Gerald Cecil | University of North Carolina at Chapel Hill (original) (raw)
Papers by Gerald Cecil
The Astrophysical Journal, 2012
Reviews of environmental contamination and toxicology, 2007
The prime focus of ethanol production from corn is to replace the imported oil used in American v... more The prime focus of ethanol production from corn is to replace the imported oil used in American vehicles, without expending more fossil energy in ethanol production than is produced as ethanol energy. In a thorough and up-to-date evaluation of all the fossil energy costs of ethanol production from corn, every step in the production and conversion process must be included. In this study, 14 energy inputs in average U.S. corn production are included. Then, in the fermentation/distillation operation, 9 more identified fossil fuel inputs are included. Some energy and economic credits are given for the by-products, including dried distillers grains (DDG). Based on all the fossil energy inputs, a total of 1.43 kcal fossil energy is expended to produced 1 kcal ethanol. When the energy value of the DDG, based on the feed value of the DDG as compared to that of soybean meal, is considered, the energy cost of ethanol production is reduced slightly, to 1.28 kcal fossil energy input per 1 kcal ...
We present the first scientific results from the Sydney-AAO Multi-Object IFS (SAMI) at the Anglo-... more We present the first scientific results from the Sydney-AAO Multi-Object IFS (SAMI) at the Anglo-Australian Telescope. This unique instrument deploys 13 fused fibre bundles (hexabundles) across a one-degree field of view allowing simultaneous spatially-resolved spectroscopy of 13 galaxies. During the first SAMI commissioning run, targeting a single galaxy field, one object (ESO 185-G031) was found to have extended minor axis emission with ionisation and kinematic properties consistent with a large-scale galactic wind. The importance of this result is two-fold: (i) fibre bundle spectrographs are able to identify low-surface brightness emission arising from extranuclear activity; (ii) such activity may be more common than presently assumed because conventional multi-object spectrographs use single-aperture fibres and spectra from these are nearly always dominated by nuclear emission. These early results demonstrate the extraordinary potential of multi-object hexabundle spectroscopy in...
The Astrophysical Journal
MeerKAT radio continuum and XMM-Newton X-ray images have recently revealed a spectacular bipolar ... more MeerKAT radio continuum and XMM-Newton X-ray images have recently revealed a spectacular bipolar channel at the Galactic Center that spans several degrees (∼0.5 kpc). An intermittent jet likely formed this channel and is consistent with earlier evidence of a sustained, Seyfert-level outburst fueled by black hole accretion onto Sgr A* several Myr ago. Therefore, to trace a now weak jet that perhaps penetrated, deflected, and percolated along multiple paths through the interstellar medium, relevant interactions are identified and quantified in archival X-ray images, Hubble Space Telescope Paschen α images and Atacama Large Millimeter/submillimeter Array millimeter-wave spectra, and new SOAR telescope IR spectra. Hydrodynamical simulations are used to show how a nuclear jet can explain these structures and inflate the ROSAT/eROSITA X-ray and Fermi γ-ray bubbles that extend ± 75° from the Galactic plane. Thus, our Galactic outflow has features in common with energetic, jet-driven struct...
Revista Mexicana De Astronomia Y Astrofisica, 2002
HST images and spectra of high-velocity outo ws from three AGN: (1) Show 5 00 -long bow shock/Mac... more HST images and spectra of high-velocity outo ws from three AGN: (1) Show 5 00 -long bow shock/Mach disk complexes at the ends of the active radio jet in NGC 4258. We argue that the jet has precessed to its current orientation seen at VLBI-scales. (2) Fully resolve [O III] 5007 A and H line proles in the NLR of NGC 1068, and show compact knots with blueshifted radial velocities >3100 km s 1 relative to ambient gas. The knots lie several arcseconds outside the nucleus, on and away from the radio jet, and are kinematically contiguous with brighter clouds moving 200{800 km s 1 relative to systemic. We argue that the knots are ablata streams undergoing radiative acceleration from jet-agitated, massive clouds. They are good candidates for \intrinsic UV absorbers" seen in other AGN. (3) Resolve many of the lamen ts that form the 1 kpc-diameter superbubble of NGC 3079. Combining with ground-based Fabry-Perot spectra, we constrain gas densities, gas lling factors, and space velocitie...
