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Search Results: 1 - 10 of 11221 matches for " Matthew Hayes "
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John Urry, Climate Change and Society.
Matthew Hayes
The Canadian Journal of Sociology , 2011,
Abstract: Book Review
Lyman alpha Emitting Galaxies in the Nearby Universe
Matthew Hayes
Physics , 2015, DOI: 10.1017/pasa.2015.25
Abstract: The Lya emission line of HI is intrinsically the brightest feature in the spectrum of astrophysical nebulae, making it a very attractive observational tool with which to survey galaxies. Moreover as a UV resonance line, Lya possesses several unique characteristics that make it useful to study the ISM and ionizing stellar population at all cosmic epochs. In this review I present a summary of Lya observations of galaxies in the nearby universe. At UV magnitudes reachable with current facilities, only ~5% of the local galaxy population shows a Lya equivalent width (EW_Lya) that exceeds 20\AA. This fraction increases dramatically at higher z, but only in the local universe can we study galaxies in detail and assemble unprecedented multi-wavelength datasets. I discuss many local Lya observations, showing that when galaxies show net Lya emission, they ubiquitously produce large halos of scattered Lya, that dominate the integrated luminosity. We discuss how global EW_Lya and the Lya escape fraction (fescLya) are higher (EW_Lya >~ 20\AA\ and fescLya> 10%) in galaxies that represent the less massive and younger end of the distributions for local objects. This is connected with various properties, such that Lya-emitters have lower metallicities (median value of 12+log(O/H) ~ 8.1) and dust reddening. However, the presence of galactic outflows is also vital to Doppler shift the Lya line out of resonance with the HI, as high EW_Lya is found only among galaxies with winds faster than ~50km/s. The evidence is then assembled into a coherent picture, and the requirement for star formation driven feedback is discussed in the context of an evolutionary sequence where the ISM is accelerated and/or subject to fluid instabilities, which reduce the scattering of Lya. Concluding remarks take the form of perspectives upon the most pressing questions that can be answered by observation.
A Model-Based Clustering Method for Genomic Structural Variant Prediction and Genotyping Using Paired-End Sequencing Data
Matthew Hayes, Yoon Soo Pyon, Jing Li
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0052881
Abstract: Structural variation (SV) has been reported to be associated with numerous diseases such as cancer. With the advent of next generation sequencing (NGS) technologies, various types of SV can be potentially identified. We propose a model based clustering approach utilizing a set of features defined for each type of SV events. Our method, termed SVMiner, not only provides a probability score for each candidate, but also predicts the heterozygosity of genomic deletions. Extensive experiments on genome-wide deep sequencing data have demonstrated that SVMiner is robust against the variability of a single cluster feature, and it significantly outperforms several commonly used SV detection programs. SVMiner can be downloaded from http://cbc.case.edu/svminer/.
The H-alpha luminosity function at redshift 2.2: A new determination using VLT/HAWK-I
Matthew Hayes,Daniel Schaerer,Goran Ostlin
Physics , 2009, DOI: 10.1051/0004-6361/200913217
Abstract: We aim to place new, strengthened constraints on the luminosity function (LF) of H-alpha emitting galaxies at redshift z=2.2, and to further constrain the instantaneous star-formation rate density of the universe (rho*). We have used the new HAWK-I instrument at ESO-VLT to obtain extremely deep narrow-band (line; NB2090) and broad-band (continuum; Ks) imaging observations. The target field is in the GOODS-South, providing us with a rich multi-wavelength auxiliary data set, which we utilise for redshift confirmation and to estimate dust content. We use this new data to measure the faint-end slope (alpha) of LF(H-alpha) with unprecedented precision. The data are well fit by a Schechter function and also a single power-law, yielding alpha=(-1.72 +/- 0.20) and (-1.77 +/- 0.21), respectively. Thus we are able to confirm the steepening of alpha from low- to high-z predicted by a number of authors and observed at other wavelengths. We combine our LF data-points with those from a much shallower but wider survey at z=2.2 (Geach et al. 2008), constructing a LF spanning a factor of 50 in luminosity. Re-fitting the Schechter parameters, we obtain log L*=(43.07+/-0.22)erg s^-1 ; log phi*=(-3.45+/-0.52)Mpc^-3 ; alpha=(-1.60+/-0.15). We integrate over LF(Halpha) and apply a correction for dust attenuation to determine the instantaneous cosmic star-formation rate density at z=2 without assuming alpha or extrapolating it from lower-z. Our measurement of rho* is (0.215+/-0.090) Msun yr^-1 Mpc^-3, integrated over a range of 37
Central Powering of the Largest Lyman-alpha Nebula is Revealed by Polarized Radiation
Matthew Hayes,Claudia Scarlata,Brian Siana
Physics , 2011, DOI: 10.1038/nature10320
Abstract: High-redshift Lyman-alpha blobs are extended, luminous, but rare structures that appear to be associated with the highest peaks in the matter density of the Universe. Their energy output and morphology are similar to powerful radio galaxies, but the source of the luminosity is unclear. Some blobs are associated with ultraviolet or infrared bright galaxies, suggesting an extreme starburst event or accretion onto a central black hole. Another possibility is gas that is shock excited by supernovae. However some blobs are not associated with galaxies, and may instead be heated by gas falling into a dark matter halo. The polarization of the Ly-alpha emission can in principle distinguish between these options, but a previous attempt to detect this signature returned a null detection. Here we report on the detection of polarized Ly-alpha from the blob LAB1. Although the central region shows no measurable polarization, the polarized fraction (P) increases to ~20 per cent at a radius of 45 kpc, forming an almost complete polarized ring. The detection of polarized radiation is inconsistent with the in situ production of Ly-alpha photons, and we conclude that they must have been produced in the galaxies hosted within the nebula, and re-scattered by neutral hydrogen.
