Richard Fredrick Gelderman

Hubble Space Telescope STIS Observations of the Kinematics of Emission-Line Nebulae in Three Compact Steep-Spectrum Radio Sources

We have obtained Hubble Space Telescope Space Telescope Imaging Spectrograph long-slit spectroscopy of the aligned emission-line nebulae in three compact steep-spectrum radio sources: 3C 67, 277.1, and 303.1. We find systematic offsets (~300–500 km s-1) of the emission-line velocities on one or both sides of the radio sources. We also see evidence for broad lines (FWHM ~ 500 km s-1) and complex emission-line profiles. In 3C 303.1 the data are consistent with multiple components and possibly split lines. The amplitude of the velocity variations is not so large as to exclude gravitationally induced motions. However, the complex kinematics, the lack of a signature of Keplerian rotation, and the association of the velocity variations with the radio lobes are consistent with the motions being driven by the expansion of the radio source. These kinematic signatures are consistent with an interaction between the expanding radio lobe and the emission-line clouds in which the clouds have been accelerated to velocities ~300–500 km s-1. Acceleration of the clouds by the bow shock is plausible given the estimated densities in the clouds and the velocities observed in the much smaller compact symmetric objects and with expansion velocities estimated from spectral aging.

Jet–Cloud Interactions in Compact Steep Spectrum Radio Sources

We have obtained HST/STIS long slit spectroscopy of the aligned emission line nebulae in three compact steep spectrum (CSS) radio sources - 3C67, 3C 277.1, and 3C 303.1. We find systematic offsets (similar to 300 - 500 km s(-1)) of the emission line velocities on one or both sides of the radio sources. We also see evidence for broad lines (FWHM similar to 500 km s(-1)) and complex emission line profiles. In 3C 303.1 the data are consistent with multiple components and possibly split lines. The amplitude of the velocity variations is not so large as to exclude gravitationally-induced motions. However, the complex kinematics, the lack of a signature of Keplerian rotation, and the association of the velocity variations with the radio lobes are consistent with the observed similar to 300-500 km s(-1) velocities being driven by the expansion of the radio source. Acceleration of the clouds by the bow shock is plausible given the estimated densities in the clouds and the velocities observed in the much smaller compact symmetric objects and with expansion velocities estimated from spectral ageing. This conclusion is unchanged if we consider the scenario in which the cloud acceleration is dominated by the post bow shock flow.

Emission-Line Properties of the Large Magellanic Cloud Bubble N70

We present a spectrophotometric imaging study of the emission bubble N70 (DEM 301) in the Large Magellanic Cloud. N70 is approximately 100 pc in size with a nearly circular shell-like morphology. The nebular emission is powered by an uncertain combination of EUV photons, intense winds, and supernova shock waves from the central population of high-mass stars (the OB association LH 114). We have obtained narrowband images (FWHM ~ 6 A) of N70 in the light of Hα λ6563, [N ii] λ6584, [S ii] λλ6717, 6731, and [O iii] λ5007, along with the corresponding red and green continua. The resulting line fluxes and flux ratios are used to derive ionization rates, nebular densities, volume filling fractions, and excitation indices. The photoionizing luminosity inferred from the embedded stellar population is more than adequate to account for the observed hydrogen ionization rate.We compare the emission-line photometry with that derived from similar imaging of the Orion Nebula and with data collected from the literature on other emission-line regions in the LMC. Compared with the Orion Nebula, N70 shows much higher [S ii]/Hα intensity ratios that increase smoothly with radius—from less than 0.3 near the center to greater than 1.0 toward the outer filamentary shell. The measured intensity ratios in N70 more closely match the range of excitation spanned by giant and supergiant H ii shells and by some of the supernova remnants observed in the LMC. The contending ionization and excitation processes in the interior and outer shell of N70 are evaluated in terms of the available data. EUV photons probably contribute most of the inner nebulas ionization, whereas a combination of photoionization plus collisional ionization and excitation of sulfur atoms by low-velocity shocks seems to best fit the emission-line luminosities and intensity ratios observed in the outer shell. Considerations of the radiative and mechanical energetics that are involved may indicate the need for one or two supernova explosions having occurred during the last ~Myr.

