ABSTRACT A key obstacle to developing a satisfying theory of galaxy evolution is the difficulty in extending analytic descriptions of early structure formation into full non-linearity, the regime in which galaxy growth occurs. Extant techniques, though powerful, are based on approximate numerical methods whose Monte Carlo-like nature hinders intuition building. Here, we develop a new solution to this problem and its empirical validation. We first derive closed-form analytic expectations for the evolution of fixed percentiles in the real-space cosmic density distribution, averaged over representative volumes observers can track cross-sectionally. Using the Lagrangian forms of the fluid equations, we show that percentiles in δ – the density relative to the median – should grow as $\delta (t)\propto \delta _{0}^{\alpha }\, t^{\beta }$, where α ≡ 2 and β ≡ 2 for Newtonian gravity at epochs after the overdensities transitioned to non-linear growth. We then use 9.5 square degress of Carnegie-Spitzer-IMACS Redshift Survey data to map galaxy environmental densities over 0.2 < z < 1.5 (∼7 Gyr) and infer α = 1.98 ± 0.04 and β = 2.01 ± 0.11 – consistent with our analytic prediction. These findings – enabled by swapping the Eulerian domain of most work on density growth for a Lagrangian approach to real-space volumetric averages – provide some of the strongest evidence that a lognormal distribution of early density fluctuations indeed decoupled from cosmic expansion to grow through gravitational accretion. They also comprise the first exact, analytic description of the non-linear growth of structure extensible to (arbitrarily) low redshift. We hope these results open the door to new modelling of, and insight-building into, galaxy growth and its diversity in cosmological contexts.

We present the results of a systematic search for Ly alpha emitters (LAEs) at 6 less than or similar to z less than or similar to 7.6 using the HST WFC3 Infrared Spectroscopic Parallel (WISP) Survey. Our total volume over this redshift range is similar to 8 x 10(5) Mpc(3), comparable to many of the narrowband surveys despite their larger area coverage. We find two LAEs at z = 6.38 and 6.44 with line luminosities of L-Lya similar to 4.7 x 10(43) erg s(-1), putting them among the brightest LAEs discovered at these redshifts. Taking advantage of the broad spectral coverage of WISP, we are able to rule out almost all lower-redshift contaminants. The WISP LAEs have a high number density of 7.7 x 10(-6) Mpc (3). We argue that the LAEs reside in megaparsec-scale ionized bubbles that allow the Ly alpha photons to redshift out of resonance before encountering the neutral intergalactic medium. We discuss possible ionizing sources and conclude that the observed LAEs alone are not sufficient to ionize the bubbles.

We build a set of composite galaxy SEDs by de-redshifting and scaling multi-wavelength photometry from galaxies in the ZFOURGE survey, covering the CDFS, COSMOS, and UDS fields. From a sample of 4000 Ks−band selected galaxies, we create 38 composite galaxy SEDs that yield continuous low-resolution spectra (R ∼ 45) over the range 0.1-4 μm. Additionally, we include far infrared photometry from the Spitzer Space Telescope and the Herschel Space Observatory to characterize the infrared properties of our diverse set of composite SEDs. From these composite SEDs we analyze the rest-frame UV J colors, as well as the ratio of IR to UV light (IRX) and the UV slope (β ) in the IRX−β dust relation at 1 < z < 3. While blue star-forming composite SEDs show IRX and β values consistent with local relations, dusty star-forming composite SEDs are offset above the local IRX−β relations by as much as 0.5 dex, i.e., dusty star-forming galaxies have more UV flux (are bluer). We measure a tight linear relation between rest-frame UV J colors and dust attenuation for star-forming composites, providing a direct method for estimating dust content from either (U −V ) or (V − J) rest-frame colors for galaxies at intermediate redshifts.

