329 Poster Session
329.01
Photometric Properties of Face-on Isolated Spiral Galaxies
Alexander Bahr1, P. Epstein1, A. Durbala1
1University of Wisconsin-Stevens Point.
8:00 AM - 7:00 PM
America Ballroom Foyer
We want to quantify the relative role of nature versus nurture in defining the observed properties of galaxies. In simpler terms we would like to disentangle the ``genetic’’ and the environmental influences in shaping the morphology of galaxies. In order to do that one needs to firstly define a zero-order baseline, i.e., a sample of galaxies that have been minimally perturbed by neighbors in the last few billion years of their existence. Such a sample has been produced and refined in different stages in the context of the AMIGA international project (www.iaa.es/AMIGA.html). The recent catalogue ``The All-Sky Catalog of Isolated Galaxies Selected from 2MASS’’ (Karachentseva, V. E. et al. 2010) allows us to complete and enrich the initial sample constructed within AMIGA with new objects, thus enhancing the statistical relevance of our study. Our focus is to define a subset of isolated disk spiral galaxies. We constrain the sample selection by: 1) orientation, restricting to almost face-on galaxies and 2) availability of good photometric images in SDSS. The goal is to ``dissect’’ (decompose) these galaxies in major components (disk, bulge, bars, etc.) and to study the properties of the components in a statistical context. Having a reasonable representation of all morphological types, we aim to test the bimodality of bulges and bars. We present a progress report of our work.
329.02
BUDDA Decomposition of Isolated Face-on Spiral Galaxies
Paulette Epstein1, A. Bahr1, A. Durbala1
1University of Wisconsin-Stevens Point.
8:00 AM - 7:00 PM
America Ballroom Foyer
We perform Bulge/Disk/Bar photometric decomposition of face-on isolated spiral galaxies employing the BUDDA code http://www.sc.eso.org/~dgadotti/budda.html. We present the typical procedure of deconstructing the 2D light distribution on SDSS i-band images for barred and non-barred galaxies. Our working sample of galaxies is extracted from ``The All-Sky Catalog of Isolated Galaxies Selected from 2MASS’’ (Karachentseva, V. E. et al. 2010) and complements the AMIGA sample (www.iaa.es/AMIGA.html).
329.03
Mapping The Spatial Distribution Of Dust Extinction In Ngc 4038/39 Using Optical - Mir Filters
Mukund P. Wosti1, P. B. Eskridge1
1Minnesota State University.
8:00 AM - 7:00 PM
America Ballroom Foyer
MAPPING THE SPATIAL DISTRIBUTION OF DUST EXTINCTION IN NGC 4038/39 USING OPTICAL - MIR FILTERS
Mukund P. Wosti , Paul B. Eskridge
Abstract:
We use a pixel based method to estimate and map the two dimensional distribution of dust extinction in the nearby interacting galaxy pair NGC 4038/39 (The Antennae).The method, pioneered by Tamura et al. (2009 AJ 138, 1634; 2010 AJ 139, 2557), compares the observed V - band to Spitzer 3.6 µm flux ratio with flux ratios from models of simple stellar populations. Our longer wavelength baseline allows us to improve on the earlier results of Kassin et al. (2003 AJ 126, 1276). Optical and NIR images of NGC 4038 obtained in Ohio State University galaxy survey, GALEX FUV/NUV, and Spitzer/IRAC 3.6, 4.5, 5.8, 8.0 images will be studied through pixel Color - Magnitude Diagrams (pCMDs) and pixel Color - Color Diagrams (pCCDs).
We gratefully acknowledge financial support from the College of Science, Engineering and Technology, and from the College of Graduate Studies at Minnesota State University, Mankato.
329.04
Global Chemical Compositions Of Spiral Galaxies
Stuart Dack1, M. McCall1
1York University, Canada.
