K. V. K. Iyengar

Far-infrared observations of NGC 4945 and the Circinus galaxy

Results of observations of NGC 4945 and the Circinus galaxy carried out with a 1 m balloon-borne far-infrared telescope are reported. While only an upper limit (5 σ) of 150 Jy for the 150 μm flux density is obtained for Circinus, the central region of NGC 4945 has been mapped in two bands with effective wavelengths of ∼58 and ∼150 μm. Pointed observations of IRAS, using survey detectors, have been deconvolved to get higher angular resolution intensity maps at 12, 25, 60, and 100 μm, respectively, for both of these galaxies

Far-infrared observations of G351. 6 - 1. 3/G351. 7 - 1. 2 region

An area of about 20 arcmin x 25 arcmin around the H II region-molecular cloud complexes G351.6 - 1.3 and G351.7 - 1.2 has been mapped in a 120 - 300 micron far-infrared band with a spatial resolution of about 1.5 arcmin. Besides the two main sources, five weaker sources have been seen. The IRAS two-dimensional COADD data of the same region at 60 microns and 100 microns have been deconvolved for comparison with the 150 micron intensity map. Combining all the available far-infrared measurements, dust temperature, optical depth, far-infrared luminosity, etc, have been derived for the individual sources in this complex. Spectra have been constructed for the two main sources using all available data. These have been compared with the results of radiation transfer calculations for a spherically symmetric model. Information has been derived on the nature of the dust and its distribution in the main source in G351.6 - 1.3. A mixture of graphite and silicate grains gives a good fit to the observed spectrum. The favored radial dust density distribution is uniform. 30 refs.

Near infrared photometry of some RS CVn systems and candidates

Infrared observations in the J, H, and K bands were made on eleven RS CVn systems. Infrared (IR) excess ≳0.3 mag in the J, H, and K bands was observed from the three systems UX Ari, HR 1099 and σ CrB. Similar observations were also made on the RS CVn candidates HD 26354, 39937, 42449, 51268, and 86005.The IR excess in the RS CVn systems for which near infrared photometric data are available is found to be correlated with the maximum of optical wave amplitude of these systems.The observed excess cannot be explained on the basis of a single process such as: (i) emission from cool spots on the photosphere; (ii) free-free emission from an optically thin circumstellar plasma; or (iii) dust grain emission from circumstellar material.

A 750 mm balloon-borne telescope for far-infrared astronomical observations

A balloon-borne 750 mm Cassegrain telescope has been developed for far-infrared (FIR) astronomical observations. This telescope uses a three-axis stabilised balloon platform with approximately 30 sec of arc (RMS) pointing accuracy. Design and overall properties of this telescope system are presented. Some of the special features of the payload are highlighted, viz., cheap and lightweight mirrors made in epoxy resin; the in-flight relative phase adjustment facility between the detector signal processing system and the secondary mirror chopper. This telescope was flown at an altitude of 32 km on December 10, 1980 for conducting far-infrared observations. The telescope flight details and performance are presented and compared with the design goals. To illustrate the scanning capability of the telescope, a map of Orion-A obtained using it is presented.

Far infrared emission from galaxies

Until recently far infrared (FIR) observations of galaxies were limited to about a dozen bright and/or active galaxies. New photometric data has become available from Infrared Astronomical Satellite (IRAS) on 33 galaxies (most of them faint) from IRAS Circular Nos. 1, 2, and 3 The FIR spectra of these galaxies are similar. The far infrared fluxFFIR in the wavelength interval 9–118 μm of the brighter galaxies is seen to be correlated with the integrated optical magnitudeBT0. The 12 and 25 μm fluxes of these galaxies exhibit the same dependence onBT0 as the 10 and 21 μm fluxes from Seyferts and other emission-line galaxies. This suggests that the galaxies detected by IRAS are some type of active galaxies in accord with the high percentage of these galaxies predicted by Lock and Rowan-Robinson (1983).

The Relationship between Blue and Fir Luminosities of Spiral Galaxies

We have studied optical and infrared properties of 86 galaxies from IRAS circulars, identified in RC-2 and UGC. For these galaxies face-on integrated blue magnitude (B T ° ) and the integrated FIR flux have been estimated and plotted in Fig. 1. With this set of homogeneous blue magnitude (B T ° ≤ 14.5) it is seen that the FIR flux is proportional to the blue band flux. The mean value of LFIR/LB is 6.8.

Far-Infrared (100–200 μm) Photometry of HII Regions with a 1m Balloon Borne Telescope

A 1m balloon-borne telescope has been developed at TIFR for far-infrared (FIR) astronomical observations. The telescope was successfully flown on March 2, 1985 from Hyderabad, India. During the flight RCW 57, RCW 108, RCW 122, W 31, G 351.6-1.3 and Carina nebula were observed. This paper describes the telescope, its performance and very preliminary results from this flight.

A study of the far infrared counterparts of new candidates for planetary nebulae

A search (using the Infrared Astronomical Satellite ‘IRAS’ point source catalogue) for infrared counterparts of the fourteen new candidates for planetary nebulae of low surface brightness detected by Hartl and Tritton (1985), resulted in only five identifications. The infrared sources of four of these candidate nebulae are found within 5 are sec of their optical position and the fifth one within 1 are min. Two of the five nebulae identified with infrared sources are classified as ‘true’, one as ‘probable’ and two as ‘possible’ by Hartl and Tritton (1985). All the five nebulae are found in regions of high cirrus flux at 100 μm. These nebulae are all found to have both point sources as well as small size extended sources (in the IRAS scan windows centred on the sources), with numbers varying from field to field. The infrared emission from these nebulae have dust temperatures ≈100K (characteristic of planetary nebulae). Four of the nebulae appear to be faint in the infrared (just as in the optical band) with total infrared flux of ≲2×10−13 W m−2. Only the PN candidate No. 12 appears to be very bright in the infrared. It is likely that part of the emission is from extraneous sources in the line-of-sight to the nebula.

Infrared observations of beta Cephei and delta Scuti stars

We have made near-infrared photometric observations of nine β-Cephei and eight δ-Scuti stars inJ, H, andK bands. The observed fluxes are in good agreement with those expected according to their spectral types. We conclude that these stars do not have any anomalous emission in these near-infrared bands.

Identification of some of the unidentified EIC-1 sources

We have identified 20 of the 75 unidentified Equatorial Infrared Catalogue Number-1 sources with stars in the BD Catalogue. Two of these are also found in the HD Catalogue.