Browsing by Author "Shanks, T."
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- ItemThe nature of sub-millimetre galaxies II: an ALMA comparison of SMG dust heating mechanisms(2022) Ansarinejad, B.; Shanks, T.; Bielby, R. M.; Metcalfe, N.; Infante, L.; Murphy, D. N. A.; Rosario, D. J.; Stach, S. M.We compare the contribution of active galactic nuclei (AGNs) and star formation towards dust heating in sub-mm galaxies (SMGs). We have used ALMA at 0.1-arcsec resolution to image a complete flux-limited sample of seven sub-mm sources previously shown to have spectral energy distributions that were as well-fitted by obscured AGN as star-forming galaxy templates. Indeed, two sub-mm sources were known to be quasars from their absorbed X-ray emission. We find the sub-mm sizes of all SMGs to be small (approximate to 1-2 kpc) and generally similar to 3 times smaller than any host detected in the near-infrared (NIR). In all cases, the five SMGs are comparable in sub-mm size to the two known quasars and four z approximate to 6 quasars, also observed with ALMA. We detect no evidence of diffuse spiral arms in this complete sample. We then convert the far-infrared (FIR) luminosities to star formation rate (SFR) surface densities and find that the SMGs occupy the same range as the known quasars in our sample. We conclude that in terms of sub-mm size, extent relative to host and SFR density as well as luminosity and mid-IR (MIR) colour, there is little distinction between the SMGs and sub-mm bright quasars. Finally, we present preliminary evidence that SMGs with higher MIR luminosities and sub-mm loud quasars tend to have dust components that range to hotter temperatures than their less luminous SMG counterparts. In light of these results, we continue to suggest that luminous SMGs may host dust-absorbed quasars that may simultaneously dominate the FIR and hard X-ray backgrounds.
- ItemThe nature of sub-millimetre galaxies II: an ALMA comparison of SMG dust heating mechanisms(2022) Ansarinejad, B.; Shanks, T.; Bielby, R. M.; Metcalfe, N.; Infante, L.; Murphy, D. N. A.; Rosario, D. J.; Stach, S. M.We compare the contribution of active galactic nuclei (AGNs) and star formation towards dust heating in sub-mm galaxies (SMGs). We have used ALMA at 0.1-arcsec resolution to image a complete flux-limited sample of seven sub-mm sources previously shown to have spectral energy distributions that were as well-fitted by obscured AGN as star-forming galaxy templates. Indeed, two sub-mm sources were known to be quasars from their absorbed X-ray emission. We find the sub-mm sizes of all SMGs to be small (approximate to 1-2 kpc) and generally similar to 3 times smaller than any host detected in the near-infrared (NIR). In all cases, the five SMGs are comparable in sub-mm size to the two known quasars and four z approximate to 6 quasars, also observed with ALMA. We detect no evidence of diffuse spiral arms in this complete sample. We then convert the far-infrared (FIR) luminosities to star formation rate (SFR) surface densities and find that the SMGs occupy the same range as the known quasars in our sample. We conclude that in terms of sub-mm size, extent relative to host and SFR density as well as luminosity and mid-IR (MIR) colour, there is little distinction between the SMGs and sub-mm bright quasars. Finally, we present preliminary evidence that SMGs with higher MIR luminosities and sub-mm loud quasars tend to have dust components that range to hotter temperatures than their less luminous SMG counterparts. In light of these results, we continue to suggest that luminous SMGs may host dust-absorbed quasars that may simultaneously dominate the FIR and hard X-ray backgrounds.
- ItemThe very large telescope lyman-break galaxy redshift survey - iv.: Gas and galaxies at z ~ 3 in observations and simulations(2014) Tummuangpak, P.; Bielby, R.; Shanks, T.; Theuns, T.; Crighton, N.; Francke Henríquez, Harold Johanns Phillippe; Infante Lira, Leopoldo
- ItemThe VLT LBG redshift survey - V. Characterizing the z = 3.1 Lyman α emitter population(2016) Bielby, R. M.; Tummuangpak, P.; Shanks, T.; Francke Henríquez, Harold Johanns Phillippe; Crighton, N.H.M.; Bañados, E.; González López, Jorge; Infante Lira, Leopoldo; Orsi, A.
- ItemThe VLT LBG redshift survey - VI. Mapping HI in the proximity of z similar to 3 LBGs with X-Shooter(OXFORD UNIV PRESS, 2017) Bielby, R. M.; Shanks, T.; Crighton, N. H. M.; Bornancini, C. G.; Infante, L.; Lambas, D. G.; Minniti, D.; Morris, S. L.; Tummuangpak, P.We present an analysis of the spatial distribution and dynamics of neutral hydrogen gas around galaxies using new X-Shooter observations of z similar to 2.5-4 quasars. Adding the X-Shooter data to our existing data set of high-resolution quasar spectroscopy, we use a total sample of 29 quasars alongside similar to 1700 Lyman Break Galaxies (LBGs) in the redshift range 2 less than or similar to z less than or similar to 3.5. We measure the Ly alpha forest auto-correlation function, finding a clustering length of s(0) = 0.081 +/- 0.006 h(-1) Mpc, and the cross-correlation function with LBGs, finding a cross-clustering length of s0 = 0.27 +/- 0.14 h(-1) Mpc and power-law slope gamma = 1.1 +/- 0.2. Our results highlight the weakly clustered nature of neutral hydrogren systems in the Ly alpha forest. Building on this, we make a first analysis of the dependence of the clustering on absorber strength, finding a clear preference for stronger Ly alpha forest absorption features to be more strongly clustered around the galaxy population, suggesting that they trace on average higher mass haloes. Using the projected and 2-D cross-correlation functions, we constrain the dynamics of Ly alpha forest clouds around z similar to 3 galaxies. We find a significant detection of large-scale infall of neutral hydrogen, with a constraint on the Ly alpha forest infall parameter of beta(F) = 1.02 +/- 0.22.
