ULTRAVIOLET PROPERTIES OF GALACTIC GLOBULAR CLUSTERS WITH GALEX. II. INTEGRATED COLORS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dalessandro, Emanuele; Ferraro, Francesco R.; Lanzoni, Barbara

2012-11-01

We present ultraviolet (UV) integrated colors of 44 Galactic globular clusters (GGCs) observed with the Galaxy Evolution Explorer (GALEX) in both FUV and NUV bands. This database is the largest homogeneous catalog of UV colors ever published for stellar systems in our Galaxy. The proximity of GGCs makes it possible to resolve many individual stars even with the somewhat low spatial resolution of GALEX. This allows us to determine how the integrated UV colors are driven by hot stellar populations, primarily horizontal branch stars and their progeny. The UV colors are found to be correlated with various parameters commonly usedmore » to define the horizontal branch morphology. We also investigate how the UV colors vary with parameters like metallicity, age, helium abundance, and concentration. We find for the first time that GCs associated with the Sagittarius dwarf galaxy have (FUV - V) colors systematically redder than GGCs with the same metallicity. Finally, we speculate about the presence of an interesting trend, suggesting that the UV color of GCs may be correlated with the mass of the host galaxy, in the sense that more massive galaxies possess bluer clusters.« less

A Search for Rapidly Pulsating Hot Subdwarf Stars in the GALEX Survey

NASA Astrophysics Data System (ADS)

Boudreaux, Thomas M.; Barlow, Brad N.; Fleming, Scott W.; Vasquez Soto, Alan; Million, Chase; Reichart, Dan E.; Haislip, Josh B.; Linder, Tyler R.; Moore, Justin P.

2017-08-01

NASA’s Galaxy Evolution Explorer (GALEX) provided near- and far-UV observations for approximately 77% of the sky over a 10-year period; however, the data reduction pipeline initially only released single NUV and FUV images to the community. The recently released Python module gPhoton changes this, allowing calibrated time-series aperture photometry to be extracted easily from the raw GALEX data set. Here we use gPhoton to generate light curves for all hot subdwarf B (sdB) stars that were observed by GALEX, with the intention of identifying short-period, p-mode pulsations. We find that the spacecraft’s short visit durations, uneven gaps between visits, and dither pattern make the detection of hot subdwarf pulsations difficult. Nonetheless, we detect UV variations in four previously known pulsating targets and report their UV pulsation amplitudes and frequencies. Additionally, we find that several other sdB targets not previously known to vary show promising signals in their periodograms. Using optical follow-up photometry with the Skynet Robotic Telescope Network, we confirm p-mode pulsations in one of these targets, LAMOST J082517.99+113106.3, and report it as the most recent addition to the sdBV r class of variable stars.

A Search for Rapidly Pulsating Hot Subdwarf Stars in the GALEX Survey

DOE Office of Scientific and Technical Information (OSTI.GOV)

Boudreaux, Thomas M.; Barlow, Brad N.; Soto, Alan Vasquez

NASA’s Galaxy Evolution Explorer ( GALEX ) provided near- and far-UV observations for approximately 77% of the sky over a 10-year period; however, the data reduction pipeline initially only released single NUV and FUV images to the community. The recently released Python module gPhoton changes this, allowing calibrated time-series aperture photometry to be extracted easily from the raw GALEX data set. Here we use gPhoton to generate light curves for all hot subdwarf B (sdB) stars that were observed by GALEX , with the intention of identifying short-period, p-mode pulsations. We find that the spacecraft’s short visit durations, uneven gapsmore » between visits, and dither pattern make the detection of hot subdwarf pulsations difficult. Nonetheless, we detect UV variations in four previously known pulsating targets and report their UV pulsation amplitudes and frequencies. Additionally, we find that several other sdB targets not previously known to vary show promising signals in their periodograms. Using optical follow-up photometry with the Skynet Robotic Telescope Network, we confirm p-mode pulsations in one of these targets, LAMOST J082517.99+113106.3, and report it as the most recent addition to the sdBV{sub r} class of variable stars.« less

GALEX: a UV telescope to map the star formation history of the universe

NASA Astrophysics Data System (ADS)

Milliard, Bruno; Grange, Robert; Martin, Christopher; Schiminovich, David

2017-11-01

The NASA Small Mission EXplorer GALEX (PI: C.Martin, Caltech) is under development at JPL for launch late 2001. It has been designed to map the history of star formation in the Universe over the redshift range 0-2, a major era where galaxies and gas content evolved dramatically. The expected depth and imaging quality matches the Palomar Observatory Surveys, allowing GALEX to provide the astronomical community with a database of FUV photometric and spectroscopic observations of several million galaxies in the nearby and distant Universe. The 1.24 degree FOV, 50 cm aperture compact Ritchey-Chrétien telescope is equipped with two 65 mm photon-counting detectors. It will perform several surveys of different coverage and depths, that will take advantage of a high throughput UV-transmissive Grism newly developed in France to easily switch between imagery and field spectroscopy modes. A thin aspherized fused silica dichroic component provides simultaneous observations in two UV bands (135-185 nm and 185-300 nm) as well as correction for field aberrations. We shall briefly present the mission science goals, and will describe the optical concept, along with the guidelines and compromises used for its optimization in the context of the "Faster, Better, Cheaper" NASA philosophy, and give a brief development status report.

FUV Emission from AGB Stars: Modeling Accretion Activity Associated with a Binary Companion

NASA Technical Reports Server (NTRS)

Stevens, Alyx Catherine; Sahai, Raghvendra

2012-01-01

It is widely believed that the late stages of evolution for Asymptotic Giant Branch (AGB) stars are influenced by the presence of binary companions. Unfortunately, there is a lack of direct observational evidence of binarity. However, more recently, strong indirect evidence comes from the discovery of UV emission in a subsample of these objects (fuvAGB stars). AGB stars are comparatively cool objects (< or =3000 K), thus their fluxes falls off drastically for wavelengths 3000 Angstroms and shorter. Therefore, ultraviolet observations offer an important, new technique for detecting the binary companions and/or associated accretion activity. We develop new models of UV emission from fuvAGB stars constrained by GALEX photometry and spectroscopy of these objects. We compare the GALEX UV grism spectra of the AGB M7 star EY Hya to predictions using the spectral synthesis code Cloudy, specifically investigating the ultraviolet wavelength range (1344-2831 Angstroms). We investigate models composed of contributions from a photoionized "hot spot" due to accretion activity around the companion, and "chromospheric" emission from collisionally ionized plasma, to fit the UV observations.

Probing the infrared counterparts of diffuse far-ultraviolet sources in the Galaxy

NASA Astrophysics Data System (ADS)

Saikia, Gautam; Shalima, P.; Gogoi, Rupjyoti; Pathak, Amit

2017-12-01

Recent availability of high quality infrared (IR) data for diffuse regions in the Galaxy and external galaxies have added to our understanding of interstellar dust. A comparison of ultraviolet (UV) and IR observations may be used to estimate absorption, scattering and thermal emission from interstellar dust. In this paper, we report IR and UV observations for selective diffuse sources in the Galaxy. Using archival mid-infrared (MIR) and far-infrared (FIR) observations from Spitzer Space Telescope, we look for counterparts of diffuse far-ultraviolet (FUV) sources observed by the Voyager, Far Ultraviolet Spectroscopic Explorer (FUSE) and Galaxy Evolution Explorer (GALEX) telescopes in the Galaxy. IR emission features at 8 μm are generally attributed to Polycyclic Aromatic Hydrocarbon (PAH) molecules, while emission at 24 μm are attributed to Very Small Grains (VSGs). The data presented here is unique and our study tries to establish a relation between various dust populations. By studying the FUV-IR correlations separately at low and high latitude locations, we have identified the grain component responsible for the diffuse FUV emission.

Flare Frequency Distribution at Low Energies in GALEX UV

NASA Astrophysics Data System (ADS)

Million, Chase; Fleming, Scott W.; Osten, Rachel A.; Brasseur, Clara; Bianchi, Luciana; Shiao, Bernie; Loyd, R. O. Parke; Shkolnik, Evgenya L.

2018-06-01

The gPhoton toolkit and database of GALEX photon events permits measurement of flares with energies as small as ~10^27 ergs in the two GALEX UV bandpasses. Following a previously reported search for flaring on several thousand M dwarfs observed by GALEX, we present initial results on the flare frequency as a function of energy and stellar type at energies < 10^32 ergs.

A GALEX-BASED SEARCH FOR THE SPARSE YOUNG STELLAR POPULATION IN THE TAURUS-AURIGAE STAR FORMING REGION

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gómez de Castro, Ana I.; Lopez-Santiago, Javier; López-Martínez, Fatima

2015-02-01

In this work, we identify 63 bona fide new candidates to T Tauri stars (TTSs) in the Taurus-Auriga region, using its ultraviolet excess as our baseline. The initial data set was defined from the GALEX all sky survey (AIS). The GALEX satellite obtained images in the near-ultraviolet (NUV) and far-ultraviolet (FUV) bands where TTSs show a prominent excess compared with main-sequence or giants stars. GALEX AIS surveyed the Taurus-Auriga molecular complex, as well as a fraction of the California Nebula and the Perseus complex; bright sources and dark clouds were avoided. The properties of TTSs in the ultraviolet (GALEX), opticalmore » (UCAC4), and infrared (2MASS) have been defined using the TTSs observed with the International Ultraviolet Explorer reference sample. The candidates were identified by means of a mixed ultraviolet-optical-infrared excess set of colors; we found that the FUV-NUV versus J–K color-color diagram is ideally suited for this purpose. From an initial sample of 163,313 bona fide NUV sources, a final list of 63 new candidates to TTSs in the region was produced. The search procedure has been validated by its ability to detect all known TTSs in the area surveyed: 31 TTSs. Also, we show that the weak-lined TTSs are located in a well-defined stripe in the FUV-NUV versus J–K diagram. Moreover, in this work, we provide a list of TTSs photometric standards for future GALEX-based studies of the young stellar population in star forming regions.« less

CCM in the FUV

NASA Astrophysics Data System (ADS)

Cartledge, S. I. B.; Clayton, G. C.; Gordon, K. D.

2005-12-01

Over 90% of Milky Way extinction curves sampled from IR through UV wavelengths (UV coverage by IUE) conform to the CCM family of curves based on R(V), a single parameter linked to grain size. The far-ultraviolet (FUV) portion of this formulation, however, was based only on a few sight lines observed by Copernicus, and it has recently been shown that in certain cases CCM does not predict extinction in the FUV as accurately as it does at longer wavelengths. In this poster paper, we present preliminary results from our examination of the agreement between all publicly-available FUSE FUV spectra of reddened O and B stars and their corresponding extinction curves inferred from longer wavelength fluxes. The eventual goal of our project is to reformulate CCM, particularly in the FUV where we have compiled more than 90 sight lines observed by FUSE. We are also exploring correlations between bulk sight line properties and the form of the reconstituted CCM curves.

GALEX UV grism for slitless spectroscopy survey

NASA Astrophysics Data System (ADS)

Grange, Robert; Milliard, Bruno; Flamand, Jean; Pauget, Alain; Waultier, Gabrielle; Moreaux, Gabriel; Rossin, Christelle; Viton, Maurice; Neviere, Michel

2017-11-01

The NASA Space Mission Galex is designed to map the history of star formation by performing imaging and spectroscopic surveys in vacuum ultraviolet. The dispersive component for the spectroscopic mode is a CaF2 Grism which can be inserted with loose tolerances in the convergent beam to produce slitless spectra. Grisms are widely used in ground based astronomy in the visible or near infrared bands but the UV cutoff of the resin involved in their manufacturing process prevents their use in the UV range. LAS and Jobin-Yvon developed a proprietary process to imprint the blazed profile into the CaF2 crystal. We will present the measured optical performance of prototypes and flight models delivered this summer to NASA/JPL. We will also present a three bipod flexures mount we designed to minimize the mechanical stress on the optical component. The flight Grism bonded to such a mount has successfully passed the Galex environmental qualification.

The effects of the WISE/ GALEX photometry for the SED-fitting with M31 star clusters and candidates

NASA Astrophysics Data System (ADS)

Fan, Zhou; Wang, Song

2017-10-01

Spectral energy distribution (SED) fitting of stellar population synthesis models is an important and popular way to constrain the physical parameters—e.g., the ages, metallicities, masses for stellar population analysis. The previous works suggest that both blue-bands and red-bands photometry works for the SED-fitting. Either blue-domained or red-domained SED-fitting usually lead to the unreliable or biased results. Meanwhile, it seems that extending the wavelength coverage could be helpful. Since the Galaxy Evolution Explorer ( GALEX) and Wide-field Infrared Survey Explorer (WISE) provide the FUV/NUV and mid-infrared W1/W2 band data, we extend the SED-fitting to a wider wavelength coverage. In our work, we analyzed the effect of adding the FUV/NUV and W1/W2 band to the optical and near-infrared UBVRIJHK bands for the fitting with the (Bruzual and Charlot in Mon. Not. R. Astron. Soc. 344, 1000, 2003) (BC03) models and galev models. It is found that the FUV/NUV bands data affect the fitting results of both ages and metallicities much more significantly than that of the WISE W1/W2 band with the BC03 models. While for the galev models, the effect of the WISE W1/W2 band for the metallicity fitting seems comparable to that of GALEX FUV/NUV bands, but for age the effect of the W1/W2 band seems less crucial than that of the FUV/NUV bands. Thus we conclude that the GALEX FUV/NUV bands are more crucial for the SED-fitting of ages and metallicities, than the other bands, and the high-quality UV data (with high photometry precision) are required.

The GALEX/S4G Surface Brightness and Color Profiles Catalog. I. Surface Photometry and Color Gradients of Galaxies

NASA Astrophysics Data System (ADS)

Bouquin, Alexandre Y. K.; Gil de Paz, Armando; Muñoz-Mateos, Juan Carlos; Boissier, Samuel; Sheth, Kartik; Zaritsky, Dennis; Peletier, Reynier F.; Knapen, Johan H.; Gallego, Jesús

2018-02-01

We present new spatially resolved surface photometry in the far-ultraviolet (FUV) and near-ultraviolet (NUV) from images obtained by the Galaxy Evolution Explorer (GALEX) and IRAC1 (3.6 μm) photometry from the Spitzer Survey of Stellar Structure in Galaxies (S4G). We analyze the radial surface brightness profiles μ FUV, μ NUV, and μ [3.6], as well as the radial profiles of (FUV ‑ NUV), (NUV ‑ [3.6]), and (FUV ‑ [3.6]) colors in 1931 nearby galaxies (z < 0.01). The analysis of the 3.6 μm surface brightness profiles also allows us to separate the bulge and disk components in a quasi-automatic way and to compare their light and color distribution with those predicted by the chemo-spectrophotometric models for the evolution of galaxy disks of Boissier & Prantzos. The exponential disk component is best isolated by setting an inner radial cutoff and an upper surface brightness limit in stellar mass surface density. The best-fitting models to the measured scale length and central surface brightness values yield distributions of spin and circular velocity within a factor of two of those obtained via direct kinematic measurements. We find that at a surface brightness fainter than μ [3.6] = 20.89 mag arcsec‑2, or below 3 × 108 M ⊙ kpc‑2 in stellar mass surface density, the average specific star formation rate (sSFR) for star-forming and quiescent galaxies remains relatively flat with radius. However, a large fraction of GALEX Green Valley galaxies show a radial decrease in sSFR. This behavior suggests that an outside-in damping mechanism, possibly related to environmental effects, could be testimony of an early evolution of galaxies from the blue sequence of star-forming galaxies toward the red sequence of quiescent galaxies.

Aluminum Mirror Coatings for UVOIR Telescope Optics Including the Far UV

NASA Technical Reports Server (NTRS)

Balasubramanian, Kunjithapatha; Hennessy, John; Raouf, Nasrat; Nikzad, Shouleh; Ayala, Michael; Shaklan, Stuart; Scowen, Paul; Del Hoyo, Javier; Quijada, Manuel

2015-01-01

NASA Cosmic Origins (COR) Program identified the development of high reflectivity mirror coatings for large astronomical telescopes particularly for the far ultra violet (FUV) part of the spectrum as a key technology requiring significant materials research and process development. In this paper we describe the challenges and accomplishments in producing stable high reflectance aluminum mirror coatings with conventional evaporation and advanced Atomic Layer Deposition (ALD) techniques. We present the current status of process development with reflectance of approx. 55 to 80% in the FUV achieved with little or no degradation over a year. Keywords: Large telescope optics, Aluminum mirror, far UV astrophysics, ALD, coating technology development.

Searching for Young M Dwarfs with GALEX

NASA Astrophysics Data System (ADS)

Shkolnik, Evgenya L.; Liu, Michael C.; Reid, I. Neill; Dupuy, Trent; Weinberger, Alycia J.

2011-01-01

The census of young moving groups in the solar neighborhood is significantly incomplete in the low-mass regime. We have developed a new selection process to find these missing members based on the Galaxy Evolution Explorer (GALEX) All-Sky Imaging Survey (AIS). For stars with spectral types gsimK5 (R - J >~ 1.5) and younger than ≈300 Myr, we show that near-UV (NUV) and far-UV (FUV) emission is greatly enhanced above the quiescent photosphere, analogous to the enhanced X-ray emission of young low-mass stars seen by ROSAT but detectable to much larger distances with GALEX. By combining GALEX data with optical (HST Guide Star Catalog) and near-IR (2MASS) photometry, we identified an initial sample of 34 young M dwarf candidates in a 1000 deg2 region around the ≈10 Myr TW Hydra Association (TWA). Low-resolution spectroscopy of 30 of these found 16 which had Hα in emission, which were then followed up at high resolution to search for spectroscopic evidence of youth and to measure their radial velocities. Four objects have low surface gravities, photometric distances and space motions consistent with TWA, but the non-detection of Li indicates that they may be too old to belong to this moving group. One object (M3.5, 93 ± 19 pc) appears to be the first known accreting low-mass member of the ≈15 Myr Lower Centaurus Crux OB association. Two objects exhibit all the characteristics of the known TWA members, and thus we designate them as TWA 31 (M4.2, 110 ± 11 pc) and TWA 32 (M6.3, 53 ± 5 pc). TWA 31 shows extremely broad (447 km s-1) Hα emission, making it the sixth member of TWA found to have ongoing accretion. TWA 32 is resolved into a 0farcs6 binary in Keck laser guide star adaptive optics imaging. Our search should be sensitive down to spectral types of at least M4-M5 in TWA and thus the small numbers of new member is puzzling. This might indicate TWA has an atypical mass function or that the presence of lithium absorption may be too restrictive a criteria for

Near-UV Sources in the Hubble Ultra Deep Field: The Catalog

NASA Technical Reports Server (NTRS)

Gardner, Jonathan P.; Voyrer, Elysse; de Mello, Duilia F.; Siana, Brian; Quirk, Cori; Teplitz, Harry I.

2009-01-01

The catalog from the first high resolution U-band image of the Hubble Ultra Deep Field, taken with Hubble s Wide Field Planetary Camera 2 through the F300W filter, is presented. We detect 96 U-band objects and compare and combine this catalog with a Great Observatories Origins Deep Survey (GOODS) B-selected catalog that provides B, V, i, and z photometry, spectral types, and photometric redshifts. We have also obtained Far-Ultraviolet (FUV, 1614 Angstroms) data with Hubble s Advanced Camera for Surveys Solar Blind Channel (ACS/SBC) and with Galaxy Evolution Explorer (GALEX). We detected 31 sources with ACS/SBC, 28 with GALEX/FUV, and 45 with GALEX/NUV. The methods of observations, image processing, object identification, catalog preparation, and catalog matching are presented.

Deep UV Luminosity Functions at the Infall Region of the Coma Cluster

NASA Technical Reports Server (NTRS)

Hammer, D. M.; Hornschemeier, A. E.; Salim, S.; Smith, R.; Jenkins, L.; Mobasher, B.; Miller, N.; Ferguson, H.

2011-01-01

We have used deep GALEX observations at the infall region of the Coma cluster to measure the faintest UV luminosity functions (LFs) presented for a rich galaxy cluster thus far. The Coma UV LFs are measured to M(sub uv) = -10.5 in the GALEX FUV and NUV bands, or 3.5 mag fainter than previous studies, and reach the dwarf early-type galaxy population in Coma for the first time. The Schechter faint-end slopes (alpha approximately equal to -1.39 in both GALEX bands) are shallower than reported in previous Coma UV LF studies owing to a flatter LF at faint magnitudes. A Gaussian-plus-Schechter model provides a slightly better parametrization of the UV LFs resulting in a faint-end slope of alpha approximately equal to -1.15 in both GALEX bands. The two-component model gives faint-end slopes shallower than alpha = -1 (a turnover) for the LFs constructed separately for passive and star forming galaxies. The UV LFs for star forming galaxies show a turnover at M(sub UV) approximately equal to -14 owing to a deficit of dwarf star forming galaxies in Coma with stellar masses below M(sub *) = 10(sup 8) solar mass. A similar turnover is identified in recent UV LFs measured for the Virgo cluster suggesting this may be a common feature of local galaxy clusters, whereas the field UV LFs continue to rise at faint magnitudes. We did not identify an excess of passive galaxies as would be expected if the missing dwarf star forming galaxies were quenched inside the cluster. In fact, the LFs for both dwarf passive and star forming galaxies show the same turnover at faint magnitudes. We discuss the possible origin of the missing dwarf star forming galaxies in Coma and their expected properties based on comparisons to local field galaxies.

New science catalogs of UV sources from the GALEX sky surveys, matched to optical-IR surveys. Related science tools, models, and first results on the characterization of evolved Galactic stellar populations.

NASA Astrophysics Data System (ADS)

Bianchi, Luciana; Shiao, Bernie; Thilker, David; Barr, Robert; Girardi, Leo

2018-01-01

GUVcat is a new, expanded and improved catalog of Ultraviolet (UV) sources from the GALEX surveys (Bianchi et al. 2017, ApJ Suppl, 230, 24; arXiv:1704.05903). It contains 83million unique sources measured in FUV and NUV (duplicate measurements and rim artifacts removed) at AIS depth (about FUV < 20, NUV<20.8 ABmag). It covers an area of 24,790 sq.deg., larger than that of previous versions (e.g., Bianchi et al. 2011 MNRAS 411, 2770; Bianchi et al.2014 J. ASR. 53, 900). In GUVcat we cured 640 fields improperly coadded by the GALEX pipeline, and implemented other improvements and new tags, e.g. to mark sources in the footprint of nearby extended galaxies or crowded clusters.The UV unique-source catalog facilitates studies of density of sources, and matching with catalogs at other wavelegths. We matched GUVcat with SDSS and Pan-STARRS surveys, which provide five optical bands each, and used the UV-to-optical colors to classify sources by astrophysical class, and to characterize classes of stellar sources to which UV data are uniquely sensitive, such as hot white dwarfs (WD), including elusive types of binaries. We compared the content of Galactic sources with Milky Way models, computed with different prescriptions. We also matched GUVcat with the first Gaia source and Gaia TGAS releases, which add precise position and G-band photometry for the bright sources, and direct distance measurements for a few very bright sources. GALEX spectra are also available and included in the analysis. Follow-up observations with HST are ongoing for an exploratory subsample.The source catalogs and related tools are available from the uvsky web site http://dolomiti.pha.jhu.edu/uvsky/#GUVcat . GUVcat_AIS is also available from MAST casjobs and soon from Vizier. A useful tool for calculating the effective area coverage of GUVcat, and of the matched catalogs, in user-chosen regions of the sky, is also available at the above url.Acknowledgements: Partial support for this work was provided by

The Ultraviolet Sky: classification and properties of UV sources from the GALEX surveys

NASA Astrophysics Data System (ADS)

Bianchi, L.; Rodriguez, L.; Herald, J.; Efremova, B.; GALEX Team

2005-12-01

We use UV imaging data from the GALEX (Galaxy Evolution Explorer) surveys, matched to other surveys at longer wavelengths, to classify sources and infer their physical parameters by comparing their measured UV - optical - IR colors to model colors. Our results significantly increase the statistics of some classes of astrophysical objects, such as Milky Way (MW) hot stars and low-redshift QSOs, and provide an unprecedented census of White Dwarfs in the MW. Results from follow-up spectroscopy of UV-selected sources are also presented. (see http://dolomiti.pha.jhu.edu for details ) We gratefully acknowledge NASA's support for construction, operation and data analysis of the GALEX mission, developed in cooperation with the French CNES and Korean Ministry of Science and Technology.

Lyman Limit Absorbers in GALEX Spectra

NASA Astrophysics Data System (ADS)

Williger, Gerard M.; Haberzettl, Lutz G.; Ribaudo, Joseph; Kuchner, Marc J.; Burchett, Joseph; Clowes, Roger G.; Lauroesch, James T.; Mills, Brianna; Borden, Jeremy

2018-01-01

We describe the method and early results for crowdsourcing a search for low-redshift partial and complete Lyman Limit Systems (pLLSs and LLSs) in the GALEX spectral archive. LLSs have been found in large numbers at z>3 and traced to lower redshift through a relatively small number of QSO spectra from spaced-based telescopes. From a sample of 44 pLLSs and 11 LLSs at 0.1far-UV, there is an indication that the metallicity distribution of partial LLSs is bimodal at z<1, with the high-metallicity portion centered at <[X/H]> = -0.32 +/- 0.07 and the low-metallicity portion centered at <[X/H]> = -1.87 +/- 0.11.The GALEX spectral archive offers a vast dataset potentially containing hundreds of LLSs, which may be leveraged to search for such a bimodality and track its evolution within the unconstrained near-UV gap at 1GALEX data coverage and signal-to-noise ratio are highly variable, which hampers an automated search. We have therefore begun crowdsourcing a subset of the GALEX archive for LLSs and pLLSs via a Zooniverse project. Initially, undergraduate physics majors are performing a pilot project before releasing to citizen scientists in the public at large. We will then vet candidate systems and estimate column densities in a follow-up analysis. Upon assessing the accuracy of the physics majors’ identifications, the results will be used to devise a larger program with the help of the general public. The resulting data set would then provide the best available link between the HST-selected far-UV and ground-based pLLS+LLS samples and provide an ideal sample for consequent metallicity determinations.

GALEX Study of the UV Variability of Nearby Galaxies and a Deep Probe of the UV Luminosity Function

NASA Technical Reports Server (NTRS)

Schlegel, Eric

2005-01-01

The proposal has two aims - a deep exposure of NGC 300, about a factor of 10 deeper than the GALEX all-sky survey; and an examination of the UV variability. The data were received just prior to a series of proposal deadlines in early spring. A subsequent analysis delay includes a move from SAO to the University of Texas - San Antonio. Nevertheless, we have merged the data into a single deep exposure as well as undertaking a preliminary examination of the variability. No UV halo is present as detected in the GALEX observation of M83. No UV bursts are visible; however a more stringent limit will only be obtained through a differencing of the sub-images. Papers: we expect 2 papers at about 12 pages/paper to flow from this project. The first paper will report on the time variability while the second will focus on the deep UV image obtained from stacking the individual observations.

SEARCHING FOR YOUNG M DWARFS WITH GALEX

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shkolnik, Evgenya L.; Weinberger, Alycia J.; Liu, Michael C.

2011-01-20

The census of young moving groups in the solar neighborhood is significantly incomplete in the low-mass regime. We have developed a new selection process to find these missing members based on the Galaxy Evolution Explorer (GALEX) All-Sky Imaging Survey (AIS). For stars with spectral types {approx}>K5 (R - J {approx}> 1.5) and younger than {approx}300 Myr, we show that near-UV (NUV) and far-UV (FUV) emission is greatly enhanced above the quiescent photosphere, analogous to the enhanced X-ray emission of young low-mass stars seen by ROSAT but detectable to much larger distances with GALEX. By combining GALEX data with optical (HSTmore » Guide Star Catalog) and near-IR (2MASS) photometry, we identified an initial sample of 34 young M dwarf candidates in a 1000 deg{sup 2} region around the {approx}10 Myr TW Hydra Association (TWA). Low-resolution spectroscopy of 30 of these found 16 which had H{alpha} in emission, which were then followed up at high resolution to search for spectroscopic evidence of youth and to measure their radial velocities. Four objects have low surface gravities, photometric distances and space motions consistent with TWA, but the non-detection of Li indicates that they may be too old to belong to this moving group. One object (M3.5, 93 {+-} 19 pc) appears to be the first known accreting low-mass member of the {approx}15 Myr Lower Centaurus Crux OB association. Two objects exhibit all the characteristics of the known TWA members, and thus we designate them as TWA 31 (M4.2, 110 {+-} 11 pc) and TWA 32 (M6.3, 53 {+-} 5 pc). TWA 31 shows extremely broad (447 km s{sup -1}) H{alpha} emission, making it the sixth member of TWA found to have ongoing accretion. TWA 32 is resolved into a 0.''6 binary in Keck laser guide star adaptive optics imaging. Our search should be sensitive down to spectral types of at least M4-M5 in TWA and thus the small numbers of new member is puzzling. This might indicate TWA has an atypical mass function or that the presence

An Ultraviolet Investigation of Activity on Exoplanet Host Stars

NASA Astrophysics Data System (ADS)

Shkolnik, Evgenya L.

2013-03-01

Using the far-UV (FUV) and near-UV (NUV) photometry from the NASA Galaxy Evolution Explorer (GALEX), we searched for evidence of increased stellar activity due to tidal and/or magnetic star-planet interactions (SPI) in the 272 known FGK planetary hosts observed by GALEX. With the increased sensitivity of GALEX, we are able probe systems with lower activity levels and at larger distances than what has been done to date with X-ray satellites. We compared samples of stars with close-in planets (a < 0.1 AU) to those with far-out planets (a > 0.5 AU) and looked for correlations of excess activity with other system parameters. This statistical investigation found no clear correlations with a, Mp , or Mp /a, in contrast to some X-ray and Ca II studies. However, there is tentative evidence (at a level of 1.8σ) that stars with radial-velocity-(RV)-detected close-in planets are more FUV-active than stars with far-out planets, in agreement with several published X-ray and Ca II results. The case is strengthened to a level of significance to 2.3σ when transit-detected close-in planets are included. This is most likely because the RV-selected sample of stars is significantly less active than the field population of comparable stars, while the transit-selected sample is similarly active. Given the factor of 2-3 scatter in fractional FUV luminosity for a given stellar effective temperature, it is necessary to conduct a time-resolved study of the planet hosts in order to better characterize their UV variability and generate a firmer statistical result. Based on observations made with the NASA Galaxy Evolution Explorer. GALEX is operated for NASA by the California Institute of Technology under NASA contract NAS5-98034.

VizieR Online Data Catalog: GALEX/S4G surface brightness profiles. I. (Bouquin+, 2018)

NASA Astrophysics Data System (ADS)

Bouquin, A. Y. K.; Gil de, Paz A.; Munoz-Mateos, J. C.; Boissier, S.; Sheth, K.; Zaritsky, D.; Peletier, R. F.; Knapen, J. H.; Gallego, J.

2018-03-01

The Spitzer Survey of Stellar Structure in Galaxies (S4GALEX FUV and NUV images and related data products for 1931 S4G galaxies that had been observed in at least one of these two UV bands. We collected imaging data from all kinds of surveys, such as the All-sky Imaging Survey, Medium Imaging Survey, Deep Imaging Survey, and Nearby Galaxy Survey, as well as from Guest Investigator (GIs/GIIs) Programs. (5 data files).

A Search for Low Surface Brightness Galaxies in the Ultraviolet with GALEX

NASA Astrophysics Data System (ADS)

Wyder, Ted K.; GALEX Science Team

2006-12-01

Low surface brightness (LSB) galaxies have traditionally been difficult to detect at visible wavelengths due to their low contrast with the night sky and their low numbers per deg2. We describe a new search for LSB galaxies using UV images from the Galaxy Evolution Explorer (GALEX) satellite. The images are from the GALEX Medium Imaging Survey targeting mainly areas of the sky within the Sloan Digital Sky Survey (SDSS) footprint. Due to the UV sky background at high Galactic latitudes reaching levels of only approximately 28 mag arcsec-2 as well as the relatively large sky coverage from GALEX, we can potentially search for LSB galaxies that would be difficult to detect optically.After first convolving the images with a suitable kernel, we select a diameter limited set of objects which we then inspect manually in order to remove image artifacts and other spurious detections. Red galaxies that have high optical surface brightness can be identified using either the ratio of far-UV to near-UV flux or via comparison to SDSS images. We quantify our selection limits using a set of artificial galaxy tests. Our goal is to find blue, ultra-LSB galaxies that would be virtually undetectable in large optical imaging surveys. GALEX is a NASA Small Explorer, launched in April 2003. We gratefully acknowledge NASA's support for construction, operation, and science analysis for the GALEX mission.

Are We Correctly Measuring Star-Formation Rates?

NASA Astrophysics Data System (ADS)

McQuinn, Kristen B.; Skillman, Evan D.; Dolphin, Andrew E.; Mitchell, Noah P.

2017-01-01

Integrating our knowledge of star formation (SF) traced by observations at different wavelengths is essential for correctly interpreting and comparing SF activity in a variety of systems and environments. This study compares extinction-corrected, integrated ultraviolet (UV) emission from resolved galaxies with color-magnitude diagram (CMD) based star-formation rates (SFRs) derived from resolved stellar populations and CMD fitting techniques in 19 nearby starburst and post-starburst dwarf galaxies. The data sets are from the panchromatic Starburst Irregular Dwarf Survey (STARBIRDS) and include deep legacy GALEX UV imaging, Hubble Space Telescope optical imaging, and Spitzer MIPS imaging. For the majority of the sample, the integrated near-UV fluxes predicted from the CMD-based SFRs—using four different models—agree with the measured, extinction corrected, integrated near-UV fluxes from GALEX images, but the far-UV (FUV) predicted fluxes do not. Furthermore, we find a systematic deviation between the SFRs based on integrated FUV luminosities and existing scaling relations, and the SFRs based on the resolved stellar populations. This offset is not driven by different SF timescales, variations in SFRs, UV attenuation, nor stochastic effects. This first comparison between CMD-based SFRs and an integrated FUV emission SFR indicator suggests that the most likely cause of the discrepancy is the theoretical FUV-SFR calibration from stellar evolutionary libraries and/or stellar atmospheric models. We present an empirical calibration of the FUV-based SFR relation for dwarf galaxies, with uncertainties, which is ˜53% larger than previous relations. These results have signficant implications for measuring FUV-based SFRs of high-redshift galaxies.

Preservation of far-UV aluminum reflectance by means of overcoating with C60 films.

PubMed

Méndez, J A; Larruquert, J I; Aznárez, J A

2000-01-01

Thin films of C(60) were investigated as protective coatings of Al films to preserve their far-UV (FUV) reflectance by inhibition or retardation of their oxidation. Two methods were used for the overcoating of Al films with approximately one monolayer of C(60): (1) deposition of a multilayer film followed by temperature desorption of all but one monolayer and (2) direct deposition of approximately one-monolayer film. We exposed both types of sample to controlled doses of molecular oxygen and water vapor and measured their FUV reflectance before and after exposure to evaluate the achieved protection on the Al films. The whole process of sample preparation, reflectance measurement, sample heating, and oxidation was made without breaking vacuum. Results show that a C(60) monolayer protected Al from oxidation to some extent, although FUV reflectance of unprotected Al films was never exceeded. FUV optical constants of C(60) films and the FUV reflectance of the C(60) film as deposited and as a function of exposure to O(2) were also measured.

The Timescale-dependent Color Variability of Quasars Viewed with /GALEX

NASA Astrophysics Data System (ADS)

Zhu, Fei-Fan; Wang, Jun-Xian; Cai, Zhen-Yi; Sun, Yu-Han

2016-11-01

In a recent work by Sun et al., the color variation of quasars, namely the bluer-when-brighter trend, was found to be timescale dependent using the SDSS g/r band light curves in Stripe 82. Such timescale dependence, I.e., bluer variation at shorter timescales, supports the thermal fluctuation origin of the UV/optical variation in quasars, and can be modeled well with the inhomogeneous accretion disk model. In this paper, we extend the study to much shorter wavelengths in the rest frame (down to extreme UV) using GALaxy Evolution eXplorer (GALEX) photometric data of quasars collected in two ultraviolet bands (near-UV and far-UV). We develop Monte Carlo simulations to correct for possible biases due to the considerably larger photometric uncertainties in the GALEX light curves (particularly in the far-UV, compared with the SDSS g/r bands), which otherwise could produce artificial results. We securely confirm the previously discovered timescale dependence of the color variability with independent data sets and at shorter wavelengths. We further find that the slope of the correlation between the amplitude of the color variation and timescale appears even steeper than predicted by the inhomogeneous disk model, which assumes that disk fluctuations follow a damped random walk (DRW) process. The much flatter structure function observed in the far-UV compared with that at longer wavelengths implies deviation from the DRW process in the inner disk, where rest-frame extreme UV radiation is produced.

UV SEDs of early-type cluster galaxies: a new look at the UV upturn

NASA Astrophysics Data System (ADS)

Ali, S. S.; Bremer, M. N.; Phillipps, S.; De Propris, R.

2018-05-01

Using GALEX, Ultraviolet Optical Telescope (UVOT), and optical photometry, we explore the prevalence and strength of the Ultraviolet (UV) upturn in the spectra of quiescent early-type galaxies in several nearby clusters. Even for galaxies with completely passive optical colours, there is a large spread in vacuum UV colour consistent with almost all having some UV upturn component. Combining GALEX and UVOT data below 3000 Å, we generate for the first time comparatively detailed UV spectral energy distributions for Coma cluster galaxies. Fitting the UV upturn component with a blackbody, 26 of these show a range of characteristic temperatures (10 000-21 000K) for the UV upturn population. Assuming a single temperature to explain GALEX-optical colours could underestimate the fraction of galaxies with UV upturns and mis-classify some as systems with residual star formation. The UV upturn phenomenon is not an exclusive feature found only in giant galaxies; we identify galaxies with similar (or even bluer) FUV - V colours to the giants with upturns over a range of fainter luminosities. The temperature and strength of the UV upturn are correlated with galaxy mass. Under the plausible hypothesis that the sources of the UV upturn are blue horizontal branch stars, the most likely mechanism for this is the presence of a substantial (between 4 per cent and 20 per cent) Helium-rich (Y > 0.3) population of stars in these galaxies, potentially formed at z ˜ 4 and certainly at z > 2; this plausibly sets a lower limit of {˜ } {0.3- 0.8} × 10^{10} M⊙ to the in situ stellar mass of ˜L* galaxies at this redshift.

GALEX Grism Spectroscopy of the Globular Cluster Omega Centauri

NASA Astrophysics Data System (ADS)

Sweigart, Allen

We propose to obtain GALEX FUV-only grism spectroscopy of the hot stars in omega Centauri, the most massive globular cluster in our Galaxy. Previous UIT imagery of omega Cen showed that it contains about 2000 hot horizontal branch (HB) stars, and we estimate that GALEX spectra can be obtained for about 500 of these stars in the outer regions of the cluster, including about 50 of the hot ``blue hook'' stars discovered with UIT. The blue hook stars appear to be both hotter (35,000 K) and less luminous in the UIT color-magnitude diagram than predicted by canonical HB models and, indeed, are unexplained by standard evolutionary theory. Brown et al. (2001) have suggested that the blue hook stars are the progeny of stars which mixed their surface hydrogen into their hot He-burning interior during a delayed helium flash subsequent to leaving the red giant branch. This ``flash-mixing'' results in a hot hydrogen-deficient star with a typical surface abundance of 96% He and 4% C by mass. The GALEX spectral region includes the strong lines of C III 1426, 1578 A, C IV 1550 A, and He II 1640 A which will allow this predicted carbon and helium enrichment to be detected. These observations will therefore provide a crucial test of the Brown et al. flash-mixing hypothesis and will determine if flash mixing represents a new evolutionary channel for populating the hot HB. The GALEX spectra will also address other questions concerning the hot HB in omega Cen including (1) the metallicity distribution of HB stars with 9,000 K < Teff < 11,000 K, (2) the effect of radiative levitation on the UV spectra of stars with Teff > 11,000 K, and (3) the origin of the subluminous HB stars found in the UIT photometry with 15,000K < Teff < 30,000 K.

Deep X-ray and UV Surveys of Galaxies with Chandra, XMM-Newton, and GALEX

NASA Technical Reports Server (NTRS)

Hornschemeier, Ann

2006-01-01

Only with the deepest Chandra surveys has X-ray emission from normal and star forming galaxies (as opposed to AGN, which dominate the X-ray sky) been accessible at cosmologically interesting distances. The X-ray emission from accreting binaries provide a critical glimpse into the binary phase of stellar evolution and studies of the hot gas reservoir constrain past star formation. UV studies provide important, sensitive diagnostics of the young star forming populations and provide the most mature means for studying galaxies at 2 < zeta < 4. This talk will review current progress on studying X-ray emission in concert with UV emission from normal/star-forming galaxies at higher redshift. We will also report on our new, deep surveys with GALEX and XMM-Newton in the nearby Coma cluster. These studies are relevant to DEEP06 as Coma is the nearest rich cluster of galaxies and provides an important benchmark for high-redshift studies in the X-ray and UV wavebands. The 30 ks GALEX (note: similar depth to the GALEX Deep Imaging Survey) and the 110 ks XMM observations provide extremely deep coverage of a Coma outskirts field, allowing the construction of the UV and X-ray luminosity function of galaxies and important constraints on star formation scaling relations such as the X-ray-Star Formation Rate correlation and the X-ray/Stellar Mass correlation. We will discuss what we learn from these deep observations of Coma, including the recently established suppression of the X-ray emission from galaxies in the Coma outskirts that is likely associated with lower levels of past star formation and/or the results of tidal gas stripping.

THE DETECTION RATE OF EARLY UV EMISSION FROM SUPERNOVAE: A DEDICATED GALEX/PTF SURVEY AND CALIBRATED THEORETICAL ESTIMATES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ganot, Noam; Gal-Yam, Avishay; Ofek, Eran O.

The radius and surface composition of an exploding massive star, as well as the explosion energy per unit mass, can be measured using early UV observations of core-collapse supernovae (SNe). We present the first results from a simultaneous GALEX/PTF search for early ultraviolet (UV) emission from SNe. Six SNe II and one Type II superluminous SN (SLSN-II) are clearly detected in the GALEX near-UV (NUV) data. We compare our detection rate with theoretical estimates based on early, shock-cooling UV light curves calculated from models that fit existing Swift and GALEX observations well, combined with volumetric SN rates. We find thatmore » our observations are in good agreement with calculated rates assuming that red supergiants (RSGs) explode with fiducial radii of 500 R{sub ⊙}, explosion energies of 10{sup 51} erg, and ejecta masses of 10 M{sub ⊙}. Exploding blue supergiants and Wolf–Rayet stars are poorly constrained. We describe how such observations can be used to derive the progenitor radius, surface composition, and explosion energy per unit mass of such SN events, and we demonstrate why UV observations are critical for such measurements. We use the fiducial RSG parameters to estimate the detection rate of SNe during the shock-cooling phase (<1 day after explosion) for several ground-based surveys (PTF, ZTF, and LSST). We show that the proposed wide-field UV explorer ULTRASAT mission is expected to find >85 SNe per year (∼0.5 SN per deg{sup 2}), independent of host galaxy extinction, down to an NUV detection limit of 21.5 mag AB. Our pilot GALEX/PTF project thus convincingly demonstrates that a dedicated, systematic SN survey at the NUV band is a compelling method to study how massive stars end their life.« less

The Detection Rate of Early UV Emission from Supernovae: A Dedicated Galex/PTF Survey and Calibrated Theoretical Estimates

NASA Astrophysics Data System (ADS)

Ganot, Noam; Gal-Yam, Avishay; Ofek, Eran. O.; Sagiv, Ilan; Waxman, Eli; Lapid, Ofer; Kulkarni, Shrinivas R.; Ben-Ami, Sagi; Kasliwal, Mansi M.; The ULTRASAT Science Team; Chelouche, Doron; Rafter, Stephen; Behar, Ehud; Laor, Ari; Poznanski, Dovi; Nakar, Ehud; Maoz, Dan; Trakhtenbrot, Benny; WTTH Consortium, The; Neill, James D.; Barlow, Thomas A.; Martin, Christofer D.; Gezari, Suvi; the GALEX Science Team; Arcavi, Iair; Bloom, Joshua S.; Nugent, Peter E.; Sullivan, Mark; Palomar Transient Factory, The

2016-03-01

The radius and surface composition of an exploding massive star, as well as the explosion energy per unit mass, can be measured using early UV observations of core-collapse supernovae (SNe). We present the first results from a simultaneous GALEX/PTF search for early ultraviolet (UV) emission from SNe. Six SNe II and one Type II superluminous SN (SLSN-II) are clearly detected in the GALEX near-UV (NUV) data. We compare our detection rate with theoretical estimates based on early, shock-cooling UV light curves calculated from models that fit existing Swift and GALEX observations well, combined with volumetric SN rates. We find that our observations are in good agreement with calculated rates assuming that red supergiants (RSGs) explode with fiducial radii of 500 R ⊙, explosion energies of 1051 erg, and ejecta masses of 10 M ⊙. Exploding blue supergiants and Wolf-Rayet stars are poorly constrained. We describe how such observations can be used to derive the progenitor radius, surface composition, and explosion energy per unit mass of such SN events, and we demonstrate why UV observations are critical for such measurements. We use the fiducial RSG parameters to estimate the detection rate of SNe during the shock-cooling phase (<1 day after explosion) for several ground-based surveys (PTF, ZTF, and LSST). We show that the proposed wide-field UV explorer ULTRASAT mission is expected to find >85 SNe per year (˜0.5 SN per deg2), independent of host galaxy extinction, down to an NUV detection limit of 21.5 mag AB. Our pilot GALEX/PTF project thus convincingly demonstrates that a dedicated, systematic SN survey at the NUV band is a compelling method to study how massive stars end their life.

Evolved Late-Type Star FUV Spectra: Mass Loss and Fluorescence

NASA Technical Reports Server (NTRS)

Harper, Graham M.

2005-01-01

This proposal was for a detailed analysis of the far ultraviolet (FUV) photoionizing radiation that provides crucial input physics for mass loss studies, e.g., observations of the flux below 10448, allow us to constrain the Ca II/Ca III balance and make significant progress beyond previous optical studies on stellar mass loss and circumstellar photochemistry. Our targets selection provided good spectral-type coverage required to help unravel the Ca II/Ca III balance as the mass-loss rates increase by over three orders of magnitude from K5 III to M5 III. We also explored the relationship between the FUV radiation field and other UV diagnostics to allow us to empirically estimate the FUV radiation field for the vast majority of stars which are too faint to be observed with FUSE, and to improve upon their uncertain mass-loss rates.

UV/Optical Detections of Candidate Tidal Disruption Events by GALEX and CFHTLS

NASA Astrophysics Data System (ADS)

Gezari, S.; Basa, S.; Martin, D. C.; Bazin, G.; Forster, K.; Milliard, B.; Halpern, J. P.; Friedman, P. G.; Morrissey, P.; Neff, S. G.; Schiminovich, D.; Seibert, M.; Small, T.; Wyder, T. K.

2008-04-01

We present two luminous UV/optical flares from the nuclei of apparently inactive early-type galaxies at z = 0.37 and 0.33 that have the radiative properties of a flare from the tidal disruption of a star. In this paper we report the second candidate tidal disruption event discovery in the UV by the GALEX Deep Imaging Survey and present simultaneous optical light curves from the CFHTLS Deep Imaging Survey for both UV flares. The first few months of the UV/optical light curves are well fitted with the canonical t-5/3 power-law decay predicted for emission from the fallback of debris from a tidally disrupted star. Chandra ACIS X-ray observations during the flares detect soft X-ray sources with Tbb = (2-5) × 105 K or Γ > 3 and place limits on hard X-ray emission from an underlying AGN down to LX(2-10 keV) lesssim 1041 ergs s-1. Blackbody fits to the UV/optical spectral energy distributions of the flares indicate peak flare luminosities of gtrsim1044-1045 ergs s-1. The temperature, luminosity, and light curves of both flares are in excellent agreement with emission from a tidally disrupted main-sequence star onto a central black hole of several times 107 M⊙. The observed detection rate of our search over ~2.9 deg2 of GALEX Deep Imaging Survey data spanning from 2003 to 2007 is consistent with tidal disruption rates calculated from dynamical models, and we use these models to make predictions for the detection rates of the next generation of optical synoptic surveys. Some of the data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation.

Stellar Activity in the Broadband Ultraviolet

NASA Astrophysics Data System (ADS)

Findeisen, K.; Hillenbrand, L.; Soderblom, D.

2011-07-01

The completion of the GALEX All-Sky Survey in the ultraviolet allows activity measurements to be acquired for many more stars than is possible with the limited sensitivity of ROSAT or the limited sky coverage of Chandra, XMM, or spectroscopic surveys for line emission in the optical or ultraviolet. We have explored the use of GALEX photometry as an activity indicator, using stars within 50 pc as a calibration sample representing the field and in selected nearby associations representing the youngest stages of stellar evolution. We present preliminary relations between UV flux and the optical activity indicator R'HK and between UV flux and age. We demonstrate that far-UV (FUV, 1350-1780 Å) excess flux is roughly proportional to R'HK. We also detect a correlation between near-UV (NUV, 1780-2830 Å) flux and activity or age, but the effect is much more subtle, particularly for stars older than ~0.5-1 Gyr. Both the FUV and NUV relations show large scatter, ~0.2 mag when predicting UV flux, ~0.18 dex when predicting R'HK, and ~0.4 dex when predicting age. This scatter appears to be evenly split between observational errors in current state-of-the-art data and long-term activity variability in the sample stars.

Characterizing Extragalactic Star Formation with GALEX Legacy Photometric Analysis of UV-Bright Stellar Complexes

NASA Astrophysics Data System (ADS)

Thilker, David

At the close of nearly a decade of observing, GALEX has accumulated an unprecedented archive of ultraviolet (UV) images revealing both the scope and intricacy of star formation (SF) in many thousands of galaxies inhabiting the local universe. If the observed hierarchical SF morphology can be quantified systematically, and physically interpreted with multi-wavelength ancillary data and modeling, then the low redshift GALEX legacy will approach completion. However, the GALEX GR6 pipeline database contains a highly incomplete census of young stellar complexes even for very well-studied galaxies. We propose to apply a dedicated photometry algorithm that has been optimized for measuring the properties of irregularly shaped sources in crowded galaxy images containing spatially variant, diffuse intra-clump emission. Structures will be selected in the UV, but we will compile UV-visible-MIR SEDs for each detection utilizing Pan-STARRS1+SDSS and WISE data. These SEDs will then be fit using population-synthesis models to derive estimated stellar mass, age, and extinction. Processing will be completed for the entire diameter-limited GALEX Large Galaxy Atlas (GLGA) sample of 20,000+ galaxies, at a variety of standardized spatial resolutions. Although the precise categorization of the cataloged substructures will depend on galaxy distance, the outcome of our analysis will be a catalog similar to the stellar association surveys of past decades for very nearby galaxies based on resolved stars (e.g. van den Bergh 1964, Hodge 1986, Efremov et al. 1987), except that our investigation will probe a galaxy sample of dramatically larger size using the integrated UV light from such groupings of young stars. Our algorithm is multi-scale in nature and will thus preserve the hierarchical properties of the stellar distribution, by linking sub-clumps to their larger-scale parent feature(s). The resulting database will be a fundamental resource for follow-up multi-wavelength studies probing SF

VizieR Online Data Catalog: Palomar/MSU and SDSS-DR7 M dwarfs with GALEX obs. (Jones+, 2016)

NASA Astrophysics Data System (ADS)

Jones, D. O.; West, A. A.

2016-03-01

To compare magnetic activity in the optical with UV activity, we matched the SDSS Data Release 7 (DR7; Abazajian et al. 2009, II/294) M dwarf spectroscopic catalog (West et al. 2011, J/AJ/141/97; R~2000) to GALEX data from Data Releases 6 and 7 (NUV: ~1750-2750Å and FUV: ~1350-1750Å; see II/312). The DR7 M dwarf catalog consists of 70841 SDSS M dwarfs with spectral types verified by eye. We supplemented the SDSS sample with the Palomar/MSU Nearby-Star Spectroscopic Survey (PMSU; Reid et al. 1995, III/198), which contains 1684 nearby low-mass stars (1415 M dwarfs) as part of the northern sample (δ>-30°) and 282 nearby low-mass stars (228 M dwarfs) as part of the southern sample. (2 data files).

Old but Still Warm: Far-UV Detection of PSR B0950+08

NASA Astrophysics Data System (ADS)

Pavlov, G. G.; Rangelov, B.; Kargaltsev, O.; Reisenegger, A.; Guillot, S.; Reyes, C.

2017-11-01

We report on a Hubble Space Telescope detection of the nearby, old pulsar B0950+08 (d≃ 262 pc, spin-down age 17.5 Myr) in two far-ultraviolet (FUV) bands. We measured the mean flux densities {\\bar{f}}ν =109+/- 6 nJy and 83 ± 14 nJy in the F125LP and F140LP filters (pivot wavelengths 1438 and 1528 Å). Using the FUV data together with previously obtained optical-UV data, we conclude that the optical-FUV spectrum consists of two components—a nonthermal (presumably magnetospheric) power-law spectrum ({f}ν \\propto {ν }α ) with slope α ˜ -1.2 and a thermal spectrum emitted from the bulk of the neutron star (NS) surface with a temperature in the range of (1-3) × 105 K, depending on interstellar extinction and NS radius. These temperatures are much higher than predicted by NS cooling models for such an old pulsar, which means that some heating mechanisms operate in NSs. A plausible mechanism responsible for the high temperature of PSR B0950+08 is the interaction of vortex lines of the faster rotating neutron superfluid with the slower rotating normal matter in the inner NS crust (vortex creep heating). Based on observations made with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. These observations are associated with program #13783.

Portal to the GALEX Data Archive

NASA Astrophysics Data System (ADS)

Smith, M. A.; Conti, A.; Shiao, B.; Volpicelli, C. A.

2004-05-01

In early February MAST began its hosting of the GALEX public "Early Release Observations" images (40,000 objects) and spectra (1000 objects). MAST will host a much larger "first release," the GALEX DR1, in October, 2004. In this poster we describe features of our on-line website at http://galex.stsci.edu for researchers interested in downloading and browsing GALEX UV image and spectral data. The site, is based on MS .NET technology and user queries are entered for classes of objects or sky regions on a "MAST-like" query forms or with detailed queries written in SQL. In the latter case examples are provided to tailor a query to a user's specifications. The site provides novel features, such as tooltips that return keyword definitions, "active images" that return object classification and coordinate information in a 2.5 arcmin radius around the selected object, self-documentation of terms and tables, and of course a tutorial for new navigators. The GALEX database employs a Hierarchial Triangular Mesh system for rapid data discovery, neighbor searches, and cross correlations with other catalogs. Our "GMAX" tool allows a coplotting of object positions for objects observed by GALEX and other US-NVO compliant mission websites such as Sloan, 2MASS, FIRST.... As a member of the new Skynode network, GALEX has reported its web services to the US-NVO registry. This permits users to generate queries from other sites to cross-correlate, compare, and plot GALEX data using US-NVO protocols. Future plans for limited on-line data analysis and footprint services are described.

SOUTHERN COSMOLOGY SURVEY. III. QSOs FROM COMBINED GALEX AND OPTICAL PHOTOMETRY

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jimenez, Raul; Verde, Licia; Spergel, David N.

2009-04-15

We present catalogs of QSO candidates selected using photometry from Galaxy Evolution Explorer (GALEX) combined with the Sloan Digital Sky Survey (SDSS) in the Stripe 82 region and Blanco Cosmology Survey (BCS) near declination -55 deg. The SDSS region contains {approx_equal}700 objects with magnitude i < 20 and {approx_equal}3600 objects with i < 21.5 in a {approx_equal}60 deg{sup 2} sky region, while the BCS region contains {approx_equal}280 objects with magnitude i < 20 and {approx}2000 objects with i < 21.5 for a 11 deg{sup 2} sky region that is being observed by three current microwave Sunyaev-Zeldovich surveys. Our QSO catalogmore » is the first one in the BCS region. Deep GALEX exposures ({approx}>2000 s in F {sub UV} and N {sub UV}, except in three fields) provide high signal-to-noise photometry in the GALEX bands (F {sub UV}, N {sub UV} < 24.5 mag). From this data, we select QSO candidates using only GALEX and optical r-band photometry, using the method given by Atlee and Gould. In the Stripe 82 field, 60% (30%) of the GALEX-selected QSOs with optical magnitude i < 20 (i < 21.5) also appear in the Richards et al. QSO catalog constructed using five-band optical SDSS photometry. Comparison with the same catalog by Richards et al. shows that the completeness of the sample is approximately 40% (25%). However, for regions of the sky with very low dust extinction, like the BCS 23-hr field and the Stripe 82 between 0{sup 0} and 10{sup 0} in R.A., our completeness is close to 95%, demonstrating that deep GALEX observations are almost as efficient as multiwavelength observations at finding QSOs. GALEX observations thus provide a viable alternate route to QSO catalogs in sky regions where u-band optical photometry is not available. The full catalog is available at http://www.ice.csic.es/personal/jimenez/PHOTOZ.« less

A Glimpse at Quasar Host Galaxy Far-UV Emission, Using Damped Lyα's as Natural Coronagraphs

DOE PAGES

Cai, Zheng; Fan, Xiaohui; Noterdaeme, Pasquier; ...

2014-09-16

In merger-driven models of massive galaxy evolution, the luminous quasar phase is expected to be accompanied by vigorous star formation in quasar host galaxies. In this paper, we use high column density damped Lyα (DLA) systems along quasar sight lines as natural coronagraphs to directly study the far-UV (FUV) radiation from the host galaxies of luminous background quasars. Here, we have stacked the spectra of ~2000 DLA systems (N HI > 10 20.6cm –2) with a median absorption redshiftmore » $$\\langle$$z$$\\rangle$$ = 2.6 selected from quasars observed in the SDSS-III Baryon Oscillation Spectroscopic Survey. We detect residual flux in the dark troughs of the composite DLA spectra. The level of this residual flux significantly exceeds systematic errors in the Sloan Digital Sky Survey fiber sky subtraction; furthermore, the residual flux is strongly correlated with the continuum luminosity of the background quasar, while uncorrelated with DLA column density or metallicity. We conclude that the flux could be associated with the average FUV radiation from the background quasar host galaxies (with medium redshift $$\\langle$$z$$\\rangle$$ = 3.1) that is not blocked by the intervening DLA. Finally, assuming that all of the detected flux originates from quasar hosts, for the highest quasar luminosity bin ($$\\langle$$L$$\\rangle$$ = 2.5 × 10 13 L ⊙), the host galaxy has an FUV intensity of 1.5 ± 0.2 × 10 40 erg s –1 Å –1; this corresponds to an unobscured UV star formation rate of 9 M ⊙ yr –1.« less

Far-UV properties of the nuclear region of M31

NASA Technical Reports Server (NTRS)

King, Ivan R.; Stanford, S. Adam; Crane, Philippe

1995-01-01

Comparison of the Hubble Space Telescope (HST) far-UV and visible images of the nucleus of M31 deepens the mystery of the two brightness peaks recently discovered by Lauer et al. At 175 mm the brightest point is the optically fainter peak (P2) that is close to the dynamical center. The very center of P2 has a UV upturn that is much greater than that of the bulge light, while the UV upturn of the optically brighter but off-center P1 is very similar to that of its surroundings. The excess FUV radiation form P2 is closely confined to its center and has a total flux density of 3 micro-joules, a level that is less likely to come from stellar radiation than from a high-frequency extension of the radio source at the center of M31. A surrounding region of 1.8 pc radius has a somewhat smaller Uv upturn than the rest of the bulge, but there is some lingering possibility that this depression might be an artifact of our correction of the spherical aberration. Our improvement decomposition of the V image removes the need to postulate a dust lane near the center. We confirm that P1 is very compact, and we derive a luminosity for it similar to that found by Lauer et al. The implications of all of this are briefly discussed.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Smith, Myron A.; Shiao, Bernard; Bianchi, Luciana, E-mail: myronmeister@gmail.com, E-mail: shiao@stsci.edu, E-mail: bianchi@pha.jhu.edu

We report on intriguing photometric properties of Galactic stars observed in the Galaxy Evolution Explorer (GALEX) satellite's far-UV (FUV) and near-UV (NUV) bandpasses, as well as from the ground-based Sloan Digital Sky Survey (SDSS) and the Kepler Input Catalog. The first property is that the (FUV – NUV) color distribution of stars in the Kepler field consists of two well-separated peaks. A second and more perplexing property is that for stars with spectral types G or later the mean (FUV – NUV) color becomes much bluer, contrary to expectation. Investigating this tendency further, we found in two samples of mid-Fmore » through K type stars that 17%-22% of them exhibit FUV excesses relative to their NUV fluxes and spectral types. A correction for FUV incompleteness of the FUV magnitude-limited star sample brings this ratio to 14%-18%. Nearly the same fractions are also discovered among members of the Kepler Eclipsing Binary Catalog and in the published list of Kepler Objects of Interest. These UV-excess ('UVe') colors are confirmed by the negative UV continuum slopes in GALEX spectra of members of the population. The SDSS spectra of some UVe stars exhibit metallic line weakening, especially in the blue. This suggests an enhanced contribution of UV flux relative to photospheric flux of a solar-type single star. We consider the possibility that the UV excesses originate from various types of hot stars, including white dwarf DA and sdB stars, binaries, and strong chromosphere stars that are young or in active binaries. The space density of compact stars is too low to explain the observed frequency of the UVe stars. Our model atmosphere-derived simulations of colors for binaries with main-sequence pairs with a hot secondary demonstrate that the color loci conflict with the observed sequence. As a preferred alternative we are left with the active chromospheres explanation, whether in active close binaries or young single stars, despite the expected paucity of

Reionization through Trickery: How to Find the True FUV Spectra of z>6 Quasars

NASA Astrophysics Data System (ADS)

O'Dowd, Matthew; Schiminovich, D.; Webster, R. L.; Haiman, Z.

2011-01-01

Studies of absorption in the vicinity of z > 6 quasars will enable characterization of the final stages of the epoch of reionization, and measurement of the last remnants of the neutral fraction from the cosmic dark ages. Before this can happen, we will need to know the intrinsic shape of the rest-frame FUV spectrum of luminous quasars, and in particular of the Lyman-Alpha emission line. To date, such measurements have only been possible for local, low luminosity quasars and Seyferts whose FUV spectra are not strongly absorbed in the IGM. These AGN are poor models of their high-luminosity cousins, and the BELR physics driving the Ly-alpha line may be very different. I will outline two approaches to measuring the true, unabsorbed FUV spectra of luminous quasars. First, by observing differential microlensing of strongly lensed quasars at z > 3, I will show how we can algebraically reconstruct the true FUV spectrum, and recover the absorption spectrum and measure the proximity effect to boot. Second, by targeting a narrow redshift range at z 1, we can identify a subsample of luminous quasars that have avoided significant absorption, but are nonetheless genuine analogs of our z > 6 quasars. I will show some preliminary GALEX data of these quasars.

A glimpse at quasar host galaxy far-UV emission using damped Lyα's as natural coronagraphs

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cai, Zheng; Fan, Xiaohui; Wang, Ran

2014-10-01

In merger-driven models of massive galaxy evolution, the luminous quasar phase is expected to be accompanied by vigorous star formation in quasar host galaxies. In this paper, we use high column density damped Lyα (DLA) systems along quasar sight lines as natural coronagraphs to directly study the far-UV (FUV) radiation from the host galaxies of luminous background quasars. We have stacked the spectra of ∼2000 DLA systems (N {sub H} {sub I} > 10{sup 20.6} cm{sup –2}) with a median absorption redshift (z) = 2.6 selected from quasars observed in the SDSS-III Baryon Oscillation Spectroscopic Survey. We detect residual fluxmore » in the dark troughs of the composite DLA spectra. The level of this residual flux significantly exceeds systematic errors in the Sloan Digital Sky Survey fiber sky subtraction; furthermore, the residual flux is strongly correlated with the continuum luminosity of the background quasar, while uncorrelated with DLA column density or metallicity. We conclude that the flux could be associated with the average FUV radiation from the background quasar host galaxies (with medium redshift (z) = 3.1) that is not blocked by the intervening DLA. Assuming that all of the detected flux originates from quasar hosts, for the highest quasar luminosity bin ((L) = 2.5 × 10{sup 13} L {sub ☉}), the host galaxy has an FUV intensity of 1.5 ± 0.2 × 10{sup 40} erg s{sup –1} Å{sup –1}; this corresponds to an unobscured UV star formation rate of 9 M {sub ☉} yr{sup –1}.« less

Optimization of MgF2-deposition temperature for far UV Al mirrors.

PubMed

De Marcos, Luis V Rodríguez; Larruquert, Juan I; Méndez, José A; Gutiérrez-Luna, Nuria; Espinosa-Yáñez, Lucía; Honrado-Benítez, Carlos; Chavero-Royán, José; Perea-Abarca, Belén

2018-04-02

Progress towards far UV (FUV) coatings with enhanced reflectance is invaluable for future space missions, such as LUVOIR. This research starts with the procedure developed to enhance MgF 2 -protected Al reflectance through depositing MgF 2 on a heated aluminized substrate [Quijada et al., Proc. SPIE 8450, 84502H (2012)] and it establishes the optimum deposition temperature of the MgF 2 protective film for Al mirrors with a reflectance as high as ~90% at 121.6 nm. Al films were deposited at room temperature and protected with a MgF 2 film deposited at various temperatures ranging from room temperature to 350°C. It has been found that mirror reflectance in the short FUV range continuously increases with MgF 2 deposition temperature up to 250°C, whereas reflectance decreases at temperatures of 300°C and up. The short-FUV reflectance of mirrors deposited at 250°C only slightly decreased over time by less than 1%, compared to a larger decay for standard coatings prepared at room temperature. Al mirrors protected with MgF 2 deposited at room temperature that were later annealed displayed a similar reflectance enhancement that mirrors protected at high temperatures. MgF 2 and Al roughness as well as MgF 2 density were analyzed by x-ray grazing incidence reflectometry. A noticeable reduction in both Al and MgF 2 roughness, as well as an increase of MgF 2 density, were measured for films deposited at high temperatures. On the other hand, it was found a strong correlation between the protective-layer deposition temperature (or post-deposition annealing temperature) and the pinhole open area in Al films, which could be prevented with a somewhat thicker Al film.

Thermal control design of the Galaxy Evolution Explorer (GALEX)

NASA Technical Reports Server (NTRS)

Tsuyuki, G. T.; Lee, S. C.

2001-01-01

This paper describes the thermal control design of GALEX, an ultraviolet telescope that investigates the UV properties of local galaxies, history of star formation, and global causes of star formation and evolution.

GALEX Wide-field Ultraviolet Imaging of NGC 5128 (Centaurus-A)

NASA Technical Reports Server (NTRS)

Neff, S. G.; Shiminovich, D.; Martin, C. D.

2004-01-01

We present new wide-field ultraviolet (UV) observations of the nearby active galaxy NGC 5128 (Centaurus A). The GALEX images provide 3.5 sec - 5.5 sec resolution over a 1.2 degree field, in two broad bands (1350- 1800A and 1800-3000A, centered at 1550A and 2200A). We detect ultraviolet emission associated with the radio and X-ray jets in both bands, extending out to a distance of approx. 40kpc from the galaxy nucleus. We compare the radio, X-ray, and UV jets, and discuss the feasibility of jet-induced star formation. We show how the UV emission relates to the optical filaments: HI and CO clouds, stellar shells, X-ray arcs, and young star chains previously reported by other authors. In the central region of NGC 5128, we detect UV emission from young super-star-clusters and associated ionized gas located along the near edge and on the upper surface of the dusty warped disk. All of the UV emission in the galaxy appears to result from intense star formation in the disk; none appears to be associated with the old stellar population of the main galaxy body, and no UV emission from the AGN is detected. We estimate the numbers and ages of the massive young stars present, and the associated ionized gas masses. Finally, we compare Cen-A to high redshift radio galaxies which were much more numerous in the earlier universe. The GALEX satellite is a NASA Small Explorer, launched in April 2003. We gratefully acknowledge NASA's support for construction, operation, and science analysis for the GALEX mission.

VizieR Online Data Catalog: LITTLE THINGS dwarf irregular galaxies FUV regions (Hunter+, 2016)

NASA Astrophysics Data System (ADS)

Hunter, D. A.; Elmegreen, B. G.; Gehret, E.

2018-03-01

The sample of galaxies is taken from LITTLE THINGS (Local Irregulars That Trace Luminosity Extremes, The H I Nearby Galaxy Survey, Hunter et al. 2012, J/AJ/144/134). This is a multi-wavelength survey of nearby (<10.3 Mpc) dIrr galaxies and BCDs, which builds on the THINGS project, whose emphasis was on nearby spirals (Walter et al. 2008, J/AJ/136/2563). The galaxies and a few key parameters are listed in Table 1. We used FUV (1516 Å) images obtained by GALEX (Melena et al. 2009, J/AJ/138/1203; Hunter et al. 2010AJ....139..447H, 2011AJ....142..121H; Zhang et al. 2012AJ....143...47Z) to identify knots of emission in the outer disks of each galaxy. In order to better distinguish knots from the wide-spread diffuse emission, we subtracted the stellar continuum from each FUV image using the V-band image. (2 data files).

From the Milky Way to differing galaxy environments: filling critical gaps in our knowledge of star formation and its interplay with dust, and in stellar and galaxy evolution.

NASA Astrophysics Data System (ADS)

Bianchi, Luciana

2018-01-01

Rest-frame UV, uniquely sensitive to luminous, short-lived hot massive stars, trace and age-date star formation across galaxies, and is very sensitive to dust, whose properties and presence are closely connected to star formation.With wide f-o-v and deep sensitivity in two broad filters,FUV and NUV,GALEX delivered the first comprehensive UV view of large nearby galaxies, and of the universe to z~2 (e.g.,Bianchi 2014 ApSS 354,103), detected star formation at the lowest rates, in environments where it was not seen before and not expected (e.g. Bianchi 2011 ApSS 335,51; Thilker+2009 Nature 457,990;2007 ApJS 173,538), triggering a new era of investigations with HST and large ground-based telescopes. New instrument technology and modeling capabilities make it now possible and compelling to solve standing issues. The scant UV filters available (esp. FUV) and the wide gap in resolution and f-o-v between GALEX and HST leaves old and new questions open. A chief limitation is degeneracies between physical parameters of stellar populations (age/SFR) and hot stars, and dust (e.g. Bianchi+ 2014 JASR 53,928).We show sample model simulations for filter optimization to provide critical measurements for the science objectives. We also demonstrate how adequate FUV+NUV filters, and resolution, allow us to move from speculative interpretation of UV data to unbiased physical characterization of young stellar populations and dust, using new data from UVIT, which, though smaller than CETUS, has better resolution and filter coverage than GALEX.Also, our understanding of galaxy chemical enrichment is limited by critical gaps in stellar evolution; GALEX surveys enabled the first unbiased census of the Milky Way hot-WD population (Bianchi+2011 MNRAS, 411,2770), which we complement with SDSS, Pan-STARRS, and Gaia data to fill such gaps (Bianchi et al.2018, ApSS). Such objects in CETUS fields (deeper exposures, more filters, and the first UV MOS) will be much better characterized, enabling

White Dwarfs in the GALEX Survey

NASA Technical Reports Server (NTRS)

Kawka, Adela; Vennes, Stephane

2007-01-01

We have cross-correlated the 2dF QSO Redshift Survey (2QZ) white dwarf catalog with the GALEX 2nd Data Release and the Sloan Digital Sky Survey (SDSS) data release 5 to obtain ultraviolet photometry (FUV, NUV) for approximately 700 objects and optical photometry (ugriz) for approximately 800 objects. We have compared the optical-ultraviolet colors to synthetic white dwarf colors to obtain temperature estimates for approximately 250 of these objects. These white dwarfs have effective temperatures ranging from 10 000 K (cooling age of about 1Gyr) up to about 40000 K (cooling age of about 3 Myrs), with a few that have even higher temperatures. We found that to distinguish white dwarfs from other stellar luminosity classes both optical and ultraviolet colors are necessary, in particular for the hotter objects where there is contamination from B and 0 main-sequence stars. Using this sample we build a luminosity function for the DA white dwarfs with Mv < 12 mag.

Thermal design and test verification of GALAXY evolution explorer (GALEX)

NASA Technical Reports Server (NTRS)

Wu, P. S.; Lee, S. -C.

2002-01-01

This paper describes the thermal control design of GALEX, an ultraviolet telescope that investigates the UV properties of local galaxies, history of star formation, and global causes of star formation and evolution.

Far-ultraviolet observation of the globular cluster NGC 6397

NASA Astrophysics Data System (ADS)

Dieball, A.; Rasekh, A.; Knigge, C.; Shara, M.; Zurek, D.

2017-07-01

We present an observational far-ultraviolet (FUV) and near-ultraviolet (NUV) study of the core region of the globular cluster (GC) NGC 6397. The observations were obtained with the Space Telescope Imaging Spectrograph (STIS, FUV) and the Wide Field Camera 3 (NUV) on board the Hubble Space Telescope. Here, we focus on the UV-bright stellar populations such as blue stragglers (BSs), white dwarfs (WDs) and cataclysmic variables (CVs). We present the first FUV - NUV colour-magnitude diagram (CMD) for this cluster. To support our classification of the stellar populations, we compare our FUV - NUV CMD with optical data from the ACS Survey of Galactic Globular Clusters. The FUV - NUV CMD indicates 16 sources located in the WD area, and 10 BSs within the 25 × 25 arcsec2 of the STIS FUV data. 18 Chandra X-ray sources are located within the FUV field of view. 13 of those have an NUV counterpart, of which 9 sources also have an FUV counterpart. Out of those, five sources are previously suggested CVs, and indeed, all five are located in the WD/CV region in our FUV - NUV CMD. Another CV has only an FUV but no NUV counterpart. We also detect an NUV (but no FUV) counterpart to the millisecond pulsar (MSP) located in the core of this cluster. The NUV light curves of the CVs and MSP show flickering behaviour typical of CVs. We found that the BSs and CVs are the most centrally concentrated populations. This might be an effect of mass segregation or it might indicate the preferred birth place of BSs and CVs via dynamical interactions in the dense core region of GCs. Horizontal branch stars are the least centrally concentrated population and absent in the innermost area of the core.

The Far Ultraviolet (FUV) auroral imager for the Inner Magnetospheric Imager (IMI) mission: Options

NASA Technical Reports Server (NTRS)

Wilson, Gordon R.

1993-01-01

The change from an intermediate mission (cost ceiling of $300 million) to a solar-terrestrial probe class mission (cost ceiling of $150 million) will require some major changes in the configuration of the IMI mission. One option being considered is to move to a small spin-stabilized spacecraft (with no despun platform) which could be launched with a smaller Taurus or Conestoga class booster. Such a change in spacecraft type would not present any fundamental problems (other than restrictions on mass and power) for the He plus 304 A plasmasphere imager, the high and low energy neutral atom imagers, and the geocoronal imager, but would present a challenge for the FUV auroral imager since the original plan called for this instrument to operate from a despun platform. Since the FUV instrument is part of the core payload it cannot be dropped from the instrument complement without jeopardizing the science goals of the mission. A way must be found to keep this instrument and to allow it to accomplish most, if not all, of its science objectives. One of the subjects discussed are options for building an FUV instrument for a spinning spacecraft. Since a number of spinning spacecraft have carried auroral imagers, a range of techniques exists. In addition, the option of flying the FUV imager on a separate micro-satellite launched with the main IMI spacecraft or with a separate pegasus launch, was considered and is discussed.

GALEX Distributes Local Galactic Treasures at AAS

NASA Technical Reports Server (NTRS)

2006-01-01

[figure removed for brevity, see original site] GALEX Poster

From sparkling blue rings to dazzling golden disks, Galaxy Evolution Explorer (Galex) scientists are handing out a collection of their finest galactic treasures at the January 2006 American Astronomical Society meeting in Washington, D.C.

Mined from the mission's Survey of Nearby Galaxies data, these cosmic gems were collected with the telescope's sensitive ultraviolet instruments. The gallery of galaxies has been made into a poster for meeting attendees visiting the mission's booth. Organized from far-ultraviolet to near-ultraviolet bright galaxies, this poster encapsulates the heart of the mission to study how galaxies and star formation rates have changed over the past 10 billion years.

Events in space take millions or billions of years to unfold, which means that astronomers can't watch individual galaxies and stars age over time. Luckily, because the physics of light travel dictates that the farther away an object is from Earth, the longer it takes for its light to travel to us, the universe can be thought of as a time machine. By building telescopes sensitive enough to capture objects that are 10 billion light-years away, astronomers can essentially see an object the way it looked 10 billion years ago. Galex astronomers are using this phenomenon to their advantage by taking snapshots of different galaxies at various distances in space. By comparing portraits of numerous objects at various times in the universe's history, the team can begin to piece together the life cycle of stars and galaxies.

For the poster, Galex scientists organized 196 different nearby galaxies in bins of increasing ultraviolet color. By placing the various snapshots side by side, astronomers can see how galaxies age differently. When viewed in ultraviolet, active star-forming regions in galaxies can be seen as glittering blue structures, while a soft, golden glow indicates the presence of older stars

Comparation between different tracers of SFR in the CALIFA sample

NASA Astrophysics Data System (ADS)

Catalán-Torrecilla, C.; Armando Gil de Paz, A.; África Castillo-Morales, A.; Jorge Iglesias-Páramo, J.; Almudena Alonso-Herrero, A.; Califa Team

2013-05-01

The Calar Alto Legacy Integral Field Area survey (CALIFA survey) has been designed to be the first survey to provide Integral Field Spectroscopy (IFS) data for a statistical sample of all galaxy types (˜ 600 galaxies) in the Local Universe (0.005UV range obtained by GALEX (GALaxy Evolution eXplorer) satellite at both far-UV (FUV) and near-UV (NUV) wavelengths and imaging data in the near-infrared (22 μm) from WISE. The main objective of our work will be to provide a robust determination of the star formation rate (SFR) in galaxies as a crucial element to understand galaxy evolution. We will focus on the analysis of this property using different tracers/calibrators: dust-extinction-corrected Hα-line emission (from CALIFA), FUV continuum (from GALEX), and infrared luminosities (from WISE). Besides a global comparison of the total SFR in the sample we will also identify those galaxies where these estimates clearly depart suggesting the presence of significant amounts of hidden star formation or variations in the IMF. Once these objects are identified we will study the spatial distribution of the different SFR tracers to know whether the discrepancies are ubiquitous in each galaxy or they are associated to specific, individual regions. The SFR are derived using both simple and hybrid recipes (see Calzetti 2012 for a recent compilation). In the case of the recipes based on a single photometric band (simple) we have used the extinction-corrected UV and Hα and the observed mid- or far-infrared luminosities. The hydrid ones combine luminosities measured directly (observed UV or Hα) with that of the light emitted by dust after being heated by young massive stars (in our case the WISE 22 μm luminosity). We have discovered that the results obtained depend in what calibrators we are using, in particular the SFR_{FUV} correlate well with SFR_{H_{α}} once both have been properly

DEEP ULTRAVIOLET LUMINOSITY FUNCTIONS AT THE INFALL REGION OF THE COMA CLUSTER

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hammer, D. M.; Hornschemeier, A. E.; Jenkins, L.

