SIRTF at the AAS: January 2002
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SIRTF at AAS - Washington D.C., January 2002
The 199th meeting of the American Astronomical Society (AAS) was held in Washington, D.C. on January 6-10, 2002. The following sessions featured SIRTF or the research of SIRTF team members:
SIRTF: A Name in Space; Renaming a NASA Observatory
D. Daou, M. D. Bicay (SIRTF Science Center), M. Kenney (Raytheon ITSS)
The Space InfraRed Telescope Facility (SIRTF) is a space-borne, cryogenically-cooled infrared observatory capable of studying objects ranging from our Solar System to the distant reaches of the Universe. SIRTF is the final element in NASA's Great observatories Program, and an important scientific and technical cornerstone of the new Astronomical Search for Origins Program. Following the tradition of the Great Observatories, NASA intends to rename SIRTF by the time of its launch. In order to promote public interest and awareness, the SIRTF Science Center (SSC), on behalf of the SIRTF Project Office at the Jet Propulsion Laboratory (JPL), has been conducting a worldwide public solicitation for renaming the Observatory. In this poster we present some of the statistics showing the demographics and the plethora of submissions of possible names for SIRTF.
The Guaranteed Time Program with the Multiband Imaging Photometer for SIRTF (MIPS)
G.H. Rieke, E.T. Young, P.A.R. Ade, A. Alonso-Herrero, C. Beichman, H. Dole, E. Egami, C. Engelbracht, T.N. Gautier, K.D. Gordon, T. deGraauw, E.E. Haller, D. Hines, D. Kelly, C. Lada, W. Latter, F.J. Low, K. Misselt, J. Morrison, J. Mould, J. Muzerolle, G.X. Neugebauer, C. Papovich, P.L. Richards, M.J. Rieke, G. Rivlis, J. Stansberry, K. Stapelfeldt, K. Y. Su, M.W. Werner (MIPS Team)
The GTO program for the MIPS team is concentrated in two areas. First, the evolution of planetary debris disks will be traced from their formation at less than one million years old, to the stable disks around old stars. To do so, we will make maps from 3 to 200 microns (in collaboration with the IRAC team) of regions where young stars are forming, to characterize thoroughly the circumstellar excess emission. We will include clusters representing a range of density and age. We will also observe a selection of isolated evolved stars in the MIPS photometric bands at 24, 70, and 160 microns. These observations will catalog the debris disk excesses as a function of stellar mass, age, binarity, and the presence of planetary companions. Second, we will explore the evolution of infrared galaxies and AGNs. This program has two components. In collaboration with both the IRAC and IRS teams, we will map at moderate depth 9 square degrees of sky, and in collaboration with IRAC will make deeper maps of about 2 square degrees. The latter regions have been selected to overlap with very deep xray surveys to aid in identification of AGNs and study of their evolution. We will extend the results of the deep maps by observations of 18 massive galaxy clusters in the redshift range 0.2 < z < 0.4. These clusters will image about 50 square arcmin of the background Universe, raising sources out of the confusion that will limit the sensitivity of the other deep surveys.
Reduction and Calibration of the MIPS 70 and 160 micron Detectors
K.D. Gordon, G.H. Rieke, E.T. Young, P.A.R. Ade, A. Alonso-Herrero, C. Beichman, H. Dole, E. Egami, C. Engelbracht, T.N. Gautier, T. deGraauw, E.E. Haller, D. Hines, D. Kelly, C. Lada, W. Latter, F.J. Low, K. Misselt, J. Morrison, J. Mould, J. Muzerolle, G.X. Neugebauer, C. Papovich, P.L. Richards, M.J. Rieke, G. Rivlis, J. Stansberry, K. Stapelfeldt, K. Y. Su, M.W. Werner (MIPS Team)
The Multiband Imaging Photometer for SIRTF (MIPS) will be one of the three instruments on the Space Infrared Telescope Facility (SIRTF). MIPS will produce images at 24 (128x128 pixels), 70 (32x32 pixels), and 160 (2x20 pixels) microns using Si:As (24 micron) and Ge:Ga (70 and 160 microns) based detectors. The reduction and calibration of the Ge:Ga images present special challenges due to the nature of the bulk photoconductive detectors. The observing strategy of MIPS has been specifically designed to make the reduction and calibration of the Ge:Ga images quite robust and is different from that employed by the Infrared Space Observatory (ISO). The observations are carried out in the fast not the slow time domain, i.e. sources do not stay on the same detector pixels between exposures (3, 4, or 10 seconds). In addition, all data are taken with a high degree of redundancy and a flat field is taken every 2 minutes. The repeatability of this flat field is better than 1%. Worst case source flux repeatability of 10-15% has also been demonstrated. The general outline of the Ge:Ga data reduction and calibration will be presented. This includes continuing characterization work in the laboratory with flight-like arrays which allows for the ongoing study of the behavior of Ge:Ga detectors.
