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44 results on '"Finn, Susanna C."'

1. Inverting OII 83.4 nm Dayglow Profiles Using Markov Chain Radiative Transfer

Author

Geddes, George, Douglas, Ewan, Finn, Susanna C., Cook, Timothy, and Chakrabarti, Supriya

Subjects
Physics - Space Physics, Astrophysics - Instrumentation and Methods for Astrophysics
Abstract

Emission profiles of the resonantly scattered OII~83.4~nm triplet can in principle be used to estimate \(\mathrm{O}^+\) density profiles in the F2 region of the ionosphere. Given the emission source profile, solution of this inverse problem is possible, but requires significant computation. The traditional Feautrier solution to the radiative transfer problem requires many iterations to converge, making it time-consuming to compute. A Markov chain approach to the problem produces similar results by directly constructing a matrix that maps the source emission rate to an effective emission rate which includes scattering to all orders. The Markov chain approach presented here yields faster results and therefore can be used to perform the \(\mathrm{O}^+\) density retrieval with higher resolution than would otherwise be possible.

Published
2016
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2. Volumetric imaging of rod and cone photoreceptor structure with a combined adaptive optics-optical coherence tomography-scanning laser ophthalmoscope

Author

Wells-Gray, Elaine M, Choi, Stacey S, Zawadzki, Robert J, Finn, Susanna C, Greiner, Cherry, Werner, John S, and Doble, Nathan

Subjects
Biomedical and Clinical Sciences, Ophthalmology and Optometry, Neurosciences, Eye Disease and Disorders of Vision, Biomedical Imaging, Clinical Research, Neurodegenerative, Rare Diseases, Bioengineering, Eye, Adult, Algorithms, Humans, Imaging, Three-Dimensional, Ophthalmoscopy, Photoreceptor Cells, Vertebrate, Retina, Tomography, Optical Coherence, Young Adult, adaptive optics, optical coherence tomography, scanning laser ophthalmoscopy, photoreceptors, cones, rods, 3-D imaging, Optical Physics, Biomedical Engineering, Opthalmology and Optometry, Optics, Ophthalmology and optometry, Biomedical engineering, Atomic, molecular and optical physics
Abstract

We have designed and implemented a dual-mode adaptive optics (AO) imaging system that combines spectral domain optical coherence tomography (OCT) and scanning laser ophthalmoscopy (SLO) for in vivo imaging of the human retina. The system simultaneously acquires SLO frames and OCT B-scans at 60 Hz with an OCT volume acquisition time of 4.2 s. Transverse eye motion measured from the SLO is used to register the OCT B-scans to generate three-dimensional (3-D) volumes. Key optical design considerations include: minimizing system aberrations through the use of off-axis relay telescopes, conjugate pupil plane requirements, and the use of dichroic beam splitters to separate and recombine the OCT and SLO beams around the nonshared horizontal scanning mirrors. To demonstrate system performance, AO-OCT-SLO images and measurements are taken from three normal human subjects ranging in retinal eccentricity from the fovea out to 15-deg temporal and 20-deg superior. Also presented are en face OCT projections generated from the registered 3-D volumes. The ability to acquire high-resolution 3-D images of the human retina in the midperiphery and beyond has clinical importance in diseases, such as retinitis pigmentosa and cone-rod dystrophy.

Published
2018

3. Distributed Low-Mass Star Formation in the IRDC G34.43+00.24

Author

Foster, Jonathan B., Arce, Héctor G., Kassis, Marc, Sanhueza, Patricio, Jackson, James M., Finn, Susanna C., Offner, Stella, Sakai, Takeshi, Sakai, Nami, Yamamoto, Satoshi, Guzmán, Andrés E., and Rathborne, Jill M.