2012-02-01

We have used deep GALEX observations at the infall region of the Coma cluster to measure the faintest ultraviolet (UV) luminosity functions (LFs) presented for a rich galaxy cluster thus far. The Coma UV LFs are measured to M{sub UV} = -10.5 in the GALEX FUV and NUV bands, or 3.5 mag fainter than previous studies, and reach the dwarf early-type galaxy population in Coma for the first time. The Schechter faint-end slopes ({alpha} Almost-Equal-To -1.39 in both GALEX bands) are shallower than reported in previous Coma UV LF studies owing to a flatter LF at faint magnitudes. A Gaussian-plus-Schechtermore » model provides a slightly better parameterization of the UV LFs resulting in a faint-end slope of {alpha} Almost-Equal-To -1.15 in both GALEX bands. The two-component model gives faint-end slopes shallower than {alpha} = -1 (a turnover) for the LFs constructed separately for passive and star-forming galaxies. The UV LFs for star-forming galaxies show a turnover at M{sub UV} Almost-Equal-To -14 owing to a deficit of dwarf star-forming galaxies in Coma with stellar masses below M{sub *} = 10{sup 8} M{sub Sun }. A similar turnover is identified in recent UV LFs measured for the Virgo cluster suggesting this may be a common feature of local galaxy clusters, whereas the field UV LFs continue to rise at faint magnitudes. We did not identify an excess of passive galaxies as would be expected if the missing dwarf star-forming galaxies were quenched inside the cluster. In fact, the LFs for both dwarf passive and star-forming galaxies show the same turnover at faint magnitudes. We discuss the possible origin of the missing dwarf star-forming galaxies in Coma and their expected properties based on comparisons to local field galaxies.« less

Star Formation in Hi Tails: HCG 92, HCG 100 and 6 Interacting Systems

NASA Technical Reports Server (NTRS)

deMello, D. F.; Urrutia-Viscarra, F.; MendesdeOliveira, C.; Torres-Flores, S.; Carrasco, E. R.; Cypriano, E.

2012-01-01

We present new Gemini spectra of 14 new objects found within the HI tails of Hickson Compact Groups 92 and 100. Nine of them are GALEX Far-UV (FUV) and Near-UV (NUV) sources. The spectra confirm that these objects are members of the compact groups and have metallicities close to solar, with an average value of 12+log(O/H)approx.8.5. They have average FUV luminosities 7 x 10(exp 40) erg/s, very young ages (< 100 Myr) and two of them resemble tidal dwarf galaxies (TDGs) candidates. We suggest that they were created within gas clouds that were ejected during galaxy-galaxy interactions into the intergalactic medium, which would explain the high metallicities of the objects, inherited from the parent galaxies from which the gas originated. We conduct a search for similar objects in 6 interacting systems with extended HI tails, NGC 2623, NGC 3079, NGC 3359, NGC 3627, NGC 3718, NGC 4656. We found 35 UV sources with ages < 100 Myr, however most of them are on average less luminous/massive than the UV sources found around HCG 92 and 100. We speculate that this might be an environmental effect and that compact groups of galaxies are more favorable to TDG formation than other interacting systems.

THE GALEX/S{sup 4}G UV–IR COLOR–COLOR DIAGRAM: CATCHING SPIRAL GALAXIES AWAY FROM THE BLUE SEQUENCE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bouquin, Alexandre Y. K.; Gil de Paz, Armando; Gallego, Jesús

We obtained GALEX FUV, NUV, and Spitzer/IRAC 3.6 μm photometry for >2000 galaxies, available for 90% of the S{sup 4}G sample. We find a very tight GALEX blue sequence (GBS) in the (FUV–NUV) versus (NUV–[3.6]) color–color diagram, which is populated by irregular and spiral galaxies, and is mainly driven by changes in the formation timescale (τ) and a degeneracy between τ and dust reddening. The tightness of the GBS provides an unprecedented way of identifying star-forming galaxies and objects that are just evolving to (or from) what we call the GALEX green valley (GGV). At the red end of the GBS, atmore » (NUV–[3.6]) > 5, we find a wider GALEX red sequence (GRS) mostly populated by E/S0 galaxies that has a perpendicular slope to that of the GBS and of the optical red sequence. We find no such dichotomy in terms of stellar mass (measured by M{sub [3.6]}) since both massive (M{sub ⋆}>10{sup 11}M{sub ⊙}) blue- and red-sequence galaxies are identified. The type that is proportionally more often found in the GGV is the S0-Sa’s, and most of these are located in high-density environments. We discuss evolutionary models of galaxies that show a rapid transition from the blue to the red sequence on a timescale of 10{sup 8} yr.« less

Ten More New Sightlines for the Study of Intergalactic Helium, and Hundreds of Far-Ultraviolet-Bright Quasars, from the Sloan Digital Sky Survey, Galaxy Evolution Explorer, and Hubble Space Telescope

NASA Astrophysics Data System (ADS)

Syphers, David; Anderson, Scott F.; Zheng, Wei; Haggard, Daryl; Meiksin, Avery; Schneider, Donald P.; York, Donald G.

2009-11-01

Absorption along quasar sightlines remains among the most sensitive direct measures of He II reionization in much of the intergalactic medium (IGM). Until recently, fewer than a half-dozen unobscured quasar sightlines suitable for the He II Gunn-Peterson test were known; although these handful demonstrated great promise, the small sample size limited confidence in cosmological inferences. We have recently added nine more such clean He II quasars, exploiting Sloan Digital Sky Survey (SDSS) quasar samples, broadband ultraviolet (UV) imaging from Galaxy Evolution Explorer (GALEX), and high-yield UV spectroscopic confirmations from Hubble Space Telescope (HST). Here we markedly expand this approach by cross-correlating SDSS DR7 and GALEX GR4+5 to catalog 428 SDSS and 165 other quasars with z > 2.78 having likely (~70%) GALEX detections, suggesting they are bright into the far-UV. Reconnaissance HST Cycle 16 Supplemental prism data for 29 of these new quasar-GALEX matches spectroscopically confirm 17 as indeed far-UV bright. At least 10 of these confirmations have clean sightlines all the way down to He II Lyα, substantially expanding the number of known clean He II quasars, and reaffirming the order of magnitude enhanced efficiency of our selection technique. Combined confirmations from this and our past programs yield more than 20 He II quasars, quintupling the sample. These provide substantial progress toward a sample of He II quasar sightlines large enough, and spanning a sufficient redshift range, to enable statistical IGM studies that may avoid individual object peculiarity and sightline variance. Our expanded catalog of hundreds of high-likelihood far-UV-bright QSOs additionally will be useful for understanding the extreme-UV properties of the quasars themselves. Based on observations with the NASA/ESA Hubble Space Telescope obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc

VizieR Online Data Catalog: GALEX BCG galaxies sample properties (Boissier+, 2018)

NASA Astrophysics Data System (ADS)

Boissier, S.; Cucciati, O.; Boselli, A.; Mei, S.; Ferrarese, L.

2018-01-01

Tables 2 to 5 from the paper, providing the properties of a sample of 166 BCG galaxies with UV photometry from GALEX. In table 3 -9.999999 indicates galaxies for which no values is provided. (4 data files).

The Far Ultra-Violet Imager on the Icon Mission

NASA Astrophysics Data System (ADS)

Mende, S. B.; Frey, H. U.; Rider, K.; Chou, C.; Harris, S. E.; Siegmund, O. H. W.; England, S. L.; Wilkins, C.; Craig, W.; Immel, T. J.; Turin, P.; Darling, N.; Loicq, J.; Blain, P.; Syrstad, E.; Thompson, B.; Burt, R.; Champagne, J.; Sevilla, P.; Ellis, S.

2017-10-01

ICON Far UltraViolet (FUV) imager contributes to the ICON science objectives by providing remote sensing measurements of the daytime and nighttime atmosphere/ionosphere. During sunlit atmospheric conditions, ICON FUV images the limb altitude profile in the shortwave (SW) band at 135.6 nm and the longwave (LW) band at 157 nm perpendicular to the satellite motion to retrieve the atmospheric O/N2 ratio. In conditions of atmospheric darkness, ICON FUV measures the 135.6 nm recombination emission of O+ ions used to compute the nighttime ionospheric altitude distribution. ICON Far UltraViolet (FUV) imager is a Czerny-Turner design Spectrographic Imager with two exit slits and corresponding back imager cameras that produce two independent images in separate wavelength bands on two detectors. All observations will be processed as limb altitude profiles. In addition, the ionospheric 135.6 nm data will be processed as longitude and latitude spatial maps to obtain images of ion distributions around regions of equatorial spread F. The ICON FUV optic axis is pointed 20 degrees below local horizontal and has a steering mirror that allows the field of view to be steered up to 30 degrees forward and aft, to keep the local magnetic meridian in the field of view. The detectors are micro channel plate (MCP) intensified FUV tubes with the phosphor fiber-optically coupled to Charge Coupled Devices (CCDs). The dual stack MCP-s amplify the photoelectron signals to overcome the CCD noise and the rapidly scanned frames are co-added to digitally create 12-second integrated images. Digital on-board signal processing is used to compensate for geometric distortion and satellite motion and to achieve data compression. The instrument was originally aligned in visible light by using a special grating and visible cameras. Final alignment, functional and environmental testing and calibration were performed in a large vacuum chamber with a UV source. The test and calibration program showed that ICON

The development and characterization of advanced broadband mirror coatings for the far-UV

NASA Astrophysics Data System (ADS)

Egan, Arika; Fleming, Brian T.; Wiley, James; Quijada, Manuel; Del Hoyo, Javier; Hennessy, John; Hicks, Brian; France, Kevin; Kruczek, Nicholas; Erickson, Nicholas

2017-08-01

We present a progress report on the development of new broadband mirror coatings that demonstrate > 80% reflectivities from 1020-5000Å. Four different coating recipes are presented as candidates for future far-ultraviolet (FUV) sensitive broadband observatories. Three samples were first coated with aluminum (Al) and lithium fluoride (LiF) at the NASA Goddard Space Flight Center (GSFC) using a new high-temperature physical vapor deposition (PVD) process. Two of these samples then had an ultrathin (10-20 Å) protective coat of either magnesium fluoride (MgF2) or aluminum fluoride (AlF3) applied using atomic later deposition (ALD) at the NASA Jet Propulsion Laboratory (JPL). A fourth sample was coated with Al and a similar high temperature PVD coating of AlF3. Polarized reflectivities into the FUV for each sample were obtained through collaboration with the Synchrotron Ultraviolet Radiation Facility at the National Institute of Standards and Technology. We present a procedure for using these reflectivities as a baseline for calculating the optical constants of each coating recipe. Given these results, we describe plans for improving our measurement methodology and techniques to develop and characterize these coating recipes for future FUV missions.

Measurements of Lyman-Alpha Escape From HST Far-UV Spectral SNAP Survey of 33 Starforming Galaxies: Initial Results

NASA Astrophysics Data System (ADS)

Redwine, Keith

2018-01-01

This thesis will describe and analyze far-UV spectra from nearby starforming galaxies to investigate how line features like the hydrogen Lyman-alpha (Lyα) line at 1216 Å are related to the local properties of the host galaxy. It has been suggested that Lyα can be used as a proxy for the escape of Lyman continuum (LyC) radiation, the escape of of which from bright regions of galaxies is of particular interest. Most notably, the reionization epoch of neutral atomic hydrogen in the universe over a redshift range from z∼6 to z∼12, was highly dependent on the flux of ionizing LyC photons in the interstellar and intergalactic media. Expanding our understanding of the dynamics of the Lyα escape fraction (fLyα) from the local environment of its emission could be key to determining a total LyC escape fraction (fLyC) across all morphologies of galaxies. The wide range of Lyα emitters and absorbors (occasionally both) of this Cycle 22 SNAP survey observed by the Cosmic Origins Spectrograph (COS) onboard Hubble Space Telescope (HST) provides a unique look at far-UV spectra in candidate LyC emitters. Lyα profiles are easily observable in short exposures, and line features discernable in the low-resolution G140L mode can inform and guide future observations by COS or other FUV spectroscopy.

The Galex Time Domain Survey. I. Selection And Classification of Over a Thousand Ultraviolet Variable Sources

NASA Technical Reports Server (NTRS)

Gezari, S.; Martin, D. C.; Forster, K.; Neill, J. D.; Huber, M.; Heckman, T.; Bianchi, L.; Morrissey, P.; Neff, S. G.; Seibert, M.;

The GALEX Time Domain Survey. I. Selection and Classification of Over a Thousand Ultraviolet Variable Sources

NASA Astrophysics Data System (ADS)

Gezari, S.; Martin, D. C.; Forster, K.; Neill, J. D.; Huber, M.; Heckman, T.; Bianchi, L.; Morrissey, P.; Neff, S. G.; Seibert, M.; Schiminovich, D.; Wyder, T. K.; Burgett, W. S.; Chambers, K. C.; Kaiser, N.; Magnier, E. A.; Price, P. A.; Tonry, J. L.

2013-03-01

We present the selection and classification of over a thousand ultraviolet (UV) variable sources discovered in ~40 deg2 of GALEX Time Domain Survey (TDS) NUV images observed with a cadence of 2 days and a baseline of observations of ~3 years. The GALEX TDS fields were designed to be in spatial and temporal coordination with the Pan-STARRS1 Medium Deep Survey, which provides deep optical imaging and simultaneous optical transient detections via image differencing. We characterize the GALEX photometric errors empirically as a function of mean magnitude, and select sources that vary at the 5σ level in at least one epoch. We measure the statistical properties of the UV variability, including the structure function on timescales of days and years. We report classifications for the GALEX TDS sample using a combination of optical host colors and morphology, UV light curve characteristics, and matches to archival X-ray, and spectroscopy catalogs. We classify 62% of the sources as active galaxies (358 quasars and 305 active galactic nuclei), and 10% as variable stars (including 37 RR Lyrae, 53 M dwarf flare stars, and 2 cataclysmic variables). We detect a large-amplitude tail in the UV variability distribution for M-dwarf flare stars and RR Lyrae, reaching up to |Δm| = 4.6 mag and 2.9 mag, respectively. The mean amplitude of the structure function for quasars on year timescales is five times larger than observed at optical wavelengths. The remaining unclassified sources include UV-bright extragalactic transients, two of which have been spectroscopically confirmed to be a young core-collapse supernova and a flare from the tidal disruption of a star by dormant supermassive black hole. We calculate a surface density for variable sources in the UV with NUV < 23 mag and |Δm| > 0.2 mag of ~8.0, 7.7, and 1.8 deg-2 for quasars, active galactic nuclei, and RR Lyrae stars, respectively. We also calculate a surface density rate in the UV for transient sources, using the effective

VizieR Online Data Catalog: UV and IR properties for galaxies (Mao+, 2014)

NASA Astrophysics Data System (ADS)

Mao, Y.-W.; Kong, X.; Lin, L.

2017-03-01

Broadband FUV and NUV imaging data were obtained from GALEX observations and downloaded from the Multimission Archive at Space Telescope Science Institute (MAST) Web site (http://galex.stsci.edu/); 8um (dust-only) and 24um images were observed by the Spitzer Space Telescope (Spitzer) and retrieved from the SINGS data distribution service (http://irsa.ipac.caltech.edu/data/SPITZER/SINGS/). Hα narrowband imaging data are also employed in this work. The Hα narrowband image for NGC 3031 was observed by the 60/90 cm Schmidt telescope at Xing-Long station of the National Astronomical Observatories of China with the filter of transmission profile FWHM~120Å. (2 data files).

GALEX Imaging Study of the HI Filaments in M81 Group

NASA Astrophysics Data System (ADS)

Yun, Min

We propose to obtain sensitive, wide-field GALEX NUV and FUV images of the area surrounding the central four main members of the M81 group (M81, M82, NGC~2976, NGC~3077) as an integral part of our multi-wavelength observational program to explore the star formation activity, associated radiation field, and details of galaxy evolution/transformation within the group. We will add two pointings adjacent to the Cy-1 program pointing of the M81-M82 field by Huchra et al. (GI1-071) to the same depth (sufficient to detect star formation activity expected for a mean HI column density of a few times 10^18 per cm^2 with S/N>5) to cover most of the 3 degree diameter region we have imaged in 21cm HI line using the VLA, DRAO, and GBT. By combining with our imaging data from IR (Spitzer Cy-2), optical/IR (SDSS, 2MASS), and CO (FCRAO) surveys, we will conduct an extensive quantitative analysis on the distribution of cold gas and dust and star formation activity traced in UV and IR associated with the extensive array of HI tidal streamers. Because of its proximity, M81 group is one of the few extragalactic systems where such analysis can be made at spatial resolution of 100 pc or better. The high quality HI, CO, and dust maps (plus the dyanmical models for the group interactions) make this group an exceptional laboratory for determining the star formation and tidal dwarf formation process.

Enhanced Aluminum Reflecting and Solar-Blind Filter Coatings for the Far-Ultraviolet

NASA Technical Reports Server (NTRS)

Del Hoyo, Javier; Quijada, Manuel

2017-01-01

The advancement of far-ultraviolet (FUV) coatings is essential to meet the specified throughput requirements of the Large UV/Optical/IR (LUVOIR) Surveyor Observatory which will cover wavelengths down to the 100 nm range. The biggest constraint in the optical thin film coating design is attenuation in the Lyman-Alpha Ultraviolet range of 100-130 nm in which conventionally deposited thin film materials used in this spectral region (e.g. aluminum [Al] protected with Magnesium fluoride [MgF2]) often have high absorption and scatter properties degrading the throughput in an optical system. We investigate the use of optimally deposited aluminum and aluminum tri-fluoride (AlF3) materials for reflecting and solar blind band-pass filter coatings for use in the FUV. Optical characterization of the deposited designs has been performed using UV spectrometry. The optical thin film design and optimal deposition conditions to produce superior reflectance and transmittance using Al and AlF3 are presented.

Enhanced aluminum reflecting and solar-blind filter coatings for the far-ultraviolet

NASA Astrophysics Data System (ADS)

Del Hoyo, Javier; Quijada, Manuel

2017-09-01

The advancement of far-ultraviolet (FUV) coatings is essential to meet the specified throughput requirements of the Large UV/Optical/IR (LUVOIR) Surveyor Observatory which will cover wavelengths down to the 100 nm range. The biggest constraint in the optical thin film coating design is attenuation in the Lyman-Alpha Ultraviolet range of 100-130 nm in which conventionally deposited thin film materials used in this spectral region (e.g., aluminum [Al] protected with Magnesium fluoride [MgF2]) often have high absorption and scatter properties degrading the throughput in an optical system. We investigate the use of optimally deposited aluminum and aluminum tri-fluoride (AlF3) materials for reflecting and solar blind band-pass filter coatings for use in the FUV. Optical characterization of the deposited designs has been performed using UV spectrometry. The optical thin film design and optimal deposition conditions to produce superior reflectance and transmittance using Al and AlF3 are presented.

First Detection of a Pulsar Bow Shock Nebula in Far-UV: PSR J0437-4715

NASA Astrophysics Data System (ADS)

Rangelov, Blagoy; Pavlov, George G.; Kargaltsev, Oleg; Durant, Martin; Bykov, Andrei M.; Krassilchtchikov, Alexandre

2016-11-01

Pulsars traveling at supersonic speeds are often accompanied by cometary bow shocks seen in Hα. We report on the first detection of a pulsar bow shock in the far-ultraviolet (FUV). We detected it in FUV images of the nearest millisecond pulsar J0437-4715 obtained with the Hubble Space Telescope. The images reveal a bow-like structure positionally coincident with part of the previously detected Hα bow shock, with an apex at 10″ ahead of the moving pulsar. Its FUV luminosity, L(1250{--}2000 \\mathringA )≈ 5 × {10}28 erg s-1, exceeds the Hα luminosity from the same area by a factor of 10. The FUV emission could be produced by the shocked interstellar medium matter or, less likely, by relativistic pulsar wind electrons confined by strong magnetic field fluctuations in the bow shock. In addition, in the FUV images we found a puzzling extended (≃3″ in size) structure overlapping with the limb of the bow shock. If related to the bow shock, it could be produced by an inhomogeneity in the ambient medium or an instability in the bow shock. We also report on a previously undetected X-ray emission extending for about 5″ ahead of the pulsar, possibly a pulsar wind nebula created by shocked pulsar wind, with a luminosity L(0.5-8 keV) ˜ 3 × 1028 erg s-1. Based on observations made with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. These observations are associated with programs GO 12917 and GO 10568.

Optical design for CETUS: a wide-field 1.5m aperture UV payload being studied for a NASA probe class mission study

NASA Astrophysics Data System (ADS)

Woodruff, Robert A.; Hull, Tony; Heap, Sara R.; Danchi, William; Kendrick, Stephen E.; Purves, Lloyd

2017-09-01

We are developing a NASA Headquarters selected Probe-class mission concept called the Cosmic Evolution Through UV Spectroscopy (CETUS) mission, which includes a 1.5-m aperture diameter large field-of-view (FOV) telescope optimized for UV imaging, multi-object spectroscopy, and point-source spectroscopy. The optical system includes a Three Mirror Anastigmatic (TMA) telescope that simultaneously feeds three separate scientific instruments: the near-UV (NUV) Multi-Object Spectrograph (MOS) with a next-generation Micro-Shutter Array (MSA); the two-channel camera covering the far-UV (FUV) and NUV spectrum; and the point-source spectrograph covering the FUV and NUV region with selectable R 40,000 echelle modes and R 2,000 first order modes. The optical system includes fine guidance sensors, wavefront sensing, and spectral and flat-field in-flight calibration sources. This paper will describe the current optical design of CETUS.

Optical design for CETUS: a wide-field 1.5m aperture UV payload being studied for a NASA probe class mission study

NASA Astrophysics Data System (ADS)

Woodruff, Robert; Robert Woodruff, Goddard Space Flight Center, Kendrick Optical Consulting

2018-01-01

We are developing a NASA Headquarters selected Probe-class mission concept called the Cosmic Evolution Through UV Spectroscopy (CETUS) mission, which includes a 1.5-m aperture diameter large field-of-view (FOV) telescope optimized for UV imaging, multi-object spectroscopy, and point-source spectroscopy. The optical system includes a Three Mirror Anastigmatic (TMA) telescope that simultaneously feeds three separate scientific instruments: the near-UV (NUV) Multi-Object Spectrograph (MOS) with a next-generation Micro-Shutter Array (MSA); the two-channel camera covering the far-UV (FUV) and NUV spectrum; and the point-source spectrograph covering the FUV and NUV region with selectable R~ 40,000 echelle modes and R~ 2,000 first order modes. The optical system includes fine guidance sensors, wavefront sensing, and spectral and flat-field in-flight calibration sources. This paper will describe the current optical design of CETUS.

Third COS FUV Lifetime Position: FUV Target Acquisition Parameter Update {LENA3}

NASA Astrophysics Data System (ADS)

Penton, Steven

2013-10-01

Verify the ability of the Cycle 22 COS FSW to place an isolated point source at the center of the PSA, using FUV dispersed light target acquisition (TA) from the object and all three FUV gratings at the Third Lifetime Position (LP3). This program is modeled from the activity summary of LENA3.This program should be executed after the LP3 HV, XD spectral positions, aperture mechanism position, and focus are determined and updated. In addition, initial estimates of the LIFETIME=ALTERNATE TA FSW parameters and subarrays should be updated prior to execution of this program. After Visit 01, the subarrays will be updated. After Visit 2, the FUV WCA-to-PSA offsets will be updateded. Prior to Visit 6, LV56 will be installed will include new values for the LP3 FUV plate scales. VISIT 6 exposures use the default lifetime position (LP3).NUV imaging TAs have previously been used to determine the correct locations for FUV spectra. We follow the same procedure here.Note that the ETC runs here were made using ETC22.2 and are therefore valid for Mach 2014. Some TDS drop will likely have occured before these visits execute, but we have plenty of count to go what we need to do in this program.

Planetary nebulae with UVIT: Far ultra-violet halo around the Bow Tie nebula (NGC 40)

NASA Astrophysics Data System (ADS)

Kameswara Rao, N.; Sutaria, F.; Murthy, J.; Krishna, S.; Mohan, R.; Ray, A.

2018-01-01

Context. NGC 40 is a planetary nebula with diffuse X-ray emission, suggesting an interaction of the high-speed wind from WC8 central star (CS) with the nebula. It shows strong C IV 1550 Å emission that cannot be explained by thermal processes alone. We present here the first map of this nebula in C IV emission using broad band filters on the Ultra-Violet Imaging Telescope (UVIT). Aim. We aim to map the hot C IV-emitting gas and its correspondence with soft X-ray (0.3-8 keV) emitting regions in order to study the shock interaction between the nebula and the ISM. We also aim to illustrate the potential of UVIT for nebular studies. Methods: We carry out a morphological study of images of the nebula obtained at an angular resolution of about 1.3″ in four UVIT filter bands that include C IV 1550 Å and [C II] 2326 Å lines as well as UV continuum. We also make comparisons with X-ray, optical, and IR images from the literature. Results: The [C II] 2326 Å images show the core of the nebula with two lobes on either side of CS similar to [N II]. The C IV emission in the core shows similar morphology and extent to that of diffuse X-ray emission concentrated in nebular condensations. A surprising UVIT discovery is the presence of a large faint far UV (FUV) halo in an FUV filter with λeff of 1608 Å. The UV halo is not present in any other UV filter. The FUV halo is most likely due to UV fluorescence emission from the Lyman bands of H2 molecules. Unlike the optical and IR halo, the FUV halo trails predominantly towards the south-east side of the nebular core, opposite to the CS's proper motion direction. Conclusions: Morphological similarity of C IV 1550 Å and X-ray emission in the core suggests that it results mostly from the interaction of strong CS wind with the nebula. The FUV halo in NGC 40 highlights the extensive existence of H2 molecules in the regions even beyond the optical and IR halos. Thus UV studies are important to estimate the amount of H2, which is

Modelling the diffuse dust emission around Orion

NASA Astrophysics Data System (ADS)

Saikia, Gautam; Shalima, P.; Gogoi, Rupjyoti

2018-06-01

We have studied the diffuse radiation in the surroundings of M42 using photometric data from the Galaxy Evolution Explorer (GALEX) in the far-ultraviolet (FUV) and infrared observations of the AKARI space telescope. The main source of the FUV diffuse emission is the starlight from the Trapezium stars scattered by dust in front of the nebula. We initially compare the diffuse FUV with the far-infrared (FIR) observations at the same locations. The FUV-IR correlations enable us to determine the type of dust contributing to this emission. We then use an existing model for studying the FUV dust scattering in Orion to check if it can be extended to regions away from the centre in a 10 deg radius. We obtain an albedo, α = 0.7 and scattering phase function asymmetry factor, g = 0.6 as the median values for our dust locations on different sides of the central Orion region. We find a uniform value of optical parameters across our sample of locations with the dust properties varying significantly from those at the centre of the nebula.

Enhanced Fluoride Over-Coated Al Mirrors for FUV Astronomy

NASA Technical Reports Server (NTRS)

Quijada, Manuel A.; DelHoyo, Javier; Rice, Steve; Threat, Felix

2014-01-01

Astronomical observations in the Far Ultraviolet (FUV) spectral region are some of the more challenging due to the very distant and faint objects that are typically searched for in cosmic origin studies such as origin of large scale structure, the formation, evolution, and age of galaxies and the origin of stellar and planetary systems. These challenges are driving the need to improve the performance of optical coatings over a wide spectral range that would increase reflectance in mirrors and reduced absorption in dielectric filters used in optical telescope for FUV observations. This paper will present recent advances in reflectance performance for Al+MgF2 mirrors optimized for Lyman-alpha wavelength by performing the deposition of the MgF2 overcoat at elevated substrate temperatures. We will also present optical characterization of little studied rare-earth fluorides such as GdF3 and LuF3 that exhibit low-absorption over a wide wavelength range and could therefore be used as high refractive index alternatives for dielectric coatings at FUV wavelengths.

Second COS FUV Lifetime Position: FUV Target Acquisition Parameter Update {FENA4}

NASA Astrophysics Data System (ADS)

Penton, Steven

2011-10-01

Verify the ability of the Cycle 20 COS FSW to place an isolated point source at the center of the PSA, using FUV dispersed light target acquisition {TA} from the object and all three FUV gratings at the Second Lifetime Position {SLP}. This program is modeled from the activity summary of FENA4.This program should be executed after the new HV, XD spectral positions, and focus are determined and updated. In addition, the LIFETIME=ALTERNATE TA FSW parameters should be updated prior to execution of this program.NUV imaging TAs have previously been used to determine the correct locations for FUV spectra. We follow the same procedure here.

(F)UV Spectral Analysis of 15 Hot, Hydrogen-Rich Central Stars of PNe

NASA Astrophysics Data System (ADS)

Ziegler, Marc

2013-07-01

The aim of this thesis was the precise determination of basic stellar parameters and metal abundances for a sample of 15 ionizing stars of gaseous nebulae. Strategic lines of metals for the expected parameter range are located in the ultraviolet (UV) and far-ultraviolet (FUV) range. Thus high-resolution, high-S/N UV and FUV observations obtained with the Hubble Space Telescope (HST) and the Far Ultraviolet Spectroscopic Explorer (FUSE) were used for the analysis. For the calculation of the necessary spectral energy distributions the Tübingen NLTE Model-Atmosphere Package (TMAP) was used. The model atmospheres included most elements from H - Ni in order to account for line-blanketing effects. For each object a small grid of model atmospheres was calculated. As the interstellar medium (ISM) imprints its influence in the Space Telescope Imaging Spectrograph (STIS) and especially the FUSE range, the program OWENS was employed to calculate the interstellar absorption features. Both, the photospheric model spectral energy distribution (SED) as well as the ISM models were combined to enable the identification of most of the observed absorption lines. The analyzed sample covers a range of 70 kK < Teff < 136 kK, and surface gravities from log (g/cm/sec^2) = 5.4 - 7.4, thus representing different stages of stellar evolution. For a large number of elements, abundances were determined for the first time in these objects. Lines of C, N, O, F, Ne, Si, P, S, and Ar allowed to determine the corresponding abundances. For none of the objects lines of Ca, Sc, Ti, and V could be found. Only a few objects were rich in Cr, Mn, Fe, Co, and Ni lines. Most of the analyzed stars exhibited only lines of Fe (ionization stages V - VIII) from the iron-group elements. No signs for gravitational settling (the gravitational force exceeds the radiation pressure and elements begin to sink from the atmosphere into deeper layers) were found. This is expected as the values of the surface gravities of

The panchromatic Hubble Andromeda Treasury. VI. The reliability of far-ultraviolet flux as a star formation tracer on subkiloparsec scales

DOE Office of Scientific and Technical Information (OSTI.GOV)

Simones, Jacob E.; Skillman, Evan D.; Weisz, Daniel R.

We have used optical observations of resolved stars from the Panchromatic Hubble Andromeda Treasury to measure the recent (<500 Myr) star formation histories (SFHs) of 33 far-UV (FUV)-bright regions in M31. The region areas ranged from ∼10{sup 4} to 10{sup 6} pc{sup 2}, which allowed us to test the reliability of FUV flux as a tracer of recent star formation on subkiloparsec scales. The star formation rates (SFRs) derived from the extinction-corrected observed FUV fluxes were, on average, consistent with the 100 Myr mean SFRs of the SFHs to within the 1σ scatter. Overall, the scatter was larger than themore » uncertainties in the SFRs and particularly evident among the smallest regions. The scatter was consistent with an even combination of discrete sampling of the initial mass function and high variability in the SFHs. This result demonstrates the importance of satisfying both the full-IMF and the constant-SFR assumptions for obtaining precise SFR estimates from FUV flux. Assuming a robust FUV extinction correction, we estimate that a factor of 2.5 uncertainty can be expected in FUV-based SFRs for regions smaller than 10{sup 5} pc{sup 2} or a few hundred parsecs. We also examined ages and masses derived from UV flux under the common assumption that the regions are simple stellar populations (SSPs). The SFHs showed that most of the regions are not SSPs, and the age and mass estimates were correspondingly discrepant from the SFHs. For those regions with SSP-like SFHs, we found mean discrepancies of 10 Myr in age and a factor of 3-4 in mass. It was not possible to distinguish the SSP-like regions from the others based on integrated FUV flux.« less

Polarizers tuned at key far-UV spectral lines for space instrumentation

NASA Astrophysics Data System (ADS)

Larruquert, Juan I.; Malvezzi, A. Marco; Rodríguez-de Marcos, Luis; Giglia, Angelo; Gutiérrez-Luna, Nuria; Espinosa-Yáñez, Lucía.; Honrado-Benítez, Carlos; Aznárez, José A.; Massone, Giuseppe; Capobianco, Gerardo; Fineschi, Silvano; Nannarone, Stefano

2017-05-01

Polarimetry is a valuable technique to help us understand the role played by the magnetic field of the coronal plasma in the energy transfer processes from the inner parts of the Sun to the outer space. Polarimetry in the far ultraviolet (FUV: 100-200 nm), which must be performed from space due to absorption in terrestrial atmosphere, supplies fundamental data of processes that are governed by the Doppler and Hanle effects on resonantly scattered line-emission. To observe these processes there are various key spectral lines in the FUV, from which H I Lyman α (121.6 nm) is the strongest one. Hence some solar physics missions that have been proposed or are under development plan to perform polarimetry at 121.6 nm, like the suborbital missions CLASP I (2015) and CLASP II (2018), and the proposed solar missions SolmeX and COMPASS and stellar mission Arago. Therefore, the development of efficient FUV linear polarizers may benefit these and other possible future missions. C IV (155 nm) and Mg II (280 nm) are other spectral lines relevant for studies of solar and stellar magnetized atmospheres. High performance polarizers can be obtained with optimized coatings. Interference coatings can tune polarizers at the spectral line(s) of interest for solar and stellar physics. Polarizing beamsplitters consist in polarizers that separate one polarization component by reflection and the other by transmission, which enables observing the two polarization components simultaneously with a single polarizer. They involve the benefit of a higher efficiency in collection of polarization data due to the use of a single polarizer for the two polarization components and they may also facilitate a simplified design for a space polarimeter. We present results on polarizing beamsplitters tuned either at 121.6 nm or at the pair of 155 and 280 nm spectral lines.

SWIFT Observations of a Far UV Luminosity Component in SS433

NASA Technical Reports Server (NTRS)

Cannizzo, J. K.; Boyd, P. T.; Dolan, J. F.

2007-01-01

SS433 is a binary system showing relativistic Doppler shifts in its two sets of emission lines. The origin of its UV continuum is not well established. We observed SS433 to determine the emission mechanism responsible for its far UV spectrum. The source was observed at several different phases of both its 13 d orbital period and 162.5 d precession period using the UVOT and XRT detector systems on Swift. The far UV spectrum down to 1880 Angstrom lies significantly above the spectral flux distribution predicted by extrapolating the reddened blackbody continuum that fits the spectrum above 3500 Angstroms. The intensity of the far UV flux varies over a period of days and the variability is correlated with the variability of the soft X-ray flux from the source. An emission mechanism in addition to those previously detected in the optical and X-ray regions must exist in the far UV spectrum of SS433.

Uv-bright Nearby Early-type Galaxies Observed in the Mid-infrared: Eidence for a Multi-stage Formation History by Way of WISE and GALEX Imaging

NASA Technical Reports Server (NTRS)

Petty, S. M.; Neill, J. D.; Jarrett, T. H.; Blain, A. W.; Farrah, D. G.; Rich, R. M.; Tsai, C.-W.; Benford, D. J.; Bridge, C. R.; Lake, S. E.;

UV-BRIGHT NEARBY EARLY-TYPE GALAXIES OBSERVED IN THE MID-INFRARED: EVIDENCE FOR A MULTI-STAGE FORMATION HISTORY BY WAY OF WISE AND GALEX IMAGING

DOE Office of Scientific and Technical Information (OSTI.GOV)

Petty, S. M.; Farrah, D. G.; Neill, J. D.

2013-10-01

In the local universe, 10% of massive elliptical galaxies are observed to exhibit a peculiar property: a substantial excess of ultraviolet emission than what is expected from their old, red stellar populations. Several origins for this ultraviolet excess (UVX) have been proposed including a population of hot young stars and a population of old, blue horizontal branch or extended horizontal branch (BHB or EHB) stars that have undergone substantial mass loss from their outer atmospheres. We explore the radial distribution of UVX in a selection of 49 nearby E/S0-type galaxies by measuring their extended photometry in the UV through mid-infraredmore » (mid-IR) with the Galaxy Evolution Explorer (GALEX), the Sloan Digital Sky Survey, and the Wide-field Infrared Survey Explorer (WISE). We compare UV/optical and UV/mid-IR colors with the Flexible Stellar Population Synthesis models, which allow for the inclusion of EHB stars. We find that combined WISE mid-IR and GALEX UV colors are more effective in distinguishing models than optical colors, and that the UV/mid-IR combination is sensitive to the EHB fraction. There are strong color gradients, with the outer radii bluer than the inner half-light radii by {approx}1 mag. This color difference is easily accounted for with an increase in the BHB fraction of 0.25 with radius. We estimated that the average ages for the inner and outer radii are 7.0 {+-} 0.3 Gyr, and 6.2 {+-} 0.2 Gyr, respectively, with the implication that the outer regions are likely to have formed {approx}1 Gyr after the inner regions. Additionally, we find that metallicity gradients are likely not a significant factor in the color difference. The separation of color between the inner and outer regions, which agrees with a specific stellar population difference (e.g., higher EHB populations), and the {approx}0.5-2 Gyr age difference suggests multi-stage formation. Our results are best explained by inside-out formation: rapid star formation within the core

Galex Lyman-alpha Emitters: Physical Properties, Luminosity Bimodality, And Morphologies.

NASA Astrophysics Data System (ADS)

Mallery, Ryan P.

2010-01-01

The Galaxy Evolution Explorer spectroscopic survey has uncovered a large statistically significant sample of Lyman-alpha emitters at z sim0.3. ACS imaging of these sources in the COSMOS and AEGIS deep fields reveals that these Lyman-alpha emitters consist of two distinct galaxy morphologies, face on spiral galaxies and compact starburst/merging systems. The morphology bimodality also results in a bimodal distribution of optical luminosity. A comparison between the UV photometry and MIPS 24 micron detections of these sources indicates that they are bluer, and have less dust extinction than similar star forming galaxies that lack Lyman-alpha detection. Our findings show how the global gas and dust distribution of star forming galaxies inhibits Lyman-alpha emission in star forming galaxies. GALEX is a NASA Small Explorer, launched in April 2003. We gratefully acknowledge NASA's support for construction, operation, and science analysis for the GALEX mission, developed in cooperation with the CNES of France and the Korean Ministry of Science and Technology.

THE EFFECTS OF EPISODIC STAR FORMATION ON THE FUV-NUV COLORS OF STAR FORMING REGIONS IN OUTER DISKS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Barnes, Kate L.; Van Zee, Liese; Dowell, Jayce D., E-mail: barneskl@astro.indiana.edu, E-mail: vanzee@astro.indiana.edu, E-mail: jdowell@unm.edu

2013-09-20

We run stellar population synthesis models to examine the effects of a recently episodic star formation history (SFH) on UV and Hα colors of star forming regions. Specifically, the SFHs we use are an episodic sampling of an exponentially declining star formation rate (SFR; τ model) and are intended to simulate the SFHs in the outer disks of spiral galaxies. To enable comparison between our models and observational studies of star forming regions in outer disks, we include in our models sensitivity limits that are based on recent deep UV and Hα observations in the literature. We find significant dispersionmore » in the FUV-NUV colors of simulated star forming regions with frequencies of star formation episodes of 1 × 10{sup –8} to 4 × 10{sup –9} yr{sup –1}. The dispersion in UV colors is similar to that found in the outer disk of nearby spiral galaxies. As expected, we also find large variations in L{sub H{sub α}}/L{sub FUV}. We interpret our models within the context of inside-out disk growth, and find that a radially increasing τ and decreasing metallicity with an increasing radius will only produce modest FUV-NUV color gradients, which are significantly smaller than what is found for some nearby spiral galaxies. However, including moderate extinction gradients with our models can better match the observations with steeper UV color gradients. We estimate that the SFR at which the number of stars emitting FUV light becomes stochastic is ∼2 × 10{sup –6} M{sub ☉} yr{sup –1}, which is substantially lower than the SFR of many star forming regions in outer disks. Therefore, we conclude that stochasticity in the upper end of the initial mass function is not likely to be the dominant cause of dispersion in the FUV-NUV colors of star forming regions in outer disks. Finally, we note that if outer disks have had an episodic SFH similar to that used in this study, this should be taken into account when estimating gas depletion timescales and modeling

Initial observations of Jupiter's aurora from Juno's Ultraviolet Spectrograph (Juno-UVS)

NASA Astrophysics Data System (ADS)

Gladstone, R.; Versteeg, M.; Greathouse, T.; Hue, V.; Davis, M. W.; Gerard, J. C. M. C.; Grodent, D. C.; Bonfond, B.; Bolton, S. J.; Connerney, J. E. P.; Levin, S.; Bagenal, F.; Mauk, B.; Kurth, W. S.; McComas, D. J.; Valek, P. W.

2016-12-01

Juno-UVS is an imaging spectrograph with a bandpass of 70<λ<205 nm. This wavelength range includes important far-ultraviolet (FUV) emissions from the H2 bands and the H Lyman series which are produced in Jupiter's auroras, and also the absorption signatures of aurorally-produced hydrocarbons. The Juno-UVS instrument telescope has a 4x4 cm2 input aperture and uses an off-axis parabolic primary mirror. A flat scan mirror situated near the entrance of the telescope is used to observe at up to ±30° perpendicular to the Juno spin plane. The light is focused onto the spectrograph entrance slit, which has a "dog-bone" shape, with three sections of 2.55°x0.2°, 2.0°x0.025°, and 2.55°x0.2° (as projected onto the sky). Light entering the slit is dispersed by a toroidal grating which focuses FUV light onto a curved microchannel plate (MCP) cross delay line (XDL) detector with a solar blind UV-sensitive CsI photocathode. The two mirrors and the grating are coated with MgF2 to improve FUV reflectivity. Tantalum surrounds the spectrograph assembly to shield the detector and its electronics from high-energy electrons. All other electronics are located in Juno's spacecraft vault, including redundant low-voltage and high-voltage power supplies, command and data handling electronics, heater/actuator electronics, scan mirror electronics, and event processing electronics. The purpose of Juno-UVS is to remotely sense Jupiter's auroral morphology and brightness to provide context for in situ measurements by Juno's particle instruments. Here we present the first near-Jupiter results from the UVS instrument following measurements made during PJ1, Juno's first perijove pass with its instruments powered on and taking data.

Near-identical star formation rate densities from Hα and FUV at redshift zero

NASA Astrophysics Data System (ADS)

Audcent-Ross, Fiona M.; Meurer, Gerhardt R.; Wong, O. I.; Zheng, Z.; Hanish, D.; Zwaan, M. A.; Bland-Hawthorn, J.; Elagali, A.; Meyer, M.; Putman, M. E.; Ryan-Weber, E. V.; Sweet, S. M.; Thilker, D. A.; Seibert, M.; Allen, R.; Dopita, M. A.; Doyle-Pegg, M. T.; Drinkwater, M.; Ferguson, H. C.; Freeman, K. C.; Heckman, T. M.; Kennicutt, R. C.; Kilborn, V. A.; Kim, J. H.; Knezek, P. M.; Koribalski, B.; Smith, R. C.; Staveley-Smith, L.; Webster, R. L.; Werk, J. K.

2018-06-01

For the first time both Hα and far-ultraviolet (FUV) observations from an H I-selected sample are used to determine the dust-corrected star formation rate density (SFRD: \\dot{ρ }) in the local Universe. Applying the two star formation rate indicators on 294 local galaxies we determine log(\\dot{ρ } _{Hα }) = -1.68 ^{+0.13}_{-0.05} [M⊙ yr-1 Mpc-3] and log(\\dot{ρ }_{FUV}) = -1.71 ^{+0.12}_{-0.13} [M⊙ yr-1 Mpc-3]. These values are derived from scaling Hα and FUV observations to the H I mass function. Galaxies were selected to uniformly sample the full H I mass (M_{H I}) range of the H I Parkes All-Sky Survey (M_{H I} ˜ 107 to ˜1010.7 M⊙). The approach leads to relatively larger sampling of dwarf galaxies compared to optically-selected surveys. The low H I mass, low luminosity and low surface brightness galaxy populations have, on average, lower Hα/FUV flux ratios than the remaining galaxy populations, consistent with the earlier results of Meurer. The near-identical Hα- and FUV-derived SFRD values arise with the low Hα/FUV flux ratios of some galaxies being offset by enhanced Hα from the brightest and high mass galaxy populations. Our findings confirm the necessity to fully sample the H I mass range for a complete census of local star formation to include lower stellar mass galaxies which dominate the local Universe.

Enhancing the far-UV sensitivity of silicon CMOS imaging arrays

NASA Astrophysics Data System (ADS)

Retherford, K. D.; Bai, Yibin; Ryu, Kevin K.; Gregory, J. A.; Welander, Paul B.; Davis, Michael W.; Greathouse, Thomas K.; Winter, Gregory S.; Suntharalingam, Vyshnavi; Beletic, James W.

2014-07-01

We report our progress toward optimizing backside-illuminated silicon PIN CMOS devices developed by Teledyne Imaging Sensors (TIS) for far-UV planetary science applications. This project was motivated by initial measurements at Southwest Research Institute (SwRI) of the far-UV responsivity of backside-illuminated silicon PIN photodiode test structures described in Bai et al., SPIE, 2008, which revealed a promising QE in the 100-200 nm range as reported in Davis et al., SPIE, 2012. Our effort to advance the capabilities of thinned silicon wafers capitalizes on recent innovations in molecular beam epitaxy (MBE) doping processes. Key achievements to date include: 1) Representative silicon test wafers were fabricated by TIS, and set up for MBE processing at MIT Lincoln Laboratory (LL); 2) Preliminary far-UV detector QE simulation runs were completed to aid MBE layer design; 3) Detector fabrication was completed through the pre-MBE step; and 4) Initial testing of the MBE doping process was performed on monitoring wafers, with detailed quality assessments. Early results suggest that potential challenges in optimizing the UV-sensitivity of silicon PIN type CMOS devices, compared with similar UV enhancement methods established for CCDs, have been mitigated through our newly developed methods. We will discuss the potential advantages of our approach and briefly describe future development steps.

UV Reflectance of Jupiter's Moon Europa and Asteroid (16) Psyche

NASA Astrophysics Data System (ADS)

Becker, T. M.; Retherford, K. D.; Roth, L.; Hendrix, A.; McGrath, M. A.; Cunningham, N.; Feaga, L. M.; Saur, J.; Elkins-Tanton, L. T.; Walhund, J. E.; Molyneux, P.

2017-12-01

Surface reflectance observations of solar system objects in the UV are not only complimentary to longer wavelength observations for identifying surface composition, but can also reveal new and meaningful information about the surfaces of those bodies. On Europa, far-UV (FUV) spectral observations made by the Hubble Space Telescope (HST) show that the surface lacks a strong water ice absorption edge near 165 nm, which is intriguing because such a band has been detected on most icy satellites. This may suggest that radiolytic processing by Jupiter's magnetosphere has altered the surface, causing absorption at wavelengths longward of the H2O edge, masking this feature. Additionally, the FUV spectra are blue (increasing albedo with shorter wavelengths), and regions that are observed to be dark in the visible appear bright in the FUV. This spectral inversion, also observed on the Moon and some asteroids, may provide insight into the properties of the surface material and how they are processed.We also explore the UV reflectance spectra of the main belt asteroid (16) Psyche. This asteroid is believed to be the metallic remnant core of a differentiated asteroid, stripped of its mantle through collisions. However, there is speculation that the asteroid could have formed as-is from highly reduced metal-rich material near the Sun early in the formation of the solar system. Further, spectral observations in the infrared have revealed pyroxene and hydroxyl on the asteroid's surface, complicating the interpretation that (16) Psyche is a pure metallic object. Laboratory studies indicate that there are diagnostic spectral features in the UV that could be useful for determining the surface composition. We obtained HST observations of Psyche from 160 - 300 nm. Preliminary results show a featureless, red-sloped spectrum, inconsistent with significant amounts of pyroxene on the surface. We will present the spectra of Europa and the asteroid (16) Psyche and discuss the unique details

Measures of star formation rates from infrared (Herschel) and UV (GALEX) emissions of galaxies in the HerMES fields

NASA Astrophysics Data System (ADS)

Buat, V.; Giovannoli, E.; Burgarella, D.; Altieri, B.; Amblard, A.; Arumugam, V.; Aussel, H.; Babbedge, T.; Blain, A.; Bock, J.; Boselli, A.; Castro-Rodríguez, N.; Cava, A.; Chanial, P.; Clements, D. L.; Conley, A.; Conversi, L.; Cooray, A.; Dowell, C. D.; Dwek, E.; Eales, S.; Elbaz, D.; Fox, M.; Franceschini, A.; Gear, W.; Glenn, J.; Griffin, M.; Halpern, M.; Hatziminaoglou, E.; Heinis, S.; Ibar, E.; Isaak, K.; Ivison, R. J.; Lagache, G.; Levenson, L.; Lonsdale, C. J.; Lu, N.; Madden, S.; Maffei, B.; Magdis, G.; Mainetti, G.; Marchetti, L.; Morrison, G. E.; Nguyen, H. T.; O'Halloran, B.; Oliver, S. J.; Omont, A.; Owen, F. N.; Page, M. J.; Pannella, M.; Panuzzo, P.; Papageorgiou, A.; Pearson, C. P.; Pérez-Fournon, I.; Pohlen, M.; Rigopoulou, D.; Rizzo, D.; Roseboom, I. G.; Rowan-Robinson, M.; Sánchez Portal, M.; Schulz, B.; Seymour, N.; Shupe, D. L.; Smith, A. J.; Stevens, J. A.; Strazzullo, V.; Symeonidis, M.; Trichas, M.; Tugwell, K. E.; Vaccari, M.; Valiante, E.; Valtchanov, I.; Vigroux, L.; Wang, L.; Ward, R.; Wright, G.; Xu, C. K.; Zemcov, M.

2010-11-01

The reliability of infrared (IR) and ultraviolet (UV) emissions to measure star formation rates (SFRs) in galaxies is investigated for a large sample of galaxies observed with the Spectral and Photometric Imaging Receiver (SPIRE) and the Photodetector Array Camera and Spectrometer (PACS) instruments on Herschel as part of the Herschel Multi-Tiered Extragalactic Survey (HerMES) project. We build flux-limited 250-μm samples of sources at redshift z < 1, cross-matched with the Spitzer/MIPS and GALEX catalogues. About 60 per cent of the Herschel sources are detected in UV. The total IR luminosities, LIR, of the sources are estimated using a spectral energy distribution (SED) fitting code that fits to fluxes between 24 and 500 μm. Dust attenuation is discussed on the basis of commonly used diagnostics: the LIR/LUV ratio and the slope, β, of the UV continuum. A mean dust attenuation AUV of mag is measured in the samples. LIR/LUV is found to correlate with LIR. Galaxies with and 0.5 < z < 1 exhibit a mean dust attenuation AUV of about 0.7 mag lower than that found for their local counterparts, although with a large dispersion. Our galaxy samples span a large range of β and LIR/LUV values which, for the most part, are distributed between the ranges defined by the relations found locally for starburst and normal star-forming galaxies. As a consequence the recipe commonly applied to local starbursts is found to overestimate the dust attenuation correction in our galaxy sample by a factor of ~2-3. The SFRs deduced from LIR are found to account for about 90 per cent of the total SFR; this percentage drops to 71 per cent for galaxies with (or ). For these faint objects, one needs to combine UV and IR emissions to obtain an accurate measure of the SFR.

Pegasus XL GALEX

NASA Image and Video Library

2003-03-13

In the Multi-Payload Processing Facility, the Pegasus XL launch vehicle is in position for mating of the Galaxy Evolution Explorer (GALEX) satellite. The GALEX, set to launch April 2 from Cape Canaveral Air Force Station, will carry into space an orbiting telescope that will observe a million galaxies across 10 billion years of cosmic history to help astronomers determine when the stars and elements we see today had their origins. The spacecraft will sweep the skies for 28 months using state-of-the-art ultraviolet detectors to single out galaxies dominated by young, hot, short-lived stars that give off a great deal of energy at that wavelength. These galaxies are actively creating stars, and therefore provide a window into the history and causes of star formation in galaxies.

Pegasus XL GALEX

NASA Image and Video Library

2003-03-13

In the Multi-Payload Processing Facility, the Pegasus XL launch vehicle waits for mating of the Galaxy Evolution Explorer (GALEX) satellite. The GALEX, set to launch April 2 from Cape Canaveral Air Force Station, will carry into space an orbiting telescope that will observe a million galaxies across 10 billion years of cosmic history to help astronomers determine when the stars and elements we see today had their origins. The spacecraft will sweep the skies for 28 months using state-of-the-art ultraviolet detectors to single out galaxies dominated by young, hot, short-lived stars that give off a great deal of energy at that wavelength. These galaxies are actively creating stars, and therefore provide a window into the history and causes of star formation in galaxies.

New Geometric-distortion Solution for STIS FUV-MAMA

NASA Astrophysics Data System (ADS)

Sohn, S. Tony

2018-04-01

We derived a new geometric distortion solution for the STIS FUV-MAMA detector. To do this, positions of stars in 89 FUV-MAMA observations of NGC 6681 were compared to an astrometric standard catalog created using WFC3/UVIS imaging data to derive a fourth-order polynomial solution that transforms raw (x, y) positions to geometrically- corrected (x, y) positions. When compared to astrometric catalog positions, the FUV- MAMA position measurements based on the IDCTAB showed residuals with an RMS of ∼ 30 mas in each coordinate. Using the new IDCTAB, the RMS is reduced to ∼ 4 mas, or 0.16 FUV-MAMA pixels, in each coordinate. The updated IDCTAB is now being used in the HST STIS pipeline to process all STIS FUV-MAMA images.

COS2025: Extending the Lifetime of the FUV channel of the Cosmic Origins Spectrograph to 2025

NASA Astrophysics Data System (ADS)

Rafelski, Marc; De Rosa, Gisella; Fischer, William J.; Fix, Mees; Fox, Andrew; Indriolo, Nick; James, Bethan; Magness, Camellia; Oliveira, Cristina M.; Penton, Steven V.; Plesha, Rachel; Roman-Duval, Julia; Sahnow, David J.; Sankrit, Ravi; Snyder, Elaine M.; Taylor, Joanna M.; White, James

2018-01-01

The Hubble Space Telescope's Cosmic Origins Spectrograph (COS) Far-Ultraviolet (FUV) microchannel plate detector's efficiency at converting incoming photons into detectable events decreases with usage. This depletion of the detector's gain (i.e. gain sag) results in unusable regions of the COS/FUV detector. In order to mitigate this gain sag, a number of strategies have been employed over the past 8 years of operations, ranging from moving to different lifetime positions, to managing the high voltage to extract a smaller amount of charge, to re-distributing the cenwave usage so that Ly-alpha does not produce a gain-sag hole in a given location. We are now at a point where none of the strategies above will, without any other changes, allow us to continue operating the COS/FUV detector to 2025. To address this a new COS2025 policy was developed, with the goal of retaining full science capability of COS/FUV to 2025. We present an overview of the COS2025 policy, which places restrictions on the G130M cenwaves allowed at Lifetime Position 4 (LP4). We also present a tool which allows users to visualize the COS/FUV wavelength ranges to help users prepare their proposals in the light of the restrictions on the G130M cenwaves.

THE COMPLEX NORTH TRANSITION REGION OF CENTAURUS A: A GALACTIC WIND

DOE Office of Scientific and Technical Information (OSTI.GOV)

Neff, Susan G.; Eilek, Jean A.; Owen, Frazer N., E-mail: susan.g.neff@nasa.gov

2015-04-01

We present deep GALEX images of NGC 5128, the parent galaxy of Centaurus A. We detect a striking “weather ribbon” of far-UV (FUV) and Hα emission which extends more than 35 kpc northeast of the galaxy. This ribbon is associated with a knotty ridge of radio/X-ray emission and is an extension of the previously known string of optical emission-line filaments. Many phenomena in the region are too short-lived to have survived transit out from the inner galaxy; something must be driving them locally. We also detect FUV emission from the galaxy’s central dust lane. Combining this with previous radio andmore » far-IR measurements, we infer an active starburst in the central galaxy which is currently forming stars at ∼2 M{sub ☉} yr{sup −1}, and has been doing so for 50–100 Myr. If the wind from this starburst is enhanced by energy and mass driven out from the active galactic nucleus, the powerful augmented wind can be the driver needed for the northern weather system. We argue that both the diverse weather system, and the enhanced radio emission in the same region, result from the wind’s encounter with cool gas left by one of the recent merger/encounter events in the history of NGC 5128.« less

UV Timing and Spectroscopy of the Crab Nebula Pulsar

NASA Technical Reports Server (NTRS)

Gull, Theodore R.; Lunqvist, Peter; Sollerman, Jesper; Lindler, Don; Fisher, Richard R. (Technical Monitor)

2001-01-01

We have used the Hubble Space Telescope and Space Telescope Imaging Spectrograph to obtain Near Ultraviolet (NUV) (1600-3200 Angstroms) and Far Ultraviolet (FUV) (1140-1720 Angstroms) spectra and pulse profiles of the Crab Nebula's pulsar. The pulse period agrees well with the radio predictions. The NUV and FUV pulse profiles are little changed from the visible wavelength profile. Spectra obtained with the Nordic Optical Telescope were combined with the UV spectra for full coverage from 1140-9250Angstoms. Dereddening the spectrum with a standard extinction curve achieves a flat spectrum for E(B-V)=0.52, R=3.1. Lyman alpha absorption indicates a column density of 3.0=/-0.5 x 10(exp 21) cm -2, consistent with the E(B-V) of 0.52. The dereddened spectrum can be fitted by a power law with spectral index alpha=0.11+/-0.04. A broad, blueshifted absorption is seen in CIV (1550Angstroms), reaching a velocity of about 2500 kilometer per second.

How Extreme is TRAPPIST-1? A look into the planetary system’s extreme-UV radiation environment

NASA Astrophysics Data System (ADS)

Peacock, Sarah; Barman, Travis; Shkolnik, Evgenya L.

2018-01-01

The ultracool dwarf star TRAPPIST-1 hosts three earth-sized planets at orbital distances where water has the potential to exist in liquid form on the planets’ surface. Close-in exoplanets, such as these, become vulnerable to water loss as stellar XUV radiation heats and expands their upper atmospheres. Currently, little is known about the high-energy radiation environment around TRAPPIST-1. Recent efforts to quantify the XUV radiation rely on empirical relationships based on X-ray or Lyman alpha line observations and yield very different results. The scaling relations used between the X-ray and EUV emission result in high-energy irradiation of the planets 10-1000x greater than present day Earth, stripping atmospheres and oceans in 1 Gyr, while EUV estimated from Lyman alpha flux is much lower. Here we present upper-atmosphere PHOENIX models representing the minimum and maximum potential EUV stellar flux from TRAPPIST-1. We use GALEX FUV and NUV photometry for similar aged M stars to determine the UV flux extrema in an effort to better constrain the high-energy radiation environment around TRAPPIST-1.

GALEX 1st Light Far Ultraviolet

NASA Image and Video Library

2003-05-28

This image was taken May 21 and 22, 2003 by NASA Galaxy Evolution Explorer. The image was made from data gathered by the far ultraviolet channel of the spacecraft camera during the mission first light milestone. It shows about 400 celestial objects

(F)UV Spectroscopy of K648: Abundance Determination of Trace Elements

NASA Astrophysics Data System (ADS)

Mohamad-Yob, S. J.; Ziegler, M.; Rauch, T.; Werner, K.

2010-11-01

We present preliminary results of an ongoing spectral analysis of K 648, the central star of the planetary nebula Ps 1, based on high resolution FUV spectra. K 648, in M 15 is one of only four known PNe in globular clusters. The formation of this post-AGB object in a globular cluster is still unclear. Our aim is to determine Teff, log g, and the abundances of trace elements, in order to improve our understanding of post-AGB evolution of extremely metal-poor stars, especially PN formation in globular clusters. We analyzed FUSE, HST/STIS, and HST/FOS observations. A grid of stellar model atmospheres was calculated using the Tübingen NLTE Model Atmosphere Package (TMAP).

COS/FUV Special Recovery

NASA Astrophysics Data System (ADS)

Wheeler, Thomas

2011-10-01

This proposal consists of the steps necessary for turning on and ramping up {in magnitude} the COS FUV high voltage and returning the FUV detector to science operations in a conservative manner after a HV anomalous or burst event {similar to what has been seen on FUSE} shutdown. HSTAR 13305 provides details and timeline of the present shutdown. The complete step-by-step procedure is detailed in the Observing Description, but in summary, the following is done: Groups of sequences with one dayâ??s activities with the QE grid off and one dayâ??s activities with the QE grid on alternate to progressively higher voltages with the QE off group leading by one sequence. The initial HV turn on {Day 1} occurs with the QE grid off; the initial transition from FUV Operate to HVLow is broken into two parts with a 1- hour wait between turning the HV on and ramping to HVLow {SAA}. The next Day 1 visit is 1 hour later, where the HV is turned off by returning the FUV Operate state. After another1-hour wait, the QE grid is turned on, the HV is turned on and the voltage is not ramped. After another 1-hour wait, the HV is turned off returning to FUV Operate. The Day 1 ends with the NSSC-1 COS flag 3 is set to prevent any FUV HV commanding. This is followed by 10 cycles {2 * 5 cycles - one set of cycles with the grid off and one set with the grid on} of HV ramp-ups and returns to FUV Operate {HV off} alternating between grid off and on with the QE off group leading by one HV setting. The HV Commanded Counts for each group of cycles are: 154/151, 160/157, 166/163, 172/169, HVNom {178/175}. {The formula to convert Command Counts to HV is: Volts = {Command Counts * -15.69V} -2500V.}The QE off and QE on cycles are similar except for the QE commanding. One typical QE off cycle is shown below:V14 QE off - Ramp to 166/163After V10 by 2D for analysis. Flag 3 must be cleared to execute. 1. QE off - Turn HV on 2. Ramp to HVLow {100/100} 3. Ramp HV to 166/163 4. DCE RAM dump 5. Dark exposure 6

The FUV to Near-IR Morphologies of Luminous Infrared Galaxies in the Goals Sample

NASA Astrophysics Data System (ADS)

Petty, S. M.; Armus, L.; Charmandaris, V.; Evans, A. S.; Le Floc'h, E.; Bridge, C.; Díaz-Santos, T.; Howell, J. H.; Inami, H.; Psychogyios, A.; Stierwalt, S.; Surace, J. A.

2014-12-01

We compare the morphologies of a sample of 20 luminous infrared galaxies (LIRGs) from the Great Observatories All-sky LIRG Survey (GOALS) in the FUV, B, I, and H bands, using the Gini (G) and M20 parameters to quantitatively estimate the distribution and concentration of flux as a function of wavelength. Hubble Space Telescope (HST) images provide an average spatial resolution of ˜ 80 pc. While our LIRGs can be reliably classified as mergers across the entire range of wavelengths studied here, there is a clear shift toward more negative M20 (more bulge-dominated) and a less significant decrease in G values at longer wavelengths. We find no correlation between the derived FUV G-M20 parameters and the global measures of the IR to FUV flux ratio (IRX). Given the fine resolution in our HST data, this suggests either that the UV morphology and IRX are correlated on very small scales, or that the regions emitting the bulk of the IR emission emit almost no FUV light. We use our multi-wavelength data to simulate how merging LIRGs would appear from z˜ 0.5-3 in deep optical and near-infrared images such as the Hubble Ultra-Deep Field, and use these simulations to measure the G-M20 at these redshifts. Our simulations indicate a noticeable decrease in G, which flattens at z≥slant 2 by as much as 40%, resulting in mis-classifying our LIRGs as disk-like, even in the rest-frame FUV. The higher redshift values of M20 for the GOALS sources do not appear to change more than about 10% from the values at z˜ 0. The change in G-M20 is caused by the surface brightness dimming of extended tidal features and asymmetries, and also the decreased spatial resolution which reduced the number of individual clumps identified. This effect, seen as early as z˜ 0.5, could easily lead to an underestimate of the number of merging galaxies at high-redshift in the rest-frame FUV.

Far ultraviolet wide field imaging and photometry - Spartan-202 Mark II Far Ultraviolet Camera

NASA Technical Reports Server (NTRS)

Carruthers, George R.; Heckathorn, Harry M.; Opal, Chet B.; Witt, Adolf N.; Henize, Karl G.

1988-01-01

The U.S. Naval Research Laboratory' Mark II Far Ultraviolet Camera, which is expected to be a primary scientific instrument aboard the Spartan-202 Space Shuttle mission, is described. This camera is intended to obtain FUV wide-field imagery of stars and extended celestial objects, including diffuse nebulae and nearby galaxies. The observations will support the HST by providing FUV photometry of calibration objects. The Mark II camera is an electrographic Schmidt camera with an aperture of 15 cm, a focal length of 30.5 cm, and sensitivity in the 1230-1600 A wavelength range.

Observations of the Magnetic Cataclysmic Variable VV Puppis with the Far Ultraviolet Spectroscopic Explorer

NASA Astrophysics Data System (ADS)

Hoard, D. W.; Szkody, Paula; Ishioka, Ryoko; Ferrario, L.; Gänsicke, B. T.; Schmidt, Gary D.; Kato, Taichi; Uemura, Makoto

2002-10-01

We present the first far-ultraviolet (FUV) observations of the magnetic cataclysmic variable VV Puppis, obtained with the Far Ultraviolet Spectroscopic Explorer satellite. In addition, we have obtained simultaneous ground-based optical photometric observations of VV Pup during part of the FUV observation. The shapes of the FUV and optical light curves are consistent with each other and with those of past observations at optical, extreme-ultraviolet, and X-ray wavelengths. Time-resolved FUV spectra during the portion of VV Pup's orbit when the accreting magnetic pole of the white dwarf can be seen show an increasing continuum level as the accretion spot becomes more directly visible. The most prominent features in the spectrum are the O VI λλ1031.9, 1037.6 emission lines. We interpret the shape and velocity shift of these lines in the context of an origin in the accretion funnel near the white dwarf surface. A blackbody function with Tbb>~90,000 K provides an adequate fit to the FUV spectral energy distribution of VV Pup. Based on observations with the NASA-CNES-CSA Far Ultraviolet Spectroscopic Explorer. FUSE is operated for NASA by Johns Hopkins University under NASA contract NAS 5-32985.

Galex and Pan-STARRS1 Discovery of SN IIP 2010aq: The First Few Days After Shock Breakout in a Red Supergiant Star

DTIC Science & Technology

2010-09-01

compare the late- time (φ > 3 d) UV/optical light curve of SN 2010aq with two nearby Type IIP SNe well studied in the UV and optical with the Swift satellite ...following SN shock breakout in a red supergiant star. SN 2010aq was discovered in joint monitoring between the Galaxy Evolution Explorer (GALEX) Time ...simultaneous UV and optical photometry allows us to fit for a progenitor star radius of 700± 200R, the size of a red supergiant star. An excess in UV emission

HST FUV/NUV Photometry of the Putative Binary Companion to the SN 1993J Progenitor

NASA Astrophysics Data System (ADS)

Miles, Nathan; Fox, Ori; Azalee Bostroem, K.; Zheng, WeiKang; Graham, Melissa; Van Dyk, Schuyler D.; Filippenko, Alexei V.; Matheson, Thomas; Dwarkadas, Vikram; Fransson, Claes; Smith, Nathan; Brink, Thomas

2018-06-01

A previous analysis of HST/COS spectra from 2012 revealed an FUV excess consistent with the presence of the hypothetical B-star companion to the SN 1993J progenitor. The spectrum, however, had low signal-to-noise and was blended with several other nearby stars within the 2.5 arcsec COS aperture. Since that time, the SN has sufficiently faded allowing for more accurate photometry to be performed. Here we present follow-up HST FUV/NUV imaging using the F140LP filter on ACS/SBC and the F218W, F275W, and F336W filters on WFC3/UVIS. This photometry isolates the UV flux from only the putative companion. We will discuss whether this new evidence removes all ambiguity about the nature of the companion once and for all.

Far-ultraviolet to Near-infrared Spectroscopy of a Nearby Hydrogen-poor Superluminous Supernova Gaia16apd

NASA Astrophysics Data System (ADS)

Yan, Lin; Quimby, R.; Gal-Yam, A.; Brown, P.; Blagorodnova, N.; Ofek, E. O.; Lunnan, R.; Cooke, J.; Cenko, S. B.; Jencson, J.; Kasliwal, M.

2017-05-01

We report the first maximum-light far-ultraviolet (FUV) to near-infrared (NIR) spectra (1000 Å - 1.62 μm, rest) of a hydrogen-poor superluminous supernova, Gaia16apd. At z = 0.1018, it is the second closest and the UV brightest SLSN-I, with 17.4 mag in Swift UVW2 band at -11 days pre-maximum. The coordinated observations with HST, Palomar, and Keck were taken at -2 to +25 days. Assuming an exponential (or t 2) form, we derived the rise time of 33 days and the peak bolometric luminosity of 3 × 1044 erg s-1. At the maximum, the photospheric temperature and velocity are 17,000 K and 14,000 km s-1, respectively. The inferred radiative and kinetic energy are roughly 1 × 1051 and 2 × 1052 erg. Gaia16apd is extremely UV luminous, and emits 50% of its total luminosity at 1000-2500 Å. Compared to the UV spectra (normalized at 3100 Å) of well studied SN1992A (Ia), SN2011fe (Ia), SN1999em (IIP), and SN1993J (IIb), it has orders of magnitude more FUV emission. This excess is interpreted primarily as a result of weaker metal-line blanketing due to a much lower abundance of iron group elements in the outer ejecta. Because these elements originate either from the natal metallicity of the star, or have been newly produced, our observation provides direct evidence that little of these freshly synthesized material, including 56Ni, were mixed into the outer ejecta, and the progenitor metallicity is likely sub-solar. This disfavors Pair-instability Supernova models with helium core masses ≥slant 90 {M}⊙ , where substantial 56Ni material is produced. A higher photospheric temperature definitely contributes to the FUV excess from Gaia16apd. Compared with Gaia16apd, we find PS1-11bam is also UV luminous.

Implications of the SPEAR FUV Maps on Our Understanding of the ISM

NASA Astrophysics Data System (ADS)

Korpela, Eric J.; Sirk, Martin; Edelstein, Jerry; Seon, Kwangil; Min, Kyoung-Wook; Han, Wonyong

2009-08-01

The distribution of a low-density transition temperature (104.5-105.5 K) gas in the interstellar medium conveys the character and evolution of diffuse matter in the Galaxy. This difficult to observe component of the ISM emits mainly in the far-ultraviolet (FUV) (912-1800 A˚) band. We describe spectral maps of FUV emission lines from the highly ionized species CIV and OVI likely to be the dominant cooling mechanisms of transition temperature gas in the ISM. The maps were obtained using an orbital spectrometer, SPEAR, that was launched in 2003 and has observed the FUV sky with a spectral resolution of ~550 and an angular resolution of 10'. We compare distribution of flux in these maps with three basic models of the distribution of transition temperature gas. We find that the median distribution of CIV and OVI emission is consistent with the spatial distribution and line ratios expected from a McKee-Ostriker (MO) type model of evaporative interfaces. However, the intensities are a factor of three higher than would be expected at the MO preferred parameters. Some high intensity regions are clearly associated with supernova remnants and superbubble structures. Others may indicate regions where gas is cooling through the transition temperature.

Testing the Linearity of the Cosmic Origins Spectrograph FUV Channel Thermal Correction

NASA Astrophysics Data System (ADS)

Fix, Mees B.; De Rosa, Gisella; Sahnow, David

2018-05-01

The Far Ultraviolet Cross Delay Line (FUV XDL) detector on the Cosmic Origins Spectrograph (COS) is subject to temperature-dependent distortions. The correction performed by the COS calibration pipeline (CalCOS) assumes that these changes are linear across the detector. In this report we evaluate the accuracy of the linear approximations using data obtained on orbit. Our results show that the thermal distortions are consistent with our current linear model.

Rocket FUV Observations of the Io Plasma Torus During the Shoemaker-Levy/9 Impacts

NASA Technical Reports Server (NTRS)

Stern, S. A.; Slater, D.; Cash, W.; Wilkinson, E.; Green, J.; Gladstone, R.

1995-01-01

We observed the Io torus from 820-1140 A on universal time (UT) 20.25 July 1994 from a sounding rocket telescope/spectrograph. These observations serve as only the fourth published spectrum of the torus in this wavelength range, and the only far ultraviolet (FUV) data documenting the state of the torus during the Shoemaker Levy 9 Impacts.

Accretion and Diffusion in the DAZ White Dwarf GALEX J1931+0117

NASA Astrophysics Data System (ADS)

Vennes, Stéphane; Kawka, Adéla; Németh, Péter

2011-03-01

We present an analysis of high-dispersion and high signal-to-noise ratio spectra of the DAZ white dwarf GALEX J1931+0117. The spectra obtained with the VLT-Kueyen/UV-Visual Echelle Spectrograph show several well-resolved Si II spectral lines enabling a study of pressure effects on line profiles. We observed large Stark shifts in silicon lines in agreement with laboratory measurements. A model atmosphere analysis shows that the magnesium, silicon and iron abundances exceed solar abundances, while the oxygen and calcium abundances are below solar. Also, we compared the observed line profiles to synthetic spectra computed with variable accretion rates and vertical abundance distributions assuming diffusion steady-state. The inferred accretion rates vary from Ṁ = 2×106 for calcium to 2×109 g s-1 for oxygen and indicate that the accretion flow is dominated by oxygen, silicon and iron while being deficient in carbon, magnesium and calcium. The lack of radial velocity variations between two measurement epochs suggests that GALEX J1931+0117 is probably not in a close binary and that the source of the accreted material resides in a debris disc.

The Far-UV Wavelength Dependence of the Lunar Phase Curve as Seen by LRO LAMP

NASA Astrophysics Data System (ADS)

Liu, Y.; Retherford, K. D.; Greathouse, T. K.; Hendrix, A. R.; Cahill, J. T. S.; Mandt, K. E.; Gladstone, G. R.; Grava, C.; Egan, A. F.; Kaufmann, D. E.; Pryor, W. R.

2017-10-01

In this study we discuss the Far-UV wavelength dependence of the lunar phase curves for sample mare and highlands as seen by the LAMP instrument, and we report current derived Hapke parameters at Far-UV wavelengths for the study areas.

FUV Reflectance of Recently Prepared Al Protected with AlF3: COR Program Technology Development

NASA Technical Reports Server (NTRS)

Quijada, Manuel

2016-01-01

Astronomical observations in the Far Ultraviolet (FUV) spectral region are some of the more challenging due to the very distant and faint objects that are typically searched for in cosmic origin studies such as origin of large scale structure, the formation, evolution, and age of galaxies and the origin of stellar and planetary systems. These challenges are driving the need to improve the performance of optical coatings over a wide spectral range that would increase reflectance in mirrors and reduced absorption in dielectric filters used in optical telescope for FUV observations. This paper will present recent advances in reflectance performance for Al+AlF3 mirrors optimized for Lyman-alpha wavelength by performing the deposition of the AlF3 overcoat at elevated substrate temperatures.

Far Ultraviolet Imaging from the Image Spacecraft

NASA Technical Reports Server (NTRS)

Mende, S. B.; Heetderks, H.; Frey, H. U.; Lampton, M.; Geller, S. P.; Stock, J. M.; Abiad, R.; Siegmund, O. H. W.; Tremsin, A. S.; Habraken, S.

2000-01-01

Direct imaging of the magnetosphere by the IMAGE spacecraft will be supplemented by observation of the global aurora. The IMAGE satellite instrument complement includes three Far Ultraviolet (FUV) instruments. The Wideband Imaging Camera (WIC) will provide broad band ultraviolet images of the aurora for maximum spatial and temporal resolution by imaging the LBH N2 bands of the aurora. The Spectrographic Imager (SI), a novel form of monochromatic imager, will image the aurora, filtered by wavelength. The proton-induced component of the aurora will be imaged separately by measuring the Doppler-shifted Lyman-a. Finally, the GEO instrument will observe the distribution of the geocoronal emission to obtain the neutral background density source for charge exchange in the magnetosphere. The FUV instrument complement looks radially outward from the rotating IMAGE satellite and, therefore, it spends only a short time observing the aurora and the Earth during each spin. To maximize photon collection efficiency and use efficiently the short time available for exposures the FUV auroral imagers WIC and SI both have wide fields of view and take data continuously as the auroral region proceeds through the field of view. To minimize data volume, the set of multiple images are electronically co-added by suitably shifting each image to compensate for the spacecraft rotation. In order to minimize resolution loss, the images have to be distort ion-corrected in real time. The distortion correction is accomplished using high speed look up tables that are pre-generated by least square fitting to polynomial functions by the on-orbit processor. The instruments were calibrated individually while on stationary platforms, mostly in vacuum chambers. Extensive ground-based testing was performed with visible and near UV simulators mounted on a rotating platform to emulate their performance on a rotating spacecraft.

FAR-ULTRAVIOLET SPECTRAL IMAGES OF THE VELA SUPERNOVA REMNANT: SUPPLEMENTS AND COMPARISONS WITH OTHER WAVELENGTH IMAGES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kim, Il-Joong; Seon, Kwang-Il; Han, Wonyong

We present the improved far-ultraviolet (FUV) emission-line images of the entire Vela supernova remnant (SNR) using newly processed Spectroscopy of Plasma Evolution from Astrophysical Radiation/Far-Ultraviolet Imaging Spectrograph (SPEAR/FIMS) data. The incomplete C III {lambda}977 and O VI {lambda}{lambda}1032, 1038 images presented in the previous study are updated to cover the whole region. The C IV {lambda}{lambda}1548, 1551 image with a higher resolution and new images at Si IV {lambda}{lambda}1394, 1403, O IV] {lambda}1404, He II {lambda}1640.5, and O III] {lambda}{lambda}1661, 1666 are also shown. Comparison of emission-line ratios for two enhanced FUV regions reveals that the FUV emissions of themore » east-enhanced FUV region may be affected by nonradiative shocks of another very young SNR, the Vela Jr. SNR (RX J0852.0-4622, G266.6-1.2). This result is the first FUV detection that is likely associated with the Vela Jr. SNR, supporting previous arguments that the Vela Jr. SNR is close to us. The comparison of the improved FUV images with soft X-ray images shows that an FUV filamentary feature forms the boundary of the northeast-southwest asymmetrical sections of the X-ray shell. The southwest FUV features are characterized as the region where the Vela SNR is interacting with slightly denser ambient medium within the dim X-ray southwest section. From a comparison with the H{alpha} image, we identify a ring-like H{alpha} feature overlapped with an extended hot X-ray feature of similar size and two local peaks of C IV emission. Their morphologies are expected when the H{alpha} ring is in direct contact with the near or far side of the Vela SNR.« less

Dust-Corrected Star Formation Rates in Galaxies with Outer Rings

NASA Astrophysics Data System (ADS)

Kostiuk, I.; Silchenko, O.

