Hubble Space Telescope imaging of the CFRS and LDSS redshift surveys - IV. Influence of mergers in the evolution of faint field galaxies from z~1

Hubble Space Telescope images of a sample of 285 galaxies with measured redshifts from the Canada-France Redshift Survey (CFRS) and Autofib-Low Dispersion Spectrograph Survey (LDSS) redshift surveys are analysed to derive the evolution of the merger fraction out to redshifts z~1. We have performed visual and machine-based merger identifications, as well as counts of bright pairs of galaxies with magnitude differences δm<=1.5mag. We find that the pair fraction increases with redshift, with up to ~20per cent of the galaxies being in physical pairs at z~0.75-1. We derive a merger fraction varying with redshift as ~(1+z)3.2+/-0.6, after correction for line-of-sight contamination, in excellent agreement with the merger fraction derived from the visual classification of mergers for which m=3.4+/-0.6. After correcting for seeing effects on the ground-based selection of survey galaxies, we conclude that the pair fraction evolves as ~(1+z)2.7+/-0.6. This implies that an average L* galaxy will have undergone 0.8-1.8 merger events from z=1 to z=0, with 0.5 to 1.2 merger events occuring in a 2-Gyr time-span at around z~0.9. This result is consistent with predictions from semi-analytical models of galaxy formation. From the simple coaddition of the observed luminosities of the galaxies in pairs, physical mergers are computed to lead to a brightening of 0.5mag for each pair on average, and a boost in star formation rate of a factor of 2, as derived from the average [Oii] equivalent widths. Mergers of galaxies are therefore contributing significantly to the evolution of both the luminosity function and luminosity density of the Universe out to z~1

Wireless Backhaul Architecture for Small Cells Deployment exploiting Q-band Frequencies

The demand of capacity in mobile communication is growing exponentially day-by-day, as the numbers of users have been increasing drastically. LTE and small cell network topologies are being hailed as the solution to this; however, the backhaul has become the real challenge. Operators have typically used different backhaul technologies for their radio access networks. Nevertheless, existing alternatives such as fibre, Digital Subscriber Line (DSL), and microwave backhaul do not provide the required CAPEX, OPEX and/or performance to meet these requirements. The SARABAND project is proposing an architecture providing multi-gigabit capacity in a cost effective manner by exploiting point to multipoint links and the Q-band spectrum. This solution provides huge advantages in CAPEX for access capillarity (last mile) when compared to FTTH and in OPEX for backhaul when compared to microwave links. This paper defines the Q-band point-tomultipoint architecture as well as the key type of nodes comprising the SARABAND architecture. Multi-beam antennas and radio parameters will also be determined to deliver segmented coverage areas and the expected capacity on each segment of the network. Finally, a techno-economic study comparing the proposed solution versus traditional point-to-point microwave backhaul will be presented.Vilar Mateo, R.; Bosshard, O.; Magne, F.; Le Fevre, A.; Martí Sendra, J. (2013). Wireless Backhaul Architecture for Small Cells Deployment exploiting Q-band Frequencies. Institute of Electrical and Electronics Engineers (IEEE). 1-11. http://hdl.handle.net/10251/63041S11

Hubble Space Telescope Imaging of the CFRS and LDSS Redshift Surveys. II. Structural Parameters and the Evolution of Disk Galaxies to Z approximately 1

