The Faint Infrared Grism Survey (FIGS) is a deep Hubble Space Telescope (HST) WFC3/IR (Wide Field Camera 3 Infrared) slitless spectroscopic survey of four deep fields. Two fields are located in the Great Observatories Origins Deep Survey-North (GOODS-N) area and two fields are located in the Great Observatories Origins Deep Survey-South (GOODS-S) area. One of the southern fields selected is the Hubble Ultra Deep Field. Each of these four fields were observed using the WFC3/G102 grism (0.8 mu m-1.15 mu m continuous coverage) with a total exposure time of 40 orbits (approximate to 100 kilo-seconds) per field. This reaches a 3 sigma continuum depth of approximate to 26 AB magnitudes and probes emission lines to similar to 10(-17) erg s(-1) cm(-2). This paper details the four FIGS fields and the overall observational strategy of the project. A detailed description of the Simulation Based Extraction (SBE) method used to extract and combine over 10,000 spectra of over 2000 distinct sources brighter than m(F105W) = 26.5 mag is provided. High fidelity simulations of the observations is shown to significantly improve the background subtraction process, the spectral contamination estimates, and the final flux calibration. This allows for the combination of multiple spectra to produce a final high quality, deep, 1D spectra for each object in the survey.

We present spectra of five ultra-diffuse galaxies (UDGs) in the vicinity of the Coma cluster obtained with the Multi-object Double Spectrograph on the Large Binocular Telescope. We confirm four of these as members of the cluster, quintupling the number of spectroscopically confirmed systems. Like the previously confirmed large (projected half-light radius > 4.6 kpc) UDG, DF44, the systems we targeted all have projected half-light radii > 2.9 kpc. As such, we spectroscopically confirm a population of physically large UDGs in the Coma cluster. The remaining UDG is located in the field, about 45 Mpc behind the cluster. We observe Balmer and Ca II H and K absorption lines in all of our UDG spectra. By comparing the stacked UDG spectrum against stellar population synthesis models, we conclude that, on average, these UDGs are composed of metal-poor stars ([Fe/H] less than or similar to -1.5). We also discover the first UDG with [O II] and [O III] emission lines within a clustered environment, demonstrating that not all cluster UDGs are devoid of gas and sources of ionizing radiation.

We report the results of a pilot program to use the Magellan/M2FS spectrograph to survey the galactic populations and internal kinematics of galaxy clusters. For this initial study, we present spectroscopic measurements for 223 quiescent galaxies observed along the line of sight of the galaxy cluster Abell 267 (z similar to 0.23). We develop a Bayesian method for modeling the integrated light from each galaxy as a simple stellar population, with free parameters that specify the redshift (v(los)/c) and characteristic age, metallicity ([Fe/H]), alpha-abundance ([alpha/Fe]), and internal velocity dispersion (sigma(int)) for individual galaxies. Parameter estimates derived from our 1.5 hr observation of A267 have median random errors of sigma(vlos) = 20 km s(-1), sigma(Age) = 1.2 Gyr, sigma([Fe/H]) = 0.11 dex, sigma([alpha/Fe]) = 0.07 dex, and sigma(sigma int) = 20 km s(-1). In a companion paper, we use these results to model the structure and internal kinematics of A267.

The Large Early Galaxy Census (LEGA-C-16) is a Public Spectroscopic Survey of similar to 3200 K-band selected galaxies at redshifts z. =. 0.6 - 1.0 with stellar masses M-* > 10(10) M-circle dot, conducted with VIMOS on ESO's Very Large Telescope. The survey is embedded in the COSMOS field (R.A. = 10h00; decl. = +2 deg). The 20 hr long integrations produce high-signal-to-noise ratio continuum spectra that reveal ages, metallicities and velocity dispersions of the stellar populations. LEGA-C's unique combination of sample size and depth will enable us for the first time to map the stellar content at large lookback time, across galaxies of different types and star formation activity. Observations started in 2014 December and are planned to be completed by mid 2018, with early data releases of the spectra and value-added products. In this paper we present the science case, the observing strategy, an overview of the data reduction process and data products, and a first look at the relationship between galaxy structure and spectral properties, as it existed 7 Gyr ago.

This overview paper describes the legacy prospect and discovery potential of the Dark Energy Survey (DES) beyond cosmological studies, illustrating it with examples from the DES early data. DES is using a wide-field camera (DECam) on the 4 m Blanco Telescope in Chile to image 5000 sq deg of the sky in five filters (grizY). By its completion, the survey is expected to have generated a catalogue of 300 million galaxies with photometric redshifts and 100 million stars. In addition, a time-domain survey search over 27 sq deg is expected to yield a sample of thousands of Type Ia supernovae and other transients. The main goals of DES are to characterize dark energy and dark matter, and to test alternative models of gravity; these goals will be pursued by studying large-scale structure, cluster counts, weak gravitational lensing and Type Ia supernovae. However, DES also provides a rich data set which allows us to study many other aspects of astrophysics. In this paper, we focus on additional science with DES, emphasizing areas where the survey makes a difference with respect to other current surveys. The paper illustrates, using early data (from 'Science Verification', and from the first, second and third seasons of observations), what DES can tell us about the Solar system, the Milky Way, galaxy evolution, quasars and other topics. In addition, we show that if the cosmological model is assumed to be I >+cold dark matter, then important astrophysics can be deduced from the primary DES probes. Highlights from DES early data include the discovery of 34 trans-Neptunian objects, 17 dwarf satellites of the Milky Way, one published z > 6 quasar (and more confirmed) and two published superluminous supernovae (and more confirmed).

Cosmological constraints from galaxy clusters rely on accurate measurements of the mass and internal structure of clusters. An important source of systematic uncertainty in cluster mass and structure measurements is the secure selection of background galaxies that are gravitationally lensed by clusters. This issue has been shown to be particular severe for faint blue galaxies. We therefore explore the selection of faint blue background galaxies, by reference to photometric redshift catalogues derived from the Cosmological Evolution Survey (COSMOS) and our own observations of massive galaxy clusters at z similar or equal to 0.2. We show that methods relying on photometric redshifts of galaxies in/behind clusters based on observations through five filters, and on deep 30-band COSMOS photometric redshifts are both inadequate to identify safely faint blue background galaxies with the same 1 per cent contamination level that we have achieved with red galaxies. This is due to the small number of filters used by the former, and absence of massive galaxy clusters at redshifts of interest in the latter. Nevertheless, our least contaminated blue galaxy sample yields stacked weak-lensing results consistent with our previously published results based on red galaxies, and we show that the stacked clustercentric number density profile of these faint blue galaxies is consistent with expectations from consideration of the lens magnification signal of the clusters. Indeed, the observed number density of blue background galaxies changes by similar to 10-30 per cent across the radial range over which other surveys assume it to be flat.

Many measurements in cosmology depend on the use of integrated distances or time, but. galaxies evolving passively on a timescale much longer than their age difference allow us to determine the expansion rate H(z) solely as a function of the redshift-time derivative dz/dt. These model-independent "cosmic chronometers" can therefore be powerful discriminators for testing different cosmologies. In previous applications, the available sources strongly disfavored models (such as Lambda CDM) predicting a variable acceleration, preferring instead a steady expansion rate over the redshift range 0 less than or similar to z less than or similar to 2. A more recent catalog of 30 objects appears to suggest non-steady expansion. In this paper, we show that such a result is entirely due to the inclusion of a high, locally inferred value of the Hubble constant H-0 as an additional datum in a set of otherwise pure cosmic-chronometer measurements. This H-0, however, is not the same as the background Hubble constant if the local expansion rate is influenced by a Hubble Bubble. Used on their own, the cosmic chronometers completely reverse this conclusion, favoring instead a constant expansion rate out to z similar to 2.

