Se p 20 05 Infrared and radio study of star forming regions associated with IRAS 19111 + 1048 and IRAS 19110 + 1045

A multiwavelength study of the star forming regions associated with IRAS 19111+1048 and IRAS 19110+1045 has been carried out. These have been simultaneously mapped in two far infrared bands at λ ef f = 130 and 200 µm with ∼ 1 ′ angular resolution using the TIFR 1-m balloon borne telescope. The radio emission from the ionised gas of these regions has been imaged at 1280, 610 and 325 MHz using the Giant Metrewave Radio Telescope, India. A total of 20 compact radio sources have been detected from the high resolution radio map of IRAS 19111+1048 at 1280 MHz (of which one is of non-thermal origin). Assuming these sources to represent exciting zero age main sequence (ZAMS) stars, the initial mass function [ξ(m) ∝ m −a ] is found to be quite steep, with a = 5.3 ± 0.5 for the mass range 14 < m/M ⊙ < 33. The near infrared (NIR) source coinci-dent with the IRAS peak is likely to be an embedded pre-main sequence star. An attempt has been made to identify sources responsible for ionising the gas using NIR sources from 2MASS. The spectral types of the ZAMS stars inferred independently from the radio and NIR measurements match very well for a good fraction of the radio sources having NIR counterparts. For the IRAS 19110+1045 region, seven radio sources have been detected of which two are associated with deeply embedded 2MASS objects. Self consistent radiative transfer modelling aimed at extracting important physical and geometrical details of the two IRAS sources has been carried out using the above cluster of ZAMS stars as the central exciting sources. The best fit models are in good agreement with the observed spectral energy distributions. A uniform density distribution of dust and gas is implied for both the sources. The extents of ionised gas, number of ZAMS stars, presence of deeply embedded sources and lower value of L/M for the cloud, support the youth of IRAS 19110+1045 visa -vis its neighbour, IRAS 19111+1048, consistent with earlier studies.