2018-03-01

The star formation rates SFR, as well as the SFR surface densities ΣSFR and absolute stellar magnitudes MAB, are determined and corrected for interinsic dust absorption for 34 disk galaxies of early morphological types with an outer ring structure and ultraviolet emission from the ring. These characteristic are determined for the outer ring structures and for the galaxies as a whole. Data from the space telescopes GALEX (in the NUV and FUV ultraviolet ranges) and WISE (in the W4 22 μm infrared band) are used. The average relative deviation in the corrected SFR and ΣSFR derived from the NUV and FUV bands is only 19.0%, so their averaged values are used for statistical consideration. The relations between the dust-corrected SFR characteristics, UV colours, the galaxy morphological type, absolute magnitude are illustrated.

Evolution of the FUV Surface Properties of 67P/Churyumov-Gerasimenko through its 2015 Perihelion Passage

NASA Astrophysics Data System (ADS)

Feaga, Lori M.; Holt, Carrie E.; Steffl, Andrew; A'Hearn, Michael F.; Bertaux, Jean-Loup; Feldman, Paul D.; Noonan, John; Parker, Joel Wm; Schindhelm, Eric; Stern, S. Alan; Weaver, Harold A.

2016-10-01

Alice, NASA's lightweight and low-power far-ultraviolet (FUV) imaging spectrograph onboard ESA's comet orbiting spacecraft Rosetta (Stern et al. 2007, Space Sci. Rev. 128, 507), has just completed its characterization of the nucleus and coma of the Jupiter family comet 67P/Churyumov-Gerasimenko (C-G). With a spectral range from 700-2050 Å, Alice was able to monitor the sunlit surface of C-G in order to establish if there was variability in the FUV reflectivity across the nucleus, determine if there were distinct spectral features associated with various morphological regions, and infer compositional makeup of the comet. Using spatially resolved pre-perihelion data, the FUV phase dependence, albedo, and spectral slope were derived for the nucleus (Feaga et al. 2015, A&A 583, A27) and were consistent with a homogeneous layer of dust covering the northern hemisphere. During the increase in activity around perihelion and change of seasons on the comet, the Rosetta suite of instruments has shown evidence of surface changes, mass movement of material, and transient patches of ice. The FUV properties of the nucleus throughout the perihelion passage inside of 3 AU, including observations during a zero phase flyby and its associated opposition surge and a search for exposed water ice on the surface, will be presented here and compared to the early pre-perihelion characteristics.

Spectroscopic limits to an extragalactic far-ultraviolet background.

PubMed

Martin, C; Hurwitz, M; Bowyer, S

1991-10-01

We use a spectrum of the lowest intensity diffuse far-ultraviolet background obtained from a series of observations in a number of celestial view directions to constrain the properties of the extragalactic FUV background. The mean continuum level, IEG = 280 +/- 35 photons cm-2 s-1 angstrom-1 sr-1, was obtained in a direction with very low H I column density, and this represents a firm upper limit to any extragalactic background in the 1400-1900 angstroms band. Previous work has demonstrated that the far-ultraviolet background includes (depending on a view direction) contributions from dust-scattered Galactic light, high-ionization emission lines, two-photon emission from H II, H2 fluorescence, and the integrated light of spiral galaxies. We find no evidence in the spectrum of line or continuum features that would signify additional extragalactic components. Motivated by the observation of steep BJ and U number count distributions, we have made a detailed comparison of galaxy evolution models to optical and UV data. We find that the observations are difficult to reconcile with a dominant contribution from unclustered, starburst galaxies at low redshifts. Our measurement rules out large ionizing fluxes at z = 0, but cannot strongly constrain the QSO background light, which is expected to be 0.5%-4% of IEG. We present improved limits on radiative lifetimes of massive neutrinos. We demonstrated with a simple model that IGM radiation is unlikely to make a significant contribution to IEG. Since dust scattering could produce a significant part of the continuum in this lowest intensity spectrum, we carried out a series of tests to evaluate this possibility. We find that the spectrum of a nearby target with higher NH I, when corrected for H2 fluorescence, is very similar to the spectrum obtained in the low H I view direction. This is evidence that the majority of the continuum observed at low NH I is also dust reflection, indicating either the existence of a hitherto

The Hubble Deep UV Legacy Survey (HDUV)

NASA Astrophysics Data System (ADS)

Montes, Mireia; Oesch, Pascal

2015-08-01

Deep HST imaging has shown that the overall star formation density and UV light density at z>3 is dominated by faint, blue galaxies. Remarkably, very little is known about the equivalent galaxy population at lower redshifts. Understanding how these galaxies evolve across the epoch of peak cosmic star-formation is key to a complete picture of galaxy evolution. Here, we present a new HST WFC3/UVIS program, the Hubble Deep UV (HDUV) legacy survey. The HDUV is a 132 orbit program to obtain deep imaging in two filters (F275W and F336W) over the two CANDELS Deep fields. We will cover ~100 arcmin2 sampling the rest-frame far-UV at z>~0.5, this will provide a unique legacy dataset with exquisite HST multi-wavelength imaging as well as ancillary HST grism NIR spectroscopy for a detailed study of faint, star-forming galaxies at z~0.5-2. The HDUV will enable a wealth of research by the community, which includes tracing the evolution of the FUV luminosity function over the peak of the star formation rate density from z~3 down to z~0.5, measuring the physical properties of sub-L* galaxies, and characterizing resolved stellar populations to decipher the build-up of the Hubble sequence from sub-galactic clumps. This poster provides an overview of the HDUV survey and presents the reduced data products and catalogs which will be released to the community, reaching down to 27.5-28.0 mag at 5 sigma. By directly sampling the rest-frame far-UV at z>~0.5, this will provide a unique legacy dataset with exquisite HST multi-wavelength imaging as well as ancillary HST grism NIR spectroscopy for a detailed study of faint, star-forming galaxies at z~0.5-2. The HDUV will enable a wealth of research by the community, which includes tracing the evolution of the FUV luminosity function over the peak of the star formation rate density from z~3 down to z~0.5, measuring the physical properties of sub-L* galaxies, and characterizing resolved stellar populations to decipher the build-up of the Hubble

Measurement of precipitation induced FUV emission and Geocoronal Lyman Alpha from the IMI mission

NASA Technical Reports Server (NTRS)

Mende, Stephen B.; Fuselier, S. A.; Rairden, R. L.

1995-01-01

This final report describes the activities of the Lockheed Martin Palo Alto Research Laboratory in studying the measurement of ion and electron precipitation induced Far Ultra-Violet (FUV) emissions and Geocoronal Lyman Alpha for the NASA Inner Magnetospheric Imager (IMI) mission. this study examined promising techniques that may allow combining several FUV instruments that would separately measure proton aurora, electron aurora, and geocoronal Lyman alpha into a single instrument operated on a spinning spacecraft. The study consisted of two parts. First, the geocoronal Lyman alpha, proton aurora, and electron aurora emissions were modeled to determine instrument requirements. Second, several promising techniques were investigated to determine if they were suitable for use in an IMI-type mission. Among the techniques investigated were the Hydrogen gas cell for eliminating cold geocoronal Lyman alpha emissions, and a coded aperture spectrometer with sufficient resolution to separate Doppler shifted Lyman alpha components.

The Effects of FUV Radiation on C-Shocks: Implications for Water and Other O-bearing Species

NASA Astrophysics Data System (ADS)

Kaufman, Michael; Melick, Gary; Tolls, Volker

2015-08-01

Protostellar outflows have long been known to drive endothermic reactions that produce high abundances of oxygen-bearing species. Models of shocks in well-shielded gas made the strong prediction that essentially all of the pre-shock oxygen gets driven into water, so that the post-shock water abundances are order 10-4. Herschel observations, however, including those from the key program “Water in Star Forming Regions with Herschel (WISH)” show that for most sources, the shocked gas water abundances of are far lower, 10-7 - 10-5.This pattern of lower-than-predicted water abundance has led us to consider that our C-shock model (Kaufman & Neufeld 1996) is incomplete. In particular, we did not previously take into account that many outflow sources have higher than average far-ultraviolet radiation fields within their outflow cavities. Strong FUV radiation has important effects on the structure of C-shocks: the ionization fraction is larger than in well-shielded gas, decreasing the coupling length between neutrals and ions, and leading to higher temperatures and a lower breakdown speeds; the pre-shock gas composition, including the presence of ice mantles and the dominant charge carriers, is strongly affected; and abundant species such as water are diminished by photodissociation in the cooled down stream gas.In addition to the normal parameters of density, shock velocity, and magnetic field strength, we now include the external FUV field strength and the extinction between the FUV source and the shock. We use the results of a detailed PDR model to compute pre-shock chemical conditions, including the ionization fraction, the increase of which decreases the maximum velocities of C- shocks. FUV also keeps oxygen in the gas phase, making more available for H2O formarion ; however, photodissociation beyond the temperature peak keeps the average H2O abundance down. We present comparisons of our model results with the inferred water abundances and with observations of H2O

Conversion of far ultraviolet to visible radiation: absolute measurements of the conversion efficiency of tetraphenyl butadiene

NASA Astrophysics Data System (ADS)

Vest, Robert E.; Coplan, Michael A.; Clark, Charles W.

Far ultraviolet (FUV) scintillation of noble gases is used in dark matter and neutrino research and in neutron detection. Upon collisional excitation, noble gas atoms recombine into excimer molecules that decay by FUV emission. Direct detection of FUV is difficult. Another approach is to convert it to visible light using a wavelength-shifting medium. One such medium, tetraphenyl butadiene (TPB) can be vapor-deposited on substrates. Thus the quality of thin TPB films can be tightly controlled. We have measured the absolute efficiency of FUV-to-visible conversion by 1 μm-thick TPB films vs. FUV wavelengths between 130 and 300 nm, with 1 nm resolution. The energy efficiency of FUV to visible conversion varies between 1% and 5%. We make comparisons with other recent results. Work performed at the NIST SURF III Synchrotron Ultraviolet Radiation Facility,.

The Local Universe as Seen in the Far-Infrared and Far-Ultraviolet: A Global Point of View of the Local Recent Star Formation

NASA Astrophysics Data System (ADS)

Buat, V.; Takeuchi, T. T.; Iglesias-Páramo, J.; Xu, C. K.; Burgarella, D.; Boselli, A.; Barlow, T.; Bianchi, L.; Donas, J.; Forster, K.; Friedman, P. G.; Heckman, T. M.; Lee, Y.-W.; Madore, B. F.; Martin, D. C.; Milliard, B.; Morissey, P.; Neff, S.; Rich, M.; Schiminovich, D.; Seibert, M.; Small, T.; Szalay, A. S.; Welsh, B.; Wyder, T.; Yi, S. K.

2007-12-01

We select far-infrared (FIR: 60 μm) and far-ultraviolet (FUV: 530 Å) samples of nearby galaxies in order to discuss the biases encountered by monochromatic surveys (FIR or FUV). Very different volumes are sampled by each selection, and much care is taken to apply volume corrections to all the analyses. The distributions of the bolometric luminosity of young stars are compared for both samples: they are found to be consistent with each other for galaxies of intermediate luminosities, but some differences are found for high (>5×1010 Lsolar) luminosities. The shallowness of the IRAS survey prevents us from securing a comparison at low luminosities (<2×109 Lsolar). The ratio of the total infrared (TIR) luminosity to the FUV luminosity is found to increase with the bolometric luminosity in a similar way for both samples up to 5×1010 Lsolar. Brighter galaxies are found to have a different behavior according to their selection: the LTIR/LFUV ratio of the FUV-selected galaxies brighter than 5×1010 Lsolar reaches a plateau, whereas LTIR/LFUV continues to increase with the luminosity of bright galaxies selected in FIR. The volume-averaged specific star formation rate (SFR per unit galaxy stellar mass, SSFR) is found to decrease toward massive galaxies within each selection. The mean values of the SSFR are found to be larger than those measured for optical and NIR-selected samples over the whole mass range for the FIR selection, and for masses larger than 1010 Msolar for the FUV selection. Luminous and massive galaxies selected in FIR appear as active as galaxies with similar characteristics detected at z~0.7.

GALEX 1st Light Far Ultraviolet

NASA Technical Reports Server (NTRS)

2003-01-01

This image was taken May 21 and 22 by NASA's Galaxy Evolution Explorer. The image was made from data gathered by the far ultraviolet channel of the spacecraft camera during the mission's 'first light' milestone. It shows about 400 celestial objects, appearing in blue, detected over a 3-minute, 20-second period in the constellation Hercules.

The Galaxy Evolution Explorer's first light images are dedicated to the crew of the Space Shuttle Columbia. The Hercules region was directly above Columbia when it made its last contact with NASA Mission Control on February 1, over the skies of Texas.

The Galaxy Evolution Explorer launched on April 28 on a mission to map the celestial sky in the ultraviolet and determine the history of star formation in the universe over the last 10 billion years.

Mapping the Spatial Distribution of Dust Extinction in NGC 959 Using Broadband Visible and Mid-Infrared Filters

NASA Astrophysics Data System (ADS)

Tamura, K.; Jansen, R. A.; Windhorst, R. A.

2009-12-01

We present a method to estimate and map the two-dimensional distribution of dust extinction in the late-type spiral galaxy NGC 959 from the theoretical and observed flux ratio of optical V and mid-IR (MIR) 3.6 μm images. Our method is applicable to both young and old stellar populations for a range of metallicities, and is not restricted to lines of sight toward star-formation (SF) regions. We explore this method using a pixel-based analysis on images of NGC 959 obtained in the V band at the Vatican Advanced Technology Telescope and at 3.6 μm (L band) with Spitzer/Infrared Array Camera. We present the original and extinction corrected Galaxy Evolution Explorer (GALEX) far-UV (FUV) and near-UV (NUV) images, as well as optical UBVR images of NGC 959. While the dust lanes are not clearly evident at GALEX resolution, our dust map clearly traces the dust that can be seen silhouetted against the galaxy's disk in the high-resolution Hubble Space Telescope (HST) images of NGC 959. The advantages of our method are (1) it only depends on two relatively common broadband images in the optical V band and in the MIR at 3.6 μm (but adding a near-UV band improves its fidelity); and (2) it is able to map the two-dimensional spatial distribution of dust within a galaxy. This powerful tool could be used to measure the detailed distribution of dust extinction within higher redshift galaxies to be observed with, e.g., the Hubble Space Telescope (HST)/WFC3 (optical near-IR) and James Webb Space Telescope (mid-IR), and to distinguish properties of dust within galaxy bulges, spiral arms, and inter-arm regions.

LRO Lyman Alpha Mapping Project (LAMP) Far-UV Investigations of Lunar Composition, Porosity, and Space Weathering

NASA Astrophysics Data System (ADS)

Retherford, K. D.; Greathouse, T. K.; Mandt, K. E.; Gladstone, R.; Hendrix, A.; Cahill, J. T.; Liu, Y.; Grava, C.; Hurley, D.; Egan, A.; Kaufmann, D. E.; Raut, U.; Byron, B. D.; Magana, L. O.; Stickle, A. M.; Wyrick, D. Y.; Pryor, W. R.

2017-12-01

Far ultraviolet reflectance measurements of the Moon, icy satellites, comets, and asteroids have proven surprisingly useful for advancing our understanding of planetary surfaces. This new appreciation for planetary far-UV imaging spectroscopy is provided in large part thanks to nearly a decade of investigations with the Lunar Reconnaissance Orbiter (LRO) Lyman Alpha Mapping Project (LAMP). LAMP has demonstrated an innovative nightside observing technique, putting a new light on permanently shadowed regions (PSRs) and other features on the Moon. Dayside far-UV albedo maps complement the nightside data, enabling comparisons of direct and hemispheric (diffuse) illumination derived albedos. We'll discuss the strengths of the far-UV reflectance imaging spectroscopy technique with respect to several new LAMP results. Detections of water frost and hydration signatures near 165 nm, for example, provide constraints on composition that complement infrared spectroscopy, visible imaging, neutron spectroscopy, radar, and other techniques. LRO's polar orbit and high data downlink capabilities enable searches for diurnal variations in spectral signals. At far-UV wavelengths a relatively blue spectral slope is diagnostic of space weathering, which is opposite of the spectral reddening indicator of maturity at wavelengths longward of 180 nm. By utilizing natural diffuse illumination sources on the nightside the far-UV technique is able to identify relative increases in porosity within the PSRs, and provides an additional tool for determining relative surface ages. On October 6, 2016 LAMP enacted a new, more sensitive dayside operating mode that expands its ability to search for diurnally varying hydration signals associated with different regions and features.

The UV and X-ray activity of the M dwarfs within 10 pc of the Sun

NASA Astrophysics Data System (ADS)

Stelzer, B.; Marino, A.; Micela, G.; López-Santiago, J.; Liefke, C.

2013-05-01

M dwarfs are the most numerous stars in the Galaxy. They are characterized by strong magnetic activity. The ensuing high-energy emission is crucial for the evolution of their planets and the eventual presence of life on them. We systematically study the X-ray and ultraviolet emission of a subsample of M dwarfs from a recent proper-motion survey, selecting all M dwarfs within 10 pc to obtain a nearly volume-limited sample (˜90 per cent completeness). Archival ROSAT, XMM-Newton and GALEX data are combined with published spectroscopic studies of Hα emission and rotation to obtain a broad picture of stellar activity on M dwarfs. We make use of synthetic model spectra to determine the relative contributions of photospheric and chromospheric emission to the ultraviolet flux. We also analyse the same diagnostics for a comparison sample of young M dwarfs in the TW Hya association (˜10 Myr). We find that generally the emission in the GALEX bands is dominated by the chromosphere but the photospheric component is not negligible in early-M field dwarfs. The surface fluxes for the Hα, near-ultraviolet, far-ultraviolet and X-ray emission are connected via a power-law dependence. We present here for the first time such flux-flux relations involving broad-band ultraviolet emission for M dwarfs. Activity indices are defined as flux ratio between the activity diagnostic and the bolometric flux of the star in analogy to the Ca IIR'HK index. For given spectral type, these indices display a spread of 2-3 dex which is largest for M4 stars. Strikingly, at mid-M spectral types, the spread of rotation rates is also at its highest level. The mean activity index for fast rotators, likely representing the saturation level, decreases from X-rays over the FUV to the NUV band and Hα, i.e. the fractional radiation output increases with atmospheric height. The comparison to the ultraviolet and X-ray properties of TW Hya members shows a drop of nearly three orders of magnitude for the

Investigating the FUV Emission of Young M dwarfs with FUMES: the Far Ultraviolet M-dwarf Evolution Survey

NASA Astrophysics Data System (ADS)

Pineda, John

2016-10-01

M dwarf stars have become attractive candidates for exoplanet searches and will be a main focus of the upcoming TESS mission, with the continued search for nearby potentially habitable worlds. However, the atmospheric characterization of these exoplanetary systems depends critically on the high energy stellar radiation environment from X-ray to NUV. Strong radiation at these energies can lead to atmospheric mass loss and is a strong driver of photochemistry in planetary atmospheres. Recently, the MUSCLES Treasury Survey (Cycles 19, 22) provided the first comprehensive assessment of the high energy radiation field around old, planet hosting M dwarfs. However, the habitability and potential for such exoplanetary atmospheres to develop life also depends on the evolution of the atmosphere and hence the evolution of the incident radiation field. The strong high energy spectrum of young M dwarfs can have devastating consequences for the potential habitability of a given system. We, thus, propose the Far Ultraviolet M-dwarf Evolution Survey (FUMES) to measure the strong FUV coronal/chromospheric emission features of young M dwarfs (12 - 650 Myr), e.g. He II, C IV, and S IV. FUMES will observe objects with a wide range of rotation rates to directly connect the emission features to the evolution of coronal heating and upper atmospheric structure, and provide observational benchmarks at young ages for models of M dwarf upper atmospheres. Building on results from MUSCLES, we will be able to estimate the whole high energy radiation field and establish the evolutionary picture of the incident radiation throughout the lifetime of exoplanetary systems around early-mid M dwarf hosts.

Colors of Ellipticals from GALEX to Spitzer

NASA Astrophysics Data System (ADS)

Schombert, James M.

2016-12-01

Multi-color photometry is presented for a large sample of local ellipticals selected by morphology and isolation. The sample uses data from the Galaxy Evolution Explorer (GALEX), Sloan Digital Sky Survey (SDSS), Two Micron All-Sky Survey (2MASS), and Spitzer to cover the filters NUV, ugri, JHK and 3.6 μm. Various two-color diagrams, using the half-light aperture defined in the 2MASS J filter, are very coherent from color to color, meaning that galaxies defined to be red in one color are always red in other colors. Comparison to globular cluster colors demonstrates that ellipticals are not composed of a single age, single metallicity (e.g., [Fe/H]) stellar population, but require a multi-metallicity model using a chemical enrichment scenario. Such a model is sufficient to explain two-color diagrams and the color-magnitude relations for all colors using only metallicity as a variable on a solely 12 Gyr stellar population with no evidence of stars younger than 10 Gyr. The [Fe/H] values that match galaxy colors range from -0.5 to +0.4, much higher (and older) than population characteristics deduced from Lick/IDS line-strength system studies, indicating an inconsistency between galaxy colors and line indices values for reasons unknown. The NUV colors have unusual behavior, signaling the rise and fall of the UV upturn with elliptical luminosity. Models with blue horizontal branch tracks can reproduce this behavior, indicating the UV upturn is strictly a metallicity effect.

Overview of GX launch services by GALEX

NASA Astrophysics Data System (ADS)

Sato, Koji; Kondou, Yoshirou

2006-07-01

Galaxy Express Corporation (GALEX) is a launch service company in Japan to develop a medium size rocket, GX rocket and to provide commercial launch services for medium/small low Earth orbit (LEO) and Sun synchronous orbit (SSO) payloads with a future potential for small geo-stationary transfer orbit (GTO). It is GALEX's view that small/medium LEO/SSO payloads compose of medium scaled but stable launch market due to the nature of the missions. GX rocket is a two-stage rocket of well flight proven liquid oxygen (LOX)/kerosene booster and LOX/liquid natural gas (LNG) upper stage. This LOX/LNG propulsion under development by Japan's Aerospace Exploration Agency (JAXA), is robust with comparable performance as other propulsions and have future potential for wider application such as exploration programs. GX rocket is being developed through a joint work between the industries and GX rocket is applying a business oriented approach in order to realize competitive launch services for which well flight proven hardware and necessary new technology are to be introduced as much as possible. It is GALEX's goal to offer “Easy Access to Space”, a highly reliable and user-friendly launch services with a competitive price. GX commercial launch will start in Japanese fiscal year (JFY) 2007 2008.

Far-UV Spectral Mapping of Lunar Composition, Porosity, and Space Weathering: LRO Lyman Alpha Mapping Project (LAMP)

NASA Astrophysics Data System (ADS)

Retherford, K. D.; Greathouse, T. K.; Mandt, K.; Gladstone, R.; Liu, Y.; Hendrix, A. R.; Hurley, D.; Cahill, J. T.; Stickle, A. M.; Egan, A.; Kaufmann, D. E.; Grava, C.; Pryor, W. R.

2016-12-01

Far ultraviolet reflectance measurements of the Moon, icy satellites, comets, and asteroids obtained within the last decade have ushered in a new era of scientific advancement for UV surface investigations. The Lunar Reconnaissance Orbiter (LRO) Lyman Alpha Mapping Project (LAMP) has demonstrated an innovative nightside observing technique, putting a new light on permanently shadowed regions (PSRs) and other features on the Moon. Dayside far-UV albedo maps complement the nightside data, and LRO's polar orbit and high data downlink capabilities enable searches for diurnal variations in spectral signals. We'll discuss the strengths of the far-UV reflectance imaging spectroscopy technique with respect to several new LAMP results. Detections of water frost and hydration signatures near 165 nm, for example, provide constraints on composition that complement infrared spectroscopy, visible imaging, neutron spectroscopy, radar, and other techniques. At far-UV wavelengths a relatively blue spectral slope is diagnostic of space weathering, which is opposite of the spectral reddening indicator of maturity at wavelengths longward of 180 nm. By utilizing natural diffuse illumination sources on the nightside the far-UV technique is able to identify relative increases in porosity within the PSRs, and provides an additional tool for determining relative surface ages. Prospects for future studies are further enabled by a new, more sensitive dayside operating mode enacted during the present LRO mission extension.

Hot Subdwarf Stars Among the Objects Rejected from the PG Catalog: a First Assessment Using GALEX Photometry

NASA Technical Reports Server (NTRS)

Wade, Richard A.; Stark, M. A.; Green, Richard F.; Durrell, Patrick R.

2009-01-01

The hot subdwarf (sd) stars in the Palomar Green (PG) catalog of ultraviolet excess (UVX) objects play a key role in investigations of the frequency and types of binary companions and the distribution of orbital periods. These are important for establishing whether and by which channels the sd stars arise from interactions in close binary systems. It has been suggested that the list of PG sd stars is biased by the exclusion of many stars in binaries, whose spectra show the Ca I1 K line in absorption. A total of 1125 objects that were photometrically selected as candidates were ultimately rejected from the final PG catalog using this K-line criterion. We study 88 of these 'PG-Rejects' (PGRs), to assess whether there are significant numbers of unrecognized sd stars in binaries among the PGR objects. The presence of a sd should cause a large UVX, compared with the cool K-line star. We assemble GALEX, Johnson V, and 2MASS photometry and compare the colors of these PGR objects with those of known sd stars, cool single stars, and hot+cool binaries. Sixteen PGRs were detected in both the far- and near-ultraviolet GALEX passbands. Eleven of these, plus the 72 cases with only an upper limit in the far-ultraviolet band, are interpreted as single cool stars, appropriately rejected by the PG spectroscopy. Of the remaining five stars, three are consistent with being sd stars paired with a cool main sequence companion, while two may be single stars or composite systems of another type. We discuss the implications of these findings for the 1125 PGR objects as a whole. An enlarged study is desirable to increase confidence in these first results and to identify individual sd+cool binaries or other composites for follow-up study. The GALEX AIS data have sufficient sensitivity to carry out this larger study.

High-Resolution Large Field-of-View FUV Compact Camera

NASA Technical Reports Server (NTRS)

Spann, James F.

2006-01-01

The need for a high resolution camera with a large field of view and capable to image dim emissions in the far-ultraviolet is driven by the widely varying intensities of FUV emissions and spatial/temporal scales of phenomena of interest in the Earth% ionosphere. In this paper, the concept of a camera is presented that is designed to achieve these goals in a lightweight package with sufficient visible light rejection to be useful for dayside and nightside emissions. The camera employs the concept of self-filtering to achieve good spectral resolution tuned to specific wavelengths. The large field of view is sufficient to image the Earth's disk at Geosynchronous altitudes and capable of a spatial resolution of >20 km. The optics and filters are emphasized.

The climatology of low-latitude ionospheric densities and zonal drifts from IMAGE-FUV.

NASA Astrophysics Data System (ADS)

Immel, T. J.; Sagawa, E.; Frey, H. U.; Mende, S. B.; Patel, J.

2004-12-01

The IMAGE satellite was the first dedicated to magnetospheric imaging, but has also provided numerous images of the nightside ionosphere with its Far-Ultraviolet (FUV) spectrographic imager. Nightside emissions of O I at 135.6-nm originating away from the aurora are due to recombination of ionospheric O+, and vary in intensity with (O+)2. IMAGE-FUV, operating in a highly elliptical orbit with apogee at middle latitudes and >7 Re altitude, measures this emission globally with 100-km resolution. During each 14.5 hour orbit, IMAGE-FUV is able to monitor nightside ionospheric densities for up to 6-7 hours. Hundreds of low-latitude ionospheric bubbles, their development and drift speed, and a variety of other dynamical variations in brightness and morphology of the equatorial anomalies have been observed during this mission. Furthermore, the average global distribution of low-latitude ionospheric plasma densities can be determined in 3 days. Imaging data collected from February through June of 2002 are used to compile a dataset containing a variety of parameters (e.g., latitude and brightness of peak plasma density, zonal bubble drift speed) which can be drawn from for climatological studies. Recent results indicate that the average ground speed of low-latitude zonal plasma drifts vary with longitude by up to 50%, and that a periodic variation in ionospheric densities with longitude suggests the influence of a lower-thermospheric non-migrating tide with wave number = 4 on ionospheric densities. An excellent correlation between zonal drift speed and the magnetic storm index Dst is also found.

Far-Ultraviolet Spectroscopy of Three Long-Period Novalike Variables

NASA Astrophysics Data System (ADS)

Bisol, Alexandra C.; Godon, Patrick; Sion, Edward M.

2012-02-01

We have selected three novalike variables at the long-period extreme of novalike orbital periods: V363 Aur, RZ Gru, and AC Cnc, all with IUE archival far-ultraviolet spectra. All are UX UMa-type novalike variables and all have Porb > 7 hr. V363 Aur is a bona fide SW Sex star, and AC Cnc is a probable one, while RZ Gru has not proven to be a member of the SW Sex subclass. We have carried out the first synthetic spectral analysis of far-ultraviolet spectra of the three systems using state-of-the-art models of both accretion disks and white dwarf photospheres. We find that the FUV spectral energy distribution of both V363 Aur and RZ Gru are in agreement with optically thick steady-state accretion disk models in which the luminous disk accounts for 100% of the FUV light. We present accretion rates and model-derived distances for V363 Aur and RZ Gru. For AC Cnc, we find that a hot accreting white dwarf accounts for ˜60% of the FUV light, with an accretion disk providing the rest. We compare our accretion rates and model-derived distances with estimates in the literature.

COLORS OF ELLIPTICALS FROM GALEX TO SPITZER

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schombert, James M., E-mail: jschombe@uoregon.edu

2016-12-01

Multi-color photometry is presented for a large sample of local ellipticals selected by morphology and isolation. The sample uses data from the Galaxy Evolution Explorer ( GALEX ), Sloan Digital Sky Survey (SDSS), Two Micron All-Sky Survey (2MASS), and Spitzer to cover the filters NUV , ugri , JHK and 3.6 μ m. Various two-color diagrams, using the half-light aperture defined in the 2MASS J filter, are very coherent from color to color, meaning that galaxies defined to be red in one color are always red in other colors. Comparison to globular cluster colors demonstrates that ellipticals are not composedmore » of a single age, single metallicity (e.g., [Fe/H]) stellar population, but require a multi-metallicity model using a chemical enrichment scenario. Such a model is sufficient to explain two-color diagrams and the color–magnitude relations for all colors using only metallicity as a variable on a solely 12 Gyr stellar population with no evidence of stars younger than 10 Gyr. The [Fe/H] values that match galaxy colors range from −0.5 to +0.4, much higher (and older) than population characteristics deduced from Lick/IDS line-strength system studies, indicating an inconsistency between galaxy colors and line indices values for reasons unknown. The NUV colors have unusual behavior, signaling the rise and fall of the UV upturn with elliptical luminosity. Models with blue horizontal branch tracks can reproduce this behavior, indicating the UV upturn is strictly a metallicity effect.« less

Far-Ultraviolet Number Counts of Field Galaxies

NASA Technical Reports Server (NTRS)

Voyer, Elysse N.; Gardner, Jonathan P.; Teplitz, Harry I.; Siana, Brian D.; deMello, Duilia F.

2010-01-01

The Number counts of far-ultraviolet (FUV) galaxies as a function of magnitude provide a direct statistical measure of the density and evolution of star-forming galaxies. We report on the results of measurements of the rest-frame FUV number counts computed from data of several fields including the Hubble Ultra Deep Field, the Hubble Deep Field North, and the GOODS-North and -South fields. These data were obtained from the Hubble Space Telescope Solar Blind Channel of the Advance Camera for Surveys. The number counts cover an AB magnitude range from 20-29 magnitudes, covering a total area of 15.9 arcmin'. We show that the number counts are lower than those in previous studies using smaller areas. The differences in the counts are likely the result of cosmic variance; our new data cover more area and more lines of sight than the previous studies. The slope of our number counts connects well with local FUV counts and they show good agreement with recent semi-analytical models based on dark matter "merger trees".

Advances in far-ultraviolet reflective and transmissive coatings for space applications

NASA Astrophysics Data System (ADS)

Rodríguez-de Marcos, Luis; Aznárez, José A.; Méndez, José A.; Larruquert, Juan I.; Vidal-Dasilva, M.; Malvezzi, A. Marco; Giglia, Angelo; Capobianco, Gerardo; Massone, Giuseppe; Fineschi, Silvano; Nannarone, Stefano

2016-07-01

Exploitation of far ultraviolet (FUV, 100-200 nm) observations extends to most areas of modern astronomy, from detailed observations of Solar System objects, the interstellar medium, exoplanets, stars and galaxies, to studies of crucial cosmological relevance. Despite several developments in recent decades, yet many observations are not possible due to technical limitations, of which one of the most important is the lack of optical coatings with high throughput. Development and optimization of such efficient FUV coatings have been identified in several roadmap reports as a key goal for future missions. The success of this development will ultimately improve the performance of nowadays feasible optical instruments and will enable new scientific imaging capabilities. GOLD's research is devoted to developing novel coatings with enhanced performance for space optics. Several deposition systems are available for the deposition of multilayer coatings. A deposition system was developed to deposit FUV coatings to satisfy space requirements. It consists of a 75-cm-diameter deposition chamber pumped with a cryo-pump and placed in an ISO-6 clean room. This chamber is available for deposition by evaporation of top-requirement coatings such as Al/ MgF2 mirrors or (Al/MgF2)n multilayer coatings for transmittance filters. A plan to add an Ion-Beam-Sputtering system in this chamber is under way. In this and other chambers at GOLD the following FUV coatings can be prepared: Transmittance filters based on (Al/MgF2)n multilayer coatings. These filters can be designed to have a peak at the FUV spectral line or band of interest and a high peak-to-visible transmittance ratio. Filters can be designed with a peak transmittance at a wavelength as short as 120 nm and with a transmittance in the visible smaller than 10-5. Narrowband reflective coatings peaked close to H Lyman β (102.6 nm) with a reflectance at H Lyman α (121.6 nm) two orders of magnitude below the one at 102.6 nm. Other

VizieR Online Data Catalog: [U]LIRGs - on the trail of AGN's types (Malek+, 2017)

NASA Astrophysics Data System (ADS)

Malek, K.; Bankowicz, M.; Pollo, A.; Takeuchi, T. T.; Buat, V.; Burgarella, D.; Goto, T.; Malkan, M.

2016-11-01

Identifications and photometric flux densities in all available wavelengths for 39 [U]LIRGs found in the ADF-S survey. All 39 sources for which a counterpart in the 40" radius on the sky has been found in the public databases are listed. The serial ADF-S number, ADF-S coordinates, redshift and fluxes (in four far-infrared (FIR) AKARI bands (65, 90, 140 and 160um), as well as photometric fluxes densities and uncertainties for 16 more bands spanning spectra from FUV (GALEX) to FIR (Herschel/SPIRE) are given for each source. Flux value set to "---" represents unknown value. (1 data file).

FAR-ULTRAVIOLET OBSERVATION OF THE AQUILA RIFT WITH FIMS/SPEAR

DOE Office of Scientific and Technical Information (OSTI.GOV)

Park, S.-J.; Min, K.-W.; Seon, K.-I.

2012-07-20

We present the results of far ultraviolet (FUV) observations of the broad region around the Aquila Rift including the Galactic plane. As compared with various wavelength data sets, dust scattering is found to be the major origin of the diffuse FUV continuum in this region. The FUV intensity clearly correlates with the dust extinction level for E(B - V) < 0.2, while this correlation disappears for E(B - V) > 0.2 due to heavy dust extinction combined with the effect of nonuniform interstellar radiation fields. The FUV intensity also correlates well with H{alpha} intensity, implying that at least some fractionmore » of the observed H{alpha} emission could be the dust-scattered light of H{alpha} photons originating elsewhere in the Galaxy. Most of the Aquila Rift region is seen devoid of diffuse FUV continuum due to heavy extinction while strong emission is observed in the surrounding regions. Molecular hydrogen fluorescent emission lines are clearly seen in the spectrum of 'Aquila-Serpens', while 'Aquila-East' does not show any apparent line features. CO emission intensity is also found to be higher in the 'Aquila-Serpens' region than in the 'Aquila-East' region. In this regard, we note that regions of star formation have been found in 'Aquila-Serpens' but not in 'Aquila-East'.« less

COS FUV Target Acquisition Monitor

NASA Astrophysics Data System (ADS)

Penton, Steven V.

2017-08-01

Starting in Cycle 25, the COS Target Acquisition (TA) monitor has been divided into two pieces, NUV (15389) and FUV (15386). This program is the FUV portion and is designed specifically for FUV LP4. FUV LP4 uses NUM_POS > 1 PEAKXDs for cross-dispersion TA. All previous LPs used NUM_POS=1 PEAKXDs. The NUM_POS=1 PEAKXDs required the routine monitoring of the grating-dependent WCA-to-PSA offsets. The NUM_POS >1 PEAKXDs do not use these flight software (FSW) patchable constants as they use the LTAPKD FSW macro used in ACQ/PEAKD, but re-purposed for use in the cross-dispersion (XD).This program uses the HST standard star WD1657+343. This target was used previously in the COS TA Monitor programs, 13124 (C20), 13526 (C21), 13972 (C22), 14440 (C23) & 14857 (C24). In these programs, this target was used to co-align the PSA/MIRRORB and BOA/MIRRORA ACQ/IMAGE modes. We re-use this target here as it is safe with PSA/MIRRORA and visible almost year-round.Note that when presented to the mission office, the target 206W3 was listed as the target for this program. This target was a backup target in previous TA monitor programs and was the faintest of the 3 targets in the program. Switching to the next brighter target (WD1657+343) allows all the goals of this program to be accomplished in just 2 orbits. Also, as this target has been used for every generation of this program, the FUV monitoring can be bootstrapped to previous programs, if needed. See the observing description for more details.The LTAIMAGE that started the second orbit of Visit 26 had the TDF down and the shutter closed. This caused the ACQ/IMAGE to miscenter the target by about 1.3". Visit 90 was added as a partial repeat from HOPR 89665. This visit is as close to a repeat of the 2nd orbit of Visi t 25 as possible. Due to time lost doing a full acq instead of a RE-ACQ, the following changes were made:1) Changed Visit number to 902) Schedulability set to 90%3) Before date set to Feb-19-2018, but the earlier the better

gPhoton: Time-tagged GALEX photon events analysis tools

NASA Astrophysics Data System (ADS)

Million, Chase C.; Fleming, S. W.; Shiao, B.; Loyd, P.; Seibert, M.; Smith, M.

2016-03-01

Written in Python, gPhoton calibrates and sky-projects the ~1.1 trillion ultraviolet photon events detected by the microchannel plates on the Galaxy Evolution Explorer Spacecraft (GALEX), archives these events in a publicly accessible database at the Mikulski Archive for Space Telescopes (MAST), and provides tools for working with the database to extract scientific results, particularly over short time domains. The software includes a re-implementation of core functionality of the GALEX mission calibration pipeline to produce photon list files from raw spacecraft data as well as a suite of command line tools to generate calibrated light curves, images, and movies from the MAST database.

The Far-UV Albedo of the Moon Determined from Dayside LAMP Observations

NASA Astrophysics Data System (ADS)

Bullock, Mark A.; Retherford, K. D.; Gladstone, R.; Greathouse, T. K.; Mandt, K. E.; Hendrix, A. R.; Feldman, P. D.; Miles, P. F.; Egan, A. F.

2013-10-01

The Lyman Alpha Mapping Project (LAMP) onboard the Lunar Reconnaissance Orbiter (LRO) has been recording far-UV photons reflected from the lunar surface almost continuously since December 2009 (Gladstone et al., 2010). One photon at a time, LAMP builds up spectra from 575 to 1965 Å with a resolution of 26 Å. We will present 3 years of accumulated LAMP lunar dayside spectral maps and derive the lunar geometric albedo spectrum for a range of phase angles. These LAMP observations can thus be used to reconstruct the lunar far-UV photometric function and refine photometric models of the lunar surface (Hapke, 1963; Lucke et al., 1976). We will also compare LAMP lunar dayside albedo with the albedo from 820-1840 Å obtained by the Hopkins Ultraviolet Telescope (HUT) on the March 1995 Astro-2 Space Shuttle mission (Henry et al., 1995). The improved lunar photometric functions from our analysis of LAMP albedo spectra will enable a better quantitative assessment of how phase angle and composition affect the Moon’s reflectance in the far-UV. Gladstone, G. R., Stern, S. A., Retherford, K. D., Black, R. K., Slater, D. C., Davis, M. W., Versteeg, M. H., Persson, K. B., Parker, J. W., Kaufmann, D. E., Egan, A. F., Greathouse, T. K., Feldman, P. D., Hurley, D., Pryor, W. R., Hendrix, A. R., 2010. LAMP: The lyman alpha mapping project on NASA's lunar reconnaissance orbiter mission. Space Science Reviews. 150, 161-181. Hapke, B. W., 1963. A theoretical photometric function for the lunar surface. Journal of Geophysical Research. 68, 4571-4586. Henry, R. C., Feldman, P. D., Kruk, J. W., Davidsen, A. F., Durrance, S. T., 1995. Ultraviolet Albedo of the Moon with the Hopkins Ultraviolet Telescope. The Astrophysical Journal Letters. 454, L69. Lucke, R. L., Henry, R. C., Fastie, W. G., 1976. Far-ultraviolet albedo of the moon. The Astronomical Journal. 81, 1162-1169.

Inferring Nighttime Ionospheric Parameters with the Far Ultraviolet Imager Onboard the Ionospheric Connection Explorer

NASA Astrophysics Data System (ADS)

Kamalabadi, Farzad; Qin, Jianqi; Harding, Brian J.; Iliou, Dimitrios; Makela, Jonathan J.; Meier, R. R.; England, Scott L.; Frey, Harald U.; Mende, Stephen B.; Immel, Thomas J.

2018-06-01

The Ionospheric Connection Explorer (ICON) Far Ultraviolet (FUV) imager, ICON FUV, will measure altitude profiles of OI 135.6 nm emissions to infer nighttime ionospheric parameters. Accurate estimation of the ionospheric state requires the development of a comprehensive radiative transfer model from first principles to quantify the effects of physical processes on the production and transport of the 135.6 nm photons in the ionosphere including the mutual neutralization contribution as well as the effect of resonant scattering by atomic oxygen and pure absorption by oxygen molecules. This forward model is then used in conjunction with a constrained optimization algorithm to invert the anticipated ICON FUV line-of-sight integrated measurements. In this paper, we describe the connection between ICON FUV measurements and the nighttime ionosphere, along with the approach to inverting the measured emission profiles to derive the associated O+ profiles from 150-450 km in the nighttime ionosphere that directly reflect the electron density in the F-region of the ionosphere.

Molecular diagnostics of FUV and accretion-related heating in protoplanetary disks

NASA Astrophysics Data System (ADS)

Adamkovics, Mate; Najita, Joan R.

2017-10-01

Emission lines from the terrestrial planet forming regions of disks are diagnostic of both the physical processes that heat the gas and the chemistry that determines the inventory of nebular material available during the epoch of planet formation. Interpreting emission spectra is informed by models of radiative, thermal, physical, and chemical processes, such as: (i) the radiation transfer of X-rays and FUV --- both continuum and Ly-alpha, (ii) direct and indirect heating processes such as the photoelectric effect and photochemical heating, (iii) heating related to turbulent processes and viscous dissipation, and (iv) gas phase chemical reaction kinetics. Many of these processes depend on a the spatial distribution of dust grains and their properties, which temporally evolve during the lifetime of the disk and the formation of planets. Studies of disks atmospheres often predict a layered structure of hot (a few thousand K) atomic gas overlying warm (a few hundred K) molecular gas, which is generally consistent with the isothermal slab emission models that are used to interpret emission spectra. However, detailed comparison between observed spectra and models (e.g., comparing the total columns and the radial extent of warm emitting species) is rare.We present results including the implementation of Ly-alpha scattering, which is an important part of the photochemical heating and FUV heating radiation budget. By including these processes we find a new component of the disk atmosphere; hot molecular gas at ~2000K within radial distances of ~0.5AU, which is consistent with observations of UV-fluorescent H2 emission (Ádámkovics, Najita & Glassgold, 2016). Constraining the most optimistic contribution of radiative heating mechanisms via X-rays and FUV together with a favorable comparison to observations, allows us to explore and evaluate additional heating mechanisms. We find that the total columns of warm (90-400K) emitting molecules such as CO, arising directly below

Cycle 24 COS FUV Internal/External Wavelength Scale Monitor

NASA Astrophysics Data System (ADS)

Fischer, William J.

2018-02-01

We report on the monitoring of the COS FUV wavelength scale zero-points during Cycle 24 in program 14855. Select cenwaves were monitored for all FUV gratings at Lifetime Position 3. The target and cenwaves have remained the same since Cycle 21, with a change only to the target acquisition sequence. All measured offsets are within the error goals, although the G140L cenwaves show offsets at the short-wavelength end of segment A that are approaching the tolerance. This behavior will be closely monitored in subsequent iterations of the program.

Second COS FUV Lifetime Position: Verification of FUV Bright Object Aperture (BOA) Operations (FCAL4)

NASA Astrophysics Data System (ADS)

Debes, John H.

2013-05-01

As part of the calibration of the second lifetime position on the Cosmic Origins Spectrograph (COS) far-ultraviolet (FUV) detectors, observations of the external target, G191-B2B, were obtained with the G130M, G160M, and G140L gratings in combi- nation with the Bright Object Aperture. The observations were designed to verify the performance of these spectroscopic modes by reproducing similar observations taken during the SM4 Servicing Mission Observatory Verification (SMOV) of COS. These observations allowed for a detailed determination of the spatial location and profile of the spectra from the three gratings, as well as a determination of the spectral resolution of the G130M grating prior to and after the lifetime move. In general, the negligi- ble differences which exist between the two lifetime positions can be attributed to slight differences in the optical path. In particular, the spectral resolution appears to be slightly improved. The stability of the absolute and relative flux calibration was investigated for G130M as well using STIS echelle data of G191-B2B. We determine that the COS ab- solute flux calibration with the BOA is accurate to 10%, and flux calibrated data are reproducible at the 1-2% level since SMOV.

Europa in the Far-UV: Spatial and Spectral Analysis from HST Observations

NASA Astrophysics Data System (ADS)

Becker, Tracy M.; Retherford, Kurt D.; Roth, Lorenz; Hendrix, Amanda R.; McGrath, Melissa; Alday, Juan; Saur, Joachim; Molyneux, Philippa M.; Raut, Ujjwal; Teolis, Benjamin

2017-10-01

We present a spatial and spectral analysis of Europa using far-UV observations from 1999 - 2015 made by the Space Telescope Imaging Spectrograph (STIS) on the Hubble Space Telescope (HST). Disk-integrated observations show that the far-UV spectrum from ~130 nm - 170 nm is blue (increasing albedo with decreasing wavelength) for the studied hemispheres: the leading, trailing, and anti-Jovian hemispheres. At Lyman-alpha (121.6 nm), the albedo of the trailing hemisphere continues the blue trend, but it reddens for the leading hemisphere. At wavelengths shorter than 133.5 nm, the leading hemisphere, which is brighter than the trailing hemisphere at near-UV and visible wavelengths, becomes darker than the trailing hemisphere. We find no evidence of a sharp water-ice absorption edge at 165 nm on any hemisphere of Europa, which is intriguing since such an absorption feature has been observed on most icy moons. This suggests the possibility that radiolytic alteration by Jovian magnetospheric plasma has made the surface more strongly absorbing, masking the absorption edge. We will also present a spatial map of Lyman-alpha across the entire surface of Europa. This map can then be used to distinguish variable H emissions in the atmosphere from surface reflectance, improving our ability to detect potential plumes occurring on the disk of Europa during an observation.

Nitrogen Incorporation in CH4-N2 Photochemical Aerosol Produced by Far UV Irradiation

NASA Technical Reports Server (NTRS)

Trainer, Melissa G.; Jimenez, Jose L.; Yung, Yuk L.; Toon, Owen B.; Tolbert, Margaret A.

2012-01-01

Nitrile incorporation into Titan aerosol accompanying hydrocarbon chemistry is thought to be driven by extreme UV wavelengths (lambda < 120 nm) or magnetospheric electrons in the outer reaches of the atmosphere. Far UV radiation (120 - 200 nm), which is transmitted down to the stratosphere of Titan, is expected to affect hydrocarbon chemistry only and not initiate the formation of nitrogenated species. We have examined the chemical properties of photochemical aerosol produced at far UV wavelengths using a High-Resolution Time-of-Flight Aerosol Mass Spectrometer (HR-ToF-AMS), which allows for elemental analysis of particle-phase products. Our results show that aerosol formed from CH4/N2 photochemistry contains a surprising amount of nitrogen, up to 16% by mass, a result of photolysis in the far UV. The proportion of nitrogenated organics to hydrocarbon species is shown to be correlated with that of N2 in the irradiated gas. The aerosol mass greatly decreases when N2 is removed, indicating that N2 plays a major role in aerosol production. Because direct dissociation of N2 is highly improbable given the immeasurably low cross-section at the wavelengths studied, the chemical activation of N2 must occur via another pathway. Any chemical activation of N2 at wavelengths > 120 nm is presently unaccounted for in atmospheric photochemical models. We suggest that reaction with CH radicals produced from CH4 photolysis may provide a mechanism for incorporating N into the molecular structure of the aerosol. Further work is needed to understand the chemistry involved, as these processes may have significant implications for prebiotic chemistry on the early Earth and similar planets.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Subramaniam, Annapurni; Sindhu, N.; Tandon, S. N.

We present early results from the Ultra-Violet Imaging Telescope (UVIT) on board the ASTROSAT observatory. We report the discovery of a hot companion associated with one of the blue straggler stars (BSSs) in the old open cluster, NGC 188. Using fluxes measured in four filters in UVIT’s far-UV (FUV) channel, and two filters in the near-UV (NUV) channel, we have constructed the spectral energy distribution (SED) of the star WOCS-5885, after combining with flux measurements from GALEX , Ultraviolet Imaging Telescope, Ultraviolet Optical Telescope, SPITZER , WISE , and several ground-based facilities. The resulting SED spans a wavelength range ofmore » 0.15 μ m to 7.8 μ m. This object is found to be one of the brightest FUV sources in the cluster. An analysis of the SED reveals the presence of two components. The cooler component is found to have a temperature of 6000 ± 150 K, confirming that it is a BSS. Assuming it to be a main-sequence star, we estimate its mass to be ∼1.1–1.2 M {sub ⊙}. The hotter component, with an estimated temperature of 17,000 ± 500 K, has a radius of ∼ 0.6 R {sub ⊙} and L ∼30 L {sub ⊙}. Bigger and more luminous than a white dwarf, yet cooler than a sub-dwarf, we speculate that it is a post-AGB/HB star that has recently transferred its mass to the BSS, which is known to be a rapid rotator. This binary system, which is the first BSS with a post-AGB/HB companion identified in an open cluster, is an ideal laboratory to study the process of BSS formation via mass transfer.« less

A Hot Companion to a Blue Straggler in NGC 188 as Revealed by the Ultra-Violet Imaging Telescope (UVIT) on ASTROSAT

NASA Astrophysics Data System (ADS)

Subramaniam, Annapurni; Sindhu, N.; Tandon, S. N.; Kameswara Rao, N.; Postma, J.; Côté, Patrick; Hutchings, J. B.; Ghosh, S. K.; George, K.; Girish, V.; Mohan, R.; Murthy, J.; Sankarasubramanian, K.; Stalin, C. S.; Sutaria, F.; Mondal, C.; Sahu, S.

2016-12-01

We present early results from the Ultra-Violet Imaging Telescope (UVIT) on board the ASTROSAT observatory. We report the discovery of a hot companion associated with one of the blue straggler stars (BSSs) in the old open cluster, NGC 188. Using fluxes measured in four filters in UVIT’s far-UV (FUV) channel, and two filters in the near-UV (NUV) channel, we have constructed the spectral energy distribution (SED) of the star WOCS-5885, after combining with flux measurements from GALEX, Ultraviolet Imaging Telescope, Ultraviolet Optical Telescope, SPITZER, WISE, and several ground-based facilities. The resulting SED spans a wavelength range of 0.15 μm to 7.8 μm. This object is found to be one of the brightest FUV sources in the cluster. An analysis of the SED reveals the presence of two components. The cooler component is found to have a temperature of 6000 ± 150 K, confirming that it is a BSS. Assuming it to be a main-sequence star, we estimate its mass to be ˜1.1-1.2 M ⊙. The hotter component, with an estimated temperature of 17,000 ± 500 K, has a radius of ˜ 0.6 R ⊙ and L ˜30 L ⊙. Bigger and more luminous than a white dwarf, yet cooler than a sub-dwarf, we speculate that it is a post-AGB/HB star that has recently transferred its mass to the BSS, which is known to be a rapid rotator. This binary system, which is the first BSS with a post-AGB/HB companion identified in an open cluster, is an ideal laboratory to study the process of BSS formation via mass transfer.

MAVEN/IUVS Apoapse Observations of the Martian FUV Dayglow

NASA Astrophysics Data System (ADS)

Correira, J.; Evans, J. S.; Stevens, M. H.; Schneider, N. M.; Stewart, I. F.; Deighan, J.; Jain, S.; Chaffin, M.; Crismani, M. M. J.; McClintock, B.; Holsclaw, G.; Lefèvre, F.; Lo, D.; Stiepen, A.; Clarke, J. T.; Mahaffy, P. R.; Bougher, S. W.; Bell, J. M.; Jakosky, B. M.

2015-12-01

We present FUV data (115 - 190 nm) from MAVEN/IUVS apoapse mode observations for the Oct 2014 through Feb 2015 time period. During apoapse mode the highly elliptical orbit of MAVEN allows for up to four apoapse disk images by IUVS per day. Maps of FUV feature intensities and intensity ratios as well as derived CO/CO2 and O/CO2 column density ratios will be shown. Column density ratios are derived from lookup tables created using the Atmospheric Ultraviolet Radiance Integrated Code [Strickland et al., 1999] in conjunction with observed intensity ratios. Column density ratios provide a measure of composition changes in the Martian atmosphere. Due to MAVEN's orbital geometry the observations from this time period focus on the southern hemisphere. The broad view provided by apoapse observations allows for the investigation of spatial and temporal variations (both long term and local time) of the atmospheric composition (via the column density ratios). IUVS FUV intensities and derived column density ratios will also be compared with model results from Mars Global Ionosphere/Thermosphere Model (MGITM) and the Mars Climate Database (MCD).

THE BURSTY STAR FORMATION HISTORIES OF LOW-MASS GALAXIES AT 0.4 < z < 1 REVEALED BY STAR FORMATION RATES MEASURED FROM H β AND FUV

DOE Office of Scientific and Technical Information (OSTI.GOV)

Guo, Yicheng; Faber, S. M.; Koo, David C.

2016-12-10

We investigate the burstiness of star formation histories (SFHs) of galaxies at 0.4 <  z  < 1 by using the ratio of star formation rates (SFRs) measured from H β and FUV (1500 Å) (H β -to-FUV ratio). Our sample contains 164 galaxies down to stellar mass ( M {sub *}) of 10{sup 8.5} M {sub ⊙} in the CANDELS GOODS-N region, where Team Keck Redshift Survey Keck/DEIMOS spectroscopy and Hubble Space Telescope /WFC3 F275W images from CANDELS and Hubble Deep UV Legacy Survey are available. When the ratio of H β - and FUV-derived SFRs is measured, dust extinction correction ismore » negligible (except for very dusty galaxies) with the Calzetti attenuation curve. The H β -to-FUV ratio of our sample increases with M {sub *} and SFR. The median ratio is ∼0.7 at M {sub *} ∼ 10{sup 8.5} M {sub ⊙} (or SFR ∼ 0.5 M {sub ⊙} yr{sup −1}) and increases to ∼1 at M {sub *} ∼ 10{sup 10} M {sub ⊙} (or SFR ∼ 10 M {sub ⊙} yr{sup −1}). At M {sub *} < 10{sup 9.5} M {sub ⊙}, our median H β -to-FUV ratio is lower than that of local galaxies at the same M {sub *}, implying a redshift evolution. Bursty SFH on a timescale of a few tens of megayears on galactic scales provides a plausible explanation for our results, and the importance of the burstiness increases as M {sub *} decreases. Due to sample selection effects, our H β -to-FUV ratio may be an upper limit of the true value of a complete sample, which strengthens our conclusions. Other models, e.g., non-universal initial mass function or stochastic star formation on star cluster scales, are unable to plausibly explain our results.« less

Short duration flares in GALEX data

NASA Astrophysics Data System (ADS)

Brasseur, Clara; Osten, Rachel A.

2018-06-01

Flares on cool stars indicate short time-scale magnetic reconnection processes that provide temporary increases in the stellar radiative output. While recent work has focused on long-duration flares from solar-like stars and those of lower mass, the existence of short-duration flares in the ultraviolet has not been systematically probed before. We will present an interesting population of short duration flares we discovered in a sample of ~37,000 light curves observed from 2009-2012 by the GALEX and Kepler missions. These flares range in duration from under a minute to a few minutes and are almost entirely distinct from a previous flare survey of Kepler data. We were able to detect this unique population of flares because the time resolution of the GALEX data allowed us to construct light curves with a 10 second cadence and thus detect shorter duration flares than could be detected within Kepler data. We applied algorithmic flare detection to a sample of ~37,000 stars, and identified a final count of 2,065 flares on 1,121 stars. We discuss the implication of these events for the flare frequency distributions of solar-like stars.

Inferred UV Fluence Focal-Spot Profiles from Soft X-Ray Pinhole Camera Measurements on OMEGA

NASA Astrophysics Data System (ADS)

Theobald, W.; Sorce, C.; Epstein, R.; Keck, R. L.; Kellogg, C.; Kessler, T. J.; Kwiatkowski, J.; Marshall, F. J.; Seka, W.; Shvydky, A.; Stoeckl, C.

2017-10-01

The drive uniformity of OMEGA cryogenic implosions is affected by UV beamfluence variations on target, which require careful monitoring at full laser power. This is routinely performed with multiple pinhole cameras equipped with charge-injection devices (CID's) that record the x-ray emission in the 3- to 7-keV photon energy range from an Au-coated target. The technique relies on the knowledge of the relation between x-ray fluence Fx and UV fluence FUV ,Fx FUVγ , with a measured γ = 3.42 for the CID-based diagnostic and 1-ns laser pulse. It is demonstrated here that using a back-thinned charge-coupled-device camera with softer filtration for x-rays with photon energies <2 keV and well calibrated pinhole provides a lower γ 2 and a larger dynamic range in the measured UV fluence. Inferred UV fluence profiles were measured for 100-ps and 1-ns laser pulses and were compared to directly measured profiles from a UV equivalent-target-plane diagnostic. Good agreement between both techniques is reported for selected beams. This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Number DE-NA0001944.

Understanding the Early Evolution of M dwarf Extreme Ultraviolet Radiation

NASA Astrophysics Data System (ADS)

Peacock, Sarah; Barman, Travis; Shkolnik, Evgenya

2015-11-01

The chemistry and evolution of planetary atmospheres depends on the evolution of high-energy radiation emitted by its host star. High levels of extreme ultraviolet (EUV) radiation can drastically alter the atmospheres of terrestrial planets through ionizing, heating, expanding, chemically modifying and eroding them during the first few billion years of a planetary lifetime. While there is evidence that stars emit their highest levels of far and near ultraviolet (FUV; NUV) radiation in the earliest stages of their evolution, we are currently unable to directly measure the EUV radiation. Most previous stellar atmosphere models under-predict FUV and EUV emission from M dwarfs; here we present new models for M stars that include prescriptions for the hot, lowest density atmospheric layers (chromosphere, transition region and corona), from which this radiation is emitted. By comparing our model spectra to GALEX near and far ultraviolet fluxes, we are able to predict the evolution of EUV radiation for M dwarfs from 10 Myr to a few Gyr. This research is the next major step in the HAZMAT (HAbitable Zones and M dwarf Activity across Time) project to analyze how the habitable zone evolves with the evolving properties of stellar and planetary atmospheres.

Searching for flares in GALEX data with gPhoton

NASA Astrophysics Data System (ADS)

Million, Chase; Fleming, Scott W.; Brasseur, Clara; Osten, Rachel A.; Bianchi, Luciana; Shiao, Bernie

2017-06-01

The Galaxy Evolution Explorer (GALEX) spacecraft observed a large fraction of the sky in two ultraviolet bands using micro-channel plate detectors with time resolutions of less than ten milliseconds. The gPhoton database of calibrated GALEX photon events at MAST has recently enabled a thorough search of this legacy data set for astrophysical variability at cadences shorter than the orbital period of the spacecraft. (https://archive.stsci.edu/prepds/gphoton/) We explore techniques for mining photon-level data for variability on timescales of seconds to minutes with an emphasis on dwarf star flares, which can be probed at lower energies and shorter durations with gPhoton than prior surveys. We present the early results of a systematic search for such events.

Global Far-ultraviolet Properties of the Cygnus Loop

NASA Astrophysics Data System (ADS)

Kim, Il-Joong; Seon, Kwang-Il; Lim, Yeo-Myeong; Lee, Dae-Hee; Han, Wonyong; Min, Kyoung-Wook; Edelstein, Jerry

2014-03-01

We present the C III λ977, O VI λλ1032, 1038 and N IV] λ1486 emission line maps of the Cygnus Loop, obtained with the newly processed data of the Spectroscopy of Plasma Evolution from Astrophysical Radiation (SPEAR; also known as FIMS) mission. In addition, the Si IV+O IV] line complexes around 1400 Å are resolved into two separate emission lines whose intensity demonstrates a relatively high Si IV region that was predicted in the previous study. The morphological similarity between the O VI and X-ray images, as well as a comparison of the O VI intensity with the value expected from the X-ray results, indicates that large portions of the observed O VI emissions could be produced from X-ray emitting gas. Comparisons of the far-ultraviolet (FUV) images with the optical and H I 21 cm images reveal spatial variations of shock-velocity populations and high FUV extinction in the direction of a previously identified H I cloud. By calculating the FUV line ratios for several subregions of the Cygnus Loop, we investigate the spatial variation of the population of radiative shock velocities as well as the effects of resonance scattering, X-ray emitting gas, and nonradiative shocks. The FUV and X-ray luminosity comparisons between the Cygnus Loop and the Vela supernova remnant suggest that the fraction of shocks in the early evolutionary stages is much larger in the Cygnus Loop.

HST STIS Images of the H-Lyman Alpha Emission and Disk-Reflected FUV Sunlight from the Upper Atmosphere of Uranus

NASA Astrophysics Data System (ADS)

Ballester, G. E.; Ben-Jaffel, L.; Clarke, J. T.; Gladstone, R.; Miller, S.; Trafton, L. M.; Trauger, J. T.

1998-09-01

An excess of H-Lyalpha emission from Uranus' sunlit hemisphere was detected by the IUE satellite in 1982, and some excess was confirmed with the Voyager 2 UVS during the 1986 encounter with Uranus. Radiative transfer modeling has shown that the Voyager H-Lyalpha observations did require emission additional to the scattered solar and IPM H-Lyalpha , and thus produced by internal processes in the upper atmosphere, such as aurora or other unidentified mechanisms. Subsequent IUE observations showed very large short- and long-term intensity variations that support an auroral source. However, although Voyager did identify UV auroral emissions by H_2 in the sunlit hemisphere, it did not detect a large H-Lyalpha auroral emission there, making it impossible to provide conclusive evidence that the H-Lyalpha enhancements observed by IUE are due to aurora. Auroral emissions are spatially confined, and resolution of the emission distribution could yield the needed evidence, or could alternatively provide observational clues to other possible causes of dayglow variations in the upper atmosphere. Uranus intrinsically weak H-Lyalpha emission ( ~ 1600 R on average) had not allowed for such an experiment in the past, but the high sensitivity in the FUV of the Space Telescope Imaging Spectrograph (STIS) on HST has now provided first images of Uranus in the FUV. The observations made on 29-30 July 1998 consisted of a FUV MAMA image in the open mode (25MAMA) and a consecutive image filtering out the H-Lyalpha (F25SRF2) to measure and subtract the disk reflected sunlight above 1250 Ang. A quick look at the data shows the H-Lyalpha emission and disk-reflected sunlight, with additional noise from the geocoronal background. We will present the results from these data, taking advantage of the time-tagging information to subtract the geocoronal background, and modeling of the underlying disk background. Four new observations will hopefully be made before October 1998 which will cover the

Colors of Dwarf Ellipticals from GALEX to WISE

NASA Astrophysics Data System (ADS)

Schombert, James M.

2018-02-01

Multicolor photometry is presented for a sample of 60 dwarf ellipticals (dE’s) selected by morphology. The sample uses data from GALEX, SDSS, and WISE to investigate the colors in the NUV, ugri, and W1 (3.4 μm) filters. We confirm the blueward shift in the color–magnitude relation (CMR) for dE’s, compared to the CMR for bright ellipticals, as seen in previous studies. However, we find that the deviation in color across the UV to near-IR for dE’s is a strong signal of a younger age for dE’s, one that indicates decreasing mean age with lower stellar mass. Lower mass dE’s are found to have mean ages of 4 Gyr and mean [Fe/H] values of ‑1.2. Age and metallicity increase tothe most massive dE’s, with mean ages similar to normal ellipticals (12 Gyr) and their lowest metallicities ([Fe/H] = ‑0.3). Deduced initial star formation rates for dE’s, combined with their current metallicities and central stellar densities, suggest a connection between field low surface brightness (LSB) dwarfs and cluster dE’s, where the cluster environment halts star formation for dE’s, triggering a separate evolutionary path.

An Ultraviolet and Near-Infrared View of NGC 4214: A Starbursting Core Embedded in a Low Surface Brightness Disk

NASA Astrophysics Data System (ADS)

Fanelli, Michael N.; Waller, William W.; Smith, Denise A.; Freedman, Wendy L.; Madore, Barry; Neff, Susan G.; O'Connell, Robert W.; Roberts, Morton S.; Bohlin, Ralph; Smith, Andrew M.; Stecher, Theodore P.

1997-05-01

During the Astro-2 Spacelab mission in 1995 March, the Ultraviolet Imaging Telescope (UIT) obtained far-UV (λ = 1500 Å) imagery of the nearby Sm/Im galaxy NGC 4214. The UIT images have a spatial resolution of ~3" and a limiting surface brightness, μ1500 > 25 mag arcsec-2, permitting detailed investigation of the intensity and spatial distribution of the young, high-mass stellar component. These data provide the first far-UV imagery covering the full spatial extent of NGC 4214. Comparison with a corresponding I-band image reveals the presence of a starbursting core embedded in an extensive low surface brightness disk. In the far-UV (FUV), NGC 4214 is resolved into several components: a luminous, central knot; an inner region (r <~ 2.5 kpc) with ~15 resolved sources embedded in bright, diffuse emission; and a population of fainter knots extending to the edge of the optically defined disk (r ~ 5 kpc). The FUV light, which traces recent massive star formation, is observed to be more centrally concentrated than the I-band light, which traces the global stellar population. The FUV radial light profile is remarkably well represented by an R1/4 law, providing evidence that the centrally concentrated massive star formation in NGC 4214 is the result of an interaction, possibly a tidal encounter, with a dwarf companion(s). The brightest FUV source produces ~8% of the global FUV luminosity. This unresolved source, corresponding to the Wolf-Rayet knot described by Sargent & Filippenko, is located at the center of the FUV light distribution, giving NGC 4214 an active galactic nucleus-like morphology. Another strong source is present in the I band, located 19" west, 10" north of the central starburst knot, with no FUV counterpart. The I-band source may be the previously unrecognized nucleus of NGC 4214 or an evolved star cluster with an age greater than ~200 Myr. The global star formation rate derived from the total FUV flux is consistent with rates derived using data at other

High Throughput, High Yield Fabrication of High Quantum Efficiency Back-Illuminated Photon Counting, Far UV, UV, and Visible Detector Arrays

NASA Technical Reports Server (NTRS)

Nikzad, Shouleh; Hoenk, M. E.; Carver, A. G.; Jones, T. J.; Greer, F.; Hamden, E.; Goodsall, T.

2013-01-01

In this paper we discuss the high throughput end-to-end post fabrication processing of high performance delta-doped and superlattice-doped silicon imagers for UV, visible, and NIR applications. As an example, we present our results on far ultraviolet and ultraviolet quantum efficiency (QE) in a photon counting, detector array. We have improved the QE by nearly an order of magnitude over microchannel plates (MCPs) that are the state-of-the-art UV detectors for many NASA space missions as well as defense applications. These achievements are made possible by precision interface band engineering of Molecular Beam Epitaxy (MBE) and Atomic Layer Deposition (ALD).

Rocket instrument for far-UV spectrophotometry of faint astronomical objects.

PubMed

Hartig, G F; Fastie, W G; Davidsen, A F

1980-03-01

A sensitive sounding rocket instrument for moderate (~10-A) resolution far-UV (lambda1160-lambda1750-A) spectrophotometry of faint astronomical objects has been developed. The instrument employs a photon-counting microchannel plate imaging detector and a concave grating spectrograph behind a 40-cm Dall-Kirkham telescope. A unique remote-control pointing system, incorporating an SIT vidicon aspect camera, two star trackers, and a tone-encoded command telemetry link, permits the telescope to be oriented to within 5 arc sec of any target for which suitable guide stars can be found. The design, construction, calibration, and flight performance of the instrument are discussed.

HST FUV monitoring of TW Hya

NASA Astrophysics Data System (ADS)

Guenther, Hans; Brickhouse, N. S.; Dupree, A. K.; Luna, G.; Schneider, P. C.; Wolk, S. J.

2014-01-01

Classical T Tauri stars (CTTS) show strong, broad and asymmetric FUV emission lines. Neither the width, nor the line profile is understood. Likely, different mechanisms influence the line profile; the best candidates are accretion, winds and stellar activity. We monitored the C IV 1548/1550 Å doublet in the nearby, bright CTTS TW Hya to correlate it with i) the cool wind, as seen in COS NUV Mg II line profiles, ii) the photometric period from joint ground-based monitoring, iii) the accretion rate as determined from the UV continuum and iv) the Ha line profile from independent ground-based observations. The observations span 10 orbits distributed over a few weeks to cover the typical time scales of stellar rotation, accretion and winds. On short time scales (seconds) the variability in the data is compatible with counting statistics when we take certain instrumental effects (the detector dead-time fraction increases when the wavelength calibration lamps are switched on). This rules out any type of coherent accretion shock fluctuation as predicted in some simulations. On longer time scales (days) variability of a factor of 3 in the continuum and similarly massive changes in the line shape are seen. The ratio of the two lines of the doublet indicates that the lines are optically thick, calling into question the idea that the blue-shifted components of the C IV lines are formed in the pre-shock region.

Design and fabrication of far ultraviolet filters based on π-multilayer technology in high-k materials

PubMed Central

Wang, Xiao-Dong; Chen, Bo; Wang, Hai-Feng; He, Fei; Zheng, Xin; He, Ling-Ping; Chen, Bin; Liu, Shi-Jie; Cui, Zhong-Xu; Yang, Xiao-Hu; Li, Yun-Peng

2015-01-01

Application of π-multilayer technology is extended to high extinction coefficient materials, which is introduced into metal-dielectric filter design. Metal materials often have high extinction coefficients in far ultraviolet (FUV) region, so optical thickness of metal materials should be smaller than that of the dielectric material. A broadband FUV filter of 9-layer non-periodic Al/MgF2 multilayer was successfully designed and fabricated and it shows high reflectance in 140–180 nm, suppressed reflectance in 120–137 nm and 181–220 nm. PMID:25687255

Far-ultraviolet spectral changes of titanium dioxide with gold nanoparticles by ultraviolet and visible light

NASA Astrophysics Data System (ADS)

Tanabe, Ichiro; Kurawaki, Yuji

2018-05-01

Attenuated total reflectance spectra including the far-ultraviolet (FUV, ≤ 200 nm) region of titanium dioxide (TiO2) with and without gold (Au) nanoparticles were measured. A newly developed external light-irradiation system enabled to observe spectral changes of TiO2 with Au nanoparticles upon light irradiations. Absorption in the FUV region decreased and increased by the irradiation with ultraviolet and visible light, respectively. These spectral changes may reflect photo-induced electron transfer from TiO2 to Au nanoparticles under ultraviolet light and from Au nanoparticles to TiO2 under visible light, respectively.

The Photoevaporation of a Neutral Structure by an EUV+FUV Radiation Field

NASA Astrophysics Data System (ADS)

Lora, Veronica; Vasconcelos, M. J.; Raga, A. C.; Cerqueira, A. H.; Esquivel, A.

The expansion of an HII region into a surrounding inhomogeneous molecular cloud, leads to the formation of elongated "elephant trunk" structures. The EUV photo-ionising radiation and FUV dissociating radiation from newly born stars photo-evaporate their parental neutral cloud, leading to the formation of dense clumps in the tips of elephant trunks, that could in principle eventually form stars. We study th effects of including a photo-dissociating FUV flux in models of fragmentation of a photo-evaporating, self-gravitating molecular cloud.

The Volatility of Far-Ultraviolet Radiation from Low-Mass Stars and Planetary Implications

NASA Astrophysics Data System (ADS)

Loyd, R. O. Parke

A low-mass star emits only 0.001-0.01% of its electromagnetic energy in the ultraviolet (100 - 1700 A), yet the implications for planets are profound. Radiation at the short-wavelength end of this range, the extreme ultraviolet (100 - 912 A), powers planetary atmospheric escape that can be observed through transit spectroscopy in the far ultraviolet (FUV; 912 - 1700 A). In addition, FUV light that penetrates further into a planet's atmosphere photolyzes molecules, driving nonthermal chemistry capable of producing O2 and O3 abiotically. I present results from extensive Hubble Space Telescope (HST) observations of the FUV emission from low-mass stars, focusing on its variability in time. Using all available archival data, I determined an astrophysical noise floor on detectable absorption in the C II, Si III, and Si IV FUV lines due to a transiting evaporating planet. I analyzed such a transit of the evaporating hot-Neptune GJ 436b, finding no detectable absorption in C II or Si III despite a large (>50%) transit in Lyalpha, but placing upper limits that agree with a photochemical-hydrodynamical model of the planetary outflow. These observations of GJ 436 were part of the MUSCLES Treasury Survey, a much larger dataset covering 7 M and 4 K dwarf stars. A time series analysis of all of these data constrained FUV flares on the surveyed M dwarfs, which I augmented with archival data on well-studied flare stars. The analysis confirmed that M dwarf flares are ubiquitous. In relative units, the FUV flares of the "inactive" MUSCLES M dwarfs are equally as energetic and frequent as those of the M dwarf flare stars. Both flare 3 orders of magnitude more frequently than the sun. Indeed, flares possibly (if not probably) dominate the energy budget of FUV emission from M dwarf stars. Highly energetic flares occurring roughly yearly could annihilate most of the ozone from an Earth-like atmosphere. However, the effect is short-lived, unless additional reactions not accounted for or

VizieR Online Data Catalog: The UV-bright Quasar Survey (UVQS) DR1 (Monroe+, 2016)

NASA Astrophysics Data System (ADS)

Monroe, T. R.; Prochaska, J. X.; Tejos, N.; Worseck, G.; Hennawi, J. F.; Schmidt, T.; Tumlinson, J.; Shen, Y.

2016-09-01

We have performed an all-sky survey for z~1, FUV-bright quasars selected from GALEX and WISE photometry. We generated a list of 1450 primary candidates (Table1). In several of the observing runs, conditions were unexpectedly favorable and we exhausted the primary candidates at certain right ascension ranges. To fill the remaining observing time, we generated a secondary candidate list. This secondary set of candidates is provided in Table2. We proceeded to obtain discovery-quality longslit spectra (i.e., low-dispersion, large wavelength coverage, modest signal-to-noise ratio (S/N) of our UV-bright Quasar Survey (UVQS) candidates in one calendar year. Our principal facilities were: (i) the dual Kast spectrometer on the 3m Shane telescope at the Lick Observatory; (ii) the Boller & Chivens (BCS) spectrometer on the Irenee du Pont 100'' telescope at the Las Campanas Observatory; and (iii) the Calar Alto Faint Object Spectrograph on the CAHA 2.2m telescope at the Calar Alto Observatory (CAHA). We acquired an additional ~20 spectra on larger aperture telescopes (Keck/ESI, MMT/MBC, Magellan/MagE) during twilight or under poor observing conditions. Typical exposure times were limited to <~200s, with adjustments for fainter sources or sub-optimal observing conditions. Table3 provides a list of the observed candidates. There are 93 sources with a good quality spectrum for which we cannot recover a secure redshift. The majority of these have been previously cataloged as blazars (or BL Lac objects). Table6 lists the sample of these unknowns. (6 data files).

COS LP4 FUV Target Acquisition Enabling and Verification

NASA Astrophysics Data System (ADS)

Penton, Steven V.

2016-10-01

This LP4 program is designed to verify the ability of the LV0058/LV0059 COS FSW to place an isolated point source at the center of the PSA, using FUV dispersed light target acquisition (TA) for COS (LP4-TA-COS). Tests will be performed for all 3 FUV TA modes (ACQ/SEARCH, ACQ/PEAKD, and ACQ/PEAKXD). It is sufficient to test ACQ/SEARCH and ACQ/PEAKD with only one grating, but all three FUV gratings need to be tested for the new (as of LV0054) ACQ/PEAKXD with NUM_POS>1 (also known internally, and in the spt files, as OPMODE=ACQ/PEAKD(XD) at the Fourth Lifetime Position (LP4). This program is modeled after the LP2 and LP3 versions of this program; 12797 and 13636.This program has specific visits to test each portion of the FUV spectroscopic TA process. Visits 01-05 will use the target AV18, while Visit 06 will observe (WD1657+343). Both targets are visible year round. For the LP4 enabling, several improvements to APT, the ground system, and the flight software (FSW) have greatly simplified the enabling process. There are now no non-standard exposures, or special commanding, in this program.Specifically; 1) We now use the LIFETIME-POS = LP4 functionality in APT & FSW to specify the LP. The old procedure of using LIFETIME-POS ="ALTERNATE" has been removed. FUV LPs are now called out by number (e.g., LP4). 2) We will be using the new NUM_POS > 1 PEAKXD algorithm at LP4 due to large geometric distortions (GD) at the "Y" detector positions of LP4. FUVA is particularly affected by GD rendering the old PEAKXD algorithm unable to center a target to the required XD accuracy at LP4. 3) Numerous FSW Patchable constants that were essential for PEAKXD operations at previous LPs are no longer required. These are the WCA-to-PSA offsets and XD plate-scales. Like PEAKD, the NUM_POS > 1 PEAKXD requires no patchable constant updates. At previous LPs, numerous updates to the patchable constants were required, this is not necessary for LP4 TA enabling.Prior to the submission of this

The Diffuse Radiation Field at High Galactic Latitudes

NASA Astrophysics Data System (ADS)

Akshaya, M. S.; Murthy, Jayant; Ravichandran, S.; Henry, R. C.; Overduin, James

2018-05-01

We have used GALEX observations of the north and south Galactic poles to study the diffuse ultraviolet background at locations where the Galactic light is expected to be at a minimum. We find offsets of 230–290 photon units in the far-UV (1531 Å) and 480–580 photon units in the near-UV (2361 Å). Of this, approximately 120 photon units can be ascribed to dust-scattered light and another 110 photon units (190 in the near-UV) to extragalactic radiation. The remaining radiation is, as yet, unidentified and amounts to 120–180 photon units in the far-UV and 300–400 photon units in the near-UV. We find that molecular hydrogen fluorescence contributes to the far-UV when the 100 μm surface brightness is greater than 1.08 MJy sr‑1.

