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We present a detailed characterization of the Ly α properties for 93 Ly α emitters (LAEs) at z ∼ 3.1 selected from the D1 field of the Canadaâ€"Franceâ€"Hawaii Telescope Legacy Survey, including 24 members of a massive protocluster. The median-stacked Ly α image shows an extended Ly α halo (LAH) surrounding the galaxy with the exponential scale length 4.9 ± 0.7 kpc, which accounts for roughly half of the total line flux. Accounting for the LAH contribution, the total Ly α escape fraction, f esc, is 40% ± 26%. Combining the data set with existing measurements, we find a dependence of f esc on the galaxy’s UV slope (β) and UV luminosity (L UV). The simultaneous use of both parameters allows prediction of f esc within 0.18 dex, a substantial improvement over 0.23 dex when only β is used. The correlation between f esc and E (B âˆ' V) suggests that Ly α photons undergo interstellar dust attenuation in a similar manner to continuum photons. Yet, Ly α transmission is typically higher than that expected for continuum photons at a similar wavelength by a factor, which depends on UV luminosity, up to 2 in the samples we studied. These results hint at complex geometries and physical conditions of the interstellar medium, which affect the Ly α transmission or production. Alternatively, the dust law may change with luminosity leading to an over- or underestimation of f esc. Finally, we report that protocluster LAEs tend to be bluer and more UV luminous than their field cousins, resulting in systematically higher f esc values. We speculate that it may be due to the widespread formation of young low-mass galaxies in dense gas-rich environments. [ABSTRACT FROM AUTHOR]

We present a deep LBT/LBC Uspec-band imaging survey (9 deg2) covering the NOAO Boötes field. A total of 14,485 Lyman break galaxies (LBGs) at z ~ 3 are selected, which are used to measure the rest-frame UV luminosity function (LF). The large sample size and survey area reduce the LF uncertainties due to Poisson statistics and cosmic variance by ⩾3 compared to previous studies. At the bright end, the LF shows excess power compared to the best-fit Schechter function, which can be attributed to the contribution of z ~ 3 quasars. We compute the rest-frame near-infrared LF and stellar mass function (SMF) of z ~ 3 LBGs based on the R-band and [4.5μm]-band flux relation. We investigate the evolution of the UV LFs and SMFs between z ~ 7 and z ~ 3, which supports a rising star formation history in the LBGs. We study the spatial correlation function of two bright LBG samples and estimate their average host halo mass. We find a tight relation between the host halo mass and the galaxy star formation rate (SFR), which follows the trend predicted by the baryonic accretion rate onto the halo, suggesting that the star formation in LBGs is fueled by baryonic accretion through the cosmic web. By comparing the SFRs with the total baryonic accretion rates, we find that cosmic star formation efficiency is about 5%-20% and it does not evolve significantly with redshift, halo mass, or galaxy luminosity. [ABSTRACT FROM AUTHOR]

We present Keck DEIMOS spectroscopic observations of the most UV-luminous star-forming galaxies at redshifts 3.2 < z < 4.6. Our sample, selected in the Boötes field of the NOAO Deep Wide-Field Survey, contains galaxies with luminosities of L" ≲ LUV ≲ 7L " and is one of the largest samples to date of the most UV-luminous galaxies at these redshifts. Our spectroscopic data confirm 41 candidates as star-forming galaxies at 3.2 < z < 4.6 and validate the relatively clean selection of the photometric candidates with a contamination rate of 11%-28%. We find that the fraction of Lyα emitting galaxies increases with decreasing UV luminosity. None of the 12 galaxies with MUV < -22 (i.e., LUV > 3L") exhibit strong Lyα emission. We find strong evidence of large-scale outflows, transporting the neutral/ionized gas in the interstellar medium away from the galaxy. Galaxies exhibiting both interstellar absorption and Lyα emission lines show a significant offset between the two features, with a relative velocity of 200-1150 km s-1. We find tentative evidence that this measure of the outflow velocity increases with UV luminosity and/or stellar mass. The luminosity- and mass-dependent outflow strengths suggest that the efficiency of feedback and enrichment of the surrounding medium depend on these galaxy parameters. We also stack the individual spectra to construct composite spectra of the absorption-line-only and Lyα-emitting subsets of the UV luminous galaxies at z ≃ 3.7. The composite spectra are very similar to those of lower-redshift and lower-luminosity Lyman break galaxy (LBG) samples, but with some subtle differences. Analyses of the composite spectra suggest that the UV luminous LBGs at z ≃ 3.7 may have a higher covering fraction of absorbing gas, and may be older (or have had more prolonged star formation histories) than their lower-redshift and lower-luminosity counterparts. In addition, we have discovered that five galaxies in the sample belong to a massive overdensity at z = 3.78. Finally, two galaxies each show two distinct sets of interstellar absorption features. The latter may be a sign of a final stage of major merger, or clumpy disk formation. These systems are not expected in our sample: their presence implies that the frequency of such sources among our luminous z ≃ 3.7 LBGs may be an order of magnitude higher than in lower-redshift and lower-luminosity samples. [ABSTRACT FROM AUTHOR]

