We present grism spectra taken with the Advanced Camera for Surveys (ACS) to identify 29 red sources with (i 775 À z 850 ) ! 0:9 in the Hubble Ultra Deep Field (HUDF). Of these, 23 are found to be galaxies at redshifts between z ¼ 5:4 and 6.7, identified by the break at 1216 8 due to intergalactic medium (IGM) absorption; two are late-type dwarf stars with red colors; and four are galaxies with colors and spectral shapes similar to dust-reddened or old galaxies at redshifts z % 1 2. This constitutes the largest uniform, flux-limited sample of spectroscopically confirmed galaxies at such faint fluxes (z 850 27:5). Many are also among the most distant spectroscopically confirmed galaxies (at redshifts up to z ¼ 6:7). We find a significant overdensity of galaxies at redshifts z ¼ 5:9 AE 0:2. Nearly two-thirds of the galaxies in our sample (15/23) belong to this peak. Taking into account the selection function and the redshift sensitivity of the survey, we get a conservative overdensity of at least a factor of 2 along the line of sight. The galaxies found in this redshift peak are also localized in the plane of the sky in a nonrandom manner, occupying about half of the ACS chip. Thus the volume overdensity is a factor of 4. The star formation rate derived from detected sources in this overdense region is sufficient to reionize the local IGM.

We present a multiwavelength analysis of Swift GRB 061007. The 2 m robotic Faulkes Telescope South began observing 137 s after the onset of the -ray emission, when the optical counterpart was already decaying from R $ 10:3 mag, and continued observing for the next 5.5 hr. These observations begin during the final -ray flare and continue through and beyond a long, soft tail of -ray emission whose flux shows an underlying simple power-law decay identical to that seen at optical and X-ray wavelengths, with temporal slope $ 1:7 (F / t À ). This remarkably simple decay in all of these bands is rare for Swift bursts, which often show much more complex light curves. We suggest the afterglow emission begins as early as 30Y100 s and is contemporaneous with the ongoing variable prompt emission from the central engine, but originates from a physically distinct region dominated by the forward shock. The observed multiwavelength evolution of GRB 061007 is explained by an expanding fireball whose optical, X-ray, and late-time -ray emission is dominated by emission from a forward shock with typical synchrotron frequency, m , that is already below the optical band as early as t ¼ 137 s and a cooling frequency, c , above the X-ray band to at least t ¼ 10 5 s. In contrast, the typical frequency of the reverse shock lies in the radio band at early time. We suggest that the unexpected lack of bright optical flashes from the majority of Swift GRBs may be explained with a low m originating from small microphysics parameters, e and B . Finally, the optical light curves imply a minimum jet opening angle ¼ 4:7, and no X-ray jet break before t $ 10 6 s makes GRB 061007 a secure outlier to spectral energy correlations.

While most of the inter-galactic medium (IGM) today is permeated by ionized hydrogen, it was largely filled with neutral hydrogen for the first 700 million years after the Big Bang. The process that ionized the IGM (cosmic reionization) is expected to be spatially inhomogeneous, with fainter galaxies playing a significant role. However, we still have only a few direct constraints on the reionization process. Here we report the first spectroscopic confirmation of two galaxies and very likely a third galaxy in a group (hereafter EGS77) at redshift z = 7.7, merely 680 Myrs after the Big Bang. The physical separation among the three members is < 0.7 Mpc. We estimate the radius of ionized bubble of the brightest galaxy to be about 1.02 Mpc, and show that the individual ionized bubbles formed by all three galaxies likely overlap significantly, forming a large yet localized ionized region, which leads to the spatial inhomogeneity in the reionization process. It is striking that two of three galaxies in EGS77 are quite faint in the continuum, thanks to our selection of reionizing sources using their Lyman-α line emission. Indeed, one is the faintest spectroscopically confirmed galaxy yet discovered at such high redshifts. Our observations provide direct constraints in the process of cosmic reionization, and allow us to investigate the properties of sources responsible for reionizing the universe.

We present our measurements of the Hα, [Oiii], and [Oii] luminosity functions as part of the Lyman Alpha Galaxies at Epoch of Reionization (LAGER) survey using our samples of 1577 z = 0.47 Hα-, 3933 z = 0.93 [Oiii]-, and 5367 z = 1.59 [Oii]selected emission line galaxies in a 3 deg 2 single, CTIO/Blanco DECam pointing of the COSMOS field. Our observations reach 5σ depths of 8.2 × 10 −18 erg s −1 cm −2 and comoving volumes of (1 − 7) × 10 5 Mpc 3 making our survey one of the deepest narrowband surveys. We select our emission line galaxies via spectroscopic confirmation, photometric redshifts, and color-color selections. We measure the observed luminosity functions for each sample and find best-fits of φ = 10 −3.16 +0.09 −0.09 Mpc −3 and L = 10 41.72 +0.09 −0.09 erg s −1 for Hα, φ = 10 −2.16 +0.10 −0.12 Mpc −3 and L = 10 41.38 +0.07 −0.06 erg s −1 for [Oiii], and φ = 10 −1.97 +0.07 −0.07 Mpc −3 and L = 10 41.66 +0.03 −0.03 erg s −1 for [Oii], with α fixed to −1.75, −1.6, and −1.3, respectively. An excess of bright > 10 42 erg s −1 [Oiii] emitters is observed and may be due to AGN contamination. Corrections for dust attenuation are applied assuming A Hα = 1 mag. We also design our own empirical rest-frame g − r calibration using SDSS DR12 data, test it against our z = 0.47 Hα emitters with zCOSMOS 1D spectra, and calibrate it for (g − r) between −0.8 and 1.3 mag. Dust and AGN-corrected star formation rate densities (SFRDs) are measured as log 10 ρ SFR /(M yr −1 Mpc −3 ) = −1.63 ± 0.04, −1.07 ± 0.06, and −0.90 ± 0.10 for Hα, [Oiii], and [Oii], respectively. We find our [Oiii] and [Oii] samples fully trace cosmic star formation activity at their respective redshifts in comparison to multi-wavelength SFRDs, while the Hα sample traces ∼ 70 percent of the total z = 0.47 SFRD.

The muntjacs (Muntiacus, Cervidae) are famous for their rapid and radical karyotypic diversification via repeated tandem chromosome fusions, constituting a paradigm for the studies of karyotypic evolution. Of the five muntjac species with defined karyotypes, three species (i.e. Muntiacus reevesi, 2n = 46; M. m. vaginalis, 2n = 6/7; and M. crinifrons, 2n = 8/9) have so far been investigated by a combined approach of comparative chromosome banding, chromosome painting and BAC mapping. The results demonstrated that extensive centromere-telomere fusions and a few centric fusions are the chromosomal mechanisms underlying the karyotypic evolution of muntjacs. Here we have applied the same approach to two additional muntjac species with less well-characterized karyotypes, M. feae (2n = 14 male ) and M. gongshanensis (2n = 8 female). High-resolution G-banded karyotypes for M. feae and M. gongshanensis are provided. The integrated analysis of hybridization results led to the establishment of a high-resolution comparative map between M. reevesi, M. feae, and M. gongshanensis, proving that all tandem fusions underpinning the karyotypic evolution of these two muntjac species are also centromere-telomere fusions. Furthermore, the results have improved our understanding of the karyotypic relationships of extant muntjac species and provided compelling cytogenetic evidence that supports the view that M. crinifrons, M. feae, and M. gongshanensis should each be treated as a distinct species.