Multiwavelength study of the high-latitude cloud L1642: chain of star formation
Résumé
Context. L1642 is one of the two high galactic latitude (|b| > 30°) clouds confirmed to have active star formation.Aims. We examine the properties of this cloud, especially the large-scale structure, dust properties, and compact sources at different stages of star formation.Methods. We present high-resolution far-infrared and submillimetre observations with the Herschel and AKARI satellites and millimetre observations with the AzTEC/ASTE telescope, which we combined with archive data from near- and mid-infrared (2MASS, WISE) to millimetre wavelength observations (Planck).Results. The Herschel observations, combined with other data, show a sequence of objects from a cold clump to young stellar objects (YSOs) 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 the cloud L1642. The western region shows striation towards the 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 has a filamentary tail extending towards the 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 of σe(250 μm) = 0.5−1.5 × 10-25 cm2/H
for different regions of the cloud. Modified black-body fits to the spectral energy
distribution of Herschel and Planck data give emissivity
spectral index β values 1.8–2.0 for the different regions. The
compact sources have lower β values and show an anticorrelation between
T and
β.Conclusions. Markov chain Monte Carlo calculations demonstrate the
strong anticorrelation between β and T errors and the importance of millimetre
wavelength Planck data in constraining the estimates. L1642 reveals a
more complex structure and sequence of star formation than previously known.
Origine : Publication financée par une institution
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