National Optical Astronomy Observatories National Optical Astronomy Observatories Quarterly Report April - June 1990 TABLE OF CONTENTS I. INTRODUCTION 1 II. SCIENTIFIC HIGHLIGHTS 2 A. The Latter-day Brightness Variation of the LMC Supernova 1987A 2 B. The Distance to Virgo and the Age of the Universe: New Data from Planetary Nebulae 2 C. Color Gradients in E Galaxies: Measuring the Galaxy Mass? 3 D. High Frequency Solar Oscillations 3 E. Solar-Stellar Observations 4 F. Solar Atmospheric Motions and Structure 6 G. Spectral and High-Resolution Imaging 7 III. PERSONNEL 8 A. Visiting Scientists 8 B. New Hires 8 C. Terminations 8 D. Change of Status 8 E. Summer Research Assistants 9 IV. INSTRUMENTATION, NEW PROJECTS AND OBSERVATORY ACTIVITIES 10 A. Future Telescope Technology Program (FTT) 10 B. Global Oscillation Network Group (GONG) 11 C. WIYN Project 12 D. Instrumentation Projects 12 E. Observatory Activities 15 V. PROGRAM SUPPORT 17 A. Director's Office 17 B. 8-M Office 18 C. Central Administrative Services 18 D. Central Computer Services 19 E. Central Facilities Operations 19 F. Engineering and Technical Services 19 G. Publications and Information Resources 20 Appendices Appendix A: Telescope Usage Statistics Appendix B: Observational Programs I. INTRODUCTION This quarterly report covers scientific highlights for the period of April - June 1990, as well as personnel changes for the period. Highlights emphasize concluded projects rather than work in progress. The report also discusses new technology for telescopes and instrumentation, GONG, WIYN, instrumentation projects, and observatory activities. The Engineering and Technical Services division now submits reports for the instrumentation projects, with contributions from program scientists, if necessary. The Associate Directors for CTIO and NSO continue to provide the information of efforts at La Serena/Cerro Tololo and Sacramento Peak. Activities of the NOAO units are included, and the appendices list telescope usage statistics and observational programs. H. SCIENTIFIC HIGHLIGHTS A. The Latter-day Brightness Variation of the LMC Supernova 1987A. CTIO staff members M. Hamuy and N.B. Suntzeff have analyzed photometric observations covering a 813-day period since the outburst of SN 1987A in the Large Magellanic Cloud (LMC). Because this is the only supernova observed from a reliably known distance, the study of this object is critical in the interpretation of the outbursts of more distant supernovae. The CTIO observations were made in several band-passes ranging from the observable ultraviolet to the near-infrared spectral region. The derived data make possible comparisons of the variations in brightness and color of SN 1987A with those shown by other supemovae of similar type; namely type II-determined by the presence of neutral hydrogen lines in spectra taken soon after outburst. It is now known that while type II supernovae show marked differences in brightness variations in the initial 150 day period after outburst, thereafter all appear to show the same exponential rate of brightness decline up to about 400 days past outburst. This is the period for which reliable apparent brightness information is available for other type II supemovae. While in theory the initial heterogeneity in brightness evolution is caused by differences in the physical nature of the supemovae progenitors, the similar brightness variations between days 150 and 400 after outburst are believed to be controlled by the radioactive decay of 56Co. Of special interest in the Hamuy-Suntzeff study is that when SN 1987A is compared to other more distant type II supemovae, the estimated absolute brightness differences at a given epoch past day 150, and at least up to day 400, are consistent with the uncertainties in the distances of the distant supemovae. Thus the apparent brightness of a given type II supernova after day 150 may be a reliable indicator of its distance. Past day 400 after the outburst, the decline in the optical brightness of SN 1987A was observed to fall off more rapidly. Soon thereafter, observers at the European Southern Observatory (ESO) found that at far infrared wavelengths the supernova had brightened. About the same time, a sudden shift towards the blue was noticed in the supernova's emission spectral lines. In collaboration, N. Suntzeff and ESO astronomer P. Bouchet combined the CTIO and ESO photometric data and noticed that while these changes were occurring, the integrated all-wavelengths radiation from the supernova did not change its decline rate. These various late observations can be interpreted as caused, very likely, by the condensation into dust particles of part of the material ejected by the supernova. B. The Distance to Virgo and the Age of the Universe: New Data from Planetary Nebulae. The most ancient problem in astronomy, that of measuring distances, is still fraught with uncertainty and controversy. Methods used to measure intermediate distances to nearby