Far-ultraviolet spectral changes of titanium dioxide with gold nanoparticles by ultraviolet and visible light.

PubMed

Tanabe, Ichiro; Kurawaki, Yuji

2018-05-15

Attenuated total reflectance spectra including the far-ultraviolet (FUV, ≤200nm) region of titanium dioxide (TiO 2 ) with and without gold (Au) nanoparticles were measured. A newly developed external light-irradiation system enabled to observe spectral changes of TiO 2 with Au nanoparticles upon light irradiations. Absorption in the FUV region decreased and increased by the irradiation with ultraviolet and visible light, respectively. These spectral changes may reflect photo-induced electron transfer from TiO 2 to Au nanoparticles under ultraviolet light and from Au nanoparticles to TiO 2 under visible light, respectively. Copyright © 2017 Elsevier B.V. All rights reserved.

VizieR Online Data Catalog: GUViCS. Ultraviolet Source Catalogs (Voyer+, 2014)

NASA Astrophysics Data System (ADS)

Voyer, E. N.; Boselli, A.; Boissier, S.; Heinis, S.; Cortese, L.; Ferrarese, L.; Cote, P.; Cuillandre, J.-C.; Gwyn, S. D. J.; Peng, E. W.; Zhang, H.; Liu, C.

2014-07-01

These catalogs are based on GALEX NUV and FUV source detections in and behind the Virgo Cluster. The detections are split into catalogs of extended sources and point-like sources. The UV Virgo Cluster Extended Source catalog (UV_VES.fit) provides the deepest and most extensive UV photometric data of extended galaxies in Virgo to date. If certain data is not available for a given source then a null value is entered (e.g. -999, -99). UV point-like sources are matched with SDSS, NGVS, and NED and the relevant photometry and further data from these databases/catalogs are provided in this compilation of catalogs. The primary GUViCS UV Virgo Cluster Point-Like Source catalog is UV_VPS.fit. This catalog provides the most useful GALEX pipeline NUV and FUV photometric parameters, and categorizes sources as stars, Virgo members, and background sources, when possible. It also provides identifiers for optical matches in the SDSS and NED, and indicates if a match exists in the NGVS, only if GUViCS-optical matches are one-to-one. NED spectroscopic redshifts are also listed for GUViCS-NED one-to-one matches. If certain data is not available for a given source a null value is entered. Additionally, the catalog is useful for quick access to optical data on one-to-one GUViCS-SDSS matches.The only parameter available in the catalog for UV sources that have multiple SDSS matches is the total number of multiple matches, i.e. SDSSNUMMTCHS. Multiple GUViCS sources matched to the same SDSS source are also flagged given a total number of matches, SDSSNUMMTCHS, of one. All other fields for multiple matches are set to a null value of -99. In order to obtain full optical SDSS data for multiply matched UV sources in both scenarios, the user can cross-correlate the GUViCS ID of the sources of interest with the full GUViCS-SDSS matched catalog in GUV_SDSS.fit. The GUViCS-SDSS matched catalog, GUV_SDSS.fit, provides the most relevant SDSS data on all GUViCS-SDSS matches, including one

New HST/COS FUV Modes G140L/800 and G160M/1533

NASA Astrophysics Data System (ADS)

Sankrit, Ravi; De Rosa, Gisella; Fischer, William J.; Fix, Mees B.; Fox, Andrew; Indriolo, Nick; James, Bethan; Magness, Camellia; Oliveira, Cristina M.; Penton, Steven V.; Plesha, Rachel; Rafelski, Marc; Roman-Duval, Julia; Sahnow, David J.; Snyder, Elaine M.; Taylor, Joanna M.; White, James

2018-06-01

We present two new observing modes that are being offered for the far-ultraviolet (FUV) channel on the Cosmic Origins Spectrograph (COS), and an initial overview of the science investigations they enable. The FUV channel on COS currently operates in the 900-2150 A wavelength region. It consists of two medium resolution gratings G130M and G160M, and a low resolution grating G140L. The detector consists of two segments (FUVB, shortward and FUVA, longward wavelengths) with a gap between them. Each grating has a number of central wavelength settings (cenwaves) available. The settings place different portions of the spectrum on the detector segments, and the focus at each cenwave is set to optimize spectral resolution in the middle of its wavelength range.The first new mode is G140L/800, which places 800-1950 A on FUVA. The grating rotation and focus for this mode are set to minimize the height of the spectrum on the detector, and thereby the background, in the region below 1100 A. This results in an increased sensitivity at these wavelengths compared to the 1280 cenwave. The second mode, G160M/1533, extends the short-wavelength coverage of the grating by 44 A to overlap with the longest wavelengths covered by the G130M/1222 setting. This allows a broad wavelength range to be covered using just two medium resolution settings without placing the key gain-sag contributor, Ly-alpha, on the detector.

The Lives and Deaths of Planets and Stars in the Value-Added UV Photon Catalog

NASA Astrophysics Data System (ADS)

Hogg, David

The lives and deaths of planets and stars in the Value-Added UV Photon Catalog Over its lifetime, the GALEX satellite has detected nearly two trillion photons with its ultraviolet- sensitive, photon-counting detectors. This time-tagged data set remains largely unexplored time-variable science. This proposal is to extract and calibrate the full photon time stream from the GALEX raw data products and to use that time stream to make discoveries in two rapidlydeveloping areas of astrophysical research: exoplanets around hot white dwarf stars and prompt ultraviolet emission from supernovae. It is only around white dwarf stars that rocky planets in the habitable zone generate frequent eclipses at large depth and with high likelihood. Theories of planet formation and evolution, now confronted with heterogeneous exoplanet discoveries around main-sequence stars, make strong predictions about planets around white dwarf stars, establishing unique and sensitive tests for ultraviolet surveys. Almost every GALEX pointing contains a bright white dwarf in the field of view. This project would be the first ever photon-limited and ultraviolet search for exoplanet eclipses. A preliminary study by the proposers has discovered new white-dwarf--main-sequence-star eclipsing binaries (and confirmed known systems) using time-resolved GALEX images, but because a calibrated photon stream is not available, it has not been possible to reach the photon limit. This proposal is to calibrate the photon time stream and perform the first UV search for planets, moons and asteroids around white dwarfs and other blue stars. The project will produce a statistically complete sample of exoplanets around white dwarfs and a similarly complete sample of binary stars. Although any exoplanet system is interesting in its own right, the proposers will also produce a probabilistic estimate of the frequency with which stellar remnants host planets of different kinds at different radii. Supernovae models have long

THE UV-BRIGHT QUASAR SURVEY (UVQS): DR1

DOE Office of Scientific and Technical Information (OSTI.GOV)

Monroe, TalaWanda R.; Tumlinson, Jason; Prochaska, J. Xavier

2016-07-01

We present the first data release (DR1) from our UV-bright Quasar Survey for new z  ∼ 1 active galactic nuclei (AGNs) across the sky. Using simple GALEX UV and WISE near-IR color selection criteria, we generated a list of 1450 primary candidates with FUV < 18.5 mag. We obtained discovery spectra, primarily on 3 m-class telescopes, for 1040 of these candidates and confirmed 86% as AGNs, with redshifts generally at z  > 0.5. Including a small set of observed secondary candidates, we report the discovery of 217 AGNs with FUV < 18 mag that previously had no reported spectroscopic redshift. These are excellent potential targets formore » UV spectroscopy before the end of the Hubble Space Telescope mission. The main data products are publicly available through the Mikulski Archive for Space Telescopes.« less

Star formation in H I tails: HCG 92, HCG 100 and six interacting systems

NASA Astrophysics Data System (ADS)

de Mello, D. F.; Urrutia-Viscarra, F.; Mendes de Oliveira, C.; Torres-Flores, S.; Carrasco, E. R.; Cypriano, E.

2012-11-01

We present new Gemini spectra of 14 new objects found within the H I tails of Hickson Compact Groups (HCGs) 92 and 100. Nine of them are Galaxy Evolution Explorer (GALEX) far-ultraviolet (FUV) and near-ultraviolet (NUV) sources. The spectra confirm that these objects are members of the compact groups and have metallicities close to solar, with an average value of 12+log(O/H) ˜ 8.5. They have average FUV luminosities 7 × 1040 erg s-1 and very young ages (<100 Myr), and two of them resemble tidal dwarf galaxy (TDG) candidates. We suggest that they were created within gas clouds that were ejected during galaxy-galaxy interactions into the intergalactic medium, which would explain the high metallicities of the objects, inherited from the parent galaxies from which the gas originated. We conduct a search for similar objects in six interacting systems with extended H I tails: NGC 2623, NGC 3079, NGC 3359, NGC 3627, NGC 3718 and NGC 4656. We found 35 ultraviolet (UV) sources with ages < 100 Myr; however, most of them are on average less luminous/massive than the UV sources found around HCG 92 and HCG 100. We speculate that this might be an environmental effect and that compact groups of galaxies are more favourable to TDG formation than other interacting systems. Based on observations obtained at the Gemini Observatory, which is operated by the Association of Universities for Research in Astronomy, Inc., under a cooperative agreement with the National Science Foundation (NSF) on behalf of the Gemini partnership: the NSF (United States), the Science and Technology Facilities Council (United Kingdom), the National Research Council (Canada), CONICYT (Chile), the Australian Research Council (Australia), Ministério da Ciência e Tecnologia (Brazil) and Ministerio de Ciencia, Tecnologia e Innovacion Productiva (Argentina) - Observing run ID: GN-2003A-Q-53 and GN-2007B-Q-87.

A comparison of FUV dayglows measured by STSAT-1/FIMS with the AURIC model in a geomagnetic quiet condition

NASA Astrophysics Data System (ADS)

Kam, Hosik; Kim, Yong Ha; Hong, Jun-Seok; Lee, Joon-Chan; Choi, Yeon-Ju; Min, Kyung Wook

2014-09-01

The Korea scientific microsatellite, STSAT-1 (Science and Technology Satellite-1), was launched in 2003 and observed far ultraviolet (FUV) airglow from the upper atmosphere with a Far-ultraviolet IMaging Spectrograph (FIMS) at an altitude of 690 km. The FIMS consists of a dual-band imaging spectrograph of 900-1150 Å (S-band) and 1340-1715 Å (L-band). Limb scanning observations were performed only at the S-band, resulting in intensity profiles of OI 989 Å, OI 1026 Å, NII 1085 Å and NI 1134 Å emission lines near the horizon. We compare these emission intensities with those computed by using a theoretical model, the AURIC (Atmospheric Ultraviolet Radiance Integrated Code). The intensities of the OI 1026 Å, NII 1085 Å and NI 1134 Å emissions measured by using the FIMS are overall consistent with the values computed by using AURIC under the thermospheric and solar activity conditions on August 6, 1984, which is close to the FIMS's observation condition. We find that the FIMS dayglow intensity profiles match reasonably well with AURIC intensity profiles for the MSIS90 oxygen atom density profiles within factors of 0.5 and 2. However, the FIMS intensities of the OI 989 Å line are about 2 ˜ 4 times stronger than the AURIC intensities, which is expected because AURIC does not properly simulate resonance scattering of airglow and solar photons at 989 Å by atomic oxygen in the thermosphere. We also find that the maximum tangential altitudes of the oxygen bearing dayglows (OI 989 Å, OI 1026 Å) are higher than those of the nitrogen-bearing dayglows (NII 1085 Å, NI 1134 Å), which is confirmed by using AURIC model calculations. This is expected because the oxygen atoms are distributed at higher altitudes in the thermosphere than the nitrogen molecules. Validations of the qualities of both the FIMS instrument and the AURIC model indicate that AURIC should be updated with improved thermospheric models and with measured solar FUV spectra for better agreement with the

GALEX 1st Light Near and Far Ultraviolet -100

NASA Image and Video Library

2003-05-28

NASA's Galaxy Evolution Explorer took this image on May 21 and 22, 2003. The image was made from data gathered by the two channels of the spacecraft camera during the mission's "first light" milestone. It shows about 100 celestial objects in the constellation Hercules. The reddish objects represent those detected by the camera's near ultraviolet channel over a 5-minute period, while bluish objects were detected over a 3-minute period by the camera's far ultraviolet channel. The Galaxy Evolution Explorer's first light images are dedicated to the crew of the Space Shuttle Columbia. The Hercules region was directly above Columbia when it made its last contact with NASA Mission Control on February 1, over the skies of Texas. The Galaxy Evolution Explorer launched on April 28 on a mission to map the celestial sky in the ultraviolet and determine the history of star formation in the universe over the last 10 billion years. http://photojournal.jpl.nasa.gov/catalog/PIA04281

Target of Opportunity - Far-UV Observations of Comet ISON with FORTIS

NASA Astrophysics Data System (ADS)

McCandliss, Stephan

The goal of this one year program is to acquire spectra and imagery of the sungrazing Oort cloud comet known as ISON in the far-UV bandpass between 800 -- 1950 Angstroms over a 1/2 degree field-of-view (FOV), during its ingress and egress from the sun. This bandpass and FOV provides access to a particularly rich set of spectral diagnostics for determining the volatile production rates of CO, H, C, C+, O and S, and to search for previously undetected atomic and molecular species such as Ar, N, N+, N2, O+ and O5+. We are particularly interested in searching for compositional changes associated with the intense heating episode at the comet's perihelion to address an outstanding question in cometary research; do Oort cloud comets carry a chemical composition similar to the proto-stellar molecular cloud from which the Solar System formed? Sounding rockets are uniquely suited to observing cometary emissions in the far-UV as they can point to within 25 degrees of the sun, whereas HST is limited to observations at angles greater than 50 degrees. The projected ephemeris of this comet shows that on ingress it is expected to reach ~ +4 mag at 25 degrees from the sun on 21 November 2013 and, should it survive its trip to within 2.7 Rsun from the sun, it is expected to reach a similar magnitude during egress at 25 degrees on 08 December 2013. This will be a reflight of the JHU sounding rocket borne spectro-telescope called FORTIS, currently scheduled to fly in May of 2013 on NASA sounding rocket 36.268 UG. The instrumental configuration of FORTIS is uniquely suited to accomplishing the goals of this task.

HST/COS Observations Of Lyman-α Emission From =0.03 Star Forming Galaxies

NASA Astrophysics Data System (ADS)

Wofford, Aida; Leitherer, C.; Salzer, J.; COS Science Team

2012-01-01

Although HI Lyman-alpha (Lyα, 1216 Å) is expected to be the strongest recombination line in HII nebulae, it is resonantly scattered by neutral hydrogen and is easily destroyed by dust. And yet, some star-forming galaxies show Lyα in emission. As evidenced by high dispersion HST/GHRS+STIS FUV spectroscopy of a handful of local (z<0.03) galaxies, the velocity shift between the neutral gas and the ionized gas plays a key role in driving the observed Lyα escape. We present HST/COS/G130M 1150-1450 Å (observed-frame) spectroscopy of 20 new targets located at a mean redshift of =0.03. The targets were selected from the KISSR survey on the basis of their GALEX FUV continuum luminosity. The observations cover the central 1-2 kpc of each galaxy, a wide range in metallicity ([O/H]=-0.83 to 0.38), and at least two orders of magnitude in FUV continuum luminosity. Seven objects show Lyα emission in the form of a P-Cygni or double-peaked profile. For 6/7 of the latter objects we are able to show that the emission is accompanied of O I gas outflows with speeds of up to 200 km/s. Two objects have Lyα luminosities comparable to the GALEX Lyα luminosities of targets at =0.3, but we find no Lyα emitters with EW(Lyα)>20 Å, such as those discovered with GALEX at z=0.2-0.35. We compare the observed Lyα/Hα line intensity ratios with predictions from dust-free cases A and B recombination under normal HII region conditions. We find evidence of O I gas inflow in the most metal-poor objects. This work is supported by NASA grant N1317.

NGC 3934: a shell galaxy in a compact galaxy environment

NASA Astrophysics Data System (ADS)

Bettoni, D.; Galletta, G.; Rampazzo, R.; Marino, A.; Mazzei, P.; Buson, L. M.

2011-10-01

Context. Mergers/accretions are considered the main drivers of the evolution of galaxies in groups. We investigate the NGC 3933 poor galaxy association that contains NGC 3934, which is classified as a polar-ring galaxy. Aims: The multi-band photometric analysis of NGC 3934 allows us to investigate the nature of this galaxy and to re-define the NGC 3933 group members with the aim to characterize the group's dynamical properties and its evolutionary phase. Methods: We imaged the group in the far (FUV, λeff = 1539 Å) and near (NUV, λeff = 2316 Å) ultraviolet (UV) bands of the Galaxy Evolution Explorer (GALEX). From the deep optical imaging we determined the fine structure of NGC 3934. We measured the recession velocity of PGC 213894 which shows that it belongs to the NGC 3933 group. We derived the spectral energy distribution (SED) from FUV to far-IR emission of the two brightest members of the group. We compared a grid of smooth particle hydrodynamical (SPH) chemo-photometric simulations with the SED and the integrated properties of NGC 3934 and NGC 3933 to devise their possible formation/evolutionary scenarios. Results: The NGC 3933 group has six bright members: a core composed of five galaxies, which have Hickson's compact group characteristics, and a more distant member, PGC 37112. The group velocity dispersion is relatively low (157 ± 44 km s-1). The projected mass, from the NUV photometry, is ~7 × 1012 M⊙ with a crossing time of 0.04 Hubble times, suggesting that at least in the center the group is virialized. We do not find evidence that NGC 3934 is a polar-ring galaxy, as suggested by the literature, but find that it is a disk galaxy with a prominent dust-lane structure and a wide type-II shell structure. Conclusions: NGC 3934 is a quite rare example of a shell galaxy in a likely dense galaxy region. The comparison between physically motivated SPH simulations with multi-band integrated photometry suggests that NGC 3934 is the product of a major merger.

A Simple Spreadsheet Program to Simulate and Analyze the Far-UV Circular Dichroism Spectra of Proteins

ERIC Educational Resources Information Center

Abriata, Luciano A.

2011-01-01

A simple algorithm was implemented in a spreadsheet program to simulate the circular dichroism spectra of proteins from their secondary structure content and to fit [alpha]-helix, [beta]-sheet, and random coil contents from experimental far-UV circular dichroism spectra. The physical basis of the method is briefly reviewed within the context of…

Far-ultraviolet absorbance detection of sugars and peptides by high-performance liquid chromatography.

PubMed

Uchiho, Yuichi; Goto, Yusuke; Kamahori, Masao; Aota, Toshimichi; Morisaki, Atsuki; Hosen, Yusuke; Koda, Kimiyoshi

2015-12-11

A far-ultraviolet (FUV)-absorbance detector with a transmission flow cell was developed and applied to detect absorbance of sugars and peptides by HPLC. The main inherent limitation of FUV-absorbance detection is the strong absorptions of solvents and atmospheric oxygen in the optical system as well as dissolved oxygen in the solvent. High absorptivity of the solvent and oxygen decreases transmission-light intensity in the flow cell and hinders the absorbance measurement. To solve the above drawbacks, the transmission-light intensity in the flow cell was increased by introducing a new optical system and a nitrogen-purging unit to remove the atmospheric oxygen. The optical system has a photodiode for detecting the reference light at a position of the minus-first-order diffracted light. In addition, acetonitrile and water were selected as usable solvents because of their low absorptivity in the FUV region. As a result of these implementations, the detectable wavelength of the FUV-absorbance detector (with a flow cell having an effective optical path length of 0.5mm) can be extended down to 175nm. Three sugars (glucose, fructose, and sucrose) were successfully detected with the FUV-absorbance detector. These detection results reveal that the absorption peak of sugar in liquid phase lies at around 178nm. The detection limit (S/N=3) in absorbance with a 0.5-mm flow cell at 180nm was 21μAU, which corresponds to 33, 60 and 60μM (198, 360, and 360pmol) for fructose, glucose, and sucrose, respectively. Also, the peptide Met-enkephalin could be detected with a high sensitivity at 190nm. The estimated detection limit (S/N=3) for Met-enkephalin is 29nM (0.29pmol), which is eight times lower than that at 220nm. Copyright © 2015 Elsevier B.V. All rights reserved.

VizieR Online Data Catalog: Dwarf galaxies surface brightness profiles. II. (Herrmann+, 2016)

NASA Astrophysics Data System (ADS)

Herrmann, K. A.; Hunter, D. A.; Elmegreen, B. G.

2016-07-01

Our galaxy sample (see Table1) is derived from the survey of nearby (>30Mpc) late-type galaxies conducted by Hunter & Elmegreen 2006 (cat. J/ApJS/162/49). The full survey includes 94 dwarf Irregulars (dIms), 26 Blue Compact Dwarfs (BCDs), and 20 Magellanic-type spirals (Sms). The 141 dwarf sample presented in the first paper of the present series (Paper I; Herrmann et al. 2013, Cat. J/AJ/146/104) contains one fewer Sm galaxy and two additional dIm systems than the original survey. A multi-wavelength data set has been assembled for these galaxies. The data include Hα images (129 galaxies with detections) to trace star formation over the past 10Myr (Hunter & Elmegreen 2004, Cat. J/AJ/128/2170) and satellite UV images (61 galaxies observed) obtained with the Galaxy Evolution Explorer (GALEX) to trace star formation over the past ~200Myr. The GALEX data include images from two passbands with effective wavelengths of 1516Å (FUV) and 2267Å (NUV) and resolutions of 4'' and 5.6'', respectively. Three of the galaxies in our sample with NUV data do not have FUV data. To trace older stars we have UBV images, which are sensitive to stars formed over the past 1Gyr for on-going star formation, and images in at least one band of JHK for 40 galaxies in the sample, which integrates the star formation over the galaxy's lifetime. Note that nine dwarfs are missing UB data and three more are missing U-band data. In addition we made use of 3.6μm images (39 galaxies) obtained with the Infrared Array Camera (IRAC) in the Spitzer archives also to probe old stars. (3 data files).

FAR-ULTRAVIOLET OBSERVATIONS OF THE SPICA NEBULA AND THE INTERACTION ZONE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Choi, Yeon-Ju; Min, Kyoung-Wook; Lim, Tae-Ho

2013-09-01

We report the analysis results of far-ultraviolet (FUV) observations, made for a broad region around {alpha} Vir (Spica) including the interaction zone of Loop I and the Local Bubble. The whole region was optically thin and a general correlation was seen between the FUV continuum intensity and the dust extinction, except in the neighborhood of the bright central star, indicating the dust scattering nature of the FUV continuum. We performed Monte Carlo radiative transfer simulations to obtain the optical parameters related to the dust scattering as well as to the geometrical structure of the region. The albedo and asymmetry factormore » were found to be 0.38 {+-} 0.06 and 0.46 {+-} 0.06, respectively, in good agreement with the Milky Way dust grain models. The distance to and the thickness of the interaction zone were estimated to be 70{sup +4}{sub -8} pc and 40{sup +8}{sub -10} pc, respectively. The diffuse FUV continuum in the northern region above Spica was mostly the result of scattering of the starlight from Spica, while that in the southern region was mainly due to the background stars. The C IV {lambda}{lambda}1548, 1551 emission was found throughout the whole region, in contrast to the Si II* {lambda}1532 emission which was bright only within the H II region. This indicates that the C IV line arises mostly at the shell boundaries of the bubbles, with a larger portion likely from the Loop I than from the Local Bubble side, whereas the Si II* line is from the photoionized Spica Nebula.« less

Photon counting photodiode array detector for far ultraviolet (FUV) astronomy

NASA Technical Reports Server (NTRS)

Hartig, G. F.; Moos, H. W.; Pembroke, R.; Bowers, C.

1982-01-01

A compact, stable, single-stage intensified photodiode array detector designed for photon-counting, far ultraviolet astronomy applications employs a saturable, 'C'-type MCP (Galileo S. MCP 25-25) to produce high gain pulses with a narrowly peaked pulse height distribution. The P-20 output phosphor exhibits a very short decay time, due to the high current density of the electron pulses. This intensifier is being coupled to a self-scanning linear photodiode array which has a fiber optic input window which allows direct, rigid mechanical coupling with minimal light loss. The array was scanned at a 250 KHz pixel rate. The detector exhibits more than adequate signal-to-noise ratio for pulse counting and event location. Previously announced in STAR as N82-19118

VizieR Online Data Catalog: IRX-β relation of HII regions in NGC628 (Ye+, 2016)

NASA Astrophysics Data System (ADS)

Ye, C.; Zou, H.; Lin, L.; Lian, J.; Hu, N.; Kong, X.

2016-10-01

NGC 628 has been observed by the PPAK IFS Nearby Galaxies Survey (PINGS) performed by the 3.5m telescope of the Calar Alto Observatory. The IFU provides a sampling of 2.7", an optical wavelength range of 3700-7000Å with a spectral resolution of ~8Å. The final data set comprises 11094 individual spectra, and the typical spatial resolution is about 3.5"-4". The slice image at the Hα wavelength is used to determine HII regions. FUV and near-UV (NUV) images of NGC 628 were taken by the Galaxy Evolution Explorer (GALEX), which are centered at wavelengths of 1516 and 2267Å. IR images were taken by Spitzer IRAC (3.6um, 8.0um) and MIPS (24um). The spatial resolutions of UV and IR images are 4.3", 5.3", 1.9", 2.8", and 6.4", respectively. We obtain these images from the data release website of Local Volume Legacy (LVL) survey DR5 (Dale+, 2009, J/ApJ/703/517; http://irsa.ipac.caltech.edu/data/SPITZER/LVL/). (2 data files).

Supermassive Black Holes in Late-type Spiral Galaxies: Constraining High Mass X-ray Binary Contamination

NASA Astrophysics Data System (ADS)

Dittenber, Benjamin; Hodges-Kluck, Edmund J.; Gallo, Elena

2018-06-01

Supermassive black holes (SMBHs) are known to commonly reside in the centers of large galaxies, but it is unclear whether they reside in smaller galaxies (M_* < M_sun x 10^10). X-rays are the most efficient way to detect low-level accretion, and provide the best measurement of the occupation fraction. X-ray binaries can be nearly as bright as SMBHs that have sub-Eddington accretion rates. High-mass XRBs (HMXBs) are especially problematic because they can get brighter than low-mass XRBs. However, previous estimates of HMXB contamination (based on the optical continuum to get the fraction of HMXBs expected in the nucleus) may be too high. A better approach is to use FUV or H-alpha, which directly trace ongoing star formation. We did this in a sample of 30 late-type galaxies with Chandra data. We calculate the total Expected X-ray Luminosity from XRBs (L_x) for each sample galaxy using existing relationships between X-ray luminosity and SFR. We estimate the fraction of the stellar formation in the nucleus by measuring the fraction of nuclear UV or H-alpha light there (total SFR is from the far infrared). Our Galex data is scaled with a sample of 6 Swift UVOT galaxies to measure with the same aperture size that previous works have used in the B-band. We found that the mean L_x,c for Swift scaled FUV ratios is ~2.025 x 10^36 and the mean L_x,c for H-alpha ratios is 7.693 x 10^35. These luminosities are 1.9 and 5 times smaller than B-band measured luminosities respectively. These results suggest that HMXBs do not contribute as much contamination in these galaxies as previously thought. Therefore, with a lower contamination, estimates of the occupation fraction from late-type galaxies are more reliable.

Definition of a metrology servo-system for a solar imaging fourier transform spectrometer working in the far UV (IFTSUV)

NASA Astrophysics Data System (ADS)

Ruiz de Galarreta Fanju, C.; Philippon, A.; Bouzit, M.; Appourchaux, T.; Vial, J.-C.; Maillard, J.-P.; Lemaire, P.

2017-11-01

The understanding of the solar outer atmosphere requires a simultaneous combination of imaging and spectral observations concerning the far UV lines that arise from the high chromospheres up to the corona. These observations must be performed with enough spectral, spatial and temporal resolution to reveal the small atmospheric structures and to resolve the solar dynamics. An Imaging Fourier Transform Spectrometer working in the far-UV (IFTSUV, Figure 1) is an attractive instrumental solution to fulfill these requirements. However, due to the short wavelength, to preserve IFTSUV spectral precision and Signal to Noise Ratio (SNR) requires a high optical surface quality and a very accurate (linear and angular) metrology to maintain the optical path difference (OPD) during the entire scanning process by: optical path difference sampling trigger; and dynamic alignment for tip/tilt compensation (Figure 2).

The Spartan-281 Far Ultraviolet Imaging Spectrograph

NASA Technical Reports Server (NTRS)

Carruthers, George R.; Heckathorn, Harry M.; Dufour, Reginald J.; Opal, Chet B.; Raymond, John C.

1988-01-01

The U.S. Naval Research Laboratory's Far Ultraviolet Imaging Spectrograph (FUVIS), currently under development for flight as a Spartan shuttle payload, is designed to perform spectroscopy of diffuse sources in the FUV with very high sensitivity and moderate spatial and spectral resolution. Diffuse nebulae, the general galactic background radiation, and artificially induced radiation associated with the Space Shuttle vehicle are sources of particular interest. The FUVIS instrument will cover the wavelength range of 970-2000 A with selectable resolutions of 5 and 30 A. It is a slit imaging spectrograph having 3 arcmin spatial resolution along its 2.7 deg long slit.

GADICON spectrometer for ionosphere far-ultraviolet observation: prototype design, manufacturing, and testing.

PubMed

Yu, Lei

2016-08-20

The design, manufacturing, and testing of an imaging spectrometer prototype that will address new scientific requirements by the observation of the lower atmosphere's impact on the ionosphere are presented. The two sided lateral limb observation covering 130-180 nm far-ultraviolet (FUV) region allows the instrument to perform particle measurements in the daytime and nighttime. In this paper, we focus upon the working design principle, observation, and calibration.

Spectral Properties of Gas-phase Condensed Fullerene-like Carbon Nanoparticles from Far-ultraviolet to Infrared Wavelengths

NASA Astrophysics Data System (ADS)

Jäger, C.; Mutschke, H.; Henning, Th.; Huisken, F.

2008-12-01

Carbon solids are ubiquitous material in interstellar space. However, the formation pathway of carbonaceous matter in astrophysical environments, as well as in terrestrial gas-phase condensation reactions, is not yet understood. Laser ablation of graphite in different quenching gas atmospheres, such as pure He, He/H2, and He/H2O at varying pressures, is used to synthesize very small, fullerene-like carbon nanoparticles. The particles are characterized by very small diameters between 1 and 4 nm and a disturbed onion-like structure. The soot particles extracted from the condensation zone obviously represent a very early stage of particle condensation. The spectral properties have been measured from the far-ultraviolet (FUV; λ = 120 nm) to the mid-infrared (MIR; λ = 15 μm). The seedlike soot particles show strong absorption bands in the 3.4 μm range. The profile and the intensity pattern of the 3.4 μm band of the diffuse interstellar medium can be well reproduced by the measured 3.4 μm profile of the condensed particles; however, all the carbon which is left to form solids is needed to fit the intensity of the interstellar bands. In contrast to the assumption that onion-like soot particles could be the carriers of the interstellar ultraviolet (UV) bump, our very small onion-like carbon nanoparticles do not show distinct UV bands due to (π-π*) transitions.

The radio continuum-star formation rate relation in WSRT sings galaxies

DOE Office of Scientific and Technical Information (OSTI.GOV)

Heesen, Volker; Brinks, Elias; Leroy, Adam K.

2014-05-01

We present a study of the spatially resolved radio continuum-star formation rate (RC-SFR) relation using state-of-the-art star formation tracers in a sample of 17 THINGS galaxies. We use SFR surface density (Σ{sub SFR}) maps created by a linear combination of GALEX far-UV (FUV) and Spitzer 24 μm maps. We use RC maps at λλ22 and 18 cm from the WSRT SINGS survey and Hα emission maps to correct for thermal RC emission. We compare azimuthally averaged radial profiles of the RC and FUV/mid-IR (MIR) based Σ{sub SFR} maps and study pixel-by-pixel correlations at fixed linear scales of 1.2 and 0.7more » kpc. The ratio of the integrated SFRs from the RC emission to that of the FUV/MIR-based SF tracers is R{sub int}=0.78±0.38, consistent with the relation by Condon. We find a tight correlation between the radial profiles of the radio and FUV/MIR-based Σ{sub SFR} for the entire extent of the disk. The ratio R of the azimuthally averaged radio to FUV/MIR-based Σ{sub SFR} agrees with the integrated ratio and has only quasi-random fluctuations with galactocentric radius that are relatively small (25%). Pixel-by-pixel plots show a tight correlation in log-log diagrams of radio to FUV/MIR-based Σ{sub SFR}, with a typical standard deviation of a factor of two. Averaged over our sample we find (Σ{sub SFR}){sub RC}∝(Σ{sub SFR}){sub hyb}{sup 0.63±0.25}, implying that data points with high Σ{sub SFR} are relatively radio dim, whereas the reverse is true for low Σ{sub SFR}. We interpret this as a result of spectral aging of cosmic-ray electrons (CREs), which are diffusing away from the star formation sites where they are injected into the interstellar medium. This is supported by our finding that the radio spectral index is a second parameter in pixel-by-pixel plots: those data points dominated by young CREs are relatively radio dim, while those dominated by old CREs are slightly more RC bright than what would be expected from a linear extrapolation. We studied the

Water in star-forming regions with Herschel (WISH). VI. Constraints on UV and X-ray irradiation from a survey of hydrides in low- to high-mass young stellar objects

NASA Astrophysics Data System (ADS)

Benz, A. O.; Bruderer, S.; van Dishoeck, E. F.; Melchior, M.; Wampfler, S. F.; van der Tak, F.; Goicoechea, J. R.; Indriolo, N.; Kristensen, L. E.; Lis, D. C.; Mottram, J. C.; Bergin, E. A.; Caselli, P.; Herpin, F.; Hogerheijde, M. R.; Johnstone, D.; Liseau, R.; Nisini, B.; Tafalla, M.; Visser, R.; Wyrowski, F.

2016-05-01

Context. Hydrides are simple compounds containing one or a few hydrogen atoms bonded to a heavier atom. They are fundamental precursor molecules in cosmic chemistry and many hydride ions have become observable in high quality for the first time thanks to the Herschel Space Observatory. Ionized hydrides such as CH+ and OH+ (and also HCO+), which affect the chemistry of molecules such as water, provide complementary information on irradiation by far-UV (FUV) or X-rays and gas temperature. Aims: We explore hydrides of the most abundant heavier elements in an observational survey covering young stellar objects (YSOs) with different mass and evolutionary state. The focus is on hydrides associated with the dense protostellar envelope and outflows, contrary to previous work that focused on hydrides in diffuse foreground clouds. Methods: Twelve YSOs were observed with HIFI on Herschel in six spectral settings providing fully velocity-resolved line profiles as part of the Water in star-forming regions with Herschel (WISH) program. The YSOs include objects of low (Class 0 and I), intermediate, and high mass, with luminosities ranging from 4 L⊙ to 2 × 105 L⊙. Results: The targeted lines of CH+, OH+, H2O+, C+, and CH are detected mostly in blue-shifted absorption. H3O+ and SH+ are detected in emission and only toward some high-mass objects. The observed line parameters and correlations suggest two different origins related to gas entrained by the outflows and to the circumstellar envelope. The derived column densities correlate with bolometric luminosity and envelope mass for all molecules, best for CH, CH+, and HCO+. The column density ratios of CH+/OH+ are estimated from chemical slab models, assuming that the H2 density is given by the specific density model of each object at the beam radius. For the low-mass YSOs the observed ratio can be reproduced for an FUV flux of 2-400 times the interstellar radiation field (ISRF) at the location of the molecules. In two high

The Hubble Deep UV Legacy Survey (HDUV): Survey Overview and First Results

NASA Astrophysics Data System (ADS)

Oesch, Pascal; Montes, Mireia; HDUV Survey Team

2015-08-01

Deep HST imaging has shown that the overall star formation density and UV light density at z>3 is dominated by faint, blue galaxies. Remarkably, very little is known about the equivalent galaxy population at lower redshifts. Understanding how these galaxies evolve across the epoch of peak cosmic star-formation is key to a complete picture of galaxy evolution. Here, we present a new HST WFC3/UVIS program, the Hubble Deep UV (HDUV) legacy survey. The HDUV is a 132 orbit program to obtain deep imaging in two filters (F275W and F336W) over the two CANDELS Deep fields. We will cover ~100 arcmin2, reaching down to 27.5-28.0 mag at 5 sigma. By directly sampling the rest-frame far-UV at z>~0.5, this will provide a unique legacy dataset with exquisite HST multi-wavelength imaging as well as ancillary HST grism NIR spectroscopy for a detailed study of faint, star-forming galaxies at z~0.5-2. The HDUV will enable a wealth of research by the community, which includes tracing the evolution of the FUV luminosity function over the peak of the star formation rate density from z~3 down to z~0.5, measuring the physical properties of sub-L* galaxies, and characterizing resolved stellar populations to decipher the build-up of the Hubble sequence from sub-galactic clumps. This poster provides an overview of the HDUV survey and presents the reduced data products and catalogs which will be released to the community.

Using XMM-OM UV Data to Study Cluster Galaxy Evolution

NASA Astrophysics Data System (ADS)

Miller, Neal A.; O'Steen, R.

2010-01-01

The XMM-Newton satellite includes an Optical Monitor (XMM-OM) for the simultaneous observation of its X-ray targets at UV and optical wavelengths. On account of XMM's excellent characteristics for the observation of the hot intracluster medium, a large number of galaxy clusters have been observed by XMM and there is consequently a large and virtually unused database of XMM-OM UV data for galaxies in the cores of these clusters. We have begun a program to capitalize on such data, and describe here our efforts on a subsample of ten nearby clusters having XMM-OM, GALEX, and SDSS data. We present our methods for photometry and calibration of the XMM-OM UV data, and briefly present some applications including galaxy color magnitude diagrams (and identification of the red sequence, blue cloud, and green valley) and SED fitting (and galaxy stellar masses and star formation histories). Support for this work is provided by NASA Award Number NNX09AC76G.

Filters for the International Solar Terrestrial Physics (ISTP) mission far ultraviolet imager

NASA Technical Reports Server (NTRS)

Zukic, Muamer; Torr, Douglas G.; Kim, Jongmin; Spann, James F.; Torr, Marsha R.

1993-01-01

The far ultraviolet (FUV) imager for the International Solar Terrestrial Physics (ISTP) mission is designed to image four features of the aurora: O I lines at 130.4 nm and 135.6 nm and the N2 Lyman-Birge-Hopfield (LBH) bands between 140 nm - 160 nm (LBH long) and 160 nm - 180 nm (LBH long). In this paper we report the design and fabrication of narrow-band and broadband filters for the ISTP FUV imager. Narrow-band filters designed and fabricated for the O I lines have a bandwidth of less than 5 nm and a peak transmittance of 23.9 percent and 38.3 percent at 130.4 nm and 135.6 nm, respectively. Broadband filters designed and fabricated for LBH bands have the transmittance close to 60 percent. Blocking of out-of-band wavelengths for all filters is better than 5x10(exp -3) percent with the transmittance at 121.6 nm of less than 10(exp -6) percent.

A photon-counting photodiode array detector for far ultraviolet (FUV) astronomy

NASA Technical Reports Server (NTRS)

Hartig, G. F.; Moos, H. W.; Pembroke, R.; Bowers, C.

1982-01-01

A compact, stable, single-stage intensified photodiode array detector designed for photon-counting, far ultraviolet astronomy applications employs a saturable, 'C'-type MCP (Galileo S. MCP 25-25) to produce high gain pulses with a narrowly peaked pulse height distribution. The P-20 output phosphor exhibits a very short decay time, due to the high current density of the electron pulses. This intensifier is being coupled to a self-scanning linear photodiode array which has a fiber optic input window which allows direct, rigid mechanical coupling with minimal light loss. The array was scanned at a 250 KHz pixel rate. The detector exhibits more than adequate signal-to-noise ratio for pulse counting and event location.

TRACING REJUVENATION EVENTS IN NEARBY S0 GALAXIES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Marino, Antonietta; Bianchi, Luciana; Thilker, David A.

2011-08-01

With the aim of characterizing rejuvenation processes in early-type galaxies, we analyzed five barred S0 galaxies showing a prominent outer ring in ultraviolet (UV) imaging. We analyzed Galaxy Evolution Explorer far-UV (FUV) and near-UV (NUV), and optical data using stellar population models and estimated the age and the stellar mass of the entire galaxies and the UV-bright ring structures. Outer rings consist of young ({approx}<200 Myr old) stellar populations, accounting for up to 70% of the FUV flux but containing only a few percent of the total stellar mass. Integrated photometry of the whole galaxies places four of these objectsmore » on the green valley, indicating a globally evolving nature. We suggest such galaxy evolution is likely driven by bar-induced instabilities, i.e., inner secular evolution, that conveys gas to the nucleus and the outer rings. At the same time, H I observations of NGC 1533 and NGC 2962 suggest external gas re-fueling can play a role in the rejuvenation processes of such galaxies.« less

The Ultraviolet Spectrograph on NASA's Juno Mission

NASA Astrophysics Data System (ADS)

Gladstone, G. Randall; Persyn, Steven C.; Eterno, John S.; Walther, Brandon C.; Slater, David C.; Davis, Michael W.; Versteeg, Maarten H.; Persson, Kristian B.; Young, Michael K.; Dirks, Gregory J.; Sawka, Anthony O.; Tumlinson, Jessica; Sykes, Henry; Beshears, John; Rhoad, Cherie L.; Cravens, James P.; Winters, Gregory S.; Klar, Robert A.; Lockhart, Walter; Piepgrass, Benjamin M.; Greathouse, Thomas K.; Trantham, Bradley J.; Wilcox, Philip M.; Jackson, Matthew W.; Siegmund, Oswald H. W.; Vallerga, John V.; Raffanti, Rick; Martin, Adrian; Gérard, J.-C.; Grodent, Denis C.; Bonfond, Bertrand; Marquet, Benoit; Denis, François

2017-11-01

The ultraviolet spectrograph instrument on the Juno mission (Juno-UVS) is a long-slit imaging spectrograph designed to observe and characterize Jupiter's far-ultraviolet (FUV) auroral emissions. These observations will be coordinated and correlated with those from Juno's other remote sensing instruments and used to place in situ measurements made by Juno's particles and fields instruments into a global context, relating the local data with events occurring in more distant regions of Jupiter's magnetosphere. Juno-UVS is based on a series of imaging FUV spectrographs currently in flight—the two Alice instruments on the Rosetta and New Horizons missions, and the Lyman Alpha Mapping Project on the Lunar Reconnaissance Orbiter mission. However, Juno-UVS has several important modifications, including (1) a scan mirror (for targeting specific auroral features), (2) extensive shielding (for mitigation of electronics and data quality degradation by energetic particles), and (3) a cross delay line microchannel plate detector (for both faster photon counting and improved spatial resolution). This paper describes the science objectives, design, and initial performance of the Juno-UVS.

Far-ultraviolet Spectroscopy of the Nova-like Variable KQ Monocerotis: A New SW Sextantis Star?

NASA Astrophysics Data System (ADS)

Wolfe, Aaron; Sion, Edward M.; Bond, Howard E.

2013-06-01

New optical spectra obtained with the SMARTS 1.5 m telescope and archival International Ultraviolet Explorer (IUE) far-ultraviolet (FUV) spectra of the nova-like variable KQ Mon are discussed. The optical spectra reveal Balmer lines in absorption as well as He I absorption superposed on a blue continuum. The 2011 optical spectrum is similar to the KPNO 2.1 m IIDS spectrum we obtained 33 years earlier except that the Balmer and He I absorption is stronger in 2011. Far-ultraviolet IUE spectra reveal deep absorption lines due to C II, Si III, Si IV, C IV, and He II, but no P Cygni profiles indicative of wind outflow. We present the results of the first synthetic spectral analysis of the IUE archival spectra of KQ Mon with realistic optically thick, steady-state, viscous accretion-disk models with vertical structure and high-gravity photosphere models. We find that the photosphere of the white dwarf (WD) contributes very little FUV flux to the spectrum and is overwhelmed by the accretion light of a steady disk. Disk models corresponding to a WD mass of ~0.6 M ⊙, with an accretion rate of order 10-9 M ⊙ yr-1 and disk inclinations between 60° and 75°, yield distances from the normalization in the range of 144-165 pc. KQ Mon is discussed with respect to other nova-like variables. Its spectroscopic similarity to the FUV spectra of three definite SW Sex stars suggests that it is likely a member of the SW Sex class and lends support to the possibility that the WD is magnetic.

Experimental study of heterogeneous organic chemistry induced by far ultraviolet light: Implications for growth of organic aerosols by CH3 addition in the atmospheres of Titan and early Earth

NASA Astrophysics Data System (ADS)

Hong, Peng; Sekine, Yasuhito; Sasamori, Tsutoni; Sugita, Seiji

2018-06-01

Formation of organic aerosols driven by photochemical reactions has been observed and suggested in CH4-containing atmospheres, including Titan and early Earth. However, the detailed production and growth mechanisms of organic aerosols driven by solar far ultraviolet (FUV) light remain poorly constrained. We conducted laboratory experiments simulating photochemical reactions in a CH4sbnd CO2 atmosphere driven by the FUV radiations dominated by the Lyman-α line. In the experiments, we analyzed time variations in thickness and infrared spectra of solid organic film formed on an optical window in a reaction cell. Gas species formed by FUV irradiation were also analyzed and compared with photochemical model calculations. Our experimental results show that the growth rate of the organic film decreases as the CH4/CO2 ratio of reactant gas mixture decreases, and that the decrease becomes very steep for CH4/CO2 < 1. Comparison with photochemical model calculations suggests that polymerizations of gas-phase hydrocarbons, such as polyynes and aromatics, cannot account for the growth rate of the organic film but that the addition reaction of CH3 radicals onto the organic film with the reaction probability around 10-2 can explain the growth rate. At CH4/CO2 < 1, etching by O atom formed by CO2 photolysis would reduce or inhibit the growth of the organic film. Our results suggest that organic aerosols would grow through CH3 addition onto the surface during the precipitation of aerosol particles in the middle atmosphere of Titan and early Earth. On Titan, effective CH3 addition would reduce C2H6 production in the atmosphere. On early Earth, growth of aerosol particles would be less efficient than those on Titan, possibly resulting in small-sized monomers and influencing UV shielding.

The Surprising Absence of Absorption in the Far-ultraviolet Spectrum of Mrk 231

NASA Technical Reports Server (NTRS)

Veilleux, S.; Trippe, M.; Hamann, F.; Rupke, D. S. N.; Tripp, T. M.; Netzer, H.; Lutz, D.; Sembach, K. R.; Krug, H.; Teng, Stacy H.;

The albedo and scattering phase function of interstellar dust and the diffuse background at far-ultraviolet wavelengths.

PubMed

Hurwitz, M; Bowyer, S; Martin, C

1991-05-01

We have determined the scattering parameters of dust in the interstellar medium at far-ultraviolet (FUV) wavelengths (1415-1835 angstroms). Our results are based on spectra of the diffuse background taken with the Berkeley UVX spectrometer. The unique design of this instrument makes possible for the first time accurate determination of the background both at high Galactic latitude, where the signal is intrinsically faint, and at low Galactic latitude, where direct starlight has heretofore compromised measurements of the diffuse emission. Because the data are spectroscopic, the continuum can be distinguished from the atomic and molecular transition features which also contribute to the background. We find the continuum intensity to be well correlated with the Galactic neutral hydrogen column density until saturation at about 1200 photons cm-2 s-1 sr-1 angstrom-1 is reached where tau FUV approximately 1. Our measurement of the intensity where tau FUV > or = 1 is crucial to the determination of the scattering properties of the grains. We interpret the data with a detailed radiative transfer model and conclude that the FUV albedo of the grains is low (<25%) and that the grains scatter fairly isotropically. We evaluate models of dust composition and grain-size distribution and compare their predictions with these new results. We present evidence that, as the Galactic neutral hydrogen column density approaches zero, the FUV continuum background arises primarily from scattering by dust, which implies that dust may be present in virtually all view directions. A non-dust-scattering continuum component has also been identified, with an intensity (external to the foreground Galactic dust) of about 115 photons cm-2 s-1 angstrom-1. With about half this intensity accounted for by two-photon emission from Galactic ionized gas, we identify roughly 50 photons cm-2 s-1 sr-1 angstrom-1 as a true extragalactic component.

Pressure shifts and abundance gradients in the atmosphere of the DAZ white dwarf GALEX J193156.8+011745

NASA Astrophysics Data System (ADS)

Vennes, S.; Kawka, A.; Németh, P.

2011-06-01

We present a detailed model atmosphere analysis of high-dispersion and high signal-to-noise ratio spectra of the heavily polluted DAZ white dwarf GALEX J1931+0117. The spectra obtained with the Very Large Telescope (VLT)-Kueyen/UV-Visual Echelle Spectrograph show several well-resolved Si II spectral lines enabling a study of pressure effects on line profiles. We observed large Stark shifts in silicon lines in agreement with theoretical predictions and laboratory measurements. Taking into account Stark shifts in the calculation of synthetic spectra, we reduced the scatter in individual line radial velocity measurements from ˜3 to ≲1 km s-1. We present revised abundances of O, Mg, Si, Ca and Fe based on a critical review of line-broadening parameters and oscillator strengths. The new measurements are generally in agreement with our previous analysis with the exception of magnesium with a revised abundance of a factor of 2 lower than previously estimated. The magnesium, silicon and iron abundances exceed solar abundances, but the oxygen and calcium abundances are below solar. Also, we compared the observed line profiles to synthetic spectra computed with variable accretion rates and vertical abundance distributions assuming diffusive steady state. The inferred accretion rates vary from ? for calcium to 2 × 109 g s-1 for oxygen. We find that the accretion flow must be oxygen rich while being deficient in calcium relative to solar abundances. The lack of radial velocity variations between two measurement epochs suggests that GALEX J1931+0117 is probably not in a close binary and that the source of the accreted material resides in a debris disc. Based on observations made with European Southern Observatory (ESO) telescopes at the La Silla Paranal Observatory under programme 283.D-5060.

Investigating an SPI and Measuring Baseline FUV Variability in the GJ 436 Hot-Neptune System

NASA Astrophysics Data System (ADS)

Loyd, R. O.

2017-08-01

Closely-orbiting, massive planets can measurably affect the activity of their host star through tides, magnetic disturbances, or even mass transfer. Observations of these star planet interactions (SPIs) provide a window into stellar and planetary physics that may eventually lead to constraints on planetary magnetic fields. Recently, the MUSCLES Treasury Survey of 11 exoplanet host stars revealed correlations providing the first-ever evidence of SPIs in M dwarf systems. This evidence additionally suggests that N V 1238,1242 Angstrom emission best traces SPIs, a feature that merits further investigation. To this end, we propose an experiment using the M dwarf + hot Neptune system GJ 436 that will also benefit upcoming transit observations. GJ 436 is ideal for an SPI experiment because (1) escaped gas from its known rapidly evaporating hot Neptune could be funneled onto the star and (2) it displays a tentative SPI signal in existing, incomplete N V observations. The proposed experiment will complete these N V observations to constrain a model of modulation in N V flux resulting from a stellar hot spot induced by the planet. The results will provide evidence for or against hot spot SPIs producing the correlations observed in the MUSCLES Survey. Furthemore, the acquired data will establish a broader FUV baseline to constrain day-timescale variability and facular emission in FUV lines, needed for the interpretation of upcoming transit observations of GJ 436b. For this reason, we waive our proprietary rights to the data. Establishing GJ 436's baseline FUV variability and testing the hot spot hypothesis are only possible through the FUV capabilities of HST.

Ultrahigh resolution photographic films for X-ray/EUV/FUV astronomy

NASA Technical Reports Server (NTRS)

Hoover, Richard B.; Walker, Arthur B. C., Jr.; Deforest, Craig E.; Watts, Richard; Tarrio, Charles

1993-01-01

The quest for ultrahigh resolution full-disk images of the sun at soft X-ray/EUV/FUV wavelengths has increased the demand for photographic films with broad spectral sensitivity, high spatial resolution, and wide dynamic range. These requirements were made more stringent by the recent development of multilayer telescopes and coronagraphs capable of operating at normal incidence at soft X-ray/EUV wavelengths. Photographic films are the only detectors now available with the information storage capacity and dynamic range such as is required for recording images of the solar disk and corona simultaneously with sub arc second spatial resolution. During the Stanford/MSFC/LLNL Rocket X-Ray Spectroheliograph and Multi-Spectral Solar Telescope Array (MSSTA) programs, we utilized photographic films to obtain high resolution full-disk images of the sun at selected soft X-ray/EUV/FUV wavelengths. In order to calibrate our instrumentation for quantitative analysis of our solar data and to select the best emulsions and processing conditions for the MSSTA reflight, we recently tested several photographic films. These studies were carried out at the NIST SURF II synchrotron and the Stanford Synchrotron Radiation Laboratory. In this paper, we provide the results of those investigations.

Far-UV-induced dimeric photoproducts in short oligonucleotides: sequence effects.

PubMed

Douki, T; Zalizniak, T; Cadet, J

1997-08-01

Cyclobutane pyrimidine dimers and pyrimidine(6-4)pyrimidone adducts represent the two major classes of far-UV-induced DNA photoproducts. Because of the lack of appropriate detection methods for each individual photoproduct, little is known about the effect of the sequence on their formation. In the present work, the photoproduct distribution obtained upon exposure of a series of dinucleoside monophosphates to 254 nm light was determined. In the latter model compounds, the presence of a cytosine, located at either the 5'- or the 3'-side of a thymine moiety, led to the preferential formation of (6-4) adducts, whereas the cis-syn cyclobutane dimer was the main thymine-thymine photoproduct. In contrast, the yield of dimeric photoproducts, and particularly of (6-4) photoadducts, was very low upon irradiation of the cytosine-cytosine dinucleoside monophosphate. However, substitution of cytosine by uracil led to an increase in the yield of (6-4) photoproduct. It was also shown that the presence of a phosphate group at the 5'- end of a thymine-thymine dinucleoside monophosphate does not modify the photoproduct distribution. As an extension of the studies on dinucleoside monophosphates, the trinucleotide TpdCpT was used as a more relevant DNA model. The yields of formation of the thymine-cytosine and cytosine-thymine (6-4) photoproducts were in a 5:1 ratio, very close to the value obtained upon photolysis of the related dinucleoside monophosphates. The characterization of the two TpdCpT (6-4) adducts was based on 1H NMR, UV and mass spectroscopy analyses. Additional evidence for the structures was inferred from the analysis of the enzymatic digestion products of the (6-4) adducts of TpdCpT with phosphodiesterases. The latter enzymes were shown to induce the quantitative release of the photoproduct as a modified dinucleoside monophosphate in a highly sequence-specific manner.

Neutral atomic absorption lines and far-UV extinction: Possible implications for depletions and grain parameters

NASA Technical Reports Server (NTRS)

Welty, Daniel E.

1990-01-01

Researchers examine nine lines of sight within the Galaxy and one in the Large Magellanic Cloud (LMC) for which data on both neutral atomic absorption lines (Snow 1984; White 1986; Welty, Hobbs, and York 1989) and far UV extinction (Bless and Savage 1972; Jenkins, Savage, and Spitzer 1986) are available, in order to test the assumption that variations in gamma/alpha will cancel in taking ratios of the ionization balance equation, and to try to determine to what extent that assumption has affected the aforementioned studies of depletions and grain properties.

X ray, extreme and far ultraviolet optical thin films for space applications

NASA Technical Reports Server (NTRS)

Zukic, Muamer; Torr, Douglas G.; Kim, Jongmin

1993-01-01

Far and extreme ultraviolet optical thin film filters find many uses in space astronomy, space astrophysics, and space aeronomy. Spacebased spectrographs are used for studying emission and absorption features of the earth, planets, sun, stars, and the interstellar medium. Most of these spectrographs use transmission or reflection filters. This requirement has prompted a search for selective filtering coatings with high throughput in the FUV and EUV spectral region. Important progress toward the development of thin film filters with improved efficiency and stability has been made in recent years. The goal for this field is the minimization of absorption to get high throughput and enhancement of wavelength selection. The Optical Aeronomy Laboratory (OAL) at the University of Alabama in Huntsville has recently developed the technology to determine optical constants of bulk and film materials for wavelengths extending from x-rays (0.1 nm) to the FUV (200 nm), and several materials have been identified that were used for designs of various optical devices which previously have been restricted to space application in the visible and near infrared. A new design concept called the Pi-multilayer was introduced and applied to the design of optical coatings for wavelengths extending from x-rays to the FUV. Section 3 of this report explains the Pi-multilayer approach and demonstrates its application for the design and fabrication of the FUV coatings. Two layer Pi-stacks have been utilized for the design of reflection filters in the EUV wavelength range from 70 - 100 nm. In order to eliminate losses due to the low reflection of the imaging optics and increase throughput and out-of-band rejection of the EUV instrumentation we introduced a self-filtering camera concept. In the FUV region, MgF2 and LiF crystals are known to be birefringent. Transmission polarizers and quarterwave retarders made of MgF2 or LiF crystals are commercially available but the performances are poor. New

Multilayer thin film design for far ultraviolet polarizers using an induced transmission and absorption technique

NASA Technical Reports Server (NTRS)

Kim, Jongmin; Zukic, Muamer; Torr, Douglas G.

1993-01-01

An explanation of induced transmission for spectral regions excluding the far ultraviolet (FUV) is given to better understand how induced transmission and absorption can be used to design effective polarizers in the FUV spectral region. We achieve high s-polarization reflectance and a high degree of polarization (P equals (Rs-Rp)/(Rs+Rp)) by means of a MgF2/Al/MgF2 three layer structure on an opaque thick film of Al as the substrate. For example, our polarizer designed for the Lyman-alpha line (lambda equals 121.6 nm) has 87.95 percent reflectance for the s-polarization case and 0.43 percent for the p-polarization case, with a degree of polarization of 99.03 percent. If a double reflection polarizer is made with this design, it will have a degree of polarization of 99.99 percent and s-polarization throughput of 77.35 percent.

Efficient conversion of 3He(n,tp) and 10B(n, α7Li) reaction energies into far-ultraviolet radiation by noble gas excimers

NASA Astrophysics Data System (ADS)

Hughes, Patrick P.; Coplan, Michael A.; Thompson, Alan K.; Vest, Robert E.; Clark, Charles W.

2011-03-01

Previous work showed that the 3He(n , tp) reaction in a cell of 3He at atmospheric pressure generated tens of far-ultraviolet (FUV) photons per reacted neutron. Here we report amplification of that signal by factors of 1000 when noble gases are added to the cell. Calibrated filter-detector measurements show that this large signal is due to noble-gas excimer emissions, and that the nuclear reaction energy is converted to FUV radiation with efficiencies of up to 30 % . Our results have been placed on an absolute scale through calibrations at the NIST SURF III Synchrotron and Center for Neutron Research. We have also seen large neutron-induced FUV signals when the 3He gas in our system is replaced with a 10B film target; an experiment on substituting 3He with BF3 is underway. Our results suggest possibilities for high-efficiency, non-3He neutron detectors as an alternative to existing proportional counters.

The Lyman continuum escape fraction of low mass star-forming galaxies at z~1.

NASA Astrophysics Data System (ADS)

Rutkowski, Michael J.; Scarlata, Claudia; Haardt, Francesco; Siana, Brian D.; Rafelski, Marc; Henry, Alaina L.; Hayes, Matthew; Salvato, Mara; Pahl, Anthony; Mehta, Vihang; Beck, Melanie; Malkan, Matthew Arnold; Teplitz, Harry I.

2016-01-01

Star-forming galaxies (SFGs) in the high redshift universe (z>6) are believed to ionize neutral hydrogen in the intergalactic medium during the epoch of reionization. We tested this assumption by studying likely analogs of these SFGs in archival HST grism spectroscopy with GALEX UV and ground-based optical images at the redshift range in which we can directly measure the rest-frame Lyman continuum (λ<912Å, LyC) emission. We selected ~1400 SFGs for study on the presence of strong Hα emission and strongly selected against those SFGs whose GALEX FUV photometry could be contaminated by low redshift interlopers along the line of sight to produce a sample of ~600 z~1 SFGs. We made no unambiguous detection of escaping Lyman continuum radiation in individual galaxies in this sample, and stacked the individual non-detections in order to constrain the absolute Lyman continuum escape fraction, fesc<2% (3σ). We sub-divided this sample and stacked SFGs to measure upper limits to fesc with respect to stellar mass,luminosity and relative orientation. For z~1 high Hα equivalent width (EW>200Å) SFGs, we found for the first time an upper limit to fesc<9%. We discuss the implications of these limits for the ionizing emissivity of high redshift SFGs during the epoch of reionization. We conclude that reionization by SFGs is only marginally consistent with independent Planck observations of the CMB electron scattering opacity unless the LyC escape fraction of SFGs increases with redshift and an unobserved population of faint (MUV<-13 AB) SFGs contributes significantly to the UV background.

Exploratory Phase for Optimizing Lifetime Position 4 of the COS/FUV Detector

NASA Astrophysics Data System (ADS)

Roman-Duval, Julia; Indriolo, Nick; De Rosa, Gisella; Fox, Andrew; Oliveira, Cristina; Penton, Steve; Sahnow, David; Sonnentrucker, Paule; White, James

2018-05-01

The COS/FUV detector uses a microchannel plate, whose response (gain) decreases with usage, a process called gain-sag. To mitigate these gain-sag effects, COS/FUV science spectra are periodically moved to pristine locations of the detector, i.e. different lifetime positions (LP). Preparations for the move from LP3 to LP4 started with an exploratory phase between May and October 2016, while the LP4 move occurred on October 2, 2017. This ISR describes the LP4 exploratory phase, during which the feasibility of placing LP4 at -2.5'' below LP3 (-5'' below LP1) was examined, the effects of the LP4 move on the science quality and calibration accuracy of spectra were investigated, and the final location of LP4 (- 2.5'' below LP3) was determined. We describe in detail the strategy adopted for the LP4 exploratory phase to ensure that all potential issues were identified and resolved well in advance of the LP4 move.

A Far-ultraviolet Fluorescent Molecular Hydrogen Emission Map of the Milky Way Galaxy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jo, Young-Soo; Min, Kyoung-Wook; Seon, Kwang-Il

We present the far-ultraviolet (FUV) fluorescent molecular hydrogen (H{sub 2}) emission map of the Milky Way Galaxy obtained with FIMS/SPEAR covering ∼76% of the sky. The extinction-corrected intensity of the fluorescent H{sub 2} emission has a strong linear correlation with the well-known tracers of the cold interstellar medium (ISM), including color excess E(B–V) , neutral hydrogen column density N (H i), and H α emission. The all-sky H{sub 2} column density map was also obtained using a simple photodissociation region model and interstellar radiation fields derived from UV star catalogs. We estimated the fraction of H{sub 2} ( f {submore » H2}) and the gas-to-dust ratio (GDR) of the diffuse ISM. The f {sub H2} gradually increases from <1% at optically thin regions where E(B–V) < 0.1 to ∼50% for E(B–V)  = 3. The estimated GDR is ∼5.1 × 10{sup 21} atoms cm{sup −2} mag{sup −1}, in agreement with the standard value of 5.8 × 10{sup 21} atoms cm{sup −2} mag{sup −1}.« less

The Amazing COS FUV (1320 - 1460 A) Spectrum of (lambda) Vel (K4Ib-II)

NASA Technical Reports Server (NTRS)

Carpenter, Kenneth

2010-01-01

The FUV spectrum (1320-1460 A) of the K4 lb-11 supergiant (lambda) Vel was observed with the Cosmic Origins Spectrograph (COS) on HST, as part of the Ayres and Redfield Cycle 17 SNAP program "SNAPing Coronal Iron". This spectrum covers a region not previously recorded in (lambda) Vel at high resolution and, in a mere 20 minutes of exposure, reveals a treasure trove of information. It shows a wide variety of strong emission lines, superposed on a bright continuum, with contributions from both atomic and molecular species. Multiple absorptions, including numerous Ni II and Fe II lines, are visible over this continuum, which is likely generated in the chromosphere of the star. Evidence of the stellar wind is seen in the P Cygni profiles of the CII lines near 1335 A and the results of fluorescence processes are visible throughout the region. The spectrum has remarkable similarities to that of (alpha) Boo (K1.5 III), but significant differences as well, including substantial FUV continuum emission, reminiscent of the M2 Iab supergiant (alpha) Ori, but minus the CO fundamental absorption bands seen in the spectrum of the latter star. However, fluoresced CO emission is present, as in the K-giant stars (alpha) Boo and (alpha) Tau (K5 III). The presence of hot plasma in the atmosphere of the star, indicated by previous GHRS observations of Si III] and C III] lines near 1900 A and FUSE observations of O VI 1032 A, is further confirmed by the detection in this COS spectrum of the Si IV UV 1 lines near 1400 A, though both lines are contaminated by overlying fluorescent H2 emission. We present the details of this spectrum, in comparison with stars of similar temperature or luminosity and discuss the implications for the structure of, and the radiative processes active in, the outer atmospheres of these stars.

COS FUV Recovery after Anomalous Shutdown

NASA Astrophysics Data System (ADS)

Wheeler, Thomas

2012-10-01

This proposal consists of the steps for turning on and ramping up the COS FUV high voltage in a conservative manner after a HV anomalous shutdown by executing a "reduced set" of visits from Cycle 19 Proposal 12810. The nature of the shutdown, i.e., over-light, HV current transient {"crackle"}, ion feedback {induced by a high energy particle}, or field emission {possibly caused by dust or other particulate on the QE grid or other close-by structure or hardware}, and the value of the commanded HV at the time of the shutdown will determine what visits are executed. Because of gain sag, commanded HV settings updates may be required. First, prior to execution of this proposal or selected visits from this proposal, all preliminary steps should be exercised to gather the necessary diagnostic data, e.g., science data evaluation {if a science exposure was in progress and the science data is available}, memory dumps {DCE, EXEC RAM, and possibly the CS BUFFER}, engineering telemetry, or other information that might provide insight as to the nature of the shutdown and estimated count rate. The complete step-by-step procedure is detailed in the Observing Description, but in summary, the following is done:Day 01 activities, visits 01-07, contain both QE grid off and on HV ramping to HVLow {100/100} with diagnostics {DCE dumps} and darks to exclude QE grid involvement in the shutdown. Subsequent to day 01, all HV ramping will be with the QE grid on with the same diagnostics and exposures. All days end with the setting of COS event flag 3 to prevent any FUV HV commanding.Time is allotted for cognizant detector and COS instrument scientist and engineers to examine data dumps, science exposures, and engineering telemetry. If all is well, the go-ahead will be given to clear flag 3 for the next day's visits.This proposal is modeled after the Cycle 19 Proposal 12718.

COS FUV Recovery after Anomalous Shutdown

NASA Astrophysics Data System (ADS)

Wheeler, Thomas

2013-10-01

This proposal consists of the steps for turning on and ramping up the COS FUV high voltage in a safe and conservative manner after a HV anomalous shutdown by executing a "reduced set" of visits from Cycle 19 Proposal 12810. The nature of the shutdown, i.e., over-light, HV current transient {"crackle"}, ion feedback {induced by a high energy particle}, or field emission {possibly caused by dust or other particulate on the QE grid or other close-by structure or hardware}, and the value of the commanded HV at the time of the shutdown will determine what visits are executed. Because of gain sag, commanded HV settings updates may be required. First, prior to execution of this proposal or selected visits from this proposal, all preliminary steps should be exercised to gather the necessary diagnostic data, e.g., science data evaluation {if a science exposure was in progress and the science data is available}, memory dumps {DCE, EXEC RAM, and possibly the CS BUFFER}, engineering telemetry, or other information that might provide insight as to the nature of the shutdown and estimated count rate. The complete step-by-step procedure is detailed in the Observing Description, but in summary, the following is done:Day 01 activities, visits 01-07, contain both QE grid off and on HV ramping to HVLow {100/100} with diagnostics {DCE dumps} and darks to exclude QE grid involvement in the shutdown. Subsequent to day 01, all HV ramping will be with the QE grid on with the same diagnostics and exposures. All days end with the setting of COS event flag 3 to prevent any FUV HV commanding.Time is allotted for cognizant detector and COS instrument scientist and engineers to examine data dumps, science exposures, and engineering telemetry. If all is well, the go-ahead will be given to clear flag 3 for the next day's visits.This proposal is modeled after the Cycle 20 Proposal 13129.

Far from thunderstorm UV transient events in the atmosphere measured by Vernov satellite

NASA Astrophysics Data System (ADS)

Morozenko, Violetta; Klimov, Pavel; Khrenov, Boris; Gali, Garipov; Margarita, Kaznacheeva; Mikhail, Panasyuk; Sergei, Svertilov; Robert, Holzworth

2016-04-01

The steady self-contained classification of events such as sprites, elves, blue jets emerged for the period of transient luminous events (TLE) observation. In accordance with TLE origin theories the presence of the thunderstorm region where the lightnings with the large peak current generating in is necessary. However, some far-from-thunderstorm region events were also detected and revealed to us another TLE generating mechanisms. For the discovering of the TLE nature the Universitetsky-Tatiana-2 and Vernov satellites were equipped with ultraviolet (240-400 nm) and red-infrared ( >610 nm) detectors. In both detector it was carried out regardless the lightnings with the guidance by the flashes in the UV wavelength where lightning's emitting is quite faint. The lowered threshold on the Vernov satellite allowed to select the great amount of TLE with the numerous far-from-thunderstorm region events examples. such events were not conjuncted with lightning activity measured by global lightning location network (WWLLN) on the large area of approximately 107 km2 for 30 minutes before and after the time of registration. The characteristic features of this type of event are: the absence of significant signal in the red-infrared detector's channel; a relatively small number of photons (less than 5 ṡ 1021). A large number of without lightning flash were detected at high latitudes over the ocean (30°S - 60°S). Lightning activity in the magnetic conjugate point also was analyzed. The relationship of far-from-thunderstorm region events with the specific lightning discharges didn't confirmed. Far-from-thunderstorm events - a new type of transient phenomena in the upper atmosphere is not associated with the thunderstorm activity. The mechanism of such discharges is not clear, though it was accumulated a sufficient amount of experimental facts of the existence of such flashes. According to the data of Vernov satellite the temporal profile, duration, location with earth

GAMA/H-ATLAS: the ultraviolet spectral slope and obscuration in galaxies

NASA Astrophysics Data System (ADS)

Wijesinghe, D. B.; da Cunha, E.; Hopkins, A. M.; Dunne, L.; Sharp, R.; Gunawardhana, M.; Brough, S.; Sadler, E. M.; Driver, S.; Baldry, I.; Bamford, S.; Liske, J.; Loveday, J.; Norberg, P.; Peacock, J.; Popescu, C. C.; Tuffs, R.; Andrae, E.; Auld, R.; Baes, M.; Bland-Hawthorn, J.; Buttiglione, S.; Cava, A.; Cameron, E.; Conselice, C. J.; Cooray, A.; Croom, S.; Dariush, A.; Dezotti, G.; Dye, S.; Eales, S.; Frenk, C.; Fritz, J.; Hill, D.; Hopwood, R.; Ibar, E.; Ivison, R.; Jarvis, M.; Jones, D. H.; van Kampen, E.; Kelvin, L.; Kuijken, K.; Maddox, S. J.; Madore, B.; Michałowski, M. J.; Nichol, B.; Parkinson, H.; Pascale, E.; Pimbblet, K. A.; Pohlen, M.; Prescott, M.; Rhodighiero, G.; Robotham, A. S. G.; Rigby, E. E.; Seibert, M.; Sergeant, S.; Smith, D. J. B.; Temi, P.; Sutherland, W.; Taylor, E.; Thomas, D.; van der Werf, P.

2011-08-01

We use multiwavelength data from the Galaxy And Mass Assembly (GAMA) and Herschel-ATLAS (H-ATLAS) surveys to compare the relationship between various dust obscuration measures in galaxies. We explore the connections between the ultraviolet (UV) spectral slope, β, the Balmer decrement and the far-infrared (FIR) to 150 nm far-ultraviolet (FUV) luminosity ratio. We explore trends with galaxy mass, star formation rate (SFR) and redshift in order to identify possible systematics in these various measures. We reiterate the finding of other authors that there is a large scatter between the Balmer decrement and the β parameter, and that β may be poorly constrained when derived from only two broad passbands in the UV. We also emphasize that FUV-derived SFRs, corrected for dust obscuration using β, will be overestimated unless a modified relation between β and the attenuation factor is used. Even in the optimum case, the resulting SFRs have a significant scatter, well over an order of magnitude. While there is a stronger correlation between the IR-to-FUV luminosity ratio and β parameter than with the Balmer decrement, neither of these correlations are particularly tight, and dust corrections based on β for high-redshift galaxy SFRs must be treated with caution. We conclude with a description of the extent to which the different obscuration measures are consistent with each other as well as the effects of including other galactic properties on these correlations.

In Charon's Shadow: Analysis of the UV Solar Occultation from New Horizons

NASA Astrophysics Data System (ADS)

Kammer, Joshua A.; Stern, S. A.; Weaver, H. A.; Young, L. A.; Ennico, K. A.; Olkin, C. B.; Gladstone, G. R.; Summers, M. E.; Greathouse, T. K.; Retherford, K. D.; Versteeg, M. H.; Parker, J. W.; Steffl, A. J.; Schindhelm, E.; Strobel, D. F.; Linscott, I. R.; Hinson, D. P.; Tyler, G. L.; Woods, W. W.

2015-11-01

Observations of Charon, Pluto's largest moon, have so far yielded no evidence for a substantial atmosphere. However, during the flyby of New Horizons through the Pluto-Charon system, the Alice ultraviolet spectrograph successfully acquired the most sensitive measurements to date during an occultation of the sun as New Horizons passed through Charon's shadow. These observations include wavelength coverage in the extreme- and far-ultraviolet (EUV and FUV) from 52 nm to 187 nm. We will present these results from Alice, and discuss their implications for an atmosphere on Charon.This work was supported by NASA's New Horizons project.

Interference Thin Films for Spectral Filtering, Polarizing, Phase Retarding, and Intensity Splitting of FUV Radiation.

NASA Astrophysics Data System (ADS)

Kim, Jongmin

The development of thin film technology for the far ultraviolet (FUV: 120~220 nm) has not progressed as rapidly as in the visible and infrared regions because substrate and thin film materials exhibit absorption characteristics that complicate the design process. Mathematically, these absorbing materials can be treated in the same manner as non-absorbing materials if a complex representation of the optical constants is used. Realization of higher throughput can be achieved by operating in a reflective rather than a transmissive mode. The spectral filter II -stack design method obtains a high reflectance by minimizing absorptance in the high refractive index layer while maintaining the constructive interference between reflected waves at the boundary of HL pairs. Reflective polarizers are designed by inducing transmission and absorption of the p-polarized light. Utilizing a MgF_2/Al/MgF _2 three layer structure on a thick Al layer as a substrate, high s-polarization reflectance (>88%) and a high degree of polarization (>99%) are obtained. Out-of-band rejection in the spectral filter and the degree of polarization in the polarizer are significantly improved by combining multiple reflectors in tandem. The high-low absorbing material boundaries in the MgF_2/Al/MgF_2 structure are also useful for obtaining phase retardance between s and p-polarized reflected fields. Two equations established by the ideal quarterwave retarder (QWR) requirement and electric field relations are used to determine the MgF_2 layer thicknesses to achieve excellent QWR performances. Calculated results show that a high reflectance for both polarizations (>80%) and almost 90^circ of phase retardance are possible. Discrepancies between the designed and measured polarizer performance are mainly caused by Al layer oxidation during fabrication in a conventional high vacuum chamber. XPS depth profiling is used to analyze the oxidation and the results show that oxidized layer thicknesses are greater

The UV Survey Mission Concept, CETUS

NASA Astrophysics Data System (ADS)

Heap, Sara; and the CETUS Team

2018-01-01

In March 2017, NASA selected CETUS for study of a Probe-class mission concept. W. Danchi is the CETUS PI, and S. Heap is the Science PI. CETUS is primarily a UV survey telescope to complement survey telescopes of the 2020’s including E-ROSITA, Subaru Hyper Suprime Cam and Prime-Focus Spectrograph, WFIRST, and the Square Kilometer Array. CETUS comprises a 1.5-m wide-field telescope and three science instruments: a wide-field (1045” on a side) far-UV and near-UV camera; a similarly wide-field near-UV multi-object spectrograph utilizing a next-generation micro-shutter array; and a single-object spectrograph with options of spectral region (far-UV or near-UV) and spectral resolving power (2,000 or 40,000). The survey instruments will operate simultaneously thereby producing wide-field images in the near-UV and far-UV and a spectrogram containing near-UV spectra of up to 100 sources free of spectral overlap and astronomical background. ln concert with other survey telescopes, CETUS will focus on understanding galaxy evolution at cosmic noon (z~1-2).

FUV Detection of the Primary Star of eta Carinae

NASA Astrophysics Data System (ADS)

Davidson, K.; Smith, N.

2006-06-01

Using FUSE data, Iping et al (2005, ApJ 633, L37) report a direct detection of the elusive hot companion of eta Car. We argue, however, that much of the observed emission represents the primary star, with no proof that any of it comes from a secondary star. The hypothetical companion should dominate the ionizing radiation below 912 A, but this is not true for wavelengths around 1100 A observed with FUSE. Moreover, since a companion's UV would be partially reprocessed by the primary star's wind, any detection is likely to be ambiguous.The non-spherical primary wind allows production of strong UV radiation at low latitudes (Smith et al 2003, ApJ 586, 432), an effect that spherical models don't include. The N II 1085 feature, the relatively slow wind velocities seen by FUSE, and other details are characteristic of the primary wind, not the secondary. Zanella et al. (1984, A&A 137, 79) suggested that eta Car's far UV disappears during a spectroscopic event due to a shell ejection. The FUSE observations may be regarded as confirmation of that conjecture, which made no reference to a secondary star. The 2003 spectroscopic event was probably a mass ejection or a wind-disturbance episode, not merely an eclipse as assumed by Iping et al. A hot companion star seems likely to account for the ionizing UV and the X-ray variability, but the FUSE data do not confirm its existence.

The U.S. Rosetta Project at Its First Science Target: Asteroid (2867) Steins, 2008

NASA Technical Reports Server (NTRS)

Alexander, C.; Sweetnam, D.; Gulkis, S.; Weissman, P.; Holmes, D.; Parker, J.; Burch, J.; Goldstein, R.; Mokashi, P.; Fuselier, S.;

Improvements to the Hubble Space Telescope COS/FUV Wavelength Calibration at Lifetime Position 4

NASA Astrophysics Data System (ADS)

Plesha, Rachel; Ake, Thomas B.; De Rosa, Gisella; Oliveira, Cristina M.; Penton, Steven V.; Snyder, Elaine M.