ABSTRACT The FourStar galaxy evolution survey (ZFOURGE) is a 45 night legacy program with the FourStar near-infrared camera on Magellan and one of the most sensitive surveys to date. ZFOURGE covers a total of 400 arcmin2 in cosmic fields CDFS, COSMOS and UDS, overlapping CANDELS. We present photometric catalogs comprising >70,000 galaxies, selected from ultradeep K s -band detection images (25.5–26.5 AB mag, 5σ, total), and >80% complete to K s < 25.3–25.9 AB. We use 5 near-IR medium-bandwidth filters (J 1, J 2, J 3, H s , H l ) as well as broad-band K s at 1.05–2.16 μm to 25–26 AB at a seeing of ∼0.″5. Each field has ancillary imaging in 26–40 filters at 0.3–8 μm. We derive photometric redshifts and stellar population properties. Comparing with spectroscopic redshifts indicates a photometric redshift uncertainty σ z = 0.010, 0.009, and 0.011 in CDFS, COSMOS, and UDS. As spectroscopic samples are often biased toward bright and blue sources, we also inspect the photometric redshift differences between close pairs of galaxies, finding σ z,pairs = 0.01–0.02 at 1 < z < 2.5. We quantify how σ z,pairs depends on redshift, magnitude, spectral energy distribution type, and the inclusion of FourStar medium bands. σ z,pairs is smallest for bright, blue star-forming samples, while red star-forming galaxies have the worst σ z,pairs. Including FourStar medium bands reduces σ z,pairs by 50% at 1.5 < z < 2.5. We calculate star formation rates (SFRs) based on ultraviolet and ultradeep far-IR Spitzer/MIPS and Herschel/PACS data. We derive rest-frame U − V and V − J colors, and illustrate how these correlate with specific SFR and dust emission to z = 3.5. We confirm the existence of quiescent galaxies at z ∼ 3, demonstrating their SFRs are suppressed by > ×15.

ABSTRACT We present a compilation of UBVRIz light curves of 51 type II supernovae discovered during the course of four different surveys during 1986–2003: the Cerro Tololo Supernova Survey, the Calán/Tololo Supernova Program (C&T), the Supernova Optical and Infrared Survey (SOIRS), and the Carnegie Type II Supernova Survey (CATS). The photometry is based on template-subtracted images to eliminate any potential host galaxy light contamination, and calibrated from foreground stars. This work presents these photometric data, studies the color evolution using different bands, and explores the relation between the magnitude at maximum brightness and the brightness decline parameter (s) from maximum light through the end of the recombination phase. This parameter is found to be shallower for redder bands and appears to have the best correlation in the B band. In addition, it also correlates with the plateau duration, being shorter (longer) for larger (smaller) s values.

We present coarse but robust star-formation histories (SFHs) derived from spectrophotometric data of the Carnegie-Spitzer-IMACS Survey, for 22,494 galaxies at 0.3 < z < 0.9 with stellar masses of 10(9)M(circle dot) to 10(12)M(circle dot). Our study moves beyond "average" SFHs and distribution functions of specific star-formation rates (sSFRs) to individually measured SFHs for tens of thousands of galaxies. By comparing star-formation rates (SFRs) with timescales of 10(10), 10(9), and 10(8) years, we find a wide diversity of SFHs: "old galaxies" that formed most or all of their stars early,. galaxies that formed stars with declining or constant SFRs over a Hubble time, and genuinely "young galaxies" that formed most of their stars since z = 1 This sequence is one of decreasing stellar mass, but remarkably, each type is found over a mass range of a factor of 10. Conversely, galaxies at any given mass follow a wide range of SFHs, leading us to conclude that. (1) halo mass does not uniquely determine SFHs,. (2) there is no "typical" evolutionary track, and (3) "abundance matching" has limitations as a tool for inferring physics. Our observations imply that SFHs are set at an early epoch, and that-for most galaxies-the decline and cessation of star formation occurs over a Hubble time, without distinct "quenching" events. SFH diversity is inconsistent with models where galaxy mass, at any given epoch, grows simply along relations between SFR and stellar mass, but is consistent with a two-parameter lognormal form, lending credence to this model from a new and independent perspective.