galaxies are particularly uncertain, since the reliable periodic stars are often too faint, and the redshifts are contaminated by motions induced by local groups and clusters of galaxies. Two years ago an item featured in these scientific highlights described a potentially new and valuable technique for measuring these distances. Developed by J. Jacoby (KPNO), R. Ciardullo (KPNO), H. Ford and J. Neill (ST Scl), the method uses observations of planetary nebulae (PN) in other galaxies. These observers have found that the PN luminosity function has a nearly invariant shape, with a sharp cutoff at a V magnitude of about -4. This upper cutoff allows these objects to be used as standard candles when a large number of them are observed in other galaxies. Jacoby and his collaborators have verified this technique by observations of, and distance determinations to, M31 and the other galaxies in the Local Group. They have now applied this technique to galaxies in the Virgo Cluster, which has one of the most controversial of distance determinations. Past work on this cluster has provided distances which tend to cluster into a "near" value (12 - 16 Mpc) and a "far" value of 20 to 24 Mpc. From a series of observations made at KPNO and at Canada-France-Hawaii Telescope (CFHT), Jacoby et al. have obtained data on the brightness of planetary nebulae in galaxies in the Virgo cluster. These remarkable observations have then allowed an independent determination of the distance to Virgo. The value obtained is 14.7 megaparsecs, which supports the "near" value. One immediate consequence of this is a determination of the age of the Universe. Assuming the motion of the Virgo cluster is pure expansion from the Hubble flow, this measurement gives an age of about 12 billion years, which is very young-younger, in fact, than the age estimates of the oldest stars which lie in the range of 14 to 16 billion years. Resolution of this dilemma may lie in the "Great Attractor." If this giant mass concentration exists, and evidence is growing that it does, then part of the recession velocity of Virgo may be due to the gravitational pull of this object. This effect will reduce the derived value of the Hubble constant and increase the age of the Universe, but the magnitude of this effect is still unclear. In any event, the value of this new method now seems proven, and the distance to the Virgo cluster seems more firmly established at the lower value. C. Color Gradients in E Galaxies: Measuring the Galaxy Mass? The variation of colors within and between elliptical galaxies is a well known phenomenon. These variations are usually interpreted as resulting from changes in the metallicity of the stellar populations in these galaxies. However, the unresolved astrophysical problem is how these metallicity variations come to be. Are they the result of the initial conditions present when the protogalactic gas cloud first condensed? Are they the result of the evolutionary history of the stellar population within the galaxy? What are the effects of the immediate environment of the galaxy now and in the past? Are the observations a result of all of these factors in some combination? Many parameters enter into determining metallicity variations, such as the initial mass function, star-formation efficiency, metal yield from high mass stars, stellar winds, recycling versus galactic winds, and the infall of primordial gas. A new and surprising insight into this phenomenon has come from recent observations made by M. Franx (Ctr. for Astrophys.), G. Ulingworth (Lick Obs.), and T. Heckman (U. of Maryland). Using the KPNO and CTIO 0.9-m telescopes and the ESO 2.2-m telescope, these observers obtained U-R and B-R color profiles in 17 elliptical galaxies. These data were then compared to other properties of the galaxies to search for any correlations that may arise. In general, the colors are more red in higher mass galaxies and change from red to blue with increasing distance from the center of the galaxy. This trend is consistent with metal absorption line strength data in other galaxies and confirms the use of colors as metallicity indicators. The surprising result is that there is a strong correlation between the local color and the local escape velocity in all the galaxies studied, in that the colors become more blue as the escape velocity rises. This strongly suggests that the local escape velocity is the primary factor that determines the metallicity of the stellar population. That such a correlation exists at all is unusual, for many factors could cause a large scatter in such a relation; e.g., mergers, stripping, late gas inflow, velocity anisotropics, etc. The physical mechanism that causes this relation is unclear. It could arise because the star-formation rate is proportional to the energy released in cloud-cloud collisions, or it could be that star-formation proceeds until the energy from supemovae becomes great enough to expel gas locally from the galaxy.