Redshift Limits of BL Lacertae Objects from Optical Spectroscopy
Redshift Limits of BL Lacertae Objects from Optical Spectroscopy
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DOI：
10.1051/0004-6361:20078492
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发表时间：
2007-11
期刊：
影响因子：
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通讯作者：
J. Finke;J. Shields;M. Boettcher;S. Basu
中科院分区：
文献类型：
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作者：
J. Finke;J. Shields;M. Boettcher;S. Basu
背景：BL Lacertae天体已成为最近许多多波长运动、连续光谱变异性研究以及理论光谱和变异性建模的目标。要对这类研究的结果作出有意义的解释，就需要对这些天体的红移有可靠的了解；然而，许多红移仍然是未知的或不确定的。目的：因此，我们希望确定或限制6个未知或鲜为人知的BL Lac天体的红移。方法：利用MDM 2.4 m Hiltner望远镜对这些物体进行观测。虽然没有探测到光谱特征，因此也就无法测量到红移，但根据预期的宿主星系吸收特征的等效宽度，我们给这些天体分配了较低的红移极限。通过假设宿主星系是标准的烛光星系，并使用从文献中获得的宿主星系视星等，我们还估计了一些天体的红移。结果：1219+285通常使用的$z=0.102$的红移几乎可以肯定是错误的，而其他研究对象的红移仍未确定。
Context: BL Lacertae objects have been the targets for numerous recent multiwavelength campaigns, continuum spectral variability studies, and theoretical spectral and variability modeling. A meaningful interpretation of the results of such studies requires a reliable knowledge of the objects' redshifts; however, the redshifts for many are still unknown or uncertain. Aims: Therefore, we hope to determine or constrain the redshifts of six BL Lac objects with unknown or poorly known redshifts. Methods: Observations were made of these objects with the MDM 2.4 m Hiltner telescope. Although no spectral features were detected, and thus no redshifts could be measured, lower redshift limits were assigned to the objects based on the expected equivalent widths of absorption features in their host galaxies. Redshifts were also estimated for some objects by assuming the host galaxies are standard candles and using host galaxy apparent magnitudes taken from the literature. Results: The commonly used redshift of $z=0.102$ for 1219+285 is almost certainly wrong, while the redshifts of the other objects studied remain undetermined.