A Near-Infrared Spectroscopic Survey of K-selected Galaxies at z~2.3: Redshifts and Implications for Broadband Photometric Studies
Mariska Kriek, Pieter G. van Dokkum, Marijn Franx, Garth D. Illingworth, Danilo Marchesini, Ryan Quadri, Gregory Rudnick, Edward N. Taylor, Natascha M. Forster … 展开作者
Mariska Kriek, Pieter G. van Dokkum, Marijn Franx, Garth D. Illingworth, Danilo Marchesini, Ryan Quadri, Gregory Rudnick, Edward N. Taylor, Natascha M. Forster Schreiber, Eric Gawiser, Ivo Labbe, Paulina Lira, Stijn Wuyts
Using the Gemini Near-InfraRed Spectrograph (GNIRS), we have completed a near-infrared spectroscopic survey for K-bright galaxies at z~2.3, selected from the MUSYC survey. We derived spectroscopic redshifts from emission lines or from continuum features and shapes for all 36 observed galaxies. The continuum redshifts are driven by the Balmer/4000 Angstrom break, and have an uncertainty in dz/(1+z) of <0.019. We use this unique sample to determine, for the first time, how accurately redshifts and other properties of massive high-redshift galaxies can be determined from broadband photometric data alone. We find that the photometric redshifts of the galaxies in our sample have a systematic error of 0.08 and a random error of 0.13 in dz/(1+z). The systematic error can be reduced by using optimal templates and deep photometry; the random error, however, will be hard to reduce below 5%. The spectra lead to significantly improved constraints for stellar population parameters. For most quantities this improvement is about equally driven by the higher spectral resolution and by the much reduced redshift uncertainty. Properties such as the age, A_V, current star formation rate, and the star formation history are generally very poorly constrained with broadband data alone. Interestingly stellar masses and mass-to-light ratios are among the most stable parameters from broadband data. Nevertheless, photometric studies may overestimate the number of massive galaxies at 2<z<3, and thus underestimate the evolution of the stellar mass density. Finally,the spectroscopy supports our previous finding that red galaxies dominate the high-mass end of the galaxy population at z=2-3.
New insights on the accuracy of photometric redshift measurements
我们使用目前可用的最深、最完整的红移目录（哈勃深场（HDF）北，并补充新的HDF南红移数据）来最大限度地减少光度和光谱红移估计之间的残差。在z_spec 2.0处的良好一致性< 1.5 shows that model libraries provide a good description of the galaxy population. At z_spec >，当星际和星系间介质的吸收模型被改进时，光度和光谱红移之间的系统位移减小。因此，在0 < z < 6的整个红移范围内，光度红移和光谱红移之间的残差大约减半。对于比光谱极限更暗的天体，测光红移不确定性的主要来源与测光误差有关，可以用蒙特卡罗模拟进行评估。
Preparation of the COROT space mission: fundamental stellar parameters determinations from photometric and spectroscopic analyses for COROT potential target candidates
A photometric and spectroscopic study of dwarf and giant galaxies in the Coma cluster - V. Dependence of the spectroscopic properties on location in the cluster
Pulsation properties of the $β$ Cephei star SY Equ from combined photometric and spectroscopic data
本文对快速旋转的仙王座$β$星SY Equ进行了同时多色$uvyI_{\rm C}$测光和低分辨光谱分析。从测光时间序列，我们确认的主要脉动频率，$f_1$ = 6.029 d $^{-1}$，我们发现了两个额外的模式的证据。在光谱学中，最高峰出现在$f_{\rm a}$ = 0.197 d $^{-1}$或其别名0.803 d $^{-1}$处。它既可以解释为二元运动，也可以解释为$g$模式脉动。此外，我们揭示了脉动模式的频率约为6.029 d $^{-1}$，即相同的占主导地位的光度变化，和一些新的候选人。对于主频率，我们得到的模式识别结合光度和光谱观测。从非绝热脉动计算，我们表明，在SY Equ的主模式的频率是一致的恒星模型的有效温度比许多文件中使用的低得多。
Photometric Redshift Estimation on SDSS Data Using Random Forests
鉴于SDSS DR 6的多波段光度数据，我们估计星系红移。我们采用了一个随机森林训练的颜色特征和光谱红移从80,000随机选择的主要星系产生从颜色到红移的映射，使估计和光谱红移之间的差异很小。我们的方法导致紧密的RMS分散在有限的测光误差的估计。此外，这种方法产生的误差分布，是接近高斯与参数估计提供可靠的置信区间独特的每个星系光度红移。
Stellar tracers of the Cygnus Arm I. Spectroscopic study of bright photometric candidates
我们提出了中等分辨率的光谱样本的恒星在银河系第二象限从文献中选择，因为他们的颜色表明，他们是适度变红的早期型恒星在非常大的距离。从衍生的光谱类型和观察到的颜色，我们计算到所有这些物体的距离。对于我们样本中相当大的一部分，我们发现距离远远超过了英仙座臂天体的预期，甚至允许相当慷慨的误差。在l= 150 degr-180 degr的区间内，有大量的距离超过4kpc的天体，它们很可能是在跟踪外旋臂或天鹅臂。特别是，我们发现关联Cam OB 3位于该旋臂上。基于我们的结果，关联Cas OB 4和Aur OB 2的范围和定义需要重新评估。
