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A tidally distorted dwarf galaxy near NGC 4449

机译:NGC 4449附近的一个畸变的矮星系

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摘要

NGC 4449 is a nearby Magellanic irregular starburst galaxy with a B-band absolute magnitude of -18 and a prominent, massive, intermediate-age nucleus at a distance from Earth of 3.8 mega-parsecs (ref. 3). It is wreathed in an extraordinary neutral hydrogen (H I) complex, which includes rings, shells and a counter-rotating core, spanning ~90 kiloparsecs (kpc; refs 1,4). NGC 4449 is relatively isolated, although an interaction with its nearest known companion-the galaxy DDO 125, some 40 kpc to the south-has been proposed as being responsible for the complexity of its HI structure. Here we report the presence of a dwarf galaxy companion to NGC 4449, namely NGC 4449B. This companion has a V-band absolute magnitude of -13.4 and a half-light radius of 2.7 kpc, with a full extent of around 8 kpc. It is in a transient stage of tidal disruption, similar to that of the Sagittarius dwarf near the Milky Way. NGC 4449B exhibits a striking S-shaped morphology that has been predicted for disrupting galaxies but has hitherto been seen only in a dissolving globular cluster. We also detect an additional arc or disk ripple embedded in a two-component stellar halo, including a component extending twice as far as previously known, to about 20 kpc from the galaxy's centre.
机译:NGC 4449是附近的麦哲伦不规则星爆星系,其B波段绝对大小为-18,并且在距地球3.8兆帕的距离上有一个显着的块状中年核(参考文献3)。它缠绕在一个非同寻常的中性氢(H I)络合物中,该络合物包括环,壳和反向旋转的核,跨度约90千帕秒(kpc;参考文献1,4)。 NGC 4449是相对孤立的,尽管有人提出与其南星40 kpc的星系DDO 125相互作用,这是造成其HI结构复杂的原因。在这里,我们报告了NGC 4449矮星系伴星的存在,即NGC 4449B。该伴星的V波段绝对幅度为-13.4,半光线半径为2.7 kpc,全范围约为8 kpc。它处于潮汐破坏的过渡阶段,类似于银河系附近的射手座矮人。 NGC 4449B表现出惊人的S形形态,已被预测会破坏星系,但迄今为止仅在溶解的球状星团中才能看到。我们还检测到嵌在由两部分组成的恒星晕中的附加电弧或磁盘波纹,其中包括从银河系中心延伸到以前已知距离的两倍,达到大约20 kpc。

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  • 来源
    《Nature》 |2012年第7384期|p.192-194|共3页
  • 作者单位

    Departmentof Physics and Astronomy, 430 Portola Plaza, Box 951547, University of California, Los Angeles, California 90095-1547, USA,Polaris Observatory Association, Frazier Park, California 93225, USA;

    Max-Planck-Institut fuer Astronomie, Koenigstuhl 17, Heidelberg D-69117, Germany;

    Departmentof Physics and Astronomy, 430 Portola Plaza, Box 951547, University of California, Los Angeles, California 90095-1547, USA;

    Polaris Observatory Association, Frazier Park, California 93225, USA,UCLA Anderson School of Management, 110 Westwood Plaza, Los Angeles, California 90095-1481, USA;

    Zentrum fuerAstronomiederUniversitat Heidelberg, Landesstemwarte, Koenigstuhl 12,69117 D-Heidelberg, Germany;

    Department of Astronomy, California Institute of Technology, MC 249-1,1200 East California Boulevard, Pasadena, California 91125, USA;

    Departmentof Physics and Astronomy, 430 Portola Plaza, Box 951547, University of California, Los Angeles, California 90095-1547, USA,Griffith Observatory, 2800 East Observatory Road, Los Angeles, California 90027, USA;

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