Multiwavelength study of the high-latitude cloud L1642: chain of star formation^{⋆,⋆⋆,⋆⋆⋆}

¹ Department of PhysicsUniversity of Helsinki, PO Box 64, 00014 Helsinki, Finland
e-mail: johanna.malinen@helsinki.fi
² Eötvös Loránd University, Department of Astronomy, Pázmány P. s. 1/A, 1117 Budapest, Hungary
³ Université de Toulouse, UPS-OMP, IRAP, 31028 Toulouse Cedex 4, France
⁴ CNRS, IRAP, 9 Av. colonel Roche, BP 44346, 31028 Toulouse Cedex 4, France
⁵ Institute of Space and Aeronautical Science, Japan Aerospace Exploration Agency, 229-8510 Kanagawa, Japan
⁶ Department of Astronomy, Graduate School of Science, The University of Tokyo, 113-0033 Tokyo, Japan
⁷ Department of Earth Science and Astronomy, College of Arts and Sciences, the University of Tokyo, Tokyo 153-8902, Japan
⁸ Finnish Centre for Astronomy with ESO (FINCA), University of Turku, Väisäläntie 20, 21500 Piikkiö, Finland
⁹ National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, 181-8588 Tokyo, Japan
¹⁰ Joint ALMA Observatory, Alonso de Cordova 3107 Vitacura, 763 0355 Santiago, Chile
¹¹ Nobeyama Radio Observatory, NAOJ, 462-2, Nobeyama, Minamisaku, Nagano, Japan
¹² Department of Astronomy, Graduate School of Science, the Univ. of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, Japan
¹³ Konkoly Observatory, Research Center for Astronomy and Earth Sciences, Hungarian Academy of Sciences ; Konkoly Thege 15-17, 1121 Budapest, Hungary
¹⁴ Infrared Processing and Analysis Center, MS 220-6, California Institute of Technology, Pasadena CA 91125, USA
¹⁵ Laboratoire AIM, CEA/DSM-CNRS-Université Paris Diderot, IRFU/Service d’Astrophysique, CEA Saclay, 91191 Gif-sur-Yvette, France
¹⁶ College of Science, Ibaraki University, Bunkyo 2-1-1, 310-8512 Mito, Japan
¹⁷ IAS, CNRS (UMR8617), Université Paris-Sud, Bât. 121, 91400 Orsay, France

Received: 11 November 2013
Accepted: 13 January 2014

Abstract

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 σ_e(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.