177 research outputs found
IFU observations of luminous type II AGN - I. Evidence for ubiquitous winds
We present observations of 17 luminous (log(L[O III]/L_Sun) > 8.7) local (z <
0.11) type II AGN. Our aim is to investigate the prevalence and nature of AGN
driven outflows in these galaxies by combining kinematic and ionization
diagnostic information. We use non-parametric methods (e.g. W80, the width
containing 80% of the line flux) to assess the line widths in the central
regions of our targets. The maximum values of W80 in each galaxy are in the
range 400 - 1600 km/s, with a mean of 790 +- 90 km/s. Such high velocities are
strongly suggestive that these AGN are driving ionized outflows. Multi-Gaussian
fitting is used to decompose the velocity structure in our galaxies. 14/17 of
our targets require 3 separate kinematic components in the ionized gas in their
central regions. The broadest components of these fits have FWHM = 530 - 2520
km/s, with a mean value of 920 +- 50 km/s. By simultaneously fitting both the
H{\beta}/[O III] and H{\alpha}/[N II] complexes we construct ionization
diagnostic diagrams for each component. 13/17 of our galaxies show a
significant (> 95 %) correlation between the [N II]/H{\alpha} ratio and the
velocity dispersion of the gas. Such a correlation is the natural consequence
of a contribution to the ionization from shock excitation and we argue that
this demonstrates that the outflows from these AGN are directly impacting the
surrounding ISM within the galaxies.Comment: 37 pages, 30 figures. Accepted for publication in MNRA
Spatially Resolved Spectroscopy of the E+A Galaxies in the z=0.32 Cluster AC114
We present spatially resolved intermediate resolution spectroscopy of a
sample of twelve E+A galaxies in the z=0.32 rich galaxy cluster AC 114,
obtained with the FLAMES multi-integral field unit system on the European
Southern Observatory's VLT. Previous integrated spectroscopy of all these
galaxies by Couch & Sharples (1987) had shown them to have strong Balmer line
absorption and an absence of [OII 3727] emission -- the defining
characteristics of the``E+A'' spectral signature, indicative of an abrupt halt
to a recent episode of quite vigorous star formation. We have used our spectral
data to determine the radial variation in the strength of Hdelta absorption in
these galaxies and hence map out the distribution of this recently formed
stellar population. Such information provides important clues as to what
physical event might have been responsible for this quite dramatic change in
star formation activity in these galaxies' recent past. We find a diversity of
behaviour amongst these galaxies in terms of the radial variation in Hdelta
absorption: Four galaxies show little Hdelta absorption across their entire
extent; it would appear they were misidentified as E+A galaxies in the earlier
integrated spectroscopic studies. The remainder show strong Hdelta absorption,
with a gradient that is either negative (Hdelta equivalent width decreasing
with radius), flat, or positive. By comparing with numerical simulations we
suggest that the first of these different types of radial behaviour provides
evidence for a merger/interaction origin, whereas the latter two types of
behaviour are more consistent with the truncation of star formation in normal
disk galaxies. It would seem therefore that more than one physical mechanism is
responsible for E+A formation in the same environment.Comment: 15 pages, 10 figures, accepted MNRA
The Large Area Radio Galaxy Evolution Spectroscopic Survey (LARGESS): survey design, data catalogue and GAMA/WiggleZ spectroscopy
© 2016 The Authors. We present the Large Area Radio Galaxy Evolution Spectroscopic Survey (LARGESS), a spectroscopic catalogue of radio sources designed to include the full range of radio AGN populations out to redshift z ~ 0.8. The catalogue covers ~800 deg 2 of sky, and provides optical identifications for 19 179 radio sources from the 1.4 GHz Faint Images of the Radio Sky at Twenty-cm (FIRST) survey down to an optical magnitude limit of i mod < 20.5 in Sloan Digital Sky Survey (SDSS) images. Both galaxies and point-like objects are included, and no colour cuts are applied. In collaboration with the WiggleZ and Galaxy And Mass Assembly (GAMA) spectroscopic survey teams, we have obtained new spectra for over 5000 objects in the LARGESS sample. Combining these new spectra with data from earlier surveys provides spectroscopic data for 12 329 radio sources in the survey area, of which 10 856 have reliable redshifts. 85 per cent of the LARGESS spectroscopic sample are radio AGN (median redshift z = 0.44), and 15 per cent are nearby star-forming galaxies (median z = 0.08). Low-excitation radio galaxies (LERGs) comprise the majority (83 per cent) of LARGESS radio AGN at z < 0.8, with 12 per cent being high-excitation radio galaxies (HERGs) and 5 per cent radioloud QSOs. Unlike the more homogeneous LERG and QSO sub-populations, HERGs are a heterogeneous class of objects with relatively blue optical colours and a wide dispersion in mid-infrared colours. This is consistent with a picture in which most HERGs are hosted by galaxies with recent or ongoing star formation as well as a classical accretion disc
HI emission and absorption in nearby, gas-rich galaxies II. -- sample completion and detection of intervening absorption in NGC 5156
We present the results of a survey for intervening 21cm HI absorption in a
sample of 10 nearby, gas-rich galaxies selected from the HI Parkes All-Sky
Survey (HIPASS). This follows the six HIPASS galaxies searched in previous work
and completes our full sample. In this paper we searched for absorption along
17 sightlines with impact parameters between 6 and 46 kpc, making one new
detection. We also obtained simultaneous HI emission-line data, allowing us to
directly relate the absorption-line detection rate to the HI distribution. From
this we find the majority of the non-detections in the current sample are
because sightline does not intersect the HI disc of the galaxy at sufficiently
high column density, but that source structure is also an important factor.