Giant Lyα nebulae (or Lyα "blobs") are likely sites of ongoing massive galaxy formation, but the rarity of these powerful sources has made it difficult to form a coherent picture of their properties, ionization mechanisms, and space density. Systematic narrowband Lyα nebula surveys are ongoing, but the small redshift range covered and the observational expense limit the comoving volume that can be probed by even the largest of these surveys and pose a significant problem when searching for such rare sources. We have developed a systematic search technique designed to find large Lyα nebulae at 2 ... ȥ ... 3 within deep broadband imaging and have carried out a survey of the 9.4 deg² NOAO Deep Wide-Field Survey Boötes field. With a total survey comoving volume of ≈ 108 h70-3 Mpc³, this is the largest volume survey for Lyα nebulae ever undertaken. In this first paper in the series, we present the details of the survey design and a systematically selected sample of 79 candidates, which includes one previously discovered Lyα nebula. [ABSTRACT FROM AUTHOR]

The Spitzer Space Telescope has identified a population of ultraluminous infrared galaxies (ULIRGs) at z ~ 2 that may play an important role in the evolution of massive galaxies. We measure the stellar masses (M∗) of two populations of Spitzer-selected ULIRGs that have extremely red R - [24] colors (dust-obscured galaxies, or DOGs) and compare our results with submillimeter-selected galaxies (SMGs). One set of 39 DOGs has a local maximum in their mid-infrared (mid-IR) spectral energy distribution (SED) at rest frame 1.6 µm associated with stellar emission ("bump DOGs"), while the other set of 51 DOGs have power-law mid-IR SEDs that are typical of obscured active galactic nuclei ("power-law DOGs"). We measure M∗ by applying Charlot & Bruzual stellar population synthesis models to broadband photometry in the rest-frame ultraviolet, optical, and near-infrared of each of these populations. Assuming a simple stellar population and a Chabrier initial mass function, we find that power-law DOGs and bump DOGs are on average a factor of 2 and 1.5 more massive than SMGs, respectively (median and inter-quartile M∗ values for SMGs, bump DOGs, and power-law DOGs are log(M∗/M⊙) = Due to image rights restrictions, multiple line equation(s) cannot be graphically displayed., and Due to image rights restrictions, multiple line equation(s) cannot be graphically displayed. respectively). More realistic star formation histories drawn from two competing theories for the nature of ULIRGs at z ~ 2 (major merger versus smooth accretion) can increase these mass estimates by up to 0.5 dex. A comparison of our stellar masses with the instantaneous star formation rate (SFR) in these z ~ 2 ULIRGs provides a preliminary indication supporting high SFRs for a given M∗, a situation that arises more naturally in major mergers than in smooth accretion-powered systems. [ABSTRACT FROM AUTHOR]

