标题： 哈勃发射星系与z = 2.2时的宇宙恒星形成率 显示英文标题

标题： Halpha emitting galaxies and the cosmic star formation rate at z = 2.2

摘要： 在一项覆盖面积为100平方角分、包括哈勃深场南侧的WFPC2和STIS区域的2.1微米窄波段成像巡天中，检测到大约10个候选的发射Hα辐射的星系，红移z = 2.2。其中六个随后使用ESO VLT上的ISAAC仪器通过光谱确认。 根据它们的Hα流量推导出的单个星系的恒星形成率在20-35个太阳质量/年之间，未进行消光修正；而从它们的静止框架紫外连续流量推导出的SFRs则低至四倍，这与Hα较低的消光一致。 速度弥散度通常约为100公里/秒，其中一个星系，在最有利条件下观测，显示出一个终端速度约140公里/秒的旋转曲线，在约3千秒差距半径处，这在附近螺旋星系的观测范围内。 这些系统看起来是在高红移下相对较大的系统。 与Yan等人（1999）的HST NICMOS光栅Hα巡天比较表明，在z ~ 1.3和2.2之间Hα亮度函数几乎没有或没有演化。 推断出的在z = 2.2时的恒星形成率密度为0.12个太阳质量/Mpc³/年，这也等于Steidel等人（1999）从消光校正后的UV连续流量得出的z ~ 3-4.5时的值。 显示英文摘要

摘要： About 10 candidate Halpha emitting galaxies at z = 2.2 have been detected in a 2.1 um narrow band imaging survey covering an area of 100 sq. arcmin including the WFPC2 and STIS fields in the Hubble Deep Field South. Six of these have subsequently been confirmed spectroscopically using ISAAC at the ESO VLT. Star formation rates of the individual galaxies derived from their Halpha fluxes are 20-35 Msolar/yr, without any correction for extinction, whereas SFRs derived from their rest frame UV continuum fluxes are up to a factor of 4 lower - consistent with lower extinction to Halpha. Velocity dispersions are typically ~ 100km/s and one galaxy, observed under the most favorable conditions, shows a rotation curve with a terminal velocity ~ 140 km/s at ~ 3kpc radius which is within the range observed for nearby spiral galaxies. These thus appear to be relatively massive systems at high redshift. Comparison with the HST NICMOS grism Halpha survey of Yan et al. (1999) reveals little or no evolution in the Halpha luminosity function between z ~ 1.3 and 2.2. The inferred star formation rate density of 0.12 Msolar/Mpc^3/yr at z = 2.2 is also equal to that at z ~ 3-4.5 derived by Steidel et al.(1999) from extinction corrected UV continuum fluxes.