IRAFA Workshop Poster Abstracts

Mario van den Ancker, ISO spectroscopy of protoplanetary disks around Herbig Ae/Be stars

   I present an analysis of infrared solid state features present in a sample of 46 Herbig AE/Be stars observed spectroscopically with the Infrared Space Observatory (ISO). The presence, strength and shape of solid-state emission bands was compared to other indicators of circumstellar material, such as optical emission lines, optical brightness variations and sub-mm continuum fluxes. We conclude that the infrared spectra of the A-type stars in our sample are dominated by thermal emission from a passively heated circumstellar disk. We also present some evidence for grain growth and mineralogical processing of material in these disks.

Tereasa Brainerd, Multiple Weak Lensing Events in the HDF-North

   We compute the theoretical shear field due to weak galaxy-galaxy lensing in the region of the HDF-North. Using the ~ 600 publicly-available spectroscopic redshifts in the HDF-North and the flanking fields, as well as the rest frame blue luminosities of these galaxies, we investigate the occurrences of "multiple lensing" for distant galaxies in the HDF-North. We take the deprojected circular velocity of the halo of an L* galaxy to be 200 km/s, with a typical radius of s* = 100h^-1 kpc, and we use common scaling relations to determine the circular velocities and radii of the halos of galaxies with luminosities L ¹ L*. If we define a lensing event to be a deflection in which g ³ 0.005, then for 0.75 £ z_source £ 1.0, the probability of multiple lensing is of order 50%. The probability increases to ³ 90% for z_source ³ 1.5. Lastly, we show that if multiple weak lensing events are ignored in the analysis of the galaxy-galaxy lensing signal, the inferred circular velocity for the halos of L* galaxies is of order 60 km/s too large.

Dan Clemens, Mimir: A Near-Infrared Wide-Field Imaging Spectrometer and Polarimeter

   The Mimir NIR multi-function instrument is being jointly developed by Boston University and Lowell Observatory personnel. When deployed to the 1.8m Perkins telescope in Flagstaff, Arizona later this year, it will become the first facility-class instrument, supporting a wide range of planetary, galactic, and extragalactic science. Mimir utilizes a 1024x1024 InSb ALADDIN III detector, refractive optics, grism-based spectroscopy, and Wollaston prism polarimetry. Two cameras provide either a 10x10 arcmin FOV at 0.6 arcsec per pixel or 3x3 arcmin at 0.18 arcsec per pixel. One half wave plate and three 10-position filter wheels provide plenty of space for filters, grisms, and polarimetry elements. Funding for this project has been provided by NASA, NSF, and the W. M. Keck Foundation.

J. M. Jackson, I. Gatley, T. M. Bania, E. Tollestrup, and E. W. Dunham, The Antarctic Infrared Observatory AIRO

   We aim to exploit the unique conditions in Antarctica by establishing a new permanent national facility, the Antarctic Infrared Observatory. AIRO will operate a 1.8-meter telescope optimized for wide-field imaging, queue observing,and standardized data processing in the largely unexplored 3 - 5 micron waveband. Dome C or the South Pole are both potential sites. The prototype user-facility instrument Abu/SPIREX demonstrated that very sensitive imaging in the thermal infrared can be routinely performed in the Antarctic. Our experiencewith Abu/SPIREX tells us that infrared astronomy in the Antarctic should be further developed. We therefore plan to establish AIRO and construct a larger, more sensitive, automated 3 - 5 micron thermal infrared telescope as its first instrument. AIRO will be a true national observatory open to the communityvia a TAC run by NOAO. The deployment plan calls for 2 years of manufacture, 2 years of testing and system integration at Lowell Observatory's Anderson Mesa site, and finally deployment to Antarctica in the fifth year. Future upgrades will include instruments for wide-field imaging in the mid-infrared, spectroscopy, and polarimetry.
   The Center for Astrophysical Research in Antarctica's research and education programs are supported in part by the National Science Foundation under a cooperative agreement, grant number NSF OPP 89-20223.

Sungeun Kim, The Origin of Far-Infrared CII Emission in the Large Magellanic Cloud

  We compare the distribution of HI 21 cm, HII 6563Å, and CII 157.7 µm line emission over the entire Large Magellanic Cloud (LMC). Bright CII emission is associated with HII regions and their surroundings, with a good correlation between CII and Ha filaments. Faint CII emission is also detected in regions with no HII emission. We found a reasonably good correlation between the extended CII emission and HI emission. Using the slope of the CII versus HI correlation in regions with low Ha brightness,

4p I_CII/N_HI = 6.0 ± 3.0 ´ 10^-26 erg×s^-1 H-atom^-1,

K.E. Kraemer, G.C. Sloan, and S.P. Price, Classification of All 2.4-45.2 µm Spectra from the ISO Short Wavelength Spectrometer