We investigate the average physical properties and star formation histories (SFHs) of the most UV-luminous star- forming galaxies at z ~ 3.7. Our results are based on the average spectral energy distributions (SEDs), constructed from stacked optical-to-infrared photometry, of a sample of the 1913 most UV-luminous star-forming galaxies found in 5.3 deg2 of the NOAO Deep Wide-Field Survey. We find that the shape of the average SED in the rest optical and infrared is fairly constant with UV luminosity, i.e., more UV-luminous galaxies are, on average, also more luminous at longer wavelengths. In the rest UV, however, the spectral slope β (≅dlogFλ/dlogλ; measured at 0.13 μm <λrest < 0.28μm) rises steeply with the median UV luminosity from -1.8 at L ≈ L* to -1.2 (L ~ 4-5L*). We use population synthesis analyses to derive their average physical properties and find that (I) LUV and thus star formation rates (SFRs) scale closely with stellar mass such that more UV-luminous galaxies are also more massive, (2) the median ages indicate that the stellar populations are relatively young (200-400 Myr) and show little correlation with UV luminosity, and (3) more UV-luminous galaxies are dustier than their less- luminous counterparts, such that L ≈ 4-5L* galaxies are extincted up to A(1600) = 2 mag while L ≈ L* galaxies have A(1600) = 0.7-1.5 mag. We argue that the average SFHs of UV-luminous galaxies are better described by models in which SFR increases with time in order to simultaneously reproduce the tight correlation between the UV-derived SFR and stellar mass and their universally young ages. We demonstrate the potential of measurements of the SFR-M* relation at multiple redshifts to discriminate between simple models of SFHs. Finally, we discuss the fate of these UV-brightest galaxies in the next 1-2 Gyr and their possible connection to the most massive galaxies at z ~ 2. [ABSTRACT FROM AUTHOR]

We present a physical model for the origin of dust-obscured galaxies (DOGs), a class of high-redshift ultraluminous infrared galaxies (ULIRGs) selected at 24 μm which are particularly optically faint . By combining N-body/smoothed particle hydrodynamic simulations of high-redshift galaxy evolution with 3D polychromatic dust radiative transfer models, we find that luminous DOGs (with mJy at ) are well modelled as extreme gas-rich mergers in massive haloes, with elevated star formation rates (SFR; ) and/or significant active galactic nuclei (AGN) growth , whereas less luminous DOGs are more diverse in nature. At final coalescence, merger-driven DOGs transition from being starburst dominated to AGN dominated, evolving from a ‘bump’ to a power-law (PL) shaped mid-IR (Infrared Array Camera, IRAC) spectral energy distribution (SED). After the DOG phase, the galaxy settles back to exhibiting a ‘bump’ SED with bluer colours and lower SFRs. While canonically PL galaxies are associated with being AGN dominated, we find that the PL mid-IR SED can owe both to direct AGN contribution and to a heavily dust obscured stellar bump at times that the galaxy is starburst dominated. Thus, PL galaxies can be either starburst or AGN dominated. Less luminous DOGs can be well-represented either by mergers or by massive secularly evolving gas-rich disc galaxies (with ). By utilizing similar models as those employed in the submillimetre galaxy (SMG) formation study of Narayanan et al., we investigate the connection between DOGs and SMGs. We find that the most heavily star-forming merger-driven DOGs can be selected as submillimetre galaxies, while both merger-driven and secularly evolving DOGs typically satisfy the BzK selection criteria. The model SEDs from the simulated galaxies match observed data reasonably well, though Mrk 231 and Arp 220 templates provide worse matches. Our models provide testable predictions of the physical masses, dust temperatures, CO linewidths and location on the relation of DOGs. Finally, we provide public SED templates derived from these simulations. [ABSTRACT FROM AUTHOR]

We use spatially extended measurements of Lyα as well as less optically thick emission lines from an ≈80 kpc Lyα nebula at z ≈ 1.67 to assess the role of resonant scattering and to disentangle kinematic signatures from Lyα radiative transfer effects. We find that the Lyα, C IV, He II, and C III] emission lines all tell a similar story in this system, and that the kinematics are broadly consistent with large-scale rotation. First, the observed surface brightness profiles are similar in extent in all four lines, strongly favoring a picture in which the Lyα photons are produced in situ instead of being resonantly scattered from a central source. Second, we see low kinematic offsets between Lyα and the less optically thick He II line (∼100-200 km s–1), providing further support for the argument that the Lyα and other emission lines are all being produced within the spatially extended gas. Finally, the full velocity field of the system shows coherent velocity shear in all emission lines: ≈500 km s–1 over the central ≈50 kpc of the nebula. The kinematic profiles are broadly consistent with large-scale rotation in a gas disk that is at least partially stable against collapse. These observations suggest that the Lyα nebula represents accreting material that is illuminated by an offset, hidden active galactic nucleus or distributed star formation, and that is undergoing rotation in a clumpy and turbulent gas disk. With an implied mass of M(11M☼, this system may represent the early formation of a large Milky Way mass galaxy or galaxy group. [ABSTRACT FROM AUTHOR]

