2,017 research outputs found
Herschel ATLAS: The cosmic star formation history of quasar host galaxies
We present a derivation of the star formation rate per comoving volume of quasar host galaxies, derived from stacking analyses of far-infrared to mm-wave photometry of quasars with redshifts 0 I_(AB) > -32 We use the science demonstration observations of the first ~16âdeg^2 from the Herschel Astrophysical Terahertz Large Area Survey (H-ATLAS) in which there are 240 quasars from the Sloan Digital Sky Survey (SDSS) and a further 171 from the 2dF-SDSS LRG and QSO (2SLAQ) survey. We supplement this data with a compilation of data from IRAS, ISO, Spitzer, SCUBA and MAMBO. H-ATLAS alone statistically detects the quasars in its survey area at >5Ï at 250,350 and 500âÎŒm. From the compilation as a whole we find striking evidence of downsizing in quasar host galaxy formation: low-luminosity quasars with absolute magnitudes in the range -22 > I_(AB) > -24 have a comoving star formation rate (derived from 100âÎŒm rest-frame luminosities) peaking between redshifts of 1 and 2, while high-luminosity quasars with I_(AB) I_(AB) > -24 quasars evolves as (1 + z)^(2.3±0.7) at z I_(AB) > -28. We tentatively interpret this as a combination of a declining major merger rate with time and gas consumption reducing fuel for both black hole accretion and star formation
From respect to reburial: negotiating pagan interest in prehistoric human remains in Britain, through the Avebury consultation
The recent Avebury Consultation on reburial has drawn considerable public and professional attention to the issue of pagan calls for respect towards the care of human remains. Our work has pointed to the importance of archaeologists and others engaging seriously and respectfully with pagans as significant stakeholders in our heritage. The Avebury Reburial Consultation suggests this dialogue is increasing in strength, but we identify problems in the process. We focus here on approaches to the prehistoric dead and worldviews enabling communication from which calls or âclaimsâ for the reburial of prehistoric pagan human remains, versus their retention for scientific study, are articulated; frameworks for assessing and adjudicating such âclaimsâ; and implications for the interest groups concerned. We argue that room must be made for philosophical debate and the emotional and spiritual views of pagans, in order to improve dialogue, develop common ground, and enable participatory decision-making and situational pragmatism
Detecting gravitational lensing cosmic shear from samples of several galaxies using two-dimensional spectral imaging
Studies of weak gravitational lensing by large-scale structures require the
measurement of the distortions introduced to the shapes of distant galaxies at
the few percent level by anisotropic light deflection along the line of sight.
To detect this signal on 1-10 arcmin scales in a particular field, accurate
measurements of the correlations between the shapes of order 1000-10000
galaxies are required. This large-scale averaging is required to accommodate
the unknown intrinsic shapes of the background galaxies, even with careful
removal of systematic effects. Here an alternative is discussed. If it is
possible to measure accurately the detailed dynamical structure of the
background galaxies, in particular rotating disks, then it should be possible
to measure directly the cosmic shear distortion, as it generally leads to a
non-self-consistent rotation curve. Narrow spectral lines and excellent
two-dimensional spatial resolution are required. The ideal lines and telescope
are CO rotational transitions and the Atacama Large Millimeter Array (ALMA)
respectively.Comment: 12 pages, 4 figures, Expected to appear in ApJ Letters Vol. 570, 10
May 2002. Replaced with final proof version correcting minor typo
Surgical Aspects of Dissecting Aortic Aneurysms
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/66511/2/10.1177_000331975400500313.pd
Pasts and pagan practices: moving beyond Stonehenge
Theorizing the past is not restricted to archaeology and interpretations of 'past' both influence and are themselves constituted within politicized understandings of self, community and in certain instances, spirituality. 'The past in the imagination of the present' is appropriated, variously, to give meaning to the present or to justify actions and interpret experiences. Summer solstice at Stonehenge, with an estimated 21,000 celebrants in 2005, is only the most publicized appropriation (by pagans and other adherents of alternative spirituality and partying) of a 'sacred site'; and conflicts and negotiations occurring throughout Britain are represented in popular and academic presentations of this 'icon of Britishness'. This paper presents work from the Sacred Sites, Contested Rites/Rights Project (http://www.sacredsites.org.uk) project, a collaboration of archaeology and anthropology informed by pagan and alternative approaches and standpoints investigating and theorizing discourse and practice of heritage management and pagan site users. Whether in negotiations around the Stonehenge solstice access or in dealing with numerous other sites, boundaries between groups or discourses are not clearly drawn - discursive communities merge and re-emerge. But clearly 'past' and 'site' are increasingly important within today's Britain, even as television archaeology increases its following, and pagan numbers continue to grow.</p
