Issue |
A&A
Volume 474, Number 2, November I 2007
|
|
---|---|---|
Page(s) | 461 - 472 | |
Section | Extragalactic astronomy | |
DOI | https://doi.org/10.1051/0004-6361:20077729 | |
Published online | 28 August 2007 |
PAHs in the halo of NGC 5529
1
Dept. of Physics, Engineering Physics, & Astronomy, Queen's University, Kingston, K7L 3N6, Canada e-mail: irwin@astro.queensu.ca
2
CEA/Saclay, Service d'Astrophysique, Orme des Merisiers, Bâtiment 709, 91191 Gif-sur-Yvette Cedex, France e-mail: smadden@cea.fr
Received:
26
April
2007
Accepted:
28
August
2007
We present sensitive ISO m observations of the edge-on galaxy,
NGC 5529, finding an extensive MIR halo around NGC 5529. The emission is dominated by PAHs in
this band. The PAH halo has an exponential scale height of 3.7 kpc but
can still be detected as far as ≈10 kpc from the plane
to the limits of the high dynamic range (1770/1) data.
This is the most extensive
PAH halo yet detected in a normal galaxy. This halo
shows substructure and the PAHs likely originate from some type of disk
outflow. PAHs are long-lived in a halo environment and therefore
continuous replenishment from the disk is not required
(unless halo PAHs are also being destroyed or removed), consistent with
the current low SFR of the galaxy. The PAHs correlate spatially with
halo Hα emission, previously observed by Miller & Veilleux (2003, ApJS, 148, 383);
both components are likely excited/ionized by in-disk photons that are
leaking into the halo. The presence of halo gas may be related to the
environment of NGC 5529 which contains at least 17 galaxies in a small
group of which NGC 5529 is the dominant member. Of these, we have identified
two new companions from the SDSS.
Key words: galaxies: general / galaxies: individual: NGC 5529 / galaxies: halos / galaxies: ISM
© ESO, 2007
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