论文标题
表征与Gaia DR2的低对比度银河开放群集
Characterizing low contrast Galactic open clusters with GAIA DR2
论文作者
论文摘要
在这项研究中，我们表征了16个先前被归类为微弱或低对比的式露天簇（OC）的对象。我们采用了与OCS动力学相关的参数：核心（$ r_c $），潮汐（$ r_t $）和半质量（$ r_ {hm} $）RADII，年龄和交叉时间（$ t_ {cr {cr} $）。这些参数之间的关系被利用以提出一些进化连接。我们还包括11个具有先前特征的OC，以提供更广泛的参数空间覆盖范围。研究的样品跨越了相当大的年龄范围（log（t/yr）〜7.0-9.7）和半乳缘距离（$ r_g $ 〜6-11 kpc）。他们中的大多数都有太阳金属性。我们采用了GAIA DR2天文学和光度法以及选定的成员恒星，通过探索3D星形空间（$μ_α$，$μ_δ$，$ \ varpi $）来分配会员可能性。以前对这些对象大多数的研究主要基于光度信息。所有研究的OC被证明是真正的恒星浓度及其参数之间的关系，表明一种普遍的破坏情况，其中OC随着演变而倾向于更加集中。内部相互作用吸引了OC，以开发更动态放松的结构，并使由于潮汐效应而遭受质量损失。根据银河潮汐场的强度，潮汐半径往往会随着$ r_g $而增加。此外，$ r_c $与动态比率$τ_ {\ textrm {dyn}} $ = age/$ t_ {cr} $之间的相关性暗示了两个不同的进化序列，这可能是不同初始形成条件的结果。
In this study, we characterized 16 objects previously classified as faint or low contrast Galactic open clusters (OCs). We employed parameters associated to the OCs dynamical evolution: core ($r_c$), tidal ($r_t$) and half-mass ($r_{hm}$) radii, age and crossing time ($t_{cr}$). Relations among these parameters were exploited to draw some evolutionary connections. We also included 11 OCs with previous characterizations to provide wider coverage of the parameters space. The investigated sample spans a considerable range in age (log (t/yr) ~7.0 - 9.7) and Galactocentric distance ($R_G$ ~ 6 - 11 kpc). Most of them present solar metallicity. We employed GAIA DR2 astrometry and photometry and selected member stars through a decontamination algorithm which explores the 3D astrometric space ($μ_α$, $μ_δ$, $\varpi$) to assign membership likelihoods. Previous studies of most of these objects were based mostly on photometric information. All investigated OCs were proved to be real stellar concentrations and relations among their parameters indicate a general disruption scenario in which OCs tend to be more concentrated as they evolve. Internal interactions sucessively drive OCs to develop more dynamically relaxed structures and make them less subject to mass loss due to tidal effects. Tidal radius tends to increase with $R_G$ in accordance with the strength of the Galactic tidal field. Besides, the correlation between the $r_c$ and the dynamical ratio $τ_{\textrm{dyn}}$ = age/$t_{cr}$ suggests two distinct evolutionary sequences, which may be consequence of different initial formation conditions.
