Classification of Planetary Nebulae through Deep Transfer Learning Dayang N. F. Awang Iskandar 1,2,*,† , Albert A. Zijlstra 2,† , Iain McDonald 2,3 , Rosni Abdullah 4 , Gary A. Fuller 2, Ahmad H. Fauzi 1 and Johari Abdullah 1 1 Faculty of Computer Science and Information Technology, Universiti Malaysia Sarawak, Sarawak 94300, Malaysia; [email protected] (A.H.F.); [email protected] (J.A.) 2 Jodrell Bank Centre for Astrophysics, Department of Physics and Astronomy, School of Natural Sciences, University of Manchester, Oxford Road, Manchester M13 9PL, UK; [email protected] (A.A.Z.); [email protected] (I.M.); [email protected] (G.A.F.) 3 School of Physical Sciences, The Open University, Walton Hall, Kents Hill, Milton Keynes MK7 6AA, UK 4 School of Computer Sciences, Universiti Sains Malaysia, Pulau Pinang 11800, Malaysia; [email protected] * Correspondence: [email protected] † These authors contributed equally to this work. Received: 11 August 2020; Accepted: 7 December 2020; Published: 11 December 2020 Abstract: This study investigate the effectiveness of using Deep Learning (DL) for the classification of planetary nebulae (PNe). It focusses on distinguishing PNe from other types of objects, as well as their morphological classification. We adopted the deep transfer learning approach using three ImageNet pre-trained algorithms. This study was conducted using images from the Hong Kong/Australian Astronomical Observatory/Strasbourg Observatory H-alpha Planetary Nebula research platform database (HASH DB) and the Panoramic Survey Telescope and Rapid Response System (Pan-STARRS). We found that the algorithm has high success in distinguishing True PNe from other types of objects even without any parameter tuning.
    [Show full text]
  • Gas and Dust in the Magellanic Clouds
    Gas and dust in the Magellanic clouds A Thesis Submitted for the Award of the Degree of Doctor of Philosophy in Physics To Mangalore University by Ananta Charan Pradhan Under the Supervision of Prof. Jayant Murthy Indian Institute of Astrophysics Bangalore - 560 034 India April 2011 Declaration of Authorship I hereby declare that the matter contained in this thesis is the result of the inves- tigations carried out by me at Indian Institute of Astrophysics, Bangalore, under the supervision of Professor Jayant Murthy. This work has not been submitted for the award of any degree, diploma, associateship, fellowship, etc. of any university or institute. Signed: Date: ii Certificate This is to certify that the thesis entitled ‘Gas and Dust in the Magellanic clouds’ submitted to the Mangalore University by Mr. Ananta Charan Pradhan for the award of the degree of Doctor of Philosophy in the faculty of Science, is based on the results of the investigations carried out by him under my supervi- sion and guidance, at Indian Institute of Astrophysics. This thesis has not been submitted for the award of any degree, diploma, associateship, fellowship, etc. of any university or institute. Signed: Date: iii Dedicated to my parents ========================================= Sri. Pandab Pradhan and Smt. Kanak Pradhan ========================================= Acknowledgements It has been a pleasure to work under Prof. Jayant Murthy. I am grateful to him for giving me full freedom in research and for his guidance and attention throughout my doctoral work inspite of his hectic schedules. I am indebted to him for his patience in countless reviews and for his contribution of time and energy as my guide in this project.
    [Show full text]
  • Thesisthesis We Analyzed a Large Sample of Young Stars,, Coveringcovering Aa Massmass Rangerange of ~2 to ~20 Solar Masses
    UvA-DARE (Digital Academic Repository) Dusty disks around young stars Verhoeff, A. Publication date 2009 Document Version Final published version Link to publication Citation for published version (APA): Verhoeff, A. (2009). Dusty disks around young stars. General rights It is not permitted to download or to forward/distribute the text or part of it without the consent of the author(s) and/or copyright holder(s), other than for strictly personal, individual use, unless the work is under an open content license (like Creative Commons). Disclaimer/Complaints regulations If you believe that digital publication of certain material infringes any of your rights or (privacy) interests, please let the Library know, stating your reasons. In case of a legitimate complaint, the Library will make the material inaccessible and/or remove it from the website. Please Ask the Library: https://uba.uva.nl/en/contact, or a letter to: Library of the University of Amsterdam, Secretariat, Singel 425, 1012 WP Amsterdam, The Netherlands. You will be contacted as soon as possible. UvA-DARE is a service provided by the library of the University of Amsterdam (https://dare.uva.nl) Download date:06 Oct 2021 Dusty Disks around Dusty Disks around Stars are formed through the collapse of giant molecular clouds.. During this contraction the matter spins up and naturally forms a circumstellar disk.. OnceOnce accretionaccretion comescomes toto aa halt,halt, thesethese disksdisks arare relatively stable.. SomeSome disksdisks areare kknown to last up to 10 Myrs.. MostMost disks however,, dissipatedissipate onon shorshorter time scales under the inuence of photoevaporation and planet formation. These disks,, consistingconsisting of 99% gas and 1% dust, have revealed a high variety of dust composition and geometry.
