Wolfgang Batrla

Detection of a strong new maser line of methanol toward DR 21(OH)

The detection of a strong new maser emission line from the 5(-1)-4(0)E transition of methanol toward DR 21(OH) is reported. Interferometric observations with a resolution of 8.3 arcsec x 6.2 arcsec show that the line does not coincide in position with any of the known maser or infrared emission features toward this source. This strongly indicates an excitation mechanism for this methanol maser which is different from the physical conditions leading to the excitation of the water and OH masers. In addition, maser emission is found toward a condensation which has been detected in emission in the 2(11)-2(12) transition of formaldehyde. Besides maser emission, thermal emission lines from several compact sources are detected. Two of these sources are found very close to the OH maser position. 16 references.

Are the NGC 7538 formaldehyde masers really unusual

The molecular cloud around NGC 7358 IRS l has been studied in order to understand the excitation conditions for the unusual H 2 CO masers. Maps in the J=1→0 transition of 13 CO indicate densities with a lower bound of ∼2 × 10 3 cm -3 or more in the cloud around the H II region. The results from the study of various molecular transitions indicate that the conditions required by the Boland & de Jong (1981, A&A, 98) model for the excitation of the H 2 CO maser are not very stringent or unique. The maser can be excited by a compact H II region which is optically thin at millimeter wavelengths

Masers and molecules near the unusual formaldehyde maser NGC 7538 IRS 1

Interferometric observations of the emission from three hyperfine lines of the J = 1-0 transition of HCN have been analyzed in order to characterize the physical conditions in the molecular cloud associated with NGC 7538 IRS 1 and its 6-cm H2CO maser. It is suggested that the lack of HCN emission around IRS 1 and IRS 2 could be the result of the expansion of the H-II region. The presence of high-density clumps around IRS 1 can account for the different excitation requirements for the H2CO and OH masers. 34 refs.

High-resolution molecular observations of NGC 7538 IRS 1

This paper presents results of high-resolution (about 3 arcsec) observations of HCN and HCO(+) toward NGC 7538 IRS 1, carried out with the Berkeley-Illinois-Maryland Array and the NRAO 12-m telescope. The J = 1-0 transition of HCO(+) shows an elongated structure extending from the northeast to the southwest. The wings of the HCO(+) line show the blue lobe of an outflow which is in the same direction as the CO outflow in the source. A detailed comparison between individual HCN and HCO(+) emission peaks shows a definite anticorrelation, which is an indication of different mechanisms which excite the two molecules. 22 refs.

Interferometric observations of the 1-0 transition of HCO(+) toward NGC 7538 IRS 1

Interferometric observations of the molecular cloud toward the compact H II region IRS 1 in NGC 7538 in the 1-0 line of HCO(+) are reported. Employing a resolution of 8.5 arcsec, a highly elongated molecular cloud oriented at position angle 52 deg is found, perpendicular to the axis of the bipolar CO outflow. In perfect alignment with the blueshifted lobe in CO, strong blueshifted line wings are detected in HCO(+). The origin of the flow is at the center of the HCO(+) cloud, 15 arcsec to the south of IRS 1, which is clearly not the source that powers this outflow. So far no other indication of star formation has been detected at this position. 8 references.

A Model for the Maser Source NGC 7538 IRS 1

High resolution observations of the molecular cloud around NGC 7538 IRS 1 in the J=1-0 transition of 13CO show that the lower bound for density in that region is about 2 x 103 cm-3. The study of various molecular transitions and the continuum measurements of the H II region indicate that the conditions required by the Boland and de Jong model for the excitation of the H2CO maser are not very stringent or unique.