Search

In earlier papers (Roshi & Anantharamaiah 2000, 2001a), we presented extensive surveys (angular resolution - 2 2 and 2 6 0 ) of radio recombination lines (RRLs) near 327 MHz in the longitude range l = 332 ! 89 using the Ooty Radio Telescope. These surveys have detected carbon lines mostly between l = 358! 20 and in a few positions at other longitudes. This paper presents the observed carbon line parameters in the high-resolution survey and a study of the galactic distribution and angular extent of the line emission observed in the surveys. The carbon lines detected in the surveys arise in "diuse" Cii regions. The l-v diagram and radial distribution constructed from our carbon line data shows similarity with that obtained from hydrogen recombination lines at 3 cm from Hii regions indicating that the distribution of the diuse Cii regions in the inner Galaxy resembles the distribution of the star-forming regions. We estimated the (Cii) 158m emission from diuse Cii regions and find that upto 95% of the total observed (Cii) 158m emission can arise in diuse Cii regions if the temperature of the latter80 K. Our high-resolution survey data shows that the carbon line emitting regions have structures on angular scale 6 0 . Analysis of the dual-resolution observations toward a 2 wide field centered at l= 13:9 and toward the longitude range l= 1:75 to 6:75 shows the presence of narrow (V 15 km s 1 ) carbon line emitting regions extending over several degrees in l and b. The physical size perpendicular to the line-of-sight of an individual diuse Cii region in these directions is>200 pc.

Context. A compact steep spectrum radio source (J0535−0452) is located in the sky coincident with a bright optical rim in the H ii region NGC 1977. J0535−0452 is observed to be ≤100 mas in angular size at 8.44 GHz. The spectrum for the radio source is steep and straight with a spectral index of −1.3 between 330 and 8440 MHz. No 2 μm IR counter part for the source is detected. These characteristics indicate that the source may be either a rare high redshift radio galaxy or a millisecond pulsar (MSP). Aims. We investigate whether the steep spectrum source is a millisecond pulsar. The optical rim is believed to be the interface between the H ii region and the adjacent molecular cloud. If the compact source is a millisecond pulsar, it would have eluded detection in previous pulsar surveys because of the extreme scattering due to the H ii region-molecular cloud interface. Methods. The limits obtained on the angular broadening along with the distance to the scattering screen are used to estimate the pulse broadening. The pulse broadening is shown to be less than a few msec at frequencies >∼5 GHz. We therefore searched for pulsed emission from J0535−0452 at 14.8 and 4.8 GHz with the Green Bank Telescope (GBT). Results. No pulsed emission is detected to 55 and 30 μJy level at 4.8 and 14.8 GHz. Based on the parameter space explored by our pulsar search algorithm, we conclude that, if J0535−0452 is a pulsar, then it could only be a binary MSP of orbital period