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  • 1
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    The accretion histories of brightest cluster galaxies from their stellar population gradients (2015)
    Oxford University Press
    Details
    Publication Date: 2015-04-10
    Description: We analyse the spatially resolved stellar populations of nine local ( z 〈 0.1) Brightest Cluster Galaxies (BCGs) observed with VIMOS in Integral Field Unit mode. Our sample is composed of seven slow-rotating and two fast-rotating BCGs. We do not find a connection between stellar kinematics and stellar populations in this small sample. The BCGs have shallow metallicity gradients (median [Fe/H] = –0.11 ± 0.1), high central metallicities (median [Fe/H] [α/Fe] = 0  = 0.13 ± 0.07), and a wide range of central ages (from 5 to 15 Gyr). We propose that the reason for this is diverse evolutionary paths in BCGs. 67 per cent of the sample (6/9) show ~7 Gyr old central ages, which reflects an active accretion history, and 33 per cent of the sample (3/9) have central ages older than 11 Gyr, which suggest no star formation since z = 2. The BCGs show similar central stellar populations and stellar population gradients to early-type galaxies of similar mass ( M dyn 〉 10 11.3 M ) from the ATLAS 3D survey (median [ Z /H] = 0.04 ± 0.07, [ Z /H] = –0.19 ± 0.1). However, massive early-type galaxies from ATLAS 3D have consistently old ages (median Age = 12.0 ± 3.8 Gyr). We also analyse the close massive companion galaxies of two of the BCGs. These galaxies have similar stellar populations to their respective BCGs.
    Print ISSN: 0035-8711
    Electronic ISSN: 1365-2966
    Topics: Physics
    Published by Oxford University Press
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  • 2
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    Recognition of duplex RNA by the deaminase domain of the RNA editing enzyme ADAR2 (2015)
    Oxford University Press
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    Publication Date: 2015-01-24
    Description: Adenosine deaminases acting on RNA (ADARs) hydrolytically deaminate adenosines (A) in a wide variety of duplex RNAs and misregulation of editing is correlated with human disease. However, our understanding of reaction selectivity is limited. ADARs are modular enzymes with multiple double-stranded RNA binding domains (dsRBDs) and a catalytic domain. While dsRBD binding is understood, little is known about ADAR catalytic domain/RNA interactions. Here we use a recently discovered RNA substrate that is rapidly deaminated by the isolated human ADAR2 deaminase domain (hADAR2-D) to probe these interactions. We introduced the nucleoside analog 8-azanebularine (8-azaN) into this RNA (and derived constructs) to mechanistically trap the protein–RNA complex without catalytic turnover for EMSA and ribonuclease footprinting analyses. EMSA showed that hADAR2-D requires duplex RNA and is sensitive to 2'-deoxy substitution at nucleotides opposite the editing site, the local sequence and 8-azaN nucleotide positioning on the duplex. Ribonuclease V1 footprinting shows that hADAR2-D protects ~23 nt on the edited strand around the editing site in an asymmetric fashion (~18 nt on the 5' side and ~5 nt on the 3' side). These studies provide a deeper understanding of the ADAR catalytic domain–RNA interaction and new tools for biophysical analysis of ADAR–RNA complexes.
    Print ISSN: 0305-1048
    Electronic ISSN: 1362-4962
    Topics: Biology
    Published by Oxford University Press
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  • 3
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    Radio galaxies in ZFOURGE/NMBS: no difference in the properties of massive galaxies with and without radio-AGN out to z = 2.25 (2015)
    Oxford University Press
    Details
    Publication Date: 2015-11-27
    Description: In order to reproduce the high-mass end of the galaxy mass distribution, some process must be responsible for the suppression of star formation in the most massive of galaxies. Commonly active galactic nuclei (AGN) are invoked to fulfil this role, but the exact means by which they do so is still the topic of much debate, with studies finding evidence for both the suppression and enhancement of star formation in AGN hosts. Using the ZFOURGE (FourStar Galaxy Evolution) and NMBS (Newfirm Medium Band Survey) galaxy surveys, we investigate the host galaxy properties of a mass-limited ( M ≥ 10 10.5 M ), high-luminosity ( L 1.4 〉 10 24 W Hz –1 ) sample of radio-loud AGN to a redshift of z  = 2.25. In contrast to low-redshift studies, which associate radio-AGN activity with quiescent hosts, we find that the majority of z 〉 1.5 radio-AGN are hosted by star-forming galaxies. Indeed, the stellar populations of radio-AGN are found to evolve with redshift in a manner that is consistent with the non-AGN mass-similar galaxy population. Interestingly, we find that the radio-AGN fraction is constant across a redshift range of 0.25 ≤ z 〈 2.25, perhaps indicating that the radio-AGN duty cycle has little dependence on redshift or galaxy type. We do however see a strong relation between the radio-AGN fraction and stellar mass, with radio-AGN becoming rare below ~10 10.5 M or a halo mass of 10 12 M . This halo-mass threshold is in good agreement with simulations that initiate radio-AGN feedback at this mass limit. Despite this, we find that radio-AGN host star formation rates are consistent with the non-AGN mass-similar galaxy sample, suggesting that while radio-AGN are in the right place to suppress star formation in massive galaxies they are not necessarily responsible for doing so.
