scholarly journals BUDHiES IV: Deep 21-cm neutral Hydrogen, optical, and UV imaging data of Abell 963 and Abell 2192 at z ≃ 0.2

2020 ◽  
Vol 496 (3) ◽  
pp. 3531-3552 ◽  
Author(s):  
A R Gogate ◽  
M A W Verheijen ◽  
B Z Deshev ◽  
J H van Gorkom ◽  
M Montero-Castaño ◽  
...  
Keyword(s):  
Galaxy Evolution ◽  
Large Scale ◽  
Neutral Hydrogen ◽  
Integration Time ◽  
Wide Field ◽  
Imaging Data ◽  
Isaac Newton ◽  
Detection Techniques ◽  
Density Maps ◽  
Line Imaging

ABSTRACT In this paper, we present data from the Blind Ultra-Deep H i Environmental Survey (BUDHiES), which is a blind 21-cm H i spectral line imaging survey undertaken with the Westerbork Synthesis Radio Telescope. Two volumes were surveyed, each with a single pointing and covering a redshift range of 0.164 < z < 0.224. Within these two volumes, this survey targeted the clusters Abell 963 and Abell 2192, which are dynamically different and offer unique environments to study the process of galaxy evolution within clusters. With an integration time of 117 × 12 h on Abell 963 and 72 × 12 h on Abell 2192, a total of 166 galaxies were detected and imaged in H i. While the clusters themselves occupy only 4 per cent of the 73 400 Mpc3 surveyed by BUDHiES, most of the volume consists of large-scale structures in which the clusters are embedded, including foreground and background overdensities and voids. We present the data processing and source detection techniques and counterpart identification based on a wide-field optical imaging survey using the Isaac Newton Telescope and deep ultraviolet (UV) Galaxy Evolution Explorer (GALEX) imaging. Finally, we present H i and optical catalogues of the detected sources as well as atlases of their global H i properties, which include integrated column density maps, position–velocity diagrams, global H i profiles, and optical and UV images of the H i sources.

scholarly journals Do AGN triggering mechanisms vary with radio power? – I. Optical morphologies of radio-intermediate HERGs

2019 ◽  
Vol 487 (4) ◽  
pp. 5490-5507 ◽  
Author(s):  
J C S Pierce ◽  
C N Tadhunter ◽  
C Ramos Almeida ◽  
P S Bessiere ◽  
M Rose
Keyword(s):  
Galaxy Evolution ◽  
Large Scale ◽  
Elliptical Galaxy ◽  
Optical Emission ◽  
Imaging Data ◽  
High Excitation ◽  
Late Type ◽  
Host Galaxies ◽  
Triggering Mechanisms ◽  
Radio Power

ABSTRACT Active galactic nuclei (AGNs) with intermediate radio powers are capable of driving multiphase outflows in galaxy bulges, and are also more common than their high-radio-power counterparts. In-depth characterization of the typical host galaxies and likely triggering mechanisms for this population is therefore required in order to better understand the role of radio AGN feedback in galaxy evolution. Here, we use deep optical imaging data to study the detailed host morphologies of a complete sample of 30 local radio AGNs with high-excitation optical emission (HERG) spectra and intermediate radio powers [ z < 0.1; 22.5 < log($L_{\rm 1.4GHz}$) < 24.0 W Hz-1]. The fraction of hosts with morphological signatures of mergers and interactions is greatly reduced compared to the 2Jy radio-powerful galaxies [log($L_{\rm 1.4GHz}$) > 25.0 W Hz-1] with strong optical emission lines: 53 ± 9 per cent compared with 94 ± 4 per cent. In addition, the most radio-powerful half of the sample has a higher frequency of morphological disturbance than the least radio-powerful half (67 ± 12 per cent and 40 ± 13 per cent, respectively), including the eight most highly disturbed galaxies. This suggests that the importance of triggering nuclear activity in high-excitation radio galaxies (HERGs) through mergers and interactions reduces with radio power. Both visual inspection and detailed light profile modelling reveal a mixed population of early-type and late-type morphologies, contrary to the massive elliptical galaxy hosts of radio-powerful AGNs. The prevalence of late-type hosts could suggest that triggering via secular, disc-based processes has increased importance for HERGs with lower radio powers (e.g. disc instabilities and large-scale bars).

scholarly journals Quantifying EoR delay spectrum contamination from diffuse radio emission

2020 ◽  
Vol 494 (3) ◽  
pp. 3712-3727 ◽  
Author(s):  
Adam E Lanman ◽  
Jonathan C Pober ◽  
Nicholas S Kern ◽  
Eloy de Lera Acedo ◽  
David R DeBoer ◽  
...  
Keyword(s):  
Radio Emission ◽  
Large Scale ◽  
Power Spectra ◽  
Neutral Hydrogen ◽  
Spectral Structure ◽  
Wide Field ◽  
Electromagnetic Simulations ◽  
The Galaxy ◽  
Spectral Weighting ◽  
The Universe

