The stellar content of low redshift BL Lacertae host galaxies from multicolour imaging
The stellar content of low redshift BL Lacertae host galaxies from multicolour imaging
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DOI：
10.1051/0004-6361:20078202
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发表时间：
2007-09
影响因子：
6.5
通讯作者：
T. Hyvönen;J. Kotilainen;R. Falomo;E. Örndahl;T. Pursimo
中科院分区：
文献类型：
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作者：
T. Hyvönen;J. Kotilainen;R. Falomo;E. Örndahl;T. Pursimo
上下文我们提出了B波段成像的18个低红移（$z\leq 0.3 $）BL紫胶天体，其宿主星系以前解决的R-波段和近红外H-波段。对于一个子集的对象，U-和V-波段成像也被提出。目标。这些多波长的数据被用来调查的蓝色，红色，近红外的颜色和颜色梯度的BL拉克的主机星系与其他椭圆星系的核活动和没有。方法.对于在B和V波段观测到的所有BL拉克，以及在$z U波段观测到的所有天体，宿主星系都被清晰地分辨出来。在所有情况下，星系都可以用椭圆模型很好地表示，平均绝对星等M B =-21.6\pm0.7 $，平均标度长度R {\rm e}= 7.6\pm3.2 $kpc.因此BL Lac宿主星系是明亮的（大质量）椭圆星系，与以前在其他波段的研究一致。结果最佳拟合的B带Kormendy关系式为（$\mu_{\rm e}= 3.3\log R_{\rm e}$（kpc）+18.4 mag arcsec-2），这与正常椭圆星系和射电星系的关系式相当吻合。这种结构和动力学的相似性表明，所有大质量椭圆星系都可以经历核活动，而不会对其全球结构产生重大影响。BL Lac天体的蓝/近红外综合色（平均$B-H = 3.5\pm 0.5 $）和色梯度（平均Δ（$B-R $）/$\Delta（\log r）=-0.14\pm 0.75 $）的分布比正常椭圆星系的宽得多，并且大多数BL Lac天体的主色和/或色梯度比正常椭圆星系的主色和/或色梯度更陡。结论.蓝色可能是由年轻的恒星群体组成，并表明由相互作用/合并事件引起的星星形成与核活动开始之间的联系。这一结果证实了恒星人口模型，表明存在的年轻/中间年龄的人口在大多数的样本，在协议与低红移类星体主机。缺乏强烈的相互作用的迹象可能需要一个显着的时间延迟之间的事件与相关的星星形成插曲和开始的核活动。
Context. We present B -band imaging of 18 low redshift ($z \leq 0.3$) BL Lac objects for which their host galaxies were previously resolved in the R -band and the near-infrared H -band. For a subset of the objects, U - and V -band imaging also is presented. Aims. These multiwavelength data are used to investigate the blue–red–near-infrared colours and the colour gradients of the host galaxies of BL Lacs in comparison with other elliptical galaxies with and without nuclear activity. Methods. For all the BL Lacs observed in the B - and V -bands, and all objects at $z U -band, the host galaxy is clearly resolved. In all cases galaxies are well represented by an elliptical model, with average absolute magnitude $M_B = -21.6\pm0.7$ and average scale length $R_{\rm e} = 7.6\pm 3.2$ kpc. BL Lac host galaxies are therefore luminous (massive) elliptical galaxies, in agreement with previous studies in other bands. Results. The best-fit B -band Kormendy relation of ($\mu_{\rm e} = 3.3 \log R_{\rm e}$ (kpc) + 18.4 mag arcsec -2 ) is in reasonable agreement with that obtained for normal ellipticals and radio galaxies. This structural and dynamical similarity indicates that all massive elliptical galaxies can experience nuclear activity without significant perturbation of their global structure. The distributions of the integrated blue/near–infrared colour (with average $B-H = 3.5\pm0.5$) and colour gradient (with average Δ ($B-R$)/$\Delta (\log r) = -0.14\pm 0.75$) of the BL Lac hosts are much wider than those for normal ellipticals, and most BL Lac objects have bluer hosts and/or steeper colour gradients than those in normal ellipticals. Conclusions. The blue colours are likely caused by a young stellar population component, and indicates a link between star formation caused by an interaction/merging event and the onset of the nuclear activity. This result is corroborated by stellar population modelling, indicating a presence of young/intermediate age populations in the majority of the sample, in agreement with low redshift quasar hosts. The lack of strong signs of interaction may require a significant time delay between the event with associated star formation episodes and the start of the nuclear activity.