Publications (3)0 Total impact
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ABSTRACT: With the rapid progress in metallicity gradient studies at high-redshift, it
is imperative that we thoroughly understand the systematics in these
measurements. This work investigates how the [NII]/Halpha ratio based
metallicity gradients change with angular resolution, signal-to-noise (S/N),
and annular binning parameters. Two approaches are used: 1. We downgrade the
high angular resolution integral-field data of a gravitationally lensed galaxy
and re-derive the metallicity gradients at different angular resolution; 2. We
simulate high-redshift integral field spectroscopy (IFS) observations under
different angular resolution and S/N conditions using a local galaxy with a
known gradient. We find that the measured metallicity gradient changes
systematically with angular resolution and annular binning. Seeing-limited
observations produce significantly flatter gradients than higher angular
resolution observations. There is a critical angular resolution limit beyond
which the measured metallicity gradient is substantially different to the
intrinsic gradient. This critical angular resolution depends on the intrinsic
gradient of the galaxy and is < 0.02 arcsec for our simulated galaxy. We show
that seeing-limited high-redshift metallicity gradients are likely to be
strongly affected by resolution-driven gradient flattening. Annular binning
with a small number of annuli produces a more flattened gradient than the
intrinsic gradient due to weak line smearing. For 3-annuli bins, a minimum S/N
of ~ 5 on the [NII] line is required for the faintest annulus to constrain the
gradients with meaningful errors.
02/2013;
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Hanae Inami,
L. Armus,
J. A. Surace,
J. M. Mazzarella,
A. S. Evans,
D. B. Sanders,
J. H. Howell,
A. Petric,
T. Vavilkin,
K. Iwasawa, [......],
J. A. Marshall,
H. Matsuhara,
J. E. Melbourne, J. Rich,
B. Schulz,
H. W. W. Spoon,
E. Sturm,
V. U,
S. Veilleux,
K Xu
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ABSTRACT: An analysis of data from the Spitzer Space Telescope, Hubble Space Telescope, Chandra X-ray Observatory, and AKARI Infrared Astronomy Satellite is presented for the z=0.036 merging galaxy system II Zw 096 (CGCG 448-020). Because II Zw 096 has an infrared luminosity of log(L_IR/L_sun) = 11.94, it is classified as a Luminous Infrared Galaxy (LIRG), and was observed as part of the Great Observatories All-sky LIRG Survey (GOALS). The Spitzer data suggest that 80% of the total infrared luminosity comes from an extremely compact, red source not associated with the nuclei of the merging galaxies. The Spitzer mid-infrared spectra indicate no high-ionization lines from a buried active galactic nucleus in this source. The strong detection of the 3.3 micron and 6.2 micron PAH emission features in the AKARI and Spitzer spectra also implies that the energy source of II Zw 096 is a starburst. Based on Spitzer infrared imaging and AKARI near-infrared spectroscopy, the star formation rate is estimated to be 120 M_sun/yr and > 45 M_sun/yr, respectively. Finally, the high-resolution B, I, and H-band images show many star clusters in the interacting system. The colors of these clusters suggest at least two populations - one with an age of 1-5 Myr and one with an age of 20-500 Myr, reddened by 0-2 magnitudes of visual extinction. The masses of these clusters span a range between 10^6-10^8 M_sun. This starburst source is reminiscent of the extra-nuclear starburst seen in NGC 4038/9 (the Antennae Galaxies) and Arp 299 but approximately an order of magnitude more luminous than the Antennae. The source is remarkable in that the off-nuclear infrared luminosity dominates the enitre system. Comment: 46 pages, 10 figures, accepted for publication in AJ
04/2010;
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L. Armus,
J. M. Mazzarella,
A. S. Evans,
J. A. Surace,
D. B. Sanders,
K. Iwasawa,
D. T. Frayer,
J. H. Howell,
B. Chan,
A. O. Petric, [......],
J. A. Marshall,
J. E. Melbourne, J. Rich,
S. Satyapal,
B. Schulz,
H. W. W. Spoon,
E. Sturm,
V. U,
S. Veilleux,
K Xu
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ABSTRACT: The Great Observatories All-sky LIRG Survey (GOALS) combines data from NASA's Spitzer, Chandra, Hubble and GALEX observatories, together with ground-based data into a comprehensive imaging and spectroscopic survey of over 200 low redshift Luminous Infrared Galaxies (LIRGs). The LIRGs are a complete subset of the IRAS Revised Bright Galaxy Sample (RBGS). The LIRGs targeted in GOALS span the full range of nuclear spectral types defined via traditional optical line-ratio diagrams as well as interaction stages. They provide an unbiased picture of the processes responsible for enhanced infrared emission in galaxies in the local Universe. As an example of the analytic power of the multi-wavelength GOALS dataset, we present data for the interacting system VV 340 (IRAS F14547+2449). Between 80-95% of the total far-infrared emission (or about 5E11 solar luminosities) originates in VV 340 North. While the IRAC colors of VV 340 North and South are consistent with star-forming galaxies, both the Spitzer IRS and Chandra ACIS data indicate the presence of a buried AGN in VV 340 North. The GALEX far and near-UV fluxes imply a extremely large infrared "excess" (IRX) for the system (IR/FUV = 81) which is well above the correlation seen in starburst galaxies. Most of this excess is driven by VV 340 N, which alone has an IR excess of nearly 400. The VV 340 system seems to be comprised of two very different galaxies - an infrared luminous edge-on galaxy (VV 340 North) that dominates the long-wavelength emission from the system and which hosts a buried AGN, and a face-on starburst (VV 340 South) that dominates the short-wavelength emission. Comment: 17 pages, 2 tables, 7 postscript figures. Accepted for publication in PASP. Updated manuscript includes complete source table (Table 1)
04/2009;
