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NATIONAL OPTICAL ASTRONOMY OBSERVATORIES NATIONAL OPTICAL ASTRONOMY OBSERVATORIES Cerro Tololo Inter-American Observatory Kitt Peak National Observatory National Solar Observatory La Serena, Chile Tucson, Arizona 85726 Sunspot, New Mexico 88349 ANNUAL REPORT October 1993 - September 1994 November 10, 1994 TABLE OF CONTENTS I. INTRODUCTION n. AURA BOARD m. SCIENTIFIC PROGRAM Cerro Tololo Inter-American Observatory (CTIO) 1. A Hubble Diagram of Distant Type la Supernovae 2. The Stellar Populations of the Carina Dwarf Galaxy 3 3. Observations of the Collision ofComet Shoemaker-Levy 9 and Jupiter 4 B. Kitt Peak National Observatory (KPNO) 5 1. Faint Galaxy Halo Could Trace Dark Matter 5 2. Young Stellar Objects in Bok Globules 5 3. A New Tool for Stellar Population Studies 6 C. National Solar Observatory (NSO) 7 1. New Observations of IR Coronal Emission Lines 7 2. High Resolution Infrared Spectroscopy of the Carbon Monoxide Molecule 7 3. Subsurface Magnetic Flux Tubes 8 IV. DIVISION OPERATIONS 9 A. Cerro Tololo Inter-American Observatory 9 1. 4-m Telescope Image Quality Improvements 9 2. Infrared Instrumentation 10 3. Arcon CCD Controllers 10 4. Other Projects 11 B. Kitt Peak National Observatory 11 1. New KPNO Programs in FY 1994 11 2. KPNO Facilities Improvements in FY 1994 13 3. KPNO Instrumentation 14 C. National Solar Observatory 17 1. Image Quality Improvement Program for NSO Telescopes 17 2. Sac Peak Instrumentation 18 3. Tucson Instrumentation 20 D. US Gemini Program 21 E. NOAO Instrumentation Program 22 V. MAJOR PROJECTS 23 A. Global Oscillation Network Group Project 23 B. The Precision Solar Photometric Telescope Project (PSPT) 25 C. SWATH Mission 26 D. WIYN 26 E. Partnerships in Progress at CTIO 28 1. 2MASS Survey 28 2. Sao Paulo Telescope 29 3. Southern Spectroscopic Survey Telescope 29 4. SOAR 29 VI. CENTRAL COMPUTER SERVICES 29 VII. SCIENTIFIC STAFF 30 A. CTIO Scientific Staff Changes 30 B. KPNO Scientific Staff Changes 31 C. NSO Scientific Staff Changes 31 Vm. DIRECTOR'S OFFICE 32 IX. NOAO STATISTICS 33 A. CTIO Statistics 33 B. KPNO Statistics 33 C. NSO Statistics 34 D. NOAO Central Computer Services Statistics 34 E. NOAO Tucson Headquarters Building Statistics 34 APPENDICES Appendix A: NOAO Technical Reports List Appendix B: CTIO Publications List Appendix C: KPNO Publications List Appendix D: NSO Publications List n I. INTRODUCTION This report covers the period 1 July 1993 - 30 June 1994. The National Optical Astronomy Observatories (NOAO) are operated for the National Science Foundation by the Association of Universities for Research in Astronomy. The four divisions of the NOAO are: the Cerro Tololo Inter-American Observatory (CTIO), in northern Chile; the Kitt Peak National Observatory (KPNO), near Tucson; the National Solar Observatory (NSO), with facilities on Kitt Peak and at Sacramento Peak, New Mexico; and the US Gemini Program (USGP), based in Tucson. NOAO observing and data reduction facilities are available to the entire astronomical community. The NOAO Home Page contains on-line information about NOAO services, including telescope schedules and instrument availability, and information about how to apply for telescope time. The NOAO Home Page can be accessed through the World Wide Web at http://www.noao.edu/. II. AURA BOARD NOAO is managed by the Association of Universities for Research in Astronomy, Inc. (AURA). There are twenty-six AURA member universities, including three international institutions. Each member university appoints one individual to serve on the AURA Board, which also includes the President of the Corporation and twelve Directors-at-Large. AURA also operates the Space Telescope Science Institute under contract with the National Aeronautics and Space Administration, and the Gemini 8-m Telescopes Project for the NSF. III. SCIENTIFIC PROGRAM A. Cerro TololoInter-American Observatory (CTIO) 1. A Hubble Diagram ofDistant Type la Supernovae Since the discovery