- ItemThe VLT LBG redshift survey - VI. Mapping HI in the proximity of z ~ 3 LBGs with X-Shooter(2017) Bielby, R. M.; Shanks, T.; Crighton, N. H. M.; Bornancini, C. G.; Infante Lira, Leopoldo; Lambas, D. G.; Minniti, D.; Morris, S. L.; Tummuangpak, P.
- ItemThe VST ATLAS Quasar Survey - II. Halo mass profiles of galaxies, LRGs and galaxy clusters via quasar and CMB lensing(2024) Eltvedt, Alice M.; Shanks, T.; Metcalfe, N.; Ansarinejad, B.; Barrientos, L. F.; Murphy, D. N. A.; Alexander, D. M.We cross-correlate a low-contamination subset of the VST ATLAS g < 22.5 quasar catalogue with g < 21.5 galaxy clusters, r < 21 galaxies and r < 19.5 luminous red galaxies (LRGs) to probe their halo mass profiles via quasar magnification bias caused by weak lensing. In the case of galaxy clusters, we find that at small scales their mass profiles are well fitted by Navarro, Frenk, and White models with masses within the expected range. For the galaxies, we find consistency with previous Sloan Digital Sky Survey-based results for the galaxy-quasar cross-correlation and the galaxy auto-correlation functions. Disagreement as to whether the cross-correlation results are in tension with Lambda cold dark matter appears due to different assumptions as to whether galaxies trace mass. We conclude that halo occupation distribution (HOD) models fit the galaxy-quasar lensing results better than models where galaxies trace the mass. We further test the cluster and galaxy HOD models in the 2-halo range using the Planck cosmic microwave background (CMB) lensing map, finding that the cross-correlation with both the poorest clusters and the galaxies may be marginally overpredicted by the above HOD models. Finally, we measure the magnification bias of LRGs using both quasar and CMB lensing and find that the observed quasar lensing amplitude may be approximate to 2x too high and, on larger scales, the CMB lensing amplitude may be too low to be explained by a standard LRG HOD model.
- ItemThe VST ATLAS Quasar Survey - III. Halo mass function via quasar clustering and quasar-CMB lensing cross-clustering(2024) Eltvedt, Alice M.; Shanks, T.; Metcalfe, N.; Ansarinejad, B.; Barrientos, L. F.; Murphy, D. N. A.; Alexander, D. M.We exploit the VST ATLAS quasar (QSO) catalogue to perform three measurements of the quasar halo mass profile. First, we make a new estimate of the angular autocorrelation function of approximate to 230 000 ATLAS quasars with z(photo)less than or similar to 2.5 and 17
- ItemThe VST ATLAS quasar survey I: Catalogue of photometrically selected quasar candidates(2023) Eltvedt, Alice M.; Shanks, T.; Metcalfe, N.; Ansarinejad, B.; Barrientos, L. F.; Sharp, R.; Malik, U.; Murphy, D. N. A.; Irwin, M.; Wilson, M.; Alexander, D. M.; Kovacs, Andras; Garcia-Bellido, Juan; Ahlen, Steven; Brooks, David; de la Macorra, Axel; Font-Ribera, Andreu; Gontcho, Satya Gontcho a; Honscheid, Klaus; Meisner, Aaron; Miquel, Ramon; Nie, Jundan; Tarle, Gregory; Vargas-Magana, Mariana; Zhou, ZhiminWe present the VST ATLAS Quasar Survey, consisting of similar to 1229 000 quasar (QSO) candidates with 16 < g < 22.5 over similar to 4700 deg(2). The catalogue is based on VST ATLAS+NEOWISE imaging surveys and aims to reach a QSO sky density of 130 deg-2 for z < 2.2 and similar to 30 deg(-2) for z > 2.2. To guide our selection, we use X-ray/UV/optical/MIR data in the extended William Herschel Deep Field (WHDF) where we find a g < 22.5 broad-line QSO density of 269 +/- 67 deg(-2), roughly consistent with the expected similar to 196 deg(-2). We find that similar to 25 per cent of our QSOs are morphologically classed as optically extended. Overall, we find that in these deep data, MIR, UV, and X-ray selections are similar to 70-90 per cent complete while X-ray suffers less contamination than MIR and UV. MIR is however more sensitive than X-ray or UV to z > 2.2 QSOs at g < 22.5 and the S-X (0.5 - 10 keV) > 1 x10(-14) ergs cm(-2) s(-1) limit of eROSITA. We adjust the selection criteria from our previous 2QDES pilot survey and prioritize VST ATLAS candidates that show both UV and MIR excess, also selecting candidates initially classified as extended. We test our selections using data from DESI (which will be released in DR1) and 2dF to estimate the efficiency and completeness, and we use ANNz2 to determine photometric redshifts. Applying over the similar to 4700 deg(2) ATLAS area gives us similar to 917 000 z < 2.2 QSO candidates of which 472 000 are likely to be z < 2.2 QSOs, implying a sky density of similar to 100 deg(-2), which our WHDF analysis suggests will rise to at least 130 deg(-2) when eROSITA X-ray candidates are included. At z > 2.2, we find similar to 310() 000 candidates, of which 169 000 are likely to be QSOs for a sky density of similar to 36 deg(-2).