We report BV(RI)(C) CCD photometric data for a group of seven Cepheid variables in the young, rich cluster NGC 1866 in the Large Magellanic Cloud. The photometry was obtained as part of a program to determine accurate distances to these Cepheids by means of the infrared surface brightness technique and to improve the LMC Cepheid database for constructing Cepheid P-L and P-L-C relations. Using the new data together with data from the literature, we have determined improved periods for all variables. For five fundamental mode pulsators, the light curves are now of excellent quality and will lead to accurate distance and radius determinations once complete infrared light curves and radial velocity curves for these variables become available.

We present the discovery and follow-up observations of the afterglow of the gamma-ray burst GRB 011121 and its associated supernova SN 2001ke. Images were obtained with the Optical Gravitational Lensing Experiment 1.3 m telescope in BVRI passbands, starting 10.3 hr after the burst. The temporal analysis of our early data indicates a steep decay, independent of wavelength, with F-nu proportional to t(-1.72+/-0.05). There is no evidence for a break in the light curve earlier than 2.5 days after the burst. The spectral energy distribution determined from the early broadband photometry is a power law with Fnu proportional to nu(-0.66+/-0.13) after correcting for a large reddening. Spectra obtained with the Magellan 6.5 m Baade telescope reveal narrow emission lines from the host galaxy that provide a redshift of z = 0.362 +/- 0.001 to the GRB. We also present late R - and J-band observations of the afterglow similar to7-17 days after the burst. The late-time photometry shows a large deviation from the initial decline, and our data combined with Hubble Space Telescope photometry provide strong evidence for a supernova peaking about 12 rest-frame days after the GRB. The first spectrum ever obtained of a GRB supernova at cosmological distance revealed a blue continuum. SN 2001ke was more blue near maximum than SN 1998bw and faded more quickly, which demonstrates that a range of properties are possible in supernovae that generate GRBs. The blue color is consistent with a supernova interacting with circumstellar gas, and this progenitor wind is also evident in the optical afterglow. This is the best evidence to date that classical, long GRBs are generated by core-collapse supernovae.

We present deep imaging and optical spectroscopy of the newly discovered Red-Sequence Cluster Survey cluster RCS 043938 - 2904.9. This cluster, drawn from an extensive preliminary list, was selected for detailed study on the basis of its apparent optical richness. Spectroscopy of 11 members places the cluster at z = 0.951 +/- 0.006 and confirms the photometric redshift estimate from the (R-z) color-magnitude diagram. Analysis of the infrared imaging data demonstrates that the cluster is extremely rich, with excess counts in the K-s band exceeding the expected background counts by 9 sigma. The properties of the galaxies in RCS 043938 - 2904.9 are consistent with those seen in other clusters at similar redshifts. Specifically, the red-sequence color, slope, and scatter and the size-magnitude relation of these galaxies are all consistent with that seen in the few other known high-redshift clusters and indeed are consistent with appropriately evolved properties of local cluster galaxies. The apparent consistency of these systems implies that the rich high-redshift RCS clusters are directly comparable to the few other systems known at, most of which have been selected on the basis of X-ray emission.

We present a first cosmological analysis of a refined cluster catalog from the Red-Sequence Cluster Survey ( RCS). The input cluster sample is derived from the deepest 72.07 deg(2) of the RCS images, which probe to the highest redshift and lowest mass limits. The catalog contains 956 clusters over 0.35 < z < 0.95, limited by cluster richness and richness error. The calibration of the survey images has been extensively cross-checked against publicly available Sloan Digital Sky Survey imaging, and the cluster redshifts and richness that result from this well-calibrated subset of data are robust. We analyze the cluster sample via a general self-calibration technique. We fit simultaneously for the matter density, Omega(m), the normalization of the power spectrum, sigma(8), and four parameters describing the calibration of cluster richness to mass, its evolution with redshift, and scatter in the mass-richness relation. The principal goal of this general analysis is to establish the consistency ( or lack thereof) between the fitted parameters ( both cosmological and cluster mass observables) and available results on both from independent measures. From an unconstrained analysis, the derived values of Omega(m) and sigma(8) are 0.31(-0.10)(+0. 11) and 0.67(-0.13)(+0: 18) , respectively. An analysis including Gaussian priors on the slope and zero point of the mass-richness relation gives very similar results: 0.30(-0.11)(+0.12) and 0.70(-0.15)(+0.27) . Both analyses are in acceptable agreement with the current literature. The derived parameters describing the mass- richness relation in the unconstrained fit are also eminently reasonable and in good agreement with existing follow- up data on both the RCS-1 and other cluster samples. Our results directly demonstrate that future surveys ( optical and otherwise), with much larger samples of clusters, can give constraints competitive with other probes of cosmology.

Context. Most sub-mm emission line studies of galaxies to date have targeted sources with known redshifts where the frequencies of the lines are well constrained. Recent blind line scans circumvent the spectroscopic redshift requirement, which could represent a selection bias.