We build a set of composite galaxy spectral energy distributions (SEDs) by de-redshifting and scaling multi-wavelength photometry from galaxies in the ZFOURGE survey, covering the CDFS, COSMOS, and UDS fields. From a sample of similar to 4000 K-s-band selected galaxies, we define 38 composite galaxy SEDs that yield continuous low-resolution spectra (R similar to 45) over the rest-frame range 0.1-4 mu m. Additionally, we include far infrared photometry from the Spitzer Space Telescope and the Herschel Space Observatory to characterize the infrared properties of our diverse set of composite SEDs. From these composite SEDs we analyze the rest-frame UVJ colors, as well as the ratio of IR to UV light (IRX) and the UV slope (beta) in the IRX-beta dust relation at 1 < z < 3. Blue star-forming composite SEDs show IRX and beta values consistent with local relations; dusty star-forming galaxies have considerable scatter, as found for local IR bright sources, but on average appear bluer than expected for their IR fluxes. We measure a tight linear relation between rest-frame UVJ colors and dust attenuation for star-forming composites, providing a direct method for estimating dust content from either (U - V) or (V - J) rest-frame colors for star-forming galaxies at intermediate redshifts.

We report the first direct and robust measurement of the faint-end slope of the Ly alpha emitter (LAE) luminosity function (LF) at z = 5.7. Candidate LAEs from a low-spectral-resolution blind search with IMACS on Magellan-Baade were targeted at higher resolution to distinguish high-redshift LAEs from foreground galaxies. All but 2 of our 42 single-emission-line systems have flux F < 2.0x10(-17) ergs s(-1) cm(-2), making these the faintest emission-lines observed for a z = 5.7 sample with known completeness, an essential property for determining the faint end slope of the LAE LF. We find 13 LAEs as compared to 29 foreground galaxies, in very good agreement with the modeled foreground counts predicted in Dressler et al. that had been used to estimate a faint-end slope of alpha = -2.0 for the LAE LF. A 32% LAE fraction, LAE/(LAE+foreground) within the flux interval F = 2-20 x 10(-18) ergs s(-1) cm(-2) constrains the faint end slope of the LF to -2.35 < alpha < -1.95 (1 sigma). We show how this steep LF should provide, to the limit of our observations, M-UV similar to -16, more than 20% of the flux necessary to maintain ionization at z = 5.7, with a factor of 10 extrapolation in flux reaching more than 50%. This is in addition to the comparable contribution by brighter Lyman Break Galaxies M-UV less than or similar to -18. We suggest that this bodes well for a sufficient supply of Lyman continuum photons by similar, low-mass star-forming galaxies within the reionization epoch at z approximate to 7, only 250 Myr earlier.

We present a spectroscopic analysis of the H-alpha profiles of hydrogen-rich type II supernovae. A total of 52 type II supernovae having well sampled optical light curves and spectral sequences were analyzed. Concentrating on the H-alpha P-Cygni profile we measure its velocity from the FWHM of emission and the ratio of absorption to emission (a/e) at a common epoch at the start of the recombination phase, and search for correlations between these spectral parameters and photometric properties of the V-band light curves. Testing the strength of various correlations we find that a/e appears to be the dominant spectral parameter in terms of describing the diversity in our measured supernova properties. It is found that supernovae with smaller a/e have higher H-alpha velocities, more rapidly declining light curves from maximum, during the plateau and radioactive tail phase, are brighter at maximum light and have shorter optically thick phase durations. We discuss possible explanations of these results in terms of physical properties of type II supernovae, speculating that the most likely parameters which influence the morphologies of H-alpha profiles are the mass and density profile of the hydrogen envelope, together with additional emission components due to circumstellar interaction.

We present results from near-infrared spectroscopy of 26 emission-line galaxies at z 2 obtained with the FIRE spectrometer on the Magellan Baade telescope. The sample was selected from the WISP survey, which uses the near-infrared grism of the Hubble Space Telescope Wide Field Camera 3 to detect emission-line galaxies over 0.3 < z < 2.3. Our FIRE follow-up spectroscopy (R 5000) over 1.0-2.5 micron permits detailed measurements of physical properties of the z 2 emission-line galaxies. Dust-corrected star formation rates for the sample range from 5-100 M_sun yr-1. We derive a median metallicity for the sample of 0.45 Z_sun, and the estimated stellar masses range from 10^8.5 - 10^9.5 M_sun. The average ionization parameters measured for the sample are typically much higher than what is found for local star-forming galaxies. We derive composite spectra from the FIRE sample, from which we infer typical nebular electron densities of 100-400 cm^-3. Based on the location of the galaxies and composite spectra on BPT diagrams, we do not find evidence for significant AGN activity in the sample. Most of the galaxies as well as the composites are offset in the BPT diagram toward higher [O III]/H-beta at a given [N II]/H-alpha, in agreement with other observations of z > 1 star-forming galaxies, but composite spectra derived from the sample do not show an appreciable offset from the local star-forming sequence on the [O III]/H-beta versus [S II]/H-alpha diagram. We infer a high nitrogen-to-oxygen abundance ratio from the composite spectrum, which may contribute to the offset of the high-redshift galaxies from the local star-forming sequence in the [O III]/H-beta versus [N II]/H-alpha diagram. We speculate that the elevated nitrogen abundance could result from substantial numbers of Wolf-Rayet stars in starbursting galaxies at z 2. (Abridged)