    [Show full text]
  • Reflection Nebula Visualization
    Reflection Nebula Visualization Marcus A. Magnor∗ Kristian Hildebrand Andrei Lintu Andrew J. Hanson† MPI Informatik MPI Informatik MPI Informatik Indiana University ABSTRACT Stars form in dense clouds of interstellar gas and dust. The residual dust surrounding a young star scatters and diffuses its light, making the star's “cocoon” of dust observable from Earth. The resulting structures, called reflection nebulae, are commonly very colorful in appearance due to wavelength-dependent effects in the scatter- ing and extinction of light. The intricate interplay of scattering and extinction cause the color hues, brightness distributions, and the ap- parent shapes of such nebulae to vary greatly with viewpoint. We describe here an interactive visualization tool for realistically ren- dering the appearance of arbitrary 3D dust distributions surround- ing one or more illuminating stars. Our rendering algorithm is based on the physical models used in astrophysics research. The tool can be used to create virtual fly-throughs of reflection nebulae for interactive desktop visualizations, or to produce scientifically accurate animations for educational purposes, e.g., in planetarium shows. The algorithm is also applicable to investigate on-the-fly the visual effects of physical parameter variations, exploiting visualiza- tion technology to help gain a deeper and more intuitive understand- ing of the complex interaction of light and dust in real astrophysical settings. CR Categories: I.3.3 [Computer Graphics]: Picture/Image Figure 1: Reflection nebulae: Recently formed, hot stars illuminate Generation—Viewing algorithms; I.3.7 [Computer Graphics]: the surrounding interstellar dust that scatters and absorbs the star Three-Dimensional Graphics and Realism—Color, shading, shad- light to give rise to a large range of color hues and brightness varia- owing, and texture; J.2 [Computer Applications]: Physical Sciences tions.
    [Show full text]
  • Exótico Cielo Profundo 12
    12 Y el astrónomo armó su Árbol Celestial Monoceros (Mon) Monocerotis. El Unicornio. · Exótico Cielo Profundo 12 de Rodolfo Ferraiuolo y Enzo De Bernardini Constelación Monoceros (Mon) Época Verano Austral Alessi 14 LDN 1601 Cr 95 IC 447 IC 446 NGC 2245 B 37 B 38 Objetos IC 448 NGC 2247 Basel 8 NGC 2251 NGC 2254 LDN 1603 Basel 7 Tr 5 B 39 NGC 2259 NGC 2261 NGC 2264 Nuevamente, hacia el anticentro de la Vía Láctea, moviéndonos sobre la atrayente zona del ecuador galáctico que cruza al mítico Unicornio, nos abocaremos a la exploración de estos fascinantes campos donde predominan vastas zonas de hidrógeno y polvo interestelar, combinados con ricos campos estelares. Por el noroeste de Monoceros, limitando con las constelaciones de Gemini y Orion, esta área seleccionada abarca unos 9º cuadrados e, incluye varias nebulosidades brillantes y oscuras, y también cúmulos galácticos. En total, indagaremos veinte objetos de cielo profundo de variada dificultad que, como siempre, recomendamos observar desde lugares oscuros, fuera de las luminosas ciudades. Para situarnos en la zona, primero localizaremos la estrella amarilla de mag. 3,4, xi (ξ) Geminorum, Alzir y, desde allí nos moveremos unos 3º al sudsudoeste para hallar NGC 2264, nuestro primer objetivo de la noche, el cúmulo Árbol de Navidad. Con mag. 4,1 y un tamaño de 45'x30', este conocido cúmulo estelar con nebulosidad asociada, fue descubierto, el 18 de enero de 1784, por W. Herschel, quién casi dos años después detectó la fina nebulosidad. Está compuesto por más de 40 estrellas destacadas, entre más de 200, a una distancia de 2450 años luz, siendo su clasificación es III 3 r n.