Bulletin of the American Astronomical Society, 1987
We present low-resolution ultraviolet spectra of 14 low redshift (zem . 0.8) quasars observed wit... more We present low-resolution ultraviolet spectra of 14 low redshift (zem . 0.8) quasars observed with HST/STIS as part of a Snap project to understand the relationship between quasar outflows and luminosity. By design, all observations cover the C IV emission line. Nine of the quasars are from the Hamburg-ESO catalog, three are from the Palomar-Green catalog, and one is from the Parkes catalog. The sample contains a few interesting quasars including two broad absorption line (BAL) quasars (HE 01433535, HE0436-2614), one quasar with a mini-BAL (HE 1105-0746), and one quasar with associated narrow absorption (HE 0409-5004). These BAL quasars are among the brightest known (though not the most luminous) since they lie at zem < 0.8. We compare the properties of these BAL quasars to the zem < 0.5 Palomar-Green and zem > 1.4 Large Bright Quasar samples. By design, our objects sample luminosities in between these two surveys, and our four absorbed objects are consistent with the v ∼ L...
ABSTRACT NGC 4258 (M106) is a nearby (7 Mpc, 0\farcs1 = 3.5 pc) active spiral galaxy, distinguish... more ABSTRACT NGC 4258 (M106) is a nearby (7 Mpc, 0\farcs1 = 3.5 pc) active spiral galaxy, distinguished by long (5' projected extent), narrow (5\arcsec) radio jets. The jets are jointed, linear segments that are embedded in diffuse plateaux of radio and X-ray emission. They flow close to the galaxy gas disk, entraining and shocking the ISM; X-rays with a thermal spectrum are prominent from the hottest shocked gas, and optical line ratios are also consistent with shock excitation. The jets have been traced with VLBA back close to the 0.1-pc radius accretion disk that surrounds the nuclear black hole (3.5*E(7) M_sun, dynamical estimate from ongoing maser monitoring.) We discuss new Hα (658N -- 547M) WFPC2 images from HST. These reveal an emission-line ``bow" whose apex points away from the galaxy nucleus (25'' distant.) This arc spans 5'' across the jet (tracing precession of the jet in a gas recombination time if it is photoionized by dissipated mechanical energy, or the opening angle of the obscuring torus if it is photoionized directly by the AGN), is barely resolved in the WFC along the jet, and has a bright knot in its W half that coincides with the terminus of the linear radio jet in our ABC-configuration 20-cm VLA image. Our existing Fabry-Perot Hα and [O III]lambda 5007 line-profile datacubes show kinematic disturbances near this putative bow shock. We use these data and the new WFPC2 images to derive kinematic and photometric parameters of this jet/ISM interaction. These data constrain the dynamical evolution of the active outflow. We also present simulations of an upcoming deep AXAF-grating spectrum to show how we will establish physical conditions of the hottest shocked gas. Work supported by NASA GO grants (HST GO-6563, AXAF GO-TBD).
Ground-based and Airborne Telescopes VII
The linear Atmospheric Dispersion Corrector has been operating at the SOuthern Astrophysical Rese... more The linear Atmospheric Dispersion Corrector has been operating at the SOuthern Astrophysical Research telescope since 2014. It was designed and built in collaboration between the University of North Carolina at Chapel Hill, and Cerro Tololo Inter-American Observatory. The device is installed in the elevation axis before the instruments mounted at the optical Nasmyth focus. It consists of two 300mm diameter sol-gel coated fused silica prisms, trombone mounted, which can be folded in or out of the beam. It is important for long slit spectroscopy, and essential for Multi-Object Slit spectroscopy. We present optical and mechanical designs, electronics and software control, and on-sky performance.
Galactic winds are the primary mechanism by which energy and metals are recycled in galaxies and ... more Galactic winds are the primary mechanism by which energy and metals are recycled in galaxies and are deposited into the intergalactic medium. New observations are revealing the ubiquity of this process, particularly at high redshift. We describe the physics behind these winds, discuss the observational evidence for them in nearby star-forming and active galaxies and in the high-redshift universe, and consider the implications of energetic winds for the formation and evolution of galaxies and the intergalactic medium. To inspire future research, we conclude with a set of observational and theoretical challenges.