Spatially Resolved Spectra of 3C Galaxy Nuclei

We present and discuss visible-wavelength long-slit spectra of four low-redshift 3C galaxies obtained with the Space Telescope Imaging Spectrograph on the Hubble Space Telescope (HST). The slit was aligned with near-nuclear jetlike structure seen in HST images of the galaxies, to give unprecedented spatial resolution of their inner regions. In 3C 135 and 3C 171, the spectra reveal clumpy emission-line structures that indicate outward motions of a few hundred kilometers per second within a centrally illuminated and ionized biconical region. There may also be some low-ionization, high-velocity material associated with 3C 135. In 3C 264 and 3C 78, the jets have blue featureless spectra consistent with their proposed synchrotron origin. There is weak associated line emission in the innermost part of the jets with mild outflow velocity. These jets are bright and highly collimated only within a circumnuclear region of lower galaxy luminosity, which is not dusty. We discuss the origins of these central regions and their connection with relativistic jets.

AN OPTICAL STUDY OF COMPACT STEEP-SPECTRUM RADIO SOURCES

We present results from an optical study of Compact Steep-Spectrum (CSS) radio galaxies and quasars. The distinguishing characteristic of the CSS class is that their powerful radio lobes do not extend outside the host galaxy. CSS sources resemble miniature versions of the classical double radio galaxies and quasars, but high resolution radio interferometry is required to identify the double-lobed or core-jet radio morphologies. One explanation for such intrinsically small radio structures is that CSS objects are youthful sources which have not had time to expand into classical double radio sources. Alternatively, CSS objects might be of a normal age yet still compact due to confinement through strong interaction with the interstellar medium. Extensive radio investigations have yielded insights into the nature of CSS sources, but this is the first comprehensive optical study. Using the KPNO 2.1-m and 4-m telescopes we obtained broad band images and both low and high dispersion spectra for a sample of 19 CSS sources. We find that the CSS sources in our sample have similar optical characteristics and conclude that the CSS classification is physically meaningful, rather than being a collection of objects which appear to be compact for various unrelated reasons. Our optical data (Gelderman & Whittle 1994, ApJS, 91, 491) support a picture in which the CSS radio sources are interacting with the optical line emitting gas; although we are unable to distinguish between the normal expansion of a young source and a source which is contained by an exceptionally dense NLR. The most dramatic aspect of the spectra is that as a class, the CSS sources have remarkably broad, structured [O III] profiles with kinematics which are distinct from all other classes of AGN. Such exceptional velocity structure is presumably due to acceleration of the ambient gas by the powerful jets and lobes. The CSS objects in our sample may be typified as extremely luminous, high excitation line emission sources. As a class they have greater [O III] flux and equivalent width than other classes of AGN. Unexpectedly, we find little relation between the enhanced line emission and the powerful subgalactic radio source. The data from our CSS sample fall along the established correlation between line luminosity and total radio power. If the high NLR luminosities are due to ionization related to the radio structure then one might expect CSS sources would have greater line luminosity at a given radio power than other radio galaxies or quasars. Furthermore, we are unable to identify emission line flux ratios which might indicate that the radio jet plays a direct role in the ionization. Instead, photoionization by the active nucleus and a high covering factor in the NLR can explain the luminous, high equivalent width, high excitation line emission. From our imaging program we conclude that galaxy-galaxy interactions, as indicated by disturbed hosts and/or nearby companions, are suggested for every member of our CSS sample. Such interactions are important for other classes of radio-loud AGN and it is not surprising that they should be an important aspect of the CSS phenomenon. However, we are unable to determine any link to the other notable properties of CSS sources which might allow us to favor either explanation as to why CSS have such powerful yet compact radio structure.

Instrumentation for the Citizen CATE Experiment: Faroe Islands and Indonesia

The inner regions of the solar corona from 1–2.5 Rsun are poorly sampled both from the ground and space telescopes. A solar eclipse reduces the sky scattered background intensity by a factor of about 10,000 and opens a window to view this region directly. The goal of the Citizen Continental-America Telescopic Eclipse (CATE) Experiment is to take a 90-minute time sequence of calibrated white-light images of this coronal region using 60 identical telescopes spread from Oregon to South Carolina during the 2017 August 21 total solar eclipse. Observations that can address questions of coronal dynamics in this region can be collected with rather modest telescope equipment, but the large dynamic range of the coronal brightness requires careful camera control. The instruments used for test runs on the Faroe Islands in 2015 and at five sites in Indonesia in 2016 are described. Intensity calibration of the coronal images is done and compared with previous eclipse measurements from November & Koutchmy and Bazin et al. The change of coronal brightness with distance from the Sun seen in the 2016 eclipse agrees with observations from the 1991 eclipse, but differ substantially from the 2010 eclipse. The 2015 observations agree with 2016 and 1991 solar radii near the Sun, but are fainter at larger distances. Problems encountered during these test runs are discussed as well the solutions which will be implemented for the 2017 eclipse experiment.