ABSTRACT The 21 cm hyperfine transition of neutral hydrogen offers a promising probe of the large-scale structure of the universe before and during the Epoch of Reionization (EoR), when the first ionizing sources formed. Bright radio emission from foreground sources remains the biggest obstacle to detecting the faint 21 cm signal. However, the expected smoothness of foreground power leaves a clean window in Fourier space where the EoR signal can potentially be seen over thermal noise. Though the boundary of this window is well defined in principle, spectral structure in foreground sources, instrumental chromaticity, and choice of spectral weighting in analysis all affect how much foreground power spills over into the EoR window. In this paper, we run a suite of numerical simulations of wide-field visibility measurements, with a variety of diffuse foreground models and instrument configurations, and measure the extent of contaminated Fourier modes in the EoR window using a delay-transform approach to estimate power spectra. We also test these effects with a model of the Hydrogen Epoch of Reionization Array (HERA) antenna beam generated from electromagnetic simulations, to take into account further chromatic effects in the real instrument. We find that foreground power spillover is dominated by the so-called pitchfork effect, in which diffuse foreground power is brightened near the horizon due to the shortening of baselines. As a result, the extent of contaminated modes in the EoR window is largely constant over time, except when the Galaxy is near the pointing centre.

scholarly journals MAMMOTH: confirmation of two massive galaxy overdensities at z = 2.24 with Hα emitters

2020 ◽  
Vol 500 (4) ◽  
pp. 4354-4364
Author(s):  
Xian Zhong Zheng ◽  
Zheng Cai ◽  
Fang Xia An ◽  
Xiaohui Fan ◽  
Dong Dong Shi
Keyword(s):  
Star Formation ◽  
Large Scale ◽  
Formation Rate ◽  
Broad Band ◽  
Infrared Camera ◽  
Wide Field ◽  
Imaging Data ◽  
Filamentary Structure ◽  
Dominant Structure ◽  
Massive Galaxy

ABSTRACT Massive galaxy overdensities at the peak epoch of cosmic star formation provide ideal testbeds for the formation theories of galaxies and large-scale structure. We report the confirmation of two massive galaxy overdensities at z = 2.24, BOSS1244 and BOSS1542, selected from the Mapping the Most Massive Overdensities Through Hydrogen (MAMMOTH) project using Lyα absorption from the intergalactic medium over the scales of 15−30 h−1 Mpc imprinted on the quasar spectra. We use Hα emitters (HAEs) as the density tracer and identify them using deep narrow-band H2S(1) and broad-band Ks imaging data obtained with the wide-field infrared camera (WIRCam) at the Canada–France–Hawaii Telescope. In total, 244 and 223 line emitters are detected in these two fields, and 196 ± 2 and 175 ± 2 are expected to be HAEs with an Hα flux of &gt;2.5 × 10−17 erg s−1 cm−2 (corresponding to a star formation rate of &gt;5 M⊙ yr−1). The detection rate of HAE candidates suggests an overdensity factor of δgal = 5.6 ± 0.3 and 4.9 ± 0.3 over the volume of 54 × 32 × 32 co-moving Mpc3. The overdensity factor increases two to three times when focusing on the high-density regions of scales 10–15  co-moving Mpc. Interestingly, the HAE density maps reveal that BOSS1244 contains a dominant structure, while BOSS1542 manifests as a giant filamentary structure. We measure the Hα luminosity functions (HLFs), finding that BOSS1244’s HLF is nearly identical to that of the general field at the same epoch, while BOSS1542 shows an excess of HAEs with high Hα luminosity, indicating the presence of enhanced star formation or active galactic nuclei activity. We conclude that the two massive MAMMOTH overdensities are undergoing a rapid galaxy mass assembly.

scholarly journals The escape fraction of ionizing photons during the Epoch of Reionization: observability with the Square Kilometre Array

2019 ◽  
Vol 487 (4) ◽  
pp. 5739-5752 ◽  
Author(s):  
Jacob Seiler ◽  
Anne Hutter ◽  
Manodeep Sinha ◽  
Darren Croton
Keyword(s):  
Power Spectrum ◽  
Galaxy Evolution ◽  
Optical Depth ◽  
Large Scale ◽  
Low Frequency ◽  
Integration Time ◽  
Square Kilometre Array ◽  
Exciting Opportunity ◽  
Functional Forms ◽  
The Impact

Abstract One of the most important parameters in characterizing the Epoch of Reionization, the escape fraction of ionizing photons, fesc, remains unconstrained both observationally and theoretically. With recent work highlighting the impact of galaxy-scale feedback on the instantaneous value of fesc, it is important to develop a model in which reionization is self-consistently coupled to galaxy evolution. In this work, we present such a model and explore how physically motivated functional forms of fesc affect the evolution of ionized hydrogen within the intergalactic medium. Using the 21 cm power spectrum evolution, we investigate the likelihood of observationally distinguishing between a constant fesc and other models that depend upon different forms of galaxy feedback. We find that changing the underlying connection between fesc and galaxy feedback drastically alters the large-scale 21 cm power. The upcoming Square Kilometre Array Low Frequency instrument possesses the sensitivity to differentiate between our models at a fixed optical depth, requiring only 200 h of integration time focused on redshifts z = 7.5–8.5. Generalizing these results to account for a varying optical depth will require multiple 800 h observations spanning redshifts z = 7–10. This presents an exciting opportunity to observationally constrain one of the most elusive parameters during the Epoch of Reionization.

scholarly journals Neutral hydrogen in the post-reionization universe

2017 ◽  
Vol 12 (S333) ◽  
pp. 216-221
Author(s):  
Hamsa Padmanