A line confusion limited millimeter survey of Orion KL (I): sulfur
  carbon chains
  We perform a sensitive (line confusion limited), single-side band spectral
survey towards Orion KL with the IRAM 30m telescope, covering the following
frequency ranges: 80-115.5 GHz, 130-178 GHz, and 197-281 GHz. We detect more
than 14 400 spectral features of which 10 040 have been identified up to date
and attributed to 43 different molecules, including 148 isotopologues and lines
from vibrationally excited states. In this paper, we focus on the study of OCS,
HCS+, H2CS, CS, CCS, C3S, and their isotopologues. In addition, we map the OCS
J=18-17 line and complete complementary observations of several OCS lines at
selected positions around Orion IRc2 (the position selected for the survey). We
report the first detection of OCS v2 = 1 and v3 = 1 vibrationally excited
states in space and the first detection of C3S in warm clouds. Most of CCS, and
almost all C3S, line emission arises from the hot core indicating an
enhancement of their abundances in warm and dense gas. Column densities and
isotopic ratios have been calculated using a large velocity gradient (LVG)
excitation and radiative transfer code (for the low density gas components) and
a local thermal equilibrium (LTE) code (appropriate for the warm and dense hot
core component), which takes into account the different cloud components known
to exist towards Orion KL, the extended ridge, compact ridge, plateau, and hot
core. The vibrational temperature derived from OCS v2 = 1 and v3 = 1 levels is
about 210 K, similar to the gas kinetic temperature in the hot core. These OCS
high energy levels are probably pumped by absorption of IR dust photons. We
derive an upper limit to the OC3S, H2CCS, HNCS, HOCS+, and NCS column
densities. Finally, we discuss the D/H abundance ratio and infer the following
isotopic abundances: 12C/13C=45+-20, 32S/34S=20+-6, 32S/33S=75+-29, and
16O/18O=250+-135.