Several aspects of the evolution of star-forming galaxies are studied using measures of the two-dimensional surface brightness profiles extracted from Hubble Space Telescope images of a sample of 341 faint objects selected from the CFRS and LDSS redshift surveys. The galaxies have 0 3.2 h^{-1}_{50} kpc, where the sample is most complete and where the disk and bulge decompositions are most reliable. This result, which is strengthened by inclusion of the local de Jong et al. size function, suggests that the scale lengths of typical disks cannot have grown substantially with cosmic epoch since z ~ 1, unless a corresponding number of large disks have been destroyed through merging. In addition to a roughly constant number density, the galaxies with large disks, alpha -1 >= 4 h^{-1}_{50} kpc, have, as a set, properties consistent with the idea that they are similar galaxies observed at different cosmic epochs. However, on average, they show higher B-band disk surface brightnesses, bluer overall (U-V) colors, higher [O II] lambda 3727 equivalent widths, and less regular morphologies at high redshift than at low redshift, suggesting an increase in the star formation rate by a factor of about 3 to z ~ 0.7. This is consistent with the expectations of recent models for the evolution of the disk of the Milky Way Galaxy. The evolution of the large disk galaxies with scale lengths alpha -1 >= 4 h^{-1}_{50} kpc, is probably not sufficient to account for the evolution of the overall luminosity function of galaxies over the interval 0 < z < 1, especially if Omega ~ 1. Analysis of the half-light radii of all the galaxies in the sample and construction of the bivariate size-luminosity function suggests that larger changes in the galaxy population are due to smaller galaxies, those with half-light radii around 5 h^{-1}_{50} kpc (i.e., disk scale lengths of 3 h^{-1}_{50} kpc or less)

Photometric redshifts in the SWIRE Survey

We present the SWIRE Photometric Redshift Catalogue, 1025119 redshifts of unprecedented reliability and accuracy. Our method is based on fixed galaxy and QSO templates applied to data at 0.36-4.5 mu, and on a set of 4 infrared emission templates fitted to infrared excess data at 3.6-170 mu. The code involves two passes through the data, to try to optimize recognition of AGN dust tori. A few carefully justified priors are used and are the key to supression of outliers. Extinction, A_V, is allowed as a free parameter. We use a set of 5982 spectroscopic redshifts, taken from the literature and from our own spectroscopic surveys, to analyze the performance of our method as a function of the number of photometric bands used in the solution and the reduced chi^2. For 7 photometric bands the rms value of (z_{phot}-z_{spec})/(1+z_{spec}) is 3.5%, and the percentage of catastrophic outliers is ~1%. We discuss the redshift distributions at 3.6 and 24 mu. In individual fields, structure in the redshift distribution corresponds to clusters which can be seen in the spectroscopic redshift distribution. 10% of sources in the SWIRE photometric redshift catalogue have z >2, and 4% have z>3, so this catalogue is a huge resource for high redshift galaxies. A key parameter for understanding the evolutionary status of infrared galaxies is L_{ir}/L_{opt}, which can be interpreted as the specific star-formation rate for starbursts. For dust tori around Type 1 AGN, L_{tor}/L_{opt} is a measure of the torus covering factor and we deduce a mean covering factor of 40%.Comment: 22 pages, 23 figures. Accepted for publication in MNRAS. Revised 28/2/08. Version with figures at full resolution at http://astro.ic.ac.uk/~mrr/swirephotzcat/swirephotz5.pdf.g

A Long-Wavelength View on Galaxy Evolution from Deep Surveys by the Infrared Space Observatory

We discuss the constraints set on galaxy evolution by data from deep surveys performed in the mid-IR and far-IR with ISO and with mm telescopes at longer wavelengths. These reveal extremely high rates of evolution for IR galaxies. According to our model, the deep ISO surveys at 15 micron may have already resolved more than 50% of the CIRB intensity, hence allowing to investigate the origin of the CIRB. From our fits to the observed optical-IR SEDs, these objects appear to involve massive galaxies hosting luminous starbursts (SFR 100 Mo/yr). Our evolutionary scheme considers a bimodal star formation (SF), including long-lived quiescent SF, and enhanced SF taking place during transient events recurrently triggered by interactions and merging. We interpret the strong observed evolution as an increase with z of the rate of interactions between galaxies (density evolution) and an increase of their IR luminosity due to the more abundant fuel available in the past (luminosity evolution). Very schematically, we associate the origin of the bulk of the optical/NIR background to the quiescent evolution, while the CIRB is interpreted as mostly due the dusty starburst phase (the latter possibly leading to the formation of galaxy spheroids). The large energy contents in the CIRB and optical backgrounds are not easily explained, considering the moderate efficiency of energy generation by stars: a top-heavy stellar IMF associated with the starburst phase (and compared with a more standard IMF during the quiescent SF) would alleviate the problem. IR data suggest that the strong observed evolution to z~1 should turn over at higher z: scenarios in which a dominant fraction of stellar formation occurs at very high-z are not supported by our analysis.Comment: 30 pages, version with improved references, to appear in Astronomy & Astrophysic

