3,511 research outputs found
The local supermassive black hole mass density: corrections for dependencies on the Hubble constant
We have investigated past measurements of the local supermassive black hole
mass density, correcting for hitherto unknown dependencies on the Hubble
constant, which, in some cases, had led to an underestimation of the mass
density by factors of ~2. Correcting for this, we note that the majority of
past studies yield a local supermassive black hole mas density that is
consistent with the range 4.4-5.9 x 10^5 f(H_0) M_Sun / Mpc^3 (when using H_0 =
70 km/s/Mpc). In addition, we address a number of ways in which these past
estimates can be further developed. In particular, we tabulate realistic
bulge-to-total flux ratios which can be used to estimate the luminosity of
bulges and subsequently their central black hole masses.Comment: MNRAS, accepte
Developing a ‘One Health’ Nipah virus vaccine to protect animal and public health
An expanding human population and the concomitant increase in demand for animal protein has led to the use of previously unused habitable land and disruption of ecosystems. Increased human-livestock-wildlife interactions has led to an increase in virus spillover events from wildlife reservoirs, which in turn has elevated the risk of epidemics of new and emerging zoonotic diseases. ‘One Health’ recognises that human, animal, and environmental health are tightly interconnected; an initiative that is righfully gaining more attention in the post-COVID-19 world. Vaccination is a powerful strategy to prevent and control viral outbreaks, as exemplified by the COVID-19 pandemic. Moreover, the vaccination of amplifying intermediate animal hosts provides an effective way to further protect human health. To support efforts to develop vaccines to combat emerging viral zoonoses, we are developing a Nipah virus (NiV) vaccine for use in pigs, which would reduce the risk that NiV poses to the Asian pig industry, livestock keepers and public health. Pig-to-human transmission was responsible for the first and most severe NiV outbreak. This outbreak caused severe and lasting economic costs to the Malaysian pig industry. Despite the threat NiV poses to some of the most pig dense regions of the world, no vaccines are currently available. We have therefore evaluated the immunogenicity of recombinant NiV glycoprotein (G or F) based vaccine candidates delivered as protein subunits or by viral or mRNA vectors in pigs. Three vaccine candidates have been evaluated for efficacy and shown to confer a high degree of protection following a prime-boost regimen. These are now being evaluated under field conditions in Bangladesh. In addition to providing a platform for the further development of a NiV vaccine for pigs, we hope these studies will also benefit ongoing human vaccine development efforts
The Millennium Galaxy Catalogue: The nearby supermassive black hole mass function
We highlight the correlation between a galaxy's supermassive black hole mass
and the Sersic-index of the host spheroid or bulge component. From our
bulge-disk decompositions of 10 095 galaxies, drawn from the Millennium Galaxy
Catalogue, we construct the local (z < 0.18) mass function of supermassive
black holes. We compare our results to those of McLure & Dunlop (2004) and
conclude that the mass density of supermassive black holes may be marginally
higher than previously supposed. This increase is predominantly due to the
inclusion of low mass and later-type bulges. More details will be presented in
a forthcoming paper.Comment: Contributed article to the Fabulous Destiny of Galaxies meetin
A concise reference to (projected) Sersic R^{1/n} quantities, including Concentration, Profile Slopes, Petrosian indices, and Kron Magnitudes
Given the growing use of Sersic's (1963, 1968) R^{1/n} model for describing
the stellar distributions in galaxies, and the lack of any single reference
that provides the various associated mathematical expressions, we have
endeavoured to compile such a resource here. We present the standard intensity
profile, and its various guises such as the luminosity, surface-brightness, and
aperture-magnitude profile. Expressions to transform the effective surface
brightness into the mean effective and central surface brightness are also
given, as is the expression to transform between effective radii and
exponential scale-lengths. We additionally provide expressions for deriving the
`concentration' of an R^{1/n} profile, and two useful equations for the
logarithmic slope of the light-profile are given. Petrosian radii and fluxes
are also derived for a range of Sersic profiles and compared with the effective
radii and total flux. Similarly, expressions to obtain Kron radii and fluxes
are presented as a function of the Sersic index n and the number of effective
radii sampled. Illustrative figures are provided throughout. Finally, the
core-Sersic model, consisting of an inner power-law and an outer-Sersic
function, is presented.Comment: 11 pages. To appear in PAS
Statistics of Lead Changes in Popularity-Driven Systems
We study statistical properties of the highest degree, or most popular, nodes
in growing networks. We show that the number of lead changes increases
logarithmically with network size N, independent of the details of the growth
mechanism. The probability that the first node retains the lead approaches a
finite constant for popularity-driven growth, and decays as N^{-phi}(ln
N)^{-1/2}, with phi=0.08607..., for growth with no popularity bias.Comment: 4 pages, 4 figures, 2 column revtex format. Minor changes in response
to referee comments. For publication in PR
Vaccine Development for Nipah Virus Infection in Pigs
