Radio observations of interstellar CH. I

Journal Article · Thu Jul 01 04:00:00 EDT 1976 · Astrophys. J., Suppl. Ser.; (United States)

DOI:https://doi.org/10.1086/190385· OSTI ID:7266936

Rydbeck, O E.H.; Kollberg, E; Hjalmarson, A; Sume, A; Ellder, J; Irvine, W M

Observations performed at Onsala Space Observatory of the 9cm CH /sup 2/Pi/sub 1;2/, J=1/2 ground-state hyperfine transitions (F=1-0, upper satellite; F=1-1, main line; F=0-1, lower satellite), in the directions of, and in many cases (marked with /sup asterisk/) in extended areas around: Cas A*, W1*, W3*, Ori A*, W12*, W28 (SNR), W31, W43*, W44 (HII), W49A, W51*, M17, Cyg X* (including, e.g., DR 5, DR 15, DR 21, DR 22), ON 1, ON 2, ON 3 (K3--50), NGC 2068*, NGC 7000*, NGC 7538, L134*, L134 N, L1036, L1082, L1399, L1500*/3C 123, L1630*, Heiles's Clouds 1 and 2*, and the Per OB 2 dust cloud* (including NGC 1333 and IC 348) are reported. The observations were made with a traveling-wave maser preamplifier on the Onsala 25.6 m telescope. Zenith system noise temperature was about 34 K.The CH seems to exhibit weak maser characteristics almost everywhere toward H I and H II regions. Observations on and off 3C 123, which is behind L1500, indicate the three CH transitions are probably inverted in dark dust clouds. Absorption was observed only toward M17. Significant departures from equlibrium line intensity ratios appear toward H I and H II regions, but generally not for dark dust clouds. The lower satellite transition is enhanced and, toward H II regions with strong far-infrared emission, is frequently the strongest line. Alternatives are presented for the interpretation of the observations in Heiles's Cloud 2 (G174.3--13.4), where non-LTE line intensity ratios are found. The CH main line excitation tempratures were determined by observations toward and around Cas A. W12, and 3C 123/L1500, are about -15, -10, and -10 K, respectively. Satellite line transitions are generally more inverted than the main line. The OH 1667 MHz line excitation temperature in the H I clouds toward Cas A is about +4 K. The CH observations, together with pertinent information on other interstellar species and far-infrared data on H II regions, are summarized. (AIP)

• Research Organization: Research Laboratory of Electronics and Onsala Space Observatory, Chalmers University of Technology, Gothenburg, Sweden
• OSTI ID: 7266936
• Journal Information: Astrophys. J., Suppl. Ser.; (United States), Journal Name: Astrophys. J., Suppl. Ser.; (United States) Vol. 31:3; ISSN APJSA
• Country of Publication: United States
• Language: English

Related Subjects

640105* -- Astrophysics & Cosmology-- Galaxies
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ABUNDANCE
AMPLIFIERS
CARBON COMPOUNDS
CHEMICAL COMPOSITION
COSMIC RADIO SOURCES
ELECTROMAGNETIC RADIATION
ELECTRONIC EQUIPMENT
ENERGY LEVELS
ENERGY-LEVEL TRANSITIONS
GROUND STATES
H1 REGIONS
H2 REGIONS
HYPERFINE STRUCTURE
INTERSTELLAR GRAINS
MASERS
MICROWAVE AMPLIFIERS
MICROWAVE EQUIPMENT
NEBULAE
PARTICLES
RADIATIONS
RADIOWAVE RADIATION
SPECTRA