Revista Mexicana De Astronomia Y Astrofisica, 2001
RESUMEN Se presentan resultados recientes de un levantamiento multifrecuencia de ujos espacialmen... more RESUMEN Se presentan resultados recientes de un levantamiento multifrecuencia de ujos espacialmente resueltos en galaxias activas cercanas. Se combinan datos espectrosc opicos opticos de Fabry-Perot y de rendija larga con im agenes del VLA (siglas en ingl es de \Very Large Array") y de ROSAT (siglas en alem an de \Roentgen Satellit"), cuando disponibles, para estudiar las componentes gaseosas tibias, relativistas y calientes involucradas en el ujo. Se pone enfasis en objetos que contienen ujos de angulo amplios y escala gal actica, pero tambi en que muestran evidencia de fen omenos tipo jet colimado a longitudes de ondas de radio y opticas (p.ej., Circinus, NGC 4388, y con menor intensidad NGC 2992). Nuestros resultados se comparan con las predicciones publicadas de modelos de vientos t ermicos impulsados por jets.
The luminous spiral NGC 1068 has now been imaged from x-ray to radio wavelengths at comparably hi... more The luminous spiral NGC 1068 has now been imaged from x-ray to radio wavelengths at comparably high resolution (approximately less than 5 in. FWHM). The bolometric luminosity of this well-known Seyfert is shared almost equally between the active nucleus and an extended 'starburst' disk. In an ongoing study, we are investigating the relative importance of the nucleus and the disk in powering the wide range of energetic activity observed throughout the galaxy. Our detailed analysis brings together a wealth of data: ROSAT HRI observations, VLA lambda lambda 6-20 cu cm and OVRO interferometry, lambda lambda 0.4-10.8 micron imaging, and Fabry-Perot spectrophotometry.
Galactic winds are the primary mechanism by which energy and metals are recycled in galaxies and ... more Galactic winds are the primary mechanism by which energy and metals are recycled in galaxies and are deposited into the intergalactic medium. New observations are revealing the ubiquity of this process, particularly at high redshift. We describe the physics behind these winds, discuss the observational evidence for them in nearby star-forming and active galaxies and in the high-redshift universe, and consider the implications of energetic winds for the formation and evolution of galaxies and the intergalactic medium. To inspire future research, we conclude with a set of observational and theoretical challenges.
The Astrophysical Journal, 2012
Reviews of environmental contamination and toxicology, 2007
The prime focus of ethanol production from corn is to replace the imported oil used in American v... more The prime focus of ethanol production from corn is to replace the imported oil used in American vehicles, without expending more fossil energy in ethanol production than is produced as ethanol energy. In a thorough and up-to-date evaluation of all the fossil energy costs of ethanol production from corn, every step in the production and conversion process must be included. In this study, 14 energy inputs in average U.S. corn production are included. Then, in the fermentation/distillation operation, 9 more identified fossil fuel inputs are included. Some energy and economic credits are given for the by-products, including dried distillers grains (DDG). Based on all the fossil energy inputs, a total of 1.43 kcal fossil energy is expended to produced 1 kcal ethanol. When the energy value of the DDG, based on the feed value of the DDG as compared to that of soybean meal, is considered, the energy cost of ethanol production is reduced slightly, to 1.28 kcal fossil energy input per 1 kcal ...
We present the first scientific results from the Sydney-AAO Multi-Object IFS (SAMI) at the Anglo-... more We present the first scientific results from the Sydney-AAO Multi-Object IFS (SAMI) at the Anglo-Australian Telescope. This unique instrument deploys 13 fused fibre bundles (hexabundles) across a one-degree field of view allowing simultaneous spatially-resolved spectroscopy of 13 galaxies. During the first SAMI commissioning run, targeting a single galaxy field, one object (ESO 185-G031) was found to have extended minor axis emission with ionisation and kinematic properties consistent with a large-scale galactic wind. The importance of this result is two-fold: (i) fibre bundle spectrographs are able to identify low-surface brightness emission arising from extranuclear activity; (ii) such activity may be more common than presently assumed because conventional multi-object spectrographs use single-aperture fibres and spectra from these are nearly always dominated by nuclear emission. These early results demonstrate the extraordinary potential of multi-object hexabundle spectroscopy in...
