[seminar] Astro Journal Club on 3 Dec

[Oskari Miettinen]

Dear all,

Astro Journal Club will be held this Wednesday at 10:15 in the seminar
room F-201 of the Physics Department. This time we will discuss about the
new ALMA molecular line observations towards NGC1097.

Presenter: Oskari Miettinen
Paper title: Multi-molecule ALMA observations towards the Seyfert 1 galaxy
NGC 1097
Authors: Martin, S., Kohno, K., Izumi, T., et al.

Abstract:
The nearby Sy 1 galaxy NGC 1097 represents an ideal laboratory to explore
the molecular chemistry in the presence and surroundings of an active
galactic nucleus. Exploring the distribution of different molecular
species allows us to understand the physical processes affecting the ISM
both in the AGN vicinity as well as in the outer star forming molecular
ring. We carried out 3 mm ALMA observations of HCN, HCO+, CCH, CS, HNCO,
SiO, HC3N, and SO as well as the 13C isotopologues. All species were
imaged over the central 2 kpc (30 arcsec) of the galaxy at a resolution of
2.2x1.5 arcsec2 (150 pc x 100 pc). HCO+ and CS appear to be slightly
enhanced in the star forming ring. CCH, showing the largest variations
across NGC 1097, is suggested to be a good tracer of both obscured and
early stage star formation. HNCO, SiO and HC3N are significantly enhanced
in the inner circumnuclear disk surrounding the AGN. Differences in the
molecular abundances are observed between the star forming ring and the
inner circumnuclear disk. We conclude that the HCN/HCO+ and HCN/CS
differences observed between AGN dominated and starburst galaxies are not
due to a HCN enhancement due to X-rays, but rather this enhancement is
produced by shocked material at distances of 200 pc from the AGN.
Additionally we claim the lower HCN/CS to be a combination of a small
under-abundance of CS in AGNs together with excitation effects, where a
high dense gas component (10^6 cm-3) may be more prominent in SB galaxies.
However the most promising are the differences found among the dense gas
tracers which, at our modest spatial resolution, seem to outline the
physical structure of the molecular disk around the AGN. In this picture,
HNCO probes the well shielded gas in the disk, surrounding the dense
material moderately exposed to X-ray radiation traced by HC3N. Finally SiO
might be the innermost molecule in the disk structure.

Link to the paper: http://adsabs.harvard.edu/abs/2014arXiv1410.2823M

Hope to see you all tomorrow!

Best regards,
Oskari Miettinen