Annexin A2 at the Interface of Actin and Membrane Dynamics: A Focus on Its Roles in Endocytosis and Cell Polarization
Adam G. Grieve,Stephen E. Moss,Matthew J. Hayes
International Journal of Cell Biology , 2012, DOI: 10.1155/2012/852430
Abstract: Annexins are a family of calcium- and phospholipid-binding proteins found in nearly all eukaryotes. They are structurally highly conserved and have been implicated in a wide range of cellular activities. In this paper, we focus on Annexin A2 (AnxA2). Altered expression of this protein has been identified in a wide variety of cancers, has also been found on the HIV particle, and has been implicated in the maturation of the virus. Recently, it has also been shown to have an important role in the establishment of normal apical polarity in epithelial cells. We synthesize here the known biochemical properties of this protein and the extensive literature concerning its involvement in the endocytic pathway. We stress the importance of AnxA2 as a platform for actin remodeling in the vicinity of dynamic cellular membranes, in the hope that this may shed light on the normal functions of the protein and its contribution to disease. 1. The Annexins A number of reviews have already been written on this large family of proteins. For the sake of brevity, we can only cursorily describe these roles. The annexins are found in all multicellular and some single-cell eukaryotes. They are a highly conserved family of calcium and phospholipid-binding proteins usually comprising four repeats of the characteristic alpha-helical-rich endonexin fold and an N-terminal domain that is unique to each annexin [1–5], Figure 1. Individual annexins tend to show restricted expression in particular cell types, the so-called “annexin fingerprint”, and where they are expressed; they tend to be highly abundant. Figure 1: Structure of AnxA2. (a) Space filling view of AnxA2 (colours indicate hydrophobicity) looking “down” onto the membrane-binding surface of the molecule. One endonexin fold, repeated four times in AnxA2, is highlighted in yellow. (b) “Cartoon” of AnxA2 showing the molecule from the side. The protein is almost entirely made up of alpha-helices. The position of coordinated calcium atoms is shown in green. In different phyla, they have evolved to perform a variety of cellular functions but all retain a set of core properties [2–7]. They bind dibasic metal ions (usually calcium) and associate with charged phospholipids. They sometimes form oligomers, which can associate into high-order pseudocrystalline arrays on the surface of membranes, somewhat reminiscent of viral capsids [1]. In other cases, they have been suggested to insert into membranes, potentially forming pores or indeed to pass through the membrane entirely to act as an extracellular protein, with functions that may
The Extremely Young Star Cluster Population In Haro 11
Angela Adamo,G?ran ?stlin,Erik Zackrisson,Matthew Hayes
Physics , 2009,
Abstract: We have performed a deep multi-band photometric analysis of the star cluster population of Haro 11. This starburst galaxy (log L_FUV = 10.3 L_sun) is considered a nearby analogue of Lyman break galaxies (LBGs) at high redshift. The study of the numerous star clusters in the systems is an effective way to investigate the formation and evolution of the starburst phase. In fact, the SED fitting models have revealed a surprisingly young star cluster population, with ages between 0.5 and 40 Myr, and estimated masses between 10^3 and 10^7 solar masses. An independent age estimation has been done with the EW(Halpha) analysis of each cluster. This last analysis has confirmed the young ages of the clusters. We noticed that the clusters with ages between 1 and 10 Myr show a flux excess in H (NIC3/F160W) and/or I (WFPC2/F814W) bands with respect to the evolutionary models. Once more Haro 11 represents a challenge to our understanding.
