ORCID Profile
0000-0001-5600-0534
Current Organisation
University of Nottingham
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Publisher: Oxford University Press (OUP)
Date: 07-09-2019
Abstract: We use state-of-the-art hydrodyamical simulations from the Sherwood, EAGLE, and Illustris projects to examine the signature of Mz = 0 ≃ 1014 M⊙ protoclusters observed in Ly α absorption at z ≃ 2.4. We find that there is a weak correlation between the mass overdensity, δm, and the Ly α effective optical depth relative to the mean, $\\delta _{\\tau _\\textrm{eff}}$, averaged over $15~h^{-1}\\, \\textrm{cMpc}$ scales, although scatter in the δm–$\\delta _{\\tau _\\textrm{eff}}$ plane means it is not possible to uniquely identify large-scale overdensities with strong Ly α absorption. Although all protoclusters are associated with large-scale mass overdensities, most sightlines through protoclusters in a ∼106$\\rm cMpc^{3}$ volume probe the low column density Ly α forest. A small subset of sightlines that pass through protoclusters exhibit coherent, strong Ly α absorption on $15h^{-1}\\rm \\, cMpc$ scales, although these correspond to a wide range in mass overdensity. Assuming perfect removal of contamination by Ly α absorbers with d ing wings, more than half of the remaining sightlines with $\\delta _{\\tau _{\\rm eff}}\\gt 3.5$ trace protoclusters. It is furthermore possible to identify a model-dependent $\\delta _{\\tau _{\\rm eff}}$ threshold that selects only protoclusters. However, such regions are rare: excluding absorption caused by d ed systems, less than 0.1 per cent of sightlines that pass through a protocluster have $\\delta _{\\tau _{\\rm eff}}\\gt 3.5$, meaning that any protocluster s le selected in this manner will also be highly incomplete. On the other hand, coherent regions of Ly α absorption also provide a promising route for identifying and studying filamentary environments at high redshift.
Publisher: EDP Sciences
Date: 06-2014
Publisher: American Astronomical Society
Date: 06-08-2012
Publisher: Oxford University Press (OUP)
Date: 16-11-2013
Publisher: EDP Sciences
Date: 12-2017
DOI: 10.1051/0004-6361/201730449
Abstract: It is not yet known if the properties of molecular gas in distant protocluster galaxies are significantly affected by their environment as galaxies are in local clusters. Through a deep, 64 h of effective on-source integration with the Australian Telescope Compact Array (ATCA), we discovered a massive, M mol = 2.0 ± 0.2× 10 11 M ⊙ , extended, ~40 kpc, CO(1–0)-emitting disk in the protocluster surrounding the radio galaxy, MRC 1138−262. The galaxy, at z CO = 2.1478, is a clumpy, massive disk galaxy, M ∗ ~ 5 × 10 11 M ⊙ , which lies 250 kpc in projection from MRC 1138−262 and is a known H α emitter, named HAE229. This source has a molecular gas fraction of ~30%. The CO emission has a kinematic gradient along its major axis, centered on the highest surface brightness rest-frame optical emission, consistent with HAE229 being a rotating disk. Surprisingly, a significant fraction of the CO emission lies outside of the UV/optical emission. In spite of this, HAE229 follows the same relation between star-formation rate and molecular gas mass as normal field galaxies. HAE229 is the first CO(1–0) detection of an ordinary, star-forming galaxy in a protocluster. We compare a s le of cluster members at z 0.4 thatare detected in low-order CO transitions, with a similar s le of sources drawn from the field. We confirm findings that the CO-luminosity and full-width at half maximum are correlated in starbursts and show that this relation is valid for normal high- z galaxies as well as for those in overdensities. We do not find a clear dichotomy in the integrated Schmidt-Kennicutt relation for protocluster and field galaxies. Our results suggest that environment does not have an impact on the “star-formation efficiency” or the molecular gas content of high-redshift galaxies. Not finding any environmental dependence in these characteristics, especially for such an extended CO disk, suggests that environmentally-specific processes such as ram pressure stripping do not operate efficiently in (proto)clusters.
