An Ultraviolet/Optical Atlas of Bright Galaxies
An Ultraviolet/Optical Atlas of Bright Galaxies
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DOI：
10.1086/318953
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发表时间：
2001-02
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通讯作者：
P. Marcum;R. O’Connell;M. Fanelli;R. Cornett;W. Waller;R. Bohlin;S. Neff;M. S. Roberts;Andrew M. Smith;K. Cheng;N. Collins;G. Hennessy;J. K. Hill;R. Hill;P. Hintzen;W. Landsman;R. Ohl;R. Parise;Eric P. Smith;W. Freedman;L. Kuchinski;B. Madore;R. Angione;C. Palma;F. Talbert;T. P. Stecher
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作者：
P. Marcum;R. O’Connell;M. Fanelli;R. Cornett;W. Waller;R. Bohlin;S. Neff;M. S. Roberts;Andrew M. Smith;K. Cheng;N. Collins;G. Hennessy;J. K. Hill;R. Hill;P. Hintzen;W. Landsman;R. Ohl;R. Parise;Eric P. Smith;W. Freedman;L. Kuchinski;B. Madore;R. Angione;C. Palma;F. Talbert;T. P. Stecher
我们给出了43个附近选定的所有形态类型的星系在紫外线和光学波长下的宽视场图像和光度测量。在Astro-1空间实验室任务期间，使用紫外线成像望远镜(UIT)获得了1500和2500ä两个宽带的紫外线(UV)图像。UV图像具有~3‘’分辨率，而比较的地面ccd图像集(在B、V、R和Hα中的一个或多个中)具有与UV帧紧密匹配的像素比例和视场。该图集由多波段图像和UV/光学表面亮度和颜色分布的曲线图组成。其他相关参数，如综合测光和半光半径，也列在表格中。在附录中，我们以“历史加权函数”的形式讨论了不同波段对星系恒星形成历史的敏感性，并强调了紫外线观测作为过去10-1000Myr期间演化的探测器的重要性。我们发现，由于恒星群在空间上的不均匀，UV星系的形态通常与可见光波段的形态有很大的不同。对于中等哈勃类型的系统，从Sa到Sc，差异是相当明显的，但对于椭圆盘或晚型盘来说，差异就不那么明显了。正常椭圆形和大型螺旋凸起在UV下较暗且更紧凑。然而，它们通常表现出平滑的UV轮廓，远UV/光学颜色梯度比光学/IR波长下的任何颜色梯度都要大。这些情况下的远紫外光可能是由占主导地位的、低质量、富含金属的星体中的极端水平分支恒星及其后代产生的。Sa和Sb螺旋线大凸起中的冷星在紫外线下褪色，而其圆盘中的热OB星变亮，因此它们的哈勃分类明显晚了很多。在远紫外光中，早期类型的螺旋通常表现为特殊的环状系统。在一些螺旋圆盘中，紫外线明亮的结构紧密地勾勒出螺旋形图案；在其他一些圆盘中，圆盘可能比在光学波长下更碎片化和混乱。在我们的样本中，明亮的活动星系核(AGN)对积分紫外光的贡献从不到10%到近100%不等。许多系统的内盘都有不同寻常的紫外亮结构，包括环、致密结和恒星爆发核，它们很容易在高红移类似物中主宰紫外光。在螺旋盘中，远紫外光中有一大部分是扩散的，而不是紧密集中在恒星形成区域的，但这一比例是可变的。普通螺旋盘中的尘埃不能控制紫外线的形态，即使在一些高倾斜度的盘系统中也是如此。最严重的消光显然局限于薄层和年轻的H II复合体的直接附近；紫外线来自较厚的恒星分布，通过光破坏或风而疏散尘埃的区域，或由于强烈的尘埃笨拙。只有在尘埃层受到干扰的情况下，尘埃才似乎是紫外线形态的主要因素。M82的紫外线明亮的羽流表明，尘埃对紫外线光子的散射在某些情况下可能是重要的。在另一篇论文中，我们讨论了来自Astro-2任务的远紫外线数据，以及另外35个星系的光学比较，重点是面对面的螺旋。
We present wide-field imagery and photometry of 43 selected nearby galaxies of all morphological types at ultraviolet and optical wavelengths. The ultraviolet (UV) images, in two broad bands at 1500 and 2500 Å, were obtained using the Ultraviolet Imaging Telescope (UIT) during the Astro-1 Spacelab mission. The UV images have ~3'' resolution, and the comparison sets of ground-based CCD images (in one or more of B, V, R, and Hα) have pixel scales and fields of view closely matching the UV frames. The atlas consists of multiband images and plots of UV/optical surface brightness and color profiles. Other associated parameters, such as integrated photometry and half-light radii, are tabulated. In an appendix, we discuss the sensitivity of different wavebands to a galaxy's star formation history in the form of "history weighting functions" and emphasize the importance of UV observations as probes of evolution during the past 10-1000 Myr. We find that UV galaxy morphologies are usually significantly different from visible band morphologies as a consequence of spatially inhomogeneous stellar populations. Differences are quite pronounced for systems in the middle range of Hubble types, Sa through Sc, but less so for ellipticals or late-type disks. Normal ellipticals and large spiral bulges are fainter and more compact in the UV. However, they typically exhibit smooth UV profiles with far-UV/optical color gradients which are larger than any at optical/IR wavelengths. The far-UV light in these cases is probably produced by extreme horizontal branch stars and their descendants in the dominant, low-mass, metal-rich population. The cool stars in the large bulges of Sa and Sb spirals fade in the UV while hot OB stars in their disks brighten, such that their Hubble classifications become significantly later. In the far-UV, early-type spirals often appear as peculiar, ringlike systems. In some spiral disks, UV-bright structures closely outline the spiral pattern; in others, the disks can be much more fragmented and chaotic than at optical wavelengths. Contributions by bright active galactic nuclei (AGNs) to the integrated UV light in our sample range from less than 10% to nearly 100%. A number of systems have unusual UV-bright structures in their inner disks, including rings, compact knots, and starburst nuclei, which could easily dominate the UV light in high-redshift analogs. A significant but variable fraction of the far-UV light in spiral disks is diffuse rather than closely concentrated to star-forming regions. Dust in normal spiral disks does not control UV morphologies, even in some highly inclined disk systems. The heaviest extinction is apparently confined to thin layers and the immediate vicinity of young H II complexes; the UV light emerges from thicker star distributions, regions evacuated of dust by photodestruction or winds, or by virtue of strong dust clumpiness. Only in cases where the dust layers are disturbed does dust appear to be a major factor in UV morphology. The UV-bright plume of M82 indicates that dust scattering of UV photons can be important in some cases. In a companion paper, we discuss far-UV data from the Astro-2 mission and optical comparisons for another 35 galaxies, emphasizing face-on spirals.