New Constraints on the Escape of Ionizing Photons From Starburst Galaxies Using Ionization-Parameter Mapping

The fate of ionizing radiation in starburst galaxies is key to understanding cosmic reionization. However, the galactic parameters on which the escape fraction of ionizing radiation depend are not well understood. Ionization-parameter mapping provides a simple, yet effective, way to study the radiative transfer in starburst galaxies. We obtain emission-line ratio maps of [SIII]/[SII] for six, nearby, dwarf starbursts: NGC 178, NGC 1482, NGC 1705, NGC 3125, NGC 7126, and He 2-10. The narrow-band images are obtained with the Maryland-Magellan Tunable Filter at Las Campanas Observatory. Using these data, we previously reported the discovery of an optically thin ionization cone in NGC 5253, and here we also discover a similar ionization cone in NGC 3125. This latter cone has an opening angle of 40+/-5 degrees (0.4 ster), indicating that the passageways through which ionizing radiation may travel correspond to a small solid angle. Additionally, there are three sample galaxies that have winds and/or superbubble activity, which should be conducive to escaping radiation, yet they are optically thick. These results support the scenario that an orientation bias limits our ability to directly detect escaping Lyman continuum in many starburst galaxies. A comparison of the star-formation properties and histories of the optically thin and thick galaxies is consistent with the model that high escape fractions are limited to galaxies that are old enough (> 3 Myr) for mechanical feedback to have cleared optically thin passageways in the ISM, but young enough (< 5 Myr) that the ionizing stars are still present.Comment: Accepted for publication in Ap

An Ionization Cone in the Dwarf Starburst Galaxy NGC 5253

There are few observational constraints on how the escape of ionizing photons from starburst galaxies depends on galactic parameters. Here, we report on the first major detection of an ionization cone in NGC 5253, a nearby starburst galaxy. This high-excitation feature is identified by mapping the emission-line ratios in the galaxy using [S III] lambda 9069, [S II] lambda 6716, and H_alpha narrow-band images from the Maryland-Magellan Tunable Filter at Las Campanas Observatory. The ionization cone appears optically thin, which is suggestive of the escape of ionizing photons. The cone morphology is narrow with an estimated solid angle covering just 3% of 4pi steradians, and the young, massive clusters of the nuclear starburst can easily generate the radiation required to ionize the cone. Although less likely, we cannot rule out the possibility of an obscured AGN source. An echelle spectrum along the minor axis shows complex kinematics that are consistent with outflow activity. The narrow morphology of the ionization cone supports the scenario that an orientation bias contributes to the difficulty in detecting Lyman continuum emission from starbursts and Lyman break galaxies.Comment: 5 pages, 4 figures, Accepted to ApJ Letter

Genome sequence of canine herpesvirus

Canine herpesvirus is a widespread alphaherpesvirus that causes a fatal haemorrhagic disease of neonatal puppies. We have used high-throughput methods to determine the genome sequences of three viral strains (0194, V777 and V1154) isolated in the United Kingdom between 1985 and 2000. The sequences are very closely related to each other. The canine herpesvirus genome is estimated to be 125 kbp in size and consists of a unique long sequence (97.5 kbp) and a unique short sequence (7.7 kbp) that are each flanked by terminal and internal inverted repeats (38 bp and 10.0 kbp, respectively). The overall nucleotide composition is 31.6% G+C, which is the lowest among the completely sequenced alphaherpesviruses. The genome contains 76 open reading frames predicted to encode functional proteins, all of which have counterparts in other alphaherpesviruses. The availability of the sequences will facilitate future research on the diagnosis and treatment of canine herpesvirus-associated disease