Subjects
Astrophysics - Astrophysics of Galaxies, Astrophysics - Solar and Stellar Astrophysics
Abstract

We have used deep near-infrared observations with adaptive optics to discover a distributed population of low-mass protostars within the filamentary Infrared Dark Cloud G34.43+00.24. We use maps of dust emission at multiple wavelengths to determine the column density structure of the cloud. In combination with an empirically-verified model of the magnitude distribution of background stars, this column density map allows us to reliably determine overdensities of red sources that are due to embedded protostars in the cloud. We also identify protostars through their extended emission in K-band which comes from excited H2 in protostellar outflows or reflection nebulosity. We find a population of distributed low-mass protostars, suggesting that low-mass protostars may form earlier than, or contemporaneously with, high-mass protostars in such a filament. The low-mass protostellar population may also produce the narrow linewidth SiO emission observed in some clouds without high-mass protostars. Finally, we use a molecular line map of the cloud to determine the virial parameter per unit length along the filament and find that the highest mass protostars form in the most bound portion of the filament, as suggested by theoretical models., Comment: 15 pages, 16 figures. This version add internal hypertext links to references, figures and tables. Full quality version at http://www.astro.yale.edu/foster/papers/Foster_2014_DistributedSF.pdf

Published
2014
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4. Performance of a combined optical coherence tomography and scanning laser ophthalmoscope with adaptive optics for human retinal imaging applications

Author

Wells-Gray, Elaine M, Zawadzki, Robert J, Finn, Susanna C, Greiner, Cherry, Werner, John S, Choi, Stacey S, and Doble, Nathan

Subjects
Adaptive optics, Optical coherence tomography, Scanning Laser Ophthalmoscopy, Retina, Photoreceptors, Cones, Rods
Abstract

We describe the design and performance of a recently implemented retinal imaging system for the human eye that combines adaptive optics (AO) with spectral domain optical coherence tomography (OCT) and scanning laser ophthalmoscopy (SLO). The AO-OCT-SLO system simultaneously acquires SLO frames and OCT B-scans at 60 Hz with an OCT volume acquisition scan rate of 0.24 Hz. The SLO images are used to correct for eye motion during the registration of OCT B-scans. Key optical design considerations are discussed including: minimizing system aberrations through the use of off-axis relay telescopes; choice of telescope magnification based on pupil plane requirements and restrictions; and the use of dichroic beam splitters to separate and re-combine OCT and SLO beams around the nonshared horizontal scanning mirrors. We include an analysis of closed-loop AO correction on a model eye and compare these findings with system performance in vivo. The 2D and 3D OCT scans included in this work demonstrate the ability of this system to laterally and axially resolve individual cone photoreceptors, while the corresponding SLO images show the en face mosaics at the photoreceptor layer showing rods and cones. Images from both healthy and diseased retina are presented.

Published
2015

5. Chemistry in Infrared Dark Cloud Clumps: a Molecular Line Survey at 3 mm

Author

Sanhueza, Patricio, Jackson, James M., Foster, Jonathan B., Garay, Guido, Silva, Andrea, and Finn, Susanna C.

Subjects
Astrophysics - Astrophysics of Galaxies
Abstract

We have observed 37 Infrared Dark Clouds (IRDCs), containing a total of 159 clumps, in high-density molecular tracers at 3 mm using the 22-meter ATNF Mopra Telescope located in Australia. After determining kinematic distances, we eliminated clumps that are not located in IRDCs and clumps with a separation between them of less than one Mopra beam. Our final sample consists of 92 IRDC clumps. The most commonly detected molecular lines are (detection rates higher than 8%): N2H+, HNC, HN13C, HCO+, H13CO+, HCN, C2H, HC3N, HNCO, and SiO. We investigate the behavior of the different molecular tracers and look for chemical variations as a function of an evolutionary sequence based on Spitzer IRAC and MIPS emission. We find that the molecular tracers behave differently through the evolutionary sequence and some of them can be used to yield useful relative age information. The presence of HNC and N2H+ lines do not depend on the star formation activity. On the other hand, HC3N, HNCO, and SiO are predominantly detected in later stages of evolution. Optical depth calculations show that in IRDC clumps the N2H+ line is optically thin, the C2H line is moderately optically thick, and HNC and HCO+ are optically thick. The HCN hyperfine transitions are blended, and, in addition, show self-absorbed line profiles and extended wing emission. These factors combined prevent the use of HCN hyperfine transitions for the calculation of physical parameters. Total column densities of the different molecules, except C2H, increase with the evolutionary stage of the clumps. Molecular abundances increase with the evolutionary stage for N2H+ and HCO+. The N2H+/HCO+ and N2H+/HNC abudance ratios act as chemical clocks, increasing with the evolution of the clumps., Comment: Accepted to ApJ. 29 pages