Large Format CCD Mapping of Galactic Globular Clusters
C. J. Grillmair (SIRTF Science Center)
We describe a program to obtain deep, wide-field photometry of Galactic globular clusters with known tidal extensions using the Large Format Camera on the Palomar 5-meter telescope. The aim of this program is to better map the tidal extensions, to examine the stellar makeup of these extensions, and to identify candidates for follow-up spectroscopy and inclusion into the target list for the Galactic structure component of the Space Interferometry Mission. We show first results for the nearby cluster NGC 6218 (M 12), which has been mapped out to more than twice its tidal radius.
The State of Gas in Collisional Galaxies containing AGN
P. Appleton (SSC, Caltech), V. Charmandaris (Cornell), Y. Gao (IPAC, Caltech), F. Combes (Observatoire de Paris), F. Ghigo (NRAO, Green Bank), C. Horellou (Onsala Space Obseravtory), I. F. Mirabel (CEA, Saclay), COLA North Collaboration, COLA South Collaboration
We present ISO, VLA and BIMA observations of the CO and HI content in two collisional Seyfert galaxies-NGC 985 and NGC 1144 (Arp 118). Both systems exhibit signs that their molecular and atomic gas are in a highly transient state. Both appear to have a huge overabundance of molecular gas relative to atomic, only moderate far-IR luminosities, and both show highly disturbed inner disk dynamics. NGC 985, a powerful X-ray source, has many similarities to nearby quasar host galaxies. Its huge molecular reservior consists of two dynamical components, one consisting of descrete SGMCs which may be raining in on the double nucleus, and a second asymmetric structure offset from the center. The descrete CO clouds may be associated with strong intrinsic UV absorption lines seen against the Seyfert nucleus. This along with X-ray evidence of a warm absorber, suggests that the dense CO clouds may be interacting with a hot AGN wind. New HI observations of Arp 118 suggest the possible ongoing transformation of HI to CO in the disk of NGC 1144-perhaps via a collisionally-induced disk-wide shock wave. Future observation of similar AGN in collisional systems will concentrate on the COLA all-sky IRAS-selected galaxy sample. This contains an unbiassed set of galaxies with or without compact radio cores, many of which are in various stages of galaxy-galaxy interaction.
Removing Point Sources from NICMOS Continuum and Emission Line Images of the Galactic Center
S.R. Stolovy (SSC/Caltech), D. Elliott (JPL), D. Makovoz (SSC/Caltech)
The inner few arcseconds of the Galaxy as imaged in NICMOS continuum filters are characterized by a crowded field of many overlapping diffraction-limited PSF's. Images of the ionized gas in Paschen Alpha constructed from the standard technique of taking the difference of two appropriately calibrated 1% filters (F187N-F190N) do show the complex, filamentary structure of the ionized ISM in the central parsec. However, the emission line images are also ''contaminated'' by large positive and residual PSF artifacts. These residuals at the locations of stellar sources are due to astrophysical processes (e.g. Pa alpha and/or Helium emission or absorption in stellar atmospheres, variable extinction) as well as due to the wavelength difference between the line and continuum filters.We desire to study both the continuum and ionized emission close to Sgr A*, which is located only 1-3$''$ from the very bright IRS16 stars. Removal of point source emission from the F190N filter will allow us to recover the underlying distribution of diffuse continuum emission near Sgr A* due to the combined light of faint stars in the Galactic bulge. In addition, even more stringent limits on the near-infrared flux at the position of Sgr A* can be placed. Removal of strong PSF artifacts from the Pa alpha image will allow imaging of the ionized gas with 0.2'' resolution near Sgr A*; our two epochs of Pa alpha images may show high proper motions due to the gravitational potentional of the purported black hole at Sgr A*.
In order to remove all stellar residuals from the NICMOS images, we employ several image processing techniques: First, the PSF is derived from the data directly and by modifying a model (e.g. Tiny Tim) to match the data. We then employ several point source extraction methods, including one developed for the SIRTF pipeline. In order to remove point sources from the emission line images, fluxes and positions derived from the F187N images are correlated with point sources extracted from the F190N ''truth'' image to select only the point sources. Point source removal will be tested using PSF subtraction as well as deconvolution techniques.