We present clustering measurements and halo masses of star-forming galaxies at 0.2 < z < 1.0. After excluding active galactic nuclei (AGNs), we construct a sample of 22,553 24 μm sources selected from 8.42 deg2 of the Spitzer MIPS AGN and Galaxy Evolution Survey of Boötes. Mid-infrared imaging allows us to observe galaxies with the highest star formation rates (SFRs), less biased by dust obscuration afflicting the optical bands. We find that the galaxies with the highest SFRs have optical colors that are redder than typical blue cloud galaxies, with many residing within the green valley. At z > 0.4 our sample is dominated by luminous infrared galaxies (LIRGs, LTIR > 1011L☼) and is composed entirely of LIRGs and ultraluminous infrared galaxies (ULIRGs, LTIR > 1012L☼) at z > 0.6. We observe weak clustering of r0 ≈ 3-6 h–1 Mpc for almost all of our star-forming samples. We find that the clustering and halo mass depend on LTIR at all redshifts, where galaxies with higher LTIR (hence higher SFRs) have stronger clustering. Galaxies with the highest SFRs at each redshift typically reside within dark matter halos of Mhalo ≈ 1012.9h–1M☼. This is consistent with a transitional halo mass, above which star formation is largely truncated, although we cannot exclude that ULIRGs reside within higher mass halos. By modeling the clustering evolution of halos, we connect our star-forming galaxy samples to their local descendants. Most star-forming galaxies at z < 1.0 are the progenitors of L ≲ 2.5 L* blue galaxies in the local universe, but star-forming galaxies with the highest SFRs (LTIR ≳ 1011.7L☼) at 0.6 < z < 1.0 are the progenitors of early-type galaxies in denser group environments. [ABSTRACT FROM AUTHOR]

We report the discovery of an IR-selected galaxy cluster in the IRAC Distant Cluster Survey (IDCS). New data from the Hubble Space Telescope spectroscopically confirm IDCS J1433.2+3306 at z = 1.89 with robust spectroscopic redshifts for seven members, two of which are based on the 4000 Å break. Detected emission lines such as [O II] and Hβ indicate star formation rates of ≳20 M☼ yr–1 for three galaxies within a 500 kpc projected radius of the cluster center. The cluster exhibits a red sequence with a scatter and color indicative of a formation redshift zf ≳ 3.5. The stellar age of the early-type galaxy population is approximately consistent with those of clusters at lower redshift (1

Detailed analysis of the substructure of Lyα nebulae can put important constraints on the physical mechanisms at work and the properties of galaxies forming within them. Using high-resolution Hubble Space Telescope (HST) imaging of a Lyα nebula at z ≈ 2.656, we have taken a census of the compact galaxies in the vicinity, used optical/near-infrared colors to select system members, and put constraints on the morphology of the spatially extended emission. The system is characterized by (1) a population of compact, low-luminosity (∼0.1 L*) sources—17 primarily young, small (Re ≈ 1-2 kpc), disky galaxies including an obscured active galactic nucleus—that are all substantially offset (≳20 kpc) from the line-emitting nebula; (2) the lack of a central galaxy at or near the peak of the Lyα emission; and (3) several nearly coincident, spatially extended emission components—Lyα, He II, and UV continuum—that are extremely smooth. These morphological findings are difficult to reconcile with theoretical models that invoke outflows, cold flows, or resonant scattering, suggesting that while all of these physical phenomena may be occurring, they are not sufficient to explain the powering and large extent of Lyα nebulae. In addition, although the compact galaxies within the system are irrelevant as power sources, the region is significantly overdense relative to the field galaxy population (by at least a factor of four). These observations provide the first estimate of the luminosity function of galaxies within an individual Lyα nebula system and suggest that large Lyα nebulae may be the seeds of galaxy groups or low-mass clusters. [ABSTRACT FROM AUTHOR]