Published
2012
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6. The Millimeter Astronomy Legacy Team 90 GHz (MALT90) Pilot Survey

Author

Foster, Jonathan B., Jackson, James M., Barris, Elizabeth, Brooks, Kate, Cunningham, Maria, Finn, Susanna C., Fuller, Gary A., Longmore, Steve N., Mascoop, Joshua L., Peretto, Nicholas, Rathborne, Jill, Sanhueza, Patricio, Schuller, Frédéric, and Wyrowski, Friedrich

Subjects
Astrophysics - Astrophysics of Galaxies
Abstract

We describe a pilot survey conducted with the Mopra 22-m radio telescope in preparation for the Millimeter Astronomy Legacy Team Survey at 90 GHz (MALT90). We identified 182 candidate dense molecular clumps using six different selection criteria and mapped each source simultaneously in 16 different lines near 90 GHz. We present a summary of the data and describe how the results of the pilot survey shaped the design of the larger MALT90 survey. We motivate our selection of target sources for the main survey based on the pilot detection rates and demonstrate the value of mapping in multiple lines simultaneously at high spectral resolution., Comment: Accepted to ApJS. 23 pages and 16 figures. Full resolution version with an appendix showing all the data (12.1 MB) is available at http://malt90.bu.edu/publications/Foster_2011_Malt90Pilot.pdf

Published
2011
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7. The 'Nessie' Nebula: Cluster Formation in a Filamentary Infrared Dark Cloud

Author

Jackson, James M., Finn, Susanna C., Chambers, Edward T., Rathborne, Jill M., and Simon, Robert

Subjects
Astrophysics - Astrophysics of Galaxies
Abstract

The "Nessie" Nebula is a filamentary infrared dark cloud (IRDC) with a large aspect ratio of over 150:1 (1.5 degrees x 0.01 degrees, or 80 pc x 0.5 pc at a kinematic distance of 3.1 kpc). Maps of HNC (1-0) emission, a tracer of dense molecular gas, made with the Australia Telescope National Facility Mopra telescope, show an excellent morphological match to the mid-IR extinction. Moreover, because the molecular line emission from the entire nebula has the same radial velocity to within +/- 3.4 km/s, the nebula is a single, coherent cloud and not the chance alignment of multiple unrelated clouds along the line of sight. The Nessie Nebula contains a number of compact, dense molecular cores which have a characteristic projected spacing of ~ 4.5 pc along the filament. The theory of gravitationally bound gaseous cylinders predicts the existence of such cores, which, due to the "sausage" or "varicose" fluid instability, fragment from the cylinder at a characteristic length scale. If turbulent pressure dominates over thermal pressure in Nessie, then the observed core spacing matches theoretical predictions. We speculate that the formation of high-mass stars and massive star clusters arises from the fragmentation of filamentary IRDCs caused by the "sausage" fluid instability that leads to the formation of massive, dense molecular cores. The filamentary molecular gas clouds often found near high-mass star-forming regions (e.g., Orion, NGC 6334, etc.) may represent a later stage of IRDC evolution., Comment: 5 pages, 2 figures, accepted for publication in The Astrophysical Journal Letters