2018-06-01

The Cosmic Origins Spectrograph (COS) was installed on the Hubble Space Telescope in 2009, and the FUV detector is currently operating at the 4th lifetime position (LP4). The COS team at the Space Telescope Science Institute has been improving the wavelength calibration of the FUV channel at each lifetime position. For the LP4 solution we obtained special calibration data as well as new lamp spectra to update the lamp template used at LP4 with the goal of achieving a wavelength calibration accuracy of ± 3 pixels. Additionally, we derived a new solution for the G130M/1222 cenwave which we expect to be more frequently used at this lifetime position due to the COS2025 policy in place on the other G130M settings. Here we present the results and methodology behind the wavelength calibration solutions at LP4.

Far Ultraviolet Spectroscopy of Saturn's Icy Moon Rhea

NASA Astrophysics Data System (ADS)

Elowitz, Mark; Hendrix, Amanda; Mason, Nigel J.; Sivaraman, Bhalamurugan

2018-01-01

We present an analysis of spatially resolved, far-UV reflectance spectra of Saturn’s icy satellite Rhea, collected by the Cassini Ultraviolet Imaging Spectrograph (UVIS). In recent years ultraviolet spectroscopy has become an important tool for analysing the icy satellites of the outer solar system (1Hendrix & Hansen, 2008). Far-UV spectroscopy provides unique information about the molecular structure and electronic transitions of chemical species. Many molecules that are suspected to be present in the icy surfaces of moons in the outer solar system have broad absorption features due to electronic transitions that occur in the far-UV portion of the spectrum. The studies show that Rhea, like the other icy satellites of the Saturnian system are dominated by water-ice as evident by the 165-nm absorption edge, with minor UV absorbing contaminants. Far-UV spectra of several Saturnian icy satellites, including Rhea and Dione, show an unexplained weak absorption feature centered near 184 nm. To carry out the geochemical survey of Rhea’s surface, the UVIS observations are compared with vacuum-UV spectra of thin-ice samples measured in laboratory experiments. Thin film laboratory spectra of water-ice and other molecular compounds in the solid phase were collected at near-vacuum conditions and temperatures identical to those at the surface of Rhea. Comparison between the observed far-UV spectra of Rhea’s surface ice and modelled spectra based on laboratory absorption measurements of different non-water-ice compounds show that two possible chemical compounds could explain the 184-nm absorption feature. The two molecular compounds include simple chlorine molecules and hydrazine monohydrate. Attempts to explain the source(s) of these compounds on Rhea and the scientific implications of their possible discovery will be summarized.[1] Hendrix, A. R. & Hansen, C. J. (2008). Icarus, 193, pp. 323-333.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Waszczak, Adam; Kulkarni, Shrinivas R.; Ofek, Eran O., E-mail: waszczak@caltech.edu

We present ultraviolet (UV) photometry (near-UV (NUV) band, 180–280 nm) of 405 asteroids observed serendipitously by GALEX from 2003 to 2012. All asteroids in this sample were detected by GALEX at least twice. Unambiguous visible-color-based taxonomic labels (C type versus S type) exist for 315 of these asteroids; of these, thermal-infrared-based diameters are available for 245. We derive NUV − V color using two independent models to predict the visual magnitude V at each NUV-detection epoch. Both V models produce NUV − V distributions in which the S types are redder than C types with more than 8σ confidence. Thismore » confirms that the S types’ redder spectral slopes in the visible remain redder than the C types’ into the NUV, this redness being consistent with absorption by silica-containing rocks. The GALEX asteroid data confirm earlier results from the International Ultraviolet Explorer, which two decades ago produced the only other sizeable set of UV asteroid photometry. The GALEX-derived NUV − V data also agree with previously published Hubble Space Telescope (HST) UV observations of asteroids 21 Lutetia and 1 Ceres. Both the HST and GALEX data indicate that NUV band is less useful than u band for distinguishing subgroups within the greater population of visible-color-defined C types (notably, M types and G types)« less

FIREBall, CHaS, and the diffuse universe

NASA Astrophysics Data System (ADS)

Hamden, Erika Tobiason

The diffuse universe, consisting of baryons that have not yet collapsed into structures such as stars, galaxies, etc., has not been well studied. While the intergalactic and circumgalactic mediums (IGM & CGM) may contain 30-40% of the baryons in the universe, this low density gas is difficult to observe. Yet it is likely a key driver of the evolution of galaxies and star formation through cosmic time. The IGM provides a reservoir of gas that can be used for star formation, if it is able to accrete onto a galaxy. The CGM bridges the IGM and the galaxy itself, as a region of both inflows from the IGM and outflows from galactic star formation and feedback. The diffuse interstellar medium (ISM) gas and dust in the galaxy itself may also be affected by the CGM of the galaxy. Careful observations of the ISM of our own Galaxy may provide evidence of interaction with the CGM. These three regions of low density, the IGM, CGM, and ISM, are arbitrary divisions of a continuous flow of low density material into and out of galaxies. My thesis focuses on observations of this low density material using existing telescopes as well as on the development of technology and instruments that will increase the sensitivity of future missions. I used data from the Galaxy Evolution Explorer (GALEX) to create an all sky map of the diffuse Galactic far ultraviolet (FUV) background, probing the ISM of our own galaxy and comparing to other Galactic all sky maps. The FUV background is primarily due to dust scattered starlight from bright stars in the Galactic plane, and the changing intensity across the sky can be used to characterize dust scattering asymmetry and albedo. We measure a consistent low level non-scattered isotropic component to the diffuse FUV, which may be due in small part to an extragalactic component. There are also several regions of unusually high FUV intensity given other Galactic quantities. Such regions may be the location of interactions between Galactic super-bubbles and

Panchromatic properties of 99000 galaxies detected by SDSS, and (some by) ROSAT, GALEX, 2MASS, IRAS, GB6, FIRST, NVSS and WENSS surveys

NASA Astrophysics Data System (ADS)

Obrić, M.; Ivezić, Ž.; Best, P. N.; Lupton, R. H.; Tremonti, C.; Brinchmann, J.; Agüeros, M. A.; Knapp, G. R.; Gunn, J. E.; Rockosi, C. M.; Schlegel, D.; Finkbeiner, D.; Gaćeša, M.; Smolčić, V.; Anderson, S. F.; Voges, W.; Jurić, M.; Siverd, R. J.; Steinhardt, W.; Jagoda, A. S.; Blanton, M. R.; Schneider, D. P.

2006-08-01

We discuss the panchromatic properties of 99088 galaxies selected from the Sloan Digital Sky Survey (SDSS) Data Release 1 `main' spectroscopic sample (a flux-limited sample for 1360deg2). These galaxies are positionally matched to sources detected by ROSAT, Galaxy Evolution Explorer (GALEX), two-Micron All-Sky Survey (2MASS), Infrared Astronomical Satellite (IRAS), Green Bank GB6 survey (GB6), Faint Images of the Radio Sky at Twenty-centimetres (FIRST), NRAO VLA Sky Survey (NVSS) and Westerbork Northern Sky Survey (WENSS). The matching fraction varies from <1 per cent for ROSAT and GB6 to ~40 per cent for GALEX and 2MASS. In addition to its size, the advantages of this sample are well-controlled selection effects, faint flux limits and the wealth of measured parameters, including accurate X-ray to radio photometry, angular sizes and optical spectra. We find strong correlations between the detection fraction at other wavelengths and optical properties such as flux, colours and emission-line strengths. For example, ~2/3 of SDSS `main' galaxies classified as active galactic nucleus (AGN) using emission-line strengths are detected by 2MASS, while the corresponding fraction for star-forming galaxies (SFs) is only ~1/10. Similarly, over 90 per cent of galaxies detected by IRAS display strong emission lines in their optical spectra, compared to ~50 per cent for the whole SDSS sample. Using GALEX, SDSS and 2MASS data, we construct the ultraviolet-infrared (UV-IR) broad-band spectral energy distributions for various types of galaxies, and find that they form a nearly one-parameter family. For example, the SDSS u- and r-band data, supplemented with redshift, can be used to `predict' K-band magnitudes measured by 2MASS with an rms scatter of only 0.2mag. When a dust content estimate determined from SDSS spectra with the aid of models is also utilized, this scatter decreases to 0.1mag and can be fully accounted for by measurement uncertainties. We demonstrate that this

UVMag: Space UV and visible spectropolarimetry

NASA Astrophysics Data System (ADS)

Pertenais, Martin; Neiner, Coralie; Parès, Laurent P.; Petit, Pascal; Snik, Frans; van Harten, Gerard

2014-07-01

UVMag is a project of a space mission equipped with a high-resolution spectropolarimeter working in the UV and visible range. This M-size mission will be proposed to ESA at its M4 call. The main goal of UVMag is to measure the magnetic fields, winds and environment of all types of stars to reach a better understanding of stellar formation and evolution and of the impact of stellar environment on the surrounding planets. The groundbreaking combination of UV and visible spectropolarimetric observations will allow the scientists to study the stellar surface and its environment simultaneously. The instrumental challenge for this mission is to design a high-resolution space spectropolarimeter measuring the full- Stokes vector of the observed star in a huge spectral domain from 117 nm to 870 nm. This spectral range is the main difficulty because of the dispersion of the optical elements and of birefringence issues in the FUV. As the instrument will be launched into space, the polarimetric module has to be robust and therefore use if possible only static elements. This article presents the different design possibilities for the polarimeter at this point of the project.

A sample of [C II] clouds tracing dense clouds in weak FUV fields observed by Herschel

NASA Astrophysics Data System (ADS)

Pineda, J. L.; Velusamy, T.; Langer, W. D.; Goldsmith, P. F.; Li, D.; Yorke, H. W.

2010-10-01

The [C ii] fine-structure line at 158 μm is an excellent tracer of the warm diffuse gas in the ISM and the interfaces between molecular clouds and their surrounding atomic and ionized envelopes. Here we present the initial results from Galactic observations of terahertz C+ (GOT C+), a Herschel key project devoted to studying the [C ii] emission in the Galactic plane using the HIFI instrument. We used the [C ii] emission, together with observations of CO, as a probe to understand the effects of newly formed stars on their interstellar environment and characterize the physical and chemical state of the star-forming gas. We collected data along 16 lines-of-sight passing near star-forming regions in the inner Galaxy near longitudes 330° and 20°. We identified fifty-eight [C ii] components that are associated with high-column density molecular clouds as traced by 13CO emission. We combined [C ii], 12CO, and 13CO observations to derive the physical conditions of the [C ii]-emitting regions in our sample of high-column density clouds based on comparing results from a grid of photon dominated region (PDR) models. From this unbiased sample, our results suggest that most of the [C ii] emission originates in clouds with H2 volume densities between 103.5 and 105.5 cm-3 and weak FUV strength (χ0 = 1-10). We find two regions where our analysis suggest high densities >105 cm-3 and strong FUV fields (χ0 = 104-106), likely associated with massive star formation. We suggest that [C ii] emission in conjunction with CO isotopes is a good tool for differentiating regions of massive star formation (high densities/strong FUV fields) and regions that are distant from massive stars (lower densities/weaker FUV fields) along the line-of-sight. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.

FULVUE: Far Ultraviolet Universal Explorer

NASA Astrophysics Data System (ADS)

White, David L.; Cross, Eugene W.

1997-10-01

This is a concept study for a proposal to NASA/GSFC for a medium class Explorer Mission. It is designed to replace a prior SBIR Phase I design for NASA/MSFC for a Lunar far-UV survey telescope done in 1994 - 1995 for the Pathfinder Program (by the authors for I.S.E., under M. E. Nein, MSFC). A full investigation by project scientist D. L. White as to the most desirable mission science for a Lunar-based UV telescope, resulted in the decision to do a universal survey of the most interesting lines in the Lyman alpha forest, especially the O VI doublet lines around 103.2/103.8 nm. A telescope was designed by the authors incorporating a multiple instrument pod (MEDUSA), and a unique optical train featuring a selectable element secondary mirror module, with a special high resolution mode debuting a new optical design, all by chief optical engineer E. W. Cross. Special thanks go to chief spacecraft engineer T. L. Kessler for all packaging and integration of the telescope, its attendant systems, and the entire mission, including the launch interface and all presentations. In this incarnation, the basic concept has been converted by D. L. White into a free flyer designed for at least a LEO. In reconfiguring the original concept in the order to accomplish the original mission science goals, it has been necessary to take a fresh approach in order to fit the largest feasible Explorer Class Fairing (10L). In addition, the reconsideration of the mission science and the performance level available from the prior mission's optics, the authors decided to push the limits of the possible in the pursuit of excellence and choose two exceptional optical designs, augment them, and integrate them into the same limited envelope, while not sacrificing performance, communications, power, control, or serviceability. This we have kept close to focus throughout our pursuit of the mission science, which we hold foremost. We see a great need to bring the lessons learned at other portions of the

The Herschel-PACS Legacy of Low-mass Protostars: The Properties of Warm and Hot Gas Components and Their Origin in Far-UV Illuminated Shocks

NASA Astrophysics Data System (ADS)

Karska, Agata; Kaufman, Michael J.; Kristensen, Lars E.; van Dishoeck, Ewine F.; Herczeg, Gregory J.; Mottram, Joseph C.; Tychoniec, Łukasz; Lindberg, Johan E.; Evans, Neal J., II; Green, Joel D.; Yang, Yao-Lun; Gusdorf, Antoine; Itrich, Dominika; Siódmiak, Natasza

2018-04-01

Recent observations from Herschel allow the identification of important mechanisms responsible both for the heating of the gas that surrounds low-mass protostars and for its subsequent cooling in the far-infrared. Shocks are routinely invoked to reproduce some properties of the far-IR spectra, but standard models fail to reproduce the emission from key molecules, e.g., H2O. Here, we present the Herschel Photodetector Array Camera and Spectrometer (PACS) far-IR spectroscopy of 90 embedded low-mass protostars (Class 0/I). The Herschel-PACS spectral maps, covering ∼55–210 μm with a field of view of ∼50″, are used to quantify the gas excitation conditions and spatial extent using rotational transitions of H2O, high-J CO, and OH, as well as [O I] and [C II]. We confirm that a warm (∼300 K) CO reservoir is ubiquitous and that a hotter component (760 ± 170 K) is frequently detected around protostars. The line emission is extended beyond ∼1000 au spatial scales in 40/90 objects, typically in molecular tracers in Class 0 and atomic tracers in Class I objects. High-velocity emission (≳90 km s‑1) is detected in only 10 sources in the [O I] line, suggesting that the bulk of [O I] arises from gas that is moving slower than typical jets. Line flux ratios show an excellent agreement with models of C-shocks illuminated by ultraviolet (UV) photons for pre-shock densities of ∼105 cm‑3 and UV fields 0.1–10 times the interstellar value. The far-IR molecular and atomic lines are a unique diagnostic of feedback from UV emission and shocks in envelopes of deeply embedded protostars.

Sensitive far uv spectrograph with a multispectral element microchannel plate detector for rocket-borne astronomy.

PubMed

Weiser, H; Vitz, R C; Moos, H W; Weinstein, A

1976-12-01

An evacuated high transmission prism spectrograph using a microchannel plate detection system with resistive strip readout was flown behind a precision pointing telescope on a sounding rocket. The construction, preparation, flight performance, and calibration stability of the system are discussed. Despite the adverse environmental conditions associated with sounding rocket flights, the microchannel detector system performed well. Far uv spectra (1160-1750 A) of stellar and planetary objects were obtained; spectral features with fluxes as low as 0.06 photons cm(-2) sec(-1) were detectable. This was achieved by operating the plates at lower than normal gains, using sensitive pulse counting electronics with both upper and lower limit discriminators, and maintaining the spectrograph and detector at a pressure of ~10(-6) Torr until reaching altitude.

The comparative effect of FUV, EUV and X-ray disc photoevaporation on gas giant separations

NASA Astrophysics Data System (ADS)

Jennings, Jeff; Ercolano, Barbara; Rosotti, Giovanni P.

2018-04-01

Gas giants' early (≲ 5 Myr) orbital evolution occurs in a disc losing mass in part to photoevaporation driven by high energy irradiance from the host star. This process may ultimately overcome viscous accretion to disperse the disc and halt migrating giants by starving their orbits of gas, imprinting on giant planet separations in evolved systems. Inversion of this distribution could then give insight into whether stellar FUV, EUV or X-ray flux dominates photoevaporation, constraining planet formation and disc evolution models. We use a 1D hydrodynamic code in population syntheses for gas giants undergoing Type II migration in a viscously evolving disc subject to either a primarily FUV, EUV or X-ray flux from a pre-solar T Tauri star. The photoevaporative mass loss profile's unique peak location and width in each energetic regime produces characteristic features in the distribution of giant separations: a severe dearth of ≲ 2 MJ planets interior to 5 AU in the FUV scenario, a sharp concentration of ≲ 3 MJ planets between ≈1.5 - 2 AU in the EUV case, and a relative abundance of ≈2 - 3.5 MJ giants interior to 0.5 AU in the X-ray model. These features do not resemble the observational sample of gas giants with mass constraints, though our results do show some weaker qualitative similarities. We thus assess how the differing photoevaporative profiles interact with migrating giants and address the effects of large model uncertainties as a step to better connect disc models with trends in the exoplanet population.

The comparative effect of FUV, EUV and X-ray disc photoevaporation on gas giant separations

NASA Astrophysics Data System (ADS)

Jennings, Jeff; Ercolano, Barbara; Rosotti, Giovanni P.

2018-07-01

Gas giants' early (≲5 Myr) orbital evolution occurs in a disc losing mass in part to photoevaporation driven by high energy irradiance from the host star. This process may ultimately overcome viscous accretion to disperse the disc and halt migrating giants by starving their orbits of gas, imprinting on giant planet separations in evolved systems. Inversion of this distribution could then give insight into whether the stellar FUV, EUV or X-ray flux dominates photoevaporation, constraining planet formation and disc evolution models. We use a 1D hydrodynamic code in population syntheses for gas giants undergoing Type II migration in a viscously evolving disc subject to either a primarily FUV, EUV or X-ray flux from a pre-solar T Tauri star. The photoevaporative mass loss profile's unique peak location and width in each energetic regime produces characteristic features in the distribution of giant separations: a severe dearth of ≲2 MJ planets interior to 5 au in the FUV scenario, a sharp concentration of ≲3 MJ planets between ≈1.5-2 au in the EUV case and a relative abundance of ≈2-3.5 MJ giants interior to 0.5 au in the X-ray model. These features do not resemble the observational sample of gas giants with mass constraints, although our results do show some weaker qualitative similarities. We thus assess how the differing photoevaporative profiles interact with migrating giants and address the effects of large model uncertainties as a step to better connect disc models with trends in the exoplanet population.

Results of the IRIS UV Burst Survey, Part I: Active Regions Tracked Limb to Limb

NASA Astrophysics Data System (ADS)

Madsen, C. A.; DeLuca, E.

2017-12-01

We present results from the first phase of an effort to thoroughly characterize UV bursts within the Interface Region Imaging Spectrograph (IRIS) data catalogue. The observational signatures of these phenomena include dramatically intensified and broadened NUV/FUV emission line profiles with absorption features from cool metallic ions. These properties suggest that UV bursts originate from plasma at transition region temperatures (≥ 80,000 K) which is deeply embedded in the cool lower chromosphere ( 5,000 K). Rigorously characterizing the energetic and dynamical properties of UV bursts is crucial since they have considerable potential to heat active region chromospheres and could provide critical constraints for models of magnetic reconnection in these regions. The survey first focuses on IRIS observations of active regions tracked from limb to limb. All observations consist of large field-of-view raster scans of 320 or 400 steps each, which allow for widespread detection of many burst profiles at the expense of having limited short-term time evolution information. We detect bursts efficiently by applying a semi-automated single-Gaussian fitting technique to Si IV 1393.8 Å emission profiles that isolates the distinct burst population in a 4-D parameter space. The robust sample of NUV/FUV burst spectra allows for precise constraints of properties critical for modeling reconnection in the chromosphere, including outflow kinetic energy, density estimates from intensity ratios of Si IV 1402.8 Å and O IV 1401.2 Å emission lines, and coincident measures of emission in other wavelengths. We also track burst properties throughout the lifetimes of their host active regions, noting changes in detection rate and preferential location as the active regions evolve. Finally, the tracked active region observations provide a unique opportunity to investigate line-of-sight effects on observed UV burst spectral properties, particularly the strength of Ni II 1393.3 Å absorption

Probing the Initial Mass Function in Extended Ultraviolet (XUV) Disks

NASA Astrophysics Data System (ADS)

Koda, Jin

2012-01-01

"The GALEX UV satellite discovered tantalizing evidence of star formation (SF) far beyond the optical edge of galactic disks (i.e. extended UV disk, or XUV disk). This discovery provides a new opportunity for studying SF in the exceedingly low-density environment (˜1/10 of typical SF density), spurring intense debate on the universality of the initial mass function (IMF) in such exceptional environments. Our pilot S-Cam study of M83’s XUV disk led to support for the universal IMF at least in M83 (Koda et al. 2012). We propose an expansion of the pilot study, observing 6 XUV disks in NA656(Hα), B, I, and R-band with S-Cam. In conjunction with GALEX UV bands, these images will reveal the presence of O stars (Hα; NA656-R) and O&B stars (UV) in stellar clusters -thus, constraining the high-mass end of the IMF. The multi-broadband images will enable us to determine the masses of the clusters with much improved accuracy (previously, relied only on R). The proposed observations will not only increase the statistical significance of our previous result, but also enable us to analyze the stochastic effect of IMF sampling in very low-mass clusters (10^{2+3} M_sun) - the regime about which there is much ongoing debate."

Far-UV observations of comet C/2012 S1 (ISON) with FORTIS

NASA Astrophysics Data System (ADS)

McCandliss, Stephan R.; Feldman, Paul D.; Weaver, Harold A.; Fleming, Brian; Redwine, Keith; Li, Mary J.; Kutyrev, Alexander; Moseley, Samuel H.

2015-01-01

Far-UV imagery and objective grating spectroscopy of comet C/2012 S1 (ISON) were acquired from NASA sounding rocket 36.296 UG, launched on 20 November 2013 at 04:40 MST (20.48 Nov 2013 UT), 8.32 days pre-perihelion, from the White Sands Missile Range, NM. The comet was 0.1° below ground horizon, 0.44 AU from the Sun, 0.86 AU from the Earth, and at a solar elongation of 26.3°. The payload reached an apogee of 279 km and the total time pointed at the comet was 353 s. At the time of launch ISON was undergoing a factor of 5 increase in water production rate, going from 3.5e29 to 19.6e29 molecules s-1between 19.6 and 21.6 Nov (Combi et al. 2014), marking what is thought to be a final fragmentation event (Sekanina & Kracht 2014). Our instrument, a wide-field multi-object spectro-telescope called FORTIS (Far-UV Off Rowland-circle Telescope for Imaging and Spectroscopy), observed Lyα emissions in an objective grating mode through an open microshutter array, developed at the Goddard Space Flight Center, over a (1/2°)2 field-of-view. After accounting for slit losses and deadtime corrections we find a preliminary lower limit to the Lyα surface brightness of ~ 400 kilorayleighs, yielding a hydrogen production rate of QH ~ 5e29 atoms s-1, in reasonable agreement with the Combi result. We also acquired a broadband image of the comet in the 1280 to 1900 Å bandpass. This image shows a drop in count rate proportional to altitude caused by increased absorption of cometary emissions by terrestrial O2 located in the lower thermosphere. O2 absorption acts as a selective time dependent filter that attenuates cometary emissions from different atomic and molecular species at different rates during descent. Preliminary analysis suggests that the dominant species in a (1e5 km)2 nuclear region is neutral carbon. The radial profile in comparison to a Haser model suggests that the C parent molecule had a lifetime (at 1 AU) ~ 105 s; much shorter than the expected lifetime of CO. We

The Wavelength Dependence of the Lunar Phase Curve as Seen by the LRO LAMP

NASA Astrophysics Data System (ADS)

Liu, Y.; Retherford, K. D.; Greathouse, T. K.; Hendrix, A. R.; Mandt, K.; Gladstone, R.; Cahill, J. T.; Egan, A.; Kaufmann, D. E.; Grava, C.; Pryor, W. R.

2016-12-01

The Lunar Reconnaissance Orbiter (LRO) Lyman Alpha Mapping Project (LAMP) provides global coverage of both nightside and dayside of the Moon in the far ultraviolet (FUV) wavelengths. The nightside observations use roughly uniform diffuse illumination sources from interplanetary medium Lyman-α sky glow and UV-bright stars so that traditional photometric corrections do not apply. In contrast, the dayside observations use sunlight as its illumination source where bidirectional reflectance is measured. The bidirectional reflectance is dependent on the incident, emission, and phase angles as well as the soil properties. Thus the comparisons of dayside mapping and nightside mapping techniques offer a method for cross-comparing the photometric correction factors because the observations are made under different lighting and viewing conditions. Specifically, the nightside data well constrain the single-scattering coefficient. We'll discuss the wavelength dependence of the lunar phase curve as seen by the LAMP instrument in dayside data. Our preliminary results indicate that the reflectance in the FUV wavelengths decreases with the increasing phase angles from 0° to 90°, similar to the phase curve in the UV-visible wavelengths as studied by Hapke et al. (2012) using LRO wide angle camera (WAC) data, among other visible-wavelength lunar studies. Particularly, we'll report how coherent backscattering and shadow hiding contribute to the opposition surge, given the fact that the albedo at FUV wavelengths is extremely low and thus multiple scattering is significantly less important. Finally, we'll report the derived Hapke parameters at FUV wavelengths for our study areas.

Updated Status and Performance at the Fourth HST COS FUV Lifetime Position

NASA Astrophysics Data System (ADS)

Taylor, Joanna M.; De Rosa, Gisella; Fix, Mees B.; Fox, Andrew; Indriolo, Nick; James, Bethan; Jedrzejewski, Robert I.; Oliveira, Cristina M.; Penton, Steven V.; Plesha, Rachel; Proffitt, Charles R.; Rafelski, Marc; Roman-Duval, Julia; Sahnow, David J.; Snyder, Elaine M.; Sonnentrucker, Paule; White, James

2017-06-01

To mitigate the adverse effects of gain sag on the spectral quality and accuracy of Hubble Space Telescope’s Cosmic Origins Spectrograph FUV observations, COS FUV spectra will be moved from Lifetime Position 3 (LP3) to a new pristine location on the detectors at LP4 in July 2017. To achieve maximal spectral resolution while preserving detector area, the spectra will be shifted in the cross-dispersion (XD) direction by -2.5" (about -31 pixels) from LP3 or -5” (about 62 pixels) from the original LP1. At LP4, the wavelength calibration lamp spectrum can overlap with the previously gain-sagged LP2 PSA spectrum location. If lamp lines fall in the gain sag holes from LP2, it can cause line ratios to change and the wavelength calibration to fail. As a result, we have updated the Wavecal Parameters Reference Table and CalCOS to address this issue. Additionally, it was necessary to extend the current geometric correction in order to encompass the entire LP4 location. Here we present 2-D template profiles and 1-D spectral trace centroids derived at LP4 as well as LP4-related updates to the wavelength calibration, and geometric correction.

The HORUS Observatory - A Next Generation 2.4m UV-Optical Mission To Study Planetary, Stellar And Galactic Formation

NASA Astrophysics Data System (ADS)

Scowen, Paul A.; SDT, HORUS

2013-01-01

The High-ORbit Ultraviolet-visible Satellite (HORUS) is a 2.4-meter class UV-optical space telescope that will conduct a comprehensive and systematic study of the astrophysical processes and environments relevant for the births and life cycles of stars and their planetary systems, to investigate and understand the range of environments, feedback mechanisms, and other factors that most affect the outcome of the star and planet formation process. To do so, HORUS will provide 100 times greater imaging efficiency and more than 10 times greater UV spectroscopic sensitivity than has existed on the Hubble Space Telescope (HST). The HORUS mission will contribute vital information on how solar systems form and whether habitable planets should be common or rare. It also will investigate the structure, evolution, and destiny of galaxies and universe. This program relies on focused capabilities unique to space that no other planned NASA mission will provide: near-UV/visible (200-1075nm) wide-field, diffraction-limited imaging; and high-sensitivity, high-resolution UV (100-170nm) spectroscopy. The core HORUS design will provide wide field of view imagery and high efficiency point source FUV spectroscopy using a novel combination of spectral selection and field sharing. The HORUS Optical Telescope Assembly (OTA) design is based on modern light weight mirror technology with a faster primary mirror to shorten the overall package and thereby reduce mass. The OTA uses a three-mirror anastigmat configuration to provide excellent imagery over a large FOV - and is exactly aligned to use one of the recently released f/1.2 NRO OTAs as part of its design. The UV/optical Imaging Cameras use two 21k x 21k Focal Plane Arrays (FPAs). The FUV spectrometer uses cross strip anode based MCPs. This poster presents results from a 2010 design update requested by the NRC Decadal Survey, and reflects updated costs and technology to the original 2004 study. It is now one of the most mature 2.4m UVOIR

Vacuum deposition of iridium on large astronomical mirrors for use in the far UV

NASA Technical Reports Server (NTRS)

Herzig, H.; Spencer, R. S.

1982-01-01

An iridium coating has been deposited by electron-beam evaporation on a 0.91-m mirror which serves as the telescope primary of a sounding rocket instrument for far-UV spectrometry. The evaporation was carried out by applying 8 kV at 400 mA to the electron gun. Zone refined Ir of 99.99% purity was used, and the electron beam was electromagnetically swept over the surface of the evaporant. Under these conditions, deposition rates of 0.55 A/sec were achieved. The reflectance distribution achieved at a wavelength of 584 A was extremely uniform; the mean reflectance was 21.2% with a standard deviation of only 0.3%. This represents a substantial improvement over Al + MgF2 and Al + LiF coatings for applications involving multiple reflections and weak signals, as might be expected in a high-resolution spectrograph studying distant celestial objects.

Unexpected Far-Ultraviolet Photometric Characteristics On Mimas

NASA Astrophysics Data System (ADS)

Royer, E. M.; Hendrix, A. R.

2013-12-01

While infrared and visible are the most common wavelength domains used to investigate planetary surfaces, ultraviolet (UV) data are significant and useful. Here, we present the first far-UV phase curves of Mimas, thus displaying another piece of the Saturnian System puzzle. Our preliminary results shows that, one more time, Mimas surface properties are far from what we was expected. Namely, we observe a leading hemisphere brighter than the trailing hemisphere at some far-UV wavelengths. We used the far-UV channel of the Cassini/UVIS instrument, ranging from 118 to 190 nm. Disk-integrated phase curves for the leading hemisphere and the trailing hemisphere, at 180nm, have been produced. Data points span from 0.5 to 163.5 degrees in phase angle. Mimas displays a leading hemisphere brighter than its trailing hemisphere, when theory and previous Voyager observations at longer wavelengths attest of a brighter trailing hemisphere due to the impact of the E-ring grains on this face of the satellite. Surprisingly, UVIS data show a very bright opposition effect on Mimas leading hemisphere, greater than what is observed on Tethys or Dione leading hemisphere at the same wavelength of 180 nm. Preliminary results of photometric properties modeling seem to indicate an important contribution of the coherent-backscattering process in the opposition surge. Exogenic processes such as bombardment by energetic electrons and/or E-ring grains are discussed to explain this unexpected surface property of Mimas.

Far Ultraviolet Spectroscopy of Three Long Period Nova-Like Variables, V363 Aur, AC Cnc and RZ Gru

NASA Astrophysics Data System (ADS)

Bisol, Alexandra; Sion, E. M.

2011-01-01

We have selected three nova-like variables: V363 Aur, RZ Gru and AC Cnc, all of which are UX UMa types, having similar orbital periods well beyond the 3 to 4 hour range where most nova-likes are found. All should have very similar secondary stars given the fact that they their physical parameters are so similar. V363 Aur is a bona fide SW Sex star, and AC Cnc is a probable one, while RZ Gru is not a member of the SW Sex subclass. Our objective is to carry out the first synthetic spectral analysis of far ultraviolet spectra of the three systems using state-of-the-art models both of accretion disks and photospheres. Therefore we shall compare the distances we obtain from the best fitting synthetic spectral models to other distance estimates in the literature. We present model-derived accretion rates and distances for all three systems. The FUV flux range of RZ Gru and V363 Aur is dominated by radiation from an optically thick, steady state, accretion but for AC Cnc, we find that a hot white dwarf accounts for 70% of the FUV flux. We compare the FUV characteristics and physical properties of these three long period nova-like systems to the properties of other nova-likes at shorter periods. This work was supported in part by NSF grant AST0807892 to Villanova University.

A Correction for IUE UV Flux Distributions from Comparisons with CALSPEC

NASA Astrophysics Data System (ADS)

Bohlin, Ralph C.; Bianchi, Luciana

2018-04-01

A collection of spectral energy distributions (SEDs) is available in the Hubble Space Telescope (HST) CALSPEC database that is based on calculated model atmospheres for pure hydrogen white dwarfs (WDs). A much larger set (∼100,000) of UV SEDs covering the range (1150–3350 Å) with somewhat lower quality are available in the IUE database. IUE low-dispersion flux distributions are compared with CALSPEC to provide a correction that places IUE fluxes on the CALSPEC scale. While IUE observations are repeatable to only 4%–10% in regions of good sensitivity, the average flux corrections have a precision of 2%–3%. Our re-calibration places the IUE flux scale on the current UV reference standard and is relevant for any project based on IUE archival data, including our planned comparison of GALEX to the corrected IUE fluxes. IUE SEDs may be used to plan observations and cross-calibrate data from future missions, so the IUE flux calibration must be consistent with HST instrumental calibrations to the best possible precision.

SOLARNET & LAIME: Imaging & Spectroscopy in the Far Ultraviolet

NASA Astrophysics Data System (ADS)

Damé, Luc; Koutchmy, Serge

SOLARNET is a medium size high resolution solar physics mission proposed to CNES and ESA for a new start in 2007 and a possible launch in 2012 (CNES) or later (ESA Cosmic Vision framework: 2015-2016). Partnerships with India and China are under discussion, and several European contributions are considered. At the center of the SOLARNET mission is a 3-telescope interferometer of 1 meter baseline capable to provide 40 times the best ever spatial resolution achieved in Space with previous, current or even planned solar missions: 20 mas - 20 km on the Sun in the FUV. The interferometer is associated to an on-axis Subtractive Double Monochromator coupled to an Imaging Fourier Transform Spectrometer capable of high spectral (0.01 nm) and high temporal resolutions (50 ms) on a field of view of 40 arcsec and covering the FUV and UV spectral domains (from 117.5 to 400 nm). This will allow to access process scales of magnetic reconnection, dissipation, emerging flux and much more, from the chromosphere to the low corona with emphasis on the transition zone where the magnetic confinement is expected to be maximum. A whole new chapter of the physics of solar magnetic field structuring, evolution and mapping from the photosphere to the high atmosphere will be opened. The interferometer is completed by instruments providing larger field of view and higher temperature (EUV-XUV coronal imaging & spectroscopy) to define the context and extension of the solar phenomena. The 3-telescope interferometer design results of an extensive laboratory demonstration program of interferometric imaging of extended objects. We will review the scientific program of SOLARNET, describe the interferometer concept and design, present the results of the breadboard and give a short overview of the mission aspects. In a different category, LAIME, the Lyman Alpha Imaging-Monitor Experiment, is a remarkably simple (no mechanisms) and compact full Sun imager to be flown with TESIS on the CORONAS

Complex organic molecules in strongly UV-irradiated gas⋆

PubMed Central

Cuadrado, S.; Goicoechea, J. R.; Cernicharo, J.; Fuente, A.; Pety, J.; Tercero, B.

2017-01-01

We investigate the presence of complex organic molecules (COMs) in strongly UV-irradiated interstellar molecular gas. We have carried out a complete millimetre (mm) line survey using the IRAM 30 m telescope towards the edge of the Orion Bar photodissociation region (PDR), close to the H2 dissociation front, a position irradiated by a very intense far-UV (FUV) radiation field. These observations have been complemented with 8.5″ resolution maps of the H2CO JKa,Kc = 51,5 → 41,4 and C18O J = 3 → 2 emission at 0.9 mm. Despite being a harsh environment, we detect more than 250 lines from COMs and related precursors: H2CO, CH3OH, HCO, H2CCO, CH3CHO, H2CS, HCOOH, CH3CN, CH2NH, HNCO, H213CO, and HC3N (in decreasing order of abundance). For each species, the large number of detected lines allowed us to accurately constrain their rotational temperatures (Trot) and column densities (N). Owing to subthermal excitation and intricate spectroscopy of some COMs (symmetric- and asymmetric-top molecules such as CH3CN and H2CO, respectively), a correct determination of N and Trot requires building rotational population diagrams of their rotational ladders separately. The inferred column densities are in the 1011 – 1013cm−2 range. We also provide accurate upper limit abundances for chemically related molecules that might have been expected, but are not conclusively detected at the edge of the PDR (HDCO, CH3O, CH3NC, CH3CCH, CH3OCH3, HCOOCH3, CH3CH2OH, CH3CH2CN, and CH2CHCN). A non-thermodynamic equilibrium excitation analysis for molecules with known collisional rate coefficients suggests that some COMs arise from different PDR layers but we cannot resolve them spatially. In particular, H2CO and CH3CN survive in the extended gas directly exposed to the strong FUV flux (Tk = 150 – 250 K and Td ≳ 60 K), whereas CH3OH only arises from denser and cooler gas clumps in the more shielded PDR interior (Tk = 40 – 50 K). The non-detection of HDCO towards the PDR edge is

Complex organic molecules in strongly UV-irradiated gas.

PubMed

Cuadrado, S; Goicoechea, J R; Cernicharo, J; Fuente, A; Pety, J; Tercero, B

2017-07-01

We investigate the presence of complex organic molecules (COMs) in strongly UV-irradiated interstellar molecular gas. We have carried out a complete millimetre (mm) line survey using the IRAM 30 m telescope towards the edge of the Orion Bar photodissociation region (PDR), close to the H 2 dissociation front, a position irradiated by a very intense far-UV (FUV) radiation field. These observations have been complemented with 8.5″ resolution maps of the H 2 CO J K a , K c = 5 1,5 → 4 1,4 and C 18 O J = 3 → 2 emission at 0.9 mm. Despite being a harsh environment, we detect more than 250 lines from COMs and related precursors: H 2 CO, CH 3 OH, HCO, H 2 CCO, CH 3 CHO, H 2 CS, HCOOH, CH 3 CN, CH 2 NH, HNCO, [Formula: see text] and HC 3 N (in decreasing order of abundance). For each species, the large number of detected lines allowed us to accurately constrain their rotational temperatures ( T rot ) and column densities ( N ). Owing to subthermal excitation and intricate spectroscopy of some COMs (symmetric- and asymmetric-top molecules such as CH 3 CN and H 2 CO, respectively), a correct determination of N and T rot requires building rotational population diagrams of their rotational ladders separately. The inferred column densities are in the 10 11 - 10 13 cm -2 range. We also provide accurate upper limit abundances for chemically related molecules that might have been expected, but are not conclusively detected at the edge of the PDR (HDCO, CH 3 O, CH 3 NC, CH 3 CCH, CH 3 OCH 3 , HCOOCH 3 , CH 3 CH 2 OH, CH 3 CH 2 CN, and CH 2 CHCN). A non-thermodynamic equilibrium excitation analysis for molecules with known collisional rate coefficients suggests that some COMs arise from different PDR layers but we cannot resolve them spatially. In particular, H 2 CO and CH 3 CN survive in the extended gas directly exposed to the strong FUV flux ( T k = 150 - 250 K and T d ≳ 60 K), whereas CH 3 OH only arises from denser and cooler gas clumps in the more shielded PDR interior

Probing the Initial Mass Function in Extended Ultraviolet (XUV) Disks

NASA Astrophysics Data System (ADS)

Koda, Jin

2013-01-01

"The GALEX UV satellite discovered tantalizing evidence of star formation (SF) far beyond the optical edge of galactic disks (i.e. extended UV disk, or XUV disk). This discovery provides a new opportunity for studying SF in the exceedingly low-density environment (˜1/10 of typical SF density), spurring intense debate on the universality of the initial mass function (IMF) in such exceptional environments. Our pilot S-Cam study of M83’s XUV disk led to support for the universal IMF at least in M83 (Koda et al. 2012). We propose an expansion of the pilot study by an order of magnitude, by observing additional 6 XUV disks in NA656(Hα), B, I, and R-band with S-Cam in S13A. In conjunction with GALEX UV bands, these images will reveal the presence of O stars (Hα; NA656-R) and O&B stars (UV) in stellar clusters -thus, constraining the high-mass end of the IMF. These multi-broadband images will enable us to determine the masses of the clusters with much improved accuracy (previously, relied only on R). The proposed observations will not only increase the statistical significance of our previous result, but also enable us to analyze the stochastic effect of IMF sampling in very low-mass - clusters (10^(2+3) M_sun) - the regime about which there is much ongoing debate."

Probing the Initial Mass Function in Extended Ultraviolet (XUV) Disks

NASA Astrophysics Data System (ADS)

Koda, Jin

2013-01-01

"The GALEX UV satellite discovered tantalizing evidence of star formation (SF) far beyond the optical edge of galactic disks (i.e. extended UV disk, or XUV disk). This discovery provides a new opportunity for studying SF in the exceedingly low-density environment (˜1/10 of typical SF density), spurring intense debate on the universality of the initial mass function (IMF) in such exceptional environments. Our pilot S-Cam study of M83’s XUV disk led to support for the universal IMF at least in M83 (Koda et al. 2012). We propose an expansion of the pilot study by about an order of magnitude, by observing 6 XUV disks in NA656(Hα), B, I, and R-band with S-Cam in S13B. In conjunction with GALEX UV bands, these images will reveal the presence of O stars (Hα) and O&B stars (UV) in stellar clusters -thus, constraining the high-mass end of the IMF. These multi-broadband images will enable us to determine the masses of the clusters with much improved accuracy (previously, relied only on R). The proposed observations will not only increase the statistical significance of our previous result, but also enable us to analyze the stochastic effect of IMF sampling in very low-mass - clusters (10^{2+3} M_sun) - the regime of ongoing debate. Previously allocated 1+2 nights were cancelled (telescope failures)."

Detection of a Hot Binary Companion of eta Carinae

NASA Technical Reports Server (NTRS)

Sonnebom, G.; Iping, R. C.; Gull, T. R.; Massa, D. L.; Hillier, D. J.

2006-01-01

A hot companion of eta Carinae has been detected using high resolution spectra (905 - 1180 A) obtained with the Far Ultraviolet Spectroscopic Explorer (FUSE) satellite. Observations were obtained at two epochs of the 2024-day orbit: 2003 June during ingress to the 2003.5 X-ray eclipse and 2004 April several months after egress. These data show that essentially all the far-UV flux from eta Car shortward of Lyman alpha disappeared at least two days before the start of the X-ray eclipse (2003 June 29), implying that the hot companion, eta Car B, was also eclipsed by the dense wind or extended atmosphere of eta Car A. Analysis of the far-UV spectrum shows that eta Car B is a luminous hot star. N II 1084-1086 emission disappears at the same time as the far-UV continuum, indicating that this feature originates from eta Car B itself or in close proximity to it. The strong N II emission also raises the possibility that the companion star is nitrogen rich. The observed FUV flux levels and spectral features, combined with the timing of their disappearance, is consistent with eta Carinae being a massive binary system

Detection of a Hot Binary Companion of eta Carinae

NASA Technical Reports Server (NTRS)

Sonneborn, G.; Iping, R. C.; Gull, T. R.; Massa, D.; Hillier, D. J.

2006-01-01

A hot companion of eta Carinae has been detected using high resolution spectra (905 - 1 180 Angsroms) obtained with the Far Ultraviolet Spectroscopic Explorer (FUSE) satellite. Observations were obtained at two epochs of the 2024-day orbit: 2003 June during ingress to the 2003.5 X-ray eclipse and 2004 April several months after egress. These data show that essentially all the far-UV flux from eta Car shortward of Lyman alpha disappeared at least two days before the start of the X-ray eclipse (2003 June 29), implying that the hot companion, eta Car By was also eclipsed by the dense wind or extended atmosphere of eta Car A. Analysis of the far-UV spectrum shows that eta Car B is a luminous hot star. N II 1084-1086 emission disappears at the same time as the far-UV continuum, indicating that this feature originates from eta Car B itself or in close proximity to it. The strong N II emission also raises the possibility that the companion star is nitrogen rich. The observed FUV flux levels and spectral features, combined with the timing of their disappearance, are consistent with eta Carinae being a massive binary system.

Suppressed Far-UV Stellar Activity and Low Planetary Mass Loss in the WASP-18 System

NASA Astrophysics Data System (ADS)

Fossati, L.; Koskinen, T.; France, K.; Cubillos, P. E.; Haswell, C. A.; Lanza, A. F.; Pillitteri, I.

2018-03-01

WASP-18 hosts a massive, very close-in Jupiter-like planet. Despite its young age (<1 Gyr), the star presents an anomalously low stellar activity level: the measured {log}{R}HK}{\\prime } activity parameter lies slightly below the basal level; there is no significant time-variability in the {log}{R}HK}{\\prime } value; there is no detection of the star in the X-rays. We present results of far-UV observations of WASP-18 obtained with COS on board of Hubble Space Telescope aimed at explaining this anomaly. From the star’s spectral energy distribution, we infer the extinction (E(B-V) ≈ 0.01 mag) and then the interstellar medium (ISM) column density for a number of ions, concluding that ISM absorption is not the origin of the anomaly. We measure the flux of the four stellar emission features detected in the COS spectrum (C II, C III, C IV, Si IV). Comparing the C II/C IV flux ratio measured for WASP-18 with that derived from spectra of nearby stars with known age, we see that the far-UV spectrum of WASP-18 resembles that of old (>5 Gyr), inactive stars, in stark contrast with its young age. We conclude that WASP-18 has an intrinsically low activity level, possibly caused by star–planet tidal interaction, as suggested by previous studies. Re-scaling the solar irradiance reference spectrum to match the flux of the Si IV line, yields an XUV integrated flux at the planet orbit of 10.2 erg s‑1 cm‑2. We employ the rescaled XUV solar fluxes to models of the planetary upper atmosphere, deriving an extremely low thermal mass-loss rate of 10‑20 M J Gyr‑1. For such high-mass planets, thermal escape is not energy limited, but driven by Jeans escape. Based on observations made with the NASA/ESA Hubble Space Telescope, obtained from MAST at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. These observations are associated with program #13859. Based on

Far-UV Spectroscopy of the Planet-hosting Star WASP-13: High-energy Irradiance, Distance, Age, Planetary Mass-loss Rate, and Circumstellar Environment

NASA Astrophysics Data System (ADS)

Fossati, L.; France, K.; Koskinen, T.; Juvan, I. G.; Haswell, C. A.; Lendl, M.

2015-12-01

Several transiting hot Jupiters orbit relatively inactive main-sequence stars. For some of those, the {log}{R}{HK}\\prime activity parameter lies below the basal level (-5.1). Two explanations have been proposed so far: (i) the planet affects the stellar dynamo, (ii) the {log}{R}{HK}\\prime measurements are biased by extrinsic absorption, either by the interstellar medium (ISM) or by material local to the system. We present here Hubble Space Telescope/COS far-UV spectra of WASP-13, which hosts an inflated hot Jupiter and has a measured {log}{R}{HK}\\prime value (-5.26), well below the basal level. From the star’s spectral energy distribution we obtain an extinction E(B - V) = 0.045 ± 0.025 mag and a distance d = 232 ± 8 pc. We detect at ≳4σ lines belonging to three different ionization states of carbon (C i, C ii, and C iv) and the Si iv doublet at ˜3σ. Using far-UV spectra of nearby early G-type stars of known age, we derive a C iv/C i flux ratio-age relation, from which we estimate WASP-13's age to be 5.1 ± 2.0 Gyr. We rescale the solar irradiance reference spectrum to match the flux of the C iv 1548 doublet. By integrating the rescaled solar spectrum, we obtain an XUV flux at 1 AU of 5.4 erg s-1 cm-2. We use a detailed model of the planet’s upper atmosphere, deriving a mass-loss rate of 1.5 × 1011 g s-1. Despite the low {log}{R}{HK}\\prime value, the star shows a far-UV spectrum typical of middle-aged solar-type stars, pointing toward the presence of significant extrinsic absorption. The analysis of a high-resolution spectrum of the Ca ii H&K lines indicates that the ISM absorption could be the origin of the low {log}{R}{HK}\\prime value. Nevertheless, the large uncertainty in the Ca ii ISM abundance does not allow us to firmly exclude the presence of circumstellar gas. Based on observations made with the NASA/ESA Hubble Space Telescope, obtained from MAST at the Space Telescope Science Institute, which is operated by the Association of Universities

Searching for Radial Velocity Variations in eta Carinae

NASA Technical Reports Server (NTRS)

Iping, R. C.; Sonneborn, G.; Gull, T. R.; Ivarsson, S.; Nielsen, K.

2006-01-01

A hot companion of eta Carinae has been detected using high resolution spectra (905 - 1180 A) obtained with the Far Ultraviolet Spectroscopic Explorer (FUSE) satellite (see poster by Sonneborn et al.). Analysis of the far-UV spectrum shows that eta Car B is a luminous hot star. The N II 1084-86 emission feature indicates that the star may be nitrogen rich. The FUV continuum and the S IV 1073 P-Cygni wind line suggest that the effective temperature of eta Car B is at least 25,000 K. FUV spectra of eta Carinae were obtained with the FUSE satellite at 9 epochs between 2000 February and 2005 July. The data consists of 12 observations taken with the LWRS aperture (30x30 arcsec), three with the HIRS aperture (1.25x20 arcsec), and one MRDS aperture (4x20 arcsec). In this paper we discuss the analysis of these spectra to search for radial velocity variations associated with the 5.54-year binary orbit of Eta Car AB.

Probing the Initial Mass Function in Extended Ultraviolet (XUV) Disks

NASA Astrophysics Data System (ADS)

Koda, Jin

2014-01-01

The GALEX UV satellite discovered tantalizing evidence of star formation (SF) far beyond the optical edge of galactic disks (i.e. XUV disk). This discovery provides a new opportunity for studying SF in the exceedingly low-density environment (~1/10 of typical SF density), spurring intense debate on the universality of the initial mass function (IMF) in such exceptional environments. Our pilot study led to support for the universal IMF at least in M83’s XUV disk (Koda et al. 2012). We propose an expansion of the pilot study by about an order of magnitude, by observing total ~ 10 XUV disks (6 disks in S14A) in NA656(Halpha), B, I, and R-band with S-Cam. In conjunction with GALEX UV bands, these images will reveal the presence of O stars (Halpha) and O&B stars (UV) in stellar clusters -thus, constraining the high-mass end of the IMF. These multi-broadband images will enable us to determine the masses of the clusters with much improved accuracy (previously, relied only on R). This project will not only increase the statistical significance of our previous result, but also enable us to analyze the stochastic effect of IMF sampling in very low-mass clusters (102-3 Msun) - the regime of ongoing debate. This proposal will complete this on-going project with S-Cam.

Globules and pillars in Cygnus X. I. Herschel far-infrared imaging of the Cygnus OB2 environment

NASA Astrophysics Data System (ADS)

Schneider, N.; Bontemps, S.; Motte, F.; Blazere, A.; André, Ph.; Anderson, L. D.; Arzoumanian, D.; Comerón, F.; Didelon, P.; Di Francesco, J.; Duarte-Cabral, A.; Guarcello, M. G.; Hennemann, M.; Hill, T.; Könyves, V.; Marston, A.; Minier, V.; Rygl, K. L. J.; Röllig, M.; Roy, A.; Spinoglio, L.; Tremblin, P.; White, G. J.; Wright, N. J.

2016-06-01

The radiative feedback of massive stars on molecular clouds creates pillars, globules and other features at the interface between the H II region and molecular cloud. Optical and near-infrared observations from the ground as well as with the Hubble or Spitzer satellites have revealed numerous examples of such cloud structures. We present here Herschel far-infrared observations between 70 μm and 500 μm of the immediate environment of the rich Cygnus OB2 association, performed within the Herschel imaging survey of OB Young Stellar objects (HOBYS) program. All of the observed irradiated structures were detected based on their appearance at 70 μm, and have been classified as pillars, globules, evaporating gasous globules (EGGs), proplyd-like objects, and condensations. From the 70 μm and 160 μm flux maps, we derive the local far-ultraviolet (FUV) field on the photon dominated surfaces. In parallel, we use a census of the O-stars to estimate the overall FUV-field, that is 103-104 G0 (Habing field) close to the central OB cluster (within 10 pc) and decreases down to a few tens G0, in a distance of 50 pc. From a spectral energy distribution (SED) fit to the four longest Herschel wavelengths, we determine column density and temperature maps and derive masses, volume densities and surface densities for these structures. We find that the morphological classification corresponds to distinct physical properties. Pillars and globules are massive (~500 M⊙) and large (equivalent radius r ~ 0.6 pc) structures, corresponding to what is defined as "clumps" for molecular clouds. EGGs and proplyd-likeobjects are smaller (r ~ 0.1 and 0.2 pc) and less massive (~10 and ~30 M⊙). Cloud condensations are small (~0.1 pc), have an average mass of 35 M⊙, are dense (~6 × 104 cm-3), and can thus be described as molecular cloud "cores". All pillars and globules are oriented toward the Cyg OB2 association center and have the longest estimated photoevaporation lifetimes, a few million

High Energy (X-ray/UV) Radiation Fields of Young, Low-Mass Stars Observed with Chandra and HST

NASA Astrophysics Data System (ADS)

Brown, Alexander; Brown, J. M.; Herczeg, G.; Bary, J.; Walter, F. M.; Ayres, T. R.

2010-01-01

Pre-main-sequence (PMS) stars are strong UV and X-ray emitters and the high energy (UV/X-ray) radiation from the central stars directly influences the physical and chemical processes in their protoplanetary disks. Gas and dust in protoplanetary systems are excited by these photons, which are the dominant ionization source for hundreds of AU around the star. X-rays penetrate deep into disks and power complex chemistry on grain surfaces. ``Transitional disks'' are a crucial and important evolutionary stage for PMS stars and protoplanetary systems. These disks have transformed most of the dust and gas in their inner regions into planetesimals or larger solid bodies. The disks show clear inner ``holes'' that almost certainly harbor infant planetary systems, given the very sharp gap boundaries inferred. Transitional disks are rare and represent a short-lived phase of PMS disk evolution. We have observed a sample of PMS stars at a variety of evolutionary stages, including the transitional disk stars GM Aur (K5) and HD135344B (F4). Chandra ACIS CCD-resolution X-ray spectra and HST STIS and COS FUV spectra are being used to reconstruct the full high energy (X-ray/EUV/FUV/NUV) spectra of these young stars, so as to allow detailed modeling of the physics and chemistry of their circumstellar environments, thereby providing constraints on the formation process of planetary systems. This work is supported by Chandra grants GO8-9024X, GO9-0015X and GO9-0020B and HST grants for GO projects 11336, 11828, and 11616 to the University of Colorado.

Monitoring the High-Energy Radiation Environment of Exoplanets around Lowmass Stars with SPARCS (Star-Planet Activity Research CubeSat)

NASA Astrophysics Data System (ADS)

Shkolnik, Evgenya

Seventy-five billion M dwarfs in our galaxy host at least one small planet in the habitable zone (HZ). The stellar ultraviolet (UV) radiation from M dwarfs is strong and highly variable, and impacts planetary atmospheric loss, composition and habitability. These effects are amplified by the extreme proximity of their HZs (0.1–0.4 AU). JWST will characterize HZ M dwarf planets and attempt the first spectroscopic search for life beyond the Solar System. Knowing the UV environments of M dwarf planets will be crucial to understanding their atmospheric composition and a key parameter in discriminating between biological and abiotic sources for observed biosignatures. The UV flux emitted during the super-luminous premain sequence phase of M stars drives water loss and photochemical O2 buildup for terrestrial planets within the HZ. This phase can persist for up to a billion years for the lowest mass M stars. Afterwards, UV-driven photochemistry during the main sequence phase strongly affects a planet’s atmosphere, could limit the planet’s potential for habitability, and may confuse studies of habitability by creating false chemical biosignatures. Our proposed CubeSat observatory will be the first mission to provide the time-dependent spectral slope, intensity and evolution of M dwarf stellar UV radiation. These measurements are crucial to interpreting observations of planetary atmospheres around low-mass stars. Mission: The Star-Planet Activity Research CubeSat (SPARCS) will be a 6U CubeSat devoted to monitoring 25 M stars in two UV bands: SPARCS far-UV (S- FUV: 153–171 nm) and SPARCS near-UV (S-NUV: 260– 300 nm). For each target, SPARCS will observe continuously between one and three complete stellar rotations (4–45 days) over a mission lifetime of 2 years. A UV characterization survey of M dwarfs, the most common of planet hosts, is a perfect experiment for a CubeSat: - UV astronomy cannot be done from the ground because of Earth’s atmospheric absorption

Estimation of the Spectral Type of the Progenitor of the ASASSN-17oz Transient

NASA Astrophysics Data System (ADS)

McCollum, B.; Rottler, Lee

2017-11-01

We report the result of SED fitting of the precursor object of the ASASSN-17oz transient (ATel #10991) using pre-outburst archival photometry. We used the following magnitudes, from the sources noted: GALEX All-sky FUV (1516A) = 21 (AB magnitude upper limit) GALEX All-sky NUV (2267A) = 22 (AB magnitude upper limit) Johnson B = 17.17 +/- 0.55 (USNO-B1.0 catalog, two values) Johnson V = 16.3 (Jayasinghe et al. 2017, ATel #10991) Johnson R = 16.02 (NOMAD catalog, Zacharias 2005) Pan-STARRS g = 17.108 +/- 0.049 Pan-STARRs r = 16.424 +/- 0.017 Pan-STARRS i = 15.885 +/- 0.053 Pan-STARRS z = 15.77 +/- 0.019 2MASS J = 14.544 +/- 0.032 2MASS H = 14.025 +/- 0.04 2MASS Ks = 13.755 +/- 0.044 WISE W1 = 13.78 +/- 0.028 WISE W2 = 14.712 +/- 0.041 WISE W3 = 12.581 (upper limit) These measurements were obtained at epochs spread over a few decades.

Summary of Quantitative Interpretation of Image Far Ultraviolet Auroral Data

NASA Technical Reports Server (NTRS)

Frey, H. U.; Immel, T. J.; Mende, S. B.; Gerard, J.-C.; Hubert, B.; Habraken, S.; Span, J.; Gladstone, G. R.; Bisikalo, D. V.; Shematovich, V. I.;

Mars, Venus, Earth and Titan UV Laboratory Aeronomy by Electron Impact

NASA Astrophysics Data System (ADS)

Malone, C. P.; Ajello, J. M.; McClintock, W. E.; Eastes, R.; Evans, J. S.; Holsclaw, G.; Schneider, N. M.; Jain, S.; Gerard, J. C. M. C.; Hoskins, A.

2017-12-01

The UV response of the Mars, Earth, Titan and Venus upper atmospheres to the solar radiation fields [solar wind and solar EUV] is the focus of the present generation of Mars, Earth, Titan and Venus missions. These missions are Mars Express (MEX), the Mars Atmosphere and Volatile Evolution Mission (MAVEN), Cassini at Titan, Global-scale Observations of the Limb and Disk (GOLD) mission for Earth and Venus Express (VEX). Each spacecraft is equipped with a UV spectrometer that senses far ultraviolet (FUV) emissions from 110-190 nm, whose dayglow intensities are proportional to three quantities:1) particle (electron, ion) fluxes, 2) the altitude distribution of species in the ionosphere: CO, CO2, O, N2 at Venus and Mars and N2, O and O2 at Titan and Earth and 3) the emission cross section for the interaction process. UV spectroscopy provides a benchmark to the present space environment and indicates pathways for removing upper atmosphere gas (e.g., water escape from Mars and Earth) or N2 escape at Titan over eons. We present a UV laboratory program that utilizes an instrument, unique in the world, at the University of Colorado that can measure excitation mechanisms by particle (electron, ion) impact and the resulting emission cross sections that include processes occurring in a planetary atmosphere, particularly the optically forbidden emissions presented by the Cameron bands, the Lyman Birge Hopfield bands and the OI 135.6 nm multiplet. There are presently uncertainties by a factor of two in the existing measurements of the emission cross section, affecting modeling of electron transport. We have utilized the MAVEN Imaging Ultraviolet Spectrograph (IUVS) engineering model which operates at moderate spectral resolution ( 0.5-1.0nm FWHM) to obtain the full vibrational spectra of the Cameron band system CO(a 3Π → X 1Σ+) from both CO direct excitation and CO2 dissociative excitation, and for the dipole-allowed Fourth Positive band system of CO, while for N2 we have

The Origins of UV-optical Color Gradients in Star-forming Galaxies at z ˜ 2: Predominant Dust Gradients but Negligible sSFR Gradients

NASA Astrophysics Data System (ADS)

Liu, F. S.; Jiang, Dongfei; Faber, S. M.; Koo, David C.; Yesuf, Hassen M.; Tacchella, Sandro; Mao, Shude; Wang, Weichen; Guo, Yicheng; Fang, Jerome J.; Barro, Guillermo; Zheng, Xianzhong; Jia, Meng; Tong, Wei; Liu, Lu; Meng, Xianmin

2017-07-01

The rest-frame UV-optical (I.e., NUV - B) color is sensitive to both low-level recent star formation (specific star formation rate—sSFR) and dust. In this Letter, we extend our previous work on the origins of NUV - B color gradients in star-forming galaxies (SFGs) at z˜ 1 to those at z˜ 2. We use a sample of 1335 large (semimajor axis radius {R}{SMA}> 0\\buildrel{\\prime\\prime}\\over{.} 18) SFGs with extended UV emission out to 2{R}{SMA} in the mass range {M}* ={10}9{--}{10}11 {M}⊙ at 1.5< z< 2.8 in the CANDELS/GOODS-S and UDS fields. We show that these SFGs generally have negative NUV - B color gradients (redder centers), and their color gradients strongly increase with galaxy mass. We also show that the global rest-frame FUV - NUV color is approximately linear with {A}{{V}}, which is derived by modeling the observed integrated FUV to NIR spectral energy distributions of the galaxies. Applying this integrated calibration to our spatially resolved data, we find a negative dust gradient (more dust extinguished in the centers), which steadily becomes steeper with galaxy mass. We further find that the NUV - B color gradients become nearly zero after correcting for dust gradients regardless of galaxy mass. This indicates that the sSFR gradients are negligible and dust reddening is likely the principal cause of negative UV-optical color gradients in these SFGs. Our findings support that the buildup of the stellar mass in SFGs at Cosmic Noon is self-similar inside 2{R}{SMA}.

Modeling Far-UV Fluorescent Emission Features of Warm Molecular Hydrogen in the Inner Regions of Protoplanetary Disks

NASA Astrophysics Data System (ADS)

Hoadley, Keri; France, Kevin

2015-01-01

Probing the surviving molecular gas within the inner regions of protoplanetary disks (PPDs) around T Tauri stars (1 - 10 Myr) provides insight into the conditions in which planet formation and migration occurs while the gas disk is still present. We model observed far ultraviolet (FUV) molecular hydrogen (H₂) fluorescent emission lines that originate within the inner regions (< 10 AU) of 9 well-studied Classic T Tauri stars, using the Hubble Space Telescope Cosmic Origins Spectrograph (COS), to explore the physical structure of the molecular disk at different PPD dust evolutionary stages. We created a 2D radiative transfer model that estimates the density and temperature distributions of warm, inner radial H₂ (T > 1500 K) with a set of 6 free parameters and produces a data cube of expected emission line profiles that describe the physical structure of the inner molecular disk atmosphere. By comparing the modeled emission lines with COS H₂ fluorescence emission features, we estimate the physical structure of the molecular disk atmosphere for each target with the set of free parameters that best replicate the observed lines. First results suggest that, for all dust evolutionary stages of disks considered, ground-state H₂ populations are described by a roughly constant temperature T(H₂) = 2500 +/- 1000 K. Possible evolution of the density structure of the H₂ atmosphere between intact and depleting dust disks may be distinguishable, but large errors in the inferred best-fit parameter sets prevent us from making this conclusion. Further improvements to the modeling framework and statistical comparison in determining the best-fit model-to-data parameter sets are ongoing, beginning with improvements to the radiative transfer model and use of up-to-date HI Lyman α absorption optical depths (see McJunkin in posters) to better estimate disk structural parameters. Once improvements are implemented, we will investigate the possible presence of a molecular wind

Changes to the Spectral Extraction Algorithm at the Third COS FUV Lifetime Position

NASA Astrophysics Data System (ADS)

Taylor, Joanna M.; Azalee Bostroem, K.; Debes, John H.; Ely, Justin; Hernandez, Svea; Hodge, Philip E.; Jedrzejewski, Robert I.; Lindsay, Kevin; Lockwood, Sean A.; Massa, Derck; Oliveira, Cristina M.; Penton, Steven V.; Proffitt, Charles R.; Roman-Duval, Julia; Sahnow, David J.; Sana, Hugues; Sonnentrucker, Paule

2015-01-01

Due to the effects of gain sag on flux on the COS FUV microchannel plate detector, the COS FUV spectra will be moved in February 2015 to a pristine location on the detector, from Lifetime Position 2 (LP2) to LP3. The spectra will be shifted in the cross-dispersion (XD) direction by -2.5", about -31 pixels, from the original LP1. In contrast, LP2 was shifted by +3.5", about 41 pixels, from LP1. By reducing the LP3-LP1 separation compared to the LP2-LP1 separation, we achieve maximal spectral resolution at LP3 while preserving more detector area for future lifetime positions. In the current version of the COS boxcar extraction algorithm, flux is summed within a box of fixed height that is larger than the PSF. Bad pixels located anywhere within the extraction box cause the entire column to be discarded. At the new LP3 position the current extraction box will overlap with LP1 regions of low gain (pixels which have lost >5% of their sensitivity). As a result, large portions of spectra will be discarded, even though these flagged pixels will be located in the wings of the profiles and contain a negligible fraction of the total source flux. To avoid unnecessarily discarding columns affected by such pixels, an algorithm is needed that can judge whether the effects of gain-sagged pixels on the extracted flux are significant. The "two-zone" solution adopted for pipeline use was tailored specifically for the COS FUV data characteristics: First, using a library of 1-D spectral centroid ("trace") locations, residual geometric distortions in the XD direction are removed. Next, 2-D template profiles are aligned with the observed spectral image. Encircled energy contours are calculated and an inner zone that contains 80% of the flux is defined, as well as an outer zone that contains 99% of the flux. With this approach, only pixels flagged as bad in the inner 80% zone will cause columns to be discarded while flagged pixels in the outer zones do not affect extraction. Finally, all

Ultraviolet Radiative Transfer Modeling of Nearby Galaxies with Extraplanar Dusts

NASA Astrophysics Data System (ADS)

Shinn, Jong-Ho; Seon, Kwang-Il

2015-12-01

In order to examine their relation to the host galaxy, the extraplanar dusts of six nearby galaxies are modeled, employing a three-dimensional Monte Carlo radiative transfer code. The targets are from the highly inclined galaxies that show dust-scattered ultraviolet halos, and the archival Galaxy Evolution Explorer FUV band images were fitted with the model. The observed images are generally well-reproduced by two dust layers and one light source layer, whose vertical and radial distributions have exponential profiles. We obtained several important physical parameters, such as star formation rate (SFRUV), face-on optical depth, and scale-heights. Three galaxies (NGC 891, NGC 3628, and UGC 11794) show clear evidence for the existence of an extraplanar dust layer. However, it is found that the remaining three targets (IC 5249, NGC 24, and NGC 4173) do not necessarily need a thick dust disk to model the ultraviolet (UV) halo, because its contribution is too small and the UV halo may be caused by the wing part of the GALEX point spread function. This indicates that the galaxy samples reported to have UV halos may be contaminated by galaxies with negligible extraplanar (halo) dust. The galaxies showing evidence of an extraplanar dust layer fall within a narrow range on the scatter plots between physical parameters such as SFRUV and extraplanar dust mass. Several mechanisms that could possibly produce the extraplanar dust are discussed. We also found a hint that the extraplanar dust scale-height might not be much different from the polycyclic aromatic hydrocarbon emission characteristic height.

Comparison of Nitrogen Incorporation in Tholins Produced by FUV Irradiation and Spark Discharge

NASA Technical Reports Server (NTRS)

Horst, S. M.; DeWitt, H. L.; Trainer, M. G.; Tolbert, M. A.

2012-01-01

The discovery of very heavy ions (Coates et al., 2007) in Titan's thermosphere has dramatically altered our understanding of the processes involved in the formation of the complex organic aerosols that comprise Titan's characteristic haze. Before Cassini's arrival, it was believed that aerosol production began in the stratosphere where the chemical processes were predominantly initiated by FUV radiation. This understanding guided the design of Titan atmosphere simulation experiments. However, the energy environment of the thermosphere is significantly different than the stratosphere; in particular there is a greater flux of EUV photons and energetic particles available to initiate chemical reactions, including the destruction of N2. in the upper atmosphere. Using a High Resolution Time-of-Flight Aerosol Mass Spectrometer (HR-ToF-AMS), we have obtained in situ composition measurements of aerosol particles (so'called "tholins") produced in CH4/N2 gas mixtures subjected to either FUV radiation (deuterium lamp, 115-400 nm) (Trainer et al., 2012) or a spark discharge. A comparison of the composition of tholins produced using the two different energy sources will be presented, in particular with regard to the variation in nitrogen content of the two types of tholin. Titan's aerosols are known to contain significant amounts of nitrogen (Israel et al., 2005) and therefore understanding the role of nitrogen in the aerosol chemistry is important to further our knowledge of the formation and evolution of aerosols in Titan's atmosphere.

Study of first electronic transition and hydrogen bonding state of ultra-thin water layer of nanometer thickness on an α-alumina surface by far-ultraviolet spectroscopy

NASA Astrophysics Data System (ADS)

Goto, Takeyoshi; Kinugasa, Tomoya

2018-05-01

The first electronic transition (A˜ ← X˜) and the hydrogen bonding state of an ultra-thin water layer of nanometer thickness between two α-alumina surfaces (0.5-20 nm) were studied using far-ultraviolet (FUV) spectroscopy in the wavelength range 140-180 nm. The ultra-thin water layer of nanometer thickness was prepared by squeezing a water droplet ( 1 μL) between a highly polished α-alumina prism and an α-alumina plate using a high pressure clamp ( 4.7 MPa), and the FUV spectra of the water layer at different thicknesses were measured using the attenuated total reflection method. As the water layer became thinner, the A˜ ← X˜ bands were gradually shifted to higher or lower energy relative to that of bulk water; at thicknesses smaller than 4 nm, these shifts were substantial (0.1-0.2 eV) in either case. The FUV spectra of the water layer with thickness < 4 nm indicate the formation of structured ice-like hydrogen bond (H-bond) layers for the higher energy shifts or the formation of slightly weaker H-bond layers as compared to those in the bulk liquid state for lower energy shifts. In either case, the H-bond structure of bulk liquid water is nearly lost at thicknesses below 4 nm, because of steric hydration forces between the α-alumina surfaces.

Complex organic molecules in strongly UV-irradiated gas

NASA Astrophysics Data System (ADS)

Cuadrado, S.; Goicoechea, J. R.; Cernicharo, J.; Fuente, A.; Pety, J.; Tercero, B.

2017-07-01

We investigate the presence of complex organic molecules (COMs) in strongly UV-irradiated interstellar molecular gas. We have carried out a complete millimetre (mm) line survey using the IRAM 30 m telescope towards the edge of the Orion Bar photodissociation region (PDR), close to the H2 dissociation front, a position irradiated by a very intense far-UV (FUV) radiation field. These observations have been complemented with 8.5'' resolution maps of the H2CO JKa,Kc = 51,5 → 41,4 and C18O J = 3 → 2 emission at 0.9 mm. Despite being a harsh environment, we detect more than 250 lines from COMs and related precursors: H2CO, CH3OH, HCO, H2CCO, CH3CHO, H2CS, HCOOH, CH3CN, CH2NH, HNCO, H213CO, and HC3N (in decreasing order of abundance). For each species, the large number of detected lines allowed us to accurately constrain their rotational temperatures (Trot) and column densities (N). Owing to subthermal excitation and intricate spectroscopy of some COMs (symmetric- and asymmetric-top molecules such as CH3CN and H2CO, respectively), a correct determination of N and Trot requires building rotational population diagrams of their rotational ladders separately. The inferred column densities are in the 1011-1013 cm-2 range. We also provide accurate upper limit abundances for chemically related molecules that might have been expected, but are not conclusively detected at the edge of the PDR (HDCO, CH3O, CH3NC, CH3CCH, CH3OCH3, HCOOCH3, CH3CH2OH, CH3CH2CN, and CH2CHCN). A non-thermodynamic equilibrium excitation analysis for molecules with known collisional rate coefficients suggests that some COMs arise from different PDR layers but we cannot resolve them spatially. In particular, H2CO and CH3CN survive in the extended gas directly exposed to the strong FUV flux (Tk = 150-250 K and Td≳ 60 K), whereas CH3OH only arises from denser and cooler gas clumps in the more shielded PDR interior (Tk = 40-50 K). The non-detection of HDCO towards the PDR edge is consistent with the

(F)UV Spectral Analysis of Hot, Hydrogen-Rich Central Stars of Planetary Nebulae

NASA Astrophysics Data System (ADS)

Ziegler, M.; Rauch, T.; Werner, K.; Kruk, J. W.

2010-11-01

Metal abundances of CSPNe are not well known although they provide important constraints on AGB nucleosynthesis. We aim to determine metal abundances of two hot, hydrogen-rich CSPNe (namely of A35 and NGC3587, the latter also known as M97 or the Owl Nebula) and to derive Teff and log g precisely from high-resolution, high-S/N (far-) ultraviolet observations obtained with FUSE and HST/STIS. For this purpose, we utilize NLTE model atmospheres calculated with TMAP, the Tübingen Model Atmosphere Package. Due to strong line absorption of the ISM, simultaneous modeling of interstellar features has become a standard tool in our analyses. We present preliminary results, demonstrating the importance of combining stellar and interstellar models, in order to clearly identify and measure the strengths of strategic photospheric lines.

Quantitative analysis of ions in spring water in three different areas of Hyogo Prefecture in Japan by far ultraviolet spectroscopy.

PubMed

Mitsuoka, Motoki; Shinzawa, Hideyuki; Morisawa, Yusuke; Kariyama, Naomi; Higashi, Noboru; Tsuboi, Motohiro; Ozaki, Yukihiro

2011-01-01

Far-ultraviolet (FUV) spectra in the 190-300 nm region were measured for spring water in Awaji-Akashi area, Tamba area and Rokko-Arima area in Hyogo Prefecture, Japan, these areas have quite different geology features. The spectra of the spring water in the Awaji-Akashi area can be divided into two groups: the spring water samples containing large amounts of NO(3)(-) and/or Cl(-), and those containing only small amounts of NO(3)(-) and Cl(-). The former shows a saturated band below 190 nm due to NO(3)(-) and/or Cl(-). These two types of spectra correspond to different lithological areas: sedimentary lithology near the sea shore containing many ions in the seawater and gravitic lithology far from the sea side, in the Awaji-Akashi area. The spring water from the Tamba area, which is far from the sea, contains relatively small amounts of NO(3)(-) and Cl(-); it does not yield a strong band in the region observed. The FUV spectra of three of four kinds of spring water samples in the Arima Hotspring show characteristic spectral patterns. They are quite different from the spectra of the spring water samples of the Rokko area. Calibration models were developed for NO(3)(-), Cl(-), SO(4)(2-), Na(+), and Mg(2+) in the nine kinds of spring water collected in the Awaji-Akashi area, Tamba, and Rokko-Arima area by using univariate analysis of the first derivative spectra and the actual values obtained by ion chromatography. NO(3)(-) yields the best results: correlation coefficient of 0.999 and standard deviation of 0.09 ppm with the wavelength of 212 nm. Cl(-) also gives good results: correlation coefficient of 0.993 and standard deviation of 0.5 ppm with the wavelength of 192 nm.

The Far Ultraviolet M-dwarf Evolution Survey (FUMES): Overview and Initial Results

NASA Astrophysics Data System (ADS)

Pineda, J. Sebastian; France, Kevin; Youngblood, Allison

2018-01-01

M-dwarf stars are prime targets for exoplanet searches because of their close proximity and favorable properties for both planet detection and characterization, with current searches around these targets having already discovered several Earth-sized planets within their star’s habitable zones. However, the atmospheric characterization and potential habitability of these exoplanetary systems depends critically on the high-energy stellar radiation environment from X-rays to NUV. Strong radiation at these energies can lead to atmospheric mass loss and is a strong driver of photochemistry in planetary atmospheres. Recently, the MUSCLES Treasury Survey provided the first comprehensive assessment of the high-energy radiation field around old, planet hosting M-dwarfs. However, the habitability and potential for such exoplanetary atmospheres to develop life also depends on the evolution of the atmosphere and hence the evolution of the incident radiation field. The strong high-energy spectrum of young M-dwarfs can have devastating consequences for the potential habitability of a given system. We, thus, introduce the Far Ultraviolet M-dwarf Evolution Survey (FUMES), a new HST-STIS observing campaign targeting 10 early-mid M dwarfs with known rotation periods, including 6 targets with known ages, to assess the evolution of the FUV radiation, including Lyα, of M-dwarf stars with stellar rotation period. We present the initial results of our survey characterizing the FUV emission features of our targets and the implications of our measurements for the evolution of the entire high-energy radiation environment around M-dwarfs from youth to old age.

Binarity and Accretion in AGB Stars: HST/STIS Observations of UV Flickering in Y Gem

NASA Astrophysics Data System (ADS)

Sahai, R.; Sánchez Contreras, C.; Mangan, A. S.; Sanz-Forcada, J.; Muthumariappan, C.; Claussen, M. J.

2018-06-01

Binarity is believed to dramatically affect the history and geometry of mass loss in AGB and post-AGB stars, but observational evidence of binarity is sorely lacking. As part of a project to search for hot binary companions to cool AGB stars using the GALEX archive, we discovered a late-M star, Y Gem, to be a source of strong and variable UV and X-ray emission. Here we report UV spectroscopic observations of Y Gem obtained with the Hubble Space Telescope that show strong flickering in the UV continuum on timescales of ≲20 s, characteristic of an active accretion disk. Several UV lines with P-Cygni-type profiles from species such as Si IV and C IV are also observed, with emission and absorption features that are red- and blueshifted by velocities of ∼500 {km} {{{s}}}-1 from the systemic velocity. Our model for these (and previous) observations is that material from the primary star is gravitationally captured by a companion, producing a hot accretion disk. The latter powers a fast outflow that produces blueshifted features due to the absorption of UV continuum emitted by the disk, whereas the redshifted emission features arise in heated infalling material from the primary. The outflow velocities support a previous inference by Sahai et al. that Y Gem’s companion is a low-mass main-sequence star. Blackbody fitting of the UV continuum implies an accretion luminosity of about 13 L ⊙, and thus a mass-accretion rate >5 × 10‑7 M ⊙ yr‑1 we infer that Roche-lobe overflow is the most likely binary accretion mode for Y Gem.

