Engineering topics

Odewahn, S. C.

Publications and source records attributed to Odewahn, S. C..

3 records

NASA NTRS1995

Abell 548: An X-ray and optical analysis of substructure

X-ray observations of Abell 548 reveal that the hot gas in this cluster is at least as complex as the galaxy distribution. Our ROSAT Position Sensitive Proportional Counter (PSPC) image is used in conjunction with optical data from the Minnesota plate-scanning project and redshift data in the literature to investigate the degree of substructure in the intracluster medium and the galaxy distribution. A548 has several X-ray components: hot gas associated with clumps of galaxies, individual sources, and a newly discovered diffuse component. This diffuse component may be promordial gas falling into the cluster for the first time. The optical data suggest that this cluster consists of four major components, not three (as indicated when velocity data are ignored). Simple models of the orbital dynamics suggest that the cluster may not yet have reached its turnaround radius.

Davis, David S.↗

NASA NTRS1993

Tidal interactions and the formation of Magellanic spiral galaxies

The closest, brightest and best resolved galaxy in the sky, the Large Magellanic Cloud, is a prototype of the late-type disk systems referred to collectively as barred Magellanic spiral galaxies (SBm). These systems occupy a pivotal stage in the Hubble sequence since they represent the transition from spiral disk galaxies to chaotic, irregular galaxies and are characterized by an asymmetric spiral arm which emanates from one end of a high surface brightness bar. We present evidence that the formation of the one-armed spiral morphology involves the tidal interaction with a companion galaxy. In summary the major points of our observational investigation include the following: (1) The vast majority of one-armed spiral galaxies possess bright nearby neighbors which appear to be physically associated. (2) The HI gas distribution and kinematics of one pair of SBm galaxies clearly reveal this system to be tidally interacting. (3) The infrared properties of the bars in two SBm galaxies support optical studies of bar luminosity profiles in late-type systems, and also suggest that the formation of compact star forming regions in these bars may not be uncommon.

Odewahn, S. C.↗

NASA NTRS1992

STARBASE: Database software for the automated plate scanner

The Automated Plate Scanner (APS) of the University of Minnesota, a unique high speed 'flying spot' laser scanner, is currently being used to scan and digitize the 936 O and E plate pairs of the first epoch Palomar Sky Survey. The resultant database will be used to produce a catalog of approximately a billion stars and several million galaxies. The authors describe the ongoing development of a dedicated APS database management system which will be made available to the astronomical community via INTERNET. A specialized DBMS called STARBASE has been written to provide fast access to the hundreds of millions of images collected by the APS. This system provides an initial reduction mode for parameterizing APS images and classifying image types using a novel set of neural network image classifiers. A second analysis mode, which will be that commonly used by the general user, provides for searches of the database which may be constrained by any combination of physical and positional parameters. Through the use of pointer hash trees, the system has been optimized for extremely fast positional searches using either right ascension and declination on the sky or linear X and Y positions on the POSS field. In addition to fast data retrieval, the system provides a graphical interface for displaying scatter plots or histograms of the collected data. In addition, a specialized image display system is being developed to allow the user to view densitometric data for all objects classified as extended by the neural network system. Finally, STARBASE has a flexible programmable interface which allows other programs to access information in the database. This allows users to write applications suited to their particular needs to process APS data.

Odewahn, S. C.↗