High-latitude dust clouds LDN 183 and LDN 169: distances and extinctions^★

¹ Institute of Theoretical Physics and Astronomy, Vilnius University, Saulėtekio al. 3, Vilnius 10257, Lithuania
e-mail: vytautas.straizys@tfai.vu.lt
² Vatican Observatory Research Group, Steward Observatory, Tucson, AZ 85721, USA
³ Jesuit University Ignatianum, Cracow, Poland
⁴ INAF Astronomical Observatory of Padova, 36012 Asiago, VI, Italy
⁵ SOFIA Science Center, USRA, NASA Ames Research Center, Moffett Field, CA 94035, USA

Received: 8 August 2017
Accepted: 11 December 2017

Abstract

Interstellar extinction is investigated in a 2°× 2° area containing the dust and molecular clouds LDN 183 (MBM 37) and LDN 169, which are located at RA = 15^h 54^m, Dec = − 3°. The study is based on a photometric classification in spectral and luminosity classes of 782 stars selected from the catalogs of 1299 stars down to V = 20 mag observed in the Vilnius seven-color system. For control, the MK types for the 18 brightest stars with V between 8.5 and 12.8 mag were determined spectroscopically. For 14 stars, located closer than 200 pc, distances were calculated from trigonometric parallaxes taken from the Gaia Data Release 1. For about 70% of the observed stars, two-dimensional spectral types, interstellar extinctions A_V, and distances were determined. Using 57 stars closer than 200 pc, we estimate that the front edge of the clouds begins at 105 ± 8 pc. The extinction layer in the vicinities of the clouds can be about 20 pc thick. In the outer parts of the clouds and between the clouds, the extinction is 0.5–2.0 mag. Behind the Serpens/Libra clouds, the extinction range does not increase; this means that the dust layer at 105 pc is a single extinction source.