Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Extended Red Emission in the "Evil Eye" Galaxy (NGC4826)   We obtained low-resolution, long-slit 5300--9100 A spectroscopy of NGC4826 (a
nearby galaxy with an absorbing dust lane (DL) asymmetrically placed across its
bulge, associated with several HII regions) with a slit encompassing its bulge,
positioned across its nucleus. The wavelength-dependent effects of absorption
and scattering by dust in the lane are evident when comparing the observed
stellar SEDs of pairs of positions symmetrically located with respect to the
nucleus, one on the DL side and one on the opposite side of the bulge, by
assuming that the intrinsic ISRF is axi-symmetric. We analyzed these SED ratios
through the multiple-scattering radiative transfer model of Witt and Gordon and
we discovered strong residual Extended Red Emission (ERE) from a region of the
DL within a distance of 13 arcsec from the nucleus, adjacent to a broad, bright
HII region. ERE is an established phenomenon in the literature interpreted as
originating from photoluminescence by nanometer-sized clusters, illuminated by
UV/optical photons. The complex radial variation of the ERE band-integrated
intensity and of the ERE-to-scattered light band-integrated intensity ratio
with the optical depth of the model derived for the DL and with the strength
and hardness of the illuminating ISRF is reproduced consistently through the
theoretical interpretation of the photophysics of the ERE carrier by Smith and
Witt. When examined within the context of ERE observations in a variety of
Galactic dusty environments (e.g. the diffuse ISM, reflection nebulae,
planetary nebulae and the Orion Nebula), we conclude that the ERE photon
conversion efficiency in NGC4826 is as high as found elsewhere, but that the
size of the actively luminescing nanoparticles there is about twice as large as
those thought to exist in the Galactic diffuse ISM.

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The categories of this paper are: q-bio
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The categories of this paper are: solv-int
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The categories of this paper are: comp-gas
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The categories of this paper are: cs
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The categories of this paper are: cond-mat
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The categories of this paper are: acc-phys
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The categories of this paper are: bayes-an
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The categories of this paper are: eess
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The categories of this paper are: physics
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The categories of this paper are: adap-org
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The categories of this paper are: q-fin
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The categories of this paper are: atom-ph
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The categories of this paper are: quant-ph
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The categories of this paper are: cmp-lg
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The categories of this paper are: plasm-ph
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The categories of this paper are: ao-sci