D. C. Hines

University of Concepción, Ciudad de Concepcion, Biobío, Chile

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Publications (319)1119.94 Total impact

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    ABSTRACT: The Archival Legacy Investigation of Circumstellar Environments (ALICE) project ((HST/AR program 12652) is currently conducting a comprehensive and consistent reprocessing of HST-NICMOS coronagraphic survey data to search for point sources and disks using advanced PSF subtraction. This project has already been very successful with numerous detections of previously unseen point sources and several debris disks that we are currently following up by multiple avenues. We give an overview of the project including preliminary scientific results with companion candidates, improved images of known disks, and first scattered light image of several disks. ALICE will deliver high-level science products (HLSPs) to the community through the MAST archive at STScI. The goal is to define a HLSP standard that can be applicable to other projects including ground-based (e.g., Gemini Planet Imager), and future space instruments (e.g., JWST). The ALICE pipeline takes full advantage of the LAPLACE PSF library (Schneider et al. 2012) for coronagraphic data, which provides enhanced calibration of NICMOS coronagraphic data and is available from the MAST archive.
    01/2014;
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    ABSTRACT: The Archival Legacy Investigation of Circumstellar Environments (ALICE) project (AR-12652) is currently conducting a comprehensive and consistent reprocessing of HST-NICMOS coronagraphic survey data to search for point sources and disks using advanced PSF subtraction. The KLIP algorithm (Karhunen-Loève Image Projection) was developed for this project, and has proven very effective at processing the hundreds of selected archival images. This project has already been very successful with numerous detections of previously unseen point sources and several resolved debris disks that we are currently following up by multiple avenues. We give an overview of the project including preliminary scientific results with companion candidates and improved images of known disks
    Proceedings of the International Astronomical Union 01/2014;
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    ABSTRACT: We have spatially resolved four new debris disks in scattered light for the first time through the analysis of archival HST NICMOS coronagraphic images. These disks around 12-30-Myr-old main-sequence F or G stars were revealed by reprocessing recalibrated archival images (HST AR program LAPLACE; PI Schneider) with a novel pipeline that improves the subtraction of the PSF (ALICE; Soummer et al. 2012). Three of these disks (HD 30447, HD 35841, and HD 141943) appear to be edge-on, and the fourth (HD 191089) appears to be an asymmetric inclined ring. We describe our modeling efforts so far that take into account all available photometry and resolved images for these sources. We employ the 3D radiative transfer code MCFOST (Pinte et al. 2008), which enables the reconstruction of SEDs and images according to the specified dust composition and disk morphology.
    01/2014;
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    ABSTRACT: The Mid-Infrared Instrument (MIRI) on JWST is equipped with four-quadrant phase mask coronagraphs (4QPM) that will enable cutting-edge science at small inner working angles. The effectiveness of these phase masks relies on accurate target acquisition and positioning at the apex of the four quadrants. In order to optimize MIRI target acquisition as well as coronagraphy operations in general, we have run optical simulations to derive contrast performances of all three MIRI 4QPM for various slew accuracy models. Our simulations include full Fourier propagation from the pupil entrance to MIRI focal plane, including intervening masks, realistic wavefront error, transmission profiles for filters and Germanium coating, as well as detector efficiency. We also include photon noise from the star and background as well as detector noise (readout, pixel-to-pixel variations). Here, we discuss the use of the CCC mechanism and the impact of latent images on science. Our results suggest that operations of MIRI coronagraphs should be modified to allow for cases where the CCC is not to be used. This work will also tie in the implementation of coronagraphy in the JWST Exposure time Calculator. ___________________________
    01/2014;
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    ABSTRACT: The Archival Legacy Investigation of Circumstellar Environments (ALICE) project (HST/AR program 12652; PI Soummer) is currently conducting a comprehensive and consistent reprocessing of HST-NICMOS coronagraphic survey data to search for point sources and disks using advanced PSF subtraction. The Karhunen-Loeve Image Projection (KLIP) algorithm based on principal component analysis was developed for this project. We present the main concept for the pipeline, reduction strategy, and PSF subtraction implementation and performance. The ALICE pipeline was designed to process automatically approximately 400 targets in the NICMOS coronagraphic archive, and to deliver High-Level Science Products (HLSPs) back to the MAST archive at STScI. The HLSPs are defined in collaboration with other similar projects to define a standard format for high-contrast imaging. We present and discuss the ALICE point source candidates detected in the NICMOS archive together with a statistical analysis of the population of background objects.