We spectroscopically confirmed two narrowband-selected redshift 7.0 Ly alpha galaxies and studied their rest-frame UV spectra. The Ly alpha and other UV nebular lines are very useful to confirm the galactic redshifts and diagnose the different mechanisms driving the ionizing emission. We observed two narrowband-selected z = 7.0 Ly alpha candidates in the LAGER Chandra Deep Field South (CDFS) field with IMACS at the Magellan telescope and confirmed they are Ly alpha emitters at z = 6.924 and 6.931. In one galaxy, we also obtained deep near-infrared (NIR) spectroscopy, which yields non-detections of the high-ionization UV nebular lines. We measured the upper limits of the ratios of C IV lambda 1548/Ly alpha, He II lambda 1640/Ly alpha, O III]lambda 1660/Ly alpha, and C III]lambda 1909/Ly alpha from the NIR spectra. These upper limits imply that the ionizing emission in this galaxy is dominated by normal star formation instead of an active galactic nucleus.

Context. Characterizing the number counts of faint (i.e., sub-mJy and especially sub-100 mu Jy), dusty star-forming galaxies is currently a challenge even for deep, high-resolution observations in the FIR-to-mm regime. They are predicted to account for approximately half of the total extragalactic background light at those wavelengths. Searching for dusty star-forming galaxies behind massive galaxy clusters benefits from strong lensing, enhancing their measured emission while increasing spatial resolution. Derived number counts depend, however, on mass reconstruction models that properly constrain these clusters.

Context. The Hubble Frontier Fields offer an exceptionally deep window into the high-redshift universe, covering a substantially larger area than the Hubble Ultra-Deep field at low magnification and probing 1-2 mag deeper in exceptional high-magnification regions. This unique parameter space, coupled with the exceptional multi-wavelength ancillary data, can facilitate for useful insights into distant galaxy populations. Aims. We aim to leverage Atacama Large Millimetre Array (ALMA) band 6 (approximate to 263 GHz) mosaics in the central portions of five Frontier Fields to characterize the infrared (IR) properties of 1582 ultraviolet (UV)-selected Lyman-Break Galaxies (LBGs) at redshifts of z similar to 2-8. We investigated individual and stacked fluxes and IR excess (IRX) values of the LBG sample as functions of stellar mass (M-& x22c6;), redshift, UV luminosity and slope beta, and lensing magnification. Methods. LBG samples were derived from color-selection and photometric redshift estimation with Hubble Space Telescope photometry. Spectral energy distributions -templates were fit to obtain luminosities, stellar masses, and star formation rates for the LBG candidates. We obtained individual IR flux and IRX estimates, as well as stacked averages, using both ALMA images and u-v visibilities. Results. Two (2) LBG candidates were individually detected above a significance of 4.1-sigma, while stacked samples of the remaining LBG candidates yielded no significant detections. We investigated our detections and upper limits in the context of the IRX-M-star and IRX-beta relations, probing at least one dex lower in stellar mass than past studies have done. Our upper limits exclude substantial portions of parameter space and they are sufficiently deep in a handful of cases to create mild tension with the typically assumed attenuation and consensus relations. We observe a clear and smooth trend between M-star and beta, which extends to low masses and blue (low) beta values, consistent with expectations from previous works.

We present our measurements of the Ha, [01111, and [OW luminosity functions as part of the Lyman Alpha Galaxies at Epoch of Reionization (LAGER) survey using our samples of 1577 z = 0.47 H a-, 3933 z = 0.93 [0 and 5367 z = 1,59 [0 u1 -selected emission line galaxies in a 3 deg2 single, CHO/Blanco DECam pointing of the COSMOS field, Our observations reach 50- depths of 8.2 x 10-18 erg s -I cm -2 and comoving volumes of (1-7) x 105 Mpc3 making our survey one of the deepest narrow -hand surveys. We select our emission line galaxies via spectroscopic confirmation, photometric redshifts, and colour-colour selections. We measure 316_'_;.`99the observed luminosity functions for each sample and find best fits of (p* = 10-- Mpc-3 and L* = 1041.72"a erg s -I for Ha, (/)* = 1 0-2.161i M c'1 and L* = 1041.38Z6 erg s-1 for [0111], and (/5* = 10 1.971,.i1041.66 'Mpc-3 and L* = erg s -I for [Oil], with a fixed to - 1.75, -1.6, and -1,3, respectively. An excess of bright >1042 erg s -I [0111] emitters is observed and may be due to active galactic nucleus (AGN) contamination, Corrections for dust attenuation are applied assuming Afp, = 1 mag. We also design our own empirical rest frame g - r calibration using SDSS DR12 data, test it against our z = 0,47 H a emitters with zCOSMOS 1D spectra, and calibrate it for (g - r) between -0.8 and 1.3 mag. Dust and AGNcorrected star formation rate densities (SERDs) are measured as logiopsFRAM(.; yr I Mpc-3) = - 1,63 + 0,04, -1.07 + 0,06, and -0.90 + 0.10 for H a, [0 in and [Ou], respectively. We find our [0 uf] and [0 RI samples fully trace cosmic star formation activity at their respective redshifts in comparison to multiwavelength SERDs, while the Ha sample traces =70 per cent of the total z = 0,47 SURD,