arXiv 1104.05072011-04-04astro-ph.CO

阿雷西博星系环境巡天IV：NGC7448区域和HI质量函数

The Arecibo Galaxy Environments survey IV: the NGC7448 region and the HI mass function

J. I. Davies, R. Auld, L. Burns, R. Minchin, E. Momjian, S. Schneider, M. Smith, R. Taylor, W. van Driel

摘要：

在本文中，我们描述了从阿雷西博星系环境调查（AGES）的结果。在10平方度量级的单个区域内，观测得到的柱密度约为3 × 10^18 cm^-2，质量约为10^7 M_O，最大速度为18，000 km·s^-1。每个被调查的区域都以附近的星系、星系群或星系团为中心，在这个例子中是NGC 7448星系群。NGC 7448星系群中的星系相互作用通过潮汐尾和潮汐桥的识别来揭示。我们发现星系间介质中的原子气体比星系团中的原子气体多2.5倍。我们确定了五个新的矮星系，其中两个似乎是NGC 7448组的成员。这是太少了，大约一个数量级，矮星系协调观测与理论预测的星系形成模型。如果他们观察到了这个天空区域，那么之前的广域盲HI调查，HIPASS和ALPRAFA，将分别只检测到我们检测到的星系的5%和43%，错过了这个体积中的大部分原子气体。我们将本文的数据与AGES的其他论文（370个星系）的数据结合起来，导出了具有以下Schechter函数参数的HI质量函数：α =-1.52+/-0.05，M^*=5.1+/-0.3x10^9 h_72^-2 M_O，phi=8.6+/-1.1x10 - 3 h_72^3 Mpc^-3 dex-1。对质量函数进行积分，得到氢原子的宇宙质量密度为Omega_HI=5.3+/-0.8x10 ^-4 h_72^-1。我们的质量函数比HIPASS和ALOFA发现的都要陡峭（α分别为1.37和1.33），而我们的宇宙质量密度与ALOFA一致，但比HIPASS发现的大1.7倍。

英文摘要：

In this paper we describe results from the Arecibo Galaxy Environments Survey (AGES). The survey reaches column densities of ~3x10^18 cm^-2 and masses of ~10^7 M_O, over individual regions of order 10 sq deg in size, out to a maximum velocity of 18,000 km s^-1. Each surveyed region is centred on a nearby galaxy, group or cluster, in this instance the NGC7448 group. Galaxy interactions in the NGC7448 group reveal themselves through the identification of tidal tails and bridges. We find ~2.5 times more atomic gas in the inter-galactic medium than in the group galaxies. We identify five new dwarf galaxies, two of which appear to be members of the NGC7448 group. This is too few, by roughly an order of magnitude, dwarf galaxies to reconcile observation with theoretical predictions of galaxy formation models. If they had observed this region of sky previous wide area blind HI surveys, HIPASS and ALFALFA, would have detected only 5% and 43% respectively of the galaxies we detect, missing a large fraction of the atomic gas in this volume. We combine the data from this paper with that from our other AGES papers (370 galaxies) to derive a HI mass function with the following Schechter function parameters alpha=-1.52+/-0.05, M^*=5.1+/-0.3x10^9 h_72^-2 M_O, phi=8.6+/-1.1x10-3 h_72^3 Mpc^-3 dex-1. Integrating the mass function leads to a cosmic mass density of atomic hydrogen of Omega_HI=5.3+/-0.8x10^-4 h_72^-1. Our mass function is steeper than that found by both HIPASS and ALFALFA (alpha=1.37 and 1.33 respectively), while our cosmic mass density is consistent with ALFALFA, but 1.7 times larger than found by HIPASS.

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英文摘要：

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