Multiwavelength study of the high-latitude cloud L1642: chain of star
  formation
  L1642 is one of the two high galactic latitude (|b| > 30deg) clouds confirmed
to have active star formation. We examine the properties of this cloud,
especially the large-scale structure, dust properties, and compact sources in
different stages of star formation. We present high-resolution far-infrared and
submm observations with the Herschel and AKARI satellites and mm observations
with the AzTEC/ASTE telescope, which we combined with archive data from near-
and mid-infrared (2MASS, WISE) to mm observations (Planck). The Herschel
observations, combined with other data, show a sequence of objects from a cold
clump to young stellar objects at different evolutionary stages. Source B-3
(2MASS J04351455-1414468) appears to be a YSO forming inside the L1642 cloud,
instead of a foreground brown dwarf, as previously classified. Herschel data
reveal striation in the diffuse dust emission around L1642. The western region
shows striation towards NE and has a steeper column density gradient on its
southern side. The densest central region has a bow-shock like structure
showing compression from the west and a filamentary tail extending towards
east. The differences suggest that these may be spatially distinct structures,
aligned only in projection. We derive values of the dust emission cross-section
per H nucleon for different regions of the cloud. Modified black-body fits to
the spectral energy distribution of Herschel and Planck data give emissivity
spectral index beta values 1.8-2.0 for the different regions. The compact
sources have lower beta values and show an anticorrelation between T and beta.
Markov chain Monte Carlo calculations demonstrate the strong anticorrelation
between beta and T errors and the importance of mm Planck data in constraining
the estimates. L1642 reveals a more complex structure and sequence of star
formation than previously known.
