EVIDENCE FOR A MASSIVE, EXTENDED CIRCUMGALACTIC MEDIUM AROUND THE ANDROMEDA GALAXY
EVIDENCE FOR A MASSIVE, EXTENDED CIRCUMGALACTIC MEDIUM AROUND THE ANDROMEDA GALAXY
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仙女座星系周围存在巨大、延伸的环绕星系介质的证据
DOI：
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发表时间：
2014
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影响因子：
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通讯作者：
B. Wakker
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作者：
N. Lehner;C. Howk;B. Wakker
我们利用HST宇宙起源光谱仪对M31的两个维里半径（R维里= 300 ?）内18个qso的紫外光谱，证明了M31周围存在一个扩展的大质量环星系介质（CGM）。> kpc)。我们探测到Si iii在- 300≤v处的吸收，LSR≤- 150 ？在R > 0.2 R vir ？在0.8 > R / R < 1.1 ？在1.1 < R / R vir > 1.8 ？>。我们提出了几个论点，在这些方向上观察到的这些速度的气体来自M31 CGM，而不是本星系群或银河系CGM或麦哲伦流。我们表明，位于M31的CGM中的矮星系在与M31相似的投影距离上具有非常相似的速度。我们发现，只有在这些速度下，所有离子的列密度(N)与R之间才存在一种非平凡的关系，即N随着R的增加而减小。>， Si iii和civ的覆盖分数接近统一(f C ~ 60% ？> -97%（90%置信水平），但下降到f c > 10% ？> -20%在R≤R ？>。我们发现M31 CGM气体是结合的，多相的，主要是电离的，并且在较大的r下是高度电离的气体。我们使用Si ii， Si iii和Si iv估计CGM金属质量为约2 × 10 ？b> m☉？>和气体质量> 3 × 10 9 (Z☉/ Z) ？b> m☉？>在0.2 R内？>，在R - vir ?内可能大10倍。>，暗示在M31的CGM中有大量的金属和气体。
We demonstrate the presence of an extended and massive circumgalactic medium (CGM) around Messier 31 using archival HST Cosmic Origins Spectrograph ultraviolet spectroscopy of 18 QSOs projected within two virial radii of M31 ( R vir = 300 ?> kpc). We detect absorption from Si iii at − 300 ≲ v LSR ≲ − 150 ?> km s−1 toward all three sightlines at R ≲ 0.2 R vir ?> , 3 of 4 sightlines at 0.8 ≲ R / R vir ≲ 1.1 ?> , and possibly 1 of 11 at 1.1 < R / R vir ≲ 1.8 ?> . We present several arguments that the gas at these velocities observed in these directions originates from the M31 CGM rather than the Local Group or Milky Way CGM or Magellanic Stream. We show that the dwarf galaxies located in the CGM of M31 have very similar velocities over similar projected distances from M31. We find a non-trivial relationship only at these velocities between the column densities (N) of all the ions and R, whereby N decreases with increasing R. At R < 0.8 R vir ?> , the covering fraction is close to unity for Si iii and C iv ( f c ∼ 60 % ?> –97% at the 90% confidence level), but drops to f c ≲ 10 % ?> –20% at R ≳ R vir ?> . We show that the M31 CGM gas is bound, multiphase, predominantly ionized, and is more highly ionized gas at larger R. We estimate using Si ii, Si iii, and Si iv, a CGM metal mass of ≳ 2 × 10 6 ?> M ☉ ?> and gas mass of ≳ 3 × 10 9 ( Z ☉ / Z ) ?> M ☉ ?> within 0.2 R vir ?> , and possibly a factor of ∼10 larger within R vir ?> , implying substantial metal and gas masses in the CGM of M31.