Biallelic Variants in PYROXD2 Cause a Severe Infantile Metabolic Disorder Affecting Mitochondrial Function

Pyridine Nucleotide-Disulfide Oxidoreductase Domain 2 (PYROXD2; previously called YueF) is a mitochondrial inner membrane/matrix-residing protein and is reported to regulate mitochondrial function. The clinical importance of PYROXD2 has been unclear, and little is known of the protein’s precise biological function. In the present paper, we report biallelic variants in PYROXD2 identified by genome sequencing in a patient with suspected mitochondrial disease. The child presented with acute neurological deterioration, unresponsive episodes, and extreme metabolic acidosis, and received rapid genomic testing. He died shortly after. Magnetic resonance imaging (MRI) brain imaging showed changes resembling Leigh syndrome, one of the more common childhood mitochondrial neurological diseases. Functional studies in patient fibroblasts showed a heightened sensitivity to mitochondrial metabolic stress and increased mitochondrial superoxide levels. Quantitative proteomic analysis demonstrated decreased levels of subunits of the mitochondrial respiratory chain complex I, and both the small and large subunits of the mitochondrial ribosome, suggesting a mitoribosomal defect. Our findings support the critical role of PYROXD2 in human cells, and suggest that the biallelic PYROXD2 variants are associated with mitochondrial dysfunction, and can plausibly explain the child’s clinical presentation

GAMA/G10-COSMOS/3D-HST: The 0<z<5 cosmic star-formation history, stellar- and dust-mass densities

We use the energy-balance code MAGPHYS to determine stellar and dust masses, and dust corrected star-formation rates for over 200,000 GAMA galaxies, 170,000 G10-COSMOS galaxies and 200,000 3D-HST galaxies. Our values agree well with previously reported measurements and constitute a representative and homogeneous dataset spanning a broad range in stellar mass (10^8---10^12 Msol), dust mass (10^6---10^9 Msol), and star-formation rates (0.01---100 Msol per yr), and over a broad redshift range (0.0 < z < 5.0). We combine these data to measure the cosmic star-formation history (CSFH), the stellar-mass density (SMD), and the dust-mass density (DMD) over a 12 Gyr timeline. The data mostly agree with previous estimates, where they exist, and provide a quasi-homogeneous dataset using consistent mass and star-formation estimators with consistent underlying assumptions over the full time range. As a consequence our formal errors are significantly reduced when compared to the historic literature. Integrating our cosmic star-formation history we precisely reproduce the stellar-mass density with an ISM replenishment factor of 0.50 +/- 0.07, consistent with our choice of Chabrier IMF plus some modest amount of stripped stellar mass. Exploring the cosmic dust density evolution, we find a gradual increase in dust density with lookback time. We build a simple phenomenological model from the CSFH to account for the dust mass evolution, and infer two key conclusions: (1) For every unit of stellar mass which is formed 0.0065---0.004 units of dust mass is also formed; (2) Over the history of the Universe approximately 90 to 95 per cent of all dust formed has been destroyed and/or ejected

Compound heterozygous Pkd1l1 variants in a family with two fetuses affected by heterotaxy and complex Chd

Heterotaxy and congenital heart defects associated with pathogenic variants in the PKD1L1 gene (autosomal visceral heterotaxy type 8, MIM 617205) has been reported in only four individuals from three unrelated families. We describe a further family with two affected fetuses and novel compound heterozygous pathogenic variants in PKD1L1. PKD1L1 has been shown to function in the ciliary sensation of nodal flow at the embryo primitive node and in the restriction of NODAL signalling to the left lateral. plate mesoderm, mechanisms involved in the development of laterality in vertebrates. Individuals affected with this autosomal recessive condition have variable thoracic and abdominal situs. Features of CHD and other anomalies vary between and within families.Accepted manuscript 12 month embarg

VVDS-SWIRE evolution of the rest frame K-band luminosity function from z=1.5

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