Research in planetary Astronomy

The focus was on the study, via near infrared observations, of the outer planets and their satellites. In the last year, these observations have emphasized imaging observations using the Cassegrain infrared camera at the f/70 focus of the 200 inch Hale telescope

Infrared Astronomical Satellite (IRAS) Scientific Data Analysis System

The Jet Propulsion Laboratory's Scientific Data Analysis System will process Infrared Astronomical Satellite data and produce a catalog of perhaps a million infrared sources in the sky, as well as other vital information for astronomical research

Research at Palomar Observatory in planetary astronomy

A wide range of observational studies are carried out to improve our understanding of the bodies of the outer solar system. Using the 200-inch Hale telescope, near-infrared observations are made of Uranus, Neptune, and the Pluto-Charon system. High time resolution occultation observations of the Uranus Ring system are used to study in detail the dynamics of this system. Occultation studies of Neptune are probing this intriguing ring-arc system. Occulation observations of the Pluto-Charon system probe the surface properties of these distant bodies. In addition, the plate material of the PSSII servey is being used to search for new comets and asteroids. Researchers observed one Neptune stellar occultation in July 1987 and completed the analysis of a series of seven separate Neptune occultation observations in conjunction with Nicholson et al., of Cornell. The analysis has shown that minimum of three ring arcs, at radii ranging from 54,000 km - 67,000 km are required to account for the high quality ring events. Current theoretical models can account for these data. Of two observations scheduled of Pluto-Charon mutual occulations scheduled for the 200-inch, the Charon eclipse event was successfully observed (the other was clouded out)

High Resolution WFPC2 Imaging of IRAS 09104+4109

With a infrared luminosity of nearly 10^13 Lsuns, IRAS 09104+4109 is the most luminous galaxy with z<0.5 in the IRAS All Sky Survey. A radio-loud Seyfert 2 type optical spectrum, a cD host galaxy in a rich cluster, and a massive cooling flow make IRAS 09104+4109 unique among ultraluminous infrared galaxies. Cannibalized cluster members and the cooling intercluster medium may contribute both the fuel and the dust needed to re-radiate the power of IRAS 09104+4109 into the far-infrared. We have imaged IRAS 09104+4109 in the WFPC2 F622W, F814W, and FR680N filters on the HST to obtain rest frame 4300A, 5700A, and [OIII] emission line images on sub-kpc scales. IRAS 09104+4109 displays a complex morphology on the smallest scales, with radiating filaments, an asymmetric [OIII] nebula, and a number of very faint, irregular blue objects surrounding the cD galaxy. We discuss the nature and possible interplay between the enshrouded QSO nucleus, the cD host galaxy and the irregular cluster.Comment: LaTex, 6 pages with 2 postscript and 1 jpg figure. To appear in the proc. of the Ringberg workshop "Ultraluminous Galaxies: Monsters or Babies" (Ringberg castle, Sept. 1998), Ap&SS, in pres

Infrared Astronomy

Several observational programs in infrared astronomy are described and significant findings are briefly discussed. The near infrared work concentrates largely on the use of the 5 m Hale telescope in spectroscopic and photometric studies of extragalactic sources. Observations of the P alpha line profile in a low redshift quasar, X-ray bursters, reflection nebula, and cataclysmic variables are included. Millimeter continuum observations of dust emission from quasars and galactic molecular clouds are also discussed. Finally, improvements to instrumentation are reported

Near Infrared Observations of a Redshift 5.34 Galaxy: Further Evidence for Dust Absorption in the Early Universe