8:00 AM - 7:00 PM
America Ballroom Foyer
Understanding the chemical composition of a galaxy is vital to tracing its global evolution. However, characterizing overall abundances for spirals poses a challenge since these galaxies tend to possess gradients in their chemical compositions. Here, a recent proposal for determining global oxygen abundances for spirals is explored and extended. By separately integrating the absolute amounts of hydrogen and oxygen within circles of increasing radii, it is shown that the overall oxygen abundance generally approaches an asymptote. The asymptote is a viable measure of the overall chemical state of a spiral, and allows for comparisons of the chemical evolution with respect to other galaxies, such as dwarf irregulars, whose chemistry is better understood.
329.05
Deep Images of the Stellar Stream Around NGC 5907
Seppo J. Laine1, J. Davies1, D. Martinez-Delgado2, C. Grillmair1, R. Arendt3, M. L. N. Ashby4, S. Majewski5, R. J. GaBany6
1Caltech, 2MPIA, Germany, 3CRESST/UMBC/GSFC, 4CfA/Harvard, 5U. Virginia, 6Blackbird Obs..
8:00 AM - 7:00 PM
America Ballroom Foyer
We have obtained ultra-deep visible light and Spitzer/IRAC images of the stellar stream around the nearby edge-on disk galaxy NGC 5907. We report on the color index distribution of the resolved emission from the stream, and our search for point sources and recent star formation associated with the stream. We speculate on the nature of the disrupted satellite galaxy, based on our observations. This work is based in part on observations made with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, California Institute of Technology under a contract with NASA. Support for this work was provided by NASA through an award issued by JPL/Caltech.
329.06
Enhancing the Picture of Star Formation in Local Galaxies with the Green Bank Telescope
Katherine Rabidoux1, K. Johnson2, A. Kepley2, D. J. Pisano1, D. Balser3
1West Virginia University, 2University of Virginia, 3National Radio Astronomy Observatory.
8:00 AM - 7:00 PM
America Ballroom Foyer
The radio continuum is an excellent probe of recent star formation in other galaxies. Free-free thermal emission is characterized by a flat spectrum and will be the strongest contributor to the radio continuum at frequencies between ~30-100 GHz in star-forming galaxies. The thermal free-free emission constrains the number of ionizing photons, and thus the number of massive stars in star-forming regions. Observations at these frequencies are necessary in order to disentangle the relative contributions of thermal free-free emission and nonthermal synchrotron emission and are complementary to observations of star formation tracers at other wavelengths.
We observed 26 local star-forming galaxies with the Caltech Continuum Backend on the Green Bank Telescope between 26 and 40 GHz. We have found that while some sources in our survey have relatively flat spectral indices, most have steep spectral indices over this range of frequencies. By separating the relative contributions from thermal and non-thermal flux and modeling the SEDs of these galaxies, we will infer their physical properties (temperature, density, pressure, size, etc.), and thus the dispersion timescale of star-forming regions, further constraining the star formation timescale. We have also mapped three luminous compact blue galaxies at 26-40 GHz with CCB and at 90 GHz with the MUSTANG bolometer array on the GBT. While we had expected these three galaxies to have the flat spectra characteristic of star-forming regions based on previous multi-wavelength observations, instead they had steep spectra indicative of a large non-thermal synchrotron component. Overall, our observations present a complex picture of star formation in nearby starbursting galaxies. Support for this work was provided by the NSF through award GSSP 10-0002 from the NRAO.
329.07
The Shearing HI Pattern of NGC 3031
Jason Speights1, D. Westpfahl1
1New Mexico Tech.
8:00 AM - 7:00 PM
America Ballroom Foyer
We present the pattern speed as a function of radius for the grand-design spiral galaxy NGC 3031, and the dwarf irregular galaxies NGC 2366 and DDO 154. The pattern speeds were found using a method of solving the Tremaine-Weinberg equations that allows for radial variation. Three different data sets of NGC 3031 were used for determining the pattern speed and its radial behavior. The results for NGC 3031 show convincing evidence for a shearing pattern, which is inconsistent with the assumption of a rigid pattern in some theories of spiral structure. The method was applied to NGC 2366 and DDO 154 to see what sorts of results are obtained for patterns that are not very coherent or well organized. Understanding how the solution method is affected by the different qualities of a data set will be useful for selecting a sample of galaxies for applying the method.
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