A multibeam H i survey of the Virgo cluster – two isolated H i clouds?
A multibeam H i survey of the Virgo cluster – two isolated H i clouds?
复制标题
对室女座星团的多波束 H i 调查——两个孤立的 H i 云？
DOI：
10.1111/j.1365-2966.2004.07568.x
复制
发表时间：
2003
影响因子：
4.8
通讯作者：
R. Smith
中科院分区：
文献类型：
--
作者：
J. Davies;Robert. F. Minchin;S. Sabatini;W. Driel;M. Baes;P. Boyce;W. D. Blok;M. Disney;R. Evans;V. Kilborn;R. Lang;S. Linder;S. Roberts;R. Smith
我们使用Jodrell Bank多波束仪器对处女座星系团的部分区域进行了全采样的大范围(4°x 8°)21厘米高线测量。这项调查的灵敏度比标准的HIJASS(Hi Jodrell All Sky Survey)和HIPASS(HI Parkes All Sky Survey)高出约三倍。我们探测到31个星系，其中27个是众所周知的星系团成员。HIPASS的数据和Jodrell Bank的后续观察证实了这四个新的检测结果。一个物体位于M86后面，但另外三个物体在数字天空勘测场的检查中没有明显的光学对应物。这三个天体是在阿雷西博绘制的，其半功率束宽(HPBW)小于3.6弧度，灵敏度是Jodrell Bank数据的四倍，后者可以更好地确定其中两个天体的尺寸和位置，但令人惊讶的是未能检测到第三个。这两个天体由阿雷西博光束分辨，使它们的大小远远大于附近视野中的任何光学图像。到我们的质量极限5×107(Δυ/50公里S-1)M 0。柱密度极限为3×1018(Δυ/50 km S-1)原子厘米-2，这些新的探测只占团簇原子氢质量的2%左右。我们的观测表明，星系团的HI质量函数在低质量端向下移动，这使得它与场星系的HI质量函数有很大的不同。这与Virgo团簇的光学光度函数有很大的不同，后者比一般场中的光度函数陡峭得多。与H I选定的野外星系样本相比，许多样本星系的气体相对贫乏，这证实了处女座星系团晚类型星系的“贫血症螺旋”观点。HI探测到的星系的速度分布也与整个星系团的速度分布有很大的不同。在H I样本中有相对较多的高速星系，这表明它们构成了目前正在流入的星系群的一部分。具有光学识别的HI样本的最小HI柱密度截止值比调查灵敏度预期的高出一个数量级。观测到的柱状密度高于恒星形成的正常预期水平。没有光学对应物的两个探测器的柱子密度比样本的其余部分低得多，低于恒星形成阈值。
We have carried out a fully sampled large area (4° x 8°) 21-cm Hi line survey of part of the Virgo cluster using the Jodrell Bank multibeam instrument. The survey has a sensitivity some three times better than the standard HIJASS (Hi Jodrell All Sky Survey) and HIPASS (HI Parkes All Sky Survey) surveys. We detect 31 galaxies, 27 of which are well-known cluster members. The four new detections have been confirmed in the HIPASS data and by follow-up Jodrell Bank pointed observations. One object lies behind M86, but the other three have no obvious optical counterparts upon inspection of the digital sky survey fields. These three objects were mapped at Arecibo with a smaller 3.6-arcmin half power beam width (HPBW) and a four times better sensitivity than the Jodrell Bank data, which allow an improved determination of the dimensions and location of two of the objects, but surprisingly failed to detect the third. The two objects are resolved by the Arecibo beam, giving them a size far larger than any optical images in the nearby field. To our mass limit of 5 x 10 7 (Δυ/50 km s -1 ) M ○. and column density limit of 3 × 10 18 (Δυ/50 km s -1 ) atom cm -2 , these new detections represent only about 2 per cent of the cluster atomic hydrogen mass. Our observations indicate that the HI mass function of the cluster turns down at the low-mass end, making it very different to the field galaxy HI mass function. This is quite different to the Virgo cluster optical luminosity function, which is much steeper than that in the general field. Many of the sample galaxies are relatively gas-poor compared with H I selected samples of field galaxies, confirming the 'anaemic spirals' view of Virgo cluster late-type galaxies. The velocity distribution of the HI detected galaxies is also very different to that of the cluster as a whole. There are relatively more high-velocity galaxies in the H I sample, suggesting that they form part of a currently infalling population. The HI sample with optical identifications has a minimum HI column density cut-off more than an order of magnitude above that expected from the sensitivity of the survey. This observed column density is above the normally expected level for star formation to occur. The two detections with no optical counterparts have very much lower column densities than that of the rest of the sample, below the star formation threshold.