Publisher: Oxford University Press (OUP)
Date: 03-03-2018
Publisher: Oxford University Press (OUP)
Date: 24-07-2015
Publisher: EDP Sciences
Date: 11-2010
Publisher: Oxford University Press (OUP)
Date: 21-09-2008
Publisher: Oxford University Press (OUP)
Date: 09-2011
Publisher: EDP Sciences
Date: 08-2021
DOI: 10.1051/0004-6361/202040232
Abstract: We report a detailed CO(1−0) survey of a galaxy protocluster field at z = 2.16, based on 475 h of observations with the Australia Telescope Compact Array. We constructed a large mosaic of 13 in idual pointings, covering an area of 21 arcmin 2 and ±6500 km s −1 range in velocity. We obtained a robust s le of 46 CO(1−0) detections spanning z = 2.09 − 2.22, constituting the largest s le of molecular gas measurements in protoclusters to date. The CO emitters show an overdensity at z = 2.12 − 2.21, suggesting a galaxy super-protocluster or a protocluster connected to large-scale filaments of ∼120 cMpc in size. We find that 90% of CO emitters have distances .′5−4′ to the center galaxy, indicating that small area surveys would miss the majority of gas reservoirs in similar structures. Half of the CO emitters have velocities larger than escape velocities, which appears gravitationally unbound to the cluster core. These unbound sources are barely found within the R 200 radius around the center, which is consistent with a picture in which the cluster core is collapsed while outer regions are still in formation. Compared to other protoclusters, this structure contains a relatively higher number of CO emitters with relatively narrow line widths and high luminosities, indicating galaxy mergers. We used these CO emitters to place the first constraint on the CO luminosity function and molecular gas density in an overdense environment. The litude of the CO luminosity function is 1.6 ± 0.5 orders of magnitude higher than that observed for field galaxy s les at z ∼ 2, and one order of magnitude higher than predictions for galaxy protoclusters from semi-analytical SHARK models. We derive a high molecular gas density of 0.6 − 1.3 × 10 9 M ⊙ cMpc −3 for this structure, which is consistent with predictions for cold gas density of massive structures from hydro-dynamical DIANOGA simulations.
Publisher: Oxford University Press (OUP)
Date: 11-2010
Publisher: American Astronomical Society
Date: 06-05-2013
Publisher: American Association for the Advancement of Science (AAAS)
Date: 31-03-2023
Abstract: The growth of galaxies in the early Universe is driven by accretion of circum- and intergalactic gas. Simulations have predicted that steady streams of cold gas penetrate the dark matter halos of galaxies and provide the raw material necessary to sustain star formation. We report a filamentary stream of gas that extends for 100 kiloparsecs and connects to the massive radio galaxy 4C 41.17. We detected the stream using submillimeter observations of the 3 P 1 to 3 P 0 emission from the [C i ] line of atomic carbon, a tracer of neutral atomic or molecular hydrogen gas. The galaxy contains a central gas reservoir that is fueling a vigorous starburst. Our results show that the raw material for star formation can be present in cosmic streams outside galaxies.
Publisher: Oxford University Press (OUP)
Date: 21-07-2021
Abstract: Local variations in the intergalactic medium (IGM) neutral hydrogen fraction will affect the Ly α absorption signature of protoclusters identified in tomographic surveys. Using the IllustrisTNG simulations, we investigate how the AGN proximity effect and hot, collisionally ionized gas arising from gravitational infall and black hole feedback changes the Ly α absorption associated with $M_{z=0}\\simeq 10^{14}\\, {\\rm M}_\\odot$ protoclusters at z ≃ 2.4. We find that protocluster galaxy overdensities exhibit a weak anticorrelation with Ly α transmission in IGM transmission maps, but local H$\\, \\rm \\scriptstyle I$ ionization enhancements due to hot $T\\gt 10^{6}\\rm \\, K$ gas or nearby AGN can disrupt this relationship within in idual protoclusters. On average, however, we find that strong reductions in the IGM neutral fraction are limited to within $\\lesssim 5h^{-1}\\, \\textrm {cMpc}$ of the dark matter haloes. Local ionization enhancements will therefore have a minimal impact on the completeness of protocluster identification in tomographic surveys if smoothing Ly α transmission maps over scales of $\\sim 4 h^{-1}\\, \\textrm {cMpc}$, as is typically done in observations. However, if calibrating the relationship between the matter density and Ly α transmission in tomographic maps using simple analytical models for the Ly α forest opacity, the presence of hot gas around haloes can still result in systematically lower estimates of Mz = 0 for the most massive protoclusters.
Publisher: Oxford University Press (OUP)
Date: 24-09-2014
Publisher: American Astronomical Society
Date: 22-05-2018
Publisher: American Astronomical Society
Date: 10-04-2014
Publisher: American Astronomical Society
Date: 05-04-2012
Publisher: Oxford University Press (OUP)
Date: 19-12-2022
Abstract: Enhanced ionizing radiation in close proximity to redshift z ≳ 6 quasars creates short windows of intergalactic Ly α transmission blueward of the quasar Ly α emission lines. The majority of these Ly α near-zones are consistent with quasars that have optically/UV bright lifetimes of $t_{\\rm Q}\\sim 10^{5}\\!-\\!10^{7}\\rm \\, yr$. However, lifetimes as short as $t_{\\rm Q}\\lesssim 10^{4}\\rm \\, yr$ appear to be required by the smallest Ly α near-zones. These short lifetimes present an apparent challenge for the growth of $\\sim 10^{9}\\rm \\, M_{\\odot }$ black holes at z ≳ 6. Accretion over longer time-scales is only possible if black holes grow primarily in an obscured phase, or if the quasars are variable on time-scales comparable to the equilibriation time for ionized hydrogen. Distinguishing between very young quasars and older quasars that have experienced episodic accretion with Ly α absorption alone is challenging, however. We therefore predict the signature of proximate 21-cm absorption around z ≳ 6 radio-loud quasars. For modest pre-heating of intergalactic hydrogen by the X-ray background, where the spin temperature $T_{\\rm S} \\lesssim 10^{2}\\rm \\, K$ prior to any quasar heating, we find proximate 21-cm absorption should be observable in the spectra of radio-loud quasars. The extent of the proximate 21-cm absorption is sensitive to the integrated lifetime of the quasar. Evidence for proximate 21-cm absorption from the diffuse intergalactic medium within $2\\!-\\!3\\rm \\, pMpc$ of a (radio-loud) quasar would be consistent with a short quasar lifetime, $t_{\\rm Q}\\lesssim 10^{5}\\rm \\, yr$, and would provide a complementary constraint on models for high-redshift black hole growth.
