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Event
Presentations
Visitors
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Listing of Poster Abstracts
| PACS: The First IFS in Space |
| Katrina Exter (KU Leuven) |
| PACS is the the first integral field spectrograph on a space mission (Herschel), and also the first operating at FIR wavelengths. In this poster I will present an overview of the instrument and how this impacts on the science you can do with PACS. I will also discuss some of the issues that have arisen since the launch of Herschel, technically interesting problems that were not foreseen, and explain how we have overcome them. |
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| High Resolution HST Spectroscopy of AGN Outflows in Mrk 573 and Plans for Gemini NIFS Observations |
| Travis Fischer (Georgia State University) |
| We present a study of the outflowing ionized gas in the resolved
narrow-line region of the Seyfert 2 galaxy Mrk 573, and its interaction with an inner dust/gas disk, as part of an ongoing program to determine the geometries of the outflows and fueling flows in nearby AGN. Using spectroscopic and imaging information from the HST Space Telescope Imaging Spectrograph and Wide Field Planetary Camera 2, we determined the fundamental geometry of the outflow and inner disk, via two modeling programs used to recreate the morphology of these regions. We found that the bicone of ionizing radiation from the AGN intersects with the inner disk, illuminating a section of the disk including inner segments of spiral arms, fully seen through structure mapping, which appear to be outflowing and expanding. However, high radial velocities of the gas at distances > 2" (~700 pc) have led to complications when fitting our simple outflow model. We suggest that these could be due high velocity rotation or in situ acceleration, via radiation pressure or entrainment in highly ionized winds, of clouds off the original fueling flow. With our recent time awarded on Gemini North using the Near-Infrared Integral Field Spectrometer (NIFS), we intend to obtain a full kinematic map of the ionized and molecular gas in the circumnuclear region of Mrk 573 to distinguish between these possibilities and illustrate the potential of IFU observations for determining the properties of feeding and feedback in AGN.
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| Turbulent Star Formation |
| Andy Green (Swinburne University) |
| Combining results from various IFU surveys from local dwarf galaxies to z~3.5 and super starburst galaxies, including our own volume limited SDSS sample, we find a strong relationship between star formation rate and velocity dispersion or turbulence of star forming regions. This poster will outline possible explanations for and implications of this relationship.
(based on results accepted for publication in Nature) |
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| The SWIFT Data Reduction Package: Reducing IFU Data in IRAF With a Single Interpolation |
| Ryan Houghton (University of Oxford (Astrophysics)) |
| SWIFT is an AO-assisted, slicer-based IFS operating in the I and z bands, mounted at the Cassegrain focus of the 200-inch Hale telescope at Palomar. The latest data reduction software for SWIFT is written for IRAF.
The use of standard IRAF packages over more instrument specific home-grown software has significant advantages: IRAF routines are well tested, mostly bug free and use well understood and accepted algorithms. Furthermore, distribution of a pipeline based on IRAF is considerably easier (for both user and developer) than instrument-specific software based on less common libraries, often still under development. But can IRAF keep up with the demands of IFU data reduction?
One of the key goals in reducing IFU data should be to minimise the number of interpolations required to transform the raw 2D data into a regular 3D data cube. Reduction of IFU data from some instruments can use up to 7 interpolations, which has many disadvantages: neighbouring pixels become strongly correlated, impairing the noise statistics of the data; overall resolution is degraded via smoothing; undetected bad pixels become blended with good data. We use standard IRAF packages to reduce SWIFT IFU data, but combine all necessary interpolation stages into one and thus use a single interpolation to create a calibrated 3D data cube. |
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| Modelling Blue Compact Dwarf Galaxies with MOCASSIN |
| Oskar Karczewski (University College London) |
| We present results of a study of the blue compact dwarf (BCD) galaxy NGC 4449 employing the fully three-dimensional Monte Carlo photoionisation and dust radiative transfer code MOCASSIN (Ercolano et al. 2003, 2005, 2008). Given an input radiation field from the stellar population synthesis code Starburst99 (Leitherer et al. 1999) MOCASSIN simultaneously solves the radiative transfer for coexisting gas and dust phases, and calculates the ionisation, electron temperature and grain temperature at each grid point, as well as the resulting gas and dust emission spectra. By a suitable choice of the input parameters the predicted spectral energy distribution (SED) and the predicted emission line intensities can be matched to observations. From a best-fit model successfully reproducing the observed spectral characteristics of NGC 4449 we deduce the ages of the underlying stellar populations, dust characteristics and the dust mass in the galaxy.
