We present results from a blind, spectroscopic survey for redshift ~5.7 Lyman-alpha-emitting galaxies using the Inamori Magellan Areal Camera and Spectrograph. A total of ~200 square arcminutes were observed in the COSMOS and LCIRS fields using a narrowband filter, which transmits between atmospheric emission lines at 8190 A, and a mask with 100 longslits. This observing technique provides higher emission-line sensitivity than narrowband imaging and probes larger volumes than strong lensing. We find 170 emission-line galaxies and identify their redshifts spectroscopically. We confirm three Lyman-alpha emitting galaxies (LAEs), the first discovered using multislit-narrowband spectroscopy. Their line profiles are narrow, but fitted models suggest instrinsic, unattenuated widths 400 km/s FWHM. The red wing of the line profiles present features consistent with galactic winds. The star formation rates of these galaxies are at least 5-7 Msun/yr and likely a factor of two higher. We estimate the number density of L .ge. 5e42 erg/s LAEs is 9.0(+12,-4)e-5 Mpc-3 at redshift 5.7 and constrain the Schechter function parameters describing this population. Galaxies fainter than our detection limit may well be the primary source of ionizing photons at redshift ~ 6. We argue, however, that the break luminosity L* is not yet well constrained. If this break luminosity is near our detection limit, and somewhat lower than previous estimates, then the detected LAE population could be responsible for ionizing the intergalactic gas at redshift ~6. We discuss the potential of multislit-narrowband spectroscopy for deeper emission-line surveys.
Detection of H-alpha emission from the Magellanic Stream: evidence for an extended gaseous Galactic halo
我们分别探测到了表面亮度为$0.37 \pm 0.02$ Raylewald、$0.21 \pm 0.04$ R和$0.20 \pm 0.02$ R的微弱、漫射H $αemission from several points along the Magellanic Stream, using the Rutgers Fabry--Perot Interferometer at the CTIO 1.5-m telescope. At points on the leading edges of the H I clouds MS II, MS III, and MS IV, we detect H$ α发射，对应于1.0到0.5 \cmsixpc的发射测量值。我们已经观察到MS IV浓度附近的几个位置，并发现最强的发射是在尖锐的前缘密度梯度。在远离梯度的地方发射较少，在MS III和MS IV之间的中间位置，在云的前缘H $αsurface brightness is $ < 0.04 $ R. We attribute the H$ α发射是由于星系晕中电离气体的冲压压力加热了流云。这些观测结果表明，来自晕气体的冲压压力在将流从麦哲伦云中剥离出来的过程中发挥了重要作用。它们还表明在星系晕中存在相对较大密度的气体$n_{\rm H} \sim 10^{-4} cm^{-3}$，其…
First Detection of NaI D lines in High-Redshift Damped Lyman-alpha Systems
利用安装在Subaru望远镜上的红外光谱仪，利用AO系统获得了类星体APM 08279+5255的近红外（1.18-1.35微米）高分辨率光谱。我们在z=1.062和1.181的高红移DLA中检测到强的NaI D 5891，5897双峰吸收，证实了NaI的存在，这是Petitjean等人首次报道的静止框架UV NaI 3303.3，3303.9双峰。此外，我们在z=1.062 DLA中检测到一个新的NaI组分，在z=1.181 DLA中检测到四个新组分。利用碘化钠和HI柱密度之间的经验关系，我们发现，所有的“组件”有大HI柱密度，使每个组件被归类为DLA吸收。我们还检测到强NaI D吸收与MgII系统在z=1.173。由于在该系统中没有检测到其他金属吸收线在以前报道的光谱中的NaI吸收的速度（3.6年前观察到的），我们解释这个NaI吸收云可能出现在光学观测后的类星体的视线。这个新发现的云很可能是一个DLA的基础上估计其大HI柱密度。我们发现，在这些DLAs中的N（NaI）/N（CaII）比系统地小于在银河系中观察到的值;它们与在大麦云云中观察到的比值更一致。这与金属丰度较低的环境中粉尘消耗量一般较小的情况相一致。然而，z=1.181系统的所有五个云都具有高的N（NaI）/N（CaII）比，这是冷稠密气体的特征。我们初步认为，该系统的宿主星系可能是对APM 08279+5255引力透…
The XMM-Newton wide-field survey in the COSMOS field: III. optical identification and multiwavelength properties of a large sample of X-ray selected sources
