Monthly Notices of the Royal Astronomical Society, 2011
ABSTRACT We investigate the environments of both X-ray and radio-loud active galactic nuclei (AGN... more ABSTRACT We investigate the environments of both X-ray and radio-loud active galactic nuclei (AGN) within the UK Infrared Telescope (UKIRT) Infrared Deep Sky Survey (UKIDSS) Ultra-deep Survey (UDS) using deep infrared selection to sample the galaxy density field in the redshift range 1.0 ≤z≤ 1.5. Using angular cross-correlation techniques we find that both X-ray and radio-loud AGN preferentially reside in overdense environments. We also find that both types of AGN cluster more strongly with those galaxies classified as ‘passive’ rather than those that are actively star forming. We infer clustering scalelengths comparable to those of passive red galaxies, suggesting that typical AGN at these epochs reside in dark matter haloes of mass M≳ 1013 M⊙. A closer look at the small-scale environments of the AGN reveals that the neighbouring galaxies of radio-loud AGN have U−B colours more skewed towards the ‘green valley’ and the red sequence, whereas the neighbours of X-ray AGN show no difference to the general galaxy population. This suggests that although both AGN types live in overdense environments, the radio-loud AGN may be preferentially located in more evolved cluster cores, in a similar environment to low-powered radio AGN in the local Universe.
Monthly Notices of the Royal Astronomical Society, 2013
ABSTRACT We investigate galactic-scale outflows in the redshift range 0.71 < z < 1.... more ABSTRACT We investigate galactic-scale outflows in the redshift range 0.71 < z < 1.63, using 413 K-band selected galaxies observed in the spectroscopic follow-up of the UKIDSS Ultra-Deep Survey (UDSz). The galaxies have an average stellar mass of ~10^9.5 solar masses and span a wide range in rest-frame colours, representing typical star-forming galaxies at this epoch. We stack the spectra by various galaxy properties, including stellar mass, [OII] equivalent width, star-formation rate, specific star-formation rate and rest-frame spectral indices. We find that outflows are present in virtually all spectral stacks, with velocities ranging from 100-1000 km s^-1, indicating that large-scale outflowing winds are a common property at these redshifts. The highest velocity outflows (>500 km s^-1) are found in galaxies with the highest stellar masses and the youngest stellar populations. Our findings suggest that high velocity galactic outflows are mostly driven by star-forming processes rather than AGN, with implied mass outflow rates comparable to the rates of star formation. Such behaviour is consistent with models required to reproduce the high-redshift mass-metallicity relation.
We present early results on the clustering of galaxies at z˜ 2, selected using the BzK colour tec... more We present early results on the clustering of galaxies at z˜ 2, selected using the BzK colour technique from the UKIDSS Ultra-Deep Survey (UDS). The passive (pBzK) galaxies are the most strongly clustered, consistent with inhabiting dark-matter halos in excess of 10^{13}M_{&sun;} at these redshifts. Starforming (sBzK) galaxies are less strongly clustered, but reveal an excess of pairs on small
The star formation history is a key-element to understand galaxy evolution and formation. Recent ... more The star formation history is a key-element to understand galaxy evolution and formation. Recent studies have shown that the star-formation rate peaks at redshift z=1-3 and then decline to its local value. The physical processes responsible for the sudden quenching of star-formation are still unknown. In order to better understand the origin of these effects, we propose in this study to use the UV-luminosity as an indicator of the Star-formation rate. We take advantage of our deep NIR/optical data from the UKIDSS-UDS/SXDS survey and our very deep CFHT U-band data to compute the luminosity function of galaxies at z=1-3. Fitting the Schechter parameters to integrate luminosity density to explore the evolution of the Star-formation rate.
We present early results on the clustering of galaxies at z˜ 2, selected using the BzK colour tec... more We present early results on the clustering of galaxies at z˜ 2, selected using the BzK colour technique from the UKIDSS Ultra-Deep Survey (UDS). The passive (pBzK) galaxies are the most strongly clustered, consistent with inhabiting dark-matter halos in excess of 10^{13}M_{&sun;} at these redshifts. Starforming (sBzK) galaxies are less strongly clustered, but reveal an excess of pairs on small
We present photometric redshift estimates for galaxies used in the weak lensing analysis of the D... more We present photometric redshift estimates for galaxies used in the weak lensing analysis of the Dark Energy Survey Science Verification (DES SV) data. Four model- or machine learning-based photometric redshift methods -- ANNZ2, BPZ calibrated against BCC-Ufig simulations, SkyNet, and TPZ -- are analysed. For training, calibration, and testing of these methods, we construct a catalogue of spectroscopically confirmed galaxies matched against DES SV data. The performance of the methods is evaluated against the matched spectroscopic catalogue, focusing on metrics relevant for weak lensing analyses, with additional validation against COSMOS photo-zs. From the galaxies in the DES SV shear catalogue, which have mean redshift $0.72\pm0.01$ over the range $0.3<z<1.3$, we construct three tomographic bins with means of $z=\{0.45, 0.67, 1.00\}$. These bins each have systematic uncertainties $\delta z \lesssim 0.05$ in the mean of the fiducial SkyNet photo-z $n(z)$. We propagate the errors...