    Print ISSN: 0035-8711
    Electronic ISSN: 1365-2966
    Topics: Physics
    Published by Oxford University Press
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  • 4
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    ZFOURGE catalogue of AGN candidates: an enhancement of 160-{mu}m-derived star formation rates in active galaxies to z = 3.2 (2016)
    Oxford University Press
    Details
    Publication Date: 2016-01-24
    Description: We investigate active galactic nuclei (AGN) candidates within the FourStar Galaxy Evolution Survey (ZFOURGE) to determine the impact they have on star formation in their host galaxies. We first identify a population of radio, X-ray, and infrared-selected AGN by cross-matching the deep K s -band imaging of ZFOURGE with overlapping multiwavelength data. From this, we construct a mass-complete (log( $M_{{\ast }}/\text{M}_{{\odot }}$ ) ≥9.75), AGN luminosity limited sample of 235 AGN hosts over z  = 0.2–3.2. We compare the rest-frame U – V versus V – J ( UVJ ) colours and specific star formation rates (sSFRs) of the AGN hosts to a mass-matched control sample of inactive (non-AGN) galaxies. UVJ diagnostics reveal AGN tend to be hosted in a lower fraction of quiescent galaxies and a higher fraction of dusty galaxies than the control sample. Using 160 μm Herschel PACS data, we find the mean specific star formation rate of AGN hosts to be elevated by 0.34 ± 0.07 dex with respect to the control sample across all redshifts. This offset is primarily driven by infrared-selected AGN, where the mean sSFR is found to be elevated by as much as a factor of ~5. The remaining population, comprised predominantly of X-ray AGN hosts, is found mostly consistent with inactive galaxies, exhibiting only a marginal elevation. We discuss scenarios that may explain these findings and postulate that AGN are less likely to be a dominant mechanism for moderating galaxy growth via quenching than has previously been suggested.
    Print ISSN: 0035-8711
    Electronic ISSN: 1365-2966
    Topics: Physics
    Published by Oxford University Press
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  • 5
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    Imprinting control region (ICR) of the Peg3 domain (2012)
    Oxford University Press
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    Publication Date: 2012-05-25
    Description: The imprinting and transcription of the 500 kb genomic region surrounding the mouse Peg3 is predicted to be regulated by the Peg3-differentially methylated region (DMR). In the current study, this prediction was tested using a mutant mouse line lacking this potential imprinting control region (ICR). At the organismal level, paternal and maternal transmission of this knockout (KO) allele caused either reduced or increased growth rates in the mouse, respectively. In terms of the imprinting control, the paternal transmission of the KO allele resulted in bi-allelic expression of the normally maternally expressed Zim2 , whereas the maternal transmission switched the transcriptionally dominant allele for Zfp264 (paternal to maternal). However, the allele-specific DNA methylation patterns of the DMRs of Peg3 , Zim2 and Zim3 were not affected in the mice that inherited the KO allele either paternally or maternally. In terms of the transcriptional control, the paternal transmission caused a dramatic down-regulation in Peg3 expression, but overall up-regulation in the other nearby imprinted genes. Taken together, deletion of the Peg3-DMR caused global changes in the imprinting and transcription of the Peg3 domain, confirming that the Peg3-DMR is an ICR for this imprinted domain.
    Print ISSN: 0964-6906
    Electronic ISSN: 1460-2083
    Topics: Biology , Medicine
    Published by Oxford University Press
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  • 6
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    3-D time-domain Gauss–Newton full waveform inversion for near-surface site characterization (2019)
    Oxford University Press
    Details
    Publication Date: 2019
    Description: 〈span〉〈div〉SUMMARY〈/div〉We present a new 3-D time-domain Gauss–Newton full waveform inversion (3-D FWI) method for near-surface site characterization. The method is based on a solution of 3-D elastic wave equations for forward modelling of wave propagation, and Gauss–Newton inversion approach for model updating to extract material property. Both the forward modelling and model updating are conducted in the time domain, which allows exploiting complete waveform information of multiple frequencies simultaneously for detailed subsurface material properties. Based on virtual sources and reciprocal wavefields, an efficient approach is developed to calculate derivative seismograms (Jacobian matrix) for all cells simultaneously. The capability of the presented FWI method is tested on both synthetic and field experimental data sets. Sensors and sources located in uniform 2-D grids on the ground surface are used to acquire seismic wavefields, which are then inverted for extraction of 3-D subsurface wave velocity structures. The results show that the waveform analysis was able to characterize low- and high-velocity synthetic layers, and variable soil/rock layers of the test site. The 〈span〉S〈/span〉-wave velocity (〈span〉Vs〈/span〉) profiles from field experiment generally agree with invasive standard penetration test (SPT) 〈span〉N〈/span〉-values, including identification of a low-velocity zone. 〈span〉Vs〈/span〉 profiles obtained from a cross-adjoint 3-D FWI are also included for comparison, and results from the presented Gauss–Newton inversion are more consistent with the SPT 〈span〉N〈/span〉-values in both trend and magnitudes.〈/span〉
    Print ISSN: 2051-1965
    Electronic ISSN: 1365-246X
    Topics: Geosciences
    Published by Oxford University Press on behalf of The Deutsche Geophysikalische Gesellschaft (DGG) and the Royal Astronomical Society (RAS).
