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ABSTRACT Extragalactic studies have demonstrated that there is a moderately tight (≈0.3 dex) relationship between galaxy stellar mass (M⋆) and star formation rate (SFR) that holds for star-forming galaxies at M⋆ ∼ 3 × 108–1011 M⊙, i.e. the ‘star formation main sequence’. However, it has yet to be determined whether such a relationship extends to even lower mass galaxies, particularly at intermediate or higher redshifts. We present new results using observations for 714 narrow-band H α-selected galaxies with stellar masses between 106 and 1010 M⊙ (average of 108.2 M⊙) at z ≈ 0.07–0.5. These galaxies have sensitive ultraviolet (UV) to near-infrared photometric measurements and optical spectroscopy. The latter allows us to correct our H α SFRs for dust attenuation using Balmer decrements. Our study reveals that: (1) for low-SFR galaxies, our H α SFRs systematically underpredict compared to far-UV measurements, consistent with other studies; (2) at a given stellar mass (≈108 M⊙), log (specific SFR) evolves as A log (1 + z) with A = 5.26 ± 0.75, and on average, specific SFR increases with decreasing stellar mass; (3) the SFR–M⋆ relation holds for galaxies down to ∼106 M⊙ (∼1.5 dex below previous studies), and over lookback times of up to 5 Gyr, follows a redshift-dependent relation of log (SFR) ∝ α log (M⋆/M⊙) + β z with α = 0.60 ± 0.01 and β = 1.86 ± 0.07; and (4) the observed dispersion in the SFR–M⋆ relation at low stellar masses is ≈0.3 dex. Accounting for survey selection effects using simulated galaxies, we estimate that the true dispersion is ≈0.5 dex.

Digitalization brought about by the Covid-19 pandemic has revolutionized many aspects of businesses, magnifying their opportunities and challenges in the market. The global retail sector is no exception. Several changes have transpired in the sector, such as increased preference for online shopping and changes in supply chains and logistics. The purpose of this study is to examine how digital advancement has taken place in the retail sector of Dubai and how it has affected service delivery. To this end, a survey of 94 retailers from around Dubai was conducted using a structured, close-ended questionnaire. The data analysed on SPSS software showed that disruptive technologies like internet of things, artificial intelligence, automation, and big data analytics have a role in changing business functioning. With the implementation of practices like on-demand delivery, tracking product location, personalized services, controlled delivery system, and reduction in transmissible disease exposure the retail industry can improve its service delivery and build healthier relationships with consumers. [ABSTRACT FROM AUTHOR]

Deep rest-frame optical spectroscopy is critical for characterizing andunderstanding the physical conditions and properties of the ionized gas ingalaxies. Here, we present a new spectroscopic survey called "Metal Abundancesacross Cosmic Time" or $\mathcal{MACT}$, which will obtain rest-frame opticalspectra for $\sim$3000 emission-line galaxies. This paper describes the opticalspectroscopy that has been conducted with MMT/Hectospec and Keck/DEIMOS for$\approx$1900 $z=0.1-1$ emission-line galaxies selected from our narrowband andintermediate-band imaging in the Subaru Deep Field. In addition, we present asample of 164 galaxies for which we have measured the weak [OIII]$\lambda$4363line (66 with at least 3$\sigma$ detections and 98 with significant upperlimits). This nebular emission line determines the gas-phase metallicity bymeasuring the electron temperature of the ionized gas. This paper presents theoptical spectra, emission-line measurements, interstellar properties (e.g.,metallicity, gas density), and stellar properties (e.g., star formation rates,stellar mass). Paper II of the $\mathcal{MACT}$ survey (Ly et al.) presents thefirst results on the stellar mass--gas metallicity relation at $z\lesssim1$using the sample with [OIII]$\lambda$4363 measurements.

Deep rest-frame optical spectroscopy is critical for characterizing andunderstanding the physical conditions and properties of the ionized gas ingalaxies. Here, we present a new spectroscopic survey called "Metal Abundancesacross Cosmic Time" or $\mathcal{MACT}$, which will obtain rest-frame opticalspectra for $\sim$3000 emission-line galaxies. This paper describes the opticalspectroscopy that has been conducted with MMT/Hectospec and Keck/DEIMOS for$\approx$1900 $z=0.1-1$ emission-line galaxies selected from our narrowband andintermediate-band imaging in the Subaru Deep Field. In addition, we present asample of 164 galaxies for which we have measured the weak [OIII]$\lambda$4363line (66 with at least 3$\sigma$ detections and 98 with significant upperlimits). This nebular emission line determines the gas-phase metallicity bymeasuring the electron temperature of the ionized gas. This paper presents theoptical spectra, emission-line measurements, interstellar properties (e.g.,metallicity, gas density), and stellar properties (e.g., star formation rates,stellar mass). Paper II of the $\mathcal{MACT}$ survey (Ly et al.) presents thefirst results on the stellar mass--gas metallicity relation at $z\lesssim1$using the sample with [OIII]$\lambda$4363 measurements.

Although double-peaked narrow emission-line galaxies have been studied extensively in the past years, only a few are reported with the Green pea (GP) galaxies. Here we present our discovery of five GP galaxies with double-peaked narrow [O  iii ] emission lines, referred to as DPGPs, selected from the LAMOST and SDSS spectroscopic surveys. We find that these five DPGPs have blueshifted narrow components more prominent than the redshifted components, with velocity offsets of [O  iii ]λ5007Å ranging from 306 to 518 |$\rm km\, s^{-1}$|⁠ , and full widths at half maximums of individual components ranging from 263 to 441 |$\rm km\, s^{-1}$|⁠. By analysing the spectra and the spectral energy distributions (SEDs), we find that they have larger metallicities and stellar masses compared with other GPs. The H α line width, emission-line diagnostic, mid-infrared colour, radio emission, and SED fitting provide evidence of the AGN activities in these DPGPs. They have the same spectral properties of type 2 quasars. Furthermore, we discuss the possible nature of the double-peaked narrow emission-line profiles of these DPGPs and find that they are more likely to be dual active galactic nuclei (AGNs). These DPGP galaxies are ideal laboratories for exploring the growth mode of AGNs in the extremely luminous emission-line galaxies, the co-evolution between AGNs and host galaxies, and the evolution of high-redshift galaxies in the early Universe. [ABSTRACT FROM AUTHOR]

We use large simulations of Ly α emitters with different fractions of ionized intergalactic medium to quantify the clustering of Ly α emitters as measured by the void probability function (VPF), and how it evolves under different ionization scenarios. We quantify how well we might be able to distinguish between these scenarios with a deep spectroscopic survey using the future Nancy Grace Roman Space Telescope. Because Roman will be able to carry out blind spectroscopic surveys of Ly α emitters continuously between 7 < z < 12 to sensitivities of at least 10−17 erg s−1 over a wide field of view, it can measure the epoch of reionization as well as the pace of ionization of the intergalactic medium (IGM). We compare deep Roman surveys covering roughly 1, 4, and 16 deg2, and quantify what constraints on reionization the VPF may find for these surveys. A survey of 1 deg2 would distinguish between very late reionization and early reionization to 3 σ near z = 7.7 with the VPF. The VPF of a 4 deg2 survey can distinguish between slow versus fast, as well as early versus late, reionization at >3 σ –4 σ at several redshifts between 7 < z < 9. However, a survey of 13–16 deg2 would allow the VPF to give several robust constraints (>5–8 σ) across the epoch of reionization, and would yield a detailed history of the reionization of the IGM and its effect on Ly α emitter clustering. [ABSTRACT FROM AUTHOR]

The Nancy Grace Roman Space Telescope , NASA's next flagship observatory, will redefine deep-field galaxy survey with a field of view two orders of magnitude larger than Hubble and an angular resolution of matching quality. These future deep-wide galaxy surveys necessitate new simulations to forecast their scientific output and to optimize survey strategies. In this work, we present five realizations of 2-deg2 light cones, containing a total of ≳25 million simulated galaxies with −16 ≳ M UV ≳ −25 spanning z ∼ 0 to 10. This data set enables a new set of experiments with the impacts of survey size on the derived galaxy formation and cosmological constraints. The intrinsic and observable galaxy properties are predicted using a well-established, physics-based semi-analytic modelling approach. We provide forecasts for number density, cosmic SFR, field-to-field variance, and angular two-point correlation functions, and demonstrate how the future wide-field surveys will be able to improve these measurements relative to current generation surveys. We also present a comparison between these light cones and others that have been constructed with empirical models. The mock light cones are designed to facilitate the exploration of multi-instrument synergies and connecting with current generation instruments and legacy surveys. In addition to Roman , we also provide photometry for a number of other instruments on upcoming facilities, including Euclid and Rubin, as well as the instruments, that are part of many legacy surveys. Full object catalogues and data tables for the results presented in this work are made available through a web-based, interactive portal. [ABSTRACT FROM AUTHOR]

Dark matter haloes that reach the H  i -cooling mass without prior star formation or external metal pollution represent potential sites for the formation of small – extremely faint – Population III galaxies at high redshifts. Gravitational lensing may in rare cases boost their fluxes to detectable levels, but to find even a small number of such objects in randomly selected regions of the sky requires very large areas to be surveyed. Because of this, a small, wide-field telescope can in principle offer better detection prospects than a large telescope with a smaller field of view. Here, we derive the minimum comoving number density required to allow gravitational lensing to lift such objects at redshift z = 5−16 above the detection thresholds of blind surveys carried out with the James Webb space telescope (JWST), the Roman space telescope (RST) and Euclid. We find that the prospects for photometric detections of Pop III galaxies are promising, and that they are better for RST than for JWST and Euclid. However, the Pop III galaxies favoured by current simulations have number densities too low to allow spectroscopic detections based on the strength of the He  ii 1640 emission line in any of the considered surveys unless very high star formation efficiencies (ϵ ≳ 0.1) are evoked. We argue that targeting individual cluster lenses instead of the wide-field surveys considered in this paper results in better spectroscopic detection prospects, while for photometric detection, the wide-field surveys perform considerably better. [ABSTRACT FROM AUTHOR]

We present a new measurement of the Ly α luminosity function (LF) at redshift z = 6.9, finding moderate evolution from z = 5.7 that is consistent with a fully or largely ionized z ∼ 7 intergalactic medium. Our result is based on four fields of the LAGER (Lyman Alpha Galaxies in the Epoch of Reionization) project. Our survey volume of 6.1 × 106 Mpc3 is double that of the next largest z ∼ 7 survey. We combine two new LAGER fields (WIDE12 and GAMA15A) with two previously reported LAGER fields (COSMOS and CDFS). In the new fields, we identify N = 95 new z = 6.9 Ly α emitter (LAEs) candidates, characterize our survey’s completeness and reliability, and compute Ly α LFs. The best-fit Schechter LF parameters for all four LAGER fields are in good general agreement. Two fields (COSMOS and WIDE12) show evidence for a bright-end excess above the Schechter function fit. We find that the Ly α luminosity density declines at the same rate as the UV continuum LF from z = 5.7 to 6.9. This is consistent with an intergalactic medium that was fully ionized as early as redshift z ∼ 7 or with a volume-averaged neutral hydrogen fraction of x H I < 0.33 at 1 σ. [ABSTRACT FROM AUTHOR]

We study the dependence of Lyα escape from galaxies on UV continuum size and luminosity using a sample of 40 Green Pea (GP) galaxies, which are the best local analogs of high-redshift Lyα emitters (LAEs). We use the Cosmic Origins Spectrograph near-ultraviolet images from the Hubble Space Telescope to measure the UV size and luminosity with 0.″047 spatial resolution. Like most galaxies the GPs show a log-normal size distribution. They also show a positive correlation between size and UV-continuum luminosity. The slope of the size-continuum luminosity relation for GPs is consistent with those of continuum-selected star-forming galaxies (SFGs) at low and high redshifts. A distinctive feature of GPs is a very compact typical radius of 0.33 kpc with a population spread (1σ) of 0.19 kpc. The peak of the size distribution and the intercept of the size–luminosity relation of GPs are noticeably smaller than those of continuum-selected SFGs at similar redshifts. There are statistically significant anticorrelations found between the circularized half-light radius (rcir,50), the Lyα equivalent width (EW(Lyα)), and the Lyα escape faction (), suggesting that small UV-continuum radii are crucial for Lyα emission. GPs and high-redshift LAEs have similar sizes, once spatial resolution effects are properly considered. Our results show that a compact small size is crucial for escape of Lyα photons, and that Lyα emitters show constant characteristic size independent of their redshift. [ABSTRACT FROM AUTHOR]

We calculate the void probability function (VPF) in simulations of Lyα emitters (LAEs) across a wide redshift range (z = 3.1, 4.5, 5.7, 6.6). The VPF measures the zero-point correlation function (i.e., places devoid of galaxies) and naturally connects to higher-order correlation functions while being computationally simple to calculate. We explore the Poissonian and systematic errors on the VPF, specify its accuracy as a function of average source density and the volume probed, and provide the appropriate size scales to measure the VPF. At small radii, the accuracy of the VPF is limited by galaxy density, while at large radii, the VPF is limited by the number of independent volumes probed. We also offer guidelines for understanding and quantifying the error in the VPF. We approximate the error in the VPF by using independent subvolumes of the catalogs, after finding that jackknife statistics underestimate the uncertainty. We use the VPF to probe the strength of higher-order correlation functions by measuring and examining the hierarchical scaling between the correlation functions using the count-in-cells method. The negative binomial model (NBM) has been shown to best describe the scaling between the two-point correlation function and the VPF for low-redshift galaxy observations. We further test the fit of the NBM by directly deriving the volume-averaged two-point correlation function from the VPF and vice versa. We find the NBM best describes the simulated LAEs, with a 1σ deviation from the model in the z = 6.6 catalog. This suggests that LAEs show higher-order clustering terms similar to those of normal low-redshift galaxies. [ABSTRACT FROM AUTHOR]

Lyα emission from galaxies can be utilized to characterize the ionization state in the intergalactic medium (IGM). We report our search for Lyα emission at z > 7 using a comprehensive Keck/MOSFIRE near-infrared spectroscopic data set, as part of the Texas Spectroscopic Search for Lyα Emission at the End of Reionization Survey. We analyze data from 10 nights of MOSFIRE observations which together target 72 high-z candidate galaxies in the GOODS-N field, all with deep exposure times of 4.5–19 hr. Utilizing an improved automated emission-line search, we report 10 Lyα emission lines detected (>4σ) at z > 7, significantly increasing the spectroscopically confirmed sample. Our sample includes large equivalent-width (EW) Lyα emitters (>50 Å), and additional tentative Lyα emission lines detected at 3σ–4σ from five additional galaxies. We constrain the Lyα EW distribution at z ∼ 7.6, finding a significant drop from z ≲ 6, suggesting an increasing fraction of neutral hydrogen (H i) in the IGM in this epoch. We estimate the Lyα transmission through the IGM (=EWz ∼ 7.6/EW) and infer an IGM H i fraction (XHI) of at z ∼ 7.6, which is lower in modest tension (>1σ) with recent measurements at z ∼ 7.6. The spatial distribution of the detected Lyα emitters implies the presence of a potential highly ionized region at z ∼ 7.55, which hosts four Lyα emitters within a ∼40 cMpc spatial separation. The prominence of this ionized region in our data set could explain our lower inferred value of XHI, though our analysis is also sensitive to the chosen reference Lyα EW distribution values and reionization models. [ABSTRACT FROM AUTHOR]

We have studied ultraviolet images of 40 Green Pea galaxies and 15 local Lyman Break Galaxy Analogs to understand the relation between Lyα photon escape and central UV photometric properties. We measured star-formation intensity (SFI; star formation rate per unit area) from the central 250 pc region () using Cosmic Origins Spectrograph near-ultraviolet images from the Hubble Space Telescope. The measured of our sample Green Peas ranges from 2.3–46 M☉ yr−1 kpc−2, with a geometric mean of 15 M☉ yr−1 kpc−2 and a standard deviation of 0.266 dex, forming a relatively narrow distribution. The Lyman Break Galaxy Analogs show a similarly narrow distribution of (0.271 dex), though with a larger mean of 28 M☉ yr−1 kpc−2. We show that while the Lyα equivalent width (EW(Lyα)) and the Lyα escape fraction () are not significantly correlated with the central SFI (), both are positively correlated with the ratio of surface brightness to galaxy stellar mass (S250 pc/Mstar), with correlation coefficients (p-values) of 0.702 (1 × 10−8) and 0.529 (5 × 10−4) with EW(Lyα) and , respectively. These correlations suggest a scenario where intense central star formation can drive a galactic wind in galaxies with relatively shallow gravitational potential wells, thus clearing channels for the escape of Lyα photons. [ABSTRACT FROM AUTHOR]

The Square Kilometre Array (SKA) is expected to provide the first tomographic observations of the neutral intergalactic medium at redshifts z > 6 and pinpoint the locations of individual ionized bubbles during early stages of cosmic reionization. In scenarios where star-forming galaxies provide most of the ionizing photons required for cosmic reionization, one expects the first ionized bubbles to be centred on overdensities of such galaxies. Here, we model the properties of galaxy populations within isolated, ionized bubbles that SKA-1 should be able to resolve at z ≈ 7–10, and explore the prospects for galaxy counts within such structures with various upcoming near-infrared telescopes. We find that, for the bubbles that are within reach of SKA-1 tomography, the bubble volume is closely tied to the number of ionizing photons that have escaped from the galaxies within. In the case of galaxy-dominated reionization, galaxies are expected to turn up above the spectroscopic detection threshold of JWST and ELT in even the smallest resolvable bubbles at z ≤ 10. The prospects of detecting galaxies within these structures in purely photometric surveys with Euclid, WFIRST, JWST , or ELT are also discussed. While spectroscopy is preferable towards the end of reionization to provide a robust sample of bubble members, multiband imaging may be a competitive option for bubbles at z ≈ 10, due to the very small number of line-of-sight interlopers expected at these redshifts. [ABSTRACT FROM AUTHOR]

We constrain the stellar population properties of a sample of 52 massive galaxies – with stellar mass log (M s/M⊙) ≳ 10.5 – over the redshift range 0.5 < z < 2 by use of observer-frame optical and near-infrared slitless spectra from Hubble Space Telescope 's ACS and WFC3 grisms. The deep exposures (∼100 ks) allow us to target individual spectra of massive galaxies to F160W = 22.5 AB. Our spectral fitting approach uses a set of six base models adapted to the redshift and spectral resolution of each observation, and fits the weights of the base models, including potential dust attenuation, via a Markov Chain Monte Carlo method. Our sample comprises a mixed distribution of quiescent (19) and star-forming galaxies (33). We quantify the width of the age distribution (Δ t) that is found to dominate the variance of the retrieved parameters according to principal component analysis. The population parameters follow the expected trend towards older ages with increasing mass, and Δ t appears to weakly anticorrelate with stellar mass, suggesting a more efficient star formation at the massive end. As expected, the redshift dependence of the relative stellar age (measured in units of the age of the Universe at the source) in the quiescent sample rejects the hypothesis of a single burst (aka monolithic collapse). Radial colour gradients within each galaxy are also explored, finding a wider scatter in the star-forming subsample, but no conclusive trend with respect to the population parameters. [ABSTRACT FROM AUTHOR]

We report the discovery of 14 Lyα blobs (LABs) at z ~ 0.3, existing at least 4-7 billion years later in the Universe than all other LABs known. Their optical diameters are 20-70 kpc, and GALEX data imply Lyα luminosities of (0.4-6.3) × 1043 erg s-1. Contrary to high-z LABs, they live in low-density areas. They are ionized by AGN, suggesting that cold accretion streams as a power source must deplete between z = 2 and 0.3. We also show that transient AGN naturally explain the ionization deficits observed in many LABs. Their Lyα and X-ray fluxes decorrelate below ≲106 years because of the delayed escape of resonantly scattering Lyα photons. High Lyα luminosities do not require currently powerful AGN, independent of obscuration. Chandra X-ray data reveal intrinsically weak AGN, confirming the luminous optical nebulae as impressive ionization echoes. For the first time, we also report mid-infrared thermal echoes from the dusty tori. We conclude that the AGN have faded by three to four orders of magnitude within the last 104-5 years, leaving fossil UV, optical and thermal radiation behind. The host galaxies belong to the group of previously discovered Green Bean galaxies (GBs). Gemini optical imaging reveals smooth spheres, mergers, spectacular outflows and ionization cones. Because of their proximity and high flux densities, GBs are perfect targets to study AGN feedback, mode switching and the Lyα escape. The fully calibrated, co-added optical FITS images are publicly available. [ABSTRACT FROM AUTHOR]

The power situation in rural India continues to remain poor with around one-third of the rural population without access to any form of electricity. The consequence of which is kerosene being used as a major source of lighting for un-electrified households as well as households with intermittent access to electricity in rural areas. While grid based electrification has been the most common approach, decentralized renewable energy options especially, solar PV systems have also been adopted as a cost effective mode of electrification. This paper presents the results of socio-technical assessment of solar photovoltaic interventions namely, solar home systems, solar mini-grid and solar AC pico-grids, which have been used to electrify selected villages in Sundarbans region of India. The study is focused on technical, financial, and institutional aspects along with the social impact assessment of PV based electrification in the Sundarbans region. The results of the study elucidate that, in general, the impacts of the solar PV solutions used for electrification have been largely positive, especially benefits of reduced kerosene consumption, ease in studying and cooking and reduced health effects. The study also finds that technology is not the only factor on which the viability of a program depends, but institutional and financial aspects also play a significant role. The need of the hour is to develop a strong institutional framework and enabling policies for achieving higher success rates in PV programs. [ABSTRACT FROM AUTHOR]

We present the first dynamical mass measurements for Lyα galaxies at high redshift, based on velocity dispersion measurements from rest-frame optical emission lines and size measurements from Hubble Space Telescope imaging, for nine galaxies drawn from four surveys. We use these measurements to study Lyα galaxies in the context of galaxy scaling relations. The resulting dynamical masses range from 109 to 1010M☼. We also fit stellar population models to our sample and use them to place the Lyα sample on a stellar mass versus line width relation. The Lyα galaxies generally follow the same scaling relation as star-forming galaxies at lower redshift, although, lower stellar mass fits are also acceptable in ∼1/3 of the Lyα galaxies. Using the dynamical masses as an upper limit on gas mass, we show that Lyα galaxies have unusually active star formation for their gas mass surface density. This behavior is consistent with what is observed in starburst galaxies, despite the typically smaller masses and sizes of the Lyα galaxy population. Finally, we examine the mass densities of these galaxies and show that their future evolution likely requires dissipational (“wet”) merging. In short, we find that Lyα galaxies are low-mass cousins of larger starbursts. [ABSTRACT FROM AUTHOR]

We present observations of a luminous galaxy at z = 6.573-the end of the reionization epoch-which has been spectroscopically confirmed twice. The first spectroscopic confirmation comes from slitless Hubble Space Telescope Advanced Camera for Surveys grism spectra from the PEARS survey (Probing Evolution And Reionization Spectroscopically), which show a dramatic continuum break in the spectrum at rest frame 1216 Å. The second confirmation is done with Keck + DEIMOS. The continuum is not clearly detected with ground-based spectra, but high wavelength resolution enables the Lyα emission line profile to be determined. We compare the line profile to composite line profiles at z = 4.5. The Lyα line profile shows no signature of a damping wing attenuation, confirming that the intergalactic gas is ionized at z = 6.57. Spectra of Lyman breaks at yet higher redshifts will be possible using comparably deep observations with IR-sensitive grisms, even at redshifts where Lyα is too attenuated by the neutral intergalactic medium to be detectable using traditional spectroscopy from the ground. [ABSTRACT FROM AUTHOR]

We present a full analysis of the Probing Evolution And Reionization Spectroscopically (PEARS) slitess grism spectroscopic data obtained with the Advanced Camera for Surveys on board Hubble Space Telescope. PEARS covers fields within both the Great Observatories Origins Deep Survey (GOODS) North and South fields, making it ideal as a random survey of galaxies, as well as the availability of a wide variety of ancillary observations complemented by the spectroscopic results. Using the PEARS data, we are able to identify star-forming galaxies (SFGs) within the redshift volume 0 < z < 1.5. Star-forming regions in the PEARS survey are pinpointed independently of the host galaxy. This method allows us to detect the presence of multiple emission-line regions (ELRs) within a single galaxy. We identified a total of 1162 Hα, [OIII], and/or [O II] emission lines in the PEARS sample of 906 galaxies to a limiting flux of ~10-18 erg s-1 cm-2. The ELRs have also been compared to the properties of the host galaxy, including morphology, luminosity, and mass. From this analysis, we find three key results: (1) the computed line luminosities show evidence of a flattening in the luminosity function with increasing redshift; (2) the star-forming systems show evidence of complex morphologies with star formation occurring predominantly within one effective (half-light) radius. However, the morphologies show no correlation with host stellar mass. (3) Also, the number density of SFGs with M" ⩾ 109 M☉ decreases by an order of magnitude at z ⩽ 0.5 relative to the number at 0.5 < z <0.9, supporting the argument of galaxy downsizing. [ABSTRACT FROM AUTHOR]

We present a spectroscopically confirmed sample of Lyman α emitting galaxies (LAEs) at z ∼ 4.5 in the Extended Chandra Deep Field-South (ECDFS), which we combine with a sample of z ∼ 4.5 LAEs from previous narrow-band surveys from the Large Area Lyman Alpha (LALA) survey to build a unified Lyα luminosity function. We spectroscopically observed 64 candidate LAEs in the ECDFS, confirming 46 objects as z ∼ 4.5 LAEs based on single-line detections with no continuum emission bluewards of the line, resulting in a Lyα confirmation rate of ∼70 per cent. We did not detect significant flux from neither the C iv λ1549 Å emission line nor the He ii λ1640 Å emission line in individual LAE spectra. These lines were also undetected in a co-added spectrum, with the co-added line ratio of He ii to Lyα constraining the Population III star formation rate (SFR) to be <0.3 per cent of the total SFR and <1.25 per cent of the observed SFR (both at the 2σ level). We combine the optical spectra with deep X-ray and radio images to constrain the AGN fraction in the sample. Only LAE was detected in both the X-ray and radio, while the other objects remained undetected, even when stacked. The Lyα luminosity functions in our two deepest narrow-band filters in the ECDFS differ at greater than 2σ significance, and the product L*Φ* differs by a factor of >3. Similar luminosity function differences have been used to infer evolution in the neutral gas fraction in the intergalactic medium at z > 6, yet here the difference is likely due to cosmic variance, given that the two samples are from adjoining line-of-sight volumes. Combining our new sample of LAEs with those from previous LALA narrow-band surveys at z = 4.5, we obtain one of the best measured Lyα luminosity functions to date, with our sample of over 200 spectroscopically confirmed Lyα galaxies yielding log10(L*) = 42.83 ± 0.06 (erg s−1) and log10(Φ*) = −3.48 ± 0.09 (Mpc−3). We compare our new luminosity function to others from the literature to study the evolution of the Lyα luminosity density at 0 < z < 7. We find tentative evidence for evolution in the product L*Φ*, which approximately tracks the cosmic SFR density, but since field-to-field and survey-to-survey variations are in some cases as large as the possible evolution, some caution is needed in interpreting this trend. [ABSTRACT FROM AUTHOR]

We present spectroscopic measurements of the [O III] emission line from two subregions of strong Lyα emission in a radio-quiet Lyman-alpha blob (LAB). The blob under study is LAB1 at z ~ 3.1, and the [OIII] detections are from the two Lyman break galaxies (LBGs) embedded in the blob halo. The [OIII] measurements were made with LUCIFER on the 8.4 m Large Binocular Telescope and NIRSPEC on 10 m Keck Telescope. Comparing the redshift of the [OIII] measurements to Lyα redshifts from SAURON allows us to take a step toward understanding the kinematics of the gas in the blob. Using both LUCIFER and NIRSPEC we find velocity offsets between the [OIII] and Lyα redshifts that are modestly negative or consistent with 0 km s-1 in both subregions studied (ranging from -72±42-+6±33 km s-1). A negative offset means Lyα is blueshifted with respect to [O III] a positive offset then implies Lyα is redshifted with respect to [O III]. These results may imply that outflows are not primarily responsible for Lyman alpha escape in this LAB, since outflows are generally expected to produce a positive velocity offset. In addition, we present an [O III] line flux upper limit on a third region of LAB1, a region that is unassociated with any underlying galaxy. We find that the [OIII] upper limit from the galaxy-unassociated region of the blob is at least 1.4-2.5 times fainter than the [OIII] flux from one of the LBG-associated regions and has an [O III] to Lyα ratio measured at least 1.9-3.4 times smaller than the same ratio measured from one of the LBGs. [ABSTRACT FROM AUTHOR]

We have developed a new method for fitting spectral energy distributions (SEDs) to identify and constrain the physical properties of high-redshift (4 < ȥ < 8) galaxies. Our approach uses an implementation of Bayesian based Markov Chain Monte Carlo that we have dubbed "πMC² ." It allows us to compare observations to arbitrarily complex models and to compute 95% credible intervals that provide robust constraints for the model parameters. The work is presented in two sections. In the first, we test πMC² using simulated SEDs to not only confirm the recovery of the known inputs but to assess the limitations of the method and identify potential hazards of SED fitting when applied specifically to high-redshift (ȥ > 4) galaxies. In the second part of the paper we apply πMC² to thirty-three 4 < ȥ < 8 objects, including the spectroscopically confirmed Grism ACS Program for Extragalactic Science Lyα sample (4 < ȥ < 6), supplemented by newly obtained Hubble Space Telescope/WFC3 near-IR observations, and several recently reported broadband selected ȥ > 6 galaxies. Using πMC², we are able to constrain the stellar mass of these objects and in some cases their stellar age and find no evidence that any of these sources formed at a redshift larger than ȥ = 8, a time when the universe was ≈0.6 Gyr old. [ABSTRACT FROM AUTHOR]

We have co-added the X-ray flux of all known Lyα emitters (LAEs) in the 4 Ms Chandra Deep Field South (CDF-S) region, achieving the tightest upper limits yet on the X-ray to Lyα ratio. We use the X-ray data to place sensitive upper limits on the average unobscured star formation rate (SFRX) in these galaxies. A very small traction of α galaxies in the field are individually detected in the X-rays, implying a low fraction of active galactic nucleus activity. After excluding the few X-ray-detected LAEs, we stack the undetected LAEs located in the 4 Ms CDF-S data and 250 ks Extended CDF-S (ECDF-S) data, and compute a 1σ upper limit on SFRX < 1.6, 14, 28, 28, 140, 440, 880M⊙ yr-1 for LAEs located at z ~ 0.3 and z = 2.1, 3.1, 3.2, 4.5, 5.7, and 6.5, respectively. The upper limit of SFRX in LAEs can be then compared to SFRLyα derived from α line and thus can constrain on the α escape fraction Due to image rights restrictions, multiple line equation(s) cannot be graphically displayed. The Due to image rights restrictions, multiple line equation(s) cannot be graphically displayed from X-ray at z ~ 0.3 is substantially larger than that from UV or Hα. Three X-ray-detected LAE galaxies at z ~ 0.3 show Due to image rights restrictions, multiple line equation(s) cannot be graphically displayed ~3%-22%, and the average Lyα escape fraction from stacking the X-ray-undetected LAEs show Due to image rights restrictions, multiple line equation(s) cannot be graphically displayed > 28% at 3σ significance level at the same redshift. We derive a lower limit on Due to image rights restrictions, multiple line equation(s) cannot be graphically displayed > 14% (84% confidence level, 1σ lower limit) for LAEs at redshift z ~ 2.1 and z ~ 3.1-3.2. At z > 4, the current LAE samples are not of sufficient size to constrain SFRX well. By averaging all the LAEs at z > 2, the X-ray non-detection constrains Due to image rights restrictions, multiple line equation(s) cannot be graphically displayed > 17% (84% confidence level, 1σ lower limit), and reject Due to image rights restrictions, multiple line equation(s) cannot be graphically displayed < 5.7% at the 99.87% confidence level from 2.1 < z < 6.5. [ABSTRACT FROM AUTHOR]

The study of Lyα emission in the high-redshift universe is a useful probe of the epoch of reionization, as the Lyα line should be attenuated by the intergalactic medium (IGM) at low to moderate neutral hydrogen fractions. Here we present the results of a deep and wide imaging search for Lyα emitters in the Cosmological Evolution Survey field. We have used two ultra-narrowband filters (filter width of ~8-9 Å) on the NOAO Extremely Wide-Field Infrared Mosaic camera, installed on the Mayall 4 m telescope at Kitt Peak National Observatory, in order to isolate Lyα emitters at z = 7.7; such ultra-narrowband imaging searches have proved to be excellent at detecting Lyα emitters. We found 5σ detections of four candidate Lyα emitters in a survey volume of 2.8 x 104 Mpc³ (total survey area ~760 arcmin²). Each candidate has a line flux greater than 8 x 10-18 erg s-1 cm-2. Using these results to construct a luminosity function and comparing to previously established Lyα luminosity functions at z = 5.7 and z = 6.5, we find no conclusive evidence for evolution of the luminosity function between z = 5.7 and z =7.7. Statistical Monte Carlo simulations suggest that half of these candidates are real z = 7.7 targets, and spectroscopic follow-up will be required to verify the redshift of these candidates. However, our results are consistent with no strong evolution in the neutral hydrogen fraction of the IGM between z = 5.7 and z = 7.7, even if only one or two of the z = 7.7 candidates are spectroscopically confirmed. [ABSTRACT FROM AUTHOR]

We present the highest redshift detections of resolved Lyα emission, using Hubble Space Telescope (HST)/Advanced Camera for Surveys F658N narrowband-imaging data taken in parallel with theWide Field Camera 3 Early Release Science program in the GOODS Chandra Deep Field-South. We detect Lyα emission from three spectroscopically confirmed z = 4.4 Lyα emitting galaxies (LAEs), more than doubling the sample of LAEs with resolved Lyα emission. Comparing the light distribution between the rest-frame ultraviolet continuum and narrowband images, we investigate the escape of Lyα photons at high redshift.While our data do not support a positional offset between the Lyα and rest-frame ultraviolet (UV) continuum emission, the half-light radius in one out of the three galaxies is significantly (>1σ) larger in Lyα than in the rest-frame UV continuum. Stacking the three LAEs in both the narrowband and UV continuum images, we find that the Lyα light appears larger than the rest-frame UV at 4.2σ significance. This Lyα flux detected with HST is a factor of 4-10 less than observed in similar filters from the ground. These results together imply that the Lyα emission is not strictly confined to its indigenous star-forming regions. Rather, for at least one object the Lyα emission is more extended, with the missing HST flux possibly existing in a diffuse outer halo. This suggests that the radiative transfer of Lyα photons in high-redshift LAEs is complicated, with the interstellar-medium geometry and/or outflows playing a significant role in galaxies at these redshifts. [ABSTRACT FROM AUTHOR]

We present the results of an optical spectroscopic study of 12 GALEX-discovered star-forming Lyα emitting galaxies (LAEs) at z ~ 0.3. We measure the emission-line fluxes from these galaxies by fitting their observed spectra to stellar population models in order to correct for underlying stellar absorption. We revisit earlier stellar population model fitting results, finding that excluding now-known active galactic nuclei lowers the typical stellar population age and stellar mass of this sample to ~300 Myr and ~4 x 109 M..., respectively. We calculate their dust extinction using the Balmer decrement, and find a typical visual attenuation ofAv ~ 0.3 mag, similar to that seen in some high- redshift LAEs. Comparing the ratios of Lyα/Hα and the Lyα equivalent widths to the measured dust extinction, we find that the interstellar media (ISMs) in these objects appear to be neither enhancing nor seriously attenuating the Lyα equivalent widths, as would be the case in a quasi-clumpy ISM. Lastly, we perform a detailed analysis of the gas-phase metallicities of these galaxies, and we find that most galaxies in our sample have Z ≲ 0.4 Z.... We find that at a fixed stellar mass, these low-redshift LAE analogs are offset by ~0.3-0.6 dex lower metallicity from the general galaxy population at similar redshifts based on the local mass-metallicity relationship. This implies that galaxies with Lyα in emission may be systematically more metal-poor than star-forming galaxies at the same stellar mass and redshift, similar to preliminary results at z ~ 2. [ABSTRACT FROM AUTHOR]

Recent results have shown that a substantial fraction of high-redshift Lyman α (Lyα) galaxies contain considerable amounts of dust. This implies that Lyα galaxies are not primordial, as has been thought in the past. However, this dust has not been directly detected in emission; rather it has been inferred based on extinction estimates from rest-frame ultraviolet (UV) and optical observations. This can be tricky, as both dust and old stars redden galactic spectra at the wavelengths used to infer dust. Measuring dust emission directly from these galaxies is thus a more accurate way to estimate the total dust mass, giving us real physical information on the stellar populations and interstellar medium enrichment. New generation instruments, such as the Atacama Large Millimeter Array and Sub-Millimeter Array, should be able to detect dust emission from some of these galaxies in the submillimeter. Using measurements of the UV spectral slopes, we derive far-infrared flux predictions for of a sample of Lyα galaxies. We find that in only a few hours, we can detect dust emission from 39 ± 22 per cent of our Lyα galaxies. Comparing these results to those found from a sample of 21 Lyman break galaxies (LBGs), we find that LBGs are on average 60 per cent more likely to be detected than Lyα galaxies, implying that they are more dusty, and thus indicating an evolutionary difference between these objects. These observations will provide better constraints on dust in these galaxies than those derived from their UV and optical fluxes alone. Undeniable proof of dust in these galaxies could explain the larger than expected Lyα equivalent widths seen in many Lyα galaxies today. [ABSTRACT FROM AUTHOR]

The galaxy population at has been the subject of intense study in recent years, culminating in the Hubble Ultra Deep Field (HUDF) – the deepest imaging survey yet. A large number of high-redshift galaxy candidates have been identified within the HUDF, but until now analysis of their properties has been hampered by the difficulty of obtaining spectroscopic redshifts for these faint galaxies. Our ‘Gemini Lyman-Alpha at Reionization Era’ (GLARE) project has been designed to undertake spectroscopic follow-up of faint i′-drop galaxies at in the HUDF. In a previous paper we presented preliminary results from the first 7.5 h of data from GLARE. In this paper we detail the complete survey. We have now obtained 36 h of spectroscopy on a single GMOS slitmask from Gemini-South, with a spectral resolution of . We identify five strong Lyα emitters at , and a further nine possible line emitters with detections at lower significance. We also place tight constraints on the equivalent width of Lyα emission for a further ten i′-drop galaxies and examine the equivalent width distribution of this faint spectroscopic sample of galaxies. We find that the fraction of galaxies with little or no emission is similar to that at , but that the population has a tail of sources with high rest-frame equivalent widths. Possible explanations for this effect include a tendency towards stronger line emission in faint sources, which may arise from extreme youth or low metallicity in the Lyman-break population at high redshift, or possibly a top-heavy initial mass function. [ABSTRACT FROM AUTHOR]

Lyman-α emitting (LAE) galaxies observed at intermediate to high redshift have the correct size, mass, star formation rate, metallicity, and space density to have been the formation sites of metal-poor globular clusters. LAEs are typically small galaxies with transient starbursts. They should accrete onto spiral and elliptical galaxies over time, delivering metal-poor clusters into the larger galaxies' halos as they themselves get dispersed by tidal forces. The galaxy WLM is a good example of a dwarf remnant from a very early starburst that contains a metal-poor globular cluster but failed to get incorporated into the Milky Way or M31 because of its remote location in the local group. [ABSTRACT FROM PUBLISHER]

We report on two regularly rotating galaxies at redshift z ≈ 2, using high-resolution spectra of the bright [C II] 158 μm emission line from the HIFI instrument on the Herschel Space Observatory. Both SDSS090122.37+181432.3 (“S0901”) and SDSSJ120602.09+514229.5 (“the Clone”) are strongly lensed and show the double-horned line profile that is typical of rotating gas disks. Using a parametric disk model to fit the emission line profiles, we find that S0901 has a rotation speed of vsin (i) ≈ 120 ± 7 km s–1 and a gas velocity dispersion of σg < 23 km s–1 (1σ). The best-fitting model for the Clone is a rotationally supported disk having vsin (i) ≈ 79 ± 11 km s–1 and σg ≲ 4 km s–1 (1σ). However, the Clone is also consistent with a family of dispersion-dominated models having σg = 92 ± 20 km s–1. Our results showcase the potential of the [C II] line as a kinematic probe of high-redshift galaxy dynamics: [C II] is bright, accessible to heterodyne receivers with exquisite velocity resolution, and traces dense star-forming interstellar gas. Future [C II] line observations with ALMA would offer the further advantage of spatial resolution, allowing a clearer separation between rotation and velocity dispersion. [ABSTRACT FROM AUTHOR]