VLA H53 α and H92 α Line Observations of the Central Region of NGC 253

Details VLA H53 α and H92 α Line Observations of the Central Region of NGC 253 VLA H53 α and H92 α Line Observations of the Central Region of NGC 253

Oct 2007

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2007aspc..375..279r&link_type=abstract

From Z-Machines to ALMA: (Sub)Millimeter Spectroscopy of Galaxies ASP Conference Series, Vol. 375, proceedings of the conference

Astronomy and Astrophysics

Astronomy

Scientific paper

We present new Very Large Array (VLA) observations toward NGC 253 of the radio recombination line (RRL) H53α (43 GHz) at an angular resolution of 1.5'' × 1.0''. The free-free emission at 43 GHz is estimated to be ˜ 140 mJy, implying a star formation rate of ˜ 2 M&sun; yr-1 in the nuclear region of this starburst galaxy. A reanalysis is made of previously reported H92α observations carried out with angular resolutions of 1.5'' × 1.0'' and 0.36 × 0.21''. Based on the line and continuum emission models used for the 1.5'' × 1.0'' angular resolution observations, the RRLs H53α and H92α are tracers of the high-density (˜ 10^5 cm-3) and low-density (˜ 10^3 cm-3) thermally ionized gas components in NGC 253, respectively. The velocity gradient in the central ˜ 18 pc of the NE component, as observed in both the H53α and H92α lines, is in the opposite direction from the velocity gradient determined from the CO observations. The enclosed virial mass, as deduced from the H53α velocity gradient over the NE component, is ˜ 5 × 10^6 M_&sun; in the central ˜ 18 pc region. The H92α line observations at high angular resolution (0.36'' × 0.21'') reveal a large velocity gradient, along a P.A. ˜ -45° in the NE component, of ˜ 110 km s-1 arcsec-1. The dynamical mass estimated using the high angular resolution H92α data (˜ 7 × 10^6 M_&sun;) supports the existence of an accreted massive object in the nuclear region of NGC 253. A complete version of this paper has been published as Rodríguez-Rico et al. (2006).

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