Issue |
Astron. Astrophys. Suppl. Ser.
Volume 122, Number 1, April I 1997
|
|
---|---|---|
Page(s) | 95 - 109 | |
DOI | https://doi.org/10.1051/aas:1997295 | |
Published online | 15 April 1997 |
Optical polarimetry, high–resolution spectroscopy and IR analysis of the Chamaeleon I dark cloud*
1
Osservatorio Astronomico di Capodimonte, Via Moiariello, 16, I–80131 Napoli, Italy
2
ITESRE/C.N.R. Bologna, Italy
3
Pomona College, Department of Physics and Astronomy, Claremont, CA, U.S.A.
4
Nordic Optical Telescope, Apartado 474, E-38700 Sta. Cruz de La Palma, Canarias, Spain
Send offprint request to: E. Covino
Received:
21
March
1996
Accepted:
2
July
1996
We present optical polarimetry and high resolution spectroscopy of a
sample of stars toward the Chamaeleon I dark cloud. We use our
polarimetry which includes 33 stars to study
the wavelength dependence of the degree and position angle of
polarization.
From fits to the normalized wavelength dependence of interstellar
polarization,
we derive
estimates of ranging from 4500 Å to 6700 Å, and
PMax ranging from 3 to 8%. The values of
were
found to be well correlated with the IRAS 100 μm intensity, while
PMax was found to increase with EB-V.
High resolution spectra of the Ca II, CH, and CH+ lines were
obtained for 10 stars, which show two components of Ca II in absorption
at 3.0
< 5 km
, and vLSR= -3.0 km
and a single strong molecular CH absorption component at 3.0
<
vLSR
< 5.0 km
.
From our data we found, by interpretation of the various correlations between
the polarimetry, photometry and IRAS fluxes, the following:
the probable presence of shocked molecular gas; a warm molecular CH
component; small dust grains at the edges of the cloud, and larger
grains in the central parts, which are causing the polarization.
Our results provide a consistent picture of the gas and dust content
in the Cha I region, where larger grains, responsible of the starlight
polarization, exist in the center of the cloud, surrounded by
envelopes of warmer molecular and atomic material.
Key words: ISM: chamacleon clouds; dust, extinction; atoms; molecules / polarization / infrared: ISM: continuum
© European Southern Observatory (ESO), 1997