Discovery of Luminous Star Formation in PMN1452-5910/IRAS14482-5857: the Pterodactyl Nebula

Abstract

We present sensitive 1-3 GHz ATCA radio continuum observations of the hitherto unresolved star forming region known as either IRAS14482-5857 or PMN1452-5910. At radio continuum frequencies, this source is characterised by a "filled-bubble" structure reminiscent of a classical HII region, dominated by three point sources, and surrounded by low-surface-brightness emission out to the $3^{\prime }\times 4^{\prime }$ source extent observed at other frequencies in the literature. The infrared emission corresponds well to the radio emission, with polycyclic aromatic hydrocarbon emission surrounding regions of hot dust towards the radio bubbles. A bright 4.5 $\mu$m point source is seen towards the centre of the radio source, suggesting a young stellar object. There is also a linear, outflow-like structure radiating brightly at 8 and 24 $\mu$m towards the brightest peak of the radio continuum. In order to estimate the distance to this source, we have used Mopra Southern Galactic Plane CO Survey ${}^{12}$CO(1-0) and ${}^{13}$CO(1-0) molecular line emission data. Integrated-intensity, velocity at peak intensity and line-fitting of the spectra all point towards the peak centred at $v_{LSR}$=-1.1 km/s being connected to this cloud. This infers a distance to this cloud of ~12.7 kpc. Assuming this distance, we estimate a column density and mass towards IRAS14482-5857 of ~$1.5\times 10^{21}$ cm${}^{-2}$ and $2\times 10^4$ $M_{\odot }$, implying that this source is a site of massive star formation. Reinforcing this conclusion, our broadband spectral fitting infers dust temperatures of 19 and 110K, emission measures for the sub-pc radio point-source of emission measure $EM\sim 10^{6-7}$ pc cm${}^{-6}$, electron densities of $n_e\sim 10^3$ cm${}^{-3}$ and photon ionisation rates of $N_{Ly}10^{46-48}$ s${}^{-1}$. The evidence strongly suggests that IRAS14482-5857 is a distant, and hence intense site of massive star-formation.

arXiv comment11 pages, 12 figures, accepted for publication in the Astronomical Journal

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