Imaging at 1.25 and 2.20 microns has been obtained of the field containing the galaxy (RD1) found at redshift 5.34 by Dey et al.(1998). This galaxy has been detected at 1.25 microns, while the lower redshift (z=4.02) galaxy also found in the same field by Dey et al. was detected at both 1.25 and 2.20 microns. Comparison to stellar population synthesis models indicates that if RD1 is a young ( 0.5 mag) is indicated. Combined with observations of other high redshift systems, these data show that dust is likely to be an important component of young galaxies even at redshifts of z > 5. The extinction-corrected monochromatic luminosity of RD1 at 1500 angstroms is then a factor of about three larger than L(1500)* as determined by Dickinson (1998) for z ~ 3 starburst galaxies. The implied star formation rate in RD1, corrected for extinction, is ~ 50-100 solar masses per year.Comment: plain LaTex with 1 postscript figure. ApJ Letters, accepte

Infrared properties of serendipitous X-ray quasars

Near infrared measurements were obtained of 30 quasars originally found serendipitously as X-ray sources in fields of other objects. The observations show that the infrared characteristics of these quasars do not differ significantly from those of quasars selected by other criteria. Because this X-ray selected sample is subject to different selection biases than previous radio and optical surveys, this conclusion is useful in validating previous inferences regarding the infrared colors of 'typical' quasars

Infrared astronomy research and high altitude observations

Highlights are presented of studies of the emission mechanisms in the 4 to 8 micron region of the spectrum using a circular variable filter wheel spectrometer with a PbSnTe photovoltaic detector. Investigations covered include the spectroscopy of planets, stellar atmospheres, highly obscured objects in molecular clouds, planetary nebulae, H2 regions, and extragalactic objects

H₂ and Infrared in Global Starburst Galaxies

Far infrared measurements from the IRAS survey combined with estimates of the molecular gas content provide a fundamental basis for the analysis of the starburst phenomena in galaxies. When the ratio of far infrared luminosity to molecular gas mass significantly exceeds that in normal galaxies like the Milky Way (4 L_⊙ M_⊙⁻¹), star formation is occurring on a shorter timescale, possibly with an initial mass function-biased towards high mass stars. In the highest luminosity IRAS galaxies (L_(IR) ≥ 10¹¹ L_⊙), the luminosity to H₂ mass ratio is typically 40 L_⊙ M_⊙⁻¹, indicating star formation rates of 10- 100 M_⊙ yr⁻¹ and cycling times for the ISM much less than 10⁹ yr. In the very luminous infrared galaxies, the optical morphology almost invariably shows evidence of a strong galactic interaction and a substantial fraction of the total molecular gas content is seen at radii ~ 1 kpc. Dense molecular gas probably plays a pivotal role in the evolution of such dynamically disturbed systems: being dissipative, the gas can readily sink to the center of the interacting system where it may fuel a nuclear starburst and/or build up and fuel a central active nucleus. We show that the shape of the high luminosity end of the infrared galaxy luminosity function can be reproduced by a model in which normal spiral galaxies, represented in the Schecter function, undergo collision-induced starbursts. Statistics from the IRAS survey are consistent with the percentage of all spiral galaxies currently undergoing a global starburst being approximately 0.2% and the lifetime of the starburst being a dynamical time, approximately 2 x 10⁸ years. The present epoch rate is therefore such that 2% of all galaxies participate in a merger every 109 years and with standard cosmological evolution, nearly all galaxies would be undergoing such merger-induced starbursts at z= 1. Galactic merging and starburst activity must therefore play a central role in galactic evolution

The properties of infrared galaxies in the local universe

The 60 µm selected IRAS Bright Galaxy Sample is used as a starting point to derive additional complete flux-limited samples of extragalactic objects at 12, 25, and 100 µm. With these complete samples the luminosity functions at all IRAS wavelengths are derived for the local Universe. These luminosity functions are used to determine the infrared emission of the local Universe. The maximum in the energy output of galaxies occurs at 100 µm. The infrared emission of galaxies at 12 and 25 µm represents ~30% of the total infrared luminosity in the local Universe. The mean infrared colors of infrared selected galaxies vary systematically with infrared luminosity; the ratio S^v(60 µm)/S_v( 100 µm) increases and S_v(12 µm)/Sv(25 µm) decreases with increasing infrared luminosity