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首页> 外文期刊>Publications of the Astronomical Society of the Pacific >Flux-calibrated emission-line imaging of extended sources using GTC/OSIRIS tunable filters
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Flux-calibrated emission-line imaging of extended sources using GTC/OSIRIS tunable filters

机译：使用GTC / OSIRIS可调滤波器对扩展源进行通量校准的发射线成像

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摘要

We investigate the utility of the tunable filters (TFs) for obtaining flux-calibrated emission-line maps of extended objects such as galactic nebulae and nearby galaxies using the Optical System for Imaging and low Resolution Integrated Spectroscopy (OSIRIS) at the 10.4-m Gran Telescopio Canarias (GTC). Despite the relatively large field of view (FoV) of OSIRIS (8' × 8'), the change in wavelength across the field (~80 ?) and the long tail of the TF spectral response function are hindrances for obtaining accurate flux-calibrated emission-line maps of extended sources. The purpose of this article is to demonstrate that emission-line maps useful for diagnostics of nebulae can be generated over the entire FoV of OSIRIS if we make use of theoretically wellunderstood characteristics of TFs. We have successfully generated the flux-calibrated images of the nearby large late-type spiral galaxy M101 in the emission lines of Hα, [N II]λ6583, [S II]λ6716 and [S II]λ6731.We find that the present uncertainty in setting the central wavelength of TFs (~1 ?) is the biggest source of error in the emission-line fluxes. By comparing the Hα fluxes of H II regions in our images with the fluxes derived from Hα images obtained using narrow-band filters, we estimate an error of ~11% in our fluxes. The flux-calibration of the images was carried out by fitting the Sloan Digital Sky Survey (SDSS) griz magnitudes of in-frame stars with the stellar spectra from the SDSS spectral database. This method resulted in an accuracy of 3% in flux-calibration of any narrow-band image, which is as good as, if not better than, what has been feasible using the observations of spectrophotometric standard stars. Thus time-consuming calibration images need not be taken. A user-friendly script under the IRAF environment was developed and is available on request.
机译：我们研究了可调谐滤波器（TFs）的实用性，使用成像和低分辨率集成光谱学（OSIRIS）光学系统在10.4米Gran上获得了扩展对象（例如银河星云和附近星系）的通量校准的发射线图Telescopio Canarias（GTC）。尽管OSIRIS的视场（FoV）相对较大（8'×8'），但整个视场的波长变化（〜80？）和TF光谱响应函数的长尾巴仍然妨碍获得准确的通量校准扩展源的发射线图。本文的目的是证明，如果我们利用理论上公认的TF的特征，可以在OSIRIS的整个FoV上生成可用于星云诊断的发射线图。我们成功地在Hα，[N II]λ6583，[S II]λ6716和[S II]λ6731的发射线中生成了附近大型晚期旋涡星系M101的通量校正图像。我们发现当前的不确定性设置TFs的中心波长（〜1？）是发射线通量误差的最大来源。通过将我们图像中H II区的Hα通量与使用窄带滤波器获得的Hα图像派生的通量进行比较，我们估计通量中的误差约为11％。图像的通量校准是通过使用标清光谱数据库中的恒星光谱拟合帧内恒星的斯隆数字天空测量（SDSS）格里兹量来进行的。这种方法在任何窄带图像的通量校准中都可以达到3％的精度，这与使用分光光度标准星体观测所获得的效果一样好，甚至更好。因此不需要耗时的校准图像。在IRAF环境下开发了一个用户友好的脚本，可应要求提供。

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