期刊
ASTRONOMY & ASTROPHYSICS
卷 499, 期 1, 页码 121-128出版社
EDP SCIENCES S A
DOI: 10.1051/0004-6361/200810830
关键词
galaxies: individual: Tucana dwarf; galaxies: structure; galaxies: kinematics and dynamics; galaxies: stellar content
资金
- STFC [ST/H004157/1, PP/C002229/1, ST/F001967/1, ST/H004165/1] Funding Source: UKRI
- Science and Technology Facilities Council [ST/H004165/1, ST/H004157/1, PP/C002229/1, ST/F001967/1] Funding Source: researchfish
Aims. Dwarf spheroidal galaxies in the Local Group are usually located close to the Milky Way or M31. Currently, there are two clear exceptions to this rule, and the Tucana dwarf galaxy is the most distant at almost 1 Mpc from the Milky Way. Our aim is to learn more about the nature of Tucana by measuring its radial velocity and internal kinematics. Methods. Using the VLT/FORS2 spectrograph in multi-object mode we were able to measure the velocities of 23 individual red giant branch stars in and around Tucana using the Ca II triplet absorption lines. From this sample 17 reliable members have been identified. Results. We measured the systemic velocity and dispersion of Tucana to be upsilon(hel) = +194.0 +/- 4.3 km s(-1) and sigma(l.o.s) = 15.8(-3.1)(+4.1) km s(-1), respectively. These measures are obtained after removing the signature of rotation using a linear gradient of 6.5 x R/R-core +/- 2.9 km s(-1) which corresponds to a rotation of approximate to 16 km s(-1) at the reliable limit of our data. Our systemic velocity corresponds to a receding velocity from the barycentre of the Local Group of upsilon(LG) = +73.3 kms(-1). We also determined the mean metallicity of Tucana to be [Fe/H] = -19.5 +/- 0.15 with a dispersion of 0.32 +/- 0.06 dex. Conclusions. Our study firmly excludes any obvious association of Tucana with the HI emission in the vicinity and shows that Tucana is a genuine dwarf spheroidal with low metallicity stars, no gaseous ISM and no recent star formation. The present location and relatively high recession velocity are consistent with Tucana having been an isolated Local Group galaxy for the majority of its existence.
作者
我是这篇论文的作者
点击您的名字以认领此论文并将其添加到您的个人资料中。
推荐
暂无数据