Investigation of Star Forming Regions in Cepheus
Total Page：16
File Type：pdf, Size：1020Kb
VILNIUS UNIVERSITY MARIUS MASKOLIUNAS¯ INVESTIGATION OF STAR FORMING REGIONS IN CEPHEUS Doctoral Dissertation Physical Sciences, Physics (02 P) Vilnius, 2014 Doctoral Dissertation was completed during 2008–2013 at Vilnius University, In- stitute of Theoretical Physics and Astronomy Scientific supervisor: Dr. Justas Zdanaviciusˇ (Vilnius University, Institute of Theoretical Physics and As- tronomy, Physical sciences, Physics – 02 P) Scientific advisor: Habil dr. Kazimieras Zdanaviciusˇ (Vilnius University, Institute of Theoretical Physics and Astronomy, Physical sciences, Physics – 02 P) 2 VILNIAUS UNIVERSITETAS MARIUS MASKOLIUNAS¯ CEFEJO˙ ZVAIGˇ ZDˇ EDAROS˙ RAJONU¸TYRIMAS Daktaro disertacija Fiziniai mokslai, fizika (02 P) Vilnius, 2014 Daktaro disertacija rengta 2008–2013 metais Vilniaus universiteto Teorines˙ fizikos ir astronomijos institute Mokslinis vadovas: Dr. Justas Zdanaviciusˇ (Vilniaus universiteto Teorines˙ fizikos ir astronomijos in- stitutas, fiziniai mokslai, fizika – 02 P) Mokslinis konsultantas: Habil dr. Kazimieras Zdanaviciusˇ (Vilniaus universiteto Teorines˙ fizikos ir as- tronomijos institutas, fiziniai mokslai, fizika – 02 P) 4 Table of Contents Introduction 8 Publicationsonthesubjectofthedissertation . ..... 14 Presentationsatinternationalconferences . ..... 15 Aimsofthestudy .............................. 16 Tasksofthestudy.............................. 16 Scientificnovelty .............................. 16 Practicalimportance. 17 Resultsandstatementspresentedfordefence. .... 17 Personalcontribution . .. 18 Thesisoutline ................................ 18 1. Observational data 19 1.1. ReflectionnebulaNGC7023 . 19 1.1.1. Thecatalog .......................... 21 1.2. DarkcloudTGU619 ......................... 23 1.2.1. Thecatalog .......................... 23 1.3. ClustersNGC7129andNGC7142. 24 1.3.1. ObservationswiththeMaksutovtelescope . 24 1.3.2. Thecatalog .......................... 24 1.3.3. Observationswiththe1.8mVATTtelescope . 25 1.3.4. ThecatalogsintheNGC7129andNGC7142areas . 27 2. Two-dimentional classification of stars 29 2.1. Classification of stars in the NGC 7023 and TGU 619 areas . .... 29 2.2. Classification of stars in the NGC 7129 and NGC 7142 areas .... 31 3. Distance determination to the star forming regions 34 3.1. DistancetothereflectionnebulaNGC7023 . 34 5 3.2. DistancetothedarkcloudTGU619 . 41 3.3. ParametersoftheclustersNGC7129andNGC7142 . 45 3.3.1. Distance of the cloud TGU 645 and the cluster NGC 7129 . 45 3.3.2. 2MASS two-color diagram for the cluster NGC 7129 . 50 3.3.3. DistanceandageoftheclusterNGC7142 . 52 4. Results and discussion 58 4.1. ReflectionnebulaNGC7023 . 58 4.2. DarkcloudTGU619 ......................... 59 4.3. OpenclustersNGC7129andNGC7142. 60 5. Main results and conclusions 66 References 68 Acknowledgements 76 Appendix 77 A. Photometry of stars 77 A.1. PhotometryofstarsintheTGU619area . 77 A.2. Photometry of stars in the directions of NGC 7129 and NGC 7142 . 106 A.3. DeepphotometryofstarsintheNGC7129area . 153 A.4. DeepphotometryofstarsintheNGC7142area . 157 B. Classification of stars 181 B.1. ClassificationofstarsintheNGC7023area . 181 B.2. ClassificationofstarsintheTGU619cloudarea . 191 B.3. Classification of stars in the NGC 7129 area observed with VATT. 206 B.4. Classification of stars in the NGC 7129 area observed with Maksutov 208 B.5. ClassificationofstarsintheNGC7142area . 210 C. Finding charts of stars 222 Finding charts in the NGC 7023 area 223 6 Finding charts in the TGU 619 area 230 Finding charts in the NGC 7129 and NGC 7142 areas 237 7 Introduction The space between stars contains the interstellar matter in the form of atomic and molecular gas and dust. Most of the interstellar dust form the clouds which are concentrated in the disk of the Galaxy, mostly in spiral arms. Despite their small contribution to the mass of material in interstellar clouds (only about 1%), dust par- ticles play an important role due to their capability to absorb and scatter the light of stars located behind the clouds. The combined effect of absorption and scattering is called interstellar extinction which is a measure of weakening of star light. Because the dependence of interstellar extinction on wavelength (the interstellar extinction law) the light of stars located behind the dust clouds becomes redder and fainter. The dust and molecular clouds are the sites of star formation due to gravitational contraction of occasional condensations of the interstellar matter and partly due to shock waves from supernova explosion. The cloud, in which stars younger than 10 Myr are usually called as star-forming region. If hot massive stars are predominantly present in such a region, they are called an OB-associations. One of the most active