Published
2010
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8. Multi-spectral and multi-instrument observation of TIDs following the Total Solar Eclipse of August 21, 2017

Author

Aryal, Saurav, Geddes, George, Finn, Susanna C., Mrak, Sebastijan, Galkin, Ivan, Cnossen, Ingrid, Cook, Timothy, Chakrabarti, Supriya, Aryal, Saurav, Geddes, George, Finn, Susanna C., Mrak, Sebastijan, Galkin, Ivan, Cnossen, Ingrid, Cook, Timothy, and Chakrabarti, Supriya

Abstract

Wave‐like structures in the upper atmospheric nightglow brightness were observed on the night of 22 August 2017, approximately 8 hr following a total solar eclipse. These wave‐like perturbations are signatures of atmospheric gravity waves and associated traveling ionospheric disturbances (TIDs). Observations were made in the red line (OI 630.0 nm) and the green line (OI 557.7 nm) from Carbondale, IL, at 2–10 UTC on 22 August 2017. Based on wavelet analyses, the dominant time period in both the red and green lines was around 1.5 hr. Differential total electron content data obtained from Global Positioning System total electron content measurements at Carbondale, IL, and ionospheric parameters from digisonde measurements at Idaho National Laboratory and Millstone Hill showed a similar dominant time period. Based on these observations and their correlation with geomagnetic indices, the TIDs appear to be associated with geomagnetic disturbances. In addition, by modeling the ionosphere‐thermosphere system's response to the eclipse, it was seen that while the eclipse enhanced the O/N2 ratio and electron density (Ne) at 250 km during our observation period, it did not affect the TIDs. Vertical (7 m/s) and meridional (616 m/s) phase velocities of the TIDs were estimated using cross‐correlation analysis between red and green line brightness profiles and spectral analysis of the differential total electron content keogram, respectively. This provides a method to characterize the three‐dimensional wave properties of TIDs.

Published
2019

11. The low-order wavefront sensor for the PICTURE-C mission

Author

Massachusetts Institute of Technology. Department of Aeronautics and Astronautics, Cahoy, Kerri, Marinan, Anne D., Mendillo, Christopher B., Brown, Joshua, Martel, Jason, Howe, Glenn A., Hewawasam, Kuravi, Finn, Susanna C., Cook, Timothy A., Chakrabarti, Supriya, Douglas, Ewan S., Mawet, Dimitri, Guyon, Olivier, Singh, Garima, Lozi, Julien, Massachusetts Institute of Technology. Department of Aeronautics and Astronautics, Cahoy, Kerri, Marinan, Anne D., Mendillo, Christopher B., Brown, Joshua, Martel, Jason, Howe, Glenn A., Hewawasam, Kuravi, Finn, Susanna C., Cook, Timothy A., Chakrabarti, Supriya, Douglas, Ewan S., Mawet, Dimitri, Guyon, Olivier, Singh, Garima, and Lozi, Julien

Abstract

The PICTURE-C mission will fly a 60 cm off-axis unobscured telescope and two high-contrast coronagraphs in successive high-altitude balloon flights with the goal of directly imaging and spectrally characterizing visible scattered light from exozodiacal dust in the interior 1-10 AU of nearby exoplanetary systems. The first flight in 2017 will use a 10[superscript -4] visible nulling coronagraph (previously flown on the PICTURE sounding rocket) and the second flight in 2019 will use a 10[superscript -7] vector vortex coronagraph. A low-order wavefront corrector (LOWC) will be used in both flights to remove time-varying aberrations from the coronagraph wavefront. The LOWC actuator is a 76-channel high-stroke deformable mirror packaged on top of a tip-tilt stage. This paper will detail the selection of a complementary high-speed, low-order wavefront sensor (LOWFS) for the mission. The relative performance and feasibility of several LOWFS designs will be compared including the Shack-Hartmann, Lyot LOWFS, and the curvature sensor. To test the different sensors, a model of the time-varying wavefront is constructed using measured pointing data and inertial dynamics models to simulate optical alignment perturbations and surface deformation in the balloon environment., United States. National Aeronautics and Space Administration (Grant NNX15AG23G S01)