THE RCT 1.3 m ROBOTIC TELESCOPE: BROADBAND COLOR TRANSFORMATION AND EXTINCTION CALIBRATION

The Robotically Controlled Telescope (RCT) 1.3 m telescope, formerly known as the Kitt Peak National Observatory (KPNO) 50 inch telescope, has been refurbished as a fully robotic telescope, with an autonomous scheduler to take full advantage of the observing site without the requirement of a human presence. Here we detail the current configuration of the RCT and present, as a demonstration of its high-priority science goals, the broadband UBVRI photometric calibration of the optical facility. In summary, we find the linear color transformation and extinction corrections to be consistent with similar optical KPNO facilities, to within a photometric precision of 10% (at 1σ). While there were identified instrumental errors that likely added to the overall uncertainty, associated with since-resolved issues in engineering and maintenance of the robotic facility, a preliminary verification of this calibration gave a good indication that the solution is robust, perhaps to a higher precision than this initial calibration implies. The RCT has been executing regular science operations since 2009 and is largely meeting the science requirements set during its acquisition and redesign.

The 1.3-meter Robotically Controlled Telescope: Developing a Fully Autonomous Observatory

The former KPNO 1.3-meter telescope is being refurbished and automated by a consortium of U.S. institutions, headed by Western Kentucky University, with the goal of a 2002 recommissioning as the Robotically Controlled Telescope (RCT). The 1.3-meter RCT will operate in fully autonomous mode to obtain guided images for a variety of research and education programs. Distinctions between a fully autonomous versus robotic observatory are presented, along with a discussion of why fully autonomous operation is necessary for increased productivity of small telescopes.

Spectroscopy of CSS Sources

Since their discovery, CSS and GPS sources have been growing in relevance. Although their nature is still not well understood, the latest studies show that these sources may be the progenitors of the large-scale powerful classical doubles. We have obtained long slit spectra of 3C67 and 3C277.1 with the HST/STIS spectrograph and present our preliminary results on the diagnostic emission line ratios along the radio source axes in 3C67 and 3C277.1.

STARBASE: A Network of Fully Autonomous Telescopes for Hands-on Science Education

Students Training for Achievement in Research Based on Analytical Space-science Experiences (STARBASE) is being established to provide exciting hands-on research opportunities for students. STARBASE is a network of networks, consisting of dedicated hardware, universities, professional astronomers, teachers, and students all working together in scientific investigations. Funded through the NASA Office of Space Science, the STARBASE network is working to bring major science research projects to motivated students all over the globe. Western Kentucky University is the lead institution for STARBASE Students Training for Achievement in Research Based on Analytical Spacescience Experiences. In 1999, WKU received funding from NASAs Office of Space Science, allowing us to begin to put into place the networks of hardware, universities, teachers, and students which comprise STARBASE. The Network of Hardware: Fully autonomous observatories have recently been made possible through the revolutionary advances in computing technology. Advances in computing power and networking allow even remote institutions with limited budgets to operate a small telescope at a world-class observing site. The STARBASE network of observatories with the first of three fully autonomous meter-class telescopes coming on-line is another example of the recent efforts to establish global networks of small telescopes. The 0.6-meter Western Kentucky University telescope is located near Bowling Green, Kentucky (latitude = +36°55, longitude = +86°36.7, elevation 225m). The telescope system has been refurbished and automated by Astronomical Consultants and Equipment, Inc. of Tucson, Arizona. Commissioning tests were being performed at the time of this conference, with the intention of achieving robotic operation in the spring of 2001. The 1.3-meter Robotically Controlled Telescope (RCT) is located at the Kitt Peak National Observatory (latitude = +31°57, longitude = +111°35.7, elevation 2064m). The refurbishment and automation of the former KPNO 1.3meter is being undertaken by EOS Technologies, Inc. of Tucson, Arizona, and recommissioning of the RCT is scheduled for early 2002. Negotiations to locate a new meter-class fully autonomous telescope at the Wise Observatory in Israel (latitude = +30°36, longitude = —31°45.8, elevation 900m) are progressing well, though no start date has been established. An additional observatory at a site in eastern Asia is desired, but funding had not yet been secured as of this conference.