    [Show full text]
  • University of Hawai'i, Institute for Astronomy Publications in Calendar
    University of Hawai‘i, Institute for Astronomy Publications in Calendar Year 2004 The names of authors listed as affiliated with IfA in each ar- &Wainscoat, R. J. Twenty-Three High-Redshift Super- ticle are in boldface. novae from the Institute for Astronomy Deep Survey: Doubling the Supernova Sample at z > 0.7. ApJ, 602, Abazajian, K., et al., including Siegmund, W. A., & Sza- 571–594 (2004) pudi, I. The Second Data Release of the Sloan Digital Sky Survey. AJ, 128, 502–512 (2004) Bendo, G. J., & Joseph, R. D. Nuclear Stellar Populations in the Infrared Space Observatory Atlas of Bright Spiral Abbas, M. M., LeClair, A., Owen, T., et al. The Nitrogen Galaxies. AJ, 127, 3338–3360 (2004) Isotopic Ratio in Jupiter’s Atmosphere from Observations by the Composite Infrared Spectrometer on the Cassini Bettoni, D., Mazzei, P., Della Valle, A., Franceschini, G. D. Spacecraft. ApJ, 602, 1063–1074 (2004) A., & Aussel, H. Optical and Spectroscopic Follow-Up of the Deeper FIR Selected Sample. Mem. Soc. Astron. Abel, N. P., Brogan, C. L., Ferland, G. J., O’Dell, C. R., Italiana Suppl., 5, 267–271 (2004) Shaw, G., & Troland, T. H. Physical Conditions in Orion’s Veil. ApJ, 609, 247–260 (2004) Beuzit, J.-L., et al., including Roddier, C., Roddier, F., & Mart´ın, E. L. New Neighbours. III. 21 New Compan- Allen, S. W., Schmidt, R. W., Ebeling, H., Fabian, A. C., ions to Nearby Dwarfs, Discovered with Adaptive Optics. &van Speybroeck, L. Constraints on Dark Energy from A&A, 425, 997–1008 (2004) Chandra Observations of the Largest Relaxed Galaxy Clusters.
    [Show full text]
  • Astronomy Magazine 2011 Index Subject Index
    Astronomy Magazine 2011 Index Subject Index A AAVSO (American Association of Variable Star Observers), 6:18, 44–47, 7:58, 10:11 Abell 35 (Sharpless 2-313) (planetary nebula), 10:70 Abell 85 (supernova remnant), 8:70 Abell 1656 (Coma galaxy cluster), 11:56 Abell 1689 (galaxy cluster), 3:23 Abell 2218 (galaxy cluster), 11:68 Abell 2744 (Pandora's Cluster) (galaxy cluster), 10:20 Abell catalog planetary nebulae, 6:50–53 Acheron Fossae (feature on Mars), 11:36 Adirondack Astronomy Retreat, 5:16 Adobe Photoshop software, 6:64 AKATSUKI orbiter, 4:19 AL (Astronomical League), 7:17, 8:50–51 albedo, 8:12 Alexhelios (moon of 216 Kleopatra), 6:18 Altair (star), 9:15 amateur astronomy change in construction of portable telescopes, 1:70–73 discovery of asteroids, 12:56–60 ten tips for, 1:68–69 American Association of Variable Star Observers (AAVSO), 6:18, 44–47, 7:58, 10:11 American Astronomical Society decadal survey recommendations, 7:16 Lancelot M. Berkeley-New York Community Trust Prize for Meritorious Work in Astronomy, 3:19 Andromeda Galaxy (M31) image of, 11:26 stellar disks, 6:19 Antarctica, astronomical research in, 10:44–48 Antennae galaxies (NGC 4038 and NGC 4039), 11:32, 56 antimatter, 8:24–29 Antu Telescope, 11:37 APM 08279+5255 (quasar), 11:18 arcminutes, 10:51 arcseconds, 10:51 Arp 147 (galaxy pair), 6:19 Arp 188 (Tadpole Galaxy), 11:30 Arp 273 (galaxy pair), 11:65 Arp 299 (NGC 3690) (galaxy pair), 10:55–57 ARTEMIS spacecraft, 11:17 asteroid belt, origin of, 8:55 asteroids See also names of specific asteroids amateur discovery of, 12:62–63
    [Show full text]
  • THE STAR FORMATION NEWSLETTER an Electronic Publication Dedicated to Early Stellar Evolution and Molecular Clouds
