A Study of Interstellar Gas and Stars in the Gravitationally Lensed Galaxy `The Cosmic Eye' from Rest-Frame Ultraviolet Spectroscopy

We report the results of a study of the rest-frame UV spectrum of the Cosmic Eye, a luminous Lyman break galaxy at z=3.07331 gravitationally lensed by a factor of 25. The spectrum, recorded with the ESI spectrograph on the Keck II telescope, is rich in absorption features from the gas and massive stars in this galaxy. The interstellar absorption lines are resolved into two components of approximately equal strength and each spanning several hundred km/s in velocity. One component has a net blueshift of -70 km/s relative to the stars and H II regions and presumably arises in a galaxy-scale outflow similar to those seen in most star-forming galaxies at z = 2-3. The other is more unusual in showing a mean redshift of +350 km/s relative to the systemic redshift; possible interpretations include a merging clump, or material ejected by a previous star formation episode and now falling back onto the galaxy, or more simply a chance alignment with a foreground galaxy. In the metal absorption lines, both components only partially cover the OB stars against which they are being viewed. We tentatively associate the redshifted component with the strong damped Lyman alpha line, indicative of a column density N(H I) = (3.0 +/- 0.8) x 10(21) atoms/cm2, and propose that it provides the dust `foreground screen' responsible for the low ratio of far-infrared to UV luminosities of the Cosmic Eye. Compared to other well-studied examples of strongly lensed galaxies, we find that the young stellar population of the Cosmic Eye is essentially indistinguishable from those of the Cosmic Horseshoe and MS 1512-cB58, while the interstellar spectra of all three galaxies are markedly different, attesting to the real complexity of the interplay between starbursts and ambient interstellar matter in young galaxies (abridged).Comment: 14 pages, 6 Figures, Accepted for publication in Monthly Notices of the Royal Astronomical Society after minor revision

Prospectus, September 23, 1991

https://spark.parkland.edu/prospectus_1991/1013/thumbnail.jp

The Redshift Evolution of Rest-UV Spectroscopic Properties in Lyman-break Galaxies at z ~ 2–4

We present the first comprehensive evolutionary analysis of the rest-frame UV spectroscopic properties of star-forming galaxies at z ~ 2–4. We match samples at different redshifts in UV luminosity and stellar mass, and perform systematic measurements of spectral features and stellar population modeling. By creating composite spectra grouped according to Lyα equivalent width (EW) and various galaxy properties, we study the evolutionary trends among Lyα, low- and high-ionization interstellar (LIS and HIS) absorption features, and integrated galaxy properties. We also examine the redshift evolution of Lyα and LIS absorption kinematics, and fine-structure emission EWs. The connections among the strengths of Lyα, LIS lines, and dust extinction are redshift independent, as is the decoupling of the Lyα and HIS line strengths, and the bulk outflow kinematics as traced by the LIS lines. Stronger Lyα emission is observed at higher redshift at fixed UV luminosity, stellar mass, SFR, and age. Much of this variation in the average Lyα strength with redshift, and the variation in Lyα strength at fixed redshift, can be explained in terms of variations in the neutral gas covering fraction and/or dust content in the ISM and CGM. However, based on the connection between Lyα and C iii] emission strengths, we additionally find evidence for variations in the intrinsic production rate of Lyα photons at the highest Lyα EWs. The challenge now is to understand the observed evolution of the neutral gas covering fraction and dust extinction within a coherent model for galaxy formation, and make robust predictions for the escape of ionizing radiation at z > 6

HEALTH AND SAFETY MANAGEMENT PRACTICES OF ROAD CONSTRUCTION PROJECTS IN SRI LANKA

Health and Safety Management Practices of Road Construction Projects in Sri Lanka Road construction workers are exposed to hazards. This study attempts to identify, health and safety practices prevailing in road construction projects, issues and propose measures to mitigate.The study was confined to seven contract packages implemented under Northern Road Connectivity Project (Additional Financing) funded by Asian Development Bank (ADB). Five of them were located in the North Central Province while the other two were in Northern Province. Data was gathered through questionnaires, interviews and observations. Questionnaire comprised six major criteria, namely, training and supervision, safe work procedures, communication, reporting safety, management commitment and injury and return to work. Study revealed that workers are exposed to hazards of frequent and heavy lifting, noise and vibration, hazardous substances such as oil, gas, hydraulic fluid, welding fumes, heavy vehicle operation, working in blasting faces, clearing operations, slips, trips and falls, struck by, being struck by falling objects, hand-arm-whole body vibration, dust, sources of noise, electrical hazards etc. In asphalting areas workers are exposed to high temperatures and Polycyclic Aromatic Hydro Carbons (PAHC) which are carcinogenic. Working in excavated areas is prone to collapse of slopes. Workers are also prone to ergonomic issues caused due to manual handling and awkward postures. Main causes of accidents have been identified as fall from height, fall of objects, struck on stationary objects, struck by moving objects, struck on moving objects, caught in between, exposure to heat, exposure to electricity and exposure to harmful substances. Information gathered from 250 respondents revealed a high positive response in overall health and safety management practices. Five of the six criteria concerned showed a high positive response of greater than 78 percent. Communication recorded the lowest. Contract package wise comparison shows that P3 and P4 had a low positive response in the criteria concerned other than management commitment. Interviews conducted with Project Managers revealed a high commitment. Safety Committees were nonexistent in six of the seven packages except (P2). Observations revealed safety lapses such as working without PPE, working under unsafe conditions, non barricading hazardous zones, lack of warning sign boards and deploying non competent flagmen etc. It is recommended to conduct awareness programmes through Labour Department Officials prior to commencement of construction work, qualified Safety Officers should be employed, sites should be thoroughly inspected to eradicate hazards, work zones should be safe for workers, consultant’s field staff should check adequacy of precautionary measures, importance of PPE should be emphasized, hazard areas should be properly barricaded, trained flagman should be deployed, records of toolbox meetings should be maintained, near misses should be recorded, Safety Policy should be accessible to all workers, officials from the Labour Department should visit the sites to check compliance

