Engineering topics

Zoonematkermani, S.

Publications and source records attributed to Zoonematkermani, S..

3 records

NASA NTRS1994

A 5 GHz VLA survey of the galactic plane

We have used the Very Large Array (VLA) to survey the inner Galaxy (absolute value of b less than 0.4 deg, l = 350-40 deg) at 5 GHz to a limiting sensitivity of between 2.5 and 10 mJy. The survey has resulted in a catalog of 1272 discrete sources (including 100 sources outside the formal survey area) of which we have temtatively identified approximately 450 as ultracompact H II regions and approximately 45 as planetary nebulae. Approximately 30% of the radio sources are detected in the Infrared Astronomy Satellite (IRAS) Point source Catalog. The results confirm a scale height of only 30 pc for ultracompact H II regions. We show that source lists generated from the IRAS Point Source Catalog alone suffer serious selection effects; the combination of the IRAS and radio surveys allows us to produce a much more complete census of the regions of massive star formation in our Galaxy.

Becker, Robert H.↗

NASA NTRS1992

Compact radio sources near the Galactic plane

The results of the extension of the 20-cm Galactic-plane survey reported by Zoonematkermani to Galactic latitudes of +/- 1.8 deg over the central region of the Milky Way are reported. A total of 1457 discrete radio sources down to flux densities of less than about 5 mJy, and 95 percent completion is achieved at 20 mJy. A detailed comparison of all radio sources from the survey in this longitude range with the IRAS Point Source Catalog provides classification for 13 percent of the objects, including 159 compact H II regions, and nearly 100 planetary nebulae, over 70 of which are identified. The identity of the remaining radio sources is discussed.

Helfand, D. J.↗

NASA NTRS1987

The Einstein survey of the young stars in the Orion Nebula

The Orion Nebula is the best studied site of recent star formation in the Galaxy. The complete Einstein Observatory survey of the Orion Nebula covering a 2 deg x 2 deg region centered on the Trapezium is reported. An X-ray mosaic is presented for the Nebula along with a complete X-ray catalogue for this very young cluster. Approximately 150 distinct sources were found in this 4 sq deg region; spectral types and colors were obtained for about 1/2 of the optical counterparts of these sources. Comparison of the variability of the Orion X-ray sources with those found in the Rho Ophiuchi cloud leads to the conclusion that the Orion sources' variability is also likely to result from continual flaring activities. Eleven new late B stars associated with X-ray emission far exceeding that expected from early type stars were discovered. The X-rays may originate from pre-main sequence companions to these stars; a T-Tauri star of the same age would have the correct L sub x. Comparison of the solar type stars in Orion with those in the Pleiades, the Hyades, and the field suggests that the decay of activity with age is most appropriately described by an exponential, rather than a power law fit.

Zoonematkermani, S.↗