文章基本信息

标题：Reddening map and recent star formation in the Magellanic Clouds based on OGLE IV Cepheids ⋆
本地全文：下载
作者：Y. C. Joshi ; A. Panchal
期刊名称：Astronomy & Astrophysics
印刷版ISSN：0004-6361
电子版ISSN：1432-0746
出版年度：2019
卷号：628
页码：1-16
DOI：10.1051/0004-6361/201834574
语种：English
出版社：EDP Sciences
摘要：Context.The reddening maps of the Large Magellanic Cloud (LMC) and Small Magellanic Cloud (SMC) are constructed using the Cepheid period–luminosity (P–L) relations.Aims.We examine reddening distribution across the LMC and SMC through large data sets on classical Cepheids provided by the OGLE Phase IV survey. We also investigate the age and spatio-temporal distributions of Cepheids to understand the recent star formation history in the LMC and SMC.Methods.TheVandIband photometric data of 2476 fundamental mode (FU) and 1775 first overtone mode (FO) Cepheids in the LMC, and 2753 FU and 1793 FO Cepheids in the SMC were analysed for theirP–Lrelations. We converted the period of FO Cepheids to the corresponding period of FU Cepheids before combining the two modes of Cepheids. Both galaxies were divided into small segments and combined FU and FOP–Ldiagrams were drawn in two bands for each segment. The reddening analysis was performed on 133 segments covering a total area of about 154.6 deg2in the LMC and 136 segments covering a total area of about 31.3 deg2in the SMC. By comparison with well-calibratedP–Lrelations of these two galaxies, we determined reddeningE(V − I) in each segment and equivalent reddeningE(B − V) assuming the normal extinction law. The period–age relations were used to derive the age of the Cepheids.Results.Reddening maps were constructed using reddening values in different segments across the LMC and SMC. We find clumpy structures in the reddening distributions of the LMC and SMC. From the reddening map of the LMC, highest reddening ofE(V − I) = 0.466 mag is traced in the region centred atα∼ 85.°13,δ∼ −69.°34 which is in close vicinity of the star forming HII region 30 Doradus. In the SMC, maximum reddening ofE(V − I) = 0.189 mag is detected in the region centred atα∼ 12.°10,δ∼ −73.°07. The mean reddening values in the LMC and SMC are estimated asE(V − I)LMC = 0.113 ± 0.060 mag,E(B − V)LMC = 0.091 ± 0.050 mag,E(V − I)SMC = 0.049 ± 0.070 mag, andE(B − V)SMC = 0.038 ± 0.053 mag.Conclusions.The LMC reddening map displays heterogeneous distribution having small reddening in the central region and higher reddening towards the eastern side of the LMC bar. The SMC has relatively small reddening in its peripheral regions but larger reddening towards the south-west region. In these galaxies, we see evidence of a common enhanced Cepheid population at around 200 Myr ago which appears to have occurred due to a close encounter between the two clouds.
关键词：enmethods: data analysissurveysstars: variables: CepheidsMagellanic Cloudsgalaxies: star formation