Monthly Notices of the Royal Astronomical Society, 2011
ABSTRACT We investigate the environments of both X-ray and radio-loud active galactic nuclei (AGN... more ABSTRACT We investigate the environments of both X-ray and radio-loud active galactic nuclei (AGN) within the UK Infrared Telescope (UKIRT) Infrared Deep Sky Survey (UKIDSS) Ultra-deep Survey (UDS) using deep infrared selection to sample the galaxy density field in the redshift range 1.0 ≤z≤ 1.5. Using angular cross-correlation techniques we find that both X-ray and radio-loud AGN preferentially reside in overdense environments. We also find that both types of AGN cluster more strongly with those galaxies classified as ‘passive’ rather than those that are actively star forming. We infer clustering scalelengths comparable to those of passive red galaxies, suggesting that typical AGN at these epochs reside in dark matter haloes of mass M≳ 1013 M⊙. A closer look at the small-scale environments of the AGN reveals that the neighbouring galaxies of radio-loud AGN have U−B colours more skewed towards the ‘green valley’ and the red sequence, whereas the neighbours of X-ray AGN show no difference to the general galaxy population. This suggests that although both AGN types live in overdense environments, the radio-loud AGN may be preferentially located in more evolved cluster cores, in a similar environment to low-powered radio AGN in the local Universe.
Monthly Notices of the Royal Astronomical Society, 2013
ABSTRACT We investigate galactic-scale outflows in the redshift range 0.71 &lt; z &lt; 1.... more ABSTRACT We investigate galactic-scale outflows in the redshift range 0.71 &lt; z &lt; 1.63, using 413 K-band selected galaxies observed in the spectroscopic follow-up of the UKIDSS Ultra-Deep Survey (UDSz). The galaxies have an average stellar mass of ~10^9.5 solar masses and span a wide range in rest-frame colours, representing typical star-forming galaxies at this epoch. We stack the spectra by various galaxy properties, including stellar mass, [OII] equivalent width, star-formation rate, specific star-formation rate and rest-frame spectral indices. We find that outflows are present in virtually all spectral stacks, with velocities ranging from 100-1000 km s^-1, indicating that large-scale outflowing winds are a common property at these redshifts. The highest velocity outflows (&gt;500 km s^-1) are found in galaxies with the highest stellar masses and the youngest stellar populations. Our findings suggest that high velocity galactic outflows are mostly driven by star-forming processes rather than AGN, with implied mass outflow rates comparable to the rates of star formation. Such behaviour is consistent with models required to reproduce the high-redshift mass-metallicity relation.
We present early results on the clustering of galaxies at z˜ 2, selected using the BzK colour tec... more We present early results on the clustering of galaxies at z˜ 2, selected using the BzK colour technique from the UKIDSS Ultra-Deep Survey (UDS). The passive (pBzK) galaxies are the most strongly clustered, consistent with inhabiting dark-matter halos in excess of 10^{13}M_{&amp;sun;} at these redshifts. Starforming (sBzK) galaxies are less strongly clustered, but reveal an excess of pairs on small
The star formation history is a key-element to understand galaxy evolution and formation. Recent ... more The star formation history is a key-element to understand galaxy evolution and formation. Recent studies have shown that the star-formation rate peaks at redshift z=1-3 and then decline to its local value. The physical processes responsible for the sudden quenching of star-formation are still unknown. In order to better understand the origin of these effects, we propose in this study to use the UV-luminosity as an indicator of the Star-formation rate. We take advantage of our deep NIR/optical data from the UKIDSS-UDS/SXDS survey and our very deep CFHT U-band data to compute the luminosity function of galaxies at z=1-3. Fitting the Schechter parameters to integrate luminosity density to explore the evolution of the Star-formation rate.
We present early results on the clustering of galaxies at z˜ 2, selected using the BzK colour tec... more We present early results on the clustering of galaxies at z˜ 2, selected using the BzK colour technique from the UKIDSS Ultra-Deep Survey (UDS). The passive (pBzK) galaxies are the most strongly clustered, consistent with inhabiting dark-matter halos in excess of 10^{13}M_{&amp;sun;} at these redshifts. Starforming (sBzK) galaxies are less strongly clustered, but reveal an excess of pairs on small
We present photometric redshift estimates for galaxies used in the weak lensing analysis of the D... more We present photometric redshift estimates for galaxies used in the weak lensing analysis of the Dark Energy Survey Science Verification (DES SV) data. Four model- or machine learning-based photometric redshift methods -- ANNZ2, BPZ calibrated against BCC-Ufig simulations, SkyNet, and TPZ -- are analysed. For training, calibration, and testing of these methods, we construct a catalogue of spectroscopically confirmed galaxies matched against DES SV data. The performance of the methods is evaluated against the matched spectroscopic catalogue, focusing on metrics relevant for weak lensing analyses, with additional validation against COSMOS photo-zs. From the galaxies in the DES SV shear catalogue, which have mean redshift $0.72\pm0.01$ over the range $0.3<z<1.3$, we construct three tomographic bins with means of $z=\{0.45, 0.67, 1.00\}$. These bins each have systematic uncertainties $\delta z \lesssim 0.05$ in the mean of the fiducial SkyNet photo-z $n(z)$. We propagate the errors...
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