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27th of November 2017
Class I methanol masers in NGC 253: Alcohol at the end of the bar
by Simon Ellingsen (UTas)
Centre panel: ATCA image of the integrated 36.2-GHz methanol emission (cyan contours at 0.24, 0.34, 0.44 and 0.54 Jy km/s/beam) and 7-mm continuum emission (green contours at 1.25, 2.5, 5, 10, 20, 40 and 80 per cent of 100 mJy/beam) towards NGC 253. The synthesized beam for the ATCA methanol observations is 0.9 arcsec × 3.4 arcsec at a position angle of 8°(shown in the bottom-right corner of image) and combines data collected in three different array configurations. The background image is the integrated CO J = 2–1 emission from Sakamoto et al. (2011) shown on a logarithmic scale. The yellow squares mark the location of molecular clouds identified by Leroy et al. (2015) and the red circle, the location of the 36.4-GHz HC3N maser (Ellingsen et al. 2017). The white stars mark the locations of the seven methanol maser sites identified in the current observations, which we have labelled MM1 through MM7 by increasing right ascension. The dashed black circle marks the pointing centre and size of the full-width at half-maximum (FWHM) primary beam of the IRAM 30-m observations by Martín et al. (2006b). The FWHM primary beam of the current ATCA observations is larger than the size of the image. Side panels: the spectra extracted from the ATCA 36.2-GHz methanol image cube (3 km/s spectral channels) at the location of the labelled white stars in the centre panel. The vertical dashed line marks the systemic velocity of NGC 253 (243 km/s; Koribalski et al. 2004). The x-axis for the spectra is the Barycentric velocity in km/s and the y-axis is the flux in mJy/beam.

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