An interferometric study of molecular emission around NGC 7538 at millimeter wavelengths

Thesis/Dissertation · Mon Jan 01 04:00:00 EST 1990

OSTI ID:5990820

Pratap, P

NGC 7538 is a visible H II region with an associated molecular cloud, situated in the Perseus arm of the Galaxy. A group of infrared sources, IRS 1, IRS 2, and IRS 3, is situated at the interface between the molecular cloud and the visible nebula. Maser emission from OH, H2O, H2CO, CH3OH, and NH3 were detected toward IRS 1. In order to examine the model for the excitation of the formaldehyde (H2CO) maser, proposed by Boland and de Jong (1981), interferometric observations of the cloud around IRS 1 have been made in the J = 1-0 transitions of HCN, HCO(+), and (13)CO. The HCN and HCO(+) maps show the presence of a cavity around IRS 1 which is not seen in the (13)CO maps. Since HCN and HCO(+) trace densities greater than 10(exp 5)cm(exp -3), the cavity indicates a lack of high density material around the H II region. Continuum observations at 88 GHz and 110 GHz result in a 2-component model for the H II region. There is a cool, extended component toward which all the masers are seen. The parameters calculated for this component, along with the H2 densities from the molecular observations, were put into the H2CO master model. The results show that the H2CO gas must be at a distance of 0.011 pc from the H II region for maximum inversion in the H2CO transition and the abundance of H2CO relative to H2 must be approximately 4x10(exp -7). The molecular observations also show that the molecular cloud is extremely clumpy. These clumps around IRS 1 could provide the varying densities required for the other masers observed in the region. The HCO(+) results also indicate the presence of a high density molecular outflow which originates about 15 sec south of IRS 1. The position angle of the outflow agrees with that of a CO outflow detected toward this source. The results imply that there may be another source powering the outflow which is situated south of IRS 1.

• Research Organization: Illinois Univ., Urbana, IL (USA)
• OSTI ID: 5990820
• Country of Publication: United States
• Language: English

Related Subjects

640105* -- Astrophysics & Cosmology-- Galaxies
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ALCOHOLS
ALDEHYDES
AMMONIA
CHEMICAL COMPOSITION
COSMIC GASES
COSMIC RADIO SOURCES
COSMOLOGICAL MODELS
CYANIDES
DATA
ELEMENTS
EMISSION SPECTRA
EXPERIMENTAL DATA
FLUIDS
FORMALDEHYDE
GASES
H2 REGIONS
HYDRIDES
HYDROCYANIC ACID
HYDROGEN
HYDROGEN COMPOUNDS
HYDROXY COMPOUNDS
INFORMATION
INFRARED SPECTRA
INORGANIC ACIDS
MATHEMATICAL MODELS
METHANOL
NEBULAE
NITROGEN COMPOUNDS
NITROGEN HYDRIDES
NONMETALS
NUMERICAL DATA
ORGANIC COMPOUNDS
SPECTRA