Published
2018

12. End-to-end simulation of high-contrast imaging systems: methods and results for the PICTURE mission family

Author

Massachusetts Institute of Technology. Department of Aeronautics and Astronautics, Cahoy, Kerri, Marinan, Anne D., Douglas, Ewan S., Hewawasam, Kuravi, Mendillo, Christopher B., Cook, Timothy A., Finn, Susanna C., Howe, Glenn A., Kuchner, Marc J., Lewis, Nikole K., Mawet, Dimitri, Chakrabarti, Supriya, Massachusetts Institute of Technology. Department of Aeronautics and Astronautics, Cahoy, Kerri, Marinan, Anne D., Douglas, Ewan S., Hewawasam, Kuravi, Mendillo, Christopher B., Cook, Timothy A., Finn, Susanna C., Howe, Glenn A., Kuchner, Marc J., Lewis, Nikole K., Mawet, Dimitri, and Chakrabarti, Supriya

Abstract

We describe a set of numerical approaches to modeling the performance of space flight high-contrast imaging payloads. Mission design for high-contrast imaging requires numerical wavefront error propagation to ensure accurate component specifications. For constructed instruments, wavelength and angle-dependent throughput and contrast models allow detailed simulations of science observations, allowing mission planners to select the most productive science targets. The PICTURE family of missions seek to quantify the optical brightness of scattered light from extrasolar debris disks via several high-contrast imaging techniques: sounding rocket (the Planet Imaging Concept Testbed Using a Rocket Experiment) and balloon flights of a visible nulling coronagraph, as well as a balloon flight of a vector vortex coronagraph (the Planetary Imaging Concept Testbed Using a Recoverable Experiment-Coronagraph, PICTURE-C). The rocket mission employs an on-axis 0.5m Gregorian telescope, while the balloon flights will share an unobstructed off-axis 0.6m Gregorian. This work details the flexible approach to polychromatic, end-to-end physical optics simulations used for both the balloon vector vortex coronagraph and rocket visible nulling coronagraph missions. We show the preliminary PICTURE-C telescope and vector vortex coronagraph design will achieve 10 -8 contrast without post-processing as limited by realistic optics, but not considering polarization or low-order errors. Simulated science observations of the predicted warm ring around Epsilon Eridani illustrate the performance of both missions.

Published
2018

15. Planetary Imaging Concept Testbed Using a Recoverable Experiment–Coronagraph (PICTURE C)

Author

Massachusetts Institute of Technology. Department of Aeronautics and Astronautics, Cahoy, Kerri, Cook, Timothy, Chakrabarti, Supriya, Douglas, Ewan, Finn, Susanna C., Kuchner, Marc, Lewis, Nikole, Marinan, Anne, Martel, Jason, Mawet, Dimitri, Mazin, Benjamin, Meeker, Seth R., Mendillo, Christopher, Serabyn, Gene, Stuchlik, David, Swain, Mark, Massachusetts Institute of Technology. Department of Aeronautics and Astronautics, Cahoy, Kerri, Cook, Timothy, Chakrabarti, Supriya, Douglas, Ewan, Finn, Susanna C., Kuchner, Marc, Lewis, Nikole, Marinan, Anne, Martel, Jason, Mawet, Dimitri, Mazin, Benjamin, Meeker, Seth R., Mendillo, Christopher, Serabyn, Gene, Stuchlik, David, and Swain, Mark

