用ugrizYJHK光度红移补充的0.04 < z < 0.15色选样品的致密星系和尺寸质量分布
Compact galaxies and the size-mass galaxy distribution from a colour-selected sample at 0.04 < z < 0.15 supplemented by ugrizYJHK photometric redshifts
摘要：
星系的大小-质量分布是星系演化的一个重要特征。大质量致密星系是恒星形成过程中高红移阶段的潜在遗迹。其中一些可能在SDSS成像中几乎无法分辨，因此不包括在星系样本中。为了克服这一点，从SDSS和UKIDSS光度法的组合中选择样品以使r<17.8。这是使用颜色选择，然后通过使用定标通量匹配（SFM）获得准确的光度红移（photo-z）来完成的。与光谱红移（spec-z）相比，SFM获得了0.0125的1-sigma散射，只有0.3%的离群值（Delta：ln（1+z）>0.06）。在2300平方度上获得了163186个星系的样本，其中0.04<z<0.15。使用SPEC-Z和PHOTO-Z的组合。继Barro等人之后，用log：Sigma_1.5=log：M_*-1.5log：reff定义紧度。紧凑星系的光谱完整性为76%（log：Sigma_1.5>10.5），而正常大小的星系为92%。这种差异主要归因于SDSS的“纤维碰撞”，而不是主要星系样本选择的完整性。使用环境过密度，这证实了与正常大小的星系相比，紧凑的静止星系更有可能在高密度环境中被发现。通过与来自3D-HST的高红移样本进行比较，log：Sigma_1.5分布函数显示出显著的演变，这是与EAGLE等模拟进行比较的一种令人信服的方式。在SDSS-UKIDSS样本中，致密静止星系的数密度从z~2下降到log（n/Mpc^-3）=-5.3+-0.4，下降了约30倍。不确定性主要由log：Sigma_1.5中的陡峭截止值决定，使用该完整样本最终证明了这一点。
英文摘要：
The size-mass galaxy distribution is a key diagnostic for galaxy evolution. Massive compact galaxies are potential surviving relics of a high-redshift phase of star formation. Some of these could be nearly unresolved in SDSS imaging and thus not included in galaxy samples. To overcome this, a sample was selected from the combination of SDSS and UKIDSS photometry to r<17.8. This was done using colour-colour selection, and then by obtaining accurate photometric redshifts (photo-z) using scaled flux matching (SFM). Compared to spectroscopic redshifts (spec-z), SFM obtained a 1-sigma scatter of 0.0125 with only 0.3% outliers (Delta:ln(1+z)>0.06). A sample of 163186 galaxies was obtained with 0.04<z<0.15 over 2300 sq.deg. using a combination of spec-z and photo-z. Following Barro et al., log:Sigma_1.5=log:M_*-1.5log:reff was used to define compactness. The spectroscopic completeness was 76% for compact galaxies (log:Sigma_1.5>10.5) compared to 92% for normal-size galaxies. This difference is primarily attributed to SDSS `fibre collisions' and not the completeness of the main galaxy sample selection. Using environmental overdensities, this confirms that compact quiescent galaxies are significantly more likely to be found in high-density environments compared to normal-size galaxies. By comparison with a high-redshift sample from 3D-HST, log:Sigma_1.5 distribution functions show significant evolution, with this being a compelling way to compare with simulations such as EAGLE. The number density of compact quiescent galaxies drops by a factor of about 30 from z~2 to log(n/Mpc^-3)=-5.3+-0.4 in the SDSS-UKIDSS sample. The uncertainty is dominated by the steep cut off in log:Sigma_1.5, which is demonstrated conclusively using this complete sample.
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