We continue to build support for the proposal to use H II galaxies (HIIGx) and giant extragalactic H II regions (GEHR) as standard candles to construct the Hubble diagram at redshifts beyond the current reach of Type Ia supernovae. Using a sample of 25 high-redshift HIIGx, 107 local HIIGx, and 24 GEHR, we confirm that the correlation between the emission -line luminosity and ionized -gas velocity dispersion is a viable luminosity indicator, and use it to test and compare the standard model Lambda CDM and the R-h = ct universe by optimizing the parameters in each cosmology using a maximization of the likelihood function. For the flat Lambda CDM model, the best fit is obtained with Omega(m) = 0.40(-0.09)(+0.09). However, statistical tools, such as the Akaike (AIC), Kullback (KIC) and Bayes (BIC) Information Criteria favour R-h = Ct over the standard model with a likelihood of approximate to 94.8-98.8 per cent versus only per cent. For wCDM (the version of ACDM with a dark -energy equation of state wde = Pde/Pde rather than was t WA = 1), a statistically acceptable fit is realized with Omega(m) = 0.221(-0.14)(+0.16) and wde = 0.511'0'21-5" which, however, are not fully consistent with their concordance values. In this case, wCDM has two more free parameters than R-h = Ct, and is penalized more heavily by these criteria. We find that R-h = Ct is strongly favoured over wCDM with a likelihood of approximate to 92.9-99.6 per cent versus only 0.4-7.1 per cent. The current HIIGx sample is already large enough for the BIC to rule out ACDM/wCDM in favour of R-h = Ct at a confidence level approaching 3 sigma.

We investigate the relation between gas and star formation in subgalactic regions, similar to 360. pc to similar to 1.5. kpc in size, within the nearby starburst dwarf NGC 4449, in order to separate the underlying relation from the effects of sampling at varying spatial scales. Dust and gas mass surface densities are derived by combining new observations at 1.1. mm, obtained with the AzTEC instrument on the Large Millimeter Telescope, with archival infrared images in the range 8-500 mu m from the Spitzer Space Telescope and the Herschel Space Observatory. We extend the dynamic range of our millimeter (and dust) maps at the faint end, using a correlation between the far-infrared/millimeter colors F(70)/F(1100) (and F(160)/F(1100)) and the mid-infrared color F(8)/F(24) that we establish for the first time for this and other galaxies. Supplementing our data with maps of the extinction-corrected star formation rate (SFR) surface density, we measure both the SFR-molecular gas and the SFR-total. gas relations in NGC 4449. We find that the SFR-molecular. gas relation is described by a power law with an exponent that decreases from similar to 1.5 to similar to 1.2 for increasing region size, while the exponent of the SFR-total. gas relation remains constant with a value of similar to 1.5 independent of region size. We attribute the molecular law behavior to the increasingly better sampling of the molecular cloud mass function at larger region sizes; conversely, the total gas law behavior likely results from the balance between the atomic and molecular gas phases achieved in regions of active star formation. Our results indicate a nonlinear relation between SFR and gas surface density in NGC 4449, similar to what is observed for galaxy samples.

A previous analysis of starburst-dominated HII galaxies and HII regions has demonstrated a statistically significant preference for the Friedmann-Robertson-Walker cosmology with zero active mass, known as the R-h = c(t) universe, over Lambda cold dark matter (Lambda CDM) and its related dark-matter parametrizations. In this paper, we employ a two-point diagnostic with these data to present a complementary statistical comparison of Rh = ct with Planck Lambda CDM. Our two-point diagnostic compares, in a pairwise fashion, the difference between the distance modulus measured at two redshifts with that predicted by each cosmology. Our results support the conclusion drawn by a previous comparative analysis demonstrating that Rh = ct is statistically preferred over Planck Lambda CDM. But we also find that the reported errors in the HII measurements may not be purely Gaussian, perhaps due to a partial contamination by non-Gaussian systematic effects. The use of HII galaxies and HII regions as standard candles may be improved even further with a better handling of the systematics in these sources.