    01/2014;
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    ABSTRACT: We have obtain WFC3/IR observations of 15 carefully selected stars with the immediate objective of establishing their Absolute Physical Flux (ABF), and an ultimate goal of achieving the sub-1% absolute photometric accuracies required by Dark Energy science with JWST and other facilities. Even with the best data available, the current determination of ABFs is plagued by the reliance on the Vega photometric system, which is known to be problematic primarily due to the fact that Vega is a pole-on rapid rotator with an infrared excess from its circumstellar disk! which makes it difficult to model. Vega is also far too bright for large aperture telescopes. In an effort to remedy these difficulties, teams from the National Institute of Standards (NIST), the University of New Mexico, Johns Hopkins University and STScI have begun to develop a catalog of stars that have spectral energy distributions that are tied directly to NIST (diode) standards with very precisely determined physical characteristics. A key element in this pursuit has been the efforts at STScI to measure the spectra of many of these objects with STIS. We discuss our program to extend this effort into the near-IR which is crucial to reliably extend the SEDs to longer wavelengths, including the mid IR.
    01/2014;
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    ABSTRACT: We present high contrast visible light imaging of the highly unusual circumstellar debris disk around HD 15745 with the Space Telescope Imaging Spectrograph (STIS) instrument on the Hubble Space Telescope (HST). The combination of two coronagraphic wedges and three separate spacecraft orientations provides unprecedented signal-to-noise and inner working angle for this disk. We detect the disk to as close as ~0.4" (26 AU) and as far as 6" (380 AU). We confirm the presence of disk emission that extends further to the west as well as evidence for a second, inner disk. Additionally, HD 15745's motion on the sky is parallel to the extended nebulosity observed, raising the possibility that ISM interactions could play a part in its unusual structure. We investigate the plausibility of this scenario. We acknowledge support from STScI for program (GO12228) and its observations.
    01/2014;
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    ABSTRACT: By reprocessing the NICMOS coronagraphic archive using improved PSF subtraction methods, we have obtained new images of 5 debris disks, all previously unseen using classical PSF subtractions. Three of the disks are edge on and two appear to be ring like, one of which is extremely asymmetric. Their stellar hosts are nearby, young F and G type stars (40-90 pc, 12-30 Myr), including one that is a close analog to the young sun at roughly the age at which terrestrial planets were assembling. This is a 25% increase in the sample of debris disks seen in scattered light. Analysis and modeling of the disk geometries is in process. Given these systems' youth, proximity, and brightness (V = 7.2 to 8.5), these will be superb targets for investigating planet formation, and are perfect targets for studies with GPI, SPHERE and JWST.
    Proceedings of the International Astronomical Union 01/2014;
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    ABSTRACT: We present new Hubble Space Telescope (HST) observations of the HD 181327 debris disk using the Space Telescope Imaging Spectrograph (STIS). Our multi-roll coronagraphic image, combined with new multi-roll image processing techniques, reveals the outer debris ring in its entirety at high SNR. The disk exhibits several significant asymmetries that, at first glance, appear to suggest the presence of a planet. We use new image deprojection methods to constrain the true disk geometry, measure an empirical scattering phase function, and show that the majority of these asymmetries are consistent with scattering and line-of-sight projection effects. One asymmetry, a "post-pericenter glow," appears to be a true density enhancement and we speculate on the origin of this density asymmetry.
    01/2014;
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    ABSTRACT: We have spatially resolved the debris disk around the young 30 Myr) G dwarf HD 202917 through the analysis of archival HST/NICMOS coronagraphic images. The disk was revealed by reprocessing the images (HST/AR program 11279; PI Schneider) through a novel pipeline that improves the subtraction of the coronagraphic PSF (HST/AR program 12652; PI Soummer). The NICMOS scattered light image confirms an earlier, formally unpublished detection of the disk at optical wavelengths from HST/ACS coronagraph images. Together, the images show a highly inclined disk extending ~200 AU from the star. We describe preliminary disk models obtained from available photometry and resolved images of the system and the 3D radiative transfer code MCFOST (Pinte et al. 2008), which enables the reconstruction of SEDs and images according to specified dust composition and disk morphology.
