924 research outputs found
The SCUBA Local Universe Galaxy Survey
The SCUBA local universe galaxy survey is the first systematic survey of the
local universe at submillimetre wavelengths. We have observed ~200 galaxies
from the IRAS bright galaxy catalogue and the CfA optical redshift survey. The
IRAS sample showed that our estimate of the luminosity function was potentially
biased if a cold population of galaxies existed which would not have appeared
in the IRAS BGS but would have been detected in a SCUBA blind survey. Here we
present preliminary results from the optically selected sample which suggest
that this is indeed the case.Comment: 2 pages, 2 figs, proceedings from Euro-conference on galaxy evolution
held in La Reunion, 200
The role of p38 MAPK and its substrates in neuronal plasticity and neurodegenerative disease
A significant amount of evidence suggests that the p38-mitogen-activated protein kinase (MAPK) signalling cascade plays a crucial role in synaptic plasticity and in neurodegenerative diseases. In this review we will discuss the cellular localisation and activation of p38 MAPK and the recent advances on the molecular and cellular mechanisms of its substrates: MAPKAPK 2 (MK2) and tau protein. In particular we will focus our attention on the understanding of the p38 MAPK-MK2 and p38 MAPK-tau activation axis in controlling neuroinflammation, actin remodelling and tau hyperphosphorylation, processes that are thought to be involved in normal ageing as well as in neurodegenerative diseases. We will also give some insight into how elucidating the precise role of p38 MAPK-MK2 and p38 MAPK-tau signalling cascades may help to identify novel therapeutic targets to slow down the symptoms observed in neurodegenerative diseases such as Alzheimer's and Parkinson's disease
Candidate High Redshift and Primeval Galaxies in Hubble Deep Field South
We present the results of colour selection of candidate high redshift
galaxies in Hubble Deep Field South (HDF-S) using the Lyman dropout scheme. The
HDF-S data we discuss were taken in a number of different filters extending
from the near--UV (F300W) to the infrared (F222M) in two different fields. This
allows us to select candidates with redshifts from z~3 to z~12. We find 15
candidate z~3 objects (F300W dropouts), 1 candidate z~4 object (F450W dropout)
and 16 candidate z5 objects (F606W dropouts) in the ~ 4.7 arcmin^2 WFPC-2
field, 4 candidate z~6 (optical dropouts) and 1 candidate z~8 (F110W dropout)
in the 0.84 arcmin^2 NICMOS-3 field. No F160W dropouts are found (z~12). We
compare our selection technique with existing data for HDF-North and discuss
alternative interpretations of the objects. We conclude that there are a number
of lower redshift interlopers in the selections, including one previously
identified object (Treu et al. 1998), and reject those objects most likely to
be foreground contaminants. Even after this we conclude that the F606W dropout
list is likely to still contain substantial foreground contamination. The lack
of candidate very high redshift UV-luminous galaxies supports earlier
conclusions by Lanzetta et al. (1998). We discuss the morphologies and
luminosity functions of the high redshift objects, and their cosmological
implications.Comment: Accepted for publication in MNRA
Mapping the interstellar medium in galaxies with Herschel/SPIRE
The standard method of mapping the interstellar medium in a galaxy, by observing the molecular gas in the CO 1-0 line and the atomic gas in the 21-cm line, is largely limited with current telescopes to galaxies in the nearby universe. In this letter, we use SPIRE observations of the galaxies
M99 and M100 to explore the alternative approach of mapping the interstellar medium using the continuum emission from the dust. We have compared the methods by measuring the relationship between the star-formation rate and the surface density of gas in the galaxies using both
methods. We find the two methods give relationships with a similar dispersion, confirming that observing the continuum emission from the dust is a promising method of mapping the interstellar medium in galaxies
The SCUBA Local Universe Galaxy Survey I: First Measurements of the Submillimetre Luminosity and Dust Mass Functions
We have used SCUBA to observe a complete sample of 104 galaxies selected at
60 microns from the IRAS BGS and we present here the 850 micron measurements.
