60 research outputs found
Molecular gas observations of the reddened quasar 3C 318
3C 318 is a z=1.574 radio-loud quasar. The small physical size of its radio
jets indicate that these jets were triggered relatively recently. In addition
to the ultraviolet continuum emission being reddened by dust, detections with
IRAS and SCUBA show it to have an exceptionally high far-infrared luminosity.
We present CO(2-1) observations of 3C 318 made with the IRAM Plateau de Bure
Interferometer. We detect CO(2-1) emission with a FWHM=200 km/s at a
signal-to-noise ratio of 5.4. There is evidence for positional (~ 20 kpc) and
velocity (~ -400 km/s) offsets between the molecular gas and the quasar which
may be due to the quasar experiencing a major merger. The mass of molecular gas
inferred from our observations is M_{H_2}=(3.0 +/- 0.6) x 10^{10} M_sun. This
molecular gas mass is comparable to that in sub-mm-selected galaxies at similar
redshifts. The large molecular gas mass is consistent with the primary source
of heating for the cool dust in this quasar to be massive star formation with a
star formation rate of 1700 M_sun/yr and a gas depletion timescale of 20 Myr.
Our observations support the idea that star formation episodes and jet
triggering can be synchronised.Comment: 4 pages, 3 b/w figures, AJ, in pres
Kepler Observations of V447 Lyr: An Eclipsing U Gem Cataclysmic Variable
We present the results of an analysis of data covering 1.5 years of the dwarf
nova V447 Lyr. We detect eclipses of the accretion disk by the mass donating
secondary star every 3.74 hrs which is the binary orbital period. V447 Lyr is
therefore the first dwarf nova in the Kepler field to show eclipses. We also
detect five long outbursts and six short outbursts showing V447 Lyr is a U Gem
type dwarf nova. We show that the orbital phase of the mid-eclipse occurs
earlier during outbursts compared to quiescence and that the width of the
eclipse is greater during outburst. This suggests that the bright spot is more
prominent during quiescence and that the disk is larger during outburst than
quiescence. This is consistent with an expansion of the outer disk radius due
to the presence of high viscosity material associated with the outburst,
followed by a contraction in quiescence due to the accretion of low angular
momentum material. We note that the long outbursts appear to be triggered by a
short outburst, which is also observed in the super-outbursts of SU UMa dwarf
novae as observed using Kepler.Comment: Accepted by MNRA
Edusource: Canada's Learning Object Repository Network
An alliance of Canadian Universities and government agencies pooled their resources to establish a network to share and combine Learning Objects from a variety of sources and further develop this technology. In the process, they resolved many learning, logistical, and legal problems and moved this technology forward by an order of magnitude. Principal goals include: nationwide interoperability, network of repositories, linked servers, repository software programs, national and international standards, digital rights management, business and management models, evaluation and feedback, dissemination of results, and bilingual access to all Canadians, particularly learners with disabilities. The defined tasks were sub-divided into nine work packages, each with a lead institution as package manager
Serendipitous Kepler observations of a background dwarf nova of SU UMa type
We have discovered a dwarf nova (DN) of type SU UMa in Kepler data which is
7.0 arcsec from the G-type exoplanet survey target KIC 4378554. The DN appears
as a background source in the pixel aperture of the foreground G star. We
extracted only the pixels where the DN is present and observed the source to
undergo five outbursts -- one a superoutburst -- over a timespan of 22 months.
The superoutburst was triggered by a normal outburst, a feature that has been
seen in all DNe superoutburst observed by Kepler. Superhumps during the super
outburst had a period of 1.842+/-0.004 h and we see a transition from
disc-dominated superhump signal to a mix of disc and accretion stream impact.