The Scatter in the Relationship between Redshift and the Radio-to-Submm Spectral Index
We derive the scatter in the relationship between redshift and radio-to-submm
spectral index, alpha^{350}_{1.4}, using the observed spectral energy
distributions of 17 low redshift star forming galaxies. A mean galaxy model is
derived, along with the rms scatter in alpha^{350}_{1.4}. The scatter is
roughly constant with redshift. Constant rms scatter, combined with the
flattening of the mean alpha^{350}_{1.4} -- z relationship with increasing
redshift, leads to increasing uncertainty for redshift estimates at high
redshifts. Normalizing by the dust temperature in the manner proposed by Blain
decreases the scatter in alpha^{350}_{1.4} for most of the sample, but does not
remove outliers, and free-free absorption at rest frequencies above 1.4 GHz is
not likely to be a dominant cause for scatter in the alpha^{350}_{1.4} -- z
relationship. We re-derive the cumulative redshift distribution of the 14 field
galaxies in a recent submm and radio source sample of Smail et al.. The most
likely median redshift for the distribution is 2.7, with a conservative lower
limit of z = 2, as was also found by Smail et al. based on the original
alpha^{350}_{1.4} -- z models. The normalization and shape of the redshift
distribution for the faint submm sources are consistent with those expected for
forming elliptical galaxies.Comment: Added Erratum, standard AAS LATEX forma
The very bright SCUBA galaxy count: looking for SCUBA galaxies with the Mexican Hat Wavelet
We present the results of a search for bright high-redshift galaxies in two
large SCUBA scan-maps of Galactic regions. A Mexican Hat Wavelet technique was
used to locate point sources in these maps, which suffer high foreground
contamination as well as typical scan-map noise signatures. A catalogue of
point source objects was selected and observed again in the submillimetre
continuum, and in HCO+ (3->2) at zero redshift to rule out Galactic sources. No
extragalactic sources were found. Simulations show that the survey was
sensitive to sources with fluxes > 50 mJy, depending on the local background.
These simulations result in upper limits on the 850-micron counts of SCUBA
galaxies of 53 per square degree at 50 mJy and 2.9 per square degree at 100
mJy.Comment: Accepted by MNRA
Phosphorylation of MCPH1 isoforms during mitosis followed by isoformâspecific degradation by APC/CâCDH1
Microcephalinâ1 (MCPH1) exists as 2 isoforms that regulate cyclinâdependent kinaseâ1 activation and chromosome condensation during mitosis, with MCPH1 mutations causing primary microcephaly. MCPH1 is also a tumor suppressor protein, with roles in DNA damage repair/checkpoints. Despite these important roles, there is little information on the cellular regulation of MCPH1. We show that both MCPH1 isoforms are phosphorylated in a cyclinâdependent kinaseâ1âdependent manner in mitosis and identify several novel phosphorylation sites. Upon mitotic exit, MCPH1 isoforms were degraded by the anaphaseâpromoting complex/cyclosomeâCDH1 E3 ligase complex. Anaphaseâpromoting complex/cyclosomeâCDH1 target proteins generally have DâBox or KENâBox degron sequences. We found that MCPH1 isoforms are degraded independently, with the long isoform degradation being DâBox dependent, whereas the short isoform was KENâBox dependent. Our research identifies several novel mechanisms regulating MCPH1 and also highlights important issues with several commercial MCPH1 antibodies, with potential relevance to previously published data.âMeyer, S. K., Dunn, M., Vidler, D. S., Porter, A., Blain, P. G., Jowsey, P. A. Phosphorylation of MCPH1 isoforms during mitosis followed by isoformâspecific degradation by APC/CâCDH1. FASEB J. 33, 2796â2808 (2019). www.fasebj.or
Dissolved iron distribution in the tropical and sub tropical south eastern Pacific
International audienceDissolved iron (DFe) distributions (Fe:P (PO43-) we show that DFe was in deficit compared to PO43- resulting from the remineralisation of organic matter. This suggests that the Marquesas islands and the surrounding plateau are not a significant source of DFe. In the gyre, DFe concentrations in the upper 350 m water column were around 0.1 nM and the ferricline was located well below the nitracline. These low concentrations reflect the low input of DFe from the atmosphere, from the ventilation of the upper thermocline with water containing low DFe, and from the low biological activity within in this ultra oligotrophic gyre
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