Elucidation of the electronic states in polyethylene glycol by attenuated Total reflectance spectroscopy in the far-ultraviolet region

NASA Astrophysics Data System (ADS)

Ueno, Nami; Wakabayashi, Tomonari; Morisawa, Yusuke

2018-05-01

We measured the attenuated total reflectance-far ultraviolet (ATR-FUV) spectra of poly(ethylene glycol) (PEG; average molecular weights of 200, 300, and 400) and related materials in the liquid state in the 145-200-nm wavelength region. For appropriately assigning the absorption bands, we also performed theoretical simulation of the unit-number dependent electronic spectra. The FUV spectra of PEGs contain three bands, which are assigned to the transitions between n(CH2OCH2)-3s Rydberg state (176 nm), n(CH2OCH2)-3p Rydberg state (163 nm), and n(OH)-3p Rydberg state (153 nm). Since the contribution of n(OH) decreases compared to n(CH2OCH2) with increase in the number of units, the ratios of the molar absorption coefficients, ε, at 153 nm relative to 163 nm, decrease. On the other hand, the ratio of ε at 176 nm to that at 163 nm increases with increase in the number of units, because of the difference in the number of unoccupied orbitals in the transitions. The calculated results suggest that n orbitals form two electronic bands. In the upper band, the electrons expand over the ether chain, whereas in the lower band, the electrons are localized in the terminal OH in the PEGs.

Release of the gPhoton Database of GALEX Photon Events

NASA Astrophysics Data System (ADS)

Fleming, Scott W.; Million, Chase; Shiao, Bernie; Tucker, Michael; Loyd, R. O. Parke

2016-01-01

The GALEX spacecraft surveyed much of the sky in two ultraviolet bands between 2003 and 2013 with non-integrating microchannel plate detectors. The Mikulski Archive for Space Telescopes (MAST) has made more than one trillion photon events observed by the spacecraft available, stored as a 130 TB database, along with an open-source, python-based software package to query this database and create calibrated lightcurves or images from these data at user-defined spatial and temporal scales. In particular, MAST users can now conduct photometry at the intra-visit level (timescales of seconds and minutes). The software, along with the fully populated database, was officially released in Aug. 2015, and improvements to both software functionality and data calibration are ongoing. We summarize the current calibration status of the gPhoton software, along with examples of early science enabled by gPhoton that include stellar flares, AGN, white dwarfs, exoplanet hosts, novae, and nearby galaxies.

A SNAPshot of the FUV (1320 - 1460 A) Spectrum of Lambda Vel (K4Ib-II)

NASA Technical Reports Server (NTRS)

Carpenter, Kenneth G.

2010-01-01

The FUV spectrum (l330-1460A) of the K4Ib-II supergiant Lambda Vel was observed with the Cosmic Origins Spectrograph (COS) on HST, as part of the Ayres and Redfield Cycle 17 SNAP program "SNAPing Coronal Iron". This spectrum covers a region not previously seen in Lambda Vel at high resolution and reveals a rich emission-line spectrum superposed on a bright continuum, with contributions from a variety of atomic and molecular sources. Evidence of the stellar wind is seen in the P Cygni profiles of selected lines and the results of fluorescence processes are visible throughout the region. The spectrum has remarkable similarities to that of Alpha Boo (K1.5 III), but significant differences as well, including substantial FUV continuum emission, reminiscent of the M2 lab supergiant Alpha Ori, but minus the CO fundamental absorption bands seen in the latter star. However, fluoresced CO emission is present and strong, as in the K-giant stars Alpha Boo and Alpha Tau (K5 III). We present the details of this spectrum, in comparison to stars of similar temperature or luminosity and discuss the implications for the structure of and the radiative processes active in, the outer atmospheres of these stars.

SUMO: Solar Ultraviolet Monitor and Ozone Nanosatellite

NASA Astrophysics Data System (ADS)

Damé, L.; Meftah, M.; Irbah, A.; Hauchecorne, A.; Keckhut, P.; Sarkissian, A.; Godin-Beekman, S.; Rogers, D. J.; Bove, P.; Lagage, P. O.; DeWitte, S.

2014-12-01

SUMO is an innovative proof-of-concept nanosatellite aiming to measure on the same platform the different components of the Earth radiation budget (ERB), the solar energy input and the energy reemitted at the top of the Earth atmosphere, with a particular focus on the far UV (FUV) part of the spectrum and on the ozone layer. The FUV is the only wavelength band with energy absorbed in the high atmosphere (stratosphere), in the ozone (Herzberg continuum, 200-220 nm) and oxygen bands, and its high variability is most probably at the origin of a climate influence (UV affects stratospheric dynamics and temperatures, altering interplanetary waves and weather patterns both poleward and downward to the lower stratosphere and tropopause). A simultaneous observation of incoming FUV and ozone production would bring an invaluable information on this process of solar-climate forcing. Space instruments have already measured the different components of the ERB but this is the first time that all instruments will operate on the same platform. This characteristic by itself guarantees original scientific results. SUMO is a 3.6 kg, 3W, 10x10x30 cm3 nanosatellite ("3U"), with a "1U" payload of <1 kg and 1 W. 5 instruments: an ozone meter, a FUV measure at 215 nm, 2 radiometers (0.2 - 3 & 0.2 - 40 µm) and a bolometer. Orbit is polar, Sun-synchronous, ~600 km, since a further challenge are relations between solar UV variability and stratospheric ozone on Arctic and Antarctic regions. Mission is expected to last 1 to 2 years. SUMO definition has been completed (platform and payload AIT are possible in 24 months). SUMO is proposed for the nanosatellite program of Polytechnic School and CNES (following QB50) for a flight in 2018. Follow-up is 2 fold: on one part more complete measurements using SUMO miniaturized instruments on a larger satellite; on the other part, increase of the coverage in local time and latitude using a constellation of SUMO nanosatellites around the Earth to further

The gaseous debris disk of the white dwarf SDSS J1228+1040. HST/COS search for far-ultraviolet signatures

NASA Astrophysics Data System (ADS)

Hartmann, S.; Nagel, T.; Rauch, T.; Werner, K.

2016-09-01

Context. Gaseous and dust debris disks around white dwarfs (WDs) are formed from tidally disrupted planetary bodies. This offers an opportunity to determine the composition of exoplanetary material by measuring element abundances in the accreting WD's atmosphere. A more direct way to do this is through spectral analysis of the disks themselves. Aims: Currently, the number of chemical elements detected through disk emission-lines is smaller than that of species detected through lines in the WD atmospheres. We assess the far-ultraviolet (FUV) spectrum of one well-studied object (SDSS J122859.93+104032.9) to search for disk signatures at wavelengths < 1050 Å, where the broad absorption lines of the Lyman series effectively block the WD photospheric flux. In addition, we investigate the Ca II infrared triplet (IRT) line profiles to constrain disk geometry and composition. Methods: We performed FUV observations (950-1240 Å) with the Hubble Space Telescope/Cosmic Origins Spectrograph and used archival optical spectra. We compared them with non-local thermodynamic equilibrium model spectra. Results: No disk emission-lines were detected in the FUV spectrum, indicating that the disk effective temperature is Teff ≈ 5000 K. The long-time variability of the Ca II IRT was reproduced with a precessing disk model of bulk Earth-like composition, having a surface mass density of 0.3 g cm-2 and an extension from 55 to 90 WD radii. The disk has a spiral shape that precesses with a period of approximately 37 years, confirming previous results. Based on observations with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26666.

Far Ultraviolet Spectroscopy of Seven Nova-Like Variables

NASA Astrophysics Data System (ADS)

Mizusawa, Trisha; Merritt, Jason; Ballouz, Ronald-Louis; Bonaro, Michael; Foran, Sean; Plumberg, Christopher; Stewart, Heather; Wiley, Trayer; Sion, Edward M.

2010-03-01

We present the results of a multicomponent synthetic spectral analysis of the archival far ultraviolet spectra of several key nova-like variables including members of the SW Sex, RW Tri, UX UMa, and VY Scl subclasses: KR Aur, RW Tri, V825 Her, V795 Her, BP Lyn, V425 Cas, and HL Aqr. Accretion rates as well as the possible flux contribution of the accreting white dwarf are included in our analysis. Except for RW Tri, which has a reliable trigonometric parallax, we computed the distances to the nova-like systems using the method of Knigge. Our analysis of seven archival IUE spectra of RW Tri at its parallax distance of 341 pc consistently indicates a low mass (˜0.4 M⊙) white dwarf and an average accretion rate, . For KR Aur, we estimate that the white dwarf has Teff = 29,000 ± 2000 K, log g = 8.4, and contributes 18% of the far-UV flux, while an accretion disk with accretion rate at an inclination of 41° contributes the remainder. We find that an accretion disk dominates the far-UV spectrum of V425 Cas but a white dwarf contributes nonnegligibly with approximately 18% of the far-UV flux. For the two high state nova-likes, HL Aqr and V825 Her, their accretion disks totally dominate with and 3 × 10-9 M⊙ yr-1, respectively. For BP Lyn we find while for V795 Her, we find an accretion rate of . We discuss the implications of our results for the evolutionary status of nova-like variables.

HST/COS Far-ultraviolet Spectroscopic Analysis of U Geminorum Following a Wide Outburst

NASA Astrophysics Data System (ADS)

Godon, Patrick; Shara, Michael M.; Sion, Edward M.; Zurek, David

2017-12-01

We used the Cosmic Origins Spectrograph (COS) on the Hubble Space Telescope (HST) to obtain a series of four far-ultraviolet (FUV; 915-2148 Å) spectroscopic observations of the prototypical dwarf nova U Geminorum during its cooling following a two-week outburst. Our FUV spectral analysis of the data indicates that the white dwarf (WD) cools from a temperature of ˜41,500 K, 15 days after the peak of the outburst, to ˜36,250 K, 56 days after the peak of the outburst, assuming a massive WD (log(g) = 8.8) and a distance of 100.4 ± 3.7 pc. These results are self-consistent with a ˜1.1 M ⊙ WD with a 5000 ± 200 km radius. The spectra show absorption lines of H I, He II, C II III IV, N III IV, O VI, S IV, Si II III IV, Al III, Ar III, and Fe II, but no emission features. We find suprasolar abundances of nitrogen, confirming the anomalous high N/C ratio. The FUV light curve reveals a ±5% modulation with the orbital phase, showing dips near phases 0.25 and ˜0.75, where the spectra exhibit an increase in the depth of some absorption lines and in particular strong absorption lines from Si II, Al III, and Ar III. The phase dependence we observe is consistent with material overflowing the disk rim at the hot spot, reaching a maximum elevation near phase 0.75, falling back at smaller radii near phase 0.5 where it bounces off the disk surface, and again rising above the disk near phase ˜0.25. There is a large scatter in the absorption lines’ velocities, especially for the silicon lines, while the carbon lines seem to match more closely the orbital velocity of the WD. This indicates that many absorption lines are affected by—or form in—the overflowing stream material veiling the WD, making the analysis of the WD spectra more difficult. Based on observations made with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by AURA, Inc., under NASA contract NAS 5-26555.

Dwarf galaxies in the coma cluster: Star formation properties and evolution

NASA Astrophysics Data System (ADS)

Hammer, Derek M.

The infall regions of galaxy clusters are unique laboratories for studying the impact of environment on galaxy evolution. This intermediate region links the low-density field environment and the dense core of the cluster, and is thought to host recently accreted galaxies whose star formation is being quenched by external processes associated with the cluster. In this dissertation, we measure the star formation properties of galaxies at the infall region of the nearby rich cluster of galaxies, Coma. We rely primarily on Ultraviolet (UV) data owing to its sensitivity to recent star formation and we place more emphasis on the properties of dwarf galaxies. Dwarf galaxies are good tracers of external processes in clusters but their evolution is poorly constrained as they are intrinsically faint and hence more challenging to detect. We make use of deep GALEX far-UV and near-UV observations at the infall region of the Coma cluster. This area of the cluster has supporting photometric coverage at optical and IR wavelengths in addition to optical spectroscopic data that includes deep redshift coverage of dwarf galaxies in Coma. Our GALEX observations were the deepest exposures taken for a local galaxy cluster. The depth of these images required alternative data analysis techniques to overcome systematic effects that limit the default GALEX pipeline analysis. Specifically, we used a deblending method that improved detection efficiency by a factor of ˜2 and allowed reliable photometry a few magnitudes deeper than the pipeline catalog. We performed deep measurements of the total UV galaxy counts in our field that were used to measure the source confusion limit for crowded GALEX fields. The star formation properties of Coma members were studied for galaxies that span from starbursts to passive galaxies. Star-forming galaxies in Coma tend to have lower specific star formation rates, on average, as compared to field galaxies. We show that the majority of these galaxies are likely

Imbalanced Learning for RR Lyrae Stars Based on SDSS and GALEX Databases

NASA Astrophysics Data System (ADS)

Zhang, Jingyi; Zhang, Yanxia; Zhao, Yongheng

2018-03-01

We apply machine learning and Convex-Hull algorithms to separate RR Lyrae stars from other stars like main-sequence stars, white dwarf stars, carbon stars, CVs, and carbon-lines stars, based on the Sloan Digital Sky Survey and Galaxy Evolution Explorer (GALEX). In low-dimensional spaces, the Convex-Hull algorithm is applied to select RR Lyrae stars. Given different input patterns of (u ‑ g, g ‑ r), (g ‑ r, r ‑ i), (r ‑ i, i ‑ z), (u ‑ g, g ‑ r, r ‑ i), (g ‑ r, r ‑ i, i ‑ z), (u ‑ g, g ‑ r, i ‑ z), and (u ‑ g, r ‑ i, i ‑ z), different convex hulls can be built for RR Lyrae stars. Comparing the performance of different input patterns, u ‑ g, g ‑ r, i ‑ z is the best input pattern. For this input pattern, the efficiency (the fraction of true RR Lyrae stars in the predicted RR Lyrae sample) is 4.2% with a completeness (the fraction of recovered RR Lyrae stars in the whole RR Lyrae sample) of 100%, increases to 9.9% with 97% completeness and to 16.1% with 53% completeness by removing some outliers. In high-dimensional spaces, machine learning algorithms are used with input patterns (u ‑ g, g ‑ r, r ‑ i, i ‑ z), (u ‑ g, g ‑ r, r ‑ i, i ‑ z, r), (NUV ‑ u, u ‑ g, g ‑ r, r ‑ i, i ‑ z), and (NUV ‑ u, u ‑ g, g ‑ r, r ‑ i, i ‑ z, r). RR Lyrae stars, which belong to the class of interest in our paper, are rare compared to other stars. For the highly imbalanced data, cost-sensitive Support Vector Machine, cost-sensitive Random Forest, and Fast Boxes is used. The results show that information from GALEX is helpful for identifying RR Lyrae stars, and Fast Boxes is the best performer on the skewed data in our case.

Ultraviolet Spectroscopy of the Surfaces of the Inner Icy Saturnian Satellites

NASA Astrophysics Data System (ADS)

Hendrix, A. R.; Hansen, C. J.

2008-12-01

The Cassini mission has provided a unique opportunity to make high-resolution, multi-spectral measurements of Saturn's icy moons, to investigate their surface compositions, processes and evolution. Here we present results from the Ultraviolet Imaing Spectrograph (UVIS). This instrument allows for the first measurements of the icy satellites in the extreme ultraviolet (EUV) to far-ultraviolet (FUV) wavelength range. The icy satellites of the Saturn system exhibit a remarkable amount of variability: Dark, battered Phoebe orbiting at a distant 200 RS, black-and-white Iapetus, the wispy streaks of Dione, cratered Rhea and Mimas, bright Tethys and geologically active Enceladus. Phoebe, Iapetus and Hyperion all orbit largely outside Saturn's magnetosphere, while the inner icy satellites Mimas, Enceladus, Dione Tethys and Rhea all orbit within the magnetosphere. Furthermore, the inner icy satellites all orbit within the E-ring - so the extent of exogenic effects on these icy satellites is wide-ranging. We present an overview of UVIS results from Tethys, Dione, Mimas, Enceladus and Rhea, focusing on surface investigations. We expect that the UV signatures of these icy satellites are strongly influenced not only by their water ice composition, but by external effects and magnetospheric environments. We study the FUV reflectance spectra to learn about the surface composition, map out water ice grain size variations, investigate effects of coating by E-ring grains, examine disk-resolved and hemispheric compositional and brightness variations, and investigate the presence of radiation products. This is new work: FUV spectra of surfaces have not been well-studied in the past. Spectra of the inner icy moons have been used to better develop spectral models, to further understand existing lab data of water ice and to help with understanding instrument performance. Analysis is challenged by a lack of laboratory data in this wavelength region, but intriguing results are being found

VizieR Online Data Catalog: Far-UV spectral atlas of O-type stars (Smith, 2012)

NASA Astrophysics Data System (ADS)

Smith, M. A.

2012-10-01

In this paper, we present a spectral atlas covering the wavelength interval 930-1188Å for O2-O9.5 stars using Far-Ultraviolet Spectroscopic Explorer archival data. The stars selected for the atlas were drawn from three populations: Galactic main-sequence (classes III-V) stars, supergiants, and main-sequence stars in the Magellanic Clouds, which have low metallicities. For several of these stars, we have prepared FITS files comprised of pairs of merged spectra for user access via the Multimission Archive at Space Telescope (MAST). We chose spectra from the first population with spectral types O4, O5, O6, O7, O8, and O9.5 and used them to compile tables and figures with identifications of all possible atmospheric and interstellar medium lines in the region 949-1188Å. Our identified line totals for these six representative spectra are 821 (500), 992 (663), 1077 (749), 1178 (847), 1359 (1001), and 1798 (1392) lines, respectively, where the numbers in parentheses are the totals of lines formed in the atmospheres, according to spectral synthesis models. The total number of unique atmospheric identifications for the six main-sequence O-star template spectra is 1792, whereas the number of atmospheric lines in common to these spectra is 300. The number of identified lines decreases toward earlier types (increasing effective temperature), while the percentages of "missed" features (unknown lines not predicted from our spectral syntheses) drop from a high of 8% at type B0.2, from our recently published B-star far-UV atlas (Cat. J/ApJS/186/175), to 1%-3% for type O spectra. The percentages of overpredicted lines are similar, despite their being much higher for B-star spectra. (4 data files).

Exploring Mercury's Surface in UltraViolet from Orbit

NASA Astrophysics Data System (ADS)

Izenberg, N.

2017-12-01

The MESSENGER Mission's Ultraviolet and Visible Spectrometer (UVVS) component of its Mercury Atmosphere and Surface Composition Spectrometer (MASCS) instrument obtained approximately 4600 point observations of Mercury's surface in middle ultraviolet (MUV; 210 nm - 300 nm) and far ultraviolet (FUV; 119.1 - 122.5 nm and 129.2 - 131.5 nm) wavelengths over the course of its orbital mission, mostly in Mercury's southern hemisphere. Given the very low (<1 to 2 wt %) average abundance of iron in the silicates of Mercury observed by multiple MESSENGER instruments, the near- to middle-ultraviolet wavelengths encompassing the oxygen metal charge transfer band (<400 nm), which is more sensitive to the presence of iron than the classic 1 micron absorption band, provides potentially useful additional compositional insight into the top layer of Mercury's regolith. The presence of nano- and microphase carbon also has potentially significant expression in the ultraviolet, and the interplay and variation between carbon and iron in mercury surface materials is an active area of investigation. Analysis of middle-UV surface reflectance and parameters appear to support the presence of varying amounts of carbon in different spectral or geologic units on Mercury. Far-UV reflectance data is currently under-utilized, but analysis of lunar surface by the Lunar Reconnaissance Orbiter (LRO) Lyman Alpha Mapping Project (LAMP) indicate that the data are sensitive to both composition and space weathering. The far-UV reflectance from MASCS may provide similar information for the Mercury surface, complementing results from longer wavelengths. MESSENGER data products for surface reflectance include middle-UV reflectance spectra, ultraviolet far-UV reflectance values, combined middle-UV through near-infrared spectra (210 nm - 1450 nm), a global `spectral cube' of near-UV to near-IR, and an upcoming UV spectral cube.

Global Increase in UV Irradiance during the Past 30 Years (1979-2008) Estimated from Satellite Data

NASA Technical Reports Server (NTRS)

Herman, Jay R.

2010-01-01

Zonal average ultraviolet irradiance (flux ultraviolet, F(sub uv)) reaching the Earth's surface has significantly increased since 1979 at all latitudes except the equatorial zone. Changes are estimated in zonal average F(sub uv) caused by ozone and cloud plus aerosol reflectivity using an approach based on Beer's law for monochromatic and action spectrum weighted irradiances. For four different cases, it is shown that Beer's Law leads to a power law form similar to that applied to erythemal action spectrum weighted irradiances. Zonal and annual average increases in F(sub uv) were caused by decreases in ozone amount from 1979 to 1998. After 1998, midlatitude annual average ozone amounts and UV irradiance levels have been approximately constant. In the Southern Hemisphere, zonal and annual average UV increase is partially offset by tropospheric cloud and aerosol transmission decreases (hemispherical dimming), and to a lesser extent in the Northern Hemisphere. Ozone and 340 nm reflectivity changes have been obtained from multiple joined satellite time series from 1978 to 2008. The largest zonal average increases in F(sub uv) have occurred in the Southern Hemisphere. For clear-sky conditions at 50 S, zonal average F(sub uv) changes are estimated (305 nm, 23%; erythemal, 8.5%; 310 nm, 10%; vitamin D production, 12%). These are larger than at 50 N (305 nm, 9%; erythemal, 4%; 310 nm, 4%; vitamin D production, 6%). At the latitude of Buenos Aires, Argentina (34.6 S), the clear-sky Fuv increases are comparable to the increases near Washington, D. C. (38.9 N): 305 nm, 9% and 7%; erythemal, 6% and 4%; and vitamin D production, 7% and 5%, respectively.

Time-Resolved Ultraviolet Spectroscopy of the M-Dwarf GJ 876 Exoplanetary System

NASA Technical Reports Server (NTRS)

France, Kevin; Linsky, Jeffrey L.; Tian, Feng; Froning, Cynthia S.; Roberge, Aki

2012-01-01

Extrasolar planets orbiting M-stars may represent our best chance to discover habitable worlds in the coming decade. The ultraviolet spectrum incident upon both Earth-like and Jovian planets is critically important for proper modeling of their atmospheric heating and chemistry. In order to provide more realistic inputs for atmospheric models of planets orbiting low-mass stars, we present new near- and far-ultraviolet (NUV and FUV) spectroscopy of the M-dwarf exoplanet host GJ 876 (U4V). Using the COS and STIS spectrographs aboard the Hubble Space Telescope, we have measured the 1150 - 3140 Ang. spectrum of GJ 876. We have reconstructed the stellar H I Ly-alpha emission line profile, and find that the integrated Ly-apha flux is roughly equal to the rest of the integrated flux (1150 - 1210 Ang + 1220 - 3140 Ang) in the entire ultraviolet bandpass (F(Ly-alpha)/F(FUV+NUV) approximately equals 0.7). This ratio is approximately 2500 x greater than the solar value. We describe the ultraviolet line spectrum and report surprisingly strong fluorescent emission from hot H2 (T(H2) > 2000 K). We show the light-curve of a chromospheric + transition region flare observed in several far-UV emission lines, with flare/ quiescent flux ratios :2: 10. The strong FUV radiation field of an M-star (and specifically Ly-alpha) is important for determining the abundance of O2 - and the formation of biomarkers - in the lower atmospheres of Earth-like planets in the habitable zones of low-mass stars.

White dwarf variability with gPhoton: pulsators

NASA Astrophysics Data System (ADS)

Tucker, Michael A.; Fleming, Scott W.; Pelisoli, Ingrid; Romero, Alejandra; Bell, Keaton J.; Kepler, S. O.; Caton, Daniel B.; Debes, John; Montgomery, Michael H.; Thompson, Susan E.; Koester, Detlev; Million, Chase; Shiao, Bernie

2018-04-01

We present results from a search for short time-scale white dwarf variability using gPhoton, a time-tagged data base of GALEX photon events and associated software package. We conducted a survey of 320 white dwarf stars in the McCook-Sion catalogue, inspecting each for photometric variability with particular emphasis on variability over time-scales less than ˜30 min. From that survey, we present the discovery of a new pulsating white dwarf: WD 2246-069. A Ca II K line is found in archival ESO spectra and an IR excess is seen in WISE W1 and W2 bands. Its independent modes are identified in follow-up optical photometry and used to model its interior structure. Additionally, we detect UV pulsations in four previously known pulsating ZZ Ceti-type (DAVs). Included in this group is the simultaneous fitting of the pulsations of WD 1401-147 in optical, near-ultraviolet and far-ultraviolet bands using nearly concurrent Whole Earth Telescope and GALEX data, providing observational insight into the wavelength dependence of white dwarf pulsation amplitudes.

The Resolved Stellar Populations in the LEGUS Galaxies1

NASA Astrophysics Data System (ADS)

Sabbi, E.; Calzetti, D.; Ubeda, L.; Adamo, A.; Cignoni, M.; Thilker, D.; Aloisi, A.; Elmegreen, B. G.; Elmegreen, D. M.; Gouliermis, D. A.; Grebel, E. K.; Messa, M.; Smith, L. J.; Tosi, M.; Dolphin, A.; Andrews, J. E.; Ashworth, G.; Bright, S. N.; Brown, T. M.; Chandar, R.; Christian, C.; Clayton, G. C.; Cook, D. O.; Dale, D. A.; de Mink, S. E.; Dobbs, C.; Evans, A. S.; Fumagalli, M.; Gallagher, J. S., III; Grasha, K.; Herrero, A.; Hunter, D. A.; Johnson, K. E.; Kahre, L.; Kennicutt, R. C.; Kim, H.; Krumholz, M. R.; Lee, J. C.; Lennon, D.; Martin, C.; Nair, P.; Nota, A.; Östlin, G.; Pellerin, A.; Prieto, J.; Regan, M. W.; Ryon, J. E.; Sacchi, E.; Schaerer, D.; Schiminovich, D.; Shabani, F.; Van Dyk, S. D.; Walterbos, R.; Whitmore, B. C.; Wofford, A.

2018-03-01

The Legacy ExtraGalactic UV Survey (LEGUS) is a multiwavelength Cycle 21 Treasury program on the Hubble Space Telescope. It studied 50 nearby star-forming galaxies in 5 bands from the near-UV to the I-band, combining new Wide Field Camera 3 observations with archival Advanced Camera for Surveys data. LEGUS was designed to investigate how star formation occurs and develops on both small and large scales, and how it relates to the galactic environments. In this paper we present the photometric catalogs for all the apparently single stars identified in the 50 LEGUS galaxies. Photometric catalogs and mosaicked images for all filters are available for download. We present optical and near-UV color–magnitude diagrams for all the galaxies. For each galaxy we derived the distance from the tip of the red giant branch. We then used the NUV color–magnitude diagrams to identify stars more massive than 14 M ⊙, and compared their number with the number of massive stars expected from the GALEX FUV luminosity. Our analysis shows that the fraction of massive stars forming in star clusters and stellar associations is about constant with the star formation rate. This lack of a relation suggests that the timescale for evaporation of unbound structures is comparable or longer than 10 Myr. At low star formation rates this translates to an excess of mass in clustered environments as compared to model predictions of cluster evolution, suggesting that a significant fraction of stars form in unbound systems. Based on observations with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by AURA Inc., under NASA contract NAS 5-26555.

The peculiar optical-UV X-ray spectra of the X-ray weak quasar PG 0043+039

NASA Astrophysics Data System (ADS)

Kollatschny, W.; Schartel, N.; Zetzl, M.; Santos-Lleó, M.; Rodríguez-Pascual, P. M.; Ballo, L.; Talavera, A.

2016-01-01

Context. The object PG 0043+039 has been identified as a broad absorption line (BAL) quasar based on its UV spectra. However, this optical luminous quasar has not been detected before in deep X-ray observations, making it the most extreme X-ray weak quasar known today. Aims: This study aims to detect PG 0043+039 in a deep X-ray exposure. The question is what causes the extreme X-ray weakness of PG 0043+039? Does PG 0043+039 show other spectral or continuum peculiarities? Methods: We took simultaneous deep X-ray spectra with XMM-Newton, far-ultraviolet (FUV) spectra with the Hubble Space Telescope (HST), and optical spectra of PG 0043+039 with the Hobby-Eberly Telescope (HET) and Southern African Large Telescope (SALT) in July, 2013. Results: We have detected PG 0043+039 in our X-ray exposure taken in 2013. We presented our first results in a separate paper (Kollatschny et al. 2015). PG 0043+039 shows an extreme αox gradient (αox = -2.37). Furthermore, we were able to verify an X-ray flux of this source in a reanalysis of the X-ray data taken in 2005. At that time, it was fainter by a factor of 3.8 ±0.9 with αox = -2.55. The X-ray spectrum is compatible with a normal quasar power-law spectrum (Γ = 1.70-0.45+0.57) with moderate intrinsic absorption (NH = 5.5-3.9+6.9 × 1021 cm-2) and reflection. The UV/optical flux of PG 0043+039 has increased by a factor of 1.8 compared to spectra taken in the years 1990-1991. The FUV spectrum is highly peculiar and dominated by broad bumps besides Lyα. There is no detectable Lyman edge associated with the BAL absorbing gas seen in the CIV line. PG 0043+039 shows a maximum in the overall continuum flux at around λ ≈ 2500 Å in contrast to most other AGN where the maximum is found at shorter wavelengths. All the above is compatible with an intrinsically X-ray weak quasar, rather than an absorbed X-ray emission. Besides strong FeII multiplets and broad Balmer and HeI lines in the optical band we only detect a narrow [O II

A study of the impact of the Space Shuttle environment on faint far-UV geophysical and astronomical phenomena

NASA Technical Reports Server (NTRS)

Lampton, Michael; Sasseen, Timothy P.; Wu, Xiaoyi; Bowyer, Stuart

1993-01-01

FAUST is a far ultraviolet (1400-1800 A) photon-counting imaging telescope featuring a wide field of view (7.6 deg) and a high sensitivity to extended emission features. During its flight as part of the ATLAS-1 payload aboard the STS-45 mission in March 1992, 19 deep-space nighttime viewing opportunities were utilized by FAUST. Here we report the observed fluxes and their time and space variations, and identify the signatures of postsunset airglow phenomena and Orbiter Vernier attitude control thruster firing events. We find that the Space Shuttle nighttime environment at 296 km altitude is often sufficiently dark to permit geophysical and astronomical UV observations down to levels on the order of 1000 photons/sq cm sr A sec, or 0.01 Rayleighs/A. We also find evidence for occasional geophysical fluxes of some tens or hundreds of Rayleighs in the upward-looking direction.

The UV Spectrum of Phobos as measured by MAVEN/IUVS

NASA Astrophysics Data System (ADS)

Chaffin, M.; Deighan, J.; Schneider, N. M.; Thiemann, E.; Stewart, I. F.; Jain, S.; Lo, D.; Crismani, M. M. J.; Stiepen, A.; Clarke, J. T.; Mayyasi, M.; Montmessin, F.; Holsclaw, G.; McClintock, B.; Epavier, F.; Jakosky, B. M.

2017-12-01

In late 2015, the Mars Atmosphere and Volatile Evolution (MAVEN) mission apoapsis was near the orbit of Phobos and the spacecraft had several close encounters with the moon. Using a specially designed imaging sequence, MAVEN's Imaging Ultraviolet Spectrograph (IUVS) was able to gather the first spectral images of the moon in the mid-ultraviolet. IUVS observed the trailing hemisphere of the moon, producing spectra useful for comparison with the leading hemisphere measurements of the Mariner 9 UV spectrometer and Mars Express SPICAM observations. IUVS shows the trailing side to be bluer than the leading side, potentially revealing differences in the space weathering history of the hemispheres. In addition, there is marginal evidence for an absorption feature longward of 300 nm, potentially produced by organic compounds. Due to short integration times, the FUV spectrum of the moon is limited to some reflectance signal at Lyman alpha, constraining the albedo at this wavelength and placing an upper limit on it elsewhere.

GAS MOTION STUDY OF Ly{alpha} EMITTERS AT z {approx} 2 USING FUV AND OPTICAL SPECTRAL LINES {sup ,}

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hashimoto, Takuya; Shimasaku, Kazuhiro; Nakajima, Kimihiko

2013-03-01

We present the results of Magellan/MMIRS and Keck/NIRSPEC spectroscopy for five Ly{alpha} emitters (LAEs) at z {approx_equal} 2.2 for which high-resolution FUV spectra from Magellan/MagE are available. We detect nebular emission lines including H{alpha} on the individual basis and low-ionization interstellar (LIS) absorption lines in a stacked FUV spectrum, and measure average offset velocities of the Ly{alpha} line, {Delta}v {sub Ly{alpha}}, and LIS absorption lines, {Delta}v {sub abs}, with respect to the systemic velocity defined by the nebular lines. For a sample of eight z {approx} 2-3 LAEs without active galactic nucleus from our study and the literature, we obtainmore » {Delta}v {sub Ly{alpha}} = 175 {+-} 35 km s{sup -1}, which is significantly smaller than that of Lyman-break Galaxies (LBGs), {Delta}v {sub Ly{alpha}} {approx_equal} 400 km s{sup -1}. The stacked FUV spectrum gives {Delta}v {sub abs} = -179 {+-} 73 km s{sup -1}, comparable to that of LBGs. These positive {Delta}v {sub Ly{alpha}} and negative {Delta}v {sub abs} suggest that LAEs also have outflows. In contrast to LBGs, however, the LAEs' {Delta}v {sub Ly{alpha}} is as small as |{Delta}v {sub abs}|, suggesting low neutral hydrogen column densities. Such a low column density with a small number of resonant scattering may cause the observed strong Ly{alpha} emission of LAEs. We find an anti-correlation between Ly{alpha} equivalent width (EW) and {Delta}v {sub Ly{alpha}} in a compilation of LAE and LBG samples. Although its physical origin is not clear, this anti-correlation result appears to challenge the hypothesis that a strong outflow, by means of a reduced number of resonant scattering, produces a large EW. If LAEs at z > 6 have similarly small {Delta}v {sub Ly{alpha}} values, constraints on the reionization history derived from the Ly{alpha} transmissivity may need to be revised.« less

Investigating early-type galaxy evolution with a multiwavelength approach. II. The UV structure of 11 galaxies with Swift-UVOT

NASA Astrophysics Data System (ADS)

Rampazzo, R.; Mazzei, P.; Marino, A.; Uslenghi, M.; Trinchieri, G.; Wolter, A.

2017-06-01

Context. GALEX detected a significant fraction of early-type galaxies, in particular S0s, showing far-UV bright structures, sometimes involving an entire galaxy out to its outskirts. These features suggest the presence of either recent ongoing and/or prolonged star formation episodes, shedding new light on the evolution of these systems. Aims: We aim at understanding the evolutionary path[s] of these early-type galaxies and the mechanisms at the origin of their UV-bright structures. We investigate with a multiwavelength approach the link between the inner and outer galaxy regions of a set of 11 early-type galaxies that were selected because of their nearly passive stage of evolution in the nuclear region. Methods: This paper, second of a series, focuses on the information coming from the comparison between UV features detected by Swift-UVOT, which trace recent star formation, and the galaxy optical structure, which maps older stellar populations. We performed a surface photometric study of these early-type galaxies, observed with the Swift-UVOT UV filters W2 2030 Å λ0, M2 2231 Å λ0, W1 2634 Å λ0 and the UBV bands. BVRI photometry from other sources in the literature was also used. Our integrated magnitude measurements were analyzed and compared with corresponding values in the literature. We characterize the overall galaxy structure that best fits the UV and optical luminosity profiles using a single Sérsic law. Results: The galaxies NGC 1366, NGC 1426, NGC 3818, NGC 3962, and NGC 7192 show featureless luminosity profiles. Excluding NGC 1366, which has a clear edge-on disk (n ≈ 1-2), and NGC 3818, the remaining three galaxies have Sérsic's indices n ≈ 3-4 in the optical and a lower index in the UV. Bright ring- or arm-like structures are revealed by UV images and luminosity profiles of NGC 1415, NGC 1533, NGC 1543, NGC 2685, NGC 2974, and IC 2006. The ring- or arm-like structures differ from galaxy to galaxy. Sérsic indices of UV profiles for these

Reconciling the Stellar and Nebular Spectra of High-redshift Galaxies

NASA Astrophysics Data System (ADS)

Steidel, Charles C.; Strom, Allison L.; Pettini, Max; Rudie, Gwen C.; Reddy, Naveen A.; Trainor, Ryan F.

2016-08-01

We present a combined analysis of rest-frame far-UV (FUV; 1000-2000 Å) and rest-frame optical (3600-7000 Å) composite spectra formed from very deep Keck/LRIS and Keck/MOSFIRE observations of a sample of 30 star-forming galaxies with z=2.40+/- 0.11, selected to be broadly representative of the full KBSS-MOSFIRE spectroscopic survey. Since the same massive stars are responsible for the observed FUV continuum and for the excitation of the observed nebular emission, a self-consistent stellar population synthesis model should simultaneously match the details of the FUV stellar+nebular continuum and—when inserted as the excitation source in photoionization models—predict all observed nebular emission line ratios. We find that only models including massive star binaries, having low stellar metallicity ({Z}* /{Z}⊙ ≃ 0.1) but relatively high nebular (ionized gas-phase) abundances ({Z}{{neb}}/{Z}⊙ ≃ 0.5), can successfully match all of the observational constraints. We show that this apparent discrepancy is naturally explained by highly super-solar O/Fe (≃ 4{--}5 {({{O}}/{Fe})}⊙ ), expected for a gas whose enrichment is dominated by the products of core-collapse supernovae. While O dominates the physics of the ionized gas (and thus the nebular emission lines), Fe dominates the extreme-UV (EUV) and FUV opacity and controls the mass-loss rate from massive stars, resulting in particularly dramatic effects for massive stars in binary systems. This high nebular excitation—caused by the hard EUV spectra of Fe-poor massive stars—is much more common at high redshift (z≳ 2) than low redshift due to systematic differences in the star formation history of typical galaxies. Based on data obtained at the W.M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and NASA, and was made possible by the generous financial support of the W.M. Keck Foundation.

Quasar probabilities and redshifts from WISE mid-IR through GALEX UV photometry

NASA Astrophysics Data System (ADS)

DiPompeo, M. A.; Bovy, J.; Myers, A. D.; Lang, D.

2015-09-01

Extreme deconvolution (XD) of broad-band photometric data can both separate stars from quasars and generate probability density functions for quasar redshifts, while incorporating flux uncertainties and missing data. Mid-infrared photometric colours are now widely used to identify hot dust intrinsic to quasars, and the release of all-sky WISE data has led to a dramatic increase in the number of IR-selected quasars. Using forced photometry on public WISE data at the locations of Sloan Digital Sky Survey (SDSS) point sources, we incorporate this all-sky data into the training of the XDQSOz models originally developed to select quasars from optical photometry. The combination of WISE and SDSS information is far more powerful than SDSS alone, particularly at z > 2. The use of SDSS+WISE photometry is comparable to the use of SDSS+ultraviolet+near-IR data. We release a new public catalogue of 5537 436 (total; 3874 639 weighted by probability) potential quasars with probability PQSO > 0.2. The catalogue includes redshift probabilities for all objects. We also release an updated version of the publicly available set of codes to calculate quasar and redshift probabilities for various combinations of data. Finally, we demonstrate that this method of selecting quasars using WISE data is both more complete and efficient than simple WISE colour-cuts, especially at high redshift. Our fits verify that above z ˜ 3 WISE colours become bluer than the standard cuts applied to select quasars. Currently, the analysis is limited to quasars with optical counterparts, and thus cannot be used to find highly obscured quasars that WISE colour-cuts identify in significant numbers.

Enhancing the far-ultraviolet sensitivity of silicon complementary metal oxide semiconductor imaging arrays

NASA Astrophysics Data System (ADS)

Retherford, Kurt D.; Bai, Yibin; Ryu, Kevin K.; Gregory, James A.; Welander, Paul B.; Davis, Michael W.; Greathouse, Thomas K.; Winters, Gregory S.; Suntharalingam, Vyshnavi; Beletic, James W.

2015-10-01

We report our progress toward optimizing backside-illuminated silicon P-type intrinsic N-type complementary metal oxide semiconductor devices developed by Teledyne Imaging Sensors (TIS) for far-ultraviolet (UV) planetary science applications. This project was motivated by initial measurements at Southwest Research Institute of the far-UV responsivity of backside-illuminated silicon PIN photodiode test structures, which revealed a promising QE in the 100 to 200 nm range. Our effort to advance the capabilities of thinned silicon wafers capitalizes on recent innovations in molecular beam epitaxy (MBE) doping processes. Key achievements to date include the following: (1) representative silicon test wafers were fabricated by TIS, and set up for MBE processing at MIT Lincoln Laboratory; (2) preliminary far-UV detector QE simulation runs were completed to aid MBE layer design; (3) detector fabrication was completed through the pre-MBE step; and (4) initial testing of the MBE doping process was performed on monitoring wafers, with detailed quality assessments.

Chandra and HST Observations of the High Energy (X-ray/UV) Radiation Fields for an Evolutionary Sequence of Pre-Main-Sequence Stars

NASA Astrophysics Data System (ADS)

Brown, Alexander; Herczeg, G. J.; Brown, J. M.; Walter, F. M.; Valenti, J.; Ardila, D.; Hillenbrand, L. A.; Edwards, S.; Johns-Krull, C. M.; Alexander, R.; Bergin, E. A.; Calvet, N.; Bethell, T. J.; Ingleby, L.; Bary, J. S.; Audard, M.; Baldovin, C.; Roueff, E.; Abgrall, H.; Gregory, S. G.; Ayres, T. R.; Linsky, J. L.

2010-03-01

Pre-main-sequence (PMS) stars are strong X-ray and UV emitters and the high energy radiation from the central stars directly influences the physical and chemical processes in their protoplanetary disks. Gas and dust in protoplanetary systems are excited by these photons, which are the dominant ionization source for hundreds of AU around the star. X-rays penetrate deep into disks and power complex chemistry on grain surfaces. ``Transitional disks'' are an important short-lived evolutionary stage for PMS stars and protoplanetary systems. These disks have transformed most of the dust and gas in their inner regions into planetesimals or larger solid bodies. As dust disks disappear after ages of roughly 5 Myr high levels of stellar magnetic activity persist and continue to bathe the newly-forming protoplanetary systems with intense high energy radiation. We present new X-ray and UV spectra for a sample of PMS stars at a variety of evolutionary stages, including the classical T Tauri stars DE Tau and DK Tau, the transitional disk stars GM Aur and HD135344B, the Herbig Ae star HD104237, and the weak-lined T Tauri star LkCa4, the Eta Cha cluster [age 7 Myr] members RECX1, RECX-11, and RECX-15, and TW Hya association [age 8 Myr] member TWA-2. These include the first results from our 111 orbit HST Large project and associated X-ray data. New and archival Chandra, XMM, and Swift X-ray spectra and HST COS+STIS FUV spectra are being used to reconstruct the full high energy (X-ray/EUV/FUV/NUV) spectra of these stars, thus allowing detailed modeling of the physics and chemistry of their circumstellar environments. The UV spectra provide improved emission line profiles revealing details of the magnetically-heated plasma and accretion and outflow processes. This work is supported by Chandra grants GO8-9024X, GO9-0015X and GO9-0020B and proposal 11200754 and HST GO grants 11336, 11616, and 11828.

UV observations of local interstellar medium.

NASA Astrophysics Data System (ADS)

Kurt, V.; Mironova, E.; Fadeev, E.

2008-12-01

The methods of the interstellar matter study are described. The brief information of space missions aimed at observations in the unreachable for ground based telescopes UV spectral range (IUE, As- tron, HST and GALEX.) is presented. The history of discovery of H and He atoms entering the Solar System from the local interstellar medium (LISM) is given in brief. The results of observations performed by the group from Stern- berg Astronomical Institute (SAI MSU) and Space Research Institute (IKI RAS) performed with the help of the missions Prognoz-5, Prognoz-6 and the stations Zond-1, Venera and Mars and aimed at estimation of all basic LISM parameters (the velocity of the Sun in relation to LISM, directions of movement, densities of H and He atoms, LISM temperature) are presented. We also describe the present-day investigations of LISM performed with SOHO and ULYSSES mis- sions including the direct registration of He atoms entering the Solar System. The problem of interaction between the incoming flow of the ISM atoms ("in- terstellar wind") and the area of two shocks at the heliopause border (100-200 AU) is discussed. The LISM parameters obtained using the available data are presented in two tables.

VizieR Online Data Catalog: Rapidly pulsating sdB stars search with GALEX (Boudreaux+, 2017)

NASA Astrophysics Data System (ADS)

Boudreaux, T. M.; Barlow, B. N.; Fleming, S. W.; Soto, A. V.; Million, C.; Reichart, D. E.; Haislip, J. B.; Linder, T. R.; Moore, J. P.

2018-04-01

Here we present a search for short-period hot subdwarf B (sdB) pulsations in the archived GALEX data set using gPhoton (Million+ 2016ApJ...833..292M). An initial sample of 5613 hot subdwarfs (Geier+ 2017, J/A+A/600/A50), which represents a good approximation of all cataloged hot subdwarf stars, was down-selected based on magnitudes, coordinates, and total exposure time available in the gPhoton database, described fully in Section 2. These selection criteria yielded 1881 targets upon which we focused our investigation. Calibrated light curves with time bins of 30s were generated for each target using gPhoton. (4 data files).

FUV Spectroscopy Of Outflows And Disks Around The Intermediate Mass Pre-main-sequence Stars HD135344B And HD104237

NASA Astrophysics Data System (ADS)

Brown, Alexander; Herczeg, G.; Brown, J. M.; Walter, F. M.; Ayres, T. R.; DAOof TAU Team

2011-01-01

The intermediate-mass, pre-main-sequence (Herbig Ae/Fe) stars HD135344B (F4) and HD104237 (A8 IV-V) are both still surrounded by almost face-on circumstellar disks. The disk around HD135344B is a ``transitional'' disk with a 25 AU radius cleared inner hole but still with some gas and dust very close to the star. We have obtained FUV spectra of these stars using the HST COS and STIS spectrographs that show that both stars have dramatic high-velocity (terminal velocity = 300-400 km/s) outflows and rich fluorescently-excited molecular hydrogen emission, originating primarily from warm gas in their disks. We present these FUV spectra and outline the outflow and disk properties implied by the observed emission and absorption line profiles. The profiles and widths of the molecular hydrogen lines provide strong constraints on the location of the emitting regions. This work is supported by HST grants for GO projects 11828 and 11616, and Chandra grant GO9-0015X to the University of Colorado.

The S201 far-ultraviolet imaging survey - A summary of results and implications for future surveys

NASA Technical Reports Server (NTRS)

Carruthers, G. R.; Page, T.

1984-01-01

The results from all-sky surveys with the S201 FUV camera/spectrograph from the moon during the Apollo 16 mission are summarized with respect to implications for future UV all-sky surveys. The scans provided imagery of 10 fields, each 20 deg in diameter, in the wavelength ranges 1050-1600 A and 1250-1600 A. Best detection thresholds were obtained with 10 and 30 min exposures at 1400 A. Only 7 percent sky coverage was recorded, and then only down to 11th mag. A Mark II camera may be flown on the Shuttle on the Spartan 3 mission, as may be an all-reflector Schmidt telescope. An additional 20 percent of the sky will be mapped and microchannel intensification will increase the diffuse source sensitivity by two orders of magnitude. Several objects sighted with the S201 will be reviewed with the Mark II.

Spatially Controlled Fabrication of Brightly Fluorescent Nanodiamond-Array with Enhanced Far-Red Si-V Luminescence

PubMed Central

Singh, Sonal; Thomas, Vinoy; Martyshkin, Dmitry; Kozlovskaya, Veronika; Kharlampieva, Eugenia

2014-01-01

We demonstrate a novel approach to precise pattern fluorescent nanodiamond-arrays with enhanced far-red intense photostable luminescence from silicon-vacancy (Si-V) defect centers. The precision-patterned pre-growth seeding of nanodiamonds is achieved by scanning probe “Dip-Pen” nanolithography technique using electrostatically-driven transfer of nanodiamonds from “inked” cantilevers to a UV-treated hydrophilic SiO2 substrate. The enhanced emission from nanodiamond-dots in the far-red is achieved by incorporating Si-V defect centers in subsequent chemical vapor deposition treatment. The development of a suitable nanodiamond ink, mechanism of ink transport, and effect of humidity, dwell time on nanodiamond patterning are investigated. The precision-patterning of as-printed (pre-CVD) arrays with dot diameter and dot height as small as 735 nm ± 27 nm, 61 nm ± 3 nm, respectively and CVD-treated fluorescent ND-arrays with consistently patterned dots having diameter and height as small as 820 nm ± 20 nm, 245 nm ± 23 nm, respectively using 1 s dwell time and 30% RH is successfully achieved. We anticipate that the far-red intense photostable luminescence (~738 nm) observed from Si-V defect centers integrated in spatially arranged nanodiamonds could be beneficial for the development of the next generation fluorescent based devices and applications. PMID:24394286

gPhoton: The GALEX Photon Data Archive

NASA Astrophysics Data System (ADS)

Million, Chase; Fleming, Scott W.; Shiao, Bernie; Seibert, Mark; Loyd, Parke; Tucker, Michael; Smith, Myron; Thompson, Randy; White, Richard L.

2016-12-01

gPhoton is a new database product and software package that enables analysis of GALEX ultraviolet data at the photon level. The project’s stand-alone, pure-Python calibration pipeline reproduces the functionality of the original mission pipeline to reduce raw spacecraft data to lists of time-tagged, sky-projected photons, which are then hosted in a publicly available database by the Mikulski Archive at Space Telescope. This database contains approximately 130 terabytes of data describing approximately 1.1 trillion sky-projected events with a timestamp resolution of five milliseconds. A handful of Python and command-line modules serve as a front end to interact with the database and to generate calibrated light curves and images from the photon-level data at user-defined temporal and spatial scales. The gPhoton software and source code are in active development and publicly available under a permissive license. We describe the motivation, design, and implementation of the calibration pipeline, database, and tools, with emphasis on divergence from prior work, as well as challenges created by the large data volume. We summarize the astrometric and photometric performance of gPhoton relative to the original mission pipeline. For a brief example of short time-domain science capabilities enabled by gPhoton, we show new flares from the known M-dwarf flare star CR Draconis. The gPhoton software has permanent object identifiers with the ASCL (ascl:1603.004) and DOI (doi:10.17909/T9CC7G). This paper describes the software as of version v1.27.2.

gPhoton: THE GALEX PHOTON DATA ARCHIVE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Million, Chase; Fleming, Scott W.; Shiao, Bernie

gPhoton is a new database product and software package that enables analysis of GALEX ultraviolet data at the photon level. The project’s stand-alone, pure-Python calibration pipeline reproduces the functionality of the original mission pipeline to reduce raw spacecraft data to lists of time-tagged, sky-projected photons, which are then hosted in a publicly available database by the Mikulski Archive at Space Telescope. This database contains approximately 130 terabytes of data describing approximately 1.1 trillion sky-projected events with a timestamp resolution of five milliseconds. A handful of Python and command-line modules serve as a front end to interact with the database andmore » to generate calibrated light curves and images from the photon-level data at user-defined temporal and spatial scales. The gPhoton software and source code are in active development and publicly available under a permissive license. We describe the motivation, design, and implementation of the calibration pipeline, database, and tools, with emphasis on divergence from prior work, as well as challenges created by the large data volume. We summarize the astrometric and photometric performance of gPhoton relative to the original mission pipeline. For a brief example of short time-domain science capabilities enabled by gPhoton, we show new flares from the known M-dwarf flare star CR Draconis. The gPhoton software has permanent object identifiers with the ASCL (ascl:1603.004) and DOI (doi:10.17909/T9CC7G). This paper describes the software as of version v1.27.2.« less

Changes in the Near-UV Spectrum of eta Car 2002 - 2015

NASA Astrophysics Data System (ADS)

Martin, John; Davidson, Kris; Ishabashi, Kazunori; Humphreys, Roberta; Mehner, Andrea

2018-01-01

Eta Car's detailed UV spectrum has been somewhat neglected in recent years, because of its complexity. Here we report on NUV and FUV data obtained with the HST STIS/MAMA spanning a time interval of more than a decade. The main results fall into three categories: (1) Changes in a diverse set of absorption lines (Fe II, Si II, Si IV, Al III, etc.) indicate changes in the wind's ionization structure between 2002 and 2013. The trend is toward more highly ionized species. (2) The extremely luminous N III] 1750 A multiplet has also changed in the same sense. (3) Curiously, the N III] profile in 2015 closely resembled its 2013 state. This is a surprise because those two dates had very different orbital phases; in most models the Doppler velocity profiles should have differed because the shock structure's viewing angle changed. We discuss these results' implications for the primary stellar wind and for the secondary star's orbit.

Cosmic Evolution Through UV Spectroscopy (CETUS): A NASA Probe-Class Mission Concept

NASA Astrophysics Data System (ADS)

Heap, Sara R.; CETUS Team

2017-01-01

CETUS is a probe-class mission concept proposed for study to NASA in November 2016. Its overarching objective is to provide access to the ultraviolet (~100-400 nm) after Hubble has died. CETUS will be a major player in the emerging global network of powerful, new telescopes such as E-ROSITA, DESI, Subaru/PFS, GMT, LSST, WFIRST, JWST, and SKA. The CETUS mission concept provisionally features a 1.5-m telescope with a suite of instruments including a near-UV multi-object spectrograph (200-400 nm) complementing Subaru/PFS observations, wide-field far-UV and near-UV cameras, and far-UV and near-UV spectrographs that can be operated in either high-resolution or low-resolution mode. We have derived the scope and specific science requirements for CETUS for understanding the evolutionary history of galaxies, stars, and dust, but other applications are possible.

KSWAGS: A Swift X-Ray and UV Survey of the Kepler Field 1

NASA Technical Reports Server (NTRS)

Smith, Krista Lynne; Boyd, Patricia T.; Mushotzky, Richard F.; Gehrels, Neil; Edelson, Rick; Howell, Steve B.; Gelino, Dawn M.; Brown, Alexander; Young, Steve

2015-01-01

We introduce the first phase of the Kepler-Swift Active Galaxies and Stars survey (KSwAGS), a simultaneous X-ray and UV survey of approximately 6 square degrees of the Kepler field using the Swift XRT and UVOT. We detect 93 unique X-ray sources with S/N greater or equal to 3 with the XRT, of which 60 have UV counterparts. We use the Kepler Input Catalog (KIC) to obtain the optical counterparts of these sources, and construct the fX / fV ratio as a first approximation of the classification of the source. The survey produces a mixture of stellar sources, extragalactic sources, and sources which we are not able to classify with certainty. We have obtained optical spectra for thirty of these targets, and are conducting an ongoing observing campaign to fully identify the sample. For sources classified as stellar or AGN with certainty, we construct SEDs using the 2MASS, UBV and GALEX data supplied for their optical counterparts by the KIC, and show that the SEDs differ qualitatively between the source types, and so can offer a method of classification in absence of a spectrum. Future papers in this series will analyze the timing properties of the stars and AGN in our sample separately. Our survey provides the first X-ray and UV data for a number of known variable stellar sources, as well as a large number of new X-ray detections in this well-studied portion of the sky. The KSwAGS survey is currently ongoing in the K2 ecliptic plane fields.

The UV-brightest Stars of M33 and Its Nucleus: Discovery, Photometry, and Optical Spectroscopy

NASA Astrophysics Data System (ADS)

Massey, Philip; Bianchi, Luciana; Hutchings, John B.; Stecher, Theodore P.

1996-10-01

We investigate the UV-brightest sources in the nearby galaxy M33. Our catalog of 356 sources is constructed from far-ultraviolet (FUV; 1500 A) and near-ultraviolet (NUV; 2400 A) images obtained with the Ultraviolet Imaging Telescope (UIT) matched with ground-based UBV data. We find that our survey is limited by the FUV flux and is complete to Flambda1500_ = 2.5 x 10^-15^ ergs cm^-2^ s^-1^ A^-1^, other than in the most crowded regions; this corresponds roughly to M_bol_ = -9.2 to -10.0 (or masses of 40-60 M_sun_), for T_eff_ = 50,000^deg^ to 10,000^deg^. We use Hubble Space Telescope (HST) WFPC2 images of several M33 fields to conclude that at least one-half of our sample is uncontaminated by unresolved neighbors, at least at the 0.1" (0.4 pc) level, a resolution similar to that achieved in the LMC from the ground. Spectral types have been obtained for 131 of our objects. We discuss the spatial distribution of the UIT sources, finding that they provide an excellent tracer of the spiral arm pattern and confirm that star formation continues in the nuclear region to the present day. Our survey has found a large number of O and early B-type supergiants, including stars as early as O6, but the optical spectroscopic sample is dominated by later type B supergiants, as these are the visually brighter. Among the brightest stars (both at 1500A and at V) are the "superluminous" Wolf-Rayet stars first discovered by Conti & Massey in the largest H II regions of M33; these objects are now known to be small groups of stars in modest analog to R136 in 30 Dor. In general, our survey has failed to detect the known W-R stars, as they are too faint, but we did find several new late-type WN stars and composite systems, which are brighter. Two stars of high absolute visual magnitude (M_V_ ~-9.0) are found to be B I + WN binaries, similar to HDE 269546 in the LMC; one of these is multiple at HST resolution. Most interesting, perhaps, is our finding six Ofpe/WN9 "slash" stars, five of them

Investigation of coronal holes in the radio and far-ultraviolet ranges

NASA Technical Reports Server (NTRS)

Sheridan, K. V.; Smerd, S. F.

1977-01-01

Results of coronal-hole observations carried out in the far-UV with a spectro-heliometer aboard Skylab are compared with corresponding results of ground-based radioheliograph measurements performed at frequencies of 80 and 160 MHz. It is found that the electron density derived from the far-UV observations for the transition region and lower corona is nearly three times greater than the value computed on the basis of the radio data. Unsuccessful attempts are made to eliminate this discrepancy by recalibrating the radio data and by recalculating the ionization equilibrium. A substantial local enhancement of the heavy-element abundance in certain parts of the transition region and inner chromosphere is considered as a possible cause of the discrepancy.

Ionospheric dynamo theory for production of far ultraviolet emissions on Uranus

NASA Technical Reports Server (NTRS)

Hudson, M. K.; Warren, J. A.; Clarke, J. T.

1989-01-01

A model is presented to explain diffuse FUV emissions from the outer planets, specifically Uranus, in excess of those diffuse emissions that are currently explainable by scattering of sunlight and/or excitation by photoelectrons. These electroglow emissions in H Ly-alpha and H2 bands, which occur in the sunlit hemisphere slightly above the homopause, appear to require particle excitation in the 10- to 50-eV range. An in situ mechanism for accelerating photoelectrons (and ions is proposed, involving neutral wind dynamo generation of field-aligned currents analogous to what occurs in the earth's equatorial E and F regions. Sufficiently strong field-aligned currents are found in the model calculation for Uranus to produce a potential drop of about 100 eV or greater between the F peak and homopause, concentrated at lower altitudes, and capable in principle of accelerating photoelectrons (and ions) to the 10- to 50-eV energies required to explain the observed emissions. The fact that the excitation and ionization cross sections are larger than elastic scattering cross sections in an H2 atmosphere at these energies makes in situ acceleration feasible for the production of UV on the outer planets.

Solar-Iss a New Solar Reference Spectrum Covering the Far UV to the Infrared (165 to 3088 Nm) Based on Reanalyzed Solar/solspec Cycle 24 Observations

NASA Astrophysics Data System (ADS)

Damé, L.; Meftah, M.; Irbah, A.; Hauchecorne, A.; Bekki, S.; Bolsée, D.; Pereira, N.; Sluse, D.; Cessateur, G.

2017-12-01

Since April 5, 2008 and until February 15, 2017, the SOLSPEC (SOLar SPECtrometer) spectro-radiometer of the SOLAR facility on the International Space Station performed accurate measurements of Solar Spectral Irradiance (SSI) from the far ultraviolet to the infrared (165 nm to 3088 nm). These measurements, unique by their large spectral coverage and long time range, are of primary importance for a better understanding of solar physics and of the impact of solar variability on climate (via Earth's atmospheric photochemistry), noticeably through the "top-down" mechanism amplifying ultraviolet (UV) solar forcing effects on the climate (UV affects stratospheric dynamics and temperatures, altering interplanetary waves and weather patterns both poleward and downward to the lower stratosphere and troposphere regions). SOLAR/SOLSPEC, with almost 9 years of observations covering the essential of the unusual solar cycle 24 from minimum in 2008 to maximum, allowed to establish new reference solar spectra from UV to IR (165 to 3088 nm) at minimum (beginning of mission) and maximum of activity. The complete reanalysis was possible thanks to revised engineering corrections, improved calibrations and advanced procedures to account for thermal, aging and pointing corrections. The high quality and sensitivity of SOLSPEC data allow to follow temporal variability in UV but also in visible along the cycle. Uncertainties on these measurements are evaluated and results, absolute reference spectra and variability, are compared with other measurements (WHI, ATLAS-3, SCIAMACHY, SORCE/SOLSTICE, SORCE/SIM) and models (SATIRE-S, NRLSSI, NESSY)

Calibration Efforts and Unique Capabilities of the HST Space Telescope Imaging Spectrograph

NASA Astrophysics Data System (ADS)

Monroe, TalaWanda R.; Proffitt, Charles R.; Welty, Daniel; Branton, Doug; Carlberg, Joleen K.; debes, John Henry; Lockwood, Sean; Riley, Allyssa; Sohn, Sangmo Tony; Sonnentrucker, Paule G.; Walborn, Nolan R.; Jedrzejewski, Robert I.

2018-01-01

The Space Telescope Imaging Spectrograph (STIS) continues to offer the astronomy community the ability to carry out innovative UV and optical spectroscopic and imaging studies, two decades after its deployment on the Hubble Space Telescope (HST). Most notably, STIS provides spectroscopy in the FUV and NUV, including high spectral resolution echelle modes, imaging in the FUV, optical spectroscopy, and coronagraphic capabilities. Additionally, spatial scanning on the CCD with the long-slits is now possible to enable very high S/N spectroscopic observations without saturation while mitigating telluric and fringing concerns in the far red and near-IR. This new mode may especially benefit the diffuse interstellar bands and exoplanet transiting communities. We present recent calibration efforts for the instrument, including work to optimize the calibration of the echelle spectroscopic modes by improving the flux agreement of overlapping spectral orders affected by changes in the grating blaze function since HST Servicing Mission 4. We also discuss considerations to maintain the wavelength precision of the spectroscopic modes, and the current capabilities of CCD spectroscopic spatial trails.

Simultaneous DMSP, All-Sky Camera, and IMAGE FUV Observations of the Brightening Arc at a Substorm Pseudo-Breakup

DTIC Science & Technology

2007-03-01

arc at a substorm pseudo-breakup Sb. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 61102F 6. AUTHORS 5d. PROJECT NUMBER K. Yago ,, K. Shiokawa, K. Yumoto...Distribution Unlimited Simultaneous DMSP, all-sky camera, and IMAGE FUV observations of the brightening arc at a substorm pseudo-breakup K. Yago "•. K. Shiokawa...2003; Mende et al., particles, field-aligned currents, and plasma convection as- 2003: Yago et al., 2005: Shiokawa et al., 2005). These sociated with

Far Ultraviolet Spectroscopic Explorer Observations of the Seyfert 1.5 Galaxy NGC 5548 in a Low State

NASA Technical Reports Server (NTRS)

Brotherton, M. S.; Green, R. F.; Kriss, G. A.; Oegerle, W.; Kaiser, M. E.; Zheng, W.; Hutchings, J. B.; Fisher, Richard R. (Technical Monitor)

2001-01-01

We present far-ultraviolet spectra of the Seyfert 1.5 galaxy NGC 5548 obtained in 2000 June with the Far Ultraviolet Spectroscopic Explorer (FUSE). Our data span the observed wavelength range 915-1185 A at a resolution of approximately 20 km s(exp -1). The spectrum shows a weak continuum and emission from O VI (lambda)(lambda)1032, 1038, C III (lambda)977, and He II (lambda)1085. The FUSE data were obtained when the AGN (Active Galactic Nuclei) was in a low state, which has revealed strong, narrow O VI emission lines. We also resolve intrinsic, associated absorption lines of O VI and the Lyman series. Several distinct kinematic components are present, spanning a velocity range of approximately 0 to -1300 km s(exp -1) relative to systemic, with kinematic structure similar to that seen in previous observations of longer wavelength ultraviolet (UV) lines. We explore the relationships between the far-UV (ultraviolet) absorbers and those seen previously in the UV and X-rays. We find that the high-velocity UV absorption component is consistent with being low-ionization, contrary to some previous claims, and is consistent with its non-detection in high-resolution X-ray spectra. The intermediate velocity absorbers, at -300 to -400 km s(exp -1), show H I and O VI column densities consistent with having contributions from both a high-ionization X-ray absorber and a low-ionization UV absorber. No single far-UV absorbing component can be solely identified with the X-ray absorber.

X-Ray, UV and Optical Observations of Classical Cepheids: New Insights into Cepheid Evolution, and the Heating and Dynamics of Their Atmospheres

NASA Astrophysics Data System (ADS)

Engle, Scott G.; Guinan, Edward F.

2012-06-01

To broaden the understanding of classical Cepheid structure, evolution and atmospheres, we have extended our continuing secret lives of Cepheids program by obtaining XMM/Chandra X-ray observations, and Hubble space telescope (HST) / cosmic origins spectrograph (COS) FUV-UV spectra of the bright, nearby Cepheids Polaris, δ Cep and β Dor. Previous studies made with the international ultraviolet explorer (IUE) showed a limited number of UV emission lines in Cepheids. The well-known problem presented by scattered light contamination in IUE spectra for bright stars, along with the excellent sensitivity & resolution combination offered by HST/COS, motivated this study, and the spectra obtained were much more rich and complex than we had ever anticipated. Numerous emission lines, indicating 10^4 K up to ~3 x 10^5 K plasmas, have been observed, showing Cepheids to have complex, dynamic outer atmospheres that also vary with the photospheric pulsation period. The FUV line emissions peak in the phase range φ ∼ 0.8-1.0 and vary by factors as large as 10x. A more complete picture of Cepheid outer atmospheres is accomplished when the HST/COS results are combined with X-ray observations that we have obtained of the same stars with XMM-Newton & Chandra. The Cepheids detected to date have X-ray luminosities of log Lx ~ 28.5-29.1 ergs/sec, and plasma temperatures in the 2-8 x 10^6 K range. Given the phase-timing of the enhanced emissions, the most plausible explanation is the formation of a pulsation-induced shocks that excite (and heat) the atmospheric plasmas surrounding the photosphere. A pulsation-driven α^2 equivalent dynamo mechanism is also a viable and interesting alternative. However, the tight phase-space of enhanced emission (peaking near 0.8-1.0 φ) favor the shock heating mechanism hypothesis.

Performance of the Far Ultraviolet Spectroscopic Explorer mirror assemblies

NASA Astrophysics Data System (ADS)

Ohl, Raymond G.; Barkhouser, Robert H.; Conard, Steven J.; Friedman, Scott D.; Hampton, Jeffrey; Moos, H. Warren; Nikulla, Paul; Oliveira, Cristina M.; Saha, Timo T.

2000-12-01

The Far Ultraviolet Spectroscopic Explorer is a NASA astrophysics satellite which produces high-resolution spectra in the far-ultraviolet (90.5 - 118.7 nm bandpass) using a high effective area and low background detectors. The observatory was launched on its three-year mission from Cape Canaveral Air Station on 24 June 1999. The instrument contains four co- aligned, normal incidence, off-axis parabolic mirrors which illuminate separate Rowland circle spectrograph channels equipped with holographically ruled diffraction gratings and delay line microchannel plate detectors. The telescope mirrors have a 352 X 387 mm aperture and 2245 mm focal length and are attached to actuator assemblies, which provide on-orbit, tip, tilt, and focus control. Two mirrors are coated with silicon carbide (SiC) and two are coated with lithium fluoride over aluminum (Al:LiF). We describe mirror assembly in-flight optical and mechanical performance. On-orbit measurements of the far-ultraviolet point spread function associated with each mirror are compared to expectations based on pre-flight laboratory measurements and modeling using the Optical Surface Analysis Code and surface metrology data. On-orbit imaging data indicate that the mirrors meet their instrument-level requirement of 50% and 95% slit transmission for the high- and mid-resolution spectrograph entrance slits, respectively. The degradation of mirror reflectivity during satellite integration and test is also discussed. The FUV reflectivity of the SiC- and Al:LiF-coated mirrors decreased about 6% and 3%, respectively, between coating and launch. Each mirror is equipped with three actuators, which consist of a stepper motor driving a ball screw via a two-stage planetary gear train. We also discuss the mechanical performance of the mirror assemblies, including actuator performance and thermal effects.

The Ultraviolet Radiation Environment around M Dwarf Exoplanet Host Stars

NASA Technical Reports Server (NTRS)

France, Kevin; Froning, Cynthia S.; Linsky, Jeffrey L.; Roberge, Aki; Stocke, John T.; Tian, Feng; Bushinsky, Rachel; Desert, Jean-Michel; Mauas, Pablo; Mauas, Pablo;

THE BINARY BLACK HOLE MODEL FOR MRK 231 BITES THE DUST

DOE Office of Scientific and Technical Information (OSTI.GOV)

Leighly, Karen M.; Terndrup, Donald M.; Gallagher, Sarah C.

2016-09-20

Mrk 231 is a nearby quasar with an unusually red near-UV-to-optical continuum, generally explained as heavy reddening by dust. Yan et al. proposed that Mrk 231 is a milliparsec black hole binary with little intrinsic reddening. We show that if the observed FUV continuum is intrinsic, as assumed by Yan et al., it fails by a factor of about 100 in powering the observed strength of the near-infrared emission lines and the thermal near and mid-infrared continuum. In contrast, the line and continuum strengths are typical for a reddened AGN spectral energy distribution (SED). We find that the He i*/Pmore » β ratio is sensitive to the SED for a one-zone model. If this sensitivity is maintained in general broadline region models, then this ratio may prove a useful diagnostic for heavily reddened quasars. Analysis of archival Hubble Space Telescope STIS and Faint Object Camera data revealed evidence that the far-UV continuum emission is resolved on size scales of ∼40 pc. The lack of broad absorption lines in the far-UV continuum might be explained if it were not coincident with the central engine. One possibility is that it is the central engine continuum reflected from the receding wind on the far side of the quasar.« less

The Massive Stellar Population in the Diffuse Ionized Gas of M33

NASA Technical Reports Server (NTRS)

Hoopes, Charles G.; Walterbos, Rene A. M.

1995-01-01

We compare Far-UV, H alpha, and optical broadband images of the nearby spiral galaxy M33, to investigate the massive stars associated with the diffuse ionized gas. The H-alpha/FUV ratio is higher in HII regions than in the DIG, possibly indicating that an older population ionizes the DIG. The broad-band colors support this conclusion. The HII region population is consistent with a young burst, while the DIG colors resemble an older population with constant star formation. Our results indicate that there may be enough massive field stars to ionize the DIG, without the need for photon leakage from HII regions.

Daytime O/N2 Retrieval Algorithm for the Ionospheric Connection Explorer (ICON)

NASA Astrophysics Data System (ADS)

Stephan, Andrew W.; Meier, R. R.; England, Scott L.; Mende, Stephen B.; Frey, Harald U.; Immel, Thomas J.

2018-02-01

The NASA Ionospheric Connection Explorer Far-Ultraviolet spectrometer, ICON FUV, will measure altitude profiles of the daytime far-ultraviolet (FUV) OI 135.6 nm and N2 Lyman-Birge-Hopfield (LBH) band emissions that are used to determine thermospheric density profiles and state parameters related to thermospheric composition; specifically the thermospheric column O/N2 ratio (symbolized as ΣO/N2). This paper describes the algorithm concept that has been adapted and updated from one previously applied with success to limb data from the Global Ultraviolet Imager (GUVI) on the NASA Thermosphere Ionosphere Mesosphere Energetics and Dynamics (TIMED) mission. We also describe the requirements that are imposed on the ICON FUV to measure ΣO/N2 over any 500-km sample in daytime with a precision of better than 8.7%. We present results from orbit-simulation testing that demonstrates that the ICON FUV and our thermospheric composition retrieval algorithm can meet these requirements and provide the measurements necessary to address ICON science objectives.

Spatially controlled fabrication of a bright fluorescent nanodiamond-array with enhanced far-red Si-V luminescence.

PubMed

Singh, Sonal; Thomas, Vinoy; Martyshkin, Dmitry; Kozlovskaya, Veronika; Kharlampieva, Eugenia; Catledge, Shane A

2014-01-31

We demonstrate a novel approach to precisely pattern fluorescent nanodiamond-arrays with enhanced far-red intense photostable luminescence from silicon-vacancy (Si-V) defect centers. The precision-patterned pre-growth seeding of nanodiamonds is achieved by a scanning probe 'dip-pen' nanolithography technique using electrostatically driven transfer of nanodiamonds from 'inked' cantilevers to a UV-treated hydrophilic SiO2 substrate. The enhanced emission from nanodiamond dots in the far-red is achieved by incorporating Si-V defect centers in a subsequent chemical vapor deposition treatment. The development of a suitable nanodiamond ink and mechanism of ink transport, and the effect of humidity and dwell time on nanodiamond patterning are investigated. The precision patterning of as-printed (pre-CVD) arrays with dot diameter and dot height as small as 735 nm ± 27 nm and 61 nm ± 3 nm, respectively, and CVD-treated fluorescent ND-arrays with consistently patterned dots having diameter and height as small as 820 nm ± 20 nm and, 245 nm ± 23 nm, respectively, using 1 s dwell time and 30% RH is successfully achieved. We anticipate that the far-red intense photostable luminescence (~738 nm) observed from Si-V defect centers integrated in spatially arranged nanodiamonds could be beneficial for the development of next generation fluorescence-based devices and applications.

Far Ultraviolet Astronomy

NASA Technical Reports Server (NTRS)

Sonneborn, George; Rabin, Douglas M. (Technical Monitor)

2002-01-01

The Far Ultraviolet Spectroscopic Explorer (FUSE) is studying a wide range of astronomical problems in the 905-1187 Angstrom wavelength region through the use of high resolution spectroscopy. The FUSE bandpass forms a nearly optimal complement to the spectral coverage provided by the Hubble Space Telescope (HST), which extends down to approximately 1170 Angstroms. The photoionization threshold of atomic hydrogen (911 Angstroms) sets a natural short-wavelength limit for the FUV. FUSE was launched in June 1999 from Cape Canaveral, Florida, on a Delta II rocket into a 768 km circular orbit. Scientific observations started later that year. This spectral region is extremely rich in spectral diagnostics of astrophysical gases over a wide range of temperatures (100 K to over 10 million K). Important strong spectral lines in this wavelength range include those of neutral hydrogen, deuterium, nitrogen, oxygen, and argon (H I, D I, N I, O I, and Ar I), molecular hydrogen (H2), five-times ionized oxygen (O VI), and several ionization states of sulfur (S III - S VI). These elements are essential for understanding the origin and evolution of the chemical elements, the formation of stars and our Solar System, and the structure of galaxies, including our Milky Way. FUSE is one of NASA's Explorer missions and a cooperative project of NASA and the space agencies of Canada and France. These missions are smaller, more scientifically focused missions than the larger observatories, like Hubble and Chandra. FUSE was designed, built and operated for NASA by the Department of Physics and Astronomy at Johns Hopkins University. Hundreds of astronomers world-wide are using FUSE for a wide range of scientific research. Some of the important scientific discoveries from the first two years of the mission are described.

Multiple Scattering Principal Component-based Radiative Transfer Model (PCRTM) from Far IR to UV-Vis

NASA Astrophysics Data System (ADS)

Liu, X.; Wu, W.; Yang, Q.

2017-12-01

Modern satellite hyperspectral satellite remote sensors such as AIRS, CrIS, IASI, CLARREO all require accurate and fast radiative transfer models that can deal with multiple scattering of clouds and aerosols to explore the information contents. However, performing full radiative transfer calculations using multiple stream methods such as discrete ordinate (DISORT), doubling and adding (AD), successive order of scattering order of scattering (SOS) are very time consuming. We have developed a principal component-based radiative transfer model (PCRTM) to reduce the computational burden by orders of magnitudes while maintain high accuracy. By exploring spectral correlations, the PCRTM reduce the number of radiative transfer calculations in frequency domain. It further uses a hybrid stream method to decrease the number of calls to the computational expensive multiple scattering calculations with high stream numbers. Other fast parameterizations have been used in the infrared spectral region reduce the computational time to milliseconds for an AIRS forward simulation (2378 spectral channels). The PCRTM has been development to cover spectral range from far IR to UV-Vis. The PCRTM model have been be used for satellite data inversions, proxy data generation, inter-satellite calibrations, spectral fingerprinting, and climate OSSE. We will show examples of applying the PCRTM to single field of view cloudy retrievals of atmospheric temperature, moisture, traces gases, clouds, and surface parameters. We will also show how the PCRTM are used for the NASA CLARREO project.

The Stellar-IRIS Connection: Four Years of FUV Measurements of Alpha Centauri by HST/STIS

NASA Astrophysics Data System (ADS)

Ayres, Thomas R.

2014-06-01

Since 2010 January, shortly after the miraculous repair of Hubble's Space Telescope Imaging Spectrograph (STIS) by SM4, the two sun-like stars of Alpha Centauri ("A" [G2V] and "B" [K1V]) have been recorded on a semi-annual basis utilizing STIS's far-ultraviolet (115-170 nm) medium resolution mode (about 8 km/s FWHM resolving power), jointly with an X-ray imaging study of AB by the Chandra Observatory. Both efforts are intended to assess the long-term behavior of high-energy (multimillion K) coronal, and subcoronal, processes on the two relatively low-activity solar-age dwarfs. In fact, the near-solar-twin Alpha Cen A has been mired in a coronal lull since 2005, originally recognized by XMM-Newton, and only recently has begun to climb out of the extended X-ray minimum. Meanwhile, the lower mass, lower luminosity, but coronally more active secondary has displayed a clear 8-year X-ray cycle, extending from the mid-1990's ROSAT era. The current study focuses on properties of the "transition zone" lines ( 100,000 K) of the Alpha Centauri stars, namely the bulk redshifts exhibited by the Si IV, C IV, and N V doublets; the multi-component nature of the hot-line profiles; behavior of the Fe XII 124 nm coronal forbidden line; and variability of the FUV fluxes relative to the higher-energy X-ray time series. These stellar measurements, with their high precision in wavelength and flux, complement the detailed high-spatial and high-temporal resolution spectral mapping of the solar corona and lower atmosphere being carried out by NASA's Interface Region Imaging Spectrograph (IRIS). [This work supported by GO grants 12758, 13060, and 13465 from Space Telescope Science Institute.

Multilayer thin film design as far ultraviolet quarterwave retarders

NASA Technical Reports Server (NTRS)

Kim, Jongmin; Zukic, Muamer; Torr, Douglas T.; Wilson, Michele M.

