论文标题
阿尔玛（Alma
ALMA detection of the dusty object silhouetted against the S0 galaxy NGC 3269 in the Antlia cluster
论文作者
论文摘要
在光学图像中，在Antlia簇中的S0 Galaxy NGC 3269的磁盘上可以看到一个有趣的小尘斑块。这些图像没有提供任何线索，即该贴片是局部木星质量尺度的云或大型尘埃尘埃复合物。我们旨在解决该物体的性质：它是小银河系或乳层尘埃络合物吗？ Alma和Apex光谱和Gemini GMOS长距离光谱法用于测量斑块的速度和NGC 3269磁盘径向速度曲线。弱16 $ \ pm $ 2.5 km/s宽$^{12} $ co（2-1）t $ _ {MB} $ 19 $ \ pm $ 2.5 mk $ 2.5 mk $ 2.0英寸“ 2.0” x 2.12”梁与对象相关的光束与Alma检测到。观察到的HeliePentric速度，V $ _R $，HEL = 3878 $ \ pm $ 5.00km/s，立即确定对象的外层面性质。贴片速度与NGC 3269核的速度一致，但与Galaxy位置的NGC 3269磁盘的径向速度不一致。 $ \ sim $ 4“贴片的角度尺寸对应于银河系的线性尺寸为$ \ sim $ 1 kpc，在银河的哈勃距离为（d/50.7 mpc）$^2 $ msun，而衰减来自光谱，则意味着尘埃质量为$ \ sim $ \ sim $ \ sim $ \ sim $ 2.6x10 $^4 $^4 $^$^2/50.7 mpc） $ _ b $/（a $ _ b $ -a'$ _ r $）为1.6 $ \ $ $ 0.11比平均银河系灭绝曲线的相应值低于点源（2.3），我们确定了贴片的外部范围。及其邻居NGC 3268。
An intriguing silhouette of a small dust patch can be seen against the disk of the S0 galaxy NGC 3269 in the Antlia cluster in optical images. The images do not provide any clue as to whether the patch is a local Jupiter mass-scale cloudlet or a large extragalactic dust complex. We aim to resolve the nature of this object: is it a small Galactic cloudlet or an extragalactic dust complex? ALMA and APEX spectroscopy and Gemini GMOS long-slit spectroscopy were used to measure the velocity of the patch and the NGC 3269 disk radial velocity curve. A weak 16$\pm$2.5 km/s wide $^{12}$CO (2-1) T$_{MB}$ 19$\pm$2.5 mK line in a 2.0" by 2.12" beam associated with the object was detected with ALMA. The observed heliocentric velocity, V$_r$,hel = 3878$\pm$5.0km/s, immediately establishes the extragalactic nature of the object. The patch velocity is consistent with the velocity of the nucleus of NGC 3269, but not with the radial velocity of the NGC 3269 disk of the galaxy at its position. The $\sim$4" angular size of the patch corresponds to a linear size of $\sim$1 kpc at the galaxy's Hubble distance of (d/50.7 Mpc)$^2$ Msun, while the attenuation derived from the optical spectrum implies a dust mass of $\sim$2.6x10$^4$ (d/50.7 Mpc)$^2$ Msun. The derived attenuation ratio A'$_B$/(A'$_B$-A'$_R$) of 1.6$\pm$0.11 is substantially lower than the corresponding value for the mean Milky Way extinction curve for point sources (2.3). We established the extragalactic nature of the patch, but its origin remains elusive. One possibility is that the dust patch is left over from the removal of interstellar matter in NGC 3269 through the interaction with its neighbour, NGC 3268.
