Halo mass and assembly history exposed in the faint outskirts: the stellar and dark matter haloes of Illustris galaxies
Halo mass and assembly history exposed in the faint outskirts: the stellar and dark matter haloes of Illustris galaxies
复制标题
DOI：
10.1093/mnras/stu1408
复制
发表时间：
2014-06
影响因子：
4.8
通讯作者：
A. Pillepich;M. Vogelsberger;A. Deason;V. Rodriguez-Gomez;S. Genel;D. Nelson;P. Torrey;L. Sales;F. Marinacci;V. Springel;D. Sijacki;L. Hernquist
中科院分区：
文献类型：
--
作者：
A. Pillepich;M. Vogelsberger;A. Deason;V. Rodriguez-Gomez;S. Genel;D. Nelson;P. Torrey;L. Sales;F. Marinacci;V. Springel;D. Sijacki;L. Hernquist
我们使用 Illustris 模拟来深入了解围绕星系的外部低表面亮度区域的形成。我们通过球面平均恒星密度分布的对数斜率（z=0 处的 alphaSTARS）来表征恒星晕，并将这些斜率与底层暗物质（DM）晕的特性、它们的中心星系及其组装历史联系起来。我们分析了约 5,000 个星系的样本，每个星系由超过 5x10^4 的粒子解析，涵盖各种形态和晕质量（3x10^11 < Mvir < 10^14 Msun）。我们发现恒星晕斜率和晕总质量之间存在很强的趋势，其中质量较大的天体比质量较小的天体具有更浅的恒星晕（在研究的质量范围内 -5.5 \pm 0.5 < alphaSTARS <-3.5 \pm 0.2）。在固定晕质量下，我们发现盘状、蓝色、年轻和质量较大的星系比椭圆形、红色、较老和质量较小的星系被更陡的恒星晕包围。总体而言，恒星密度剖面比底层DM 下降得更陡，并且恒星斜率和DM 晕浓度之间没有明显的趋势。然而，最近形成的 DM 晕，或者从坠落卫星中吸积了较大部分恒星质量的 DM 晕，表现出比具有相似质量的较旧类似物更浅的恒星晕，达 Delta(alphaSTARS) ~ 0.5-0.7。我们的发现，结合对 M31 和银河系截然不同的恒星幂律指数的最新测量结果，似乎有利于 M31 的巨大质量，以及过去 10 吉里的吸积历史比其伴星安静得多的银河系。
We use the Illustris Simulations to gain insight into the build-up of the outer, low-surface brightness regions which surround galaxies. We characterize the stellar haloes by means of the logarithmic slope of the spherically-averaged stellar density profiles, alphaSTARS at z=0, and we relate these slopes to the properties of the underlying Dark-Matter (DM) haloes, their central galaxies, and their assembly histories. We analyze a sample of ~5,000 galaxies resolved with more than 5x10^4 particles each, and spanning a variety of morphologies and halo masses (3x10^11 < Mvir < 10^14 Msun). We find a strong trend between stellar halo slope and total halo mass, where more massive objects have shallower stellar haloes than the less massive ones (-5.5 \pm 0.5 < alphaSTARS <-3.5 \pm 0.2 in the studied mass range). At fixed halo mass, we show that disk-like, blue, young, and more massive galaxies are surrounded by significantly steeper stellar haloes than elliptical, red, older, and less massive galaxies. Overall, the stellar density profiles fall off much more steeply than the underlying DM, and no clear trend holds between stellar slope and DM halo concentration. However, DM haloes which formed more recently, or which accreted larger fractions of stellar mass from infalling satellites, exhibit shallower stellar haloes than their older analogs with similar masses, by up to Delta(alphaSTARS) ~ 0.5-0.7. Our findings, combined with the most recent measurements of the strikingly different stellar power-law indexes for M31 and the Milky Way, appear to favour a massive M31, and a Milky Way characterized by a much quieter accretion history over the past 10 Gyrs than its companion.