Our goal is apply these spatially resolved radiative transfer modelling techniques to the analysis of integral field unit (IFU) spectroscopy being acquired for a number of blue compact dwarf galaxies with the Photodetector Array Camera and Spectrometer (PACS) on-board the Herschel Space Observatory (HSO), together with planned ground-based optical IFU spectroscopic measurements. These data will provide detailed spatially resolved measurements of electron temperature and densities, elemental abundances and reddenings, enabling a more precise 3D modelling of the properties of the BCD sample. |
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| SWIFT and Multi-Wavelength Observations of the Eagle Galaxy at z=0.8
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| Susan Kassin (Oxford Astrophysics) |
| This poster presents Short Wavelength Integral Field Spectrograph (SWIFT) (Thatte et al. 2006) observations of DEEP2 1301-91-95, the "Eagle Galaxy," at z=0.8. Velocity maps are presented and interpreted along with multi-wavelength data from the AEGIS Survey. The Eagle was chosen to be observed primarily because of its bright and extended line emission and secondarily because it is an example of a dispersion-dominated galaxy as determined from a single slit spectrum. It is a unique object: dispersion-dominated throughout, highly star-forming in extended filamentary structures, and with a low dust
content and metallicity for its size. |
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| Metal-Poor Wolf-Rayet SDSS Galaxies: Integral Field Spectroscopy With PMAS |
| Carolina Kehrig (Astrophysikalisches Institut Potsdam) |
| Our main goal is to take advantage of the SDSS catalogue of Wolf-Rayet (WR) galaxies (Brinchmann et al. 2008) to analyze the properties of these objects using integral field spectroscopy. WR galaxies are star-forming systems whose spectra show WR features (e.g blue bump around 4600-4750 A) indicating the presence of WR stars. We will focus on metal-poor objects [12+log(O/H) < 8.0] in order to explore the disagreements between observations and model predictions for WR features in this metallicity regime. We used the IFU Potsdam Multi-Aperture Spectrophotometer (PMAS), at the 3.5m telescope at Calar Alto Observatory (Spain), to observe six low metallicity WR galaxies covering the optical spectral range (~ 3700 - 7000 A). In this workshop we will present pure emission line, emission line ratio and continuum maps that characterize the spatial distribution of the WR stellar population and the warm ISM properties (electron density and temperature, chemical abundance, ionization structure, etc) in our sample of galaxies. |
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| The Interplay Between Ionized Gas and Massive Stars in the HII Galaxy IIZw70 Using Integral Field Spectroscopy |
| Carolina Kehrig (Astrophysikalisches Institut Potsdam) |
| We performed an integral field spectroscopic study for the HII galaxy IIZw70 to investigate the interplay between its ionized interstellar medium (ISM) and the massive star formation.Observations were taken in the optical spectral range (3700 - 6800 A) with the Potsdam Multi-Aperture Spectrophotometer (PMAS) attached to the 3.5 m telescope at Calar Alto Observatory. We created maps of spatially distributed emission-lines, continuum emission, and properties of the ionized ISM (ionization structure indicators, physical-chemical conditions, dust extinction, kinematics). We investigated the relation of these properties to the spatial distribution and evolutionary stage of the massive stars. For the first time we have detected Wolf-Rayet (WR) stars in this galaxy. The peak of the ionized gas emission coincides with both the location of the maximum of the stellar continuum emission and the WR bump. The region of the galaxy with lower dust extinction corresponds to the region that shows the lowest values of velocity dispersion and radial velocity. The overall picture suggests that the ISM of this region is being disrupted via photoionization and stellar winds, leading to a spatial decoupling between gas+stars and dust clouds. The bulk of dust appears to be located at the boundaries of the region occupied by the probable ionizing cluster. We also found that this region is associated to the nebular emission in HeII4686 and to the intensity maximum of most emission lines. This indicates that the hard ionizing radiation responsible for the HeII4686 nebular emission can be related to the youngest stars. |
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| The Star-Forming Dwarf Galaxy Population in the Local Universe and
Beyond: The First 3D Spectroscopic Study of a Large Sample of Blue Compact Dwarf Galaxies |
| Carolina Kehrig (Astrophysikalisches Institut Potsdam) |
| In spite of the great effort that has been done during the last two
decades on the investigations on Blue Compact Dwarf (BCD) Galaxies, we are still far from understand fundamental issues as the mechanism responsible for the ignition of the actual starburst, the evolutionary status of these galaxies or their star forming histories. Integral Field Spectroscopy is the ideal observational
technique to explore such issues: each single exposure contains both spatial and spectral information in a large
area of the galaxy, so just in one shot we collect information for all the star forming regions as well as for
the low surface brightness stellar component of the galaxies. Besides, the kinematical information also allow us to investigate what mechanisms ignite the star-formation in BCDs. This poster presents results on the
first comprehensive analysis of a large
sample of BCDs by means of Integral Field Spectroscopy. This
dataset allow us to gain insights into the most crucial unanswered
questions in BCDs research. Besides, this analysis will form an essential reference to understand and interpret
high-z star-forming galaxies. |
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| A IFS Study of the Giant HII Region NGC588 |
| Ana Monreal-Ibero (Instituto de Astrofisica de Andalucía) |
| Most of today stars were formed in high intensity episodes about 7−10 Gyr ago. However, at these redshifts both resolution and dimming effects make difficult to study in detail the interaction of the gas, dust and newly formed stars. Giant H II regions in very nearby galaxies constitute their best local counterpart to address such a study. Here, we present an analysis of NGC 588, a GHIIR in M33, based on optical Integral Field Spectroscopy data obtained with PMAS together with IR images from Spitzer. In particular, we will show that the extinction distribution display a complex structure with three maxima that correlate well with those for the dust emission at 24 μm and 8 μm. Moreover, the absorbed Hβ luminosity map reproduces the structure observed in the 24 μm image from Spitzer supporting the use of this band as a good tracer of recent star formation. Also, we will put special attention in identifying the areas of the regions responsible for the line ratios measured in the integrated spectrum. We will see that spectrum of GHIIR in galaxies at distances >25 Mpc can be dominated by the ionization conditions in their low surface brightness (i.e. L(Hβ)<25%L(Hβ)max) areas as it is seen from the comparison of the integrated and local values derived for the line ratios involved in the BPT diagrams as well as for those tracing the ionization parameter and metallicity. |
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| Image Reconstruction of the JWST-MIRI IFU Spectrometer Data
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| Jane Morrison (University of Arizona - Steward Observatory) |
| The Mid Infrared Instrument of the James Webb Space Telescope contains a spectrometer with four integral field units(IFUs). The optical distortion in the image slicing and the dispersive optics in this instrument lead to non-uniform sampling of the spatial and spectral information on the detector plane.
