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We present an atlas of 88 z ∼ 5.7 and 30 z ∼ 6.5 Lyα emitters obtained from a wide-field narrowband survey. We combined deep narrowband imaging in 120Å bandpass filters centered at 8150Å and 9140Å with deep BV RIz broadband imaging to select high-redshift galaxy candidates over an area of 4180 arcmin 2 . The goal was to obtain a uniform selection of comparable depth over the 7 targeted fields in the two filters. For the GOODS-N region of the HDF-N field, we also selected candidates using a 120Å filter centered at 9210Å. We made spectroscopic observations with Keck DEIMOS of nearly all the candidates to obtain the final sample of Lyα emitters. At the 3.3Å resolution of the DEIMOS observations the asymmetric profile for Lyα emission can be clearly seen in the spectra of nearly all the galaxies. We show that the spectral profiles are surprisingly similar for many of the galaxies and that the composite spectral profiles are nearly identical at z = 5.7 and z = 6.5. We analyze the distributions of line widths and Lyα equivalent widths and find that the lines are marginally narrower at the higher redshift, with median values of 0.77Å at z = 6.5 and 0.92Å at z = 5.7. The line widths have a dependence on the Lyα luminosity of the form ∼ L 0.3 α . We compare the surface densities and the luminosity functions at the two redshifts and find that there is a multiplicative factor of 2 decrease in the number density of bright Lyα emitters from z = 5.7 to z = 6.5, while the characteristic luminosity is unchanged.

Abstract. With the first direct detection of gravitational waves, the Advanced Laser Interferometer Gravitational-wave Observatory (LIGO) has initiated a new field of astronomy by providing an alternate means of sensing the universe. The extreme sensitivity required to make such detections is achieved through exquisite isolation of all sensitive components of LIGO from non-gravitational-wave disturbances. Nonetheless, LIGO is still susceptible to a variety of instrumental and environmental sources of noise that contaminate the data. Of particular concern are noise features known as glitches, which are transient and non-Gaussian in their nature, and occur at a high enough rate so that accidental coincidence between the two LIGO detectors is non-negligible. Glitches come in a wide range of time-frequency-amplitude morphologies, with new morphologies appearing as the detector evolves. Since they can obscure or mimic true gravitational-wave signals, a robust characterization of glitches is paramount in the effort to achieve the gravitational-wave detection rates that are predicted by the design sensitivity of LIGO. This proves a daunting task for members of the LIGO Scientific Collaboration alone due to the sheer amount of data. In this paper we describe an innovative project that combines crowdsourcing with machine learning to aid in the challenging task of categorizing all of the glitches recorded by the LIGO detectors. Through the Zooniverse platform, we engage and recruit volunteers from the public to categorize images of time-frequency representations of glitches into preidentified morphological classes and to discover new classes that appear as the detectors arXiv:1611.04596v2 [gr-qc]

We use a wide-field (0.9 deg 2 ) X-ray sample with optical and GALEX ultraviolet observations to measure the contribution of Active Galactic Nuclei (AGNs) to the ionizing flux as a function of redshift. Our analysis shows that the AGN contribution to the metagalactic ionizing background peaks at around z = 2. The measured values of the ionizing background from the AGNs are lower than previous estimates and confirm that ionization from AGNs is insufficient to maintain the observed ionization of the intergalactic medium (IGM) at z > 3. We show that only sources with broad lines in their optical spectra have detectable ionizing flux and that the ionizing flux seen in an AGN is not correlated with its X-ray color. We also use the GALEX observations of the GOODS-N region to place a 2σ upper limit of 0.008 on the average ionization fraction f ν (700Å)/f ν (1500Å) for 626 UV selected galaxies in the redshift range z = 0.9 − 1.4. We then use this limit to estimate an upper bound to the galaxy contribution in the redshift range z = 0 − 5. If the z ∼ 1.15 ionization fraction is appropriate for higher redshift galaxies, then contributions from the galaxy population are also too low to account for the IGM ionization at the highest redshifts (z > 4).