VLT/VIMOS observations of an occulting galaxy pair: redshifts and effective extinction curve
VLT/VIMOS observations of an occulting galaxy pair: redshifts and effective extinction curve
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VLT/VIMOS 对隐匿星系对的观测：红移和有效消光曲线
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发表时间：
2013
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影响因子：
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通讯作者：
R. D. Jong
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作者：
B. Holwerda;T. Böker;J. Dalcanton;W. Keel;R. D. Jong
我们介绍了之前在HST观测中发现的一对掩星星系的VLT/VIMOS IFU观测。前景星系是一个低倾角的螺旋盘，在背景星系的明亮凸起和盘的映衬下，产生了明显的衰减特征。我们发现前景星系和背景星系的红移分别为z=0.065：0640和0：003。这一相对较小的差异并不排除两个星系之间存在引力相互作用。发射线比率表明这是一个恒星形成的星系，而不是以活动星系核为主的前景星系。我们将Cardelli，Clayton&Mathis(CCM)消光定律应用于单个Bre的光谱，得到斜率(RV)和归一化(Av)。归一化与HST衰减图一致，斜率低于银河系关系(RV<；3：1)，这可能与盘的空间采样有关。我们推测，RV的值要么指向盘中的相干ISM结构，要么比平时(9KPC)更大，或者RV的起始值更高，表明最近尘埃的处理。前景星系是一个低质量旋涡星系(M3109M)，尘埃含量高(Must 0：5106M)。HST图像中可见的尘埃盘几何形状可以解释观测到的较小星系的SED特性：较低的平均尘埃温度，较高的尘埃与恒星质量比，但光学衰减相对较小。对前景较小的星系的掩星对进行的观测将表明这种几何学是多么普遍。
We present VLT/VIMOS IFU observations of an occulting galaxy pair previously discovered in HST observations. The foreground galaxy is a low-inclination spiral disk, which causes clear attenuation features seen agains the bright bulge and disk of the background galaxy. We nd redshifts of z = 0:064 0:003 and z=0.065 for the foreground and background galaxy respectively. This relatively small dierence does not rule out gravitational interaction between the two galaxies. Emission line ratios point to a star-forming, not AGN-dominated foreground galaxy. We t the Cardelli, Clayton & Mathis (CCM) extinction law to the spectra of individual bres to derive slope ( RV ) and normalization (AV ). The normalization agrees with the HST attenuation map and the slope is lower than the Milky Way relation (RV < 3:1), which is likely linked to the spatial sampling of the disk. We speculate that the values of RV point to either coherent ISM structures in the disk larger than usual ( 9 kpc) or higher starting values of RV , indicative of recent processing of the dust. The foreground galaxy is a low stellar mass spiral (M 3 10 9 M ) with a high dust content (Mdust 0:5 10 6 M ). The dust disk geometry visible in the HST image would explain the observed SED properties of smaller galaxies: a lower mean dust temperature, a high dust-to-stellar mass ratio but relatively little optical attenuation. Ongoing eorts to nd occulting pairs with a small foreground galaxies will show how common this geometry is.