    THE STAR FORMATION NEWSLETTER An electronic publication dedicated to early stellar evolution and molecular clouds No. 131 — 8 September 2003 Editor: Bo Reipurth ([email protected]) Abstracts of recently accepted papers The pre-main sequence spectroscopic binary AK Sco revisited S.H.P. Alencar1,2, C.H.F. Melo3, C.P. Dullemond4, J. Andersen5, C. Batalha6, L.P.R. Vaz1, and R.D. Mathieu7 1 Departamento de Fsica, ICEx-UFMG, CP. 702, Belo Horizonte - MG, 30123-970, Brazil 2 Departamento de Astronomia, IAG, USP, Rua do Mat˜ao,1226, S˜aoPaulo, 05508-900, Brazil 3 European Southern Observatory, Casilla 19001, Santiago 19, Chile 4 Max Planck Institut f¨urAstrophysik, Postfach 1317, D-85741 Garching, Germany 5 Niels Bohr Institute for Astronomy, Physics, and Geophysics, Astronomical Observatory, Juliane Maries Vej 30, 2100 Copenhagen, Denmark 6 Observat´orio Nacional, Departamento de Astrof´ısica, Rua General Jos´eCristino 77, S˜aoCrist´ov˜ao, Rio de Janeiro, 20921-400, Brazil 7 Department of Astronomy, University of Wisconsin-Madison, 475 North Charter Street, Madison, WI, 53706, USA E-mail contact: silvia@fisica.ufmg.br We present an analysis of 32 high-resolution echelle spectra of the pre-main sequence spectroscopic binary AK Sco obtained during 1998 and 2000, as well as a total of 72 photoelectric radial-velocity observations from the period 1986- 1994. These data allow considerable improvement of the period and other orbital parameters of AK Sco. Our analysis also includes eight series of photometric observations in the uvby and Geneva seven-color systems from 1987, 1989, 1990, 1992, 1994 and 1997.
    [Show full text]
  • Young Stars and Reflection Nebulae Near the Lower" Edge" of the Galactic Molecular Disc
    Astronomy & Astrophysics manuscript no. text c ESO 2018 October 30, 2018 Young stars and reflection nebulae near the lower “edge” of the Galactic molecular disc? Pedro M. Palmeirim and Joao˜ L. Yun Universidade de Lisboa - Faculdade de Cienciasˆ Centro de Astronomia e Astrof´ısica da Universidade de Lisboa, Observatorio´ Astronomico´ de Lisboa, Tapada da Ajuda, 1349-018 Lisboa, Portugal e-mail: [email protected], [email protected] Received September 1, 2009; accepted November 16, 2009 ABSTRACT Aims. We investigate the star formation occurring in a region well below the Galactic plane towards the optical reflection nebula ESO 368-8 (IRAS 07383−3325). We confirm the presence of a small young stellar cluster (or aggregate of tens of YSOs) identified earlier, embedded in a molecular cloud located near the lower “edge” of the Galactic disc, and characterise the young stellar popula- tion. We report the discovery of a near-infrared nebula, and present a CO map revealing a new dense, dynamic cloud core. Methods. We used near-infrared JHKS images obtained with VLT/ISAAC, millimetre CO spectra obtained with the SEST telescope, and optical V-band images from the YALO telescope. Results. This star formation region displays an optical reflection nebula (ESO 368-8) and a near-infrared nebula located about 4600 (1.1 pc) from each other. The two nebulae are likely to be coeval and to represent two manifestations of the same single star formation episode with about 1 Myr age. The near-IR nebula reveals an embedded, optically and near-IR invisible source whose light scatters off a cavity carved by previous stellar jets or molecular outflows and into our line-of-sight.
    [Show full text]