Robert M. Price

Two views of the Andromeda Galaxy H-alpha and far infrared

A complete H-alpha image of the Andromeda Galaxy (M31) is presented allowing the first direct measurement of the total H-alpha luminosity which is (7.3 +/- 2.4) x 10(exp 6) solar luminosity. The H-alpha emission is associated with three morphologically distinct components; a large scale star-forming ring, approximately 1.65 deg in diameter, contributing 66% of the total H-alpha emission, a bright nucleus contributing 6% of the total H-alpha emission with the remaining 28% contributed by a previously unidentified component of extended and filamentary H-alpha emission interior to the star forming ring. The correspondence between the H-alpha image and the Infrared Astronomy Satellite (IRAS) far-infrared high resolution image is striking when both are convolved to a common resolution of 105 arcsec. The close correspondence between the far-infrared and H-alpha images suggests a common origin for the two emissions. The star-forming ring contributes 70% of the far-infrared luminosity of M31. Evidence that the ring emission is energized by high mass stars includes the fact that peaks in the far-infrared emission coincide identically with H II regions in the H-alpha image. In addition, the far-infrared to H-alpha luminosity ratio within the star-forming ring is similar to what one would expect for H II regions powered by stars of spectral types ranging between O9 and B0. The origin of the filamentary H-alpha and far-infrared luminosity interior to the star-forming ring is less clear, but it is almost certainly not produced by high mass stars.

VLA observations of 91 quasars at Z greater than 0.35 and less than 1

We present NRAO-VLA 4 snapshot observations of 91 radio quasars with 0.35 < z < 1 chosen to sample the redshift-luminosity plane as widely as possible, to enable the study of the radio evolution of quasars. Their evolution has been discussed by Hutchings, Price, & Gower and Neff & Hutchings. The observations were made at 6 and 20 cm in the A-array and have ∼ 0.″4 and 1.″2 resolution, respectively. The primary purpose of this paper is to present the radio images and image parameters of a morphologically unbiased and uniformly reduced sample of quasars. We include only a brief discussion of the sample selection, observations, and data reductions. This is the second sample in a series of papers presenting tbe VLA observations of quasars

New results on the radio-far-infrared relation for galaxies

The radio-FIR relation has been decomposed into thermal bremsstrahlung-FIR and synchrotron-FIR relation for a sample of 31 galaxies. Both radio emission components are tightly correlated with the FIR emission for early and late-type spiral as well as irregular galaxies. It follows that any mixture of the radio components produces a tight universal radio-FIR relation. At high radio frequencies, thermal bremsstrahlung can dominate the radio emission over a large range of luminosities so that the slope of the radio-FIR relation approaches that of the thermal bremsstrahlung-FIR relation and is therefore close to unity (0.97 +/- 0.02). At lower frequencies, synchrotron emission dominates and the slope approaches that of the synchrotron-FIR ratio which is significantly steeper than unity (1.33 +/- 0.10). The results are consistent with a scenario in which the FIR luminosities of galaxies scale in direct proportion to the star formation rate.

X-Ray emission from poor clusters of galaxies

The X-ray, optical, and radio properties of a sample of 25 poor clusters of galaxies were investigated on the basis of published observations. The X-ray emission from poor clusters was classified into morphological types depending on whether they contain a dominant galaxy or not, as was done by Jones and Forman (1984) for rich clusters. It was found that 13 of the clusters could be classified as D-type clusters, where the peak coincides with a dominant galaxy. For the five T-type clusters in this group, it was found that radio sources are detected almost three times as often as in D-type clusters, indicating that the production of radio sources in poor clusters may be dependent on the shape of the cluster potential well. The optical properties of seven clusters that were not detected at X-ray wavelengths are indistinguishable from those of the X-ray detected clusters, indicating that all poor clusters have a hot intracluster medium. 52 refs.

Radio evolution of quasars at z less than 1

A sample of 128 quasars with redshifts less than 1.0 observed at 6 cm and 20 cm with the A array of the VLA are presented and discussed. It is found that the source size envelope varies with both redshift and core luminosity, being smaller for high values of both. More luminous sources have greater core dominance, and the largest sources tend to have low-luminosity cores. Core variability tends to increase with luminosity and with redshift. The distribution of the ratio of core-lobe distances is consistent with a simple model of initial alternating ejection at nonrelativistic velocities. The ratios of lobe luminosities also show no evidence of relativistic beaming. The evidence suggests a general evolution of individual sources in which the source is initially a luminous core only, whose luminosity falls with time. The lobes develop initially as a one-sided structure, but eventually form large triple sources with a fading core. 21 references.

21 cm emission in QSOs and active galaxies

Observations of H I emission from galaxies containing QSOs and active nuclei, obtained with the Arecibo telescope, are reported, including new data on 17 objects, new detections in four of them, improved profiles in five more, and possible detections in several others. These results are discussed together with published observations of five other objects by the same telescope. This sample lies at higher luminosity and redshift than surveys of Seyfert galaxies. The line profiles are generally broad and asymmetric, probably due to contamination by associated or interacting galaxies. There is a close agreement with optical NLR redshifts, but a mismatch of some 50 km/s is suggested. Overall, the H I masses are lower than for normal galaxies, but they appear to correlate with the nuclear luminosity. This may connect fueling events and ionization by the nuclear radiation. 16 references.