by Edwin Hubble in 1929 that the Universe is expanding, one of the outstanding problems in observational cosmology has been the determination of the Hubble constant, Ho, which measures the rate of expansion in the neighborhood of the Milky Way. Knowledge of Ho is of special importance since it provides a limit to the age of the Universe. In the 65 years since Hubble's discovery, debate has raged over the precise value of Ho, with astronomers currently dividing into two main camps: those who argue for a "short" distance scale with Ho -70-90 km s' Mpc"1, and those who favor a "long" distance scale with Ho -50 km s1 Mpc'1. The short distance scale is supported by several different techniques for measuring distances to galaxies, but a persistent thorn in the side has been the results based on Type la Supernovae (SNe la) which have consistently favored the long distance scale. Indeed, recent distance measurements to the host galaxies of two SNe la using Cepheid variable stars discovered with the Hubble Space Telescope have yielded values of Ho between 50-55 km s'1 Mpc"1. Since several of the distance indicators which support the short distance scale are also based on Cepheid distances for calibration, this disagreement is particularly perplexing. Recent work by a team of investigators at CTIO and the University of Chile at Cerro Calan led by Mario Hamuy (CTIO) and Jose Maza (U. of Chile) provides a possible resolution to this conflict. From 1990-1993, Hamuy and Maza carried out a supernova search using the Michigan Curtis Schmidt telescope at CTIO with the goal of discovering and observing a sample of distant SNe la which could then be used to study the Hubble diagram of these objects. The first Hubble diagram for SNe la, which was published by Charles Kowal in 1968, yielded a relatively small dispersion (0.6 mag) in the peak brightnesses of SNe la, revealing the potential utility of these objects as extragalactic distance indicators. More modern studies have found a scatter of 0.3-0.5 mag, but two major observational complications have hampered the determination of the intrinsic spread in the peak luminositiesof these objects: 1) These Hubble diagrams are based nearly entirely on nearby objects (z < 0.02). At such low redshifts, the peculiar motions of individual galaxies introduce significant scatter in the velocity field associated with the general expansion of the Universe. 2) Most historical SNe la light curves consist of fragmentary observations, more often than not obtained from photographic plates. With photographic plates, it is difficult to subtract accurately the bright galaxy background light on which the supernovae are often projected. The lack of a precise definition of the photographic band introduces an additional problem when comparing observations obtained from different observers and emulsions. Not surprisingly, even for bright supernovae with frequent observations, large discrepancies (-1 mag) often appear among photometry from different sources. Since supernovae aretransitory objects, visible typically foronly a few months, they cannot simply be re- observed to improve the data quality. Hence, Hamuy and Maza organized the Calan/Tololo search which led to the discovery of 50 new SNe during the three-year period that it was carried out. Follow-up spectroscopic observations obtained mostly with the CTIO 1.5-m and 4.0-m telescopes revealed that a significant fraction (-60%) of these objects were members of the Type la class, and thatnearly all were at redshifts between 0.02 and 0.1. Thanks to the generous collaboration of many visiting astronomers and CTIO staffmembers, BVRI photometry was secured with CCD detectors for most of these supernovae. So far, light curves have been completely reduced for 13 SNe la (i.e., roughly halfthe complete sample), and the analysis of these data forms the subject of a paper to be published by Hamuy et al. in the January 1995 issue of the Astronomical Journal. The Hubble diagrams in B and V for these 13 