ALMA and VLA observations of recombination lines and continuum toward the Becklin-Neugebauer object in Orion
Abstract
Compared to their centimeter-wavelength counterparts, millimeter recombination lines (RLs) are intrinsically brighter and are free of pressure broadening. We report observations of RLs (H30α at 231.9 GHz, H53α at 42.9 GHz) and the millimeter and centimeter continuum toward the Becklin-Neugebauer (BN) object in Orion, obtained from the Atacama Large Millimeter/submillimeter Array (ALMA) science verification archive and the Very Large Array (VLA). The RL emission appears to be arising from the slowly-moving, dense (Ne = 8.4 × 106 cm-3) base of the ionized envelope around BN. This ionized gas has a relatively low electron temperature (Te < 4900 K) and small (≪ 10 km s-1) bulk motions. Comparing our continuum measurements with previous (non)detections, it is possible that BN has large flux variations in the millimeter. However, dedicated observations with a uniform setup are needed to confirm this. From the H30α line, the central line-of-sight LSR velocity of BN is 26.3 km s-1.
Appendices are available in electronic form at http://www.aanda.org- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- November 2012
- DOI:
- 10.1051/0004-6361/201220330
- arXiv:
- arXiv:1210.1413
- Bibcode:
- 2012A&A...547L...3G
- Keywords:
-
- stars: massive;
- HII regions;
- radio continuum: ISM;
- radio lines: ISM;
- Astrophysics - Astrophysics of Galaxies;
- Astrophysics - Cosmology and Nongalactic Astrophysics;
- Astrophysics - Solar and Stellar Astrophysics
- E-Print:
- To appear in Astronomy and Astrophysics as a Letter to the editor. Corrections to mm fluxes. Discussion about flux variability shortened. Physical properties of ionized gas remain the same. Table 1 to main text rather than online only. Language edited