1993-01-01

At short wavelengths, such as FUV, transparent, optically active materials are scarce. Reflection phase retardation by a multilayer thin film can be a good alternative in this wavelength region. We design a multilayer quarterwave retarder by calculating the electric fields at each boundary in the multilayer thin film. Using this method, we achieve designs of FUV multilayers which provide high, matched reflectances for both s- and p-polarization states, and at the same time a phase difference between these two states of nearly 90 deg. For example, a quarterwave retarder designed at the Lyman-alpha line (121.6 nm) has 81.05 percent reflectance for the s-polarization and 81.04 percent for the p-polarization state. The phase difference between these two polarization states is 90.07 deg. For convenience the retarders are designed for 45 deg angle of incidence, but our design approach can be used for any other angle of incidence. Aluminum and MgF2 are used as film materials and an opaque thick film of aluminum as the substrate.

Far-UV HST  Spectroscopy of an Unusual Hydrogen-poor Superluminous Supernova: SN2017egm

NASA Astrophysics Data System (ADS)

Yan, Lin; Perley, D. A.; De Cia, A.; Quimby, R.; Lunnan, R.; Rubin, Kate H. R.; Brown, P. J.

2018-05-01

SN2017egm is the closest (z = 0.03) H-poor superluminous supernova (SLSN-I) detected to date, and a rare example of an SLSN-I in a massive, metal-rich galaxy. We present the HST UV and optical spectra covering 1000–5500 Å, taken at +3 day relative to the peak. Our data reveal two absorption systems at redshifts matching the host galaxy NGC 3191 (z = 0.0307) and its companion galaxy (z = 0.0299) 73″ apart. Weakly damped Lyα absorption lines are detected at these two redshifts, with H I column densities of (3.0 ± 0.8) × 1019 and (3.7 ± 0.9) × 1019 cm‑2, respectively. This is an order of magnitude smaller than the H I column densities in the disks of nearby galaxies (>1010 M ⊙) and suggests that SN2017egm is on the near side of NGC 3191 and has a low host extinction (E(B ‑ V) ∼ 0.007). Using unsaturated metal absorption lines, we find that the host of SN2017egm probably has a solar or higher metallicity and is unlikely to be a dwarf companion to NGC 3191. Comparison of early-time UV spectra of SN2017egm, Gaia16apd, iPTF13ajg, and PTF12dam finds that the continuum at λ > 2800 Å is well fit by a blackbody, whereas the continuum at λ < 2800 Å is considerably below the model. The degree of UV suppression varies from source to source, with the 1400–2800 Å continuum flux ratio of 1.5 for Gaia16apd and 0.4 for iPTF13ajg. This cannot be explained by the differences in magnetar power or blackbody temperature. Finally, the UV spectra reveal a common set of seven broad absorption features and their equivalent widths are similar (within a factor of 2) among the four events.

Solar UV dose patterns in Italy.

PubMed

Meloni, D; Casale, G R; Siani, A M; Palmieri, S; Cappellani, F

2000-06-01

Since 1992 solar ultraviolet (UV) spectral irradiance (290-325 nm) has been measured at two Italian stations of Rome (urban site) and Ispra (semirural site) using Brewer spectrophotometry. The data collected under all sky conditions, are compared with the output of a sophisticated radiative transfer model (System for Transfer of Atmospheric Radiation--STAR model). The STAR multiple scattering scheme is able to cope with all physical processes relevant to the UV transfer through the atmosphere. The experience so far acquired indicates that, in spite of the unavoidable uncertainties in the input parameters (ozone, aerosol, surface albedo, pressure, temperature, relative humidity, cloud cover), measured and computed clear sky iradiances are in reasonable agreement. The STAR model is applied to build up the solar UV geographic patterns in Italy: the daily dose in the range 290-325 nm is computed at about 70 sites where a thorough and homogeneous climatology is available. For each month the concept of an idealized "standard day" is introduced and the surface distribution of solar UV field determined. The map of solar UV patterns for Italy, available for the first time, meets the study requirements in the field of skin and eye epidemiology, as well as in other investigations dealing with the impact of UV on the biosphere. The results are interpreted in terms of atmospheric and meteorological parameters modulating UV radiation reaching the ground.

Arabidopsis FHY3 and HY5 Positively Mediate Induction of COP1 Transcription in Response to Photomorphogenic UV-B Light[C][W][OA

PubMed Central

Huang, Xi; Ouyang, Xinhao; Yang, Panyu; Lau, On Sun; Li, Gang; Li, Jigang; Chen, Haodong; Deng, Xing Wang

2012-01-01

As sessile organisms, higher plants have evolved the capacity to sense and interpret diverse light signals to modulate their development. In Arabidopsis thaliana, low-intensity and long-wavelength UV-B light is perceived as an informational signal to mediate UV-B–induced photomorphogenesis. Here, we report that the multifunctional E3 ubiquitin ligase, CONSTITUTIVE PHOTOMORPHOGENESIS1 (COP1), a known key player in UV-B photomorphogenic responses, is also a UV-B–inducible gene. Two transcription factors, FAR-RED ELONGATED HYPOCOTYL3 (FHY3) and ELONGATED HYPOCOTYL5 (HY5), directly bind to distinct regulatory elements within the COP1 promoter, which are essential for the induction of the COP1 gene mediated by photomorphogenic UV-B signaling. Absence of FHY3 results in impaired UV-B–induced hypocotyl growth and reduced tolerance against damaging UV-B. Thus, FHY3 positively regulates UV-B–induced photomorphogenesis by directly activating COP1 transcription, while HY5 promotes COP1 expression via a positive feedback loop. Furthermore, FHY3 and HY5 physically interact with each other, and this interaction is diminished by UV-B. Together, our findings reveal that COP1 gene expression in response to photomorphogenic UV-B is controlled by a combinatorial regulation of FHY3 and HY5, and this UV-B–specific working mode of FHY3 and HY5 is distinct from that in far-red light and circadian conditions. PMID:23150635

Mid-UV studies of the transitional millisecond pulsars XSS J12270-4859 and PSR J1023+0038 during their radio pulsar states

NASA Astrophysics Data System (ADS)

Rivera Sandoval, L. E.; Hernández Santisteban, J. V.; Degenaar, N.; Wijnands, R.; Knigge, C.; Miller, J. M.; Reynolds, M.; Altamirano, D.; van den Berg, M.; Hill, A.

2018-05-01

We report mid-UV (MUV) observations taken with Hubble Space Telescope (HST)/WFC3, Swift/UVOT, and GALEX/NUV of the transitional millisecond pulsars XSS J12270-4859 and PSR J1023+0038 during their radio pulsar states. Both systems were detected in our images and showed MUV variability. At similar orbital phases, the MUV luminosities of both pulsars are comparable. This suggests that the emission processes involved in both objects are similar. We estimated limits on the mass ratio, companion's temperature, inclination, and distance to XSS J12270-4859 by using a Markov Chain Monte Carlo algorithm to fit published folded optical light curves. Using the resulting parameters, we modelled MUV light curves in our HST filters. The resulting models failed to fit our MUV observations. Fixing the mass ratio of XSS J12270-4859 to the value reported in other studies, we obtained a distance of ˜3.2 kpc. This is larger than the one derived from dispersion measure (˜1.4 kpc). Assuming a uniform prior for the mass ratio, the distance is similar to that from radio measurements. However, it requires an undermassive companion (˜0.01M⊙). We conclude that a direct heating model alone cannot fully explain the observations in optical and MUV. Therefore, an additional radiation source is needed. The source could be an intrabinary shock which contributes to the MUV flux and likely to the optical one as well. During the radio pulsar state, the MUV orbital variations of PSR J1023+0038 detected with GALEX, suggest the presence of an asymmetric intrabinary shock.

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

NASA Astrophysics Data System (ADS)

Reddy, Naveen A.; Steidel, Charles C.; Pettini, Max; Bogosavljević, Milan

2016-09-01

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 (≳ 7 hr) at λ =850{--}1300 \\mathring{{A}} , 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 H I, 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({{H}} {{I}})≲ {10}17.2 cm-2) neutral ISM of high-redshift galaxies. Based on data obtained at the W.M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and NASA, and was made possible by the generous financial support of the W.M. Keck Foundation.

The interstellar medium and star formation of galactic disks. I. Interstellar medium and giant molecular cloud properties with diffuse far-ultraviolet and cosmic-ray backgrounds

NASA Astrophysics Data System (ADS)

Li, Qi; Tan, Jonathan C.; Christie, Duncan; Bisbas, Thomas G.; Wu, Benjamin

2018-05-01

We present a series of adaptive mesh refinement hydrodynamic simulations of flat rotation curve galactic gas disks, with a detailed treatment of the interstellar medium (ISM) physics of the atomic to molecular phase transition under the influence of diffuse far-ultraviolet (FUV) radiation fields and cosmic-ray backgrounds. We explore the effects of different FUV intensities, including a model with a radial gradient designed to mimic the Milky Way. The effects of cosmic rays, including radial gradients in their heating and ionization rates, are also explored. The final simulations in this series achieve 4 pc resolution across the ˜20 kpc global disk diameter, with heating and cooling followed down to temperatures of ˜10 K. The disks are evolved for 300 Myr, which is enough time for the ISM to achieve a quasi-statistical equilibrium. In particular, the mass fraction of molecular gas is stabilized by ˜200 Myr. Additional global ISM properties are analyzed. Giant molecular clouds (GMCs) are also identified and the statistical properties of their populations are examined. GMCs are tracked as the disks evolve. GMC collisions, which may be a means of triggering star cluster formation, are counted and their rates are compared with analytic models. Relatively frequent GMC collision rates are seen in these simulations, and their implications for understanding GMC properties, including the driving of internal turbulence, are discussed.

Far-UV, visible, and near-IR reflectance spectra of frosts of H2O, CO2, NH3 and SO2

NASA Technical Reports Server (NTRS)

Hapke, B.; Wells, E.; Wagner, J.; Partlow, W.

1981-01-01

Measurements in the 0.1-2.5 micron range are presented for the reflectance spectra of the frosts of several volatiles pertinent to the study of comet nuclei. The frost spectra have distinctive features permitting their identification by spectroscopic reflectance remote sensing, notably in the far UV. It is found that: (1) H2O has a minimum at 0.16 microns and a maximum at 0.13 microns; (2) CO2 has minima near 0.21, 0.18 and 0.125 microns, with maxima at 0.19, 0.135 and 0.120 microns; (3) NH3 is bright at wavelengths longer than 0.21 microns, where reflectance drops to a value of only a few per cent at shorter wavelengths; (4) SO2 has a sharp drop at 0.32 microns, with a minimum at 0.18 microns and a maximum at 0.13 microns. The features in the frost spectra largely correspond to absorption line bands in the gas phase.

The ultraviolet radiation environment in the habitable zones around low-mass exoplanet host stars

NASA Astrophysics Data System (ADS)

France, Kevin; Linsky, Jeffrey L.; Loyd, R. O. Parke

2014-11-01

The EUV (200-911 Å), FUV (912-1750 Å), and NUV (1750-3200 Å) spectral energy distribution of exoplanet host stars has a profound influence on the atmospheres of Earth-like planets in the habitable zone. The stellar EUV radiation drives atmospheric heating, while the FUV (in particular, Ly α) and NUV radiation fields regulate the atmospheric chemistry: the dissociation of H2O and CO2, the production of O2 and O3, and may determine the ultimate habitability of these worlds. Despite the importance of this information for atmospheric modeling of exoplanetary systems, the EUV/FUV/NUV radiation fields of cool (K and M dwarf) exoplanet host stars are almost completely unconstrained by observation or theory. We present observational results from a Hubble Space Telescope survey of M dwarf exoplanet host stars, highlighting the importance of realistic UV radiation fields for the formation of potential biomarker molecules, O2 and O3. We conclude by describing preliminary results on the characterization of the UV time variability of these sources.

Study of UV surface plasmons on metallic nanostructures and its applications to nanophotonics

NASA Astrophysics Data System (ADS)

Zhou, Liangcheng

Modern nanotechnology requires the characterization ability in the order of 100 nm or smaller. This resolution requirement cannot be met by using conventional optical microscopy. Nowadays, the mainstream technique that is universally adopted to characterize optical properties on this length scale is Near-field Scanning Optical Microscopy (NSOM). In the effort to improve the resolution and efficiency of NSOM techniques, both nanoscopic fabrication and imaging techniques are critical because the light field strongly intereacts with the metallic NSOM probe or other surfaces to form surface plasmons (SPs). However, much is still unknown about the behavior of light interacting with metallic nanostructures. This calls for research that develops the tool set, methodology and that includes both experimental characterization, and numerical simulations, for the investigation of SPs. The short wavelength of UV light makes it particularly desirable for many industrial processes. So far, little research has been carried out to understand surface plasmon in the UV spectral region. Like conventional optics, UV SPs have unique properties and optical behavior. For this purpose, we modified our existing NSOM into a Photon Scanning Tunneling Microscope (PTSM) and demonstrate its power for the imaging of UV SPs. We present what we believe to be the first direct mapping of the UV SPs on an Al2O3/Al surface. UV SP modes launched by one-dimensional slits or two-dimensional groove arrays and corresponding interference phenomenon were both observed. We then use the same methodology in the engineering of optimized nano aperture such as UV bowtie nanoantenna. For the latter, we find a strong UV intensity profile which is localized to less than 50nm caused by a localized surface plasmon resonance. The relationship of optical field enhancement and antenna geometric shape is studied using numerical simulations and NSOM experiments. In another project, we examine the propagation of light from

COS FUV Focus Sweep for G140L/800

NASA Astrophysics Data System (ADS)

Fischer, William J.

2017-08-01

COS cenwave G140L/800 will place wavelengths from 800 to 1950 A on segment A, with coverage about 300 A blueward of G140L/1105, and it lacks the gap between segments that affects G140L/1280. It is optimized to reduce astigmatism in the region below 1100 A, giving increased sensitivity at these wavelengths compared to 1280/B, due to the lower background. This program is designed to determine the best focus of the new cenwave at COS FUV Lifetime Position 4. We will check focus steps from -1000 to +1000 relative to the predicted best focus of -1087 (absolute steps of -2087 to -87), which was determined by extrapolation from the LP4 focuses for existing G140L cenwaves 1105 and 1280. We will increment the focus in steps of 200, or 100 near the center of the range, as is typical for focus sweeps. We will optimize the spectral resolution as well as the cross-dispersion width at short wavelengths, since a low cross-dispersion width below 1100 A is intended to be a unique benefit of this mode. The target is AzV 75, as in previous G140L focus sweeps such as PID 14874. The exposure time at each step is 940 s in order to obtain sufficient S/N below 1100 A. The throughput there is relatively low, but the new cenwave is intended to facilitate science in this range.

Preillumination of lettuce seedlings with red light enhances the resistance of photosynthetic apparatus to UV-A.

PubMed

Kreslavski, Vladimir D; Lyubimov, Valery Yu; Shirshikova, Galina N; Shmarev, Alexander N; Kosobryukhov, Anatoly A; Schmitt, Franz-Josef; Friedrich, Thomas; Allakhverdiev, Suleyman I

2013-05-05

Seedlings of 10-day-old lettuce (Lactuca sativa L., cultivar Berlin) were preilluminated by low intensity red light (λmax=660 nm, 10 min, 5 μmol quanta m(-2) s(-1)) and far-red light (λmax=730 nm, 10 min, 5 μmol quanta m(-2) s(-1)) to study the effect of pre-treatment on photosynthesis, photochemical activity of photosystem II (PSII), the contents of photosynthetic and UV-A-absorbing pigments (UAPs) and H2O2, as well as total and ascorbate peroxidase activities in cotyledonary leaves of seedlings exposed to UV-A. UV radiation reduced the photosynthetic rate (Pn), the activity of PSII, and the contents of Chl a and b, carotenoids and UAPs in the leaves, but increased the content of H2O2 and the total peroxidase activity. Preillumination with red light removed these effects of UV. In turn, the illumination with red light, then far-red light removed the effect of the red light. Illumination with red light alone increased the content of UAPs, as well as peroxidase activity. It is suggested that higher resistance of the lettuce photosynthetic apparatus to UV-A radiation is associated with involvement of the active form of phytochrome B, thereby increasing peroxidase activities as well as UAPs and saving preservation of photosynthetic pigment contents due to pre-illumination with red light. Copyright © 2013 Elsevier B.V. All rights reserved.

Two UV colours of the central part of M 31

NASA Technical Reports Server (NTRS)

Deharveng, J. M.; Laget, M.; Monnet, G.; Vuillemin, A.

1976-01-01

Two photographs of the galaxy M 31 have been obtained in the far UV with a Faust rocket experiment and in the near UV with the S 183 experiment aboard Skylab. Only the central part of the galaxy is detected. Reductions provide both the energy received and the angular area over M 31 from which it is emitted. The UV flux is brighter than expected from extrapolation of the visible spectrum. The distribution below 300 A is rather flat and different from previous OAO-2 observations. These results, combined with Lyman continuum flux evaluation, are used to discuss the temperature and the age of the stars which may be responsible for this anomalous UV distribution.

Germicidal Efficacy and Mammalian Skin Safety of 222-nm UV Light

PubMed Central

Buonanno, Manuela; Ponnaiya, Brian; Welch, David; Stanislauskas, Milda; Randers-Pehrson, Gerhard; Smilenov, Lubomir; Lowy, Franklin D.; Owens, David M.; Brenner, David J.

2017-01-01

We have previously shown that 207-nm ultraviolet (UV) light has similar antimicrobial properties as typical germicidal UV light (254 nm), but without inducing mammalian skin damage. The biophysical rationale is based on the limited penetration distance of 207-nm light in biological samples (e.g. stratum corneum) compared with that of 254-nm light. Here we extended our previous studies to 222-nm light and tested the hypothesis that there exists a narrow wavelength window in the far-UVC region, from around 200–222 nm, which is significantly harmful to bacteria, but without damaging cells in tissues. We used a krypton-chlorine (Kr-Cl) excimer lamp that produces 222-nm UV light with a bandpass filter to remove the lower- and higher-wavelength components. Relative to respective controls, we measured: 1. in vitro killing of methicillin-resistant Staphylococcus aureus (MRSA) as a function of UV fluence; 2. yields of the main UV-associated premutagenic DNA lesions (cyclobutane pyrimidine dimers and 6-4 photoproducts) in a 3D human skin tissue model in vitro; 3. eight cellular and molecular skin damage endpoints in exposed hairless mice in vivo. Comparisons were made with results from a conventional 254-nm UV germicidal lamp used as positive control. We found that 222-nm light kills MRSA efficiently but, unlike conventional germicidal UV lamps (254 nm), it produces almost no premutagenic UV-associated DNA lesions in a 3D human skin model and it is not cytotoxic to exposed mammalian skin. As predicted by biophysical considerations and in agreement with our previous findings, far-UVC light in the range of 200–222 nm kills bacteria efficiently regardless of their drug-resistant proficiency, but without the skin damaging effects associated with conventional germicidal UV exposure. PMID:28225654

Germicidal Efficacy and Mammalian Skin Safety of 222-nm UV Light.

PubMed

Buonanno, Manuela; Ponnaiya, Brian; Welch, David; Stanislauskas, Milda; Randers-Pehrson, Gerhard; Smilenov, Lubomir; Lowy, Franklin D; Owens, David M; Brenner, David J

2017-04-01

We have previously shown that 207-nm ultraviolet (UV) light has similar antimicrobial properties as typical germicidal UV light (254 nm), but without inducing mammalian skin damage. The biophysical rationale is based on the limited penetration distance of 207-nm light in biological samples (e.g. stratum corneum) compared with that of 254-nm light. Here we extended our previous studies to 222-nm light and tested the hypothesis that there exists a narrow wavelength window in the far-UVC region, from around 200-222 nm, which is significantly harmful to bacteria, but without damaging cells in tissues. We used a krypton-chlorine (Kr-Cl) excimer lamp that produces 222-nm UV light with a bandpass filter to remove the lower- and higher-wavelength components. Relative to respective controls, we measured: 1. in vitro killing of methicillin-resistant Staphylococcus aureus (MRSA) as a function of UV fluence; 2. yields of the main UV-associated premutagenic DNA lesions (cyclobutane pyrimidine dimers and 6-4 photoproducts) in a 3D human skin tissue model in vitro; 3. eight cellular and molecular skin damage endpoints in exposed hairless mice in vivo. Comparisons were made with results from a conventional 254-nm UV germicidal lamp used as positive control. We found that 222-nm light kills MRSA efficiently but, unlike conventional germicidal UV lamps (254 nm), it produces almost no premutagenic UV-associated DNA lesions in a 3D human skin model and it is not cytotoxic to exposed mammalian skin. As predicted by biophysical considerations and in agreement with our previous findings, far-UVC light in the range of 200-222 nm kills bacteria efficiently regardless of their drug-resistant proficiency, but without the skin damaging effects associated with conventional germicidal UV exposure.

Charge coupled devices vs. microchannel plates in the extreme and far ultraviolet - A comparison based on the latest laboratory measurements

NASA Technical Reports Server (NTRS)

Vallerga, J.; Lampton, M.

1988-01-01

While microchannel plates (MCPs) have been established as imaging photon counters in the EUV and FUV for some years, CCDs are associated with low light level sensing at visible and near-IR wavelengths. Attention is presently given to recent proposals for CCDs' use as EUV and FUV detectors with quantum efficiencies sometimes exceeding those of MCPs; quantum resolution, format size, dynamic range, and long-term stability are also used as bases of comparison, for the cases of both space-based astronomical and spectroscopic applications.

Development of High-Resolution UV-VIS Diagnostics for Space Plasma Simulation

NASA Astrophysics Data System (ADS)

Taylor, Andrew; Batishchev, Oleg

2012-10-01

Non-invasive far-UV-VIS plasma emission allows remote diagnostics of plasma, which is particularly important for space application. Accurate vacuum tank space plasma simulations require monochromators with high spectral resolution (better than 0.01A) to capture important details of atomic and ionic lines, such as Ly-alpha, etc. We are building a new system based on the previous work [1], and will discuss the development of a spectrometry system that combines a single-pass vacuum far-UV-NIR spectrometer and a tunable Fabry-Perot etalon. [4pt] [1] O. Batishchev and J.L. Cambier, Experimental Study of the Mini-Helicon Thruster, Air Force Research Laboratory Report, AFRL-RZ-ED-TR-2009-0020, 2009.

Exploring the Time Evolution of Cool Metallic Absorption Features in UV Burst Spectra

NASA Astrophysics Data System (ADS)

Belmes, K.; Madsen, C. A.; DeLuca, E.

2017-12-01

UV bursts are compact brightenings in active regions that appear in UV images. They are identified through three spectroscopic features: (1) broadening and intensification of NUV/FUV emission lines, (2) the presence of optically thin Si IV emission, and (3) the presence of absorption features from cool metallic ions. Properties (2) and (3) imply that bursts exist at transition region temperatures (≥ 80,000 K) but are located in the cooler lower chromosphere ( 5,000 K). Their energetic and dynamical properties remain poorly constrained. Improving our understanding of this phenomena could help us further constrain the energetic and dynamical properties of the chromosphere, as well as give us insight into whether or not UV bursts contribute to chromospheric and/or coronal heating. We analyzed the time evolution of UV bursts using spectral data from the Interface Region Imaging Spectrograph (IRIS). We inspected Si IV 1393.8 Å line profiles for Ni II 1393.3 Å absorption features to look for signs of heating. Weakening of absorption features over time could indicate heating of the cool ions above the burst, implying that thermal energy from the burst could rapidly conduct upward through the chromosphere. To detect the spectral profiles corresponding to bursts, we applied a four-parameter Gaussian fit to every profile in each observation and took cuts in parameter space to isolate the bursts. We then manually reviewed the remaining profiles by looking for a statistically significant appearance of Ni II 1393.3 Å absorption. We quantified these absorption features by normalizing the Si IV 1393.8 Å emission profiles and measuring the maximum fractional extinction in each. Our preliminary results indicate that Ni II 1393.3 Å absorption may undergo a cycle of strengthening and weakening throughout a burst's lifetime. However, further investigation is needed for confirmation. This work is supported by the NSF-REU solar physics program at SAO, grant number AGS-1560313.

EXPERIMENT - APOLLO 16 (UV)

NASA Image and Video Library

1972-06-06

S72-40821 (21 April 1972) --- An artificially reproduced color enhancement of a ten-minute far-ultraviolet exposure of Earth, taken with a filter which blocks the glow caused by atomic hydrogen but which transmits the glow caused by atomic oxygen and molecular nitrogen. Note that airglow emission bands are visible on the night side of Earth, one roughly centered between the two polar auroral zones and one at an angle to this extending northward toward the sunlit side of Earth. The UV camera was operated by astronaut John W. Young on the Apollo 16 lunar landing mission. It was designed and built at the Naval Research Laboratory, Washington, D.C. EDITOR'S NOTE: The photographic number of the original black & white UV camera photograph, from which this artificially reproduced version was made, is AS16-123-19657.

The Hubble Spectroscopic Legacy Archive

NASA Astrophysics Data System (ADS)

Peeples, M.; Tumlinson, J.; Fox, A.; Aloisi, A.; Fleming, S.; Jedrzejewski, R.; Oliveira, C.; Ayres, T.; Danforth, C.; Keeney, B.; Jenkins, E.

2017-04-01

With no future space ultraviolet instruments currently planned, the data from the UV spectrographs aboard the Hubble Space Telescope have a legacy value beyond their initial science goals. The goal of the Hubble Spectroscopic Legacy Archive(HSLA) is to provide to the community new science-grade combined spectra for all publicly available data obtained by the Cosmic Origins Spectrograph (COS)and the Space Telescope Imaging Spectrograph (STIS). These data are packaged into "smart archives" according to target type and scientific themes to facilitate the construction of archival samples for common science uses. A new "quick look" capability makes the data easy for users to quickly access, assess the quality of,and download for archival science. The first generation of these products for the far-ultraviolet (FUV) modes of COS was made available online via the Mikulski Archive for Space Telescopes (MAST) in early 2016 and updated in early 2017; future releases will include COS/NUV and STIS/UV data.

UV filters for lighting of plants

NASA Astrophysics Data System (ADS)

Doehring, T.; Koefferlein, M.; Thiel, S.; Seidlitz, H. K.; Payer, H. D.

1994-03-01

The wavelength dependent interaction of biological systems with radiation is commonly described by appropriate action spectra. Particularly effective plant responses are obtained for ultraviolet (UV) radiation. Excess shortwave UV-B radiation will induce genetic defects and plant damage. Besides the ecological discussion of the deleterious effects of the excess UV radiation there is increasing interest in horticultural applications of this spectral region. Several metabolic pathways leading to valuable secondary plant products like colors, odors, taste, or resulting in mechanical strength and vitality are triggered by UV radiation. Thus, in ecologically as well as in economically oriented experiments the exact generation and knowledge of the spectral irradiance, particularly near the UV absorption edge, is essential. The ideal filter 'material' to control the UV absorption edge would be ozone itself. However, due to problems in controlling the toxic and chemically aggressive, instable gas, only rather 'small ozone filters' have been realized so far. In artificial plant lighting conventional solid filter materials such as glass sheets and plastic foils (celluloseacetate or cellulosetriacetate) which can be easily handled have been used to absorb the UV-C and the excess shortwave UV-B radiation of the lamp emissions. Different filter glasses are available which provide absorption properties suitable for gradual changes of the spectral UV-B illumination of artificial lighting. Using a distinct set of lamps and filter glasses an acceptable simulation of the UV-B part of natural global radiation can be achieved. The aging of these and other filter materials under the extreme UV radiation in the lamphouse of a solar simulator is presently unavoidable. This instability can be dealt with only by a precise spectral monitoring and by replacing the filters accordingly. For this reason attempts would be useful to develop real ozone filters which can replace glass filters. In

UV filters for lighting of plants

NASA Technical Reports Server (NTRS)

Doehring, T.; Koefferlein, M.; Thiel, S.; Seidlitz, H. K.; Payer, H. D.

1994-01-01

The wavelength dependent interaction of biological systems with radiation is commonly described by appropriate action spectra. Particularly effective plant responses are obtained for ultraviolet (UV) radiation. Excess shortwave UV-B radiation will induce genetic defects and plant damage. Besides the ecological discussion of the deleterious effects of the excess UV radiation there is increasing interest in horticultural applications of this spectral region. Several metabolic pathways leading to valuable secondary plant products like colors, odors, taste, or resulting in mechanical strength and vitality are triggered by UV radiation. Thus, in ecologically as well as in economically oriented experiments the exact generation and knowledge of the spectral irradiance, particularly near the UV absorption edge, is essential. The ideal filter 'material' to control the UV absorption edge would be ozone itself. However, due to problems in controlling the toxic and chemically aggressive, instable gas, only rather 'small ozone filters' have been realized so far. In artificial plant lighting conventional solid filter materials such as glass sheets and plastic foils (celluloseacetate or cellulosetriacetate) which can be easily handled have been used to absorb the UV-C and the excess shortwave UV-B radiation of the lamp emissions. Different filter glasses are available which provide absorption properties suitable for gradual changes of the spectral UV-B illumination of artificial lighting. Using a distinct set of lamps and filter glasses an acceptable simulation of the UV-B part of natural global radiation can be achieved. The aging of these and other filter materials under the extreme UV radiation in the lamphouse of a solar simulator is presently unavoidable. This instability can be dealt with only by a precise spectral monitoring and by replacing the filters accordingly. For this reason attempts would be useful to develop real ozone filters which can replace glass filters. In

Mirror coatings for large aperture UV optical infrared telescope optics

NASA Astrophysics Data System (ADS)

Balasubramanian, Kunjithapatham; Hennessy, John; Raouf, Nasrat; Nikzad, Shouleh; Del Hoyo, Javier; Quijada, Manuel

2017-09-01

Large space telescope concepts such as LUVOIR and HabEx aiming for observations from far UV to near IR require advanced coating technologies to enable efficient gathering of light with important spectral signatures including those in far UV region down to 90nm. Typical Aluminum mirrors protected with MgF2 fall short of the requirements below 120nm. New and improved coatings are sought to protect aluminum from oxidizing readily in normal environment causing severe absorption and reduction of reflectance in the deep UV. Choice of materials and the process of applying coatings present challenges. Here we present the progress achieved to date with experimental investigations of coatings at JPL and at GSFC and discuss the path forward to achieve high reflectance in the spectral region from 90 to 300nm without degrading performance in the visible and NIR regions taking into account durability concerns when the mirrors are exposed to normal laboratory environment as well as high humidity conditions. Reflectivity uniformity required on these mirrors is also discussed.

Optical-to-UV correlations and particle fluxes for M dwarf exoplanet host stars

NASA Astrophysics Data System (ADS)

Youngblood, Allison

2017-01-01

UV stellar radiation can significantly impact planetary atmospheres through heating and photochemistry, even regulating production of potential biomarkers. M dwarfs emit the majority of their UV radiation in the form of emission lines, and the incident UV radiation on habitable-zone planets is significant owing to their small orbital radii. Only recently have the UV spectral energy distributions (SEDs) of average M dwarfs been explored (e.g., the MUSCLES Treasury Survey). Emission lines tracing hot plasma in the stellar chromosphere and transition region dominate the far-UV spectra, even for optically inactive M dwarfs (i.e., those displaying Hα absorption spectra). Lyα (1216 Å) is the strongest of the UV emission lines, but resonant scattering from the interstellar medium makes direct observations of the intrinsic Lyα emission of even nearby stars challenging. I reconstruct the intrinsic Lyα profiles using an MCMC technique and use them to estimate the extreme-UV SED.Monitoring the long-term (years-to-decades) UV activity of M dwarfs will be important for assessing the potential habitability of short-period planets, but will only be feasible from the ground via optical proxies. Therefore, I also quantify correlations between UV and optical emission lines of the MUSCLES stars and other M dwarfs, for use when direct UV observations of M dwarf exoplanet host stars are not available. Recent habitability studies of M dwarf exoplanets have sought to address the impact of frequent flaring and are just beginning to include the damaging impact of stellar energetic particles that are typically associated with large flares. Working under the necessary assumption of solar-like particle production, I present a new technique for estimating >10 MeV proton flux during far-UV flares, and analyze a sample of the flares observed in the MUSCLES Treasury Survey.

Testing the molecular-hydrogen Kennicutt-Schmidt law in the low-density environments of extended ultraviolet disc galaxies

NASA Astrophysics Data System (ADS)

Watson, Linda C.; Martini, Paul; Lisenfeld, Ute; Böker, Torsten; Schinnerer, Eva

2016-01-01

Studying star formation beyond the optical radius of galaxies allows us to test empirical relations in extreme conditions with low average gas density and low molecular fraction. Previous studies discovered galaxies with extended ultraviolet (XUV) discs, which often contain star-forming regions with lower Hα-to-far-UV (FUV) flux ratios compared to inner disc star-forming regions. However, most previous studies lack measurements of molecular gas, which is presumably the component of the interstellar medium out of which stars form. We analysed published CO measurements and upper limits for 15 star-forming regions in the XUV or outer disc of three nearby spiral galaxies and a new CO upper limit from the IRAM (Institut de Radioastronomie Millimétrique) 30 m telescope in one star-forming region at r = 3.4r25 in the XUV disc of NGC 4625. We found that the star-forming regions are in general consistent with the same molecular-hydrogen Kennicutt-Schmidt law that applies within the optical radius, independent of whether we used Hα or FUV as the star formation rate (SFR) tracer. However, a number of the CO detections are significantly offset towards higher SFR surface density for their molecular-hydrogen surface density. Deeper CO data may enable us to use the presence or absence of molecular gas as an evolutionary probe to break the degeneracy between age and stochastic sampling of the initial mass function as the explanation for the low Hα-to-FUV flux ratios in XUV discs.

An Accurate Measurement of the IGM HeII Lyman Alpha Forest toward a Newly Discovered UV-bright Quasar at z>3.5

NASA Astrophysics Data System (ADS)

Worseck, Gabor

2016-10-01

The advent of GALEX and COS have revolutionized our view of HeII reionization, the final major phase transition of the intergalactic medium. COS spectra of the HeII Lyman alpha forest have confirmed with high confidence the high HeII transmission that signifies the completion of HeII reionization at z 2.7. However, the handful of z>3.5 quasars observed to date show a set of HeII transmission 'spikes' and larger regions with non-zero transmission that suggest HeII reionization was well underway by z=4. This is in striking conflict with predictions from state-of-the-art radiative transfer simulations of a HeII reionization driven by bright quasars. Explaining these measurements may require either faint quasars or more exotic sources of hard photons at z>4, with concomitant implications for HI reionization. We propose here to observe J2354-2033, an FUV-bright quasar at z=3.786 that we recently discovered in a dedicated survey for likely HeII-transmitting quasars. With this COS/G140L spectrum, we would confirm that the quasar is valuable for studies of the HeII Lyman alpha forest by identifying possible interloping low-z HI absorbers, provide accurate measurements of the IGM HeII opacity, and provide only the third z>3.5 sightline that would allow for high-resolution G130M spectroscopy before the end of HST's mission. The proposed observations would mark only the fourth observation of the HeII Lyman alpha forest at z>3.7 and the source would be the 2nd-brightest known on the sky at these redshifts.

The Helix Nebula: Unraveling at the Seams

NASA Image and Video Library

2012-10-03

This image from NASA Spitzer and GALEX shows the Helix nebula, a dying star throwing a cosmic tantrum. In death, the star dusty outer layers are unraveling into space, glowing from the intense UV radiation being pumped out by the hot stellar core.

GAMA/H-ATLAS: common star formation rate indicators and their dependence on galaxy physical parameters

NASA Astrophysics Data System (ADS)

Wang, L.; Norberg, P.; Gunawardhana, M. L. P.; Heinis, S.; Baldry, I. K.; Bland-Hawthorn, J.; Bourne, N.; Brough, S.; Brown, M. J. I.; Cluver, M. E.; Cooray, A.; da Cunha, E.; Driver, S. P.; Dunne, L.; Dye, S.; Eales, S.; Grootes, M. W.; Holwerda, B. W.; Hopkins, A. M.; Ibar, E.; Ivison, R.; Lacey, C.; Lara-Lopez, M. A.; Loveday, J.; Maddox, S. J.; Michałowski, M. J.; Oteo, I.; Owers, M. S.; Popescu, C. C.; Smith, D. J. B.; Taylor, E. N.; Tuffs, R. J.; van der Werf, P.

2016-09-01

We compare common star formation rate (SFR) indicators in the local Universe in the Galaxy and Mass Assembly (GAMA) equatorial fields (˜160 deg2), using ultraviolet (UV) photometry from GALEX, far-infrared and sub-millimetre (sub-mm) photometry from Herschel Astrophysical Terahertz Large Area Survey, and Hα spectroscopy from the GAMA survey. With a high-quality sample of 745 galaxies (median redshift = 0.08), we consider three SFR tracers: UV luminosity corrected for dust attenuation using the UV spectral slope β (SFRUV, corr), Hα line luminosity corrected for dust using the Balmer decrement (BD) (SFRH α, corr), and the combination of UV and infrared (IR) emission (SFRUV + IR). We demonstrate that SFRUV, corr can be reconciled with the other two tracers after applying attenuation corrections by calibrating Infrared excess (IRX; I.e. the IR to UV luminosity ratio) and attenuation in the Hα (derived from BD) against β. However, β, on its own, is very unlikely to be a reliable attenuation indicator. We find that attenuation correction factors depend on parameters such as stellar mass (M*), z and dust temperature (Tdust), but not on Hα equivalent width or Sérsic index. Due to the large scatter in the IRX versus β correlation, when compared to SFRUV + IR, the β-corrected SFRUV, corr exhibits systematic deviations as a function of IRX, BD and Tdust.

Search for X-ray Emission from AGB Stars in the Coronal Graveyard

NASA Astrophysics Data System (ADS)

Montez, Rodolfo

2013-10-01

Maser observations demonstrate the existence of magnetic fields in the circumstellar envelopes of AGB stars. However, thus far, only 2-3 AGB stars have exhibited evidence for coronal X-ray emission. We have demonstrated that only the sensitivity of modern X-ray telescopes can detect magnetically-induced coronal emission and have identified a sample of AGB stars which are ideal candidates to search for such emission. Specifically, we have selected a sample of AGB stars with SiO maser emission, UV emission in at least one of the GALEX bandpasses, and low mass loss rates. The four selected AGB stars provide a pilot sample that optimally probes for coronal activity beyond the giant phase and that provides valuable tests for the launching and shaping of AGB mass loss.

Atomic Oxygen Density Retrievals using FUV Observations by the Imaging Ultraviolet Spectrograph on MAVEN

NASA Astrophysics Data System (ADS)

Evans, J. Scott; Stevens, Michael H.; Schneider, Nicholas M.; Stewart, Ian; Deighan, Justin; Jain, Sonal Kumar; Eparvier, Francis; Thiemann, E. M.; Bougher, Stephen W.; Jakosky, Bruce

2016-10-01

We present the first direct retrievals of neutral atomic oxygen in Mars's upper atmosphere using daytime FUV periapse limb scan observations from 130 - 200 km tangent altitude. Atmospheric composition is inferred using the Atmospheric Ultraviolet Radiance Integrated Code [Strickland et al., 1999] adapted to the Martian atmosphere [Evans et al., 2015]. For our retrievals we use O I 135.6 nm emission observed by IUVS on MAVEN under daytime conditions (solar zenith angle < 60 degrees) over both northern and southern hemispheres (latitudes between -65 and +35 degrees) from October 2014 to August 2016. We investigate the sensitivity of atomic oxygen density retrievals to variability in solar irradiance, solar longitude, and local time. We compare our retrievals to predictions from the Mars Global Ionosphere-Thermosphere Model [MGITM, Bougher et al., 2015] and the Mars Climate Database [MCD, Forget et al., 1999] and quantify the differences throughout the altitude region of interest. The retrieved densities are used to characterize global transport of atomic oxygen in the Martian thermosphere.

Electronic structure, dielectric response, and surface charge distribution of RGD (1FUV) peptide.

PubMed

Adhikari, Puja; Wen, Amy M; French, Roger H; Parsegian, V Adrian; Steinmetz, Nicole F; Podgornik, Rudolf; Ching, Wai-Yim

2014-07-08

Long and short range molecular interactions govern molecular recognition and self-assembly of biological macromolecules. Microscopic parameters in the theories of these molecular interactions are either phenomenological or need to be calculated within a microscopic theory. We report a unified methodology for the ab initio quantum mechanical (QM) calculation that yields all the microscopic parameters, namely the partial charges as well as the frequency-dependent dielectric response function, that can then be taken as input for macroscopic theories of electrostatic, polar, and van der Waals-London dispersion intermolecular forces. We apply this methodology to obtain the electronic structure of the cyclic tripeptide RGD-4C (1FUV). This ab initio unified methodology yields the relevant parameters entering the long range interactions of biological macromolecules, providing accurate data for the partial charge distribution and the frequency-dependent dielectric response function of this peptide. These microscopic parameters determine the range and strength of the intricate intermolecular interactions between potential docking sites of the RGD-4C ligand and its integrin receptor.

Electronic Structure, Dielectric Response, and Surface Charge Distribution of RGD (1FUV) Peptide

PubMed Central

Adhikari, Puja; Wen, Amy M.; French, Roger H.; Parsegian, V. Adrian; Steinmetz, Nicole F.; Podgornik, Rudolf; Ching, Wai-Yim

2014-01-01

Long and short range molecular interactions govern molecular recognition and self-assembly of biological macromolecules. Microscopic parameters in the theories of these molecular interactions are either phenomenological or need to be calculated within a microscopic theory. We report a unified methodology for the ab initio quantum mechanical (QM) calculation that yields all the microscopic parameters, namely the partial charges as well as the frequency-dependent dielectric response function, that can then be taken as input for macroscopic theories of electrostatic, polar, and van der Waals-London dispersion intermolecular forces. We apply this methodology to obtain the electronic structure of the cyclic tripeptide RGD-4C (1FUV). This ab initio unified methodology yields the relevant parameters entering the long range interactions of biological macromolecules, providing accurate data for the partial charge distribution and the frequency-dependent dielectric response function of this peptide. These microscopic parameters determine the range and strength of the intricate intermolecular interactions between potential docking sites of the RGD-4C ligand and its integrin receptor. PMID:25001596

General Astrophysics Science Enabled by the HabEx Ultraviolet Spectrograph (UVS)

NASA Astrophysics Data System (ADS)

Scowen, Paul; Clarke, John; Gaudi, B. Scott; Kiessling, Alina; Martin, Stefan; Somerville, Rachel; Stern, Daniel; HabEx Science and Technology Definition Team

2018-01-01

The Habitable Exoplanet Imaging Mission (HabEx) is one of the four large mission concepts being studied by NASA as input to the upcoming 2020 Decadal Survey. The mission implements two world-class General Astrophysics instruments as part of its complement of instrumentation to enable compelling science using the 4m aperture. The Ultraviolet Spectrograph has been designed to address cutting edge far ultraviolet (FUV) science that has not been possible with the Hubble Space Telescope, and to open up a wide range of capabilities that will advance astrophysics as we look into the 2030s. Our poster discusses some of those science drivers and possible applications, which range from Solar System science, to nearby and more distant studies of star formation, to studies of the circumgalactic and intergalactic mediums where the ecology of mass and energy transfer are vital to understanding stellar and galactic evolution. We discuss the performance features of the instrument that include a large 3’x3’ field of view for multi-object spectroscopy, and some 20 grating modes for a variety of spectral resolution and coverage.

New binaries among UV-selected, hot subdwarf stars and population properties

NASA Astrophysics Data System (ADS)

Kawka, A.; Vennes, S.; O'Toole, S.; Németh, P.; Burton, D.; Kotze, E.; Buckley, D. A. H.

2015-07-01

We have measured the orbital parameters of seven close binaries, including six new objects, in a radial velocity survey of 38 objects comprising a hot subdwarf star with orbital periods ranging from ˜0.17 to 3 d. One new system, GALEX J2205-3141, shows reflection on an M dwarf companion. Three other objects show significant short-period variations, but their orbital parameters could not be constrained. Two systems comprising a hot subdwarf paired with a bright main-sequence/giant companion display short-period photometric variations possibly due to irradiation or stellar activity and are also short-period candidates. All except two candidates were drawn from a selection of subluminous stars in the Galaxy Evolution Explorer ultraviolet sky survey. Our new identifications also include a low-mass subdwarf B star and likely progenitor of a low-mass white dwarf (GALEX J0805-1058) paired with an unseen, possibly substellar, companion. The mass functions of the newly identified binaries imply minimum secondary masses ranging from 0.03 to 0.39 M⊙. Photometric time series suggest that, apart from GALEX J0805-1058 and J2205-3141, the companions are most likely white dwarfs. We update the binary population statistics: close to 40 per cent of hot subdwarfs have a companion. Also, we found that the secondary mass distribution shows a low-mass peak attributed to late-type dwarfs, and a higher mass peak and tail distribution attributed to white dwarfs and a few spectroscopic composites. Also, we found that the population kinematics imply an old age and include a few likely halo population members.

Nearby Newborns

NASA Image and Video Library

2004-12-21

This image shows six of the three-dozen "ultraviolet luminous galaxies" spotted in our corner of the universe by NASA's Galaxy Evolution Explorer. These massive galaxies greatly resemble newborn galaxies that were common in the early universe. The discovery came as a surprise, because astronomers had thought that the universe's "birth-rate" had declined, and that massive galaxies were no longer forming. The galaxies, located in the center of each panel, were discovered after the Galaxy Evolution Explorer scanned a large portion of the sky with its highly sensitive ultraviolet-light detectors. Because young stars pack most of their light into ultraviolet wavelengths, young galaxies appear to the Galaxy Evolution Explorer like diamonds in a field of stones. Astronomers mined for these rare "gems" before, but missed them because they weren't able to examine a large enough slice of the sky. The Galaxy Evolution Explorer surveyed thousands of nearby galaxies before finding three-dozen newborns. While still relatively close in astronomical terms, these galaxies are far enough away to appear small to the Galaxy Evolution Explorer. Clockwise beginning from the upper left, they are called: GALEX_J232539.24+004507.1, GALEX_J231812.98-004126.1, GALEX_J015028.39+130858.5, GALEX_J021348.52+125951.3, GALEX_J143417.15+020742.5, GALEX_J020354.02-092452.5. http://photojournal.jpl.nasa.gov/catalog/PIA07143

The Ultraviolet Spectrograph (UVS) on Juno

NASA Astrophysics Data System (ADS)

Gladstone, G. R.; Persyn, S.; Eterno, J.; Slater, D. C.; Davis, M. W.; Versteeg, M. H.; Persson, K. B.; Siegmund, O. H.; Marquet, B.; Gerard, J.; Grodent, D. C.

2008-12-01

Juno, a NASA New Frontiers mission, plans for launch in August 2011, a 5-year cruise (including a flyby of Earth in October 2013 for a gravity boost), and 14 months around Jupiter after arriving in August 2016. The spinning (2 RPM), solar-powered Juno will study Jupiter from a highly elliptical orbit, in which the spacecraft (for about 6 hours once every 11 days) dives down over the north pole, skims the outermost atmosphere, and rises back up over the south pole. This orbit allows Juno avoid most of the intense particle radiation surrounding the planet and provides an excellent platform for investigating Jupiter's polar magnetosphere. Part of the exploration of Jupiter's polar magnetosphere will involve remote sensing of the far-ultraviolet H and H2 auroral emissions, plus gases such as methane and acetylene which add their absorption signature to the H2 emissions. This hydrocarbon absorption can be used to estimate the energy of the precipitating electrons; since more energetic electrons penetrate deeper into the atmosphere and the UV emissions they produce will show more absorption. Juno will carry an Ultraviolet Spectrograph (UVS) to make spectral images of Jupiter's aurora. UVS is a UV imaging spectrograph sensitive to both extreme and far ultraviolet emissions in the 70-205~nm range that will characterize the morphology and spectral nature of Jupiter's auroral emissions. Juno UVS consists of two separate sections: a dedicated telescope/spectrograph assembly and a vault electronics box. The telescope/spectrograph assembly contains a telescope which feeds a 0.15-m Rowland circle spectrograph. The telescope has an input aperture 40×40~mm2 and uses an off-axis parabolic primary mirror. A flat scan mirror situated at the front end of the telescope (used to target specific auroral features at up to ±30° perpendicular to the Juno spin plane) directs incoming light to the primary. The light is then focused onto the spectrograph entrance slit, which has a 'dog

MAMA detector systems - A status report

NASA Technical Reports Server (NTRS)

Timothy, J. Gethyn; Morgan, Jeffrey S.; Slater, David C.; Kasle, David B.; Bybee, Richard L.

1989-01-01

Third-generation, 224 x 960 and 360 x 1024-pixel multianode microchannel (MAMA) detectors are under development for satellite-borne FUV and EUV observations, using pixel dimensions of 25 x 25 microns. An account is presently given of the configurations, modes of operation, and recent performance data of these systems. At UV and visible wavelengths, these MAMAs employ a semitransparent, proximity-focused photocathode structure. At FUV and EUV wavelengths below about 1500 A, opaque alkali-halide photocathodes deposited directly on the front surface of the MCP furnish the best detective quantum efficiencies.

Research on vacuum utraviolet calibration technology

NASA Astrophysics Data System (ADS)

Wang, Jiapeng; Gao, Shumin; Sun, Hongsheng; Chen, Yinghang; Wei, Jianqiang

2014-11-01

Importance of extreme ultraviolet (EUV) and far ultraviolet (FUV) calibration is growing fast as vacuum ultraviolet payloads are wildly used in national space plan. A calibration device is established especially for the requirement of EUV and FUV metrology and measurement. Spectral radiation and detector relative spectral response at EUV and FUV wavelengths can be calibrated with accuracy of 26% and 20%, respectively. The setup of the device, theoretical model and value retroactive method are introduced and measurement of detector relative spectral response from 30 nm to 200 nm is presented in this paper. The calibration device plays an important role in national space research.

Potential of far-ultraviolet absorption spectroscopy as a highly sensitive qualitative and quantitative analysis method for polymer films, part I: classification of commercial food wrap films.

PubMed

Sato, Harumi; Higashi, Noboru; Ikehata, Akifumi; Koide, Noriko; Ozaki, Yukihiro

2007-07-01

The aim of the present study is to propose a totally new technique for the utilization of far-ultraviolet (UV) spectroscopy in polymer thin film analysis. Far-UV spectra in the 120-300 nm region have been measured in situ for six kinds of commercial polymer wrap films by use of a novel type of far-UV spectrometer that does not need vacuum evaporation. These films can be straightforwardly classified into three groups, polyethylene (PE) films, polyvinyl chloride (PVC) films, and polyvinylidene chloride (PVDC) films, by using the raw spectra. The differences in the wavelength of the absorption band due to the sigma-sigma* transition of the C-C bond have been used for the classification of the six kinds of films. Using this method, it was easy to distinguish the three kinds of PE films and to separate the two kinds of PVDC films. Compared with other spectroscopic methods, the advantages of this technique include nondestructive analysis, easy spectral measurement, high sensitivity, and simple spectral analysis. The present study has demonstrated that far-UV spectroscopy is a very promising technique for polymer film analysis.

NASA Ames UV-LED Poster Overview

NASA Technical Reports Server (NTRS)

Jaroux, Belgacem Amar

2015-01-01

UV-LED is a small satellite technology demonstration payload being flown on the Saudisat-4 spacecraft that is demonstrating non-contacting charge control of an isolated or floating mass using new solid-state ultra-violet light emitting diodes (UV-LEDs). Integrated to the rest of the spacecraft and launched on a Dnepr in June 19, 2014, the project is a collaboration between the NASA Ames Research Center (ARC), Stanford University, and King Abdulaziz City for Science and Technology (KACST). Beginning with its commissioning in December, 2015, the data collected by UV-LED have validated a novel method of charge control that will improve the performance of drag-free spacecraft allowing for concurrent science collection during charge management operations as well as reduce the mass, power and volume required while increasing lifetime and reliability of a charge management subsystem. UV-LED continues to operate, exploring new concepts in non-contacting charge control and collecting data crucial to understanding the lifetime of ultra-violet light emitting diodes in space. These improvements are crucial to the success of ground breaking missions such as LISA and BBO, and demonstrates the ability of low cost small satellite missions to provide technological advances that far exceed mission costs.

Frankenstein Galaxy

NASA Image and Video Library

2016-07-11

The galaxy UGC 1382 has been revealed to be far larger and stranger than previously thought. Astronomers relied on a combination of ground-based and space telescopes to uncover the true nature of this "Frankenstein galaxy." The composite image shows the same galaxy as viewed with different instruments. The component images are also available. In the image at left, UGC 1382 appears to be a simple elliptical galaxy, based on optical data from the Sloan Digital Sky Survey (SDSS). But spiral arms emerged when astronomers incorporated ultraviolet data from the Galaxy Evolution Explorer (GALEX) and deep optical data from SDSS, as seen in the middle image. Combining that with a view of low-density hydrogen gas (shown in green), detected at radio wavelengths by the Very Large Array, scientists discovered that UGC 1382 is a giant, and one of the largest isolated galaxies known. GALEX in particular was able detect very faint features because it operated from space, which is necessary for UV observations because ultraviolet light is absorbed by the Earth's atmosphere. Astronomers also used Stripe 82 of SDSS, a small region of sky where SDSS imaged the sky 80 times longer than the original standard SDSS survey. This enabled optical detection of much fainter features as well. http://photojournal.jpl.nasa.gov/catalog/PIA20695

Molecular line tracers of high-mass star forming regions

NASA Astrophysics Data System (ADS)

Nagy, Zsofia

2013-09-01

High-mass stars influence their environment in different ways including feedback via their far-UV radiation and mechanical feedback via shocks and stellar winds. The penetration of FUV photons into molecular clouds creates Photon Dominated Regions (PDRs) with different chemical layers where the mainly ionized medium changes into mainly molecular. Different chemical layers in PDRs are traced by different species observable at sub-mm and far-infrared wavelengths. In this thesis we present results from two molecular line surveys. One of them is the James Clerk Maxwell Telescope (JCMT) Spectral Legacy Survey (SLS) toward the luminous (>10^7 L_Sun), massive (~10^6 M_Sun), and distant (11.4 kpc) star-forming region W49A. The SLS images a 2x2 arcminute field around W49A in the 330-373 GHz frequency range. The detected molecular lines reveal a complex chemistry and the importance of FUV-irradiation and shocks in the heating and chemistry of the region. The other line survey presented in this thesis is part of the HEXOS (Herschel observations of EXtra-Ordinary Sources) key program using the Herschel Space Observatory and is toward the nearby (~420 pc) prototypical edge-on Orion Bar PDR and the dense molecular condensation Orion S. Reactive ions, such as CH+, SH+, and CO+, detected as a part of this line survey trace the warm (~500-1000 K) surface region of PDRs. Spectroscopic data from the HIFI and PACS instruments of Herschel give constraints on the chemistry and excitation of reactive ions in these regions.

Far-UV spectroscopy of two extremely hot, helium-rich white dwarfs

NASA Astrophysics Data System (ADS)

Werner, K.; Rauch, T.; Kruk, J. W.

2017-05-01

A large proportion of hot post-asymptotic giant branch stars and white dwarfs (WDs) are hydrogen-deficient. Two distinct evolutionary sequences have been identified. One of them comprises stars of spectral type [WC] and PG1159, and it originates from a late helium-shell flash, creating helium-rich stellar atmospheres with significant admixtures of carbon (up to about 50%, mass fraction). The other sequence comprises stars of spectral type O(He) and luminous subdwarf O stars which possibly are descendants of RCrB stars and extreme helium stars. Their carbon abundances are significantly lower (of the order of 1% or less) and it is thought that they originate from binary-star evolution (through merger or common-envelope evolution). Here we investigate two of the three hottest known helium-rich (DO) WDs (PG 1034+001 and PG 0038+199). They are the only ones for which spectra were recorded with the Far Ultraviolet Spectroscopic Explorer and the Hubble Space Telescope, allowing a comprehensive ultraviolet spectral analysis. We find effective temperatures of Teff = 115 000 ± 5000 K and 125 000 ± 5000 K, respectively, and a surface gravity of log g= 7 ± 0.5. In both stars, nitrogen is strongly oversolar while C and O are significantly subsolar. For all other assessed metals (Ne, Si, P, S, Ar, Fe, and Ni) we find abundances close to solar. We conclude that these WDs are immediate descendants of O(He) stars and, hence, result from close-binary evolution. Based on observations made with the NASA-CNES-CSA Far Ultraviolet Spectroscopic Explorer.

Monitoring the High-Energy Radiation Environment of Exoplanets Around Low-mass Stars with SPARCS (Star-Planet Activity Research CubeSat)

NASA Astrophysics Data System (ADS)

Shkolnik, Evgenya L.; Ardila, David; Barman, Travis; Beasley, Matthew; Bowman, Judd D.; Gorjian, Varoujan; Jacobs, Daniel; Jewell, April; Llama, Joe; Meadows, Victoria; Nikzad, Shouleh; Scowen, Paul; Swain, Mark; Zellem, Robert

2018-01-01

Roughly seventy-five billion M dwarfs in our galaxy host at least one small planet in the habitable zone (HZ). The stellar ultraviolet (UV) radiation from M dwarfs is strong and highly variable, and impacts planetary atmospheric loss, composition and habitability. These effects are amplified by the extreme proximity of their HZs (0.1–0.4 AU). Knowing the UV environments of M dwarf planets will be crucial to understanding their atmospheric composition and a key parameter in discriminating between biological and abiotic sources for observed biosignatures. The Star-Planet Activity Research CubeSat (SPARCS) will be a 6U CubeSat devoted to photometric monitoring of M stars in the far-UV and near-UV, measuring the time-dependent spectral slope, intensity and evolution of M dwarf stellar UV radiation. For each target, SPARCS will observe continuously over at least one complete stellar rotation (5 - 45 days). SPARCS will also advance UV detector technology by flying high quantum efficiency, UV-optimized detectors developed at JPL. These Delta-doped detectors have a long history of deployment demonstrating greater than five times the quantum efficiency of the detectors used by GALEX. SPARCS will pave the way for their application in missions like LUVOIR or HabEx, including interim UV-capable missions. SPARCS will also be capable of ‘target-of-opportunity’ UV observations for the rocky planets in M dwarf HZs soon to be discovered by NASA’s TESS mission, providing the needed UV context for the first habitable planets that JWST will characterize.Acknowledgements: Funding for SPARCS is provided by NASA’s Astrophysics Research and Analysis program, NNH16ZDA001N.

Aromatic Cluster Sensor of Protein Folding: Near-UV Electronic Circular Dichroism Bands Assigned to Fold Compactness.

PubMed

Farkas, Viktor; Jákli, Imre; Tóth, Gábor K; Perczel, András

2016-09-19

Both far- and near-UV electronic circular dichroism (ECD) spectra have bands sensitive to thermal unfolding of Trp and Tyr residues containing proteins. Beside spectral changes at 222 nm reporting secondary structural variations (far-UV range), L b bands (near-UV range) are applicable as 3D-fold sensors of protein's core structure. In this study we show that both L b (Tyr) and L b (Trp) ECD bands could be used as sensors of fold compactness. ECD is a relative method and thus requires NMR referencing and cross-validation, also provided here. The ensemble of 204 ECD spectra of Trp-cage miniproteins is analysed as a training set for "calibrating" Trp↔Tyr folded systems of known NMR structure. While in the far-UV ECD spectra changes are linear as a function of the temperature, near-UV ECD data indicate a non-linear and thus, cooperative unfolding mechanism of these proteins. Ensemble of ECD spectra deconvoluted gives both conformational weights and insight to a protein folding↔unfolding mechanism. We found that the L b 293 band is reporting on the 3D-structure compactness. In addition, the pure near-UV ECD spectrum of the unfolded state is described here for the first time. Thus, ECD folding information now validated can be applied with confidence in a large thermal window (5≤T≤85 °C) compared to NMR for studying the unfolding of Trp↔Tyr residue pairs. In conclusion, folding propensities of important proteins (RNA polymerase II, ubiquitin protein ligase, tryptase-inhibitor etc.) can now be analysed with higher confidence. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Far-ultraviolet absorption spectra of quasars: How to find missing hot gas and metals

NASA Technical Reports Server (NTRS)

Verner, D. A.; Tytler, David; Barthel, P. D.

1994-01-01

We show that some high-redshift QSO absorption systems that reveal only the H I Lyman series lines at wavelengths visible from the ground maybe a new class of ultra-high-ionization metal line systems, with metal lines in the far-UV region which is now being explored with satellites. At high temperatures or in intense radiation fields metal systems will not show the usual C IV absorption, and O VI will become the most prominent metal absorber. At still higher ionization, O IV also becomes weak and the strongest metal lines are from Ne VIII, Mg X and Si XII, which have doublets in the rangs 500-800 A. Hence very high ionization metal systems will not show metal lines in existing spectra. Recent X-ray observations show that galaxy halos contain hot gas, so we predict that far-UV spectra of QSOs will also show this gas.

Correlated variations of UV and radio emissions during an outstanding Jovian auroral event

NASA Technical Reports Server (NTRS)

Prange, R.; Zarka, P.; Ballester, G. E.; Livengood, T. A.; Denis, L.; Carr, T.; Reyes, F.; Bame, S. J.; Moos, H. W.

1993-01-01

An exceptional Jovian aurora was detected in the FUV on December 21, 1990, by means of Vilspa and Goddard Space Flight Center (GFSC) International Ultraviolet Explorer (IUE) observations. This event included intensification by a factor of three between December 20 and 21, leading to the brightest aurora identified in the IUE data analyzed, and, in the north, to a shift of the emission peak towards larger longitudes. The Jovian radio emission simultaneously recorded at decameter wavelengths in Nancay also exhibits significant changes, from a weak and short-duration emission on December 20 to a very intense one, lasting several hours, on December 21. Confirmation of this intense radio event is also found in the observations at the University of Florida on December 21. The emissions are identified as right-handed Io-independent 'A' (or 'non Io-A') components from the northern hemisphere. The radio source region deduced from the Nancay observations lies, for both days, close to the UV peak emission, exhibiting in particular a similar shift of the source region toward larger longitudes from one day to the next. A significant broadening of the radio source was also observed and it is shown that on both days, the extent of the radio source closely followed the longitude range for which the UV brightness exceeds a given threshold. The correlated variations, both in intensity and longitude, strongly suggest that a common cause triggered the variation of the UV and radio emissions during this exceptional event. On one hand, the variation of the UV aurora could possibly be interpreted according to the Prange and Elkhamsi (1991) model of diffuse multicomponent auroral precipitation (electron and ion): it would arise from an increase in the precipitation rate of ions together with an inward shift of their precipitation locus from L approximately equal 10 to L approximately equal 6. On the other hand, the analysis of Ulysses observations in the upstream solar wind suggests that

The WiggleZ Dark Energy Survey: final data release and the metallicity of UV-luminous galaxies

NASA Astrophysics Data System (ADS)

Drinkwater, Michael J.; Byrne, Zachary J.; Blake, Chris; Glazebrook, Karl; Brough, Sarah; Colless, Matthew; Couch, Warrick; Croton, Darren J.; Croom, Scott M.; Davis, Tamara M.; Forster, Karl; Gilbank, David; Hinton, Samuel R.; Jelliffe, Ben; Jurek, Russell J.; Li, I.-hui; Martin, D. Christopher; Pimbblet, Kevin; Poole, Gregory B.; Pracy, Michael; Sharp, Rob; Smillie, Jon; Spolaor, Max; Wisnioski, Emily; Woods, David; Wyder, Ted K.; Yee, Howard K. C.

2018-03-01

The WiggleZ Dark Energy Survey measured the redshifts of over 200 000 ultraviolet (UV)-selected (NUV < 22.8 mag) galaxies on the Anglo-Australian Telescope. The survey detected the baryon acoustic oscillation signal in the large-scale distribution of galaxies over the redshift range 0.2 < z < 1.0, confirming the acceleration of the expansion of the Universe and measuring the rate of structure growth within it. Here, we present the final data release of the survey: a catalogue of 225 415 galaxies and individual files of the galaxy spectra. We analyse the emission-line properties of these UV-luminous Lyman-break galaxies by stacking the spectra in bins of luminosity, redshift, and stellar mass. The most luminous (-25 magFUV<-22 mag) galaxies have very broad Hβ emission from active nuclei, as well as a broad second component to the [O III] (495.9 nm, 500.7 nm) doublet lines that is blueshifted by 100 km s-1 , indicating the presence of gas outflows in these galaxies. The composite spectra allow us to detect and measure the temperature-sensitive [O III] (436.3 nm) line and obtain metallicities using the direct method. The metallicities of intermediate stellar mass (8.8 < log (M*/M⊙) < 10) WiggleZ galaxies are consistent with normal emission-line galaxies at the same masses. In contrast, the metallicities of high stellar mass (10 < log (M*/M⊙) < 12) WiggleZ galaxies are significantly lower than for normal emission-line galaxies at the same masses. This is not an effect of evolution as the metallicities do not vary with redshift; it is most likely a property specific to the extremely UV-luminous WiggleZ galaxies.

Why soft UV-A damages DNA: An optical micromanipulation study

NASA Astrophysics Data System (ADS)

Rapp, A.; Greulich, K. O.

2013-09-01

Optical micromanipulation studies have solved a puzzle on DNA damage and repair. Such knowledge is crucial for understanding cancer and ageing. So far it was not understood, why the soft UV component of sunlight, UV-A, causes the dangerous DNA double strand breaks. The energy of UV-A photons is below 4 eV per photon, too low to directly cleave the corresponding chemical bonds in DNA. This is occasionally used to claim that artificial sunbeds, which mainly use UV-A, would not impose a risk on health. UV-A is only sufficient for induction of single strand breaks. The essential new observation is that, when on the opposite strand there is another single strand break at a distance of up to 20 base pairs. These two breaks will be converted into a break of the whole double strand with all its known consequences for cancer and ageing. However, in natural sun the effect is counteracted. Simultaneous red light illumination reduces UV induced DNA damages to 1/3. Since sunlight has a red component, skin tanning with natural sun is not as risky as might appear at a first glance.

Hubble Space Telescope far-ultraviolet imaging of the jet in 3C273: a common emission component from optical to X-rays

NASA Astrophysics Data System (ADS)

Jester, Sebastian; Meisenheimer, Klaus; Martel, André R.; Perlman, Eric S.; Sparks, William B.

2007-09-01

We present far-ultraviolet (far-UV) observations at ~150 nm of the jet of quasar 3C273 obtained with the Advanced Camera for Surveys (ACS) Solar Blind Channel onboard the Hubble Space Telescope. While the jet morphology is very similar to that in the optical and near-UV, the spectral energy distributions of the jet's subregions show an upturn in νfν at 150nm compared to 300nm everywhere in the jet. Moreover, the 150-nm flux is compatible with extrapolating the X-ray power law down to the UV region. This constitutes strong support for a common origin of the jet's far-UV and X-ray emission. It implies that even a substantial fraction of the visible light in the X-ray brightest parts of the jet arises from the same spectral component as the X-rays, as had been suggested earlier based on Spitzer Space Telescope observations. We argue that the identification of this UV/X-ray component opens up the possibility to establish the synchrotron origin of the X-ray emission by optical polarimetry. Based on observations made with the NASA/ESA Hubble Space Telescope (HST), obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. These observations are associated with HST programme GO-9814. This work was begun at the Particle Astrophysics Center, Fermilab, Batavia, IL 60510, USA. ‡ E-mail: jester@mpia.de

Juno-UVS and Chandra Observations of Jupiter's Polar Auroral Emissions

NASA Astrophysics Data System (ADS)

Gladstone, G. R.; Kammer, J. A.; Versteeg, M. H.; Greathouse, T. K.; Hue, V.; Gérard, J.-C.; Grodent, D.; Bonfond, B.; Jackman, C.; Branduardi-Raymont, G.; Kraft, R. P.; Dunn, W. R.; Bolton, S. J.; Connerney, J. E. P.; Levin, S. M.; Mauk, B. H.; Valek, P.; Adriani, A.; Kurth, W. S.; Orton, G. S.

2017-09-01

New results are presented comparing Jupiter's auroras at far-ultraviolet and x-ray wavelengths, using data acquired by Juno-UVS and Chandra. The highly variable polar auroras (which are located within the main auroral oval) track each other quite well in brightness at these two wavelengths.

M dwarf energetic proton flux on exoplanets during flares: estimates using solar UV-proton relations

NASA Astrophysics Data System (ADS)

Youngblood, Allison, France; Kevin; Mason, James P.

2016-10-01

UV and X-ray stellar radiation impacts planetary atmospheres through heating and photochemistry, even regulating production of potential biomarkers. The surface conditions on M dwarf planets are not greatly affected by flares in the emission line-dominated far-UV spectra of M dwarfs (M < 0.5 Msun), however, theoretical investigations have largely ignored the additional influence of stellar energetic particles (SEPs) released during flares. Magnetospheric compression and atmospheric stripping by SEPs could allow life-damaging (or catalyzing) radiation to reach the planetary surface and cause atmospheric heating closer to the surface. For the sun, a relationship between >10 MeV proton flux and 1-8 Å irradiance has been established with data from the GOES satellites (Belov et al. 2005), however, only a few X-ray observations of M-dwarf flares covering the complete 1-8 Å bandpass exist. Current M dwarf SEP estimates (Segura et al. 2010) employ the Neupert effect to first estimate the average X-ray flux over a broad band (1-62 Å) from the observed near- and far-UV flare flux (Mitra-Kraev et al. 2005). To improve the quality of proton flux estimates, we have analyzed the GOES >10 MeV observed proton flux and SDO EVE's solar spectral irradiance measurements to define relationships between SEPs and extreme-UV emission lines with formation temperatures similar to far-UV lines directly accessible by the Hubble Space Telescope (HST). Under the necessary assumption that an M dwarf's SEP production mechanism is similar to the sun's, we estimate SEP fluxes during M-dwarf flares observed with HST as part of the MUSCLES (Measurements of the Ultraviolet Spectral Characteristics of Low-mass Exoplanetary Systems) Treasury Survey.

Dissecting the IRX-β dust attenuation relation: exploring the physical origin of observed variations in galaxies

NASA Astrophysics Data System (ADS)

Popping, Gergö; Puglisi, Annagrazia; Norman, Colin A.

2017-12-01

The use of ultraviolet (UV) emission as a tracer of galaxy star formation rate (SFR) is hampered by dust obscuration. The empirical relationship between UV-slope, β, and the ratio between far-infrared and UV luminosity, IRX, is commonly employed to account for obscured UV emission. We present a simple model that explores the physical origin of variations in the IRX-β dust attenuation relation. A relative increase in FUV compared to NUV attenuation and an increasing stellar population age cause variations towards red UV-slopes for a fixed IRX. Dust geometry effects (turbulence, dust screen with holes, mixing of stars within the dust screen, two-component dust model) cause variations towards blue UV-slopes. Poor photometric sampling of the UV spectrum causes additional observational variations. We provide an analytic approximation for the IRX-β relation invoking a subset of the explored physical processes (dust type, stellar population age, turbulence). We discuss observed variations in the IRX-β relation for local (sub-galactic scales) and high-redshift (normal and dusty star-forming galaxies, galaxies during the epoch of reionization) galaxies in the context of the physical processes explored in our model. High spatial resolution imaging of the UV and sub-mm emission of galaxies can constrain the IRX-β dust attenuation relation for different galaxy types at different epochs, where different processes causing variations may dominate. These constraints will allow the use of the IRX-β relation to estimate intrinsic SFRs of galaxies, despite the lack of a universal relation.

Emission measures derived from far ultraviolet spectra of T Tauri stars

NASA Astrophysics Data System (ADS)

Cram, L. E.; Giampapa, M. S.; Imhoff, C. L.

1980-06-01

Spectroscopic diagnostics based on UV emission line observations have been developed to study the solar chromosphere, transition region, and corona. The atmospheric properties that can be inferred from observations of total line intensities include the temperature, by identifying the ionic species present; the temperature distribution of the emission measure, from the absolute intensities; and the electron density of the source, from line intensity ratios sensitive to the electron density. In the present paper, the temperature distribution of the emission measure is estimated from observations of far UV emission line fluxes of the T Tauri stars, RW Aurigae and RU Lupi, made on the IUE. A crude estimate of the electron density of one star is obtained, using density-sensitive line ratios.

Gas in Protoplanetary and Debris Disks: Insights from UV Spectroscopy

NASA Technical Reports Server (NTRS)

Roberge, Aki

2008-01-01

Over the last two decades, observations of protoplanetary and debris disks have played an important role in the new field of extrasolar planetary studies. Many are familiar with the extensive work on the cold circumstellar dust present in these disks done using infrared and sub-millimeter photometry and spectroscopy. However. UV spectroscopy has made some unique contributions by probing the elusive but vital gas component in protoplanetary and debris disks. In this talk, I will outline our picture of the evolution of protoplanetary disks and discuss the importance of the gas component. New insights obtained from UV spectroscopy will be highlighted, as well as some new puzzles. Finally, I will touch on upcoming studies of gas in protoplanetary and debris disks, some at UV wavelengths, some at far-IR and sub-mm wavelengths.

The Loopy Ultraviolet Line Profiles of RU Lupi: Accretion, Outflows, and Fluorescence

NASA Astrophysics Data System (ADS)

Herczeg, Gregory J.; Walter, Frederick M.; Linsky, Jeffrey L.; Gahm, Gösta F.; Ardila, David R.; Brown, Alexander; Johns-Krull, Christopher M.; Simon, Michal; Valenti, Jeff A.

2005-06-01

We present far-ultraviolet (FUV) spectra of the classical T Tauri star RU Lup covering the 912-1710 Å spectral range, as observed by the Hubble Space Telescope STIS and the Far Ultraviolet Spectroscopic Explorer satellite. We use these spectra, which are rich in emission and absorption lines, to probe both the accreting and outflowing gas. Absorption in the Lyα profile constrains the extinction to AV~0.07 mag, which we confirm with other diagnostics. We estimate a mass accretion rate of (5+/-2)×10-8 Msolar yr-1 using the optical-NUV accretion continuum. The accreting gas is also detected in bright, broad lines of C IV, Si IV, and N V, which all show complex structures across the line profile. Many other emission lines, including those of H2 and Fe II, are pumped by Lyα. RU Lup's spectrum varies significantly in the FUV; our STIS observations occurred when RU Lup was brighter than several other observations in the FUV, possibly because of a high mass accretion rate.

Understanding the scatter in the spatially resolved star formation main sequence of local massive spiral galaxies

NASA Astrophysics Data System (ADS)

Abdurro'uf; Akiyama, Masayuki

2017-08-01

We investigate the relation between star formation rate (SFR) and stellar mass (M*) at the sub-galactic scale (˜1 kpc) of 93 local (0.01 < z < 0.02) massive (M* > 1010.5 M⊙) spiral galaxies. To derive a spatially resolved SFR and stellar mass, we perform the so-called pixel-to-pixel spectral energy distribution (SED) fitting, which fits an observed spatially resolved multiband SED with a library of model SEDs using Bayesian statistics. We use two bands (far-ultraviolet or FUV and near-ultraviolet or NUV) and five bands (u, g, r, I and z) of imaging data from Galaxy Evolution Explorer (GALEX) and Sloan Digital Sky Survey (SDSS), respectively. We find a tight nearly linear relation between the local surface density of SFR (ΣSFR) and stellar mass (Σ*), which is flattened at high Σ*. The near linear relation between Σ* and ΣSFR suggests a constant specific SFR (sSFR) throughout the galaxies, and the scatter of the relation is directly related to that of the sSFR. Therefore, we analyse the variation of the sSFR in various scales. More massive galaxies on average have lower sSFR throughout them than less massive galaxies. We also find that barred galaxies have a lower sSFR in the core region than non-barred galaxies. However, in the outer region, the sSFRs of barred and non-barred galaxies are similar and lead to a similar total sSFR.

The star-formation law at GMC scales in M33, the Triangulum Galaxy

NASA Astrophysics Data System (ADS)

Williams, Thomas G.; Gear, Walter K.; Smith, Matthew W. L.

2018-06-01

We present a high spatial resolution study, on scales of ˜100pc, of the relationship between star-formation rate (SFR) and gas content within Local Group galaxy M33. Combining deep SCUBA-2 observations with archival GALEX, SDSS, WISE, Spitzer and submillimetre Herschel data, we are able to model the entire SED from UV to sub-mm wavelengths. We calculate the SFR on a pixel-by-pixel basis using the total infrared luminosity, and find a total SFR of 0.17 ± 0.06 {M}_⊙/yr, somewhat lower than our other two measures of SFR - combined FUV and 24μ SFR (0.25^{+0.10}_{-0.07} {M}_⊙/yr) and SED-fitting tool MAGPHYS (0.33^{+0.05}_{-0.06} {M}_⊙/yr). We trace the total gas using a combination of the 21cm HI line for atomic hydrogen, and CO(J=2-1) data for molecular hydrogen. We have also traced the total gas using dust masses. We study the star-formation law in terms of molecular gas, total gas, and gas from dust. We perform an analysis of the star-formation law on a variety of pixel scales, from 25" to 500" (100pc to 2kpc). At kpc scales, we find that a linear Schmidt-type power law index is suitable for molecular gas, but the index appears to be much higher with total gas, and gas from dust. Whilst we find a strong scale dependence on the Schmidt index, the gas depletion timescale is invariant with pixel scale.

The LUVOIR Ultraviolet Multi-Object Spectrograph (LUMOS): instrument definition and design

NASA Astrophysics Data System (ADS)

France, Kevin; Fleming, Brian; West, Garrett; McCandliss, Stephan R.; Bolcar, Matthew R.; Harris, Walter; Moustakas, Leonidas; O'Meara, John M.; Pascucci, Ilaria; Rigby, Jane; Schiminovich, David; Tumlinson, Jason

2017-08-01

The Large Ultraviolet/Optical/Infrared Surveyor (LUVOIR) is one of four large mission concepts currently undergoing community study for consideration by the 2020 Astronomy and Astrophysics Decadal Survey. LUVOIR is being designed to pursue an ambitious program of exoplanetary discovery and characterization, cosmic origins astrophysics, and planetary science. The LUVOIR study team is investigating two large telescope apertures (9- and 15-meter primary mirror diameters) and a host of science instruments to carry out the primary mission goals. Many of the exoplanet, cosmic origins, and planetary science goals of LUVOIR require high-throughput, imaging spectroscopy at ultraviolet (100 - 400 nm) wavelengths. The LUVOIR Ultraviolet Multi-Object Spectrograph, LUMOS, is being designed to support all of the UV science requirements of LUVOIR, from exoplanet host star characterization to tomography of circumgalactic halos to water plumes on outer solar system satellites. LUMOS offers point source and multi-object spectroscopy across the UV bandpass, with multiple resolution modes to support different science goals. The instrument will provide low (R = 8,000 - 18,000) and medium (R = 30,000 - 65,000) resolution modes across the far-ultraviolet (FUV: 100 - 200 nm) and nearultraviolet (NUV: 200 - 400 nm) windows, and a very low resolution mode (R = 500) for spectroscopic investigations of extremely faint objects in the FUV. Imaging spectroscopy will be accomplished over a 3 × 1.6 arcminute field-of-view by employing holographically-ruled diffraction gratings to control optical aberrations, microshutter arrays (MSA) built on the heritage of the Near Infrared Spectrograph (NIRSpec) on the James Webb Space Telescope (JWST), advanced optical coatings for high-throughput in the FUV, and next generation large-format photon-counting detectors. The spectroscopic capabilities of LUMOS are augmented by an FUV imaging channel (100 - 200nm, 13 milliarcsecond angular resolution, 2 × 2

Degradation and mineralization of Bisphenol A (BPA) in aqueous solution using advanced oxidation processes: UV/H2O2 and UV/S2O8(2-) oxidation systems.