Tracing the star formation history of three Blue Compact galaxies through the analysis of their star clusters
Angela Adamo,G?ran ?stlin,Erik Zackrisson,Matthew Hayes
Physics , 2009,
Abstract: We present preliminary results from a study of the compact star cluster populations in three local luminous blue compact galaxies: ESO 185-IG 013, ESO 350-IG 038 (a.k.a. Haro 11), and MRK 930. These systems show peculiar morphologies and the presence of hundreds of SCs that have been produced by the past, recent, and/or current starburst phases. We use a complete set of HST images ranging from the UV to IR for each galaxy. Deep images in V (WFPC2/f606w) and I (WFPC2/f814w) are used to capture most of the star cluster candidates up to the old ones (fainter) which have had, in the past, less possibility to be detected. The other bands are used in the SED fitting technique for constraining ages and masses. Our goals are to investigate the evolution of these three blue compact galaxies and the star cluster formation impact on their star formation history.
Escape of Lyman continuum radiation from local galaxies - Detection of leakage from the young starburst Tol 1247-232
Elisabet Leitet,Nils Bergvall,Matthew Hayes,Staffan Linné,Erik Zackrisson
Physics , 2013, DOI: 10.1051/0004-6361/201118370
Abstract: The escape fraction of hydrogen ionizing photons (f_esc) from galaxies has been suggested to be evolving with time, but the picture is far from clear. While evidence for significant escape fractions has been found at high redshifts in several studies, the picture looks different in the more nearby universe. Here, we apply a new background subtraction routine on archival data from the Far Ultraviolet Spectroscopic Explorer (FUSE), in order to study local galaxies in search for possible Lyman Continuum (LyC) leakage. In the process, for the first time a stacked spectrum in the LyC is produced for local galaxies. With this small sample, we also make a more tentative approach to look for possible correlations between f_esc and physical parameters such as internal absorption E(B-V)_i, mass, H I mass, specific star formation rate (SSFR), metallicity, and Ly-alpha emission. Eight star forming galaxies with redshifts z > 0.015 from the FUSE archive were re-examined. Also, a sub-sample of an additional four galaxies with lower redshifts were included, for which the escape fraction was estimated from residual flux in the low ionization interstellar C II(1036{\AA}) line. Out of the eight galaxies, only one was found to have significant LyC leakage, Tol 1247-232 (S/N=5.2). This is the second detection of a leaking galaxy in the local universe. We find an absolute escape fraction for Tol 1247-232 of f_esc = 2.4(+0.9/-0.8) %. The stacked sample show an excess in the LyC with f_esc = 1.4(+0.6/-0.5) %, but we note that there might be important selection biases involved. With the small sample, we suggest a possible trend for higher f_esc with lower mass and with enhanced SSFR. None of the galaxies with high values of E(B-V)_i were found to show any sign of leakage.
On the origin of the red excess in very young super star clusters: the case of SBS 0335-052E
Angela Adamo,Erik Zackrisson,Goeran Ostlin,Matthew Hayes
Physics , 2010, DOI: 10.1088/0004-637X/725/2/1620
Abstract: The spectral energy distribution analysis of very young unresolved star clusters challenges our understanding of the cluster formation process. Studies of resolved massive clusters in the Milky Way and in the nearby Magellanic Clouds show us that the contribution from photoionized gas is very important during the first Myr of cluster evolution. We present our models which include both a self-consistent treatment of the photoionized gas and the stellar continuum and quantify the impact of such nebular component on the total flux of young unresolved star clusters. A comparison with other available models is considered. The very young star clusters in the SBS 0335-052E dwarf starburst galaxy are used as a test for our models. Due to the low metallicity of the galactic medium our models predict a longer lasted nebular phase which contributes between 10-40% of the total near infrared (NIR) fluxes at around 10 Myr. We propose thus a possible solution for the observed flux excess in the 6 bright super star clusters of SBS 0335-052E. Reines et al. showed that the observed cluster fluxes, in the red-optical and NIR range, sit irreconcilably above the provided stellar continuum models. We find that in the age range estimated from the H_alpha emission we can explain the red excess in all the 6 super star clusters as due to nebular emission, which at cluster ages around 10 Myr still affects the NIR wavebands substantially.
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