通过模型和非参数拟合对z=0-1星系尺寸测量的鲁棒性
On The Robustness of z=0-1 Galaxy Size Measurements Through Model and Non-Parametric Fits
摘要：
我们提出了附近（z=0.01-0.02）斯隆数字巡天星系的大小-恒星质量关系，样品的颜色，形态，Sersic指数n，和特定的恒星形成率。使用几种常用的尺寸测量技术，包括单Sersic拟合，双组分Sersic模型和非参数方法。通过简单的模拟，我们表明，非参数和两个组件的Sersic方法提供了最强大的有效半径测量，而那些基于单Sersic配置文件往往被高估，特别是对于大规模的红色/早型星系。使用我们的鲁棒尺寸，我们表明，对于所有子样本，质量-尺寸关系在低恒星质量处较浅，在~ 3-4 x 10^{10} \msun以上较陡。分类为晚型、低n和恒星形成的星系的质量-尺寸关系是相互一致的，而蓝色星系遵循一个稍微陡峭的关系。早期型，高n，红色和静止星系的质量尺寸关系都彼此一致，但在高质量端比以前的结果有点陡峭。为了在高红移下测试潜在的系统学，我们人为地将我们的样本（包括表面亮度变暗和分辨率降低）红移到z=1，并使用单个Serisc配置文件重新拟合星系。这些星系在红移前后的大小是一致的，我们得出的结论是，系统的影响，大小和质量关系在z ~ 1可以忽略不计。有趣的是，由于在高红移时较差的物理分辨率会洗掉明亮的星系子结构，因此单Sersic拟合似乎在高z时提供了比附近分辨率良好的星系更可靠和无偏的有效半径测量。
英文摘要：
We present the size-stellar mass relations of nearby (z=0.01-0.02) Sloan Digital Sky Survey galaxies, for samples selected by color, morphology, Sersic index n, and specific star formation rate. Several commonly employed size measurement techniques are used, including single Sersic fits, two-component Sersic models, and a non-parametric method. Through simple simulations, we show that the non-parametric and two-component Sersic methods provide the most robust effective radius measurements, while those based on single Sersic profiles are often overestimates, especially for massive red/early-type galaxies. Using our robust sizes, we show for all sub-samples that the mass-size relations are shallow at low stellar masses and steepen above ~ 3-4 x 10^{10}\msun. The mass-size relations for galaxies classified as late-type, low-n, and star-forming are consistent with each other, while blue galaxies follow a somewhat steeper relation. The mass-size relations of early-type, high-n, red, and quiescent galaxies all agree with each other but are somewhat steeper at the high-mass end than previous results. To test potential systematics at high redshift, we artificially redshifted our sample (including surface brightness dimming and degraded resolution) to z=1 and re-fit the galaxies using single Serisc profiles. The sizes of these galaxies before and after redshifting are consistent and we conclude that systematic effects in sizes and the size-mass relation at z ~ 1 are negligible. Interestingly, since the poorer physical resolution at high redshift washes out bright galaxy substructures, single-Sersic fitting appears to provide more reliable and unbiased effective radius measurements at high z than for nearby, well-resolved galaxies.
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