Publisher: EDP Sciences
Date: 09-2020
DOI: 10.1051/0004-6361/202038673
Abstract: Passive early-type galaxies dominate cluster cores at z ≲ 1.5. At higher redshift, cluster core galaxies are observed to have on-going star-formation, which is fueled by cold molecular gas. We measured the molecular gas reservoir of the central region around the radio-loud active galactic nucleus (AGN) in the cluster CARLA J1103 + 3449 at z = 1.44 using NOEMA. The AGN synchrotron emission dominates the continuum emission at 94.48 GHz, and we measured its flux at the AGN position and at the position of two radio jets. Combining our measurements with published results over the range 4.71–94.5 GHz, and assuming S synch ∝ ν − α , we obtain a flat spectral index of α = 0.14 ± 0.03 for the AGN core emission, and a steeper index of α = 1.43 ± 0.04 and α = 1.15 ± 0.04 at positions close to the western and eastern lobes, respectively. The total spectral index is α = 0.92 ± 0.02 over the range 73.8 MHz–94.5 GHz. We detect two CO(2–1) emission lines, both blueshifted with respect to the AGN. Their emission corresponds to two regions, ~17 kpc southeast and ~14 kpc southwest of the AGN, not associated with galaxies. In these two regions, we find a total massive molecular gas reservoir of M gas tot = 3.9 ± 0.4 × 10 10 M ⊙ , which dominates (≳60%) the central total molecular gas reservoir. These results can be explained by massive cool gas flows in the center of the cluster. The AGN early-type host is not yet quenched its star formation rate is consistent with being on the main sequence of star-forming galaxies in the field (star formation rate ~30 – 140 M ⊙ yr −1 ), and the cluster core molecular gas reservoir is expected to feed the AGN and the host star formation before quiescence. The other confirmed cluster members show star formation rates at ~2 σ below the field main sequence at similar redshifts and do not have molecular gas masses larger than galaxies of similar stellar mass in the field.
Publisher: EDP Sciences
Date: 28-10-2013
Publisher: EDP Sciences
Date: 10-2014
Publisher: Oxford University Press (OUP)
Date: 22-11-2012
DOI: 10.1093/MNRAS/STS264
Publisher: Oxford University Press (OUP)
Date: 07-2021
Abstract: A late end to reionisation at redshift z ≃ 5.3 is consistent with observed spatial variations in the Lyα forest transmission and the deficit of Lyα emitting galaxies around extended Lyα absorption troughs at z = 5.5. In this model, large islands of neutral hydrogen should persist in the diffuse intergalactic medium (IGM) until z ≃ 6. We use a novel, hybrid approach that combines high resolution cosmological hydrodynamical simulations with radiative transfer to predict the incidence of strong $21\\rm \\, cm$ forest absorbers with optical depths τ21 & 10−2 from the diffuse IGM in these late reionisation models. We include the effect of redshift space distortions on the simulated $21\\rm \\, cm$ forest spectra, and treat the highly uncertain heating of the pre-reionisation IGM by soft X-rays as a free parameter. For a model with only modest IGM pre-heating, such that average gas kinetic temperatures in the diffuse IGM remain below $T_{\\rm K}\\simeq 10^{2} \\rm \\, K$, we find that strong $21\\rm \\, cm$ forest absorption lines should persist until z = 6. For a s le of ∼10 sufficiently radio loud background sources, a null-detection of $21\\rm \\, cm$ forest absorbers at z ≃ 6 with SKA1-low or possibly LOFAR should provide an informative lower limit on the still largely unconstrained soft X-ray background at high redshift and the temperature of the pre-reionisation IGM.
Publisher: EDP Sciences
Date: 17-06-2016
Publisher: Oxford University Press (OUP)
Date: 12-10-2023
Location: United Kingdom of Great Britain and Northern Ireland
No related grants have been discovered for Nina Hatch.