The Effect of Discovery Systems on Online Journal Usage: A Longitudinal Study

Many academic libraries are implementing discovery services as a way of giving their users a single comprehensive search option for all library resources. These tools are designed to change the research experience, yet very few studies have investigated the impact of discovery service implementation. This study examines one aspect of that impact by asking whether usage of publisher-hosted journal content changes after implementation of a discovery tool. Libraries that have begun using the four major discovery services have seen an increase in usage of this content, suggesting that for this particular type of material, discovery services have a positive impact on use. Though all discovery services significantly increased usage relative to a no discovery service control group, some had a greater impact than others, and there was extensive variation in usage change among libraries using the same service. Future phases of this study will look at other types of content

The Effect of Discovery Systems on Online Journal Usage: A Longitudinal Study

Many academic libraries are implementing discovery services as a way of giving their users a single comprehensive search option for all library resources. These tools are designed to change the research experience, yet very few studies have investigated the impact of discovery service implementation. This study examines one aspect of that impact by asking whether usage of publisher-hosted journal content changes after implementation of a discovery tool. Libraries that have begun using the four major discovery services have seen an increase in usage of this content, suggesting that for this particular type of material, discovery services have a positive impact on use. Though all discovery services significantly increased usage relative to a no discovery service control group, some had a greater impact than others, and there was extensive variation in usage change among libraries using the same service. Future phases of this study will look at other types of content

IDCS J1426.5+3508: The Most Massive Galaxy Cluster at z>1.5z > 1.5

We present a deep (100 ks) Chandra observation of IDCS J1426.5+3508, a spectroscopically confirmed, infrared-selected galaxy cluster at $z = 1.75$. This cluster is the most massive galaxy cluster currently known at $z > 1.5$, based on existing Sunyaev-Zel'dovich (SZ) and gravitational lensing detections. We confirm this high mass via a variety of X-ray scaling relations, including $T_X$-M, $f_g$-M, $Y_X$-M and $L_X$-M, finding a tight distribution of masses from these different methods, spanning M$_{500}$ = 2.3-3.3 $\times 10^{14}$ M$_{\odot}$, with the low-scatter $Y_X$-based mass $M_{500,Y_X} = 2.6^{+1.5}_{-0.5} \times 10^{14}$ M$_\odot$. IDCS J1426.5+3508 is currently the only cluster at $z > 1.5$ for which X-ray, SZ and gravitational lensing mass estimates exist, and these are in remarkably good agreement. We find a relatively tight distribution of the gas-to-total mass ratio, employing total masses from all of the aforementioned indicators, with values ranging from $f_{gas,500}$ = 0.087-0.12. We do not detect metals in the intracluster medium (ICM) of this system, placing a 2$\sigma$ upper limit of $Z(r < R_{500}) < 0.18 Z_{\odot}$. This upper limit on the metallicity suggests that this system may still be in the process of enriching its ICM. The cluster has a dense, low-entropy core, offset by $\sim$30 kpc from the X-ray centroid, which makes it one of the few "cool core" clusters discovered at $z > 1$, and the first known cool core cluster at $z > 1.2$. The offset of this core from the large-scale centroid suggests that this cluster has had a relatively recent ($\lesssim$500 Myr) merger/interaction with another massive system.Comment: Minor changes to match accepted version, results unchanged; ApJ in pres

Underpowered Aircraft - Performance and Operational Possibilities

A unique configuration, known as an Underpowered Aircraft, allows for the modification of gliding flight vehicles for increased range and lower cost when compared with fully powered flight vehicles. Intentionally under-sizing the powerplant for a flight vehicle allows the designer to choose a powerplant that will not only perform the mission requirements, but will also provide the customer with the most cost effective solution, as some missions may not require fully powered flight. Specifically, the underpowered aircraft concept studied in this paper is a gliding flight aircraft that does not have enough power for climbing or level flight, but does have enough power to overcome some of the drag forces associated with flight, in turn increasing the effective range of the vehicle. In this paper, the underpowered aircraft concept was analyzed and its feasibility was determined. Analysis done using equations of motion, followed by a more accurate numerical integration including a thrust lapse, determined that the underpowered aircraft concept provides a unique method for a cost effective range extension technology for gliding flight vehicles. Finally, the technology and methods of this paper were applied to the AGM-154 JSOW and JSOW-ER glide munitions and it was determined that JSOW-ER is representative of an underpowered aircraft with our analysis. This paper represents a back-of-the-envelope investigation into the underpowered aircraft concept

