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Register a new userRadio-Continuum Study of the Nearby Sculptor Group Galaxies. Part 2: NGC 55 at {lambda}=20, 13, 6 and 3 cm
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A series of new radio-continuum ({lambda}=20, 13, 6 and 3 cm) mosaic images focused on the NGC55 galactic system were produced using archived observational data from the Australia Telescope Compact Array. These new images are both very sensitive (down to rms=33 {mu}Jy) and feature high angular resolution (down to <4). Using these newly created images, 66 previously unidentified discrete sources are identified. Of these sources, 46 were classified as background sources, 11 as HII regions and 6 as supernova remnant candidates. This relatively low number of SNR candidates detected coupled with the low number of large HII regions is consistent with the estimated low star formation rate of the galaxy at 0.06 solar masses per year. Our spectral index map shows that the core of galaxy appears to have a shallow spectral index between {alpha} = -0.2 and -0.4. This indicates that the core of the galaxy is a region of high thermal radiation output.
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A series of new radio-continuum (lambda=20 cm) mosaic images focused on the NGC 300 galactic system were produced using archived observational data from the VLA and/or ATCA. These new images are both very sensitive (rms=60 microJy) and feature high angular resolution (<10). The most prominent new feature is the galaxys extended radio-continuum emission, which does not match its optical appearance. Using these newly created images a number of previously unidentified discrete sources have been discovered. Furthermore, we demonstrate that a joint deconvolution approach to imaging this complete data-set is inferior when compared to an immerge approach.
We re-examine a series of archived centimetre radio-continuum observations (lambda=16, 6 and 3 cm) focusing on NGC7793 using the Australia Telescope Compact Array. These new images are both very sensitive (rms=0.011 mJy/beam) and feature reasonably high angular resolution (down to < 3). Using these images, a total of 76 discrete radio sources are identified, of which 57 have been classified. We also studied the radio component of the micro-quasar NGC7793-S26 which shows two distinct regions of somewhat steep spectral index between -0.3 and -0.7.
We present and discuss a new catalogue of 52 compact HII regions in the Small Magellanic Cloud (SMC) and a newly created deep 1420 MHz (lambda=20 cm) radio-continuum image of the N19 region located in the southwestern part of the SMC. The new images were created by merging 1420 MHz radio-continuum archival data from the Australian Telescope Compact Array. The majority of these detected radio compact HII regions have rather flat spectral indices which indicates, as expected, that the dominant emission mechanism is of thermal nature.
We identified 21 new Planetary Nebula (PN) candidates in the Sculptor Group galaxy NGC 55. We determined a most likely distance of 2.00 +/- 0.2 Mpc using the Planetary Nebulae Luminosity Function (PNLF) method. The distance to NGC 55 is larger than previously determined distances, which means that the Sculptor Group is a bit further away from the Local Group than previously thought. The distance to NGC 55 is again similar to the distance of NGC 300, adding support to the suggestion that these galaxies form a bound pair.
We present a series of new high-sensitivity and high-resolution radio-continuum images of M31 at lambda=20 cm ( u=1.4 GHz). These new images were produced by merging archived 20 cm radio-continuum observations from the Very Large Array (VLA) telescope. Images presented here are sensitive to rms=60 mu Jy and feature high angular resolution (<10). A complete sample of discrete radio sources have been catalogued and analysed across 17 individual VLA projects. We identified a total of 864 unique discrete radio sources across the field of M31. One of the most prominent regions in M31 is the ring feature for which we estimated total integrated flux of 706 mJy at lambda=20 cm. We compare here, detected sources to those listed in Gelfand et al. (2004) at lambda=92 cm and find 118 sources in common to both surveys. The majority (61%) of these sources exhibit a spectral index of alpha <-0.6 indicating that their emission is predominantly non-thermal in nature. That is more typical for background objects.
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