Abstract

An exoplanet mission based on a high-altitude balloon is a next logical step in humanity’s quest to explore Earthlike planets in Earthlike orbits orbiting Sunlike stars. The mission described here is capable of spectrally imaging debris disks and exozodiacal light around a number of stars spanning a range of infrared excesses, stellar types, and ages. The mission is designed to characterize the background near those stars, to study the disks themselves, and to look for planets in those systems. The background light scattered and emitted from the disk is a key uncertainty in the mission design of any exoplanet direct imaging mission, thus, its characterization is critically important for future imaging of exoplanets., United States. National Aeronautics and Space Administration (Grants NNX14AH46G, NNX15AG23G, and NNX13AD50G), University of Massachusetts at Lowell

Published
2017

19. The low-order wavefront sensor for the PICTURE-C mission

Author

Shaklan, Stuart, Mendillo, Christopher B., Brown, Joshua, Martel, Jason, Howe, Glenn A., Hewasawam, Kuravi, Finn, Susanna C., Cook, Timothy A., Chakrabarti, Supriya, Douglas, Ewan S., Mawet, Dimitri, Guyon, Olivier, Singh, Garima, Lozi, Julien, Cahoy, Kerri L., Marinan, Anne D., and Shaklan, S.

Subjects
Physics, Wavefront, Sounding rocket, business.industry, Wavefront sensor, Deformable mirror, Exoplanet, law.invention, Telescope, Optics, law, Actuator, business, Coronagraph
Abstract

The PICTURE-C mission will fly a 60 cm off-axis unobscured telescope and two high-contrast coronagraphs in successive high-altitude balloon flights with the goal of directly imaging and spectrally characterizing visible scattered light from exozodiacal dust in the interior 1-10 AU of nearby exoplanetary systems. The first flight in 2017 will use a 10^(-4) visible nulling coronagraph (previously flown on the PICTURE sounding rocket) and the second flight in 2019 will use a 10^(-7) vector vortex coronagraph. A low-order wavefront corrector (LOWC) will be used in both flights to remove time-varying aberrations from the coronagraph wavefront. The LOWC actuator is a 76-channel high-stroke deformable mirror packaged on top of a tip-tilt stage. This paper will detail the selection of a complementary high-speed, low-order wavefront sensor (LOWFS) for the mission. The relative performance and feasibility of several LOWFS designs will be compared including the Shack-Hartmann, Lyot LOWFS, and the curvature sensor. To test the different sensors, a model of the time-varying wavefront is constructed using measured pointing data and inertial dynamics models to simulate optical alignment perturbations and surface deformation in the balloon environment.

Published
2015

22. The low-order wavefront sensor for the PICTURE-C mission

Author

Shaklan, S., Shaklan, Stuart, Mendillo, Christopher B., Brown, Joshua, Martel, Jason, Howe, Glenn A., Hewasawam, Kuravi, Finn, Susanna C., Cook, Timothy A., Chakrabarti, Supriya, Douglas, Ewan S., Mawet, Dimitri, Guyon, Olivier, Singh, Garima, Lozi, Julien, Cahoy, Kerri L., Marinan, Anne D., Shaklan, S., Shaklan, Stuart, Mendillo, Christopher B., Brown, Joshua, Martel, Jason, Howe, Glenn A., Hewasawam, Kuravi, Finn, Susanna C., Cook, Timothy A., Chakrabarti, Supriya, Douglas, Ewan S., Mawet, Dimitri, Guyon, Olivier, Singh, Garima, Lozi, Julien, Cahoy, Kerri L., and Marinan, Anne D.