A Very Large Bipolar Structure Associated with MWC314: An Evolved Eta Carina?
A. P. Marston, B. McCollum (SSC, Caltech)
Be and B[e] emission-line stars have emission-lines that are believed to arise from a circumstellar disk. The position of these stars in the Hertzsprung-Russell diagram provides a puzzle. Are these young stars evolving towards the main sequence or are they evolved massive stars either evolving away from the main sequence or back towards it? In an effort to answer this question we have initiated an emission-line imaging survey of the circumstellar environments of Be and B[e] stars. Our intention is to look for structures indicative of prior stellar evolution and/or structures providing further evidence of the existence of circumstellar disks. In our initial set of observations of the environments of the B[e] star MWC314, we show it to have a very large (>15\prime) bipolar structure associated with it. Such a structure is immediately indicative of an outflow restricted by the presence of a circumstellar disk. The bipolar structure is consistent with radio recombination lines observed at 57 km/s. This places the object at a distance of approximately 3kpc, based on galactic rotation in this portion of the sky. The total length of the bipolar is therefore over 13pc. We suggest that MWC314 is an evolved massive star with the tentative suggestion that it has evolved from a prior Luminous Blue Variable phase. Together with its high luminosity, this would indicate that MWC314 is the kind of object that Eta Carina could evolve into.
The Atomic and Molecular Gas Around Evolved Stars
D. Fong, M. Meixner, E.C. Sutton (Univ. of Illinois), A. Castro-Carrizo, V. Bujarrabal (Observatorio Astronómico Nacional, Spain), W.B. Latter (Caltech, SIRTF Science Center), A.G.G.M. Tielens (Kapteyn Astronomical Institute, The Netherlands), D.M. Kelly (Univ. of Arizona, Steward Obs.), W.J. Welch (Univ. of California)
We present ISO LWS and SWS observations of far-infrared atomic fine structure lines of 24 evolved stars including asymptotic giant branch (AGB) stars, proto-planetary nebulae (PPNe) and planetary nebulae (PNe). The spectra include grating and Fabry-Perot measurements of the line emission from [OI], [CII], [SiI], [SiII], [SI], [FeI], [FeII], [NeII] and [NII] which trace the low-excitation atomic gas. Atomic emission was only found in those sources where Teff \geq 10000 K. Above this cutoff, the number of detectable lines and the intensity of the line emission increase as Teff increases. These trends suggest that the atomic lines originate from photodissociation regions (PDRs). In general, the kinematics of the atomic gas, derived from line fits to the Fabry-Perot data, are comparable to the molecular expansion velocities. These kinematics are expected for atomic cooling lines associated with circumstellar PDRs. A new PDR code which properly treats enhanced carbon abundances was used to model the observations. The predicted line intensities agree reasonably well with the observations. Shock models, however, do not compare well with the observed line intensities. PDR mass estimates ranging from ~0.01-0.2 M\odot were derived from the [CII] 158 \mum line emission. The atomic gas only occupies a small fraction of the total mass for young planetary nebulae, but grows significantly as they evolve. To compliment our atomic gas study we also present CO J=1-0 observations of 7 objects in our ISO sample to investigate the evolution of the molecular envelope. By combining data from the Berkeley-Illinois-Maryland-Association (BIMA) Millimeter Array and the NRAO 12m, we have constructed full synthesis data cubes for MIRA, IRC +10216, IRAS 17436+5003 (HD 161796), AFGL 2688, IRAS 22272+5435 (HD 235858), AFGL 2343 (IRAS 19114+0002) and NGC 7027. The history of the circumstellar gas is imprinted on the circumstellar envelope itself, such as the record of its molecular mass loss, and its interaction with fast winds and dissociating/ionizing photons. By imaging the morphology and the kinematic structure, we can model the mass loss history and piece together how fast winds, shocks and photodissociation/photoionization have transformed these envelopes. Our overall analysis shows that photodissociation and not shocks dominates the evolution of the circumstellar envelope by transforming the initially molecular asymptotic giant branch envelopes into the atomic gas found in proto-planetary and planetary nebulae.This work has been partially supported by NASA JPL 961504, NASA NAG 5-3350, NSF AST 99-81363 and NSF AST 97-33697.
