Robert Benjamin Leighton

Robert Benjamin Leighton, a longtime physicist and astronomer at Caltech, died in Pasadena on 9 March 1997 of a neurological disease. Bob was born in Detroit on 10 September 1919 and received his physics undergraduate (BS, 1941) and graduate (MS, 1944; PhD, 1947) degrees from Caltech. He stayed at Caltech his entire professional career, serving as division chair of physics, mathematics and astronomy from 1970 to 1975 and retiring as the Valentine Professor of Physics in 1985

Interview with Gerry Neugebauer

An interview in two sessions, July 1991, with Gerry Neugebauer, Robert Andrews Millikan Professor of Physics in the Division of Physics, Mathematics, and Astronomy (PMA). Received his PhD in physics from Caltech (1960) and joined the faculty in 1962 as assistant professor. Lead scientist on IRAS (Infrared Astronomical Satellite), launched in 1983; director of Palomar Observatory 1980-1984; PMA division chair 1988-1993. Discusses his role in construction of Keck I, the first of W. M. Keck Observatory’s two 10-meter telescopes on Mauna Kea. Recalls his early interest in astronomy; switch to physics at Cornell; Army career working on Mariner program at Jet Propulsion Laboratory. Discusses his stint as Palomar director and its light problems; involvement, beginning in 1983, in planning for a 10-meter telescope with his former student Jerry Nelson and PMA division chair Edward C. Stone. Competing designs. Caltech’s decision to go with University of California, then expecting $36 million from Hoffman Foundation, as “junior partner.” Involvement of Keck Foundation; early notions of building a Keck telescope and a Hoffman telescope. Caltech becomes equal partner. Establishment of CARA (California Association for Research in Astronomy) to run the observatory. Comments on Mauna Kea site, conflict with UC over siting the headquarters: Waimea or Hilo. Selection of Waimea; Smart Trust. Discusses design and manufacture of the 36 mirror segments. Comments on difficulty working at telescope’s altitude; on partnership between UC, Caltech, and University of Hawaii. Continual drive in astronomy community for larger telescopes; adaptive optics. Itek’s problems with polishing the mirrors. Status of work on Keck II

Photoproduction of negative and positive pions from deuterium for photon energies 500 to 1000 Mev

The ratio of the yields of negative and positive pions photoproduced in deuterium has been measured at six photon energies between 500 and 1000 Mev and at seven angles between 20° and 160° in the center-of-momentum system of the photon and target nucleon. Pions were selected with a magnetic spectrometer and identified using momentum and specific ionization in a scintillation counter telescope. The spectator model of the deuteron was used to identify the photon energy. Statistical errors assigned to the π- / π+ ratio range between five and fifteen percent. The results of the present experiment join smoothly with the low-energy π- / π+ ratios obtained by Sands et al. At high energies the π- / π+ ratio varies from 0.5 at forward angles and energies near 900 Mev to 2.5 at 160° c.m. and energies 600 to 800 Mev. The cross sections for π- photo-production from neutrons have been derived from the π- / π+ ratio and the CalTech π+ photoproduction data. The angular distributions for π- production are considerably different from those for π+; there is, for example, a systematic increase at the most backward angles. The energy dependence of the total cross section for π- is similar to that for π+, although the second resonance peak occurs at a slightly lower energy, and at 900 and 1000 Mev the π- cross section is smaller by a factor 1.6. A comparison is made of the cross sections for π+ photoproduction from hydrogen and deuterium, although the accuracy of this comparison is not high

Infrared observations of Phobos and Deimos from Viking

The surface thermal properties of Phobos and Deimos have been determined from observations made with the Viking Orbiter Infrared Thermal Mapper (IRTM), at wavelengths ranging from 6 to 20 μm. The data, composed of both global and high-resolution infrared photometry of the satellite surfaces as well as eclipse observations, indicate surface material of low thermal conductivity comparable to that of the earth's moon. Values of the thermal inertia I consistent with the data for Phobos are 0.9 ≲ I ≲ 1.6 × 10^(−3) cal cm^(−2) s^(−1/2) K^(−1), and 0.6 ≲ I ≲ 2.0 × 10^(−3) cal cm^(−2) s^(−1/2) K^(−1) for Deimos. It is concluded that both satellites are covered with a vertically uniform layer of finely divided material at least several centimeters thick. Observed differences between brightness temperatures at different wavelengths on Phobos are due mainly to topographic slopes and to the presence of ∼5% by area high inertia or blocky material