Abstract

The PICTURE-C mission will fly a 60 cm off-axis unobscured telescope and two high-contrast coronagraphs in successive high-altitude balloon flights with the goal of directly imaging and spectrally characterizing visible scattered light from exozodiacal dust in the interior 1-10 AU of nearby exoplanetary systems. The first flight in 2017 will use a 10^(-4) visible nulling coronagraph (previously flown on the PICTURE sounding rocket) and the second flight in 2019 will use a 10^(-7) vector vortex coronagraph. A low-order wavefront corrector (LOWC) will be used in both flights to remove time-varying aberrations from the coronagraph wavefront. The LOWC actuator is a 76-channel high-stroke deformable mirror packaged on top of a tip-tilt stage. This paper will detail the selection of a complementary high-speed, low-order wavefront sensor (LOWFS) for the mission. The relative performance and feasibility of several LOWFS designs will be compared including the Shack-Hartmann, Lyot LOWFS, and the curvature sensor. To test the different sensors, a model of the time-varying wavefront is constructed using measured pointing data and inertial dynamics models to simulate optical alignment perturbations and surface deformation in the balloon environment.

Published
2015

23. End-to-end simulation of high-contrast imaging systems: methods and results for the PICTURE mission family

Author

Shaklan, Stuart, Douglas, Ewan S., Hewawasam, Kuravi, Mendillo, Christopher B., Cahoy, Kerri L., Cook, Timothy A., Finn, Susanna C., Howe, Glenn A., Kuchner, Marc J., Lewis, Nikole K., Marinan, Anne D., Mawet, Dimitri, Chakrabarti, Supriya, Shaklan, Stuart, Douglas, Ewan S., Hewawasam, Kuravi, Mendillo, Christopher B., Cahoy, Kerri L., Cook, Timothy A., Finn, Susanna C., Howe, Glenn A., Kuchner, Marc J., Lewis, Nikole K., Marinan, Anne D., Mawet, Dimitri, and Chakrabarti, Supriya

Abstract

We describe a set of numerical approaches to modeling the performance of space flight high-contrast imaging payloads. Mission design for high-contrast imaging requires numerical wavefront error propagation to ensure accurate component specifications. For constructed instruments, wavelength and angle-dependent throughput and contrast models allow detailed simulations of science observations, allowing mission planners to select the most productive science targets. The PICTURE family of missions seek to quantify the optical brightness of scattered light from extrasolar debris disks via several high-contrast imaging techniques: sounding rocket (the Planet Imaging Concept Testbed Using a Rocket Experiment) and balloon flights of a visible nulling coronagraph, as well as a balloon flight of a vector vortex coronagraph (the Planetary Imaging Concept Testbed Using a Recoverable Experiment - Coronagraph, PICTURE-C). The rocket mission employs an on-axis 0.5m Gregorian telescope, while the balloon flights will share an unobstructed off-axis 0.6m Gregorian. This work details the flexible approach to polychromatic, end-to-end physical optics simulations used for both the balloon vector vortex coronagraph and rocket visible nulling coronagraph missions. We show the preliminary PICTURE-C telescope and vector vortex coronagraph design will achieve 10^(-8) contrast without post-processing as limited by realistic optics, but not considering polarization or low-order errors. Simulated science observations of the predicted warm ring around Epsilon Eridani illustrate the performance of both missions.

Published
2015

28. End-to-end simulation of high-contrast imaging systems: methods and results for the PICTURE mission family

Author

Douglas, Ewan S., additional, Hewawasam, Kuravi, additional, Mendillo, Christopher B., additional, Cahoy, Kerri L., additional, Cook, Timothy A., additional, Finn, Susanna C., additional, Howe, Glenn A., additional, Kuchner, Marc J., additional, Lewis, Nikole K., additional, Marinan, Anne D., additional, Mawet, Dimitri, additional, and Chakrabarti, Supriya, additional

Published
2015
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29. The low-order wavefront sensor for the PICTURE-C mission

Author

Mendillo, Christopher B., additional, Brown, Joshua, additional, Martel, Jason, additional, Howe, Glenn A., additional, Hewawasam, Kuravi, additional, Finn, Susanna C., additional, Cook, Timothy A., additional, Chakrabarti, Supriya, additional, Douglas, Ewan S., additional, Mawet, Dimitri, additional, Guyon, Olivier, additional, Singh, Garima, additional, Lozi, Julien, additional, Cahoy, Kerri L., additional, and Marinan, Anne D., additional