Nipah virus (NiV) causes a severe and often fatal neurological disease in humans. Whilst fruit bats are considered the natural reservoir, NiV also infects pigs and may cause an unapparent or mild disease. Direct pig-to-human transmission was responsible for the first and still most devastating NiV outbreaks in Malaysia and Singapore in 1998–99, with nearly 300 human cases and over 100 fatalities. Pigs can therefore play a key role in the epidemiology of NiV by acting as an “amplifying” host. The outbreak in Singapore ended with the prohibition of pig imports from Malaysia and the Malaysian outbreak was ended by culling 45% of the country's pig population with costs exceeding US$500 million. Despite the importance of NiV as an emerging disease with the potential for pandemic, no vaccines, or therapeutics are currently approved for human or livestock use. In this mini-review, we will discuss current knowledge of NiV infection in pigs; our ongoing work to develop a NiV vaccine for use in pigs; and the pig as a model to support human vaccine development
The supermassive black hole mass - S\'ersic index relations for bulges and elliptical galaxies
Scaling relations between supermassive black hole mass, M_BH, and host galaxy
properties are a powerful instrument for studying their coevolution. A complete
picture involving all of the black hole scaling relations, in which each
relation is consistent with the others, is necessary to fully understand the
black hole-galaxy connection. The relation between M_BH and the central light
concentration of the surrounding bulge, quantified by the S\'ersic index n, may
be one of the simplest and strongest such relations, requiring only
uncalibrated galaxy images. We have conducted a census of literature S\'ersic
index measurements for a sample of 54 local galaxies with directly measured
M_BH values. We find a clear M_BH - n relation, despite an appreciable level of
scatter due to the heterogeneity of the data. Given the current M_BH - L_sph
and the L_sph - n relations, we have additionally derived the expected M_BH - n
relations, which are marginally consistent at the 2 sigma level with the
observed relations. Elliptical galaxies and the bulges of disc galaxies are
each expected to follow two distinct bent M_BH - n relations due to the
S\'ersic/core-S\'ersic divide. For the same central light concentration, we
predict that M_BH in the S\'ersic bulges of disc galaxies are an order
magnitude higher than in S\'ersic elliptical galaxies if they follow the same
M_BH - L_sph relation.Comment: 12 pages, 6 figures, 5 tables, accepted for publication in MNRA
The Millennium Galaxy Catalogue: morphological classification and bimodality in the colour-concentration plane
Using 10 095 galaxies (B < 20 mag) from the Millennium Galaxy Catalogue, we
derive B-band luminosity distributions and selected bivariate brightness
distributions for the galaxy population. All subdivisions extract highly
correlated sub-sets of the galaxy population which consistently point towards
two overlapping distributions. A clear bimodality in the observed distribution
is seen in both the rest-(u-r) colour and log(n) distributions. The rest-(u-r)
colour bimodality becomes more pronounced when using the core colour as opposed
to global colour. The two populations are extremely well separated in the
colour-log(n) plane. Using our sample of 3 314 (B < 19 mag) eyeball classified
galaxies, we show that the bulge-dominated, early-type galaxies populate one
peak and the bulge-less, late-type galaxies occupy the second. The early- and
mid-type spirals sprawl across and between the peaks. This constitutes
extremely strong evidence that the fundamental way to divide the luminous
galaxy population is into bulges and discs and that the galaxy bimodality
reflects the two component nature of galaxies and not two distinct galaxy
classes. We argue that these two-components require two independent formation
mechanisms/processes and advocate early bulge formation through initial
collapse and ongoing disc formation through splashback, infall and
merging/accretion. We calculate the B-band luminosity-densities and
stellar-mass densities within each subdivision and estimate that the z ~ 0
stellar mass content in spheroids, bulges and discs is 35 +/- 2 per cent, 18
+/- 7 and 47 +/- 7 per cent respectively. [Abridged]Comment: Accepted for publication in MNRAS, 23 pages, 17 figures. Comments
welcome. MGC website is at: http://www.eso.org/~jliske/mgc
The Millennium Galaxy Catalogue: The -- derived supermassive black hole mass function
Supermassive black hole mass estimates are derived for 1743 galaxies from the
Millennium Galaxy Catalogue using the recently revised empirical relation
between supermassive black hole mass and the luminosity of the host spheroid.
The MGC spheroid luminosities are based on -bulge plus
exponential-disc decompositions. The majority of black hole masses reside
between and an upper limit of . Using
previously determined space density weights, we derive the SMBH mass function
which we fit with a Schechter-like function. Integrating the black hole mass
function over gives a supermassive black
hole mass density of (
Mpc for early-type galaxies and ( Mpc for late-type galaxies. The errors are estimated from
Monte Carlo simulations which include the uncertainties in the --
relation, the luminosity of the host spheroid and the intrinsic scatter of the
-- relation. Assuming supermassive black holes form via baryonic
accretion we find that ( per cent of the Universe's
baryons are currently locked up in supermassive black holes. This result is
consistent with our previous estimate based on the -- (S{\'e}rsic
index) relation.Comment: 10 pages, 6 figures, accepted to MNRA
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