The Astropy Problem

The Astropy Project (http://astropy.org) is, in its own words, "a community effort to develop a single core package for Astronomy in Python and foster interoperability between Python astronomy packages." For five years this project has been managed, written, and operated as a grassroots, self-organized, almost entirely volunteer effort while the software is used by the majority of the astronomical community. Despite this, the project has always been and remains to this day effectively unfunded. Further, contributors receive little or no formal recognition for creating and supporting what is now critical software. This paper explores the problem in detail, outlines possible solutions to correct this, and presents a few suggestions on how to address the sustainability of general purpose astronomical software

The Lyman alpha reference sample. II. Hubble space telescope imaging results, integrated properties, and trends

We report new results regarding the Lyα output of galaxies, derived from the Lyman Alpha Reference Sample, and focused on Hubble Space Telescope imaging. For 14 galaxies we present intensity images in Lyα, Hα, and UV, and maps of Hα/Hβ, Lyα equivalent width (EW), and Lyα/Hα. We present Lyα and UV radial light profiles and show they are well-fitted by Sérsic profiles, but Lyα profiles show indices systematically lower than those of the UV (n ≈ 1-2 instead of gsim 4). This reveals a general lack of the central concentration in Lyα that is ubiquitous in the UV. Photometric growth curves increase more slowly for Lyα than the far ultraviolet, showing that small apertures may underestimate the EW. For most galaxies, however, flux and EW curves flatten by radii ≈10 kpc, suggesting that if placed at high-z only a few of our galaxies would suffer from large flux losses. We compute global properties of the sample in large apertures, and show total Lyα luminosities to be independent of all other quantities. Normalized Lyα throughput, however, shows significant correlations: escape is found to be higher in galaxies of lower star formation rate, dust content, mass, and nebular quantities that suggest harder ionizing continuum and lower metallicity. Six galaxies would be selected as high-z Lyα emitters, based upon their luminosity and EW. We discuss the results in the context of high-z Lyα and UV samples. A few galaxies have EWs above 50 Å, and one shows $f_\mathrm{esc}^{\mathrm{Ly}\alpha }$ of 80%; such objects have not previously been reported at low-z

The Lyα Properties of Faint Galaxies at z ~ 2-3 with Systemic Redshifts and Velocity Dispersions from Keck-MOSFIRE

We study the Lyα profiles of 36 spectroscopically detected Lyα-emitters (LAEs) at z ~ 2-3, using Keck MOSFIRE to measure systemic redshifts and velocity dispersions from rest-frame optical nebular emission lines. The sample has a median optical magnitude R = 26.0, and ranges from R ≃ 23 to R > 27, corresponding to rest-frame UV absolute magnitudes M _(UV) ≃ –22 to M ^(UV) > –18.2. Dynamical masses range from M_(dyn) 3σ significance: brighter galaxies with larger velocity dispersions tend to have larger values of Δv Lyα. We also make use of a comparison sample of 122 UV-color-selected R < 25.5 galaxies at z ~ 2, all with Lyα emission and systemic redshifts measured from nebular emission lines. Using the combined LAE and comparison samples for a total of 158 individual galaxies, we find that Δv_(Lyα) is anti-correlated with the Lyα equivalent width with 7σ significance. Our results are consistent with a scenario in which the Lyα profile is determined primarily by the properties of the gas near the systemic redshift; in such a scenario, the opacity to Lyα photons in lower mass galaxies may be reduced if large gaseous disks have not yet developed and if the gas is ionized by the harder spectrum of young, low metallicity stars

The Metagenome of an Anaerobic Microbial Community Decomposing Poplar Wood Chips

This study describes the composition and metabolic potential of a lignocellulosic biomass degrading community that decays poplar wood chips under anaerobic conditions. We examined the community that developed on poplar biomass in a non-aerated bioreactor over the course of a year, with no microbial inoculation other than the naturally occurring organisms on the woody material. The composition of this community contrasts in important ways with biomass-degrading communities associated with higher organisms, which have evolved over millions of years into a symbiotic relationship. Both mammalian and insect hosts provide partial size reduction, chemical treatments (low or high pH environments), and complex enzymatic ‘secretomes’ that improve microbial access to cell wall polymers. We hypothesized that in order to efficiently degrade coarse untreated biomass, a spontaneously assembled free-living community must both employ alternative strategies, such as enzymatic lignin depolymerization, for accessing hemicellulose and cellulose and have a much broader metabolic potential than host-associated communities. This would suggest that such a community would make a valuable resource for finding new catalytic functions involved in biomass decomposition and gaining new insight into the poorly understood process of anaerobic lignin depolymerization. Therefore, in addition to determining the major players in this community, our work specifically aimed at identifying functions potentially involved in the depolymerization of cellulose, hemicelluloses, and lignin, and to assign specific roles to the prevalent community members in the collaborative process of biomass decomposition. A bacterium similar to Magnetospirillum was identified among the dominant community members, which could play a key role in the anaerobic breakdown of aromatic compounds. We suggest that these compounds are released from the lignin fraction in poplar hardwood during the decay process, which would point to lignin-modification or depolymerization under anaerobic conditions