Kinman conducted seminal studies of the Milky Way halo, RR Lyrae variables in globular clusters, QSO’s and BL Lac objects.
by Katy Garmany, Abi Saha, and Alistair Walker
Published onJun 26, 2023
Thomas D. Kinman (1928-2023)
Photo credit: Mike Kinman
Dr. Thomas Kinman, an emeritus astronomer at NSF’s NOIRLab, passed away on Monday March 20, 2023, at age 94.
Kinman was a towering figure in the early studies of the diffuse halo of stars that surround our Galaxy: illuminating the nature of and distribution of globular clusters in the Milky Way halo; conducting one of the earliest systematic searches for RR Lyrae stars in the Milky Way halo; and early investigation of QSO’s and BL Lac objects. He was a mentor to many students and post-docs – especially those who passed through Kitt Peak National Observatory (KPNO).
Tom completed his Ph.D. at the University of Oxford in 1953, under the direction of H.H. Plaskett. His earliest published works in the 1950s, emanating from his Ph.D. thesis, concern the study of the Evershed effect in the Sun, and mapping of velocity fields in sunspots. He came to what was then known as the Kitt Peak National Observatory in Tucson in 1969 and remained there the rest of his career.
In the late 1950’s Tom did seminal systematic work on globular clusters. By obtaining distances using RR Lyrae stars, and brightest stars for 75 globular clusters, he was able to improve vastly over prior methods that used the integrated cluster brightness in conjunction with apparent cluster diameter. Working from the Radcliffe Observatory in Pretoria, South Africa, and using the Radcliffe 74-inch telescope (then the largest aperture telescope in the southern hemisphere), he obtained radial velocities to clusters (which are more numerous at southern declinations) that had eluded measurement from northern observatories. Armed with improved distances, velocities and spectral types from integrated light spectra, Kinman was able to deduce a correlation between implied metallicity and spatial distribution, as well as kinematics. In his words, “Clusters with the lowest metal abundance show an extended spherical galactic distribution, and the greater the metal abundance, the more the clusters are concentrated to the galactic plane”. In addition, he noted that the group of clusters poorest in metallicity appear to show smaller galactic rotation than the group relatively richer in metals.
The theme of exploring the structure and properties of the Galactic halo continued through his survey of individual RR Lyrae stars using the Lick astrograph, along strategic lines of sight, ranging from near the Galactic bulge through the north Galactic pole, to the anti-center. To analyze periods and light curves, he invented the so called Lafler-Kinman algorithm, a simple but effective form of the “period dispersion minimization” class of methods, which remains in use to this day, with over 700 citations in ADS. The harvest of RR Lyrae stars from this survey, which probe the halo out to Galactocentric distances of up to 20 kpc, was examined spectroscopically by him and others to explore halo abundances, kinematics, and mass of the Galaxy through the 1970’s and 80’s.
During the 1960’s and onwards, Kinman also became interested in the study of QSO’s, with a focus on their variability and polarization. But he continued his exploration of the Galactic halo using blue horizontal branch and other A and F stars, in addition to the RR Lyrae stars. His studies explored the extended structure of the LMC, and to long period variables in M33. He continued to refine the observational picture of the halo, as the sample of probes grew in the 80’s through the 2010’s.
Tom enjoyed the designation of the “Kinman Dwarf Galaxy”, which he serendipitously discovered in 1965 and named as PHL 293B. It was first referred to as the Kinman Dwarf in a paper Tom wrote with Kris Davidson in 1981. This blue compact dwarf galaxy was popularized in an ESO press release in 2020 when a putative LBV in this galaxy mysteriously disappeared.
As a student, Tom was a member of the Oxford University track team, which at the time included notables like Roger Bannister (the first to run a mile in under four minutes). Tom married Jacqueline Louise Schroedter Kinman in 1963; they met when Tom was working at Lick Observatory. Jackie was trained in astronomy and worked at Lockheed in California, plotting gravity assist trajectories for space probes. They are survived by their two sons, Ian and Michael. Tom was very active in the larger Tucson community. He was a Deacon at St. Michael’s in Tucson, and served as a chaplain at the University Medical Center in Tucson.
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