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  • 7
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    3D Time-Domain Gauss-Newton full waveform inversion for Near-Surface site characterization (2019)
    Oxford University Press
    Details
    Publication Date: 2019
    Description: 〈span〉〈div〉Summary〈/div〉We present a new 3D time-domain Gauss-Newton full waveform inversion (3D FWI) method for near-surface site characterization. The method is based on a solution of 3D elastic wave equations for forward modeling of wave propagation, and Gauss-Newton inversion approach for model updating to extract material property. Both the forward modeling and model updating are conducted in the time domain, which allows exploiting complete waveform information of multiple frequencies simultaneously for detailed subsurface material properties. Based on virtual sources and reciprocal wave-fields, an efficient approach is developed to calculate derivative seismograms (Jacobian matrix) for all cells simultaneously. The capability of the presented FWI method is tested on both synthetic and field experimental datasets. Sensors and sources located in uniform 2D grids on the ground surface are used to acquire seismic wave-fields, which are then inverted for extraction of 3D subsurface wave velocity structures. The results show that the waveform analysis was able to characterize low- and high-velocity synthetic layers, and variable soil/rock layers of the test site. The S-wave velocity (〈span〉Vs〈/span〉) profiles from field experiment generally agree with invasive standard penetration test (SPT) N-values, including identification of a low-velocity zone. 〈span〉Vs〈/span〉 profiles obtained from a cross-adjoint 3D FWI are also included for comparison, and results from the presented Gauss-Newton inversion are more consistent with the SPT N-values in both trend and magnitudes.〈/span〉
    Print ISSN: 2051-1965
    Electronic ISSN: 1365-246X
    Topics: Geosciences
    Published by Oxford University Press on behalf of The Deutsche Geophysikalische Gesellschaft (DGG) and the Royal Astronomical Society (RAS).
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  • 8
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    A novel method for computing the vertical gradients of the potential field: Application to downward continuation (2019)
    Oxford University Press
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    Publication Date: 2019
    Description: 〈span〉〈div〉Summary〈/div〉Downward continuation is a very useful technique in the interpretation of potential field data. It would enhance the short wavelength of the gravity anomalies or accentuate the details of the source distribution. Taylor series expansion method has been proposed to be one of the best downward continued methods. However, the method using high-order vertical derivatives leads to low accuracy and instability results in many cases. In this paper, we propose a new method using a combination of Taylor series expansion and upward continuation for computing vertical derivatives. This method has been tested on the gravitational anomaly of infinite horizontal cylinder in both cases with and without random noise for higher accurate and stable than Hilbert transform method and Laplace equation method, especially in the case of noise input data. This vertical derivative method is applied successfully to calculate the downward continuation according to Taylor series expansion method. The downward continuation is also tested on both complex synthetic models and real data in the East Vietnam Sea (South China Sea). The results reveal that by calculating this new vertical derivative, the downward continuation method gave higher accurate and stable than the previous downward continuation methods.〈/span〉
    Print ISSN: 2051-1965
    Electronic ISSN: 1365-246X
    Topics: Geosciences
    Published by Oxford University Press on behalf of The Deutsche Geophysikalische Gesellschaft (DGG) and the Royal Astronomical Society (RAS).
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  • 9
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    Radio galaxies in ZFOURGE/NMBS: no difference in the properties of massive galaxies with and without radio-AGN out toz = 2.25 (2015)
    Oxford University Press
    Details
    Publication Date: 2015-11-25
    Print ISSN: 0035-8711
    Electronic ISSN: 1365-2966
    Topics: Physics
    Published by Oxford University Press on behalf of The Royal Astronomical Society.
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  • 10
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    Spatial kinematics of Brightest Cluster Galaxies and their close companions from Integral Field Unit spectroscopy★ (2011)
    Oxford University Press
    Details
    Publication Date: 2011-05-02
    Print ISSN: 1745-3925
    Electronic ISSN: 1745-3933
    Topics: Physics
    Published by Oxford University Press on behalf of The Royal Astronomical Society.
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