We have created a software tool set, to translate the detector data into the three-dimensional data cube representing the two spatial and the spectral sky dimension. This tools set has three parts: 1) the creation of the necessary calibration files to translate the detector data to the spectral sky cube; 2) the reconstruction software which uses the calibration files to create the sky cube; and 3) the visualization and analysis software to examine the sky cube and how it relates back to the detector data.
The calibration files contain the transformation maps that derive for each pixel corner the corresponding wavelength, along-slice position, as well as the slice number. The source of the calibration maps depends on the phase of the project. During the Verification Model testing the ray-tracing software ZEMAX was used derive the calibration data. One of the goals of Flight Model test campaign is
to astrometrically characterize the MIRI spectrometer. Therefore during the Flight Model test campaign the calibration files will be determined from the data.
With our tool set we will be able to analyze the image quality, PSF characterization, and test the astrometric calibration of the spectrometer.
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| WiFeS GOALS: Metallicity, Shocks, and More in Nearby U/LIRGS |
| Jeffrey Rich (University of Hawaii) |
| Ultraluminous/Luminous Infrared Galaxies (U/LIRGs) are an excellent laboratory for investigating galaxy formation and evolution. They are complex systems, running the gamut of galaxy nuclear types and covering a sequence of massive mergers from isolated starburst galaxies to completely coalesced mergers with post-starburst populations and strong AGN. The detailed relationship between star formation, AGN, the ISM environment, gas motions, and merger evolution in LIRGs remains poorly understood.
In this talk I will present the first results from a survey of nearby U/LIRGs from the GOALS sample. Our data come from WiFeS, a new IFU on the ANU 2.3m at Siding Spring Observatory. I will show our work on abundance maps and gradients in merging systems as well as our investigation of galactic winds and and extended emission power sources and a brief foray into stellar populations. Our work has shown that IFU data is absolutely necessary for understanding key features of U/LIRGs and the phenomena associated with them. |
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| PMAS Optical Integral Field Spectroscopy of Luminous Infrared Galaxies |
| Javier Rodriguez (CSIC/STScI) |
| There are relatively few studies of large samples of local LIRGs using
integral field spectroscopy (IFS). As part of a larger, ongoing
project, we present optical (~3800-7200A) IFS data taken with the
Potsdam Multi-Aperture Spectrophotometer (PMAS), on Calar Alto, Spain,
of the central few kiloparsecs of eleven LIRGs (Alonso Herrero et
al. 2009,A&A,506,1541 and Alonso Herrero et al. 2010
arXiv1006.2219A). The PMAS observations were complemented with
existing HST/NICMOS Pa-alpha imaging. The optical continua of selected
regions are well fitted with combinations of evolved (0.7-10Gyr) and
ionizing (1-20Myr) stellar populations. The latter is more obscured
than the evolved population, and has visual extinctions in good
agreement with those obtained from the Balmer decrement. Except for
NGC 7771, we found no evidence for an important contribution to the
optical light from an intermediate-aged stellar population
(100-500Myr). Even after correcting for stellar absorption, most of
the extended regions of the galaxies with low equivalent widths of
Halpha in emission still show enhanced [NII]6584/Ha and
[SII]6717,6731/Ha ratios. These ratios are likely to be produced by
photoionization in HII regions and diffuse emission. These regions of
enhanced line ratios are coincident with low surface brightness HII
regions. The fraction of diffuse emission in LIRGs varies from galaxy
to galaxy, and it is less than 60% as found in other starburst
galaxies. The Halpha velocity fields over the central few kpc are
generally consistent, at least to first order, with rotational
motions. The velocity fields of most LIRGs are similar to those of
disk galaxies, in contrast to the highly perturbed fields of most
local, strongly interacting ULIRGs. The peak of the Halpha velocity
dispersion coincides with the position of the nucleus and is likely to
be tracing mass. Follow up projects will also be presented during the talk.
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