Strong Lensing Model of SPT-CLJ0356-5337, a Major Merger Candidate at Redshift 1.0359

We present an analysis of the mass distribution inferred from strong lensing by SPT-CL J0356-5337, a cluster of galaxies at redshift z = 1.0359 revealed in the follow-up of the SPT-SZ clusters. The cluster has an Einstein radius of Erad=14 for a source at z = 3 and a mass within 500 kpc of M_500kpc = 4.0+-0.8x10^14Msol. Our spectroscopic identification of three multiply-imaged systems (z = 2.363, z = 2.364, and z = 3.048), combined with HST F606W-band imaging allows us to build a strong lensing model for this cluster with an rms of <0.3'' between the predicted and measured positions of the multiple images. Our modeling reveals a two-component mass distribution in the cluster. One mass component is dominated by the brightest cluster galaxy and the other component, separated by ~170 kpc, contains a group of eight red elliptical galaxies confined in a ~9'' (~70 kpc) diameter circle. We estimate the mass ratio between the two components to be between 1:1.25 and 1:1.58. In addition, spectroscopic data reveal that these two near-equal mass cores have only a small velocity difference of 300 km/s between the two components. This small radial velocity difference suggests that most of the relative velocity takes place in the plane of the sky, and implies that SPT-CL J0356-5337 is a major merger with a small impact parameter seen face-on. We also assess the relative contributions of galaxy-scale halos to the overall mass of the core of the cluster and find that within 800 kpc from the brightest cluster galaxy about 27% of the total mass can be attributed to visible and dark matter associated with galaxies, whereas only 73% of the total mass in the core comes from cluster-scale dark matter halos.Comment: 19 pages, 11 figures. Submitted to Ap

Acute toxicity in comprehensive head and neck radiation for nasopharynx and paranasal sinus cancers: cohort comparison of 3D conformal proton therapy and intensity modulated radiation therapy.

Background: To evaluate acute toxicity endpoints in a cohort of patients receiving head and neck radiation with proton therapy or intensity modulated radiation therapy (IMRT). Methods: Forty patients received comprehensive head and neck radiation including bilateral cervical nodal radiation, given with or without chemotherapy, for tumors of the nasopharynx, nasal cavity or paranasal sinuses, any T stage, N0-2. Fourteen received comprehensive treatment with proton therapy, and 26 were treated with IMRT, either comprehensively or matched to proton therapy delivered to the primary tumor site. Toxicity endpoints assessed included g-tube dependence at the completion of radiation and at 3 months after radiation, opioid pain medication requirement compared to pretreatment normalized as equivalent morphine dose (EMD) at completion of treatment, and at 1 and 3 months after radiation. Results: In a multivariable model including confounding variables of concurrent chemotherapy and involved nodal disease, comprehensive head and neck radiation therapy using proton therapy was associated with a lower opioid pain requirement at the completion of radiation and a lower rate of gastrostomy tube dependence by the completion of radiation therapy and at 3 months after radiation compared to IMRT. Proton therapy was associated with statistically significant lower mean doses to the oral cavity, esophagus, larynx, and parotid glands. In subgroup analysis of 32 patients receiving concurrent chemotherapy, there was a statistically significant correlation with a greater opioid pain medication requirement at the completion of radiation and both increasing mean dose to the oral cavity and to the esophagus. Conclusions: Proton therapy was associated with significantly reduced radiation dose to assessed non-target normal tissues and a reduced rate of gastrostomy tube dependence and opioid pain medication requirements. This warrants further evaluation in larger studies, ideally with patient-reported toxicity outcomes and quality of life endpoints