    01/2014;
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    ABSTRACT: We present polarization images of Comet ISON (C/2012 S1) taken with the Hubble Space Telescope (HST) on UTC 2013 May 8 (rh = 3.81 AU, Delta = 4.34 AU), when the phase angle was alpha = 12.16 degrees. This phase angle is approximately centered in the negative polarization branch for cometary dust. The region beyond 1000 km from the nucleus shows a negative polarization amplitude of p% -1.6%. Within 1000 km of the nucleus, the polarization position angle rotates to be approximately perpendicular to the scattering plane, with an amplitude p% +2.5%. Such positive polarization has been observed previously as a characteristic feature of cometary jets, and we show that Comet ISON does indeed harbor a jet-like feature. These HST observations of Comet ISON represent the first visible light, imaging polarimetry with sub-arcsecond spatial resolution of a Nearly Isotropic Comet (NIC) beyond 3.8 AU from the Sun at a small phase angle. The observations provide an early glimpse of the properties of the cometary dust preserved in this Oort-cloud comet.
    The Astrophysical Journal 11/2013; 780(2). · 6.73 Impact Factor
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    ABSTRACT: In this talk we discuss the design, implementation, and reduction of observations of Comet ISON from space using the Spitzer Space Telescope on 13.00 - 13.96 Jun UT and from the ground at Lowell Observatory on Jun 11.16 UT and from APO on 14.13 Jun UT. The comet was at distance rh = 3.34 AU from the Sun, distance ΔSpitzer = 3.29 AU and 17.4o phase from SST, and distance ΔEarth = 4.25 AU and 6.8 - 7.3o phase at the time of observation. Preliminary analyses show ISON's Spitzer coma morphology was relatively compact and simple, with a linear anti-solar dust tail > 3x105 km in length and a 1/p profile gas coma extending > 105 km from the nucleus. Afp values in an 18,200 km radius aperture of 840, 890, and 840 ± 80 cm were found at VRI, and 650 ± 100 cm were found at 3.6 micron. Together, the ground-based and Spitzer photometry imply near-neutral dust scattering from the visual through the infrared. An excess at 4.5 µm due to emission from a neutral gas coma is clearly found both morphologically and photometrically. The gas coma total flux and spatial profile and ISON’s discovery distance imply a coma dominated by the stronger CO_2 line emission at 4.67 μm, but we cannot rule out a preponderance of CO emission at 4.26 μm. No variability in our Spitzer photometry at the 0.03 mag level over 24 hrs was seen. We present our imagery, spectrophotometry, and lightcurves, and discuss the physical implications of these measurements of the comet made well outside the ice line.
    10/2013;
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    ABSTRACT: Massive young stellar objects (YSOs), like low-mass YSOs, are thought to be surrounded by optically thick envelopes and/or discs and are observed to have associated regions that produce polarized light at near-infrared wavelengths. These polarized regions are thought to be lower-density outflows along the polar axes of the YSO envelopes. Using the 0.2 arcsec spatial resolution of the Near-Infrared Camera and Multi-Object Spectrometer on the Hubble Space Telescope we are examining the structure of the envelopes and outflow regions of massive YSOs in star-forming regions within a few kpc of the Sun. Here we report on 2 micron polarimetry of Mon R2-IRS3, S140-IRS1, and AFGL 2591. All three sources contain YSOs with highly-polarized monopolar outflows, with Mon R2-IRS3 containing at least two YSOs in a small cluster. The central stars of all four YSOs are also polarized, with position angles perpendicular to the directions of the outflows. We infer that this polarization is due to scattering and absorption by aligned grains. We have modelled our observations of S140-IRS1 and AFGL 2591 as light scattered and absorbed both by spherical grains and by elongated grains that are aligned by magnetic fields. Models that best reproduce the observations have a substantial toroidal component to the magnetic field in the equatorial plane. Moreover, the toroidal magnetic field in the model that best fits AFGL 2591 extends a large fraction of the height of the model cavity, which is 10^5 au. We conclude that the massive YSOs in this study all show evidence of the presence of a substantial toroidal magnetic field.
