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arXiv 0705.3462astro-ph
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z<0.5时强吸收系统CaII QSO的宿主星系

The host galaxies of strong CaII QSO absorption systems at z<0.5

Berkeley J. Zych, Michael T. Murphy, Max Pettini, Paul C. Hewett, Emma V. Ryan-Weber, Sara L. Ellison

摘要:

我们提出了新的成像和光谱观测领域的五个类星体非常强的干预钙吸收系统在红移z<0.5选择从斯隆数字巡天。最近的研究表明,这些非常罕见的吸收剂可能与阻尼莱曼α系统(DLAs)。在所有五种情况下,我们确定一个星系的红移的CaII系统的碰撞参量高达~24千秒差距。五分之四的星系是明亮的(L ~L*),富含金属(Z ~Zsun),质量大(速度色散,sigma ~100 km/s)的螺旋星系。它们的恒星形成率很高,SFR = 0.3 - 30 Msun/yr。在我们的分析中,我们特别注意校正观测到的恒星吸收和尘埃消光的发射线通量。我们表明,这些影响是重要的正确的SFR估计,他们的忽视在以前的低Z研究DLA选定的星系可能导致低估的恒星形成活动,至少在一些DLA主机。我们讨论了调用选择星系和DLAs之间可能的联系,并概述了未来的观测,这将有助于澄清这些不同类别的类星体吸收体之间的关系。

英文摘要:

We present new imaging and spectroscopic observations of the fields of five QSOs with very strong intervening CaII absorption systems at redshifts z<0.5 selected from the Sloan Digital Sky Survey. Recent studies of these very rare absorbers indicate that they may be related to damped Lyman alpha systems (DLAs). In all five cases we identify a galaxy at the redshift of the CaII system with impact parameters up to ~24 kpc. In four out of five cases the galaxies are luminous (L ~L*), metal-rich (Z ~Zsun), massive (velocity dispersion, sigma ~100 km/s) spirals. Their star formation rates, deduced from Halpha emission, are high, in the range SFR = 0.3 - 30 Msun/yr. In our analysis, we paid particular attention to correcting the observed emission line fluxes for stellar absorption and dust extinction. We show that these effects are important for a correct SFR estimate; their neglect in previous low-z studies of DLA-selected galaxies has probably led to an underestimate of the star formation activity in at least some DLA hosts. We discuss possible links between CaII-selected galaxies and DLAs and outline future observations which will help clarify the relationship between these different classes of QSO absorbers.

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