Shedding light on the formation mechanism of shell galaxy NGC 474 with MUSE
Shedding light on the formation mechanism of shell galaxy NGC 474 with MUSE
复制标题
利用 MUSE 揭示壳星系 NGC 474 的形成机制
DOI：
10.1051/0004-6361/202038550
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发表时间：
2020-12
影响因子：
6.5
通讯作者：
Smith Rory
中科院分区：
文献类型：
--
作者：
Fensch Jeremy;Duc Pierre-Alain;Lim Sungsoon;Emsellem Eric;Bilek Michal;Durrell Patrick;Liu Chengze;Peng Eric;Smith Rory
星系周围的恒星壳可以提供对其组装历史的宝贵见解。然而，它们的形成机制仍然缺乏经验约束，特别是关于它们起源时的星系碰撞类型。我们目前的MUSE在VLT数据的最突出的外壳的NGC 474，以约束其形成历史。恒星壳光谱被清晰地探测到，信噪比为1.65 pix−1。我们使用了全光谱拟合方法来确定视线速度和年龄和金属的外壳和相关的点状源在MUSE的视野。我们检测到六个球状星团（GC）的候选者和八个行星状星云（PN）的候选者，都与恒星壳运动学相关。我们发现壳层具有中等的金属丰度，[M/H] = −0.83−0.12+0.12，以及可能的α-富集，[α/Fe]<$0.3。假设壳层的物质来自一个质量较低的伴星，并且后者没有初始金属丰度梯度，这样的恒星金属丰度将把前身星的质量限制在7.4 × 108 M左右，这意味着合并的质量比约为1：100。 然而，我们对PNe的普查和早期的外壳测光表明，比例要高得多，大约为1：20。考虑到不确定性，该差异仅在101 σ水平下显著。我们讨论了祖先的特点，特别是祖先是否也可以从一个更大的星系的低金属丰度郊区的恒星组成。最终，所提供的数据不允许我们对祖细胞质量进行严格限制。我们发现，至少有两个GC候选人可能与壳是相当年轻的，年龄低于1.5 Gyr。我们还注意到NGC 474中心存在一个年轻（101 Gyr）恒星群。两者可能是同一事件的结果。
Stellar shells around galaxies could provide precious insights into their assembly history. However, their formation mechanism remains poorly empirically constrained, regarding in particular the type of galaxy collisions at their origin. We present MUSE at VLT data of the most prominent outer shell of NGC 474, to constrain its formation history. The stellar shell spectrum is clearly detected, with a signal-to-noise ratio of ∼65 pix−1. We used a full spectral fitting method to determine the line-of-sight velocity and the age and metallicity of the shell and associated point-like sources within the MUSE field of view. We detect six globular cluster (GC) candidates and eight planetary nebula (PN) candidates that are all kinematically associated with the stellar shell. We show that the shell has an intermediate metallicity, [M/H] = −0.83−0.12+0.12, and a possible α-enrichment, [α/Fe] ∼ 0.3. Assuming the material of the shell comes from a lower mass companion, and that the latter had no initial metallicity gradient, such a stellar metallicity would constrain the mass of the progenitor at around 7.4 × 108 M⊙, implying a merger mass ratio of about 1:100. However, our census of PNe and earlier photometry of the shell would suggest a much higher ratio, around 1:20. Given the uncertainties, this difference is only significant at the ≃1σ level. We discuss the characteristics of the progenitor, and in particular whether the progenitor could also be composed of stars from the low-metallicity outskirts of a more massive galaxy. Ultimately, the presented data do not allow us to put a firm constraint on the progenitor mass. We show that at least two GC candidates possibly associated with the shell are quite young, with ages below 1.5 Gyr. We also note the presence of a young (∼1 Gyr) stellar population in the center of NGC 474. The two may have resulted from the same event.
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影响因子：
6.5
作者：
A. Longobardi;M. Arnaboldi;O. Gerhard;J. C. Mihos
通讯作者：
A. Longobardi;M. Arnaboldi;O. Gerhard;J. C. Mihos
DOI：
10.1111/j.1365-2966.2007.11759.x
发表时间：
2007-03
影响因子：
4.8
作者：
F. Combes;L. M. Young;L. M. Young;M. Bureau
通讯作者：
F. Combes;L. M. Young;L. M. Young;M. Bureau
DOI：
10.1111/j.1365-2966.2006.10179.x
发表时间：
2006-05
影响因子：
4.8
作者：
R. Rampazzo;P. Alexander;C. Carignan;M. Clemens;H. Cullen;O. Garrido;M. Marcelin;K. Sheth;G. Trinchieri
通讯作者：
R. Rampazzo;P. Alexander;C. Carignan;M. Clemens;H. Cullen;O. Garrido;M. Marcelin;K. Sheth;G. Trinchieri
DOI：
10.1111/j.1365-2966.2012.21877.x
发表时间：
2012-08
影响因子：
4.8
作者：
D. Forbes;A. Cortesi;V. Pota;C. Foster;A. Romanowsky;M. Merrifield;J. Brodie;J. Strader;L. Coccato;N. Napolitano
通讯作者：
D. Forbes;A. Cortesi;V. Pota;C. Foster;A. Romanowsky;M. Merrifield;J. Brodie;J. Strader;L. Coccato;N. Napolitano
DOI：
10.3847/1538-4365/aabfdf
发表时间：
2018-04
期刊：
The Astrophysical Journal Supplement Series
影响因子：
--
作者：
C. Willmer
通讯作者：
C. Willmer