Predictions of the number of DNe present in Kepler data based on previously
published space densities vary from 0.3 to 258. An investigation of the
background pixels targets would lead to firmer constraints on the space density
of DN.Comment: Accepted for publication in MNRA
Anti-Nirvana: crime, culture and instrumentalism in the age of insecurity
‘Anti-Nirvana’ explores the relationship between consumer culture, media and criminal motivations. It has appeared consistently on the list of the top-ten most-read articles in this award-winning international journal, and it mounts a serious neo-Freudian challenge to the predominant naturalistic notion of ‘resistance’ at the heart of liberal criminology and media studies. It is also cited in the Oxford Handbook of Criminology and other criminology texts as a persuasive argument in support of the theory that criminality amongst young people is strongly linked to the acquisitive values of consumerism and the images of possessive individualism that dominate mass media
Millimetre observations of a sample of high-redshift obscured quasars
We present observations at 1.2 mm with MAMBO-II of a sample of z>~2
radio-intermediate obscured quasars, as well as CO observations of two sources
with the Plateau de Bure Interferometer. Five out of 21 sources (24%) are
detected at a significance of >=3sigma. Stacking all sources leads to a
statistical detection of = 0.96+-0.11 mJy and stacking only the
non-detections also yields a statistical detection, with = 0.51+-0.13
mJy. This corresponds to a typical far-infrared luminosity L_FIR~4x10^12 Lsol.
If the far-infrared luminosity is powered entirely by star-formation, and not
by AGN-heated dust, then the characteristic inferred star-formation rate is
~700 Msol yr-1. This far-infrared luminosity implies a dust mass of
M_dust~3x10^8 Msol. We estimate that such large dust masses on kpc scales can
plausibly cause the obscuration of the quasars. We present dust SEDs for our
sample and derive a mean SED for our sample. This mean SED is not well fitted
by clumpy torus models, unless additional extinction and far-infrared
re-emission due to cool dust are included. There is a hint that the host
galaxies of obscured quasars must have higher far-infrared luminosities and
cool-dust masses and are therefore often found at an earlier evolutionary phase
than those of unobscured quasars. For one source at z=2.767, we detect the
CO(3-2) transition, with S_CO Delta nu=630+-50 mJy km s-1, corresponding to
L_CO(3-2)= 3.2x10^7 Lsol, or L'_CO(3-2)=2.4x10^10 K km s-1 pc2. For another
source at z=4.17, the lack of detection of the CO(4-3) line yields a limit of
L'_CO(4-3)<1x10^10 K km s-1 pc2. Molecular gas masses, gas depletion timescales
and gas-to-dust ratios are estimated (Abridged).Comment: Accepted by ApJ, 25 pages, 11 figures, 4 table
Gas and dust in a z=2.8 obscured quasar
We present new detections of the CO(5-4), CO(7-6), [CI](1-0) and [CI](2-1)
molecular and atomic line transitions towards the unlensed, obscured quasar
AMS12 (z=2.7672), observed with the IRAM PdBI. This is the first unlensed, high
redshift source to have both [CI] transitions detected. Continuum measurements
between 70 m and 3 mm are used to constrain the FIR SED, and we find a
best fit FIR luminosity of log[Lfir/Lsol] = 13.5+/-0.1, dust temperature T_d =
88+/-8 K and emissivity index {\beta} = 0.6+/-0.1. The highly-excited molecular
gas probed by CO(3-2), (5-4) and (7-6), is modelled with large velocity
gradient (LVG) models. The gas kinetic temperature T_g, density n(H2), and the
characteristic size r0, are determined using the dust temperature from the FIR
SED as a prior for the gas temperature. The best fitting parameters are T_g =
90+/-8 K, n(H2) = 10^(3.9+/-0.1) cm^(-3) and r0 = 0.8+/-0.04 kpc. The ratio of
the [CI] lines gives a [CI] excitation temperature of 43+/-10 K, indicating the
[CI] and the high-excitation CO are not in thermal equilibrium. The [CI]
excitation temperature is below that of T_d and T_g of the high-excitation CO,
perhaps because [CI] lies at a larger radius where there may also be a large
reservoir of CO at a cooler temperature, perhaps detectable through the
CO(1-0). Using the [CI](1-0) line we can estimate the strength of the CO(1-0)
line and hence the gas mass. This suggests that a significant fraction (~30%)
of the molecular gas is missed from the high-excitation line analysis. The
Eddington limited black hole mass is found from the bolometric luminosity to be
Mbh >~ 1.5x10^9 Msol. Along with the stellar mass of 3x10^11 Msol, these give a
