标题： 宇宙紫外光度密度来自哈勃深场星系的光度红移 显示英文标题

标题： The Ultraviolet Luminosity Density of the Universe from Photometric Redshifts of Galaxies in the Hubble Deep Field

摘要： 哈勃深场（HDF）和其他深度调查的研究显示，宇宙在红移1<z<2范围内出现了紫外（UV）光度密度的明显峰值，因此恒星形成率密度也出现了峰值。 我们使用HDF中星系的光度红移来确定共动紫外光度密度，并发现当正确考虑误差（特别是抽样误差）时，平坦分布与在z~1.5处有峰值的分布在统计上无法区分。 此外，我们通过在将所有星系流量校正到红移z=5后应用统一的表面亮度（SB）截断，来研究宇宙学表面亮度暗化对这些测量的影响。 我们发现，比较所有具有相同内在表面亮度灵敏度的星系，高内在SB区域对紫外光度密度的贡献从z~0增加到z~5时几乎增加了两个数量级。 这表明在高红移处存在一个恒星形成率非常高的天体群体，而在低红移处似乎不存在这样的天体。 因此，恒星形成的峰值可能出现在红移z~>5的更远处。 显示英文摘要

摘要： Studies of the Hubble Deep Field (HDF) and other deep surveys have revealed an apparent peak in the ultraviolet (UV) luminosity density, and therefore the star-formation rate density, of the Universe at redshifts 1<z<2. We use photometric redshifts of galaxies in the HDF to determine the comoving UV luminosity density and find that, when errors (in particular, sampling error) are properly accounted for, a flat distribution is statistically indistinguishable from a distribution peaked at z~1.5. Furthermore, we examine the effects of cosmological surface brightness (SB) dimming on these measurements by applying a uniform SB cut to all galaxy fluxes after correcting them to redshift z=5. We find that, comparing all galaxies at the same intrinsic surface brightness sensitivity, the UV luminosity density contributed by high intrinsic SB regions increases by almost two orders of magnitude from z~0 to z~5. This suggests that there exists a population of objects with very high star formation rates at high redshifts that apparently do not exist at low redshifts. The peak of star formation, then, may occur somewhere beyond a redshift z~>5.