The Astrophysical Journal
MeerKAT radio continuum and XMM-Newton X-ray images have recently revealed a spectacular bipolar ... more MeerKAT radio continuum and XMM-Newton X-ray images have recently revealed a spectacular bipolar channel at the Galactic Center that spans several degrees (∼0.5 kpc). An intermittent jet likely formed this channel and is consistent with earlier evidence of a sustained, Seyfert-level outburst fueled by black hole accretion onto Sgr A* several Myr ago. Therefore, to trace a now weak jet that perhaps penetrated, deflected, and percolated along multiple paths through the interstellar medium, relevant interactions are identified and quantified in archival X-ray images, Hubble Space Telescope Paschen α images and Atacama Large Millimeter/submillimeter Array millimeter-wave spectra, and new SOAR telescope IR spectra. Hydrodynamical simulations are used to show how a nuclear jet can explain these structures and inflate the ROSAT/eROSITA X-ray and Fermi γ-ray bubbles that extend ± 75° from the Galactic plane. Thus, our Galactic outflow has features in common with energetic, jet-driven struct...
Revista Mexicana De Astronomia Y Astrofisica, 2002
HST images and spectra of high-velocity outo ws from three AGN: (1) Show 5 00 -long bow shock/Mac... more HST images and spectra of high-velocity outo ws from three AGN: (1) Show 5 00 -long bow shock/Mach disk complexes at the ends of the active radio jet in NGC 4258. We argue that the jet has precessed to its current orientation seen at VLBI-scales. (2) Fully resolve [O III] 5007 A and H line proles in the NLR of NGC 1068, and show compact knots with blueshifted radial velocities >3100 km s 1 relative to ambient gas. The knots lie several arcseconds outside the nucleus, on and away from the radio jet, and are kinematically contiguous with brighter clouds moving 200{800 km s 1 relative to systemic. We argue that the knots are ablata streams undergoing radiative acceleration from jet-agitated, massive clouds. They are good candidates for \intrinsic UV absorbers" seen in other AGN. (3) Resolve many of the lamen ts that form the 1 kpc-diameter superbubble of NGC 3079. Combining with ground-based Fabry-Perot spectra, we constrain gas densities, gas lling factors, and space velocitie...
Bulletin of the American Astronomical Society, 1987
We present low-resolution ultraviolet spectra of 14 low redshift (zem . 0.8) quasars observed wit... more We present low-resolution ultraviolet spectra of 14 low redshift (zem . 0.8) quasars observed with HST/STIS as part of a Snap project to understand the relationship between quasar outflows and luminosity. By design, all observations cover the C IV emission line. Nine of the quasars are from the Hamburg-ESO catalog, three are from the Palomar-Green catalog, and one is from the Parkes catalog. The sample contains a few interesting quasars including two broad absorption line (BAL) quasars (HE 01433535, HE0436-2614), one quasar with a mini-BAL (HE 1105-0746), and one quasar with associated narrow absorption (HE 0409-5004). These BAL quasars are among the brightest known (though not the most luminous) since they lie at zem < 0.8. We compare the properties of these BAL quasars to the zem < 0.5 Palomar-Green and zem > 1.4 Large Bright Quasar samples. By design, our objects sample luminosities in between these two surveys, and our four absorbed objects are consistent with the v ∼ L...
ABSTRACT NGC 4258 (M106) is a nearby (7 Mpc, 0\farcs1 = 3.5 pc) active spiral galaxy, distinguish... more ABSTRACT NGC 4258 (M106) is a nearby (7 Mpc, 0\farcs1 = 3.5 pc) active spiral galaxy, distinguished by long (5' projected extent), narrow (5\arcsec) radio jets. The jets are jointed, linear segments that are embedded in diffuse plateaux of radio and X-ray emission. They flow close to the galaxy gas disk, entraining and shocking the ISM; X-rays with a thermal spectrum are prominent from the hottest shocked gas, and optical line ratios are also consistent with shock excitation. The jets have been traced with VLBA back close to the 0.1-pc radius accretion disk that surrounds the nuclear black hole (3.5*E(7) M_sun, dynamical estimate from ongoing maser monitoring.) We discuss new Hα (658N -- 547M) WFPC2 images from HST. These reveal an emission-line ``bow" whose apex points away from the galaxy nucleus (25'' distant.) This arc spans 5'' across the jet (tracing precession of the jet in a gas recombination time if it is photoionized by dissipated mechanical energy, or the opening angle of the obscuring torus if it is photoionized directly by the AGN), is barely resolved in the WFC along the jet, and has a bright knot in its W half that coincides with the terminus of the linear radio jet in our ABC-configuration 20-cm VLA image. Our existing Fabry-Perot Hα and [O III]lambda 5007 line-profile datacubes show kinematic disturbances near this putative bow shock. We use these data and the new WFPC2 images to derive kinematic and photometric parameters of this jet/ISM interaction. These data constrain the dynamical evolution of the active outflow. We also present simulations of an upcoming deep AXAF-grating spectrum to show how we will establish physical conditions of the hottest shocked gas. Work supported by NASA GO grants (HST GO-6563, AXAF GO-TBD).
