Filamentary Large-scale Structure Traced by Six Lyα Blobs at z = 2.3

Extended nebulae of Lyα emission ("Lyα blobs") are known to be associated with overdense regions at high redshift. Here we present six large Lyα blobs in a previously known protocluster with galaxy overdensity δ ~ 7 at z = 2.3; this is the richest field of giant Lyα blobs detected to date. The blobs have linear sizes of ≳ 100 kpc and Lyα luminosities of ~10^(43) erg s^(–1). The positions of the blobs define two linear filaments with an extent of at least 12 comoving Mpc; these filaments intersect at the center of one of the blobs. Measurement of the position angles of the blobs indicates that five of the six are aligned with these filaments to within ~10°, suggesting a connection between the physical processes powering extended Lyα emission and those driving structure on larger scales

Discovery of Two Spectroscopically Peculiar, Low-Luminosity Quasars at z~4

We report the discovery of two low-luminosity quasars at z~4, both of which show prominent N IV] 1486A emission. This line is extremely rare in quasar spectra at any redshift; detecting it in two out of a sample of 23 objects (i.e., ~ 9% of the sample) is intriguing and is likely due to the low-luminosity, high-redshift quasar sample we are studying. This is still a poorly explored regime, where contributions from associated, early starbursts may be significant. One interpretation of this line posits photoionization by very massive young stars. Seeing N IV] 1486A emission in a high-redshift quasar may thus be understood in the context of co-formation and early co-evolution of galaxies and their supermassive black holes. Alternatively, we may be seeing a phenomenon related to the early evolution of quasar broad emission line regions. The non-detection (and possibly even broad absorption) of N V 1240A line in the spectrum of one of these quasars may support that interpretation. These two objects may signal a new faint quasar population or an early AGN evolutionary stage at high redshifts.Comment: 15 pages, 5 figures, Accepted for publicated in ApJ Letter

Q1549-C25: A Clean Source of Lyman-Continuum Emission at z=3.15z=3.15

We present observations of Q1549-C25, an ~L* star-forming galaxy at z=3.15 for which Lyman-continuum (LyC) radiation is significantly detected in deep Keck/LRIS spectroscopy. We find no evidence for contamination from a lower-redshift interloper close to the line of sight in the high signal-to-noise spectrum of Q1549-C25. Furthermore, the morphology of Q1549-C25 in V_606, J_125, and H_160 Hubble Space Telescope (HST) imaging reveals that the object consists of a single, isolated component within 1". In combination, these data indicate Q1549-C25 as a clean spectroscopic detection of LyC radiation, only the second such object discovered to date at z~3. We model the spectral energy distribution (SED) of Q1549-C25, finding evidence for negligible dust extinction, an age (assuming continuous star formation) of ~1 Gyr, and a stellar mass of M_*=7.9x10^9 M_sun. Although it is not possible to derive strong constraints on the absolute escape fraction of LyC emission, f_esc(LyC), from a single object, we use simulations of intergalactic and circumgalactic absorption to infer f_esc(LyC)>=0.51 at 95% confidence. The combination of deep Keck/LRIS spectroscopy and HST imaging is required to assemble a larger sample of objects like Q1549-C25, and obtain robust constraints on the average f_esc(LyC) at z~3 and beyond.Comment: 6 pages, 5 figures, accepted to ApJ Letter

Effect of non-genetic factors on standard lactation milk performance traits in simmental cows

The effect of systematic and continuous environmental factors on milk performance traits over standard lactations in 2805 Simmental cows was evaluated using the general linear model. The systematic factors included the effect of farm or breeding area, calving season, year of birth, season of birth, lactation group and their interactions. The continuous factor analysed was the effect of age at first conception. The effect of farm, lactation group and calving season on standard lactation milk performance was found to be highly significant (P lt 0.01), excepting the effect of calving season on milk fat percent in standard lactations which showed statistical significance (P lt 0.05). The interactions between year and season of birth, farm and calving season, and farm and lactation group had a highly significant effect (P lt 0.01) on all performance traits studied. Age at first conception, as a continuous factor, had a highly significant effect (P lt 0.01) on milk yield and milk fat percent, and a non-significant effect on milk fat yield. The model used to correct the performance traits over standard lactations for the effect of systematic factors was highly significant (P lt 0.01). The variance of the model accounted for 20.06 and 37.31% of the total variance of milk fat yield and milk fat percent, respectively. The resulting coefficients of determination (R-2) ranged from 0.20 for milk fat yield to 0.37 for milk fat percent