The long-period variable stars of M33

Infrared photometry of long-period variables (LPVs) in M33 shows that the majority of those identified up to now are supergiants. The period-luminosity relation for these stars yields a distance of M33 of 760 kpc with a 10 percent uncertainty. This uncertainty primarily reflects the uncertain distance of the Large Magellanic Cloud, although the broader P - L relation of M33 is a contributing factor. Cepheid period-luminosity relations yield a distance at the low end of this range; RR Lyrae stars tend toward the high end. The remaining LPVs are asymptotic giant branch stars. There is one confirmed carbon star among them

Caltech Faint Field Galaxy Redshift Survey IX: Source detection and photometry in the Hubble Deep Field Region

Detection and photometry of sources in the U_n, G, R, and K_s bands in a 9x9 arcmin^2 region of the sky, centered on the Hubble Deep Field, are described. The data permit construction of complete photometric catalogs to roughly U_n=25, G=26, R=25.5 and K_s=20 mag, and significant photometric measurements somewhat fainter. The galaxy number density is 1.3x10^5 deg^{-2} to R=25.0 mag. Galaxy number counts have slopes dlog N/dm=0.42, 0.33, 0.27 and 0.31 in the U_n, G, R and K_s bands, consistent with previous studies and the trend that fainter galaxies are, on average, bluer. Galaxy catalogs selected in the R and K_s bands are presented, containing 3607 and 488 sources, in field areas of 74.8 and 59.4 arcmin^2, to R=25.5 and and K_s=20 mag.Comment: Accepted for publication in ApJS; some tables and slightly nicer figures available at http://www.sns.ias.edu/~hogg/deep

On the Nature of Ryle and Bailey's Candidate Star for the Pulsating Radio Source CP 1919

The energy distribution and spectrum of the "blue" star near CP 1919 indicate that it is a normal early F, main-sequence star and therefore is not likely to be related to the radio source. No regular variations were found in the light from the star, to within an accuracy of a few tenths of 1 per cent

Maffei 1: a New Massive Member of the Local Group?

An extensive collection of observational data is presented which indicates that the recently discovered infrared object Maffei 1 is a highly reddened giant elliptical galaxy at a distance of about 1 Mpc, and thus is probably a new massive member of the Local Group

Multiwavelength Observations of the Low Metallicity Blue Compact Dwarf Galaxy SBS 0335-052

New infrared and millimeter observations from Keck, Palomar, ISO, and OVRO and archival data from the NRAO VLA and IRAS are presented for the low metallicity blue compact dwarf galaxy SBS 0335-052. Mid-infrared imaging shows this young star-forming system is compact (0.31"; 80 pc) at 12.5 microns. The large Br-gamma equivalent width (235 Angstroms) measured from integral field spectroscopy is indicative of a ~5 Myr starburst. The central source appears to be optically thin in emission, containing both a warm (~80 K) and a hot (~210 K) dust component, and the overall interstellar radiation field is quite intense, about 10,000 times the intensity in the solar neighborhood. CO emission is not detected, though the galaxy shows an extremely high global H I gas-to-dust mass ratio, high even for blue compact dwarfs. Finally, the galaxy's mid-infrared-to-optical and mid-to-near-infrared luminosity ratios are quite high, whereas its far-infrared-to-radio and far-infrared-to-optical flux ratios are surprisingly similar to what is seen in normal star-forming galaxies. The relatively high bolometric infrared-to-radio ratio is more easily understood in the context of such a young system with negligible nonthermal radio continuum emission. These new lines of evidence may outline features common to primordial galaxies found at high redshift.Comment: 28 pages including 6 figures; accepted for publication in the Astronomical Journa

Caltech Faint Galaxy Redshift Survey. IX. Source Detection and Photometry in the Hubble Deep Field Region

Detection and photometry of sources in the U_n, G, ℛ, and K_s bands in a 9 × 9 arcmin^2 region of the sky, centered on the Hubble Deep Field, are described. The data permit construction of complete photometric catalogs to roughly U_n = 25, G = 26, ℛ = 25.5, K_s = 20 mag and significant photometric measurements somewhat fainter. The galaxy number density is 1.3 × 10^5 deg^(-2) to ℛ = 25.0 mag. Galaxy number counts have slopes d log N/dm = 0.42, 0.33, 0.27, and 0.31 in the U_n, G, ℛ, and K_s bands, consistent with previous studies and the trend that fainter galaxies are, on average, bluer. Galaxy catalogs selected in the ℛ and K_s bands are presented, containing 3607 and 488 sources in field areas of 74.8 and 59.4 arcmin^2, to ℛ = 25.5 and K_s = 20 mag