black hole - bulge mass ratio of Mbh/Mbulge >~ 0.005. This is in agreement with
studies on the evolution of the Mbh/Mbulge relationship at high redshifts,
which find a departure from the local value ~0.002.Comment: Accepted by MNRAS, 17 pages, 9 figure
A tale of two capitalisms: preliminary spatial and historical comparisons of homicide rates in Western Europe and the USA
This article examines comparative homicide rates in the United States and Western Europe in an era of increasingly globalized neoliberal economics. The main finding of this preliminary analysis is that historical and spatial correlations between distinct forms of political economy and homicide rates are consistent enough to suggest that social democratic regimes are more successful at fostering the socio-cultural conditions necessary for reduced homicide rates. Thus Western Europe and all continents and nations should approach the importation of American neo-liberal economic policies with extreme caution. The article concludes by suggesting that the indirect but crucial causal connection between political economy and homicide rates, prematurely pushed into the background of criminological thought during the ‘cultural turn’, should be returned to the foreground
The Canada-UK Deep Submillimetre Survey VIII: Source Identifications in the 3-hour field
We present optical, near-infrared and radio observations of the 3-hour field
of the Canada-UK Deep Submillimetre Survey. Of the 27 submillimetre sources in
the field, nine have secure identifications with either a radio source or a
near-IR source. We show that the percentage of sources with secure
identifications in the CUDSS is consistent with that found for the bright `8
mJy' submillimetre survey, once allowance is made for the different
submillimetre and radio flux limits. Of the 14 secure identifications in the
two CUDSS fields, eight are VROs or EROs, five have colours typical of normal
galaxies, and one is a radio source which has not yet been detected at
optical/near-IR wavelengths. Eleven of the identifications have optical/near-IR
structures which are either disturbed or have some peculiarity which suggests
that the host galaxy is part of an interacting system. One difference between
the CUDSS results and the results from the 8-mJy survey is the large number of
low-redshift objects in the CUDSS; we give several arguments why these are
genuine low-redshift submillimetre sources rather than being gravitational
lenses which are gravitationally amplifying a high- submillimetre source. We
construct a diagram for various classes of high-redshift galaxy and show
that the SCUBA galaxies are on average less luminous than classical radio
galaxies, but are very similar in both their optical/IR luminosities and their
colours to the host galaxies of the radio sources detected in Jy radio
surveys.Comment: accepted for publication in MNRAS, 18 pages, full-resolution versions
of Figure 1 and 2 can be found at
http://www.astro.cf.ac.uk/groups/cosmo/papers.htm
Molecular and atomic gas in dust lane early-type galaxies - I : Low star-formation efficiencies in minor merger remnants
In this work we present IRAM-30m telescope observations of a sample of bulge-dominated galaxies with large dust lanes, which have had a recent minor merger. We find these galaxies are very gas rich, with H2 masses between 4x10^8 and 2x10^10 Msun. We use these molecular gas masses, combined with atomic gas masses from an accompanying paper, to calculate gas-to-dust and gas-to-stellar mass ratios. The gas-to-dust ratios of our sample objects vary widely (between ~50 and 750), suggesting many objects have low gas-phase metallicities, and thus that the gas has been accreted through a recent merger with a lower mass companion. We calculate the implied minor companion masses and gas fractions, finding a median predicted stellar mass ratio of ~40:1. The minor companion likely had masses between ~10^7 - 10^10 Msun. The implied merger mass ratios are consistent with the expectation for low redshift gas-rich mergers from simulations. We then go on to present evidence that (no matter which star-formation rate indicator is used) our sample objects have very low star-formation efficiencies (star-formation rate per unit gas mass), lower even than the early-type galaxies from ATLAS3D which already show a suppression. This suggests that minor mergers can actually suppress star-formation activity. We discuss mechanisms that could cause such a suppression, include dynamical effects induced by the minor merger.Peer reviewe
- …