J/A+A/592/A20 NGC 1316 and NGC 612 WISE images (Duah Asabere+, 2016)
Mid-infrared dust in two nearby radio galaxies, NGC 1316 (Fornax A) and
NGC 612 (PKS 0131-36).
Duah Asabere B., Horellou C., Jarrett T.H., Winkler H.
<Astron. Astrophys. 592, A20 (2016)>
=2016A&A...592A..20D 2016A&A...592A..20D (SIMBAD/NED BibCode)
ADC_Keywords: Galaxies, radio ; Photometry, infrared
Keywords: galaxies: individual: NGC 1316 (Fornax A) - galaxies: ISM -
galaxies: interactions - infrared: galaxies -
galaxies: individual: NGC 612 (PKS 0131-36)
Abstract:
Most radio galaxies are hosted by giant gas-poor ellipticals, but some
contain significant amounts of dust, which is likely to be of external
origin. In order to characterize the mid-IR properties of two of the
most nearby and brightest merger-remnant radio galaxies of the
Southern hemisphere, NGC 1316 (Fornax A) and NGC 612 (PKS 0131-36), we
used observations with the Wide-field Infrared Survey Explorer (WISE)
at wavelengths of 3.4, 4.6, 12 and 22 micron and Spitzer mid-infrared
spectra.
By applying a resolution-enhancement technique, new WISE images were
produced at angular resolutions ranging from 2.6" to 5.5". Global
measurements were performed in the four WISE bands, and stellar masses
and star-formation rates were estimated using published scaling
relations.
Two methods were used to uncover the distribution of dust, one relying
on two-dimensional fits to the 3.4 micron images to model the
starlight, and the other one using a simple scaling and subtraction of
the 3.4 micron images to estimate the stellar continuum contribution
to the emission in the 12 and 22 micron bands. The two galaxies differ
markedly in their mid-IR properties. The 3.4 micron brightness
distribution can be well represented by the superposition of two
Sersic models in NGC 1316 and by a Sersic model and an exponential
disk in NGC 612. The WISE colors of NGC 1316 are typical of those of
early-type galaxies; those of NGC 612 are in the range found for
star-forming galaxies. From the 22 micron luminosity, we infer a
star-formation rate of about 0.7 solar masses per year in NGC 1316 and
about 7 solar masses per year in NGC 612. Spitzer spectroscopy shows
that the 7.7-to-11.3 micron PAH line ratio is significantly lower in
NGC 1316 than in NGC 612. The WISE images reveal resolved emission
from dust in the central 1'-2' of the galaxies. In NGC 1316, the
extra-nuclear emission coincides with two dusty regions NW and SE of
the nucleus seen in extinction in optical images and where molecular
gas is known to reside. In NGC 612 it comes from a warped disk. This
suggests a recent infall onto NGC 1316 and disruption of one or
several smaller gas-rich galaxies, but a smoother accretion in NGC
612. While the nucleus of NGC 1316 is currently dormant and the galaxy
is likely to evolve into a passive elliptical, NGC 612 has the
potential of growing a larger disk and sustaining an active nucleus.
NGC 1316 and NGC 612 represent interesting challenges to models of
formation and evolution of galaxies and AGNs.
Description:
Mid-IR level 1-b frames of NGC 1316 and NGC 612 were downloaded from
the WISE archive4. In order to improve the resolution of those images,
we used the Image Coaddition with Optional Resolution Enhancement
software package (ICORE) and a deconvolution technique based on the
Maximum Correlation Method (MCMHiRes). This allowed an improvement of
a factor of 3-4 in angular resolution compared to the publicly
released mosaics, which were optimized for point-source detection and
have a degraded resolution of 30 to 40% compared to the native single
frames (see Cutri et al., 2012, Cat. II/311; Jarrett et al.,
2013AJ....145....6J 2013AJ....145....6J).
Objects:
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RA (2000) DE Designation(s)
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03 22 41.79 -37 12 29.5 NGC 1316 = NAME FORNAX A
01 33 57.74 -36 29 35.9 NGC 612 = PKS 0131-36
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
list.dat 150 20 List of fits images
fits/* . 20 Individual fits images
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See also:
II/311 : WISE All-Sky Data Release (Cutri+ 2012)
Byte-by-byte Description of file: list.dat
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Bytes Format Units Label Explanations
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1- 9 F9.5 deg RAdeg ? Right Ascension of center (J2000)
10- 18 F9.5 deg DEdeg ? Declination of center (J2000)
20- 23 I4 --- Nx Number of pixels along X-axis
25- 28 I4 --- Ny Number of pixels along Y-axis
30- 48 A19 --- Obs.Date Observation date (YYYY-MM-DDThh:mm:ss)
50- 54 I5 Kibyte size Size of FITS file
56- 82 A27 --- FileName Name of FITS file, in subdirectory fits
84-150 A67 --- Title Title of the FITS file
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Acknowledgements:
Cathy Horellou, cathy.horellou(at)chalmers.se
(End) Patricia Vannier [CDS] 02-Jun-2016