Published
2015
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30. Planetary Imaging Concept Testbed Using a Recoverable Experiment–Coronagraph (PICTURE C)

Author

Cook, Timothy, primary, Cahoy, Kerri, additional, Chakrabarti, Supriya, additional, Douglas, Ewan, additional, Finn, Susanna C., additional, Kuchner, Marc, additional, Lewis, Nikole, additional, Marinan, Anne, additional, Martel, Jason, additional, Mawet, Dimitri, additional, Mazin, Benjamin, additional, Meeker, Seth R., additional, Mendillo, Christopher, additional, Serabyn, Gene, additional, Stuchlik, David, additional, and Swain, Mark, additional

Published
2015
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33. DISTRIBUTED LOW-MASS STAR FORMATION IN THE IRDC G34.43+00.24

Author

Foster, Jonathan B., primary, Arce, Héctor G., additional, Kassis, Marc, additional, Sanhueza, Patricio, additional, Jackson, James M., additional, Finn, Susanna C., additional, Offner, Stella, additional, Sakai, Takeshi, additional, Sakai, Nami, additional, Yamamoto, Satoshi, additional, Guzmán, Andrés E., additional, and Rathborne, Jill M., additional

Published
2014
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37. THE MILLIMETER ASTRONOMY LEGACY TEAM 90 GHz (MALT90) PILOT SURVEY

Author

Foster, Jonathan B., primary, Jackson, James M., additional, Barnes, Peter J., additional, Barris, Elizabeth, additional, Brooks, Kate, additional, Cunningham, Maria, additional, Finn, Susanna C., additional, Fuller, Gary A., additional, Longmore, Steve N., additional, Mascoop, Joshua L., additional, Peretto, Nicolas, additional, Rathborne, Jill, additional, Sanhueza, Patricio, additional, Schuller, Frédéric, additional, and Wyrowski, Friedrich, additional

Published
2011
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44. Molecular line observations of Infrared Dark Clouds in the Galaxy

Author

Finn, Susanna C.

Abstract

Although massive stars play many important roles in the universe, their formation is poorly understood. Recently, a class of interstellar clouds known as Infrared Dark Clouds (IRDCs) has been identified as likely progenitors of massive stars and clusters. These clouds are dense (nH2 > 10^5 cm-3), cold (T < 20 K), have very high column densities (N ~ 10^23 10^25 cm-2), and contain dense clumps and cores. In this dissertation, I present radio observations of a large sample of IRDCs in order to examine their properties and explore the hypothesis that high-mass stars and clusters form in these dense, cold molecular clouds. I determine kinematic distances to a large sample of IRDCs in the inner Galaxy based on CS (2-1) radial velocities. IRDCs are concentrated at specific Galactocentric radii and their distribution appears to trace Milky 'vVay spiral structure. To identify IRDC clumps and determine properties such as mass, size, and chemical evolution, I map a sample of IRDCs in various high density-tracing molecular transitions. The size and mass estimates show that IRDC clumps are comparable in size to more evolved regions of massive star formation. I compare the integrated intensities and linewidths of the molecular emission with a proposed evolutionary sequence of the clumps. The ratio of N2H+ with HNC, HCN, and HCQ+ is a function of evolutionary stage. The linewidths and virial parameters of the clumps show no clear trend with the evolutionary sequence. Finally, I explore the filamentary shape of IRDCs. The "sausage instability," which describes clumps forming in a gas cylinder, is explored as a mechanism for star-forming clumps to collapse in filaments. First, I compare observations of the "Nessie Nebula," an extreme case of a filamentary IRDC, with predictions from the theory of the fluid instability and then expand the sample to other filamentary IRDCs. The observations are consistent with theoretical predictions of clump spacing, clump masses, and linear mass density. Fragmentation of filaments due to the sausage instability might be the dominant mode of star formation in the Universe.

Published
2012

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