   We present a a comprehensive system of spectral classification for spectra from the ISO Short Wavelength Spectrometer (SWS). Almost 1250 spectra from over 900 objects were observed in full-grating-scan mode (SWS01, 2.4-45.2 µm) with the SWS. Sources are assigned to groups based on the overall shape of the spectral energy distribution (SED). The groups include (1) naked stars, (2) dusty stars, (3) warm dust shells, (4) cool dust shells, (5) very red sources such as H II regions and planetary nebulae, and (6) sources with emission lines but no detected continuum. These groups are further divided into subgroups based on spectral features that shape the SED such as carbon-rich dust emission, silicate absorption, ice absorption, and fine-structure or recombination lines. Most sources which had spectral classifications from the IRAS Low Resolution Spectrometer are in similar categories based on their SWS spectra. Where discrepancies occur, e.g., in carbon - vs. oxygen-rich, the SWS classification should take precedence because of the larger bandpass, higher resolution (spectral and angular), and greater sensitivity of SWS. Caveats regarding the data and data reduction, and biases intrinsic to the database, are discussed. Systematics in the SWS database should not affect the classifications by more than a subgroup in most cases.

R. Simon, J. M. Jackson, T. M. Bania, D. P. Clemens, M. Kolpak, K. McQuinn, M. H. Heyer, The BU-FCRAO Milky Way Galactic Ring Survey

   The Milky Way Galactic Ring Survey (GRS) is a collaboration between Boston University and Five College Radio Astronomy Observatory designed to probe the star-forming and quiescent molecular gas comprising the 5 kpc Galactic Ring. The survey exploits the multi-pixel array receiver SEQUOIA on the FCRAO 14 m telescope, obtaining low noise, high angular resolution (46") and spectral resolution 13CO (1-0) and CS (2-1) spectra on a 22" grid. Over the past three years, the GRS has obtained over 500,000 spectra and surveyed more than 20 square degrees of the first Galactic quadrant. The structures of the molecular clouds sampled are significantly more complex than seen in previous surveys. We are correlating infrared sources with the GRS maps to establish associations and radial velocities, and thereby deduce kinematic distances. The near-far kinematic distance ambiguity is resolved for many molecular clouds based on positional and spectral association with the presence or absence of HI self-absorption, using data from the BU-Arecibo Observatory Galactic HI survey. In many cases, near distances are confirmed by optical and infrared extinction against the Galactic background.
   The Galactic Ring Survey acknowledges support by the NSF via grants AST-9800334 and AST-0098562. The BU-Arecibo survey was supported by NSF grant AST-8511844.

R. Simon, J. M. Jackson, T. M. Bania, D. P. Clemens, M. H. Heyer, M. P. Egan, S. D. Price, Infrared Dark Clouds in the BU-FCRAO Milky Way Galactic Ring Survey

   Recent high resolution, high sensitivity mid-infrared surveys of the Galactic plane with the Midcourse Space Experiment (MSX) and Infrared Space Observatory satellites have revealed a large population of clouds seen in silhouette against the Galactic background. The origin and nature of these IR dark clouds are stillpoorly understood. Most of these objects are concentrated in the first and fourth Galactic quadrant and at low Galactic latitudes where the infrared background is highest. Recent studies of some of these clouds show that they aredense, cold, and have very high column densities. Combined with the absence of embedded mid- to far-infrared sources, this suggests that the clouds are cores before or in the earliest stages of star-formation (protostellar class 0 or earlier).
   Preliminary results for some of the IR dark clouds identified from the MSX data set in the region sampled by the GRS are: (1) For all dark clouds we studied, mid-infrared absorption morphologically matches strong molecular line emission in velocity channels of 13CO. (2) Requiring a significant background to absorb against, IR dark clouds must be located at the near kinematic distance. The 13CO velocities then can be used to solve the kinematic distance ambiguity and to assign unique distances to the IR dark clouds. (3) Our observations confirm high densities, high column densities, and relatively high masses, typically a few thousand solar masses. 12CO spectra towards the IR dark clouds are saturated and show signs of self-absorption. Line ratios of 13CO/C18O even suggest
moderate to high opticities in the 13CO line towards the cores. (4) The dark clouds sampled by the GRS are condensations within Giant Molecular Clouds and are not isolated objects.
   The Galactic Ring Survey acknowledges support by the NSF via grants AST-9800334 and AST-0098562.

Marco Ferrari Toniolo, Five (and maybe more) good reasons to support the IRAIT project

A schematic presentation, underlining the importance of supporting the installation at Dome C of a small Telescope and Prototype Instrumentation, covering the range 2µm to 20µm, as proposed by the IRAIT Project.

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Last updated March 5, 2002