PubMed

Sharma, Jyoti; Mishra, I M; Kumar, Vineet

2015-06-01

This work reports on the removal and mineralization of an endocrine disrupting chemical, Bisphenol A (BPA) at a concentration of 0.22 mM in aqueous solution using inorganic oxidants (hydrogen peroxide, H2O2 and sodium persulfate, Na2S2O8;S2O8(2-)) under UV irradiation at a wavelength of 254 nm and 40 W power (Io = 1.26 × 10(-6) E s(-1)) at its natural pH and a temperature of 29 ± 3 °C. With an optimum persulfate concentration of 1.26 mM, the UV/S2O8(2-) process resulted in ∼95% BPA removal after 240 min of irradiation. The optimum BPA removal was found to be ∼85% with a H2O2 concentration of 11.76 mM. At higher concentrations, either of the oxidants showed an adverse effect because of the quenching of the hydroxyl or sulfate radicals in the BPA solution. The sulfate-based oxidation process could be used over a wider initial pH range of 3-12, but the hydroxyl radical-based oxidation of BPA should be carried out in the acidic pH range only. The water matrix components (bicarbonate, chloride and humic acid) showed higher scavenging effect in hydroxyl radical-based oxidation than that in the sulfate radical-based oxidation of BPA. UV/S2O8(2-) oxidation system utilized less energy (307 kWh/m(3)) EE/O in comparison to UV/H2O2 system (509 kWh/m(3)) under optimum operating conditions. The cost of UV irradiation far outweighed the cost of the oxidants in the process. However, the total cost of treatment of persulfate-based system was much lower than that of H2O2-based oxidation system. Copyright © 2015 Elsevier Ltd. All rights reserved.

Advanced Environmentally Resistant Lithium Fluoride Mirror Coatings for the Next Generation of Broadband Space Observatories

NASA Technical Reports Server (NTRS)

Fleming, Brian; Quijada, Manuel A.; Hennessy, John; Egan, Arika; Del Hoyo, Javier G.

2017-01-01

Recent advances in the physical vapor deposition (PVD) of protective fluoride films have raised the far-ultraviolet (FUV: 912-1600 A) reflectivity of aluminum-based mirrors closer to the theoretical limit. The greatest gains, at more than 20%, have come for lithium fluoride-protected aluminum, which has the shortest wavelength cutoff of any conventional overcoat. Despite the success of the NASA FUSE mission, the use of lithium fluoride (LiF)-based optics is rare, as LiF is hygroscopic and requires handling procedures that can drive risk. With NASA now studying two large mission concepts for astronomy, Large UV-Optical-IR Surveyor (LUVOIR) and the Habitable Exoplanet Imaging Mission (HabEx), which mandate throughput down to 1000 , the development of LiF-based coatings becomes crucial. This paper discusses steps that are being taken to qualify these new enhanced LiF-protected aluminum (eLiF) mirror coatings for flight. In addition to quantifying the hygroscopic degradation, we have developed a new method of protecting eLiF with an ultrathin (10-20 A) capping layer of a nonhygroscopic material to increase durability. We report on the performance of eLiF-based optics and assess the steps that need to be taken to qualify such coatings for LUVOIR, HabEx, and other FUV-sensitive space missions.

Ultraviolet aurorae and dayglow in the upper atmospheres of terrestrial planets

NASA Astrophysics Data System (ADS)

Gerard, Jean-Claude; Hubert, Benoit; Gustin, J.; Cox, Cedric

Since its discovery in 2005 with the SPICAM spectrograph on board Mars Express, the Mars aurora has been further investigated. It is caused by sporadic soft electron precipitation whose signature is clearly observed in the FUV nightglow spectrum. The characteristics of the auroral electrons have been documented with parallel observations. Dayglow UV spectra have been collected with SPICAM over several seasons. The dependence of the intensity and peak altitude of the CO Cameron bands and CO2 + doublet emissions on latitude, local time and solar activity level have been investigated and compared with the results of a FUV Mars dayglow model. Far and Extreme ultraviolet spectra have been collected with the UVIS instrument during the flyby of Venus by Cassini, in a period a high solar activity. Their analysis shows the presence of OI, OII, NI, CI, CO and CO2 + emissions, some of them not previously identified in the Venus spectrum. The intensities will be compared with those observed with the HUT spectrograph during a period of low solar activity. The excitation processes of the observed features will be discussed. Scans of the intensity variation of several EUV bright emissions such as OII 83.4 nm, OI 98.9 nm and NI 120.0 nm multiplets across the sunlit disc will be compared with the calculations of a Venus dayglow model, including multiple scattering of optically thick transitions.

Multi-wavelength Morphological Study Of Star Forming Regions In Nearby Cluster-rich Lirgs

NASA Astrophysics Data System (ADS)

Vavilkin, Tatjana; Evans, A.; Mazzarella, J.; Surace, J.; Kim, D.; Howell, J.; Armus, L.; GOALS Team

2009-05-01

Luminous Infrared Galaxies (LIRGs) are believed to play an important role in star formation history of the universe. Many LIRGs undergo intense bursts of star formation as a result of interaction/merger process. Given the dusty nature of LIRGs, it is necessary to probe Luminous Infrared Galaxies at multiple wavelengths. The Great Observatories All-sky LIRG Survey (GOALS) combines data from NASA's Spitzer, Hubble, Chandra and GALEX observatories and offers a unique opportunity to gain insights into the physical processes in these highly dust enshrouded systems. We examine a sample of 11 nearby (z < 0.03) cluster-rich (> 200 clusters as seen in HST ACS images) LIRG systems at various interaction stages. The combined HST ACS optical imaging, Spitzer IRAC 8 micron channel and GALEX near-UV imaging allows us to access the properties of visible and obscured star forming regions. We study the spatial distribution of star forming regions at these wavelengths, correlate locations of young stellar clusters with PAH and UV emission regions and trace changes with merger stage.

CUVE - Cubesat UV Experiment: Unveil Venus' UV Absorber with Cubesat UV Mapping Spectrometer

NASA Astrophysics Data System (ADS)

Cottini, V.; Aslam, S.; D'Aversa, E.; Glaze, L.; Gorius, N.; Hewagama, T.; Ignatiev, N.; Piccioni, G.

2017-09-01

Our Venus mission concept Cubesat UV Experiment (CUVE) is one of ten proposals selected for funding by the NASA PSDS3 Program - Planetary Science Deep Space SmallSat Studies. CUVE concept is to insert a CubeSat spacecraft into a Venusian orbit and perform remote sensing of the UV spectral region using a high spectral resolution point spectrometer to resolve UV molecular bands, observe nightglow, and characterize the unidentified main UV absorber. The UV spectrometer is complemented by an imaging UV camera with multiple bands in the UV absorber main band range for contextual imaging. CUVE Science Objectives are: the nature of the "Unknown" UV-absorber; the abundances and distributions of SO2 and SO at and above Venus's cloud tops and their correlation with the UV absorber; the atmospheric dynamics at the cloud tops, structure of upper clouds and wind measurements from cloud-tracking; the nightglow emissions: NO, CO, O2. This mission will therefore be an excellent platform to study Venus' cloud top atmospheric properties where the UV absorption drives the planet's energy balance. CUVE would complement past, current and future Venus missions with conventional spacecraft, and address critical science questions cost effectively.

Light-Regulated Polymerization under Near-Infrared/Far-Red Irradiation Catalyzed by Bacteriochlorophyll a.

PubMed

Shanmugam, Sivaprakash; Xu, Jiangtao; Boyer, Cyrille

2016-01-18

Photoregulated polymerizations are typically conducted using high-energy (UV and blue) light, which may lead to undesired side reactions. Furthermore, as the penetration of visible light is rather limited, the range of applications with such wavelengths is likewise limited. We herein report the first living radical polymerization that can be activated and deactivated by irradiation with near-infrared (NIR) and far-red light. Bacteriochlorophyll a (Bachl a) was employed as a photoredox catalyst for photoinduced electron transfer/reversible addition-fragmentation chain transfer (PET-RAFT) polymerization. Well-defined polymers were thus synthesized within a few hours under NIR (λ=850 nm) and far-red (λ=780 nm) irradiation with excellent control over the molecular weight (M(n)/M(w)<1.25). Taking advantage of the good penetration of NIR light, we showed that the polymerization also proceeded smoothly when a translucent barrier was placed between light source and reaction vessel. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Star Formation in NGC 4631

NASA Astrophysics Data System (ADS)

Smith, A. M.; Collins, N. R.; Bohlin, R.; Fanelli, M. N.; Neff, S. G.; O'Connell, R. W.; Roberts, M. S.; Stecher, T. P.; Waller, W. H.

1997-12-01

The group of galaxies including NGC 4631 provides an outstanding example of a galaxy interaction accompanied by intensive star formation. FUV imagery, recorded by the Ultraviolet Imaging Telescope (UIT), exhibits very bright far- ultraviolet (FUV) emission corresponding to the H II regions cataloged by Crillon and Monet (1969). This data is, in our experience, extraordinary in that NCG 4631 is observed nearly edge-on and strong attenuation of FUV light could be anticipated. Analysis of the ultraviolet imagery together with ground-based data leads to the following conclusions. The average extinction internal to the bright FUV regions is low [E(B--V) = 0.31], which combined with the optical morphology implies that the FUV bright regions are close to the edge of the galactic disk. The FUV luminosity of that part of the galaxy which can be observed is 8.2 x 10(40) ergs/s and is about a factor 6 less than the FUV luminosities of M101 and M83. FUV colors, M152-U, M152-B and M152-V, when compared to the predicted colors from cluster formation models utilizing a Salpeter IMF imply an internal extinction like that of a non-30Dor LMC extinction curve (Fitzpatrick 1985). Instantaneous burst models indicate an average age of the FUV bright regions of about 6 Myr and a total created stellar mass of 2.8 x 10(7) Msun . If the measured colors are compared to continuous star formation models, star formation beginning about 100 Myr in the past and continuing to the present with a total star formation rate in the FUV bright regions of 0.026 Msun /yr is implied. The total number of OB stars in the H II regions comprising the large ring in the eastern part of the galaxy (Rand's Shell #1, 1993) is inferred to be 20,000. This number can be compared to Rand's estimate of 10,000 to 35,000 supernova-producing OB stars which are required to impart momentum to an expanding shell of hydrogen gas.

High-resolution ultraviolet radiation fields of classical T Tauri stars

DOE Office of Scientific and Technical Information (OSTI.GOV)

France, Kevin; Schindhelm, Eric; Bergin, Edwin A.

2014-04-01

The far-ultraviolet (FUV; 912-1700 Å) radiation field from accreting central stars in classical T Tauri systems influences the disk chemistry during the period of giant planet formation. The FUV field may also play a critical role in determining the evolution of the inner disk (r < 10 AU), from a gas- and dust-rich primordial disk to a transitional system where the optically thick warm dust distribution has been depleted. Previous efforts to measure the true stellar+accretion-generated FUV luminosity (both hot gas emission lines and continua) have been complicated by a combination of low-sensitivity and/or low-spectral resolution and did not includemore » the contribution from the bright Lyα emission line. In this work, we present a high-resolution spectroscopic study of the FUV radiation fields of 16 T Tauri stars whose dust disks display a range of evolutionary states. We include reconstructed Lyα line profiles and remove atomic and molecular disk emission (from H{sub 2} and CO fluorescence) to provide robust measurements of both the FUV continuum and hot gas lines (e.g., Lyα, N V, C IV, He II) for an appreciable sample of T Tauri stars for the first time. We find that the flux of the typical classical T Tauri star FUV radiation field at 1 AU from the central star is ∼10{sup 7} times the average interstellar radiation field. The Lyα emission line contributes an average of 88% of the total FUV flux, with the FUV continuum accounting for an average of 8%. Both the FUV continuum and Lyα flux are strongly correlated with C IV flux, suggesting that accretion processes dominate the production of both of these components. On average, only ∼0.5% of the total FUV flux is emitted between the Lyman limit (912 Å) and the H{sub 2} (0-0) absorption band at 1110 Å. The total and component-level high-resolution radiation fields are made publicly available in machine-readable format.« less

The UV Imager and its Role in the SMILE Mission

NASA Astrophysics Data System (ADS)

Donovan, E.; Escoubet, C. P.; Branduardi-Raymont, G.; Wang, C.; Hubert, B. A.; Spanswick, E.; Wang, Y.; Raab, W.; Sibeck, D. G.; Sembay, S.; Read, A.; Wielders, A.; Dimmock, A. P.; Romstedt, J.; Loicq, J.

2017-12-01

The upcoming SMILE (Solar wind Magnetosphere Ionosphere Link Explorer) mission promises to revolutionize our understanding of the global geospace and space weather consequences of the Solar Wind Magnetosphere interaction. SMILE will carry four instruments: two in situ instruments which will specify the magnetic field and energetic particles at the spacecraft, an X-ray imager for imaging the magnetopause and cusps, and a UV imager for observing the global (northern hemisphere) auroral oval. The high apogee, which is necessary for obtaining the in situ measurements, presents challenges for the UV imager, but will also support by far the longest duration continuous imaging of the global aurora. As well, inbound and outbound from perigee (for up to 8 hours during each orbit), the UV imager will be able to provide images that will compete with THEMIS-ASI in terms of resolution across an area larger than Canada. In this presentation, we will give an overview of SMILE and its objectives, and an in depth discussion of the UV imager and the role its data will play in the mission science.

Lifetime testing UV LEDs for use in the LISA charge management system

NASA Astrophysics Data System (ADS)

Hollington, D.; Baird, J. T.; Sumner, T. J.; Wass, P. J.

2017-10-01

As a future charge management light source, UV light-emitting diodes (UV LEDs) offer far superior performance in a range of metrics compared to the mercury lamps used in the past. As part of a qualification program a number of short wavelength UV LEDs have been subjected to a series of lifetime tests for potential use on the laser interferometer space antenna (LISA) mission. These tests were performed at realistic output levels for both fast and continuous discharging in either a DC or pulsed mode of operation and included a DC fast discharge test spanning 50 days, a temperature dependent pulsed fast discharge test spanning 21 days and a pulsed continuous discharge test spanning 507 days. Two types of UV LED have demonstrated lifetimes equivalent to over 25 years of realistic mission usage with one type providing a baseline for LISA and the other offering a backup solution.

Vacuum ultraviolet imagery of the Virgo Cluster region. II - Total far-ultraviolet flux of galaxies

NASA Astrophysics Data System (ADS)

Kodaira, K.; Watanabe, T.; Onaka, T.; Tanaka, W.

1990-11-01

The total flux in the far-ultraviolet region around 150 nm was measured for more than 40 galaxies in the central region of the Virgo Cluster, using two imaging telescopes on board a sounding rocket. The observed far-ultraviolet flux shows positive correlations with the H I 21 cm flux and the far-infrared flux for spiral galaxies, and with the X-ray flux and the radio continuum flux for elliptical galaxies. The former correlations of spiral galaxies are interpreted in terms of star formation activity, which indicates substantial depletion in the Virgo galaxies in accordance with the H I stripping. The latter correlations of elliptical galaxies indicate possible far-ultraviolet sources of young population, in addition to evolved hot stars. Far-ultraviolet fluxes from two dwarf elliptical galaxies were obtained tentatively, indicating star formation activity in elliptical galaxies. A high-resolution UV imagery by HST would be effective to distinguish the young population and the old population in elliptical galaxies.

Identification of cyanobacteriochromes detecting far-red light

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rockwell, Nathan C.; Martin, Shelley S.; Lagarias, J. Clark

The opacity of mammalian tissue to visible light and the strong attenuation of infrared light by water at ≥900 nm have contributed to growing interest in the development of far-red and near-infrared absorbing tools for visualizing and actuating responses within live cells. Here we report the discovery of cyanobacteriochromes (CBCRs) responsive to light in this far-red window. CBCRs are linear tetrapyrrole (bilin)-based light sensors distantly related to plant phytochrome sensors. Our studies reveal far-red (λ max = 725–755 nm)/orange (λ max = 590–600 nm) and far-red/red (λ max = 615–685 nm) photoswitches that are small (<200 amino acids) and canmore » be genetically reconstituted in living cells. Phylogenetic analysis and characterization of additional CBCRs demonstrated that far-red/orange CBCRs evolved after a complex transition from green/red CBCRs known for regulating complementary chromatic acclimation. Incorporation of different bilin chromophores demonstrated that tuning mechanisms responsible for red-shifted chromophore absorption act at the A-, B-, and/ or C-rings, whereas photoisomerization occurs at the D-ring. Two such proteins exhibited detectable fluorescence extending well into the near-infrared region. In conclusion, this work extends the spectral window of CBCRs to the edge of the infrared, raising the possibility of using CBCRs in synthetic biology applications in the far-red region of the spectrum.« less

Identification of cyanobacteriochromes detecting far-red light

DOE PAGES

Rockwell, Nathan C.; Martin, Shelley S.; Lagarias, J. Clark

2016-06-13

The opacity of mammalian tissue to visible light and the strong attenuation of infrared light by water at ≥900 nm have contributed to growing interest in the development of far-red and near-infrared absorbing tools for visualizing and actuating responses within live cells. Here we report the discovery of cyanobacteriochromes (CBCRs) responsive to light in this far-red window. CBCRs are linear tetrapyrrole (bilin)-based light sensors distantly related to plant phytochrome sensors. Our studies reveal far-red (λ max = 725–755 nm)/orange (λ max = 590–600 nm) and far-red/red (λ max = 615–685 nm) photoswitches that are small (<200 amino acids) and canmore » be genetically reconstituted in living cells. Phylogenetic analysis and characterization of additional CBCRs demonstrated that far-red/orange CBCRs evolved after a complex transition from green/red CBCRs known for regulating complementary chromatic acclimation. Incorporation of different bilin chromophores demonstrated that tuning mechanisms responsible for red-shifted chromophore absorption act at the A-, B-, and/ or C-rings, whereas photoisomerization occurs at the D-ring. Two such proteins exhibited detectable fluorescence extending well into the near-infrared region. In conclusion, this work extends the spectral window of CBCRs to the edge of the infrared, raising the possibility of using CBCRs in synthetic biology applications in the far-red region of the spectrum.« less

Cosmic Star Formation History and Evolution of the Galaxy UV Luminosity Function for z < 1

NASA Astrophysics Data System (ADS)

Zhang, Keming; Schiminovich, David

2018-01-01

We present the latest constraints on the evolution of the far-ultraviolet luminosity function of galaxies (1500 Å, UVLF hereafter) for 0 < z < 1 based on GALEX photometry, with redshift measurements from four spectroscopic and photometric-redshift catalogs: NSA, GAMA, VIPERS, and COSMOS photo-z. Our final sample consists of ~170000 galaxies, which represents the largest sample used in such studies. By integrating wide NSA and GAMA data and deep VIPERS and COSMOS photo-z data, we have been able to constrain both the bright end and the faint end of the luminosity function with high accuracy over the entire redshift range. We fit a Schechter function to our measurements of the UVLF, both to parameterize its evolution, and to integrate for SFR densities. From z~1 to z~0, the characteristic absolute magnitude of the UVLF increases linearly by ~1.5 magnitudes, while the faint end slope remains shallow (alpha < 1.5). However, the Schechter function fit exhibits an excess of galaxies at the bright end, which is accounted for by contributions from AGN. We also describe our methodology, which can be applied more generally to any combination of wide-shallow and deep-narrow surveys.

Variations in Canonical Star-Forming Laws at Low Metallicity

NASA Astrophysics Data System (ADS)

Monkiewicz, Jacqueline; Bowman, Judd D.; Scowen, Paul

2018-01-01

Empirically-determined star formation relations link observed galaxy luminosities to extrapolated star formation rates at almost every observable wavelength range. These laws are a cornerstone of extragalactic astronomy, and will be critically important for interpreting upcoming observations of early high-redshift protogalaxies with JWST and WFIRST. There are indications at a variety of wavelengths that these canonical relations may become unreliable at the lowest metallicities observed. This potentially complicates interpretation of the earliest protogalaxies, which are expected to be pristine and largely unenriched by stellar nucleosynthesis. Using a sample of 15 local dwarf galaxies with 12+[O/H] < 8.2, I focus on two of these relations: the far-infrared/radio relation and the H-alpha/ultraviolet relation. The sample is chosen to have pre-existing far-IR and UV observations, and to span the full spread of the galaxy mass-metallicity relationship at low luminosity, so that luminosity and metallicity may be examined separately. Radio continuum observations of low metallicity dwarf galaxies 1 Zw 18 and SBS 0335-052E suggest that the far-IR/radio relation probably deviates at low metallicities, but the low luminosity end of the relation is not well sampled. The upgraded Jansky Very Large Array has the sensitivity to fill in this gap. I have obtained 45 hours of L- and C-band continuum data of my dwarf galaxy sample. I present radio continuum imaging of an initial sub-sample of Local Group dwarfs, some of which have never before been detected in radio continuum. The H-alpha/UV relationship is likewise known to become unreliable for dwarf galaxies, though this has been attributed to dwarf galaxy "bursty-ness" rather than metallicity effects. I have conducted a parallel survey of emission line imaging to study the underlying astrophysics of the H-alpha/UV relation. Using Balmer decrement imaging, I map out the pixel-to-pixel dust distribution and geometry within the

A comparison of UV surface brightness and HI surface densities for spiral galaxies

NASA Technical Reports Server (NTRS)

Federman, S. R.; Strom, C.

1990-01-01

Shaya and Federman (1987) suggested that the ambient ultraviolet flux at 1000 A permeating a spiral galaxy controls the neutral hydrogen (HI) surface density in the galaxy. They found that the atomic envelopes surrounding small molecular clouds, because of their great number, provide the major contribution to the HI surface density over the stellar disk. The increase in HI surface density with later Hubble types was ascribed to the stronger UV fields from more high-mass stars in later Hubble types. These hypotheses are based on the observations of nearby diffuse interstellar clouds, which show a sharp atomic-to-molecular transition (Savage et al. 1977), and on the theoretical framework introduced by Federman, Glassgold, and Kwan (1979). Atomic envelopes around interstellar clouds in the solar neighborhood arise when a steady state is reached between photodissociation of H2 and the formation of H2 on grains. The photodissociation process involves photons with wavelengths between 912 A and 1108 A. Shaya and Federman used H-alpha flux as an approximate measure for the far UV flux and made their comparisons based on averages over Hubble type. Here, researchers compare, on an individual basis, UV data obtained with space-borne and balloon-borne instruments for galaxies with measurements of HI surface density (Warmels 1988a, b). The comparisons substantiate the conclusion of Shaya and Federman that the far UV field controls the HI content of spiral galaxies.

Extremely Luminous Far-infrared Sources (ELFS)

NASA Technical Reports Server (NTRS)

Harwit, Martin; Houck, James R.; Soifer, B. Thomas; Palumbo, Giorgio G. C.

1987-01-01

The Infrared Astronomical Satellite (IRAS) survey uncovered a class of Extremely Luminous Far Infrared Sources (ELFS), exhibiting luminosities up to and occasionally exceeding 10 to the 12th power L sub 0. Arguments are presented to show that sources with luminosities L equal to or greater than 3 x 10 to the 10th power L sub 0 may represent gas rich galaxies in collision. The more conventional explanation of these sources as sites of extremely active star formation fails to explain the observed low optical luminosities of ELFS as well as their high infrared excess. In contrast, a collisional model heats gas to a temperature of approx. 10 to the 6th power K where cooling takes place in the extreme ultraviolet. The UV is absorbed by dust and converted into far infrared radiation (FIR) without generation of appreciable optical luminosity. Gas recombination as it cools generates a Lyman alpha photon only once for every two extreme ultraviolet approx. 50eV photons emitted by the 10 to the 6th power gas. That accounts for the high infrared excess. Finally, the model also is able to explain the observed luminosity distribution of ELFS as well as many other traits.

GOODS Far Infrared Imaging with Herschel

NASA Astrophysics Data System (ADS)

Frayer, David T.; Elbaz, D.; Dickinson, M.; GOODS-Herschel Team

2010-01-01

Most of the stars in galaxies formed at high redshift in dusty environments, where their energy was absorbed and re-radiated at infrared wavelengths. Similarly, much of the growth of nuclear black holes in active galactic nuclei (AGN) was also obscured from direct view at UV/optical and X-ray wavelengths. The Great Observatories Origins Deep Survey Herschel (GOODS-H) open time key program will obtain the deepest far-infrared view of the distant universe, mapping the history of galaxy growth and AGN activity over a broad swath of cosmic time. GOODS-H will image the GOODS-North field with the PACS and SPIRE instruments at 100 to 500 microns, matching the deep survey of GOODS-South in the guaranteed time key program. GOODS-H will also observe an ultradeep sub-field within GOODS-South with PACS, reaching the deepest flux limits planned for Herschel (0.6 mJy at 100 microns with S/N=5). GOODS-H data will detect thousands of luminous and ultraluminous infrared galaxies out to z=4 or beyond, measuring their far-infrared luminosities and spectral energy distributions, and providing the best constraints on star formation rates and AGN activity during this key epoch of galaxy and black hole growth in the young universe.

Extreme ultraviolet (EUV) and FUV calibration facility for special sensor ultraviolet limb imager (SSULI)

NASA Astrophysics Data System (ADS)

Boyer, Craig N.; Osterman, Steven N.; Thonnard, Stefan E.; McCoy, Robert P.; Williams, J. Z.; Parker, S. E.

1994-09-01

A facility for calibrating far ultraviolet and extreme ultraviolet instruments has recently been completed at the Naval Research Laboratory. Our vacuum calibration vessel is 2-m in length, 1.67-m in diameter, and can accommodate optical test benches up to 1.2-m wide by 1.5-m in length. A kinematically positioned frame with four axis precision pointing capability of 10 microns for linear translation and .01 degrees for rotation is presently used during vacuum optical calibration of SSULI. The chamber was fabricated from 304 stainless steel and polished internally to reduce surface outgassing. A dust-free environment is maintained at the rear of the vacuum chamber by enclosing the 2-m hinged vacuum access door in an 8 ft. by 8 ft. class 100 clean room. Every effort was made to obtain an oil-free environment within the vacuum vessel. Outgassing products are continually monitored with a 1 - 200 amu residual gas analyzer. An oil-free claw and vane pump evacuates the chamber to 10-2 torr through 4 in. diameter stainless steel roughing lines. High vacuum is achieved and maintained with a magnetically levitated 480 l/s turbo pump and a 3000 l/s He4 cryopump. Either of two vacuum monochrometers, a 1-m f/10.4 or a 0.2-m f/4.5 are coaxially aligned with the optical axis of the chamber and are used to select single UV atomic resonance lines from a windowless capillary or penning discharge UV light source. A calibrated channeltron detector is coaxially mounted with the SSULI detector during calibration. All vacuum valves, the cooling system for the cryopump compressor, and the roughing pump are controlled through optical fibers which are interfaced to a computer through a VME board. Optical fibers were chosen to ensure that complete electrical isolation is maintained between the computer and the vacuum system valves-solenoids and relays.

A Model for Protostellar Cluster Luminosities and the Impact on the CO–H2 Conversion Factor

NASA Astrophysics Data System (ADS)

Gaches, Brandt A. L.; Offner, Stella S. R.

2018-02-01

We construct a semianalytic model to study the effect of far-ultraviolet (FUV) radiation on gas chemistry from embedded protostars. We use the protostellar luminosity function (PLF) formalism of Offner & McKee to calculate the total, FUV, and ionizing cluster luminosity for various protostellar accretion histories and cluster sizes. We2 compare the model predictions with surveys of Gould Belt star-forming regions and find that the tapered turbulent core model matches best the mean luminosities and the spread in the data. We combine the cluster model with the photodissociation region astrochemistry code, 3D-PDR, to compute the impact of the FUV luminosity from embedded protostars on the CO-to-H2 conversion factor, X CO, as a function of cluster size, gas mass, and star formation efficiency. We find that X CO has a weak dependence on the FUV radiation from embedded sources for large clusters owing to high cloud optical depths. In smaller and more efficient clusters the embedded FUV increases X CO to levels consistent with the average Milky Way values. The internal physical and chemical structures of the cloud are significantly altered, and X CO depends strongly on the protostellar cluster mass for small efficient clouds.

Galaxy And Mass Assembly (GAMA): the 0.013 < z < 0.1 cosmic spectral energy distribution from 0.1 μm to 1 mm

NASA Astrophysics Data System (ADS)

Driver, S. P.; Robotham, A. S. G.; Kelvin, L.; Alpaslan, M.; Baldry, I. K.; Bamford, S. P.; Brough, S.; Brown, M.; Hopkins, A. M.; Liske, J.; Loveday, J.; Norberg, P.; Peacock, J. A.; Andrae, E.; Bland-Hawthorn, J.; Bourne, N.; Cameron, E.; Colless, M.; Conselice, C. J.; Croom, S. M.; Dunne, L.; Frenk, C. S.; Graham, Alister W.; Gunawardhana, M.; Hill, D. T.; Jones, D. H.; Kuijken, K.; Madore, B.; Nichol, R. C.; Parkinson, H. R.; Pimbblet, K. A.; Phillipps, S.; Popescu, C. C.; Prescott, M.; Seibert, M.; Sharp, R. G.; Sutherland, W. J.; Taylor, E. N.; Thomas, D.; Tuffs, R. J.; van Kampen, E.; Wijesinghe, D.; Wilkins, S.

2012-12-01

We use the Galaxy And Mass Assembly survey (GAMA) I data set combined with GALEX, Sloan Digital Sky Survey (SDSS) and UKIRT Infrared Deep Sky Survey (UKIDSS) imaging to construct the low-redshift (z < 0.1) galaxy luminosity functions in FUV, NUV, ugriz and YJHK bands from within a single well-constrained volume of 3.4 × 105 (Mpc h-1)3. The derived luminosity distributions are normalized to the SDSS data release 7 (DR7) main survey to reduce the estimated cosmic variance to the 5 per cent level. The data are used to construct the cosmic spectral energy distribution (CSED) from 0.1 to 2.1 μm free from any wavelength-dependent cosmic variance for both the elliptical and non-elliptical populations. The two populations exhibit dramatically different CSEDs as expected for a predominantly old and young population, respectively. Using the Driver et al. prescription for the azimuthally averaged photon escape fraction, the non-ellipticals are corrected for the impact of dust attenuation and the combined CSED constructed. The final results show that the Universe is currently generating (1.8 ± 0.3) × 1035 h W Mpc-3 of which (1.2 ± 0.1) × 1035 h W Mpc-3 is directly released into the inter-galactic medium and (0.6 ± 0.1) × 1035 h W Mpc-3 is reprocessed and reradiated by dust in the far-IR. Using the GAMA data and our dust model we predict the mid- and far-IR emission which agrees remarkably well with available data. We therefore provide a robust description of the pre- and post-dust attenuated energy output of the nearby Universe from 0.1 μm to 0.6 mm. The largest uncertainty in this measurement lies in the mid- and far-IR bands stemming from the dust attenuation correction and its currently poorly constrained dependence on environment, stellar mass and morphology.

Thermal Pressure in Diffuse H2 Gas Measured by Herschel [C II] Emission and FUSE UV H2 Absorption

NASA Astrophysics Data System (ADS)

Velusamy, T.; Langer, W. D.; Goldsmith, P. F.; Pineda, J. L.

2017-04-01

UV absorption studies with the Far Ultraviolet Spectroscopic Explorer (FUSE) satellite have made important observations of H2 molecular gas in Galactic interstellar translucent and diffuse clouds. Observations of the 158 μm [C II] fine-structure line with Herschel trace the same H2 molecular gas in emission. We present [C II] observations along 27 lines of sight (LOSs) toward target stars of which 25 have FUSE H2 UV absorption. Two stars have only HST STIS C II λ2325 absorption data. We detect [C II] 158 μm emission features in all but one target LOS. For three target LOSs that are close to the Galactic plane, | {\\text{}}b| < 1°, we also present position-velocity maps of [C II] emission observed by Herschel Heterodyne Instrument in the Far Infrared (HIFI) in on-the-fly spectral-line mapping. We use the velocity-resolved [C II] spectra observed by the HIFI instrument toward the target LOSs observed by FUSE to identify [C II] velocity components associated with the H2 clouds. We analyze the observed velocity integrated [C II] spectral-line intensities in terms of the densities and thermal pressures in the H2 gas using the H2 column densities and temperatures measured by the UV absorption data. We present the H2 gas densities and thermal pressures for 26 target LOSs and from the [C II] intensities derive a mean thermal pressure in the range of ˜6100-7700 K cm-3 in diffuse H2 clouds. We discuss the thermal pressures and densities toward 14 targets, comparing them to results obtained using the UV absorption data for two other tracers C I and CO. Our results demonstrate the richness of the far-IR [C II] spectral data which is a valuable complement to the UV H2 absorption data for studying diffuse H2 molecular clouds. While the UV absorption is restricted to the directions of the target star, far-IR [C II] line emission offers an opportunity to employ velocity-resolved spectral-line mapping capability to study in detail the clouds’ spatial and velocity structures.

The Behavior of Warm Molecules in Planet-forming Disks and CHESS: a Pathfinder UV Spectrograph for the LUVOIR Surveyor

NASA Astrophysics Data System (ADS)

Hoadley, Keri; France, Kevin

2017-01-01

Understanding the evolution of gas over the lifetime of protoplanetary disks provides us with important clues about how planet formation mechanisms drive the diversity of exoplanetary systems observed to date. In the first part of my talk, I will discuss how we use emission line observations of molecular hydrogen (H2) in the far-ultraviolet (far-UV) with the Cosmic Origins Spectrograph (COS) on the Hubble Space Telescope to study the warm molecular regions (a < 10 AU) of planet-forming disks. We compare the observations with analytic disk models that produce synthetic H2 profiles, and we statistically determine the disk representations that best replicate the data. I will discuss the results of our comparisons and how the modeled radial distributions of H2 in the disk help provide important constraints on the effective density of gas left in the inner disk of protoplanetary disks at various disk evolutionary stages. Finally, I will talk about follow-up studies that look to connect the warm, UV-pumped molecular populations of the inner disk to thermally-excited molecules observed in similar regions of the disk in the near- to mid-IR.In the second part of my talk, I will discuss the observational requirements in the UV and IR band passes to gain further insights into the behavior of the warm, gaseous protoplanetary disk, focusing specifically on a spectrograph concept for the next-generation LUVOIR Surveyor. I will discuss a testbed instrument, the Colorado High-resolution Echelle Stellar Spectrograph (CHESS), built as a demonstration of one component of the LUVOIR spectrograph and new technological improvements to UV optical components for the next generation of near- to far-UV astrophysical observatories. CHESS is a far-UV sounding rocket experiment designed to probe the warm and cool atoms and molecules near sites of recent star formation in the local interstellar medium. I will talk about the science goals, design, research and development (R&D) components, and

A Comprehensive COS Study of the Magnetic Dynamos, Rotations, UV Irradiances and Habitability of dM Stars with a Broad Span of Ages

NASA Astrophysics Data System (ADS)

Guinan, Edward

2012-10-01

We propose HST/COS FUV spectrophotometry of a carefully selected sample of 9 dM1-5 stars with recently reliably determined ages ranging from 1-12 Gyr. This program complements our Chandra Cycle 13 program of the same targets to determine their coronal X-ray properties. Ages {of all but one star} have recently been firmly determined from memberships in wide binaries with white dwarf {WD} companions having reliable cooling time+main-sequence evolution ages {Zhao et al. 2012, Garces et al 2011}. Until these studies, reliable age determinations for dM stars >2 Gyr were nearly impossible. However, we can now carry out a comprehensive UV study of dM star atmospheres across nearly the full age-range of the current Universe. The primary goals are 1} to study the evolution of their dynamo-generated X-ray and UV {XUV} emissions with age/rotation and to better define the heating and energetics of their atmospheres {via Age-Rotation-Activity-XUV Irradiance relations} and 2} to study the effects of the XUV radiation on planets hosted by red dwarfs. The COS UV spectral region contains numerous important diagnostic emission lines for characterizing the energy transfer and atmospheric structure, while line ratios yield valuable information about the electron density. Further, these data {when combined with our coronal X-ray measures} are also important for gauging dM star XUV emissions - critical for assessing the photochemical & photoionization evolution of planetary atmospheres and ionospheres that in turn strongly affect the possible development of life on hosted extrasolar planets. We are requesting a total of 19 HST orbits to achieve the science goals of the program.

Past, present, and future of exoplanet research at UV wavelengths

NASA Astrophysics Data System (ADS)

Fossati, Luca

2016-07-01

The study of extra-solar planets (exoplanets) is arguably the most exciting and fastest-growing field in Astrophysics. We are only now beginning to see and understand the large variety of exoplanets, starting to classify them on the basis of their properties. Observations of transiting close-in planets at ultraviolet (UV) wavelengths revealed that such planets are subject to powerful mass-loss that shapes planetary structure, composition, and evolution. Thanks mostly to the Hubble Space Telescope, the past decade has seen great advances in the study of planet evaporation, but there are still many open questions and the the observations obtained so far were not able to provide enough constraints to the many models that have been developed in the meantime. I will review the past observations and advances in exoplanet science obtained on the basis of UV observations and discuss the prospects of further discoveries on the basis of the currently available and planned UV space telescopes.

Quantitative determination of ambroxol in tablets by derivative UV spectrophotometric method and HPLC.

PubMed

Dinçer, Zafer; Basan, Hasan; Göger, Nilgün Günden

2003-04-01

A derivative UV spectrophotometric method for the determination of ambroxol in tablets was developed. Determination of ambroxol in tablets was conducted by using first-order derivative UV spectrophotometric method at 255 nm (n = 5). Standards for the calibration graph ranging from 5.0 to 35.0 microg/ml were prepared from stock solution. The proposed method was accurate with 98.6+/-0.4% recovery value and precise with coefficient of variation (CV) of 1.22. These results were compared with those obtained by reference methods, zero-order UV spectrophotometric method and reversed-phase high-performance liquid chromatography (HPLC) method. A reversed-phase C(18) column with aqueous phosphate (0.01 M)-acetonitrile-glacial acetic acid (59:40:1, v/v/v) (pH 3.12) mobile phase was used and UV detector was set to 252 nm. Calibration solutions used in HPLC were ranging from 5.0 to 20.0 microg/ml. Results obtained by derivative UV spectrophotometric method was comparable to those obtained by reference methods, zero-order UV spectrophotometric method and HPLC, as far as ANOVA test, F(calculated) = 0.762 and F(theoretical) = 3.89, was concerned. Copyright 2003 Elsevier Science B.V.

UVIT view of ram-pressure stripping in action: Star formation in the stripped gas of the GASP jellyfish galaxy JO201 in Abell 85

NASA Astrophysics Data System (ADS)

George, K.; Poggianti, B. M.; Gullieuszik, M.; Fasano, G.; Bellhouse, C.; Postma, J.; Moretti, A.; Jaffé, Y.; Vulcani, B.; Bettoni, D.; Fritz, J.; Côté, P.; Ghosh, S. K.; Hutchings, J. B.; Mohan, R.; Sreekumar, P.; Stalin, C. S.; Subramaniam, A.; Tandon, S. N.

2018-06-01

Jellyfish are cluster galaxies that experience strong ram-pressure effects that strip their gas. Their Hα images reveal ionized gas tails up to 100 kpc, which could be hosting ongoing star formation. Here we report the ultraviolet (UV) imaging observation of the jellyfish galaxy JO201 obtained at a spatial resolution ˜ 1.3 kpc. The intense burst of star formation happening in the tentacles is the focus of the present study. JO201 is the "UV-brightest cluster galaxy" in Abell 85 (z ˜ 0.056) with knots and streams of star formation in the ultraviolet. We identify star forming knots both in the stripped gas and in the galaxy disk and compare the UV features with the ones traced by Hα emission. Overall, the two emissions remarkably correlate, both in the main body and along the tentacles. Similarly, also the star formation rates of individual knots derived from the extinction-corrected FUV emission agree with those derived from the Hα emission and range from ˜ 0.01 -to- 2.07 M⊙ yr-1. The integrated star formation rate from FUV flux is ˜ 15 M⊙ yr-1. The unprecedented deep UV imaging study of the jellyfish galaxy JO201 shows clear signs of extraplanar star-formation activity due to a recent/ongoing gas stripping event.

Far-UV photochemical bond cleavage of n-amyl nitrite: bypassing a repulsive surface.

PubMed

Minitti, Michael P; Zhang, Yao; Rosenberg, Martin; Brogaard, Rasmus Y; Deb, Sanghamitra; Sølling, Theis I; Weber, Peter M

2012-01-19

We have investigated the deep-UV photoinduced, homolytic bond cleavage of amyl nitrite to form NO and pentoxy radicals. One-color multiphoton ionization with ultrashort laser pulses through the S(2) state resonance gives rise to photoelectron spectra that reflect ionization from the S(1) state. Time-resolved pump-probe photoionization measurements show that upon excitation at 207 nm, the generation of NO in the v = 2 state is delayed, with a rise time of 283 (16) fs. The time-resolved mass spectrum shows the NO to be expelled with a kinetic energy of 1.0 eV, which is consistent with dissociation on the S(1) state potential energy surface. Combined, these observations show that the first step of the dissociation reaction involves an internal conversion from the S(2) to the S(1) state, which is followed by the ejection of the NO radical on the predissociative S(1) state potential energy surface.

Legacy ExtraGalactic UV Survey (LEGUS): The HST View of Star Formation in Nearby Galaxies

NASA Astrophysics Data System (ADS)

Calzetti, Daniela; Lee, J. C.; Adamo, A.; Aloisi, A.; Andrews, J. E.; Brown, T. M.; Chandar, R.; Christian, C. A.; Cignoni, M.; Clayton, G. C.; Da Silva, R. L.; de Mink, S. E.; Dobbs, C.; Elmegreen, B.; Elmegreen, D. M.; Evans, A. S.; Fumagalli, M.; Gallagher, J. S.; Gouliermis, D.; Grebel, E.; Herrero-Davo`, A.; Hilbert, B.; Hunter, D. A.; Johnson, K. E.; Kennicutt, R.; Kim, H.; Krumholz, M. R.; Lennon, D. J.; Martin, C. D.; Nair, P.; Nota, A.; Pellerin, A.; Prieto, J.; Regan, M. W.; Sabbi, E.; Schaerer, D.; Schiminovich, D.; Smith, L. J.; Thilker, D. A.; Tosi, M.; Van Dyk, S. D.; Walterbos, R. A.; Whitmore, B. C.; Wofford, A.

2014-01-01

The Treasury program LEGUS (HST/GO-13364) is the first HST UV Atlas of nearby galaxies, and is aimed at the thorough investigation of star formation and its relation with galaxy environment, from the scales of individual stars to those of ~kpc clustered structures. The 154-orbits program is obtaining NUV,U,B,V,I images of 50 star-forming galaxies in the distance range 4-12 Mpc, covering the full range of morphology, star formation rate (SFR), mass, metallicity, internal structure, and interaction state found in the local Universe. The imaging survey will yield accurate recent (<50 Myr) star formation histories (SFHs) from resolved massive stars, and the extinction-corrected ages and masses of star clusters and associations. These extensive inventories of massive stars, clustered systems, and SFHs will be used to: (1) quantify how the clustering of star formation evolves both in space and in time; (2) discriminate among models of star cluster evolution; (3) investigate the effects of SFH on the UV SFR calibrations; (4) explore the impact of environment on star formation and cluster evolution across the full range of galactic and ISM properties. LEGUS observations will inform theories of star formation and galaxy evolution, and improve the understanding of the physical underpinning of the gas-star formation relation and the nature of the clumpy star formation at high redshift. LEGUS will generate the most homogeneous high-resolution, wide-field UV dataset to date, building and expanding on the GALEX legacy. Data products that will be delivered to the community include: catalogs of massive stars and star clusters, catalogs of star cluster properties (ages, masses, extinction), and a one-stop shop for all the ancillary data available for this well-studied galaxy sample. LEGUS will provide the reference survey and the foundation for future observations with JWST and with ALMA. This abstract accompanies another one from the same project, and presents the status of the

The Northern Middle Lobe of Centaurus A: Circumgalactic Gas in a Starburst Wind

NASA Technical Reports Server (NTRS)

Neff, S. G.; Eilek, J. A.; Owen, F. N.; Schiminovich, D.; Seibert, M.; Thilker, D.

2012-01-01

We present deep ultraviolet (GALEX), radio continuum (VLA) and H-alpha (Magellan) images of the circumgalactic medium around Centaurus A (NGC5128). We focus on the Northern Middle Lobe (NML), a region extending more than 50kpc beyond the galaxy and known to host a collection of striking phenomena: emission line filaments, recent star formation, disrupted HI/molecular gas streams, and short-lived X-ray clouds. Far UV emission is tightly correlated with H-alpha emission for more than 50kpc, and loosely associated with a filament of X-ray clouds and with the radio continuum emission. The radio emission in the NML region does not appear to be an extension of the inner radio jet (10kpc) or a typical radio lobe. We speculate that the "weather" seen in the NML region is a short-lived phenomenon, caused by an outflow encountering cool gas deposited by one of the recent merger/encounter events which have characterized the history of NGC5128.

FTIR and Vis-FUV real time spectroscopic ellipsometry studies of polymer surface modifications during ion beam bombardment

NASA Astrophysics Data System (ADS)

Laskarakis, A.; Gravalidis, C.; Logothetidis, S.

2004-02-01

The continuously increasing application of polymeric materials in many scientific and technological fields has motivated an extensive use of polymer surface treatments, which modify the physical and chemical properties of polymer surfaces leading to surface activation and promotion of the surface adhesion. Fourier transform IR spectroscopic ellipsometry (FTIRSE) and phase modulated ellipsometry (PME) in the IR and Vis-FUV spectral regions respectively have been employed for in situ and real time monitoring of the structural changes on the polymer surface obtained by Ar + ion bombardment. The polymers were industrially supplied polyethylene terephthalate (PET) and polyethylene naphthalate (PEN) membranes. The Ar + ion bombardment has found to change the chemical bonding of the films and especially the amount of the CO, C-C and CC groups. The detailed study of the FTIRSE spectra reveals important information about the effect of the Ar + ion bombardment on each of the above bonding groups. Also, the modification of the characteristic features, attributed to electronic transitions in specific bonds of PET and PEN macromolecules, has been studied using PME.

Optical properties of graphene, silicene, germanene, and stanene from IR to far UV - A first principles study

NASA Astrophysics Data System (ADS)

John, Rita; Merlin, Benita

2017-11-01

This study offers an analysis of optical properties of Graphene and its 2D analogues: Silicene, Germanene, and Stanene with the help of band structures based on Density Functional Theory. The complex dielectric function and complex refractive index are calculated in both parallel (||) and perpendicular (⊥) polarization directions of the electromagnetic field. From these calculated values, optical observables like absorption, reflection, optical conductivity, and electron loss function have been studied. The optical response of all materials is shifted from ultraviolet (UV) to infrared (IR) from graphene to stanene; Graphene is more into UV region and other materials in the IR and visible regions. The intensity of absorption is maximum for stanene. The real part of dielectric function reveals the existence of plasma frequency in the || polarization direction indicating the metal to dielectric transition except for graphene. Study on refractive index clearly displays the birefringence characteristics of all materials. Reflectivity is enhanced in the mid IR and visible regions when light is polarized in the || direction. The in-depth investigations arrive at fine results which would enable the prediction of their potential applications in the optical and optoelectronic industries.

NGC 2782: A Merger Remnant with Young Stars in its Gaseous Tidal Tail

NASA Technical Reports Server (NTRS)

Torres-Flores, S.; de Oliveira, C. Mendes; de Mello, D. F.; Scarano, S. Jr.; Urrutia-Viscarra, R.

2012-01-01

We have searched for young star-forming regions around the merger remnant NGC 2782. By using GALEX FUV and NUV imaging and HI data we found seven UV sources, located at distances greater than 26 kpc from the center of NGG 2782, and coinciding with its western HI tidal tail. These regions were resolved in several smaller systems when Gemini/GMOS r-band images were used. We compared the observed colors to stellar population synthesis models and we found that these objects have ages of l to ll11yr and masses ranging from 10(exp 3.9) to l0(exp 4.6) Solar Mass. By using Gemini/GMOS spectroscopic data we confirm memberships and derive high metallicities for three of the young regions in the tail (12+log(O/H)=8.74+/-0.20, 8.81+/-0.20 and 8.78+/-0.20). These metallicities are similar to the value presented by the nuclear region of NGG 2782 and also similar to the value presented for an object located close to the main body of NGG 2782. The high metallicities measured for the star-forming regions in the gaseous tidal tail of NGG 2782 could be explained if they were formed out of highly enriched gas which was once expelled from the center of the merging galaxies when the system collided. An additional possibility is that the tail has been a nursery of a few generations of young stellar systems which ultimately polluted this medium with metals, further enriching the already pre-enriched gas ejected to the tail when the galaxies collided.

MULTIWAVELENGTH OBSERVATIONS OF A0620-00 IN QUIESCENCE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Froning, Cynthia S.; France, Kevin; Khargharia, Juthika

2011-12-10

We present contemporaneous X-ray, ultraviolet, optical, near-infrared, and radio observations of the black hole binary system, A0620-00, acquired in 2010 March. Using the Cosmic Origins Spectrograph on the Hubble Space Telescope, we have obtained the first FUV spectrum of A0620-00 as well as NUV observations with the Space Telescope Imaging Spectrograph. The observed spectrum is flat in the FUV and very faint (with continuum fluxes {approx_equal} 1e - 17 erg cm{sup -2} s{sup -1} A{sup -1}). The UV spectra also show strong, broad (FWHM {approx} 2000 km s{sup -1}) emission lines of Si IV, C IV, He II, Fe II,more » and Mg II. The C IV doublet is anomalously weak compared to the other lines, which is consistent with the low carbon abundance seen in NIR spectra of the source. Comparison of these observations with previous NUV spectra of A0620-00 shows that the UV flux has varied by factors of 2-8 over several years. We compiled the dereddened, broadband spectral energy distribution (SED) of A0620-00 and compared it to previous SEDs as well as theoretical models. The SEDs show that the source varies at all wavelengths for which we have multiple samples. Contrary to previous observations, the optical-UV spectrum does not continue to drop to shorter wavelengths, but instead shows a recovery and an increasingly blue spectrum in the FUV. We created an optical-UV spectrum of A0620-00 with the donor star contribution removed. The non-stellar spectrum peaks at {approx_equal}3000 A. The peak can be fit with a T = 10,000 K blackbody with a small emitting area, probably originating in the hot spot where the accretion stream impacts the outer disk. However, one or more components in addition to the blackbody are needed to fit the FUV upturn and the red optical fluxes in the optical-UV spectrum. By comparing the mass accretion rate determined from the hot spot luminosity to the mean accretion rate inferred from the outburst history, we find that the latter is an order of magnitude

Far-red light-mediated programmable anti-cancer gene delivery in cooperation with photodynamic therapy.

PubMed

Wang, Jinhui; He, Hua; Xu, Xin; Wang, Xiao; Chen, Yongbing; Yin, Lichen

2018-07-01

Effective anti-cancer therapy is hurdled by the complicated extracellular and intracellular barriers, and thus a smart gene vector that can enable programmable gene delivery is highly demanded. Photo-manipulation of gene delivery processes features spatial and temporal precision, while majority of current strategies utilizes short-wavelength UV/visible light with poor tissue penetration or high-power-density near-infrared (NIR) light that would cause undesired heat damage. Herein, an ROS-degradable polycation was designed and co-delivered with a photosensitizer (PS), thus realizing photo-programmable gene delivery using far-red light (661 nm) at low optical power density (down to 5 mW cm -2 ). Thioketal-crosslinked polyethylenimine (TK-PEI) was synthesized to condense p53 gene to form nanocomplexes (NCs), and hyaluronic acid (HA) modified with pheophytin a (Pha) was coated onto NCs to enhance their colloidal stability and enable cancer cell targeting. Short-time (8-min) light irradiation produced non-lethal amount of ROS to disrupt the endosomal membranes and facilitate p53 gene release via degradation of TK-PEI, which collectively enhanced p53 expression levels toward anti-cancer gene therapy. Long-time (30-min) light irradiation at the post-transfection state generated lethal amount of ROS, which cooperatively killed cancer cells to strengthen p53 gene therapy. To the best of our knowledge, this study represents the first example of an "one stone, three birds" approach to realize cooperative anti-cancer gene therapy using low-power-density, long-wavelength visible light as a single stimulus. Copyright © 2018 Elsevier Ltd. All rights reserved.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Thilker, David A.; Bianchi, Luciana; Schiminovich, David

We have discovered recent star formation in the outermost portion ((1-4) x R {sub 25}) of the nearby lenticular (S0) galaxy NGC 404 using Galaxy Evolution Explorer UV imaging. FUV-bright sources are strongly concentrated within the galaxy's H I ring (formed by a merger event according to del RIo et al.), even though the average gas density is dynamically subcritical. Archival Hubble Space Telescope imaging reveals resolved upper main-sequence stars and conclusively demonstrates that the UV light originates from recent star formation activity. We present FUV, NUV radial surface brightness profiles, and integrated magnitudes for NGC 404. Within the ring,more » the average star formation rate (SFR) surface density ({Sigma}{sub SFR}) is {approx}2.2 x 10{sup -5} M {sub sun} yr{sup -1} kpc{sup -2}. Of the total FUV flux, 70% comes from the H I ring which is forming stars at a rate of 2.5 x 10{sup -3} M {sub sun} yr{sup -1}. The gas consumption timescale, assuming a constant SFR and no gas recycling, is several times the age of the universe. In the context of the UV-optical galaxy color-magnitude diagram, the presence of the star-forming H I ring places NGC 404 in the green valley separating the red and blue sequences. The rejuvenated lenticular galaxy has experienced a merger-induced, disk-building excursion away from the red sequence toward bluer colors, where it may evolve quiescently or (if appropriately triggered) experience a burst capable of placing it on the blue/star-forming sequence for up to {approx}1 Gyr. The green valley galaxy population is heterogeneous, with most systems transitioning from blue to red but others evolving in the opposite sense due to acquisition of fresh gas through various channels.« less

Vesta's UV Lightcurve: Hemispheric Variation in Brightness and Spectral Reversal

NASA Technical Reports Server (NTRS)

Hendrix, Amanda R.; Vilas, Faith; Festou, Michael

2003-01-01

Spectra of asteroid 4 Vesta obtained in October 1990 with the International Ultraviolet Explorer are reanalyzed and reinterpreted. A large portion of the eastern hemisphere (based on the prime meridian definition of Thomas et al., 1997a) is darker at UV Wavelengths than much of the western hemisphere. The UV lightcurve is in contrast with the visible lightcurve, which shows that the eastern hemisphere is brighter than the western. These IUE spectra of Vesta thus may be evidence for the "spectral reversal." first seen on the Moon by Apollo 17. where the visibly brighter lunar highlands are darker than the maria at far-UV wavelengths. This effect was linked to space weathering when it was noted (Wagner et al., 1987) that the spectral reversal appears in the laboratory spectra of lunar soils but not powdered lunar rocks. We investigate Vesta's UV lightcurve and spectral reversal, and its possible connection with space weathering. The addition to grain coatings of small amounts of submicroscopic iron (SMFe) through vapor deposition causes drastic spectral changes at UV-visible wavelengths (Hapke, 2001). while the longer wavelength spectrum remains largely unaffected. Other laboratory results (e.g., Hiroi and Pieters, 1998) indicate that the UV-visible wavelength range is affected by simulated weathering processes in a manner similar to what is seen on Vesta. It is likely that Vesta has experienced relatively minor amounts of space weathering, as indicated by the spectral reversal, along with the subtle visible-near infrared weathering effects (e.g., Binzel et al., 1997).

Far-red light is needed for efficient photochemistry and photosynthesis.

PubMed

Zhen, Shuyang; van Iersel, Marc W

2017-02-01

The efficiency of monochromatic light to drive photosynthesis drops rapidly at wavelengths longer than 685nm. The photosynthetic efficiency of these longer wavelengths can be improved by adding shorter wavelength light, a phenomenon known as the Emerson enhancement effect. The reverse effect, the enhancement of photosynthesis under shorter wavelength light by longer wavelengths, however, has not been well studied and is often thought to be insignificant. We quantified the effect of adding far-red light (peak at 735nm) to red/blue or warm-white light on the photosynthetic efficiency of lettuce (Lactuca sativa). Adding far-red light immediately increased quantum yield of photosystem II (Φ PSII ) of lettuce by an average of 6.5 and 3.6% under red/blue and warm-white light, respectively. Similar or greater increases in Φ PSII were observed after 20min of exposure to far-red light. This longer-term effect of far-red light on Φ PSII was accompanied by a reduction in non-photochemical quenching of fluorescence (NPQ), indicating that far-red light reduced the dissipation of absorbed light as heat. The increase in Φ PSII and complementary decrease in NPQ is presumably due to preferential excitation of photosystem I (PSI) by far-red light, which leads to faster re-oxidization of the plastoquinone pool. This facilitates reopening of PSII reaction centers, enabling them to use absorbed photons more efficiently. The increase in Φ PSII by far-red light was associated with an increase in net photosynthesis (P n ). The stimulatory effect of far-red light increased asymptotically with increasing amounts of far-red. Overall, our results show that far-red light can increase the photosynthetic efficiency of shorter wavelength light that over-excites PSII. Copyright © 2016 Elsevier GmbH. All rights reserved.

Calibration of the Voyager Ultraviolet Spectrometers and the Composition of the Heliosphere Neutrals: Reassessment

NASA Astrophysics Data System (ADS)

Ben-Jaffel, Lotfi; Holberg, J. B.

2016-06-01

The data harvest from the Voyagers’ (V 1 and V 2) Ultraviolet Spectrometers (UVS) covers encounters with the outer planets, measurements of the heliosphere sky-background, and stellar spectrophotometry. Because their period of operation overlaps with many ultraviolet missions, the calibration of V1 and V2 UVS with other spectrometers is invaluable. Here we revisit the UVS calibration to assess the intriguing sensitivity enhancements of 243% (V1) and 156% (V2) proposed recently. Using the Lyα airglow from Saturn, observed in situ by both Voyagers, and remotely by International Ultraviolet Explorer (IUE), we match the Voyager values to IUE, taking into account the shape of the Saturn Lyα line observed with the Goddard High Resolution Spectrograph on board the Hubble Space Telescope. For all known ranges of the interplanetary hydrogen density, we show that the V1 and V2 UVS sensitivities cannot be enhanced by the amounts thus far proposed. The same diagnostic holds for distinct channels covering the diffuse He I 58.4 nm emission. Our prescription is to keep the original calibration of the Voyager UVS with a maximum uncertainty of 30%, making both instruments some of the most stable EUV/FUV spectrographs in the history of space exploration. In that frame, we reassess the excess Lyα emission detected by Voyager UVS deep in the heliosphere, to show its consistency with a heliospheric but not galactic origin. Our finding confirms results obtained nearly two decades ago—namely, the UVS discovery of the distortion of the heliosphere and the corresponding obliquity of the local interstellar magnetic field (˜ 40^\\circ from upwind) in the solar system neighborhood—without requiring any revision of the Voyager UVS calibration.

A UV-B-specific signaling component orchestrates plant UV protection

PubMed Central

Brown, Bobby A.; Cloix, Catherine; Jiang, Guang Huai; Kaiserli, Eirini; Herzyk, Pawel; Kliebenstein, Daniel J.; Jenkins, Gareth I.

2005-01-01

UV-B radiation in sunlight has diverse effects on humans, animals, plants, and microorganisms. UV-B can cause damage to molecules and cells, and consequently organisms need to protect against and repair UV damage to survive in sunlight. In plants, low nondamaging levels of UV-B stimulate transcription of genes involved in UV-protective responses. However, remarkably little is known about the underlying mechanisms of UV-B perception and signal transduction. Here we report that Arabidopsis UV RESISTANCE LOCUS 8 (UVR8) is a UV-B-specific signaling component that orchestrates expression of a range of genes with vital UV-protective functions. Moreover, we show that UVR8 regulates expression of the transcription factor HY5 specifically when the plant is exposed to UV-B. We demonstrate that HY5 is a key effector of the UVR8 pathway, and that it is required for survival under UV-B radiation. UVR8 has sequence similarity to the eukaryotic guanine nucleotide exchange factor RCC1, but we found that it has little exchange activity. However, UVR8, like RCC1, is located principally in the nucleus and associates with chromatin via histones. Chromatin immunoprecipitation showed that UVR8 associates with chromatin in the HY5 promoter region, providing a mechanistic basis for its involvement in regulating transcription. We conclude that UVR8 defines a UV-B-specific signaling pathway in plants that orchestrates the protective gene expression responses to UV-B required for plant survival in sunlight. PMID:16330762

Molecular mechanisms and ecological function of far-red light signalling.

PubMed

Sheerin, David J; Hiltbrunner, Andreas

2017-11-01

Land plants possess the ability to sense and respond to far-red light (700-760 nm), which serves as an important environmental cue. Due to the nature of far-red light, it is not absorbed by chlorophyll and thus is enriched in canopy shade and will also penetrate deeper into soil than other visible wavelengths. Far-red light responses include regulation of seed germination, suppression of hypocotyl growth, induction of flowering and accumulation of anthocyanins, which depend on one member of the phytochrome photoreceptor family, phytochrome A (phyA). Here, we review the current understanding of the underlying molecular mechanisms of how plants sense far-red light through phyA and the physiological responses to this light quality. Light-activated phytochromes act on two primary pathways within the nucleus; suppression of the E3 ubiquitin ligase complex CUL4/DDB1 COP1/SPA and inactivation of the PHYTOCHROME INTERACTING FACTOR (PIF) family of bHLH transcription factors. These pathways integrate with other signal transduction pathways, including phytohormones, for tissue and developmental stage specific responses. Unlike other phytochromes that mediate red-light responses, phyA is transported from the cytoplasm to the nucleus in far-red light by the shuttle proteins FAR-RED ELONGATED HYPOCOTYL 1 (FHY1) and FHY1-LIKE (FHL). However, additional mechanisms must exist that shift the action of phyA to far-red light; current hypotheses are discussed. © 2017 John Wiley & Sons Ltd.

207-nm UV Light-A Promising Tool for Safe Low-Cost Reduction of Surgical Site Infections. II: In-Vivo Safety Studies.

PubMed

Buonanno, Manuela; Stanislauskas, Milda; Ponnaiya, Brian; Bigelow, Alan W; Randers-Pehrson, Gerhard; Xu, Yanping; Shuryak, Igor; Smilenov, Lubomir; Owens, David M; Brenner, David J

2016-01-01

UVC light generated by conventional germicidal lamps is a well-established anti-microbial modality, effective against both bacteria and viruses. However, it is a human health hazard, being both carcinogenic and cataractogenic. Earlier studies showed that single-wavelength far-UVC light (207 nm) generated by excimer lamps kills bacteria without apparent harm to human skin tissue in vitro. The biophysical explanation is that, due to its extremely short range in biological material, 207 nm UV light cannot penetrate the human stratum corneum (the outer dead-cell skin layer, thickness 5-20 μm) nor even the cytoplasm of individual human cells. By contrast, 207 nm UV light can penetrate bacteria and viruses because these cells are physically much smaller. To test the biophysically-based hypothesis that 207 nm UV light is not cytotoxic to exposed mammalian skin in vivo. Hairless mice were exposed to a bactericidal UV fluence of 157 mJ/cm2 delivered by a filtered Kr-Br excimer lamp producing monoenergetic 207-nm UV light, or delivered by a conventional 254-nm UV germicidal lamp. Sham irradiations constituted the negative control. Eight relevant cellular and molecular damage endpoints including epidermal hyperplasia, pre-mutagenic UV-associated DNA lesions, skin inflammation, and normal cell proliferation and differentiation were evaluated in mice dorsal skin harvested 48 h after UV exposure. While conventional germicidal UV (254 nm) exposure produced significant effects for all the studied skin damage endpoints, the same fluence of 207 nm UV light produced results that were not statistically distinguishable from the zero exposure controls. As predicted by biophysical considerations and in agreement with earlier in vitro studies, 207-nm light does not appear to be significantly cytotoxic to mouse skin. These results suggest that excimer-based far-UVC light could potentially be used for its anti-microbial properties, but without the associated hazards to skin of conventional

207-nm UV Light—A Promising Tool for Safe Low-Cost Reduction of Surgical Site Infections. II: In-Vivo Safety Studies

PubMed Central

Buonanno, Manuela; Stanislauskas, Milda; Ponnaiya, Brian; Bigelow, Alan W.; Randers-Pehrson, Gerhard; Xu, Yanping; Shuryak, Igor; Smilenov, Lubomir; Owens, David M.; Brenner, David J.

2016-01-01

Background UVC light generated by conventional germicidal lamps is a well-established anti-microbial modality, effective against both bacteria and viruses. However, it is a human health hazard, being both carcinogenic and cataractogenic. Earlier studies showed that single-wavelength far-UVC light (207 nm) generated by excimer lamps kills bacteria without apparent harm to human skin tissue in vitro. The biophysical explanation is that, due to its extremely short range in biological material, 207 nm UV light cannot penetrate the human stratum corneum (the outer dead-cell skin layer, thickness 5–20 μm) nor even the cytoplasm of individual human cells. By contrast, 207 nm UV light can penetrate bacteria and viruses because these cells are physically much smaller. Aims To test the biophysically-based hypothesis that 207 nm UV light is not cytotoxic to exposed mammalian skin in vivo. Methods Hairless mice were exposed to a bactericidal UV fluence of 157 mJ/cm2 delivered by a filtered Kr-Br excimer lamp producing monoenergetic 207-nm UV light, or delivered by a conventional 254-nm UV germicidal lamp. Sham irradiations constituted the negative control. Eight relevant cellular and molecular damage endpoints including epidermal hyperplasia, pre-mutagenic UV-associated DNA lesions, skin inflammation, and normal cell proliferation and differentiation were evaluated in mice dorsal skin harvested 48 h after UV exposure. Results While conventional germicidal UV (254 nm) exposure produced significant effects for all the studied skin damage endpoints, the same fluence of 207 nm UV light produced results that were not statistically distinguishable from the zero exposure controls. Conclusions As predicted by biophysical considerations and in agreement with earlier in vitro studies, 207-nm light does not appear to be significantly cytotoxic to mouse skin. These results suggest that excimer-based far-UVC light could potentially be used for its anti-microbial properties, but without

Photodegradation of 4-tert-butylphenol in aqueous solution by UV-C, UV/H2O2 and UV/S2O8(2-) system.

PubMed

Wu, Yanlin; Zhu, Xiufen; Chen, Hongche; Dong, Wenbo; Zhao, Jianfu

2016-01-01

The photolytic degradation of 4-tert-butylphenol (4-t-BP) in aqueous solution was investigated using three kinds of systems: UV-C directly photodegradation system, UV/H2O2 and UV/S2O8(2-) system. Under experimental conditions, the degradation rate of 4-t-BP was in the order: UV/S2O8(2-) > UV/H2O2 > UV-C. The reaction kinetics of UV/S2O8(2-) system were thoroughly investigated. The increase of S2O8(2-) concentration enhanced the 4-t-BP degradation rate, which was inhibited when the concentration of S2O8(2-) exceeded 4.0 mM. The highest efficacy in 4-t-BP degradation was obtained at pH 6.5. The oxidation rate of 4-t-BP could be accelerated by increasing the reaction temperature and irradiation intensity. The highest rate constant (kobs = 8.4 × 10(-2) min(-1)) was acquired when the reaction temperature was 45 °C. The irradiation intensity was measured by irradiation distance, and the optimum irradiation distance was 10 cm. Moreover, the preliminary mechanism of 4-t-BP degradation was studied. The bond scission of the 4-t-BP molecule occurred by the oxidation of SO4(•-), which dimerized and formed two main primary products. Under the conditions of room temperature (25 °C ± 1 °C) and low concentration of K2S2O8 (0.5 mM), 35.4% of total organic carbon (TOC) was removed after 8.5-h irradiation. The results showed that UV/S2O8(2-) system was effective for the degradation of 4-t-BP.

Durable silver mirror with ultra-violet thru far infra-red reflection

DOEpatents

Wolfe, Jesse D.

2010-11-23

A durable highly reflective silver mirror characterized by high reflectance in a broad spectral range of about 300 nm in the UV to the far infrared (.about.10000 nm), as well as exceptional environmental durability. A high absorptivity metal underlayer is used which prevents the formation of a galvanic cell with a silver layer while increasing the reflectance of the silver layer. Environmentally durable overcoat layers are provided to enhance mechanical and chemical durability and protect the silver layer from corrosion and tarnishing, for use in a wide variety of surroundings or climates, including harsh or extreme environments.

Spatial and directional control of self-assembled wrinkle patterns by UV light absorption

NASA Astrophysics Data System (ADS)

Kortz, C.; Oesterschulze, E.

2017-12-01

Wrinkle formation on surfaces is a phenomenon that is observed in layered systems with a compressed elastic thin capping layer residing on a viscoelastic film. So far, the properties of the viscoelastic material could only be changed replacing it by another material. Here, we propose to use a photosensitive material whose viscoelastic properties, Young's modulus, and glass transition temperature can easily be adjusted by the absorption of UV light. Employing UV lithography masks during the exposure, we gain additionally spatial and directional control of the self-assembled wrinkle pattern formation that relies on a spinodal decomposition process. Inspired by the results on surface wrinkling and its dependence on the intrinsic stress, we also derive a method to avoid wrinkling locally by tailoring the mechanical stress distribution in the layered system choosing UV masks with convex patterns. This is of particular interest in technical applications where the buckling of surfaces is undesirable.

Probing 67P/Churyumov-Gerasimenko's Electron Environment Through Ultraviolet Emission by Rosetta Alice Observations

NASA Astrophysics Data System (ADS)

Schindhelm, Eric; Noonan, John; Keeney, Brian A.; Broiles, Thomas; Bieler, Andre; A'Hearn, Michael F.; Bertaux, Jean-Loup; Feaga, Lori M.; Feldman, Paul D.; Parker, Joel Wm.; Steffl, Andrew Joseph; Stern, S. Alan; Weaver, Harold A.

2016-10-01

The Alice Far-Ultraviolet (FUV) Spectrograph onboard ESA's Rosetta spacecraft has observed the coma of comet 67P/Churyumov-Gerasimenko from far approach in summer 2014 until the end of mission in September 2016. We present an overall perspective of the bright FUV emission lines (HI 1026 Å, OI 1302/1305/1306 Å multiplet, OI] 1356 Å, CO 1510 (1-0) Å, and CI 1657 Å) above the sunward hemisphere, detailing their spatial extent and brightness as a function of time and the heliocentric distance of the comet. We compare our observed gas column densities derived using electron temperatures and densities from the Ion Electron Sensor (IES) with those derived using the Inner Coma Environment Simulator (ICES) models in periods when electron-impact excited emission dominates over solar fluorescence emission. The electron population is characterized with 2 three-dimensional kappa functions, one dense and warm, one rarefied and hot.

UV protection of euglenoids: computation of the electromagnetic response

NASA Astrophysics Data System (ADS)

Dolinko, Andrés.; Valencia, Claudio; Skigin, Diana C.; Inchaussandague, Marina E.; Tolivia, Analía.; Conforti, Visitación

2015-06-01

Euglenoids are a group of predominantly free-living unicellular microorganisms that mostly live in freshwater bodies but can also be found in marine and brackish waters. These organisms have a characteristic that distinguishes them form the other protists: they are covered by a surface pellicle formed by S-shaped overlapping bands which resemble a diffraction grating. These microorganisms have developed numerous protection mechanisms intended to avoid or reduce the damage produced by UV radiation, such as the production of pigments and the repair mechanisms in hours of darkness and during daylight. In a recent paper we have investigated the role played by the pellicle of Euglenoids in the protection of the cell against UV radiation, by means of an electromagnetic approach based on the approximation of the pellicle profile by a one-dimensional diffraction grating. This simplified model allowed us to confirm that under certain incidence conditions, the corrugation of the pellicle helps increase the UV reflection, and consequently, diminish the UV radiation that enters the cell. In order to analyze the electromagnetic response of the whole cell, we extend two different approaches to calculate the reflected response: a simulation method especially developed to deal with complex biological structures that permits the introduction of the scattering object via an electron microscopy image, and the integral method, which has been widely used to compute the electromagnetic response of finite structures. Numerical results of near and far fields are shown.

Prospects for the design of an ultraviolet imaging Fourier transform spectrometer

NASA Astrophysics Data System (ADS)

Lemaire, Philippe

2017-11-01

Recent results from solar observations in the far and extremeultraviolet (FUV/EUV) obtained from SOHO (SOlar and Heliospheric Observatory) and TRACE (Transition Region Camera) show the extreme variability of the solar atmosphere. Within the limited resolution of the instruments (1-2 arcseconds) horizontal and vertical velocities up-to 100 to 400 km s-1 have been measured. With an horizontal velocity of 100 km s-1 an one arsecond structure crosses the one arcsecond slit width of a classical slit spectrometer in less than 10 seconds. In the future, with higher angular resolution (e.g. 0.1 arcsecond), the capability to study small structures will be greatly reduced by a classical slit spectrometer. To be able to characterize the small scale solar atmospheric structures formed in the 104 K to 106 K temperature range (which emit in the 30 to 180 nm wavelength range) a spectrometer without slit (or with wide slit) is required. At the same time to obtain an accurate measurement of the doppler velocity an high spectral resolution is needed. The two requirements, high spectral resolution and large slit, are difficult to be simultaneously fulfilled with a classical slit spectrometer within the limited volume of a space instrumentation. Also, we propose to use an Imaging Fourier Transform Spectrometer (IFTS) to provide simultaneously a bidimensionnal field and an accurate determination of line profiles and positions. The development of Fourier Transform Spectrometers (FTS), although popular in the infrared, has been very limited in the UV/FUV by the lack of very high quality beam splitter. Since 10 years, the use of diffraction gratings as beam splitters has been suggested and few intruments have been built ([Chak 94]; [Clea 92]; [File 00]). These instruments illustrate some applications in the new wavelength domain opened by using a beam splitter grating, but do not yet provide the full capabilities of an FTS. In this paper we present several optical schemes which can

UV-B induction of the E3 ligase ARIADNE12 depends on CONSTITUTIVELY PHOTOMORPHOGENIC 1

PubMed Central

Xie, Lisi; Lang-Mladek, Christina; Richter, Julia; Nigam, Neha; Hauser, Marie-Theres

2015-01-01

The UV-B inducible ARIADNE12 (ARI12) gene of Arabidopsis thaliana is a member of the RING-between-RING (RBR) family of E3 ubiquitin ligases for which a novel ubiquitination mechanism was identified in mammalian homologs. This RING-HECT hybrid mechanism needs a conserved cysteine which is replaced by serine in ARI12 and might affect the E3 ubiquitin ligase activity. We have shown that under photomorphogenic UV-B, ARI12 is a downstream target of the classical ultraviolet B (UV-B) UV RESISTANCE LOCUS 8 (UVR8) pathway. However, under high fluence rate of UV-B ARI12 was induced independently of UVR8 and the UV-A/blue light and red/far-red photoreceptors. A key component of several light signaling pathways is CONSTITUTIVELY PHOTOMORPHOGENIC 1 (COP1). Upon UV-B COP1 is trapped in the nucleus through interaction with UVR8 permitting the activation of genes that regulate the biosynthesis of UV-B protective metabolites and growth adaptations. To clarify the role of COP1 in the regulation of ARI12 mRNA expression and ARI12 protein stability, localization and interaction with COP1 was assessed with and without UV-B. We found that COP1 controls ARI12 in white light, low and high fluence rate of UV-B. Furthermore we show that ARI12 is indeed an E3 ubiquitin ligase which is mono-ubiquitinated, a prerequisite for the RING-HECT hybrid mechanism. Finally, genetic analyses with transgenes expressing a genomic pmARI12:ARI12-GFP construct confirm the epistatic interaction between COP1 and ARI12 in growth responses to high fluence rate UV-B. PMID:25817546

In-orbit Calibrations of the Ultraviolet Imaging Telescope

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tandon, S. N.; Subramaniam, Annapurni; Sankarasubramanian, K.

The Ultra-Violet Imaging Telescope (UVIT) is one of the payloads in ASTROSAT, the first Indian Space Observatory. The UVIT instrument has two 375 mm telescopes: one for the far-ultraviolet (FUV) channel (1300–1800 Å), and the other for the near-ultraviolet (NUV) channel (2000–3000 Å) and the visible (VIS) channel (3200–5500 Å). UVIT is primarily designed for simultaneous imaging in the two ultraviolet channels with spatial resolution better than 1.″8, along with provisions for slit-less spectroscopy in the NUV and FUV channels. The results of in-orbit calibrations of UVIT are presented in this paper.

Improved Mirror Coatings for Use in the Lyman Ultraviolet to Enhance Astronomical Instrument Capabilities

NASA Technical Reports Server (NTRS)

Quijada, Manuel A.; Del Hoyo, Javier; Boris, David R.; Walton, Scott

2017-01-01

This paper will describe efforts at developing broadband mirror coatings with high performance that will extend from infrared wavelengths down to the Far-Ultraviolet (FUV) spectral region. These mirror coatings would be realized by passivating the surface of freshly made aluminum coatings with XeF2 gas in order to form a thin AlF3 overcoat that will protect the aluminum from oxidation and, hence, realize the high-reflectance of this material down to its intrinsic cut-off wavelength of 90 nm. Improved reflective coatings for optics, particularly in the FUV region (90-120 nm), could yield dramatically more sensitive instruments and permit more instrument design freedom.

Improved Lyman Ultraviolet Astronomy Capabilities through Enhanced Coatings

NASA Technical Reports Server (NTRS)

Quijada, Manuel A.; del Hoyo, Javier; Boris, David; Walton, Scott

2017-01-01

This paper will describe efforts at developing broadband mirror coatings with high performance that will extend from infrared wavelengths down to the Far-Ultraviolet (FUV) spectral region. These mirror coatings would be realized by passivating the surface of freshly made aluminum coatings with XeF2 gas in order to form a thin AlF$_3$ overcoat that will protect the aluminum from oxidation and, hence, realize the high-reflectance of this material down to its intrinsic cut-off wavelength of 90 nm. Improved reflective coatings for optics, particularly in the FUV region (90-120 nm), could yield dramatically more sensitive instruments and permit more instrument design freedom.

Improved mirror coatings for use in the Lyman Ultraviolet to enhance astronomical instrument capabilities

NASA Astrophysics Data System (ADS)

Quijada, Manuel A.; del Hoyo, Javier; Boris, David R.; Walton, Scott G.

2017-09-01

This paper will describe efforts at developing broadband mirror coatings with high performance that will extend from infrared wavelengths down to the Far-Ultraviolet (FUV) spectral region. These mirror coatings would be realized by passivating the surface of freshly made aluminum coatings with fluorine ions in order to form a thin AlF3 overcoat that will protect the aluminum from oxidation and, hence, realize the high-reflectance of this material down to its intrinsic cut-off wavelength of 90 nm. Improved reflective coatings for optics, particularly in the FUV region (90-120 nm), could yield dramatically more sensitive instruments and permit more instrument design freedom.