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Proposal Identication No.: A1704 Date Received: 2002-Jun-02 16:57:32
Technical Page
Proposal Type: Regular
General Category: Astronomy
Sub-Category: Spectroscopy
Observation Category: Galactic
Total Time Requested: 12 Hours
Proposal Title: Environments of UCHII regions: Carbon Recombination Lines as Probes of Ultra-
Dense PDRs
ABSTRACT:
A majority of extended HII regions appear to be density bounded, implying that no cold CII regions will form
around them. In fact, there are only a handful of HII regions that have CII emission associated with them.
However, UCHII regions are often surrounded by dense molecular material and thus appear to be ideal regions to
search for carbon recombination lines. In fact, recent VLA observations were very successful in detecting carbon
lines near UCHII regions. We propose to make a survey of carbon lines toward a selected set of UCHII regions.
Our objectives are : (1) to understand the relationship between the morphological type of UCHII region and
carbon line forming region; (2) to determine the physical properties of the neutral material in the vicinity of UCHII
region. If dense molecular material connes the UCHII regions, then it should be detectable in carbon
recombination lines near 8 GHz. If the line is not detected, we will be able to set stringent limits on the
temperature and density of the molecular material in the surrounding medium.
Name Institution E-mail Phone Student
Anish Roshi National Radio As-
tronomy Observatory
aroshi@nrao.edu 1-304-456-2130 no
Service Observing Request Remot e Observing Request
X None X No
All of the observing run. Maybe
Part of the observing run. Yes
Queue Observing
Instrument Setup
X-high
Atmospheric Observation Instruments:
1

Special Equipment or setup: none
RFI Considerations
Frequency Ranges Planned
2