    Monthly Notices of the Royal Astronomical Society 09/2013; 435(4). · 5.52 Impact Factor
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    ABSTRACT: CBET 3598 available at Central Bureau for Astronomical Telegrams.
    Central Bureau Electronic Telegrams. 07/2013;
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    ABSTRACT: We present Spitzer InfraRed Spectrograph (IRS) low-resolution spectra of 16 spectroscopically selected post-starburst quasars (PSQs) at z ~ 0.3. The optical spectra of these broad-lined active galactic nuclei (AGNs) simultaneously show spectral signatures of massive intermediate-aged stellar populations making them good candidates for studying the connections between AGNs and their hosts. The resulting spectra show relatively strong polycyclic aromatic hydrocarbon (PAH) emission features at 6.2 and 11.3\micron and a very weak silicate feature, indicative of ongoing star formation and low dust obscuration levels for the AGNs. We find that the mid-infrared composite spectrum of PSQs has spectral properties between ULIRGs and QSOs, suggesting that PSQs are hybrid AGN and starburst systems as also seen in their optical spectra. We also find that PSQs in early-type host galaxies tend to have relatively strong AGN activities, while those in spiral hosts have stronger PAH emission, indicating more star formation.
    The Astrophysical Journal 05/2013; 772(1). · 6.73 Impact Factor
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    The Astrophysical Journal 01/2013; 764(1):111. · 6.73 Impact Factor
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    ABSTRACT: We present results from a coordinated IR-to-X-ray spectral campaign of the QSO IRAS 13349+2438. Optical spectra reveal extreme Eigenvector-1 characteristics, but the H-beta line width argues against a NLS1 classification; we refine z=0.10853 based on [O III]. We estimate a BH mass=10^9 Msun using 2 independent methods (H-beta line width & SED fits). Blue-shifted absorption (-950km/s & -75km/s) is seen for the 1st time in STIS UV spectra from Ly-alpha, NV, & CIV. The higher velocity UV lines are coincident with the lower-ionisation (xi~1.6) X-ray warm absorber lines. A dusty multiple ionization absorber blueshifted by 700-900km/s is required to fit the X-ray data. Theoretical models comparing different ionising SEDs reveal that a UV-inclusive (i.e., the accretion disc) ionising continuum strongly impacts conclusions for the thermodynamic stability of the warm absorber. Specific to IRAS13349, an Xray-UV ionising SED favors a continuous distribution of ionisation states in a smooth flow (this paper), versus discrete clouds in pressure equilibrium (work by others where UV is omitted). Direct dust detections are seen in both the IR: PAH emission at (7.7 & 11.3)micron which may also be blended with forsterite, and (10 & 18)micron silicate emission, and X-rays: iron dust with a dust-to-gas ratio > 90%. We develop a geometrical model whereby the QSO nuclear region is viewed through the upper atmosphere of an obscuring torus. This sight line is obscured by dust that blocks a direct view of the UV/optical emission region but is largely transparent in X-rays since the gas is ionised. In our model, 20% of the intrinsic UV/optical continuum is scattered into our sight line by the far wall of an obscuring torus. An additional 2.4% of the direct light, which likely dominates the UV emission, is Thomson-scattered into our line-of-sight by another off-plane component of highly ionized gas.
    Monthly Notices of the Royal Astronomical Society 01/2013; 430(4). · 5.52 Impact Factor
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    ABSTRACT: We present the results of a comprehensive study on target acquisition with JWST’s Mid-Infrared Instrument (MIRI) four-quadrant phase mask (4QPM) coronagraph using numerical simulations. The adverse effects of the coronagraph and the observatory’s slew accuracy on target acquisition are known to limit our ability to position stars at the center of the coronagraph. Here, we investigate further these two effects and use different scenarios involving single and multiples acquisitions to mitigate them. We also investigate the effects of wavelength, wavefront error, latency, intermediate distances, and detector noise on the different scenarios’ performances. Unlike the intermediate position, we find that latency and noise do not affect TA significantly. We also find that scenarios that require fewer acquisitions yield final pointings with smaller dispersions but larger offsets, and vice versa. At this point, we estimate that a single acquisition at 500 mas from the center of the coronagraph constitutes our best approach for TA with MIRI four-quadrant phase mask coronagraph.