Fitting the 60,100 and 850 micron fluxes with a single temperature dust model
gives the sample mean temperature T=36 K and beta = 1.3. We do not rule out the
possibility of dust which is colder than this, if a 20 K component was present
then our dust masses would increase by factor 1.5-3. We present the first
measurements of the luminosity and dust mass functions, which were well fitted
by Schechter functions (unlike those 60 microns). We have correlated many
global galaxy properties with the submillimetre and find that there is a
tendancy for less optically luminous galaxies to contain warmer dust and have
greater star formation efficiencies (cf. Young 1999). The average gas-to-dust
ratio for the sample is 581 +/- 43 (using both atomic and molecular hydrogen),
significantly higher than the Galactic value of 160. We believe this
discrepancy is due to a cold dust component at T < 20 K. There is a suprisingly
tight correlation between dust mass and the mass of molecular hydrogen as
estimated from CO measurements, with an intrinsic scatter of ~50%.Comment: 24 pages, 15 figures, 8 tables, accepted for publication in MNRA
Smoking Supernovae
The question "Are supernovae important sources of dust?" is a contentious one. Observations with the Infrared Astronomical Satellite (IRAS) and the Infrared Space Observatory (ISO) only detected very small amounts of hot dust in supernova remnants. Here, we review observations of two young Galactic remnants with the Submillimetre Common User Bolometer Array (SCUBA), which imply that large quantities of dust are produced by supernovae. The association of dust with the Cassiopeia A remnant is in question due to the contamination of foreground material. In this article, we compare the emission from cold dust with CO emission towards Kepler's supernova remnant. We detect very little CO at the location of the submillimetre peaks. A comparison of masses from the CO and the dust clouds are made, and we estimate the 3 sigma upper limit on the gas-to-dust ratios to range from 25 - 65 suggesting that we cannot yet rule out freshly-formed or swept up circumstellar dust in Kepler's supernova remnant
The Canada-UK Deep Submillimetre Survey: First Submillimetre Images, the Source Counts, and Resolution of the Background
We present the first results of a deep unbiased submillimetre survey carried
out at 450 and 850 microns. We detected 12 sources at 850 microns, giving a
surface density of sources with 850-micron flux densities > 2.8mJy of of
0.49+-0.16 per square arcmin. The sources constitute 20-30% of the background
radiation at 850 microns and thus a significant fraction of the entire
background radiation produced by stars. This implies, through the connection
between metallicity and background radiation, that a significant fraction of
all the stars that have ever been formed were formed in objects like those
detected here. The combination of their large contribution to the background
radiation and their extreme bolometric luminosities make these objects
excellent candidates for being proto-ellipticals. Optical astronomers have
recently shown that the UV-luminosity density of the universe increases by a
factor of about 10 between z=0 and z=1 and then decreases again at higher
redshifts. Using the results of a parallel submillimetre survey of the local
universe, we show that both the submillimetre source density and background can
be explained if the submillimetre luminosity density evolves in a similar way
to the UV-luminosity density. Thus, if these sources are ellipticals in the
process of formation, they may be forming at relatively modest redshifts.Comment: 8 pages (LATEX), 6 postscript figures, submitted to ApJ Letter
High spatial resolution observations of CUDSS14A: a SCUBA-selected ultraluminous galaxy at high redshift
The definitive version is available at www.blackwell-synergy.com '. Copyright Blackwell Publishing DOI : 10.1046/j.1365-8711.2000.03822.xWe present a high-resolutionmillimetre interferometric image of the brightest SCUBA- selected galaxy from the Canada-UK deep SCUBA survey (CUDSS). We make a very clear detection at 1.3 mm, but fail to resolve any structure in the source.Peer reviewe
A census of metals at high and low redshifts and the connection between submillimetre sources and spheroid formation
Deep surveys in many wavebands have shown that the rate at which stars were
forming was at least a factor of 10 higher at z > 1 than today. Heavy elements
(metals) are produced by stars, and the star formation history deduced by these
surveys implies that a significant fraction of metals in the universe today
should already exist at z~2-3. However, only 10% of the total metals expected
to exist at this epoch have so far been accounted for (in DLAs and the Lyman
forest). In this paper, we use the results of submillimetre surveys of the
local and high redshift universe to show that there was much more dust in
galaxies in the past. We find that a large proportion of the missing metals are
traced by this dust, bringing the metals implied from the star formation
history and observations into agreement. We also show that the observed
distribution of dust masses at high redshift can be reproduced remarkably well
by a simple model for the evolution of dust in spheroids, suggesting that the
descendants of the dusty galaxies found in the deep submm surveys are the
relatively dust-free spiral bulges and ellipticals in the universe today.Comment: 11 pages, 6 figures, MNRAS in pres
The Canada-UK Deep Submillimetre Survey: The Survey of the 14-hour field
We have used SCUBA to survey an area of 50 square arcmin, detecting 19
sources down to a 3sigma sensitivity limit of 3.5 mJy at 850 microns. We have
used Monte-Carlo simulations to assess the effect of source confusion and noise
on the SCUBA fluxes and positions, finding that the fluxes of sources in the
SCUBA surveys are significantly biased upwards and that the fraction of the 850
micron background that has been resolved by SCUBA has been overestimated. The
radio/submillmetre flux ratios imply that the dust in these galaxies is being
heated by young stars rather than AGN. We have used simple evolution models
based on our parallel SCUBA survey of the local universe to address the major
questions about the SCUBA sources: (1) what fraction of the star formation at
high redshift is hidden by dust? (2) Does the submillimetre luminosity density
reach a maximum at some redshift? (3) If the SCUBA sources are
proto-ellipticals, when exactly did ellipticals form? However, we show that the
observations are not yet good enough for definitive answers to these questions.
There are, for example, acceptable models in which 10 times as much
high-redshift star formation is hidden by dust as is seen at optical
wavelengths, but also acceptable ones in which the amount of hidden star
formation is less than that seen optically. There are acceptable models in
which very little star formation occurred before a redshift of three (as might
be expected in models of hierarchical galaxy formation), but also ones in which
30% of the stars have formed by this redshift. The key to answering these
questions are measurements of the dust temperatures and redshifts of the SCUBA
sources.Comment: 41 pages (latex), 17 postscript figures, to appear in the November
issue of the Astronomical Journa
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