star-forming regions is located in the Cepheus constella- tion, at the Galactic longitudes between 100◦ and 120◦In˙ this sky region, the band of the Milky Way splits into two branches, with one branch stretching approximately along the Galactic equator and the another branch forming the so-called Cepheus Flare. The latter branch separates from the main Milky Way band in the northern part of the Cygnus constellation and extends, at some angle to the Galactic equator, towards the North Celestial Pole in Ursa Minor. The Cepheus Flare contains a few star forming regions, which have recently been described by Kun et al. (2008) in the Handbook of Star Forming Regions, published by the Astronomical Society of the Pacific. Since these regions are very important to understanding the evolution of the Galaxy, especially its spiral structure, we selected some of these regions for the present photometric investigation. In our investigation we applied the Vilnius seven-color photometric system at the mean wavelengths of its passbands 345, 374, 405, 466, 516, 544 and 656 nm. The system was developed many years ago in 8 the Vilnius Observatory for the classification of all types of stars, especially in the presence of large and variable interstellar extinction. Using the radiation intensities measured in the passbands of the Vilnius system, it is possible to determine spec- tral classes (or temperatures), luminosity classes (or absolute magnitudes), and the values of interstellar reddening and extinction. The young stellar objects (YSO) can be also identified adding infrared magnitudes from the published catalogs of the photometric surveys in a number of infrared wavelengths (2MASS, WISE, Spitzer, Akari, etc.) enables a more complete photometric identification of YSOs. All this makes the Vilnius system very useful in the investigation of star forming regions, young open clusters and associations. The following objects have been selected for the present investigation: 1. The area around the reflection nebula NGC 7023; 2. The area in the nearby dust cloud TGU 619; 3. The area around the reflection nebula and a very young open cluster NGC 7129, which contains also the old open cluster NGC 7142 reddened by the same dust cloud TGU 645 in which NGC 7129 is embedded. NGC 7023 is a reflection nebula, illuminated by the young massive star HD 200775 and several less luminus stars. It was discovered in 1794 by William Her- schel. HD 200775 is a Herbig Be star (also known as V380 Cep and HBC 726) which was studied by Slipher (1918), Altamore et al. (1980), Witt & Cottrel (1980), Witt et al. (1982), Rogers et al. (1995), Laureijs et al. (1996), Fuente et al. (2000), Werner et al. (2004), Pogodin et al. (2004), Alecian et al. (2008), Berne et al. (2008). In the center of the reflection nebula, Weston (1953) found a small group of variable stars, show Hα line in emission. Approximately two dozens of variable stars in the region were studied by Rosino & Romano (1962). Goodman & Arce (2004) spec- ulate that the young Herbig Ae star PV Cep, located more than 10 pc to the west of the cluster, might have been ejected from NGC 7023 at least 100,000 years ago. HD 200775 is located at the northern edge of an elongated molecular cloud, corre- sponding to the dark clouds L1167, 1168, 1170, 1171, 1172, 1173 and 1174, most frequently known as L1167/L1174 complex. The cloud complex has been mapped 9 Figure 0.1.: Distribution of pre-main sequence stars in the Cepheus Flare region, taken from Kun et al. (2008), overplotted on the extinction map from the Dobashi et al. (2005). Red dots and black crosses indicate the classical T Tauri stars. Blue star symbols show Herbig Ae/Be stars and green diamonds denote T Tauri stars identified by Tachihara et al. (2005). Three black squares on the right side show the areas investigated in this work. The size of the squares is approximately the same as that of the fields observed with the Maksutov telescope. in CO by Elmegreen & Elmegreen (1978). They determined the size of the cloud 0.5◦ × 1.0◦ , or 3.9 pc × 7.7 pc, and the mass of the molecular hydrogen about 600 M⊙. Close to the star HD 200775, Watt et al. (1986) found a bipolar outflow. The area of the outflow has been mapped by Fuente et al. (1998) according to CO molecular line emission, but they found no evidence for current high-velocity gas. Another molecular outflow, centered on the IRAS source IRAS 21017+6742 was found by Myers et al. (1988). On the K filter image of L1172, Hodapp (1994) found four stars associated with localized nebulosity. Visser, Richter & Chandler (2002) detected three submillimeter sources at the position of IRAS 21017+6742 and L1172 SMM1–SMM3 claiming that there could be a protostar as a source of the outflow. Dark cloud TGU619 (Dobashi et al. 2005), corresponding to the Lynds (1962) 10 clouds LDN 1147,