41 research outputs found
Correlations between Ultrahigh Energy Cosmic Rays and Infrared-Luminous Galaxies
We confirm the UHECR horizon established by the Pierre Auger Observatory
using the heterogeneous Veron-Cetty Veron (VCV) catalog of AGNs, by performing
a redshift-angle-IR luminosity scan using PSCz galaxies having infrared
luminosity greater than 10^{10}L_sun. The strongest correlation -- for z <
0.016, psi = 2.1 deg, and L_ir > 10^{10.5}L_sun -- arises in fewer than 0.3% of
scans with isotropic source directions. When we apply a penalty for using the
UHECR energy threshold that was tuned to maximize the correlation with VCV, the
significance degrades to 1.1%. Since the PSCz catalog is complete and
volume-limited for these parameters, this suggests that the UHECR horizon
discovered by the Pierre Auger Observatory is not an artifact of the
incompleteness and other idiosyncrasies of the VCV catalog. The strength of the
correlation between UHECRs and the nearby highest-IR-luminosity PSCz galaxies
is stronger than in about 90% percent of trials with scrambled luminosity
assignments for the PSCz galaxies. If confirmed by future data, this result
would indicate that the sources of UHECRs are more strongly associated with
luminous IR galaxies than with ordinary, lower IR luminosity galaxies.Comment: 4 pages, 3 figures. Replaced with accepted versio
S7 : Probing the physics of Seyfert Galaxies through their ENLR & HII Regions
Here we present the first results from the Siding Spring Southern Seyfert
Spectroscopic Snapshot Survey (S7) which aims to investigate the physics of
~140 radio-detected southern active Galaxies with z<0.02 through Integral Field
Spectroscopy using the Wide Field Spectrograph (WiFeS). This instrument
provides data cubes of the central 38 x 25 arc sec. of the target galaxies in
the waveband 340-710nm with the unusually high resolution of R=7000 in the red
(530-710nm), and R=3000 in the blue (340-560nm). These data provide the
morphology, kinematics and the excitation structure of the extended narrow-line
region, probe relationships with the black hole characteristics and the host
galaxy, measures host galaxy abundance gradients and the determination of
nuclear abundances from the HII regions. From photoionisation modelling, we may
determine the shape of the ionising spectrum of the AGN, discover whether AGN
metallicities differ from nuclear abundances determined from HII regions, and
probe grain destruction in the vicinity of the AGN. Here we present some
preliminary results and modelling of both Seyfert galaxies observed as part of
the survey.Comment: 6 pages, 2 figures, Invited Talk at the IAU symposium 30
Probing the Physics of Narrow Line Regions in Active Galaxies II: The Siding Spring Southern Seyfert Spectroscopic Snapshot Survey (S7)
Here we describe the \emph{Siding Spring Southern Seyfert Spectroscopic
Snapshot Survey} (S7) and present results on 64 galaxies drawn from the first
data release. The S7 uses the Wide Field Spectrograph (WiFeS) mounted on the
ANU 2.3m telescope located at the Siding Spring Observatory to deliver an
integral field of ~ arcsec at a spectral resolution of in
the red (nm), and in the blue (nm). {From these data
cubes we have extracted the Narrow Line Region (NLR) spectra from a 4 arc sec
aperture centred on the nucleus. We also determine the H and
[OIII]~5007 fluxes in the narrow lines, the nuclear reddening, the
reddening-corrected relative intensities of the observed emission lines, and
the H and \lOIII\ luminosities {determined from spectra for which the
stellar continuum has been removed.} We present a set of images of the galaxies
in [OIII]~5007, [NII]~6584 and H which serve to
delineate the spatial extent of the extended narrow line region (ENLR) and {\bf
also to} reveal the structure and morphology of the surrounding \HII\ regions.
Finally, we provide a preliminary discussion of those Seyfert~1 and Seyfert~2
galaxies which display coronal emission lines in order to explore the origin of
these lines.Comment: Accepted for publication 9 Jan 2015, Astrophysical Journal
Supplements. 49pages, 8 figure
Probing the Physics of Narrow Line Regions in Active Galaxies III: Accretion and Cocoon Shocks in the LINER NGC1052
We present Wide Field Spectrograph (WiFeS) integral field spectroscopy and
HST FOS spectroscopy for the LINER galaxy NGC 1052. We infer the presence of a
turbulent accretion flow forming a small-scale accretion disk. We find a
large-scale outflow and ionisation cone along the minor axis of the galaxy.
Part of this outflow region is photoionised by the AGN, and shares properties
with the ENLR of Seyfert galaxies, but the inner (~arcsec)
accretion disk and the region around the radio jet appear shock excited. The
emission line properties can be modelled by a "double shock" model in which the
accretion flow first passes through an accretion shock in the presence of a
hard X-ray radiation, and the accretion disk is then processed through a cocoon
shock driven by the overpressure of the radio jets. This model explains the
observation of two distinct densities ( and cm),
and provides a good fit to the observed emission line spectrum. We derive
estimates for the velocities of the two shock components and their mixing
fractions, the black hole mass, the accretion rate needed to sustain the LINER
emission and derive an estimate for the jet power. Our emission line model is
remarkably robust against variation of input parameters, and so offers a
generic explanation for the excitation of LINER galaxies, including those of
spiral type such as NGC 3031 (M81).Comment: Accepted for publication in Astrophysical Journal. 16 pages, 12
figure
Dissecting Galaxies: Separating Star Formation, Shock Excitation and AGN Activity in the Central Region of NGC 613
The most rapidly evolving regions of galaxies often display complex optical
spectra with emission lines excited by massive stars, shocks and accretion onto
supermassive black holes. Standard calibrations (such as for the star formation
rate) cannot be applied to such mixed spectra. In this paper we isolate the
contributions of star formation, shock excitation and active galactic nucleus
(AGN) activity to the emission line luminosities of individual spatially
resolved regions across the central 3 3 kpc region of the active
barred spiral galaxy NGC613. The star formation rate and AGN luminosity
calculated from the decomposed emission line maps are in close agreement with
independent estimates from data at other wavelengths. The star formation
component traces the B-band stellar continuum emission, and the AGN component
forms an ionization cone which is aligned with the nuclear radio jet. The
optical line emission associated with shock excitation is cospatial with strong
and [Fe II] emission and with regions of high ionized gas velocity
dispersion ( km s). The shock component also traces the
outer boundary of the AGN ionization cone and may therefore be produced by
outflowing material interacting with the surrounding interstellar medium. Our
decomposition method makes it possible to determine the properties of star
formation, shock excitation and AGN activity from optical spectra, without
contamination from other ionization mechanisms.Comment: 16 pages, 12 figures. Accepted for publication in MNRA