Ground-based and Airborne Telescopes VII
The linear Atmospheric Dispersion Corrector has been operating at the SOuthern Astrophysical Rese... more The linear Atmospheric Dispersion Corrector has been operating at the SOuthern Astrophysical Research telescope since 2014. It was designed and built in collaboration between the University of North Carolina at Chapel Hill, and Cerro Tololo Inter-American Observatory. The device is installed in the elevation axis before the instruments mounted at the optical Nasmyth focus. It consists of two 300mm diameter sol-gel coated fused silica prisms, trombone mounted, which can be folded in or out of the beam. It is important for long slit spectroscopy, and essential for Multi-Object Slit spectroscopy. We present optical and mechanical designs, electronics and software control, and on-sky performance.
Galactic winds are the primary mechanism by which energy and metals are recycled in galaxies and ... more Galactic winds are the primary mechanism by which energy and metals are recycled in galaxies and are deposited into the intergalactic medium. New observations are revealing the ubiquity of this process, particularly at high redshift. We describe the physics behind these winds, discuss the observational evidence for them in nearby star-forming and active galaxies and in the high-redshift universe, and consider the implications of energetic winds for the formation and evolution of galaxies and the intergalactic medium. To inspire future research, we conclude with a set of observational and theoretical challenges.
Revista Mexicana De Astronomia Y Astrofisica, 2001
RESUMEN Se presentan resultados recientes de un levantamiento multifrecuencia de ujos espacialmen... more RESUMEN Se presentan resultados recientes de un levantamiento multifrecuencia de ujos espacialmente resueltos en galaxias activas cercanas. Se combinan datos espectrosc opicos opticos de Fabry-Perot y de rendija larga con im agenes del VLA (siglas en ingl es de \Very Large Array") y de ROSAT (siglas en alem an de \Roentgen Satellit"), cuando disponibles, para estudiar las componentes gaseosas tibias, relativistas y calientes involucradas en el ujo. Se pone enfasis en objetos que contienen ujos de angulo amplios y escala gal actica, pero tambi en que muestran evidencia de fen omenos tipo jet colimado a longitudes de ondas de radio y opticas (p.ej., Circinus, NGC 4388, y con menor intensidad NGC 2992). Nuestros resultados se comparan con las predicciones publicadas de modelos de vientos t ermicos impulsados por jets.
The luminous spiral NGC 1068 has now been imaged from x-ray to radio wavelengths at comparably hi... more The luminous spiral NGC 1068 has now been imaged from x-ray to radio wavelengths at comparably high resolution (approximately less than 5 in. FWHM). The bolometric luminosity of this well-known Seyfert is shared almost equally between the active nucleus and an extended 'starburst' disk. In an ongoing study, we are investigating the relative importance of the nucleus and the disk in powering the wide range of energetic activity observed throughout the galaxy. Our detailed analysis brings together a wealth of data: ROSAT HRI observations, VLA lambda lambda 6-20 cu cm and OVRO interferometry, lambda lambda 0.4-10.8 micron imaging, and Fabry-Perot spectrophotometry.
Galactic winds are the primary mechanism by which energy and metals are recycled in galaxies and ... more Galactic winds are the primary mechanism by which energy and metals are recycled in galaxies and are deposited into the intergalactic medium. New observations are revealing the ubiquity of this process, particularly at high redshift. We describe the physics behind these winds, discuss the observational evidence for them in nearby star-forming and active galaxies and in the high-redshift universe, and consider the implications of energetic winds for the formation and evolution of galaxies and the intergalactic medium. To inspire future research, we conclude with a set of observational and theoretical challenges.