Near infrared slitless spectroscopy with the Wide Field Camera 3, on board the Hubble Space Telescope, offers a unique opportunity to study low-mass galaxy populations at high redshift (z similar to 1-2). While most high-z surveys are biased toward massive galaxies, we are able to select sources via their emission lines that have very faint continua. We investigate the star formation rate (SFR)-stellar mass (M-star) relation for about 1000 emission line galaxies identified over a wide redshift range of 0.3 less than or similar to z less than or similar to 2.3. We use the Ha emission as an accurate SFR indicator and correct the broadband photometry for the strong nebular contribution to derive accurate stellar masses down to M-star similar to 10(7) M-circle dot. We focus here on a subsample of galaxies that show extremely strong emission lines (EELGs) with rest-frame equivalent widths ranging from 200 to 1500 A. This population consists of outliers to the normal SFR-M-star sequence with much higher specific SFRs (> 10 Gyr(-1)). While on-sequence galaxies follow continuous star formation processes, EELGs are thought to be caught during an extreme burst of star formation that can double their stellar mass in a period of less than 100 Myr. The contribution of the starburst population to the total star formation density appears to be larger than what has been reported for more massive galaxies in previous studies. In the complete mass range 8.2 < log(M-star/M-circle dot)< 10 and a SFR lower completeness limit of about 2 M-circle dot yr(-1) (10 M-circle dot yr-1) at z similar to 1 (z similar to 2), we find that starbursts having EWrest(H alpha) > 300, 200, and 100 angstrom contribute up to similar to 13%, 18%, and 34%, respectively, to the total SFR of emission-line-selected sample at z similar to 1-2. The comparison with samples of massive galaxies shows an increase in the contribution of starbursts toward lower masses.

Our understanding of the redshift z > 3 galaxy population relies largely on samples selected using the popular "dropout" technique, typically consisting of UV-bright galaxies with blue colors and prominent Lyman breaks. As it is currently unknown if these galaxies are representative of the massive galaxy population, we here use the FOURSTAR Galaxy Evolution (ZFOURGE) survey to create a stellar mass-limited sample at z = 3-4. Uniquely, ZFOURGE uses deep near-infrared medium-bandwidth filters to derive accurate photometric redshifts and stellar population properties. The mass-complete sample consists of 57 galaxies with log M > 10.6, reaching below M* at z = 3-4. On average, the massive z = 3-4 galaxies are extremely faint in the observed optical with median = R-tot(AB) = 27.48 +/- 0.41 (rest-frame M-1700 = 18.05 +/- 0.37). They lie far below the UV luminosity stellar mass relation for Lyman break galaxies and are about similar to 100x fainter at the same mass. The massive galaxies are red (R - K-s (AB) = 3.9 +/- 0.2; rest-frame UV-slope beta = -0.2 +/- 0.3) likely from dust or old stellar ages. We classify the galaxy spectral energy distributions by their rest-frame U-V and V-J colors and find a diverse population: 46(-6-17)(+6+10)% of the massive galaxies are quiescent, 40(-6-5)(+6+7)% are dusty star-forming galaxies, and only 14(-3-4)(+3+10)% resemble luminous blue star-forming Lyman break galaxies. This study clearly demonstrates an inherent diversity among massive galaxies at higher redshift than previously known. Furthermore, we uncover a reservoir of dusty star-forming galaxies with 4x lower specific star-formation rates compared to submillimeter-selected starbursts at z > 3. With 5x higher numbers, the dusty galaxies may represent a more typical mode of star formation compared to submillimeter-bright starbursts.