    01/2013;
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    ABSTRACT: AFGL 2591 is a massive young stellar object (YSO) with a luminosity of 2-3 times 10^5 solar luminosities at a distance of 3.33 kpc. It has a single lobe of scattered light to the west, with its east lobe appearing only as a bow shock in molecular hydrogen. The west lobe almost certainly defines the outflow axis, also seen in blue-shifted CO, but the east lobe is completely obscured by the extended dense envelope and massive accretion toroid or disk. We are studying the massive YSOs in the nearest star-forming regions using 2 micron polarimetry with the 0.2" resolution of the Near-Infrared Camera and Multi-Object Spectrometer (NICMOS) on Hubble Space Telescope (HST). Visible and near-infrared polarization of extended sources is caused by light scattered from dust grains, which can be either spherical or non-spherical. Polarization of point sources is caused by differential absorption of the components of light perpendicular and parallel to the major axis of any elongated grains in the light path. It is generally believed that the spin axis of the elongated grains is aligned parallel to the local magnetic field. In AFGL 2591 the extended emission of the outflow more than a few arcsec from the YSO is highly polarized with the polarization position angles indicating that the dust is illuminated by the YSO. The polarization of many of the stars in the field of view and the YSO itself indicates polarization due to absorption by aligned grains oriented in various directions. In particular, the polarization of the extended emission in the central few arcsec is not in agreement with that expected by scattering but is heavily affected by contributions from absorptive polarization. From the absorptive polarization we infer that the grains are aligned in the AFGL 2591 toroid and in the outflow; this is consistent with both a toroidal magnetic field and a field parallel to the outflow. We will discuss additional sources with similar polarization morphology. Support for program 10519 was provided by NASA through a grant from the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555.
    01/2013;
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    ABSTRACT: The Mid-Infrared Instrument (MIRI) on the James Webb Space Telescope (JWST) is expected to spatially resolve many nearby debris disks at mid-infrared wavelengths and detect line emission from circumstellar molecules for the first time. We have simulated (1) direct and coronagraphic images of the debris disk around Vega and (2) spectra of the debris disk around HD 172555 to ellucidate the capabilities of these MIRI modes. We anticipate that MIRI will be able to resolve dust structures indicative of the presence of planets and to detect molecular species indicative of recent giant collisions.
    01/2013;

Publication Stats

2k Citations
1,119.94 Total Impact Points

Institutions

  • 2013
    • University of Concepción
      • Departamento de Astronomía
      Ciudad de Concepcion, Biobío, Chile
  • 2011–2013
    • Space Telescope Science Institute
      Baltimore, Maryland, United States
  • 2012
    • University of Oklahoma
      • Homer L. Dodge Department of Physics and Astronomy
      Norman, Oklahoma, United States
  • 2006–2010
    • The Space Science Institute
      Boulder, Colorado, United States
  • 2009
    • University of Texas at Austin
      • Department of Astronomy
      Austin, Texas, United States
    • University of Illinois, Urbana-Champaign
      • Department of Astronomy
      Urbana, Illinois, United States
  • 1999–2009
    • The University of Arizona
      • • Department of Astronomy
      • • Department of Planetary Sciences
      Tucson, Arizona, United States
  • 2007
    • California State University, Los Angeles
      • Department of Physics and Astronomy
      Los Angeles, California, United States
    • Princeton University
      Princeton, New Jersey, United States
    • University of California, Los Angeles
      • Department of Physics and Astronomy
      Los Angeles, California, United States
  • 2003
    • Arizona State University
      Phoenix, Arizona, United States
  • 1998
    • William Penn University
      Penn Hills, Pennsylvania, United States