SNe la show clear evidence for a distance-dependent dispersion. Although some of the scatter could be due to the peculiar velocities of the host galaxies or to uncorrected dust absorption in the host galaxies,Hamuy and collaborators argue that the dominant source is an intrinsic dispersion in the peak absolute magnitudes of SNe la amounting to -0.8 mag in MB and -0.5 mag in Mv. The data also confirm, in general terms, the recent finding by Phillips from an independent sample of well-observed nearby SNela that the absolute B and V magnitudes are correlated with the initial decline rate of the B light curve. The sense of this correlation is that the most slowly declining events tend to be intrinsically the most luminous. In addition, Hamuy et al. find rather unexpectedly that galaxieshaving a youngerstellar populationappear to host the most luminous SNe la. It is these two effects-the dependence of the absolute luminosity on decline rate and host galaxy morphology-that provide the clues to understanding the small value of the Hubble constant derived by Sandage and collaborators from Cepheid distances to the host galaxies of SN 1937C and SN 1972E. As shown by Hamuy et al. from the published photometry of SN 1972E, this supernova was a slow- declining event and, therefore, probably more luminous than average. Using the peak luminosity-decline rate relations derived from either the Phillips or Calan/Tololo samples of SNe la, Hamuy et al. derive a Hubble constant in the range Ho = 62-67 km s' Mpc"1, which is -15% larger than the value that would be obtained if the peak luminosity-decline rate relation were to be ignored. Recent remeasurements by Pierce and Jacoby (KPNO) of the photographic plates obtained by Zwicky and Baade of SN 1937C indicate that this supernova was also an unusually slow-declining event, and so this supernova was probably also more luminous than average.
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  • Resolving the Dusty Circumstellar Environment of the a [E] Supergiant HD 62623 with the VLTI/MIDI

    Resolving the Dusty Circumstellar Environment of the a [E] Supergiant HD 62623 with the VLTI/MIDI

    Astronomy & Astrophysics manuscript no. HD62623˙v17 c ESO 2018 November 4, 2018 Resolving the dusty circumstellar environment of the A[e] supergiant HD 62623 with the VLTI/MIDI⋆ A. Meilland1, S. Kanaan2, M. Borges Fernandes2, O. Chesneau2, F. Millour1, Ph. Stee2, and B. Lopez2 1 Max Planck Intitut f¨ur Radioastronomie, Auf dem Hugel 69, 53121 Bonn, Germany 2 UMR 6525 CNRS H. FIZEAU UNS, OCA, Campus Valrose, F-06108 Nice cedex 2, France, CNRS - Avenue Copernic, Grasse, France. Received; accepted ABSTRACT Context. B[e] stars are hot stars surrounded by circumstellar gas and dust responsible for the presence of emission lines and IR-excess in their spectra. How dust can be formed in this highly illuminated and diluted environment remains an open issue. Aims. HD 62623 is one of the very few A-type supergiants showing the B[e] phenomenon. We studied the geometry of its circum- stellar envelope in the mid-infrared using long-baseline interferometry, which is the only observing technique able to spatially resolve objects smaller than a few tens of milliarcseconds. Methods. We obtained nine calibrated visibility measurements between October 2006 and January 2008 using the VLTI/MIDI instru- ment in SCI-PHOT mode and PRISM spectral dispersion mode with projected baselines ranging from 13 to 71 m and with various position angles (PA). We used geometrical models and physical modeling with a radiative transfer code to analyze these data. Results. The dusty circumstellar environment of HD 62623 is partially resolved by the VLTI/MIDI even with the shortest baselines. The environment is flattened (a/b 1.3 0.1) and can be separated into two components: a compact one whose extension grows from 17 mas at 8µm to 30 mas at 9.6µm∼ and± stays almost constant up to 13µm, and a more extended one that is over-resolved even with the shortest baselines.