The detected absorption-line arises in the galaxy NGC 5156 () at an
impact parameter of 19 kpc. The line is deep and narrow with an integrated
optical depth of 0.82 km s. High resolution Australia Telescope Compact
Array (ATCA) images at 5 and 8 GHz reveal that the background source is
resolved into two components with a separation of 2.6 arcsec (500 pc at the
redshift of the galaxy), with the absorption likely occurring against a single
component. We estimate that the ratio of the spin temperature and covering
factor, , is approximately 950 K in the outer disc of NGC
5156, but further observations using VLBI would allow us to accurately measure
the covering factor and spin temperature of the gas.Comment: 31 pages, 11 figure
IFU observations of luminous type II AGN - I. Evidence for ubiquitous winds
We present observations of 17 luminous (log(L[O III]/L) > 8.7) local (z < 0.11) type II AGN.
Our aim is to investigate the prevalence and nature of AGN-driven outflows in these galaxies by
combining kinematic and ionization diagnostic information. We use non-parametric methods
(e.g. W80, the width containing 80 per cent of the line flux) to assess the line widths in the central
regions of our targets. The maximum values of W80 in each galaxy are in the range 400–1600 km
s−1, with a mean of 790 ± 90 km s−1. Such high velocities are strongly suggestive that these
AGN are driving ionized outflows. Multi-Gaussian fitting is used to decompose the velocity
structure in our galaxies. 14/17 of our targets require three separate kinematic components in
the ionized gas in their central regions. The broadest components of these fits have FWHM
= 530–2520 km s−1, with a mean value of 920 ± 50 km s−1. By simultaneously fitting
both the Hβ/[O III] and Hα/[N II] complexes, we construct ionization diagnostic diagrams for
each component. 13/17 of our galaxies show a significant (>95 per cent) correlation between
the [N II]/Hα ratio and the velocity dispersion of the gas. Such a correlation is the natural
consequence of a contribution to the ionization from shock excitation and we argue that this
demonstrates that the outflows from these AGN are directly impacting the surrounding ISM
within the galaxies.
Key words: galaxies: active – galaxies: evolution – galaxies: kinematics and dynamic
A Search for Propylene Oxide and Glycine in Sagittarius B2 (LMH) and Orion
We have used the Mopra Telescope to search for glycine and the simple chiral
molecule propylene oxide in the Sgr B2 (LMH) and Orion KL, in the 3-mm band. We
have not detected either species, but have been able to put sensitive upper
limits on the abundances of both molecules. The 3-sigma upper limits derived
for glycine conformer I are 3.7 x 10^{14} cm^{-2} in both Orion-KL and Sgr B2
(LMH), comparable to the reported detections of conformer I by Kuan et al.
However, as our values are 3-sigma upper limits rather than detections we
conclude that this weighs against confirming the detection of Kuan et al. We
find upper limits for the glycine II column density of 7.7 x 10^{12} cm^{-2} in
both Orion-KL and Sgr B2 (LMH), in agreement with the results of Combes et al.
The results presented here show that glycine conformer II is not present in the
extended gas at the levels detected by Kuan et al. for conformer I. Our ATCA
results (Jones et al.) have ruled out the detection of glycine (both conformers
I and II) in the compact hot core of the LMH at the levels reported, so we
conclude that it is unlikely that Kuan et al. have detected glycine in either
Sgr B2 or Orion-KL. We find upper limits for propylene oxide abundance of 3.0 x
10^{14} cm^{-2} in Orion-KL and 6.7 x 10^{14} cm^{-2} in Sgr B2 (LMH). We have
detected fourteen features in Sgr B2 and four features in Orion-KL which have
not previously been reported in the ISM, but have not be able to plausibly
assign these transitions to any carrier.Comment: 12 pages, 3 figures. Accepted by MNRAS 12th January 200
The star pile in Abell 545
Context:Struble (1988) found what appeared to be a cD halo without cD galaxy
in the center of the galaxy cluster Abell 545. This remarkable feature has been
passed almost unnoticed for nearly twenty years.
Aims:Our goal is to review Struble's claim by providing a first (preliminary)
photometric and spectroscopic analysis of this ''star pile''.
Methods:Based on archival VLT-images and long-slit spectra obtained with
Gemini-GMOS, we describe the photometric structure and measure the redshift of
the star pile and of the central galaxy.
Results:The star pile is indeed associated with Abell 545. Its velocity is
higher by about 1300 km/s than that of the central object. The spectra indicate
an old, presumably metal-rich population. Its brightness profile is much
shallower than that of typical cD-galaxies.
Conclusions:The formation history and the dynamical status of the star pile
remain elusive, until high S/N spectra and a dynamical analysis of the galaxy
cluster itself become available. We suggest that the star pile might provide an
interesting test of the Cold Dark Matter paradigm.Comment: 6 pages, 7 figures. Accepted for publication in A&
Legislative History: An Act to Amend the Date to Determine Age for Kindergarten Eligibility (HP284)(LD 367)
https://digitalmaine.com/legishist113/1366/thumbnail.jp
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