INSTITUTE OF THEORETICAL PHYSICS AND ASTRONOMY, VILNIUS UNIVERSITY Justas Zdanaviˇcius INTERSTELLAR EXTINCTION IN THE DIRECTION OF THE CAMELOPARDALIS DARK CLOUDS Doctoral dissertation Physical sciences, physics (02 P), astronomy, space research, cosmic chemistry (P 520) Vilnius, 2006 Disertacija rengta 1995 - 2005 metais Vilniaus universiteto Teorin˙es fizikos ir astronomijos institute Disertacija ginama eksternu Mokslinis konsultantas prof.habil.dr. V. Straiˇzys (Vilniaus universiteto Teorin˙es fizikos ir astronomijos institutas, fiziniai mokslai, fizika – 02 P) VILNIAUS UNIVERSITETO TEORINES˙ FIZIKOS IR ASTRONOMIJOS INSTITUTAS Justas Zdanaviˇcius TARPZVAIGˇ ZDINˇ EEKSTINKCIJA˙ ZIRAFOSˇ TAMSIU¸JU¸ DEBESU¸KRYPTIMI Daktaro disertacija Fiziniai mokslai, fizika (02 P), astronomija, erdv˙es tyrimai, kosmin˙e chemija (P 520) Vilnius, 2006 CONTENTS PUBLICATIONONTHESUBJECTOFTHEDISSERTATION .....................5 1. INTRODUCTION ................................................................6 2. REVIEWOFTHELITERATURE ................................................8 2.1. InvestigationsoftheinterstellarextinctioninCamelopardalis ..................8 2.2. Distinctiveobjectsinthearea ................................................10 2.3. Extinctionlawintheinvestigatedarea .......................................11 2.4. Galacticmodelsandluminosityfunctions .....................................11 2.5. SpiralstructureoftheGalaxyintheinvestigateddirection ...................12 3. METHODS ......................................................................14 3.1. Photoelectricobservationsandequipment ....................................14 3.1.1. AreaA1 ................................................................. 14 3.1.2. AreaA2 ................................................................. 14 3.1.3. AreaB ...................................................................15 3.2. CCDobservationandreductions .............................................15 3.2.1. CCDlinearitytesting ....................................................16 3.2.2. ObservationsinAreaC andreductions ...................................16 3.3. Theinterstellarextinctionlaw ................................................18 3.4. Photometricclassification ....................................................19 3.4.1. ClassificationinAreaA1 .................................................19 3.4.2. ClassificationinAreaA2 .................................................20 3.4.3. ClassificationinAreaB ..................................................20 3.4.4. ClassificationinAreaC ..................................................21 3.5Accuracyofstellarparameters ................................................22 4. RESULTSANDDISCUSSION ...................................................23 4.1. Interstellarreddeninglaw ....................................................23 4.1.1. Reddeninglawintheopticalrange .......................................23 4.1.2. Reddeninglawintheultraviolet ..........................................25 4.1.3. Reddeninglawintheinfrared ............................................25 4.1.4. Wavelengthdependenceofpolarization ...................................27 4.2. Interstellarextinction ........................................................27 4.2.1. InterstellarextinctioninAreaA1 .........................................27 4.2.2. InterstellarextinctioninAreaA2 .........................................29 4.2.3. InterstellarextinctioninAreaB ..........................................31 4.2.3.1. Interstellarextinctionvs. distance: largescale ........................33 4.2.3.2. Interstellarextinctionvs. distance: smallscale .......................35 4.2.4. InterstellarextinctioninAreaC ..........................................36 4.2.4.1. Generalviewofthearea .............................................37 4.2.4.2. Theextinctionatsmalldistances .....................................39 4.2.4.3. Theextinctionatlargedistances .....................................39 4.2.4.4. Limitingmagnitudeeffectsanddiscussion ............................40 4.2.5. TheCamOB3association ................................................42 4.3. Spacedistributionofstars ....................................................42 4.3.1. Somestatisticaldata .....................................................45 4.3.2. Theobservedspacedensities .............................................45 4.3.3. Theobservedluminosityfunction .........................................50 4.3.4. Onthecompletenessoftheobservedstarsample .........................50 4.4. Comparisonoftheresults ....................................................53 3 5. THEMAINRESULTSANDCONCLUSIONS ...................................54 5.1. SUMMARYOFTHEMAINRESULTS ......................................54 5.2. CONCLUSIONS .............................................................54 6. REFERENCES ..................................................................56 ACKNOWLEDGMENTS ...........................................................60 APPENDIX ........................................................................61 4 PUBLICATIONS ON THE SUBJECT OF THE DISSERTATION 1. Zdanaviˇcius K., Zdanaviˇcius J., Kazlauskas A. 1996, ”Interstellar Extinction in the Camelopardalis Dark Clouds”, Baltic Astronomy, 5, 563 2. Zdanaviˇcius J., Cernisˇ K., Zdanaviˇcius K., Straiˇzys V. 2001, ”Photometric Classifi- cation of Stars and the Interstellar Extinction near the Camelopardalis and Perseus Border”, Baltic Astronomy, 10, 349 3. Zdanaviˇcius J., Zdanaviˇcius K. 2002, ”Photometry and Classification of Stars along the Camelopardalis and Perseus Border”, Baltic Astronomy, 11, 75 4. Zdanaviˇcius J., Straiˇzys V., Corbally C. J. 2002, ”Interstellar Extinction Law near the Galactic Equator along the Camelopardalis, Perseus and Cassiopeia Border”, A&A, 392, 295 5. Zdanaviˇcius J., Zdanaviˇcius K. 2002, ”Interstellar Extinction along the Camelopardalis and Perseus Border”, Baltic Astronomy, 11, 441 6. Zdanaviˇcius J., Zdanaviˇcius K. 2003, ”A New CCD Camera at the Mol˙etai Observa- tory”, Baltic Astronomy, 12, 642 7. Zdanaviˇcius J., Zdanaviˇcius K. 2005, ”CCD Photometry and Classification of Stars in a Camelopardalis Area”, Baltic Astronomy, 14, 1 8. Zdanaviˇcius J., Zdanaviˇcius K., Straiˇzys V. 2005, ”Interstellar Extinction in the Di- rection of the Association Cam OB3”, Baltic Astronomy, 14, 31 9. Zdanaviˇcius J., Zdanaviˇcius K., Straiˇzys V. 2005, ”Space Distribution of Stars in the Direction of the Association Cam OB3”, Baltic Astronomy, 14, 313 CONTRIBUTION RELATED TO THE DISERTATION AT THE INTERNATIONAL CONFERENCES 1. Zdanaviˇcius K., Zdanaviˇcius J., Kazlauskas A. ”Interstellar Reddening in the Camelo- pardalis Dark Clouds”, in ”Photometric Systems and Standard Stars”, Vilnius 1995 August 14-16. 2. Zdanaviˇcius J., Zdanaviˇcius K. ”A New CCD Camera at the Moletai Observatory”, in Stellar Photometry: Past, Present and Future, Vilnius 2003 September 17-20. 3. Zdanaviˇcius J., Zdanaviˇcius K., Straiˇzys V. ”CCD Observations and Photometric Clas- sification of Stars at the Mol˙etai Observatory”, in the ”CrAO60 Conference”, Crimea, Nauchny, Ukraine 2005 September 11-18. 5 1. INTRODUCTION For better understanding the structure and evolution of our Galaxy, we need infor- mation about physical parameters of stars and interstellar matter and their distribution in space. The Galaxy contains about 300 billion stars, but only a small part of them is accessible for our investigation. Usually studies are concentrated only in the chosen directions and areas. Only a small part of the Galactic longitudes and latitudes is in- vestigated. For investigation of distant objects, especially near the Galactic plane, we need, in addition, the value of interstellar extinction in their directions. Usually, the interstellar extinction in different sky areas is evaluated by using stars for which photo- metric and spectral classification data are available. This has been done only in a small number of sky areas. Therefore, in many directions new investigations of interstellar extinction are needed. Among the least investigated directions in the Milky Way are dark clouds in the Camelopardalis constellation (Galactic longitudes between 140◦ and 150◦). In this direction our view crosses the Orion spiral arm, the Perseus arm and the Outer arm. A discontinuity of the Milky Way brightness at the Galactic longitudes 140◦–170◦ has been well known since the first wide-field surveys of the Galactic system. At these longitudes all the tracers of the Perseus spiral arm disappear. The Milky Way reappears only at = 170◦, near the Auriga border. We may suspect that this blocking of the light of distant stars probably is due to the crowding of dust clouds near the Galactic equator, which probably belong to the local Orion spiral arm. The Camelopardalis dark cloud-region, which occupies a large area of the Galactic equator ( =140◦–150◦), is still a poorly investigated area. The distances of the clouds and their extinctions are known with a low accuracy and only in some occasional direc- tions. This section of the Galaxy remains also a poorly investigated region considering interstellar extinction and the Galactic structure. These are the main reasons why we have chosen for investigation an area at the Camelopardalis border with Perseus and Cassiopeia. The main aim of the dissertation The main goal of this work was a comprehensive photometric investigation of the Milky Way region at Galactic longitudes 140◦–150◦ in the direction of the Cameloparda- lis dark clouds in order