Spectroscopic Measurements of the Far-Ultraviolet Dust Attenuation Curve at z~3

We present the first spectroscopic measurements of the shape of the far-ultraviolet (far-UV; λ = 950-1500 Å) dust attenuation curve at high redshift (z ~ 3). Our analysis employs rest-frame UV spectra of 933 galaxies at z ~ 3, 121 of which have very deep spectroscopic observations (≳7hr) at λ = 850 - 1300 Å, with the Low Resolution Imaging Spectrograph on the Keck Telescope. By using an iterative approach in which we calculate the ratios of composite spectra in different bins of continuum color excess, E(B-V), we derive a dust curve that implies a lower attenuation in the far-UV for a given E(B-V) than those obtained with standard attenuation curves. We demonstrate that the UV composite spectra of z ~ 3 galaxies can be modeled well by assuming our new attenuation curve, a high covering fraction of Hi, and absorption from the Lyman–Werner bands of H_2 with a small (≾20%) covering fraction. The low covering fraction of H_2 relative to that of the H_I and dust suggests that most of the dust in the ISM of typical galaxies at z ~ 3 is unrelated to the catalysis of H_2, and is associated with other phases of the ISM (i.e., the ionized and neutral gas). The far-UV dust curve implies a factor of ≈ 2 lower dust attenuation of Lyman continuum (ionizing) photons relative to those inferred from the most commonly assumed attenuation curves for L^* galaxies at z ~ 3. Our results may be utilized to assess the degree to which ionizing photons are attenuated in H ii regions or, more generally, in the ionized or low column density N(HI) ≾ 10^(17.2) cm^(−2) neutral ISM of high-redshift galaxies

The Relationship between Stellar Populations and Lyα Emission in Lyman Break Galaxies

We present the results of a photometric and spectroscopic survey of 321 Lyman break galaxies (LBGs) at z ~ 3 to investigate systematically the relationship between Lyα emission and stellar populations. Lyα equivalent widths (W_(Lyα)) were calculated from rest-frame UV spectroscopy and optical/near-infrared/Spitzer photometry was used in population synthesis modeling to derive the key properties of age, dust extinction, star formation rate (SFR), and stellar mass. We directly compare the stellar populations of LBGs with and without strong Lyα emission, where we designate the former group (W_(Lyα) ≥ 20 Å) as Lyα emitters (LAEs) and the latter group (W_(Lyα) < 20 Å) as non-LAEs. This controlled method of comparing objects from the same UV luminosity distribution represents an improvement over previous studies in which the stellar populations of LBGs and narrowband-selected LAEs were contrasted, where the latter were often intrinsically fainter in broadband filters by an order of magnitude simply due to different selection criteria. Using a variety of statistical tests, we find that Lyα equivalent width and age, SFR, and dust extinction, respectively, are significantly correlated in the sense that objects with strong Lyα emission also tend to be older, lower in SFR, and less dusty than objects with weak Lyα emission, or the line in absorption. We accordingly conclude that, within the LBG sample, objects with strong Lyα emission represent a later stage of galaxy evolution in which supernovae-induced outflows have reduced the dust covering fraction. We also examined the hypothesis that the attenuation of Lyα photons is lower than that of the continuum, as proposed by some, but found no evidence to support this picture

The Connection Between Reddening, Gas Covering Fraction, and the Escape of Ionizing Radiation at High Redshift

Using a large sample of spectroscopically confirmed z ~ 3 galaxies, we establish an empirical relationship between reddening (E(B-V), neutral gas covering fraction (f_(cov)HI), and the escape of ionizing (Lyman continuum, LyC) photons. Our sample includes 933 galaxies at z ~ 3,121 of which have deep spectroscopic observations (≳7 hr) at 850 ≾ λ_(rest) ≾ 1300 Å with the Low Resolution Imaging Spectrograph on Keck. The high covering fraction of outflowing optically thick HI indicated by the composite pectra of these galaxies implies that photoelectric absorption, rather than dust attenuation, dominates the depletion of LyC photons. By modeling the composite spectra as the combination of an unattenuated stellar spectrum including nebular continuum emission with one that is absorbed by HI and reddened by a line-of-sight extinction, we derive an empirical relationship between E(B-V) and f_(cov) HI. Galaxies with redder UV continua have larger covering fractions of HI characterized by higher line-of-sight extinctions. We develop a model which connects the ionizing escape fraction with E(B-V), and which may be used to estimate the ionizing escape fraction for an ensemble of galaxies. Alternatively, direct measurements of the escape fraction for our sample allow us to constrain the intrinsic LyC-to-UV flux density ratio to be 〈900 Å)/S(1500 Å〉_(int) ≳ 0.20, a value that favors stellar population models that include weaker stellar winds, a flatter initial mass function, and/or binary evolution. Last, we demonstrate how the framework discussed here may be used to assess the pathways by which ionizing radiation escapes from high-redshift galaxies

The Keck Lyman Continuum Spectroscopic Survey (KLCS): The Emergent Ionizing Spectrum of Galaxies at z ∼ 3

We present results of a deep spectroscopic survey quantifying the statistics of the escape of ionizing radiation from star-forming galaxies at z ~ 3. We measure the ratio of ionizing to non-ionizing UV flux density 〈f_(900)/f_(1500) 〉_(obs), where f_(900) is the mean flux density evaluated over the range [880, 910] Å. We quantify the emergent ratio of ionizing to non-ionizing UV flux density by analyzing high signal-to-noise ratio composite spectra formed from subsamples with common observed properties and numbers sufficient to reduce the statistical uncertainty in the modeled IGM+CGM correction to obtain precise values of 〈f_(900)/f_(1500) 〉_(out), including a full-sample average 〈f_(900)/f_(1500) 〉_(out) = 0.057 ± 0.006. We show that 〈f_(900)/f_(1500) 〉_(out) increases monotonically with W_ λ(Lyα), inducing an inverse correlation with UV luminosity as a by-product. We fit the composite spectra using stellar spectral synthesis together with models of the ISM in which a fraction f c of the stellar continuum is covered by gas with column density N_(H1). We show that the composite spectra simultaneously constrain the intrinsic properties of the stars (L_(900)/L_(1500))_(int) along with f_c , N_(H1), E(B - V), and f_(esc,abs), the absolute escape fraction of ionizing photons. We find a sample-averaged f-(esc,abs) = 0.09 ± 0.01, with subsamples falling along a linear relation 〈f_(esc,abs) 〉 ≃ 0.75[W_ λ(Lyα)/110 Å]. Using the far-UV luminosity function, the distribution function n(W(Lyα)), and the relationship between W_ λ(Lyα) and f_(900)/f_(1500) 〉_(out), we estimate the total ionizing emissivity of z ~ 3 star-forming galaxies with M_(uv) ≤ −19.5, which exceeds the contribution of quasi-stellar objects by a factor of ~3, and accounts for ~50% of the total ϵ_(LyC) at z ~ 3 estimated using indirect methods

Establishment and confirmation of heterotic groups and genetic diversity assessment of maize inbred lines using microsatellite data

Twenty-seven maize inbreds (12 commercial and 15 developing lines) from Maize Research Institute breeding program were subjected to microsatelite analysis. The aim was genetic diversity determination, establishing relationships among tested lines and assigning them to heterotic groups according to molecular marker data. Number of alelles detected was 97, with an average of 3.23. Major allele frequency was in a range from 0.33 to 0.82 (average 0.55). The highest value for observed heterozygosity was 10% for several developing lines. Mean values for gene diversity and PIC were 0.56 and 0.48, respectively. Frequency-based distances were calculated using Roger's coefficient and average value of 0.57 indicates high genetic diversity in analyzed maize inbreds. Distance matrices were subjected to cluster analysis and PCA. Multivariate analysis methods showed considerable concurrency with pedigree data. Results of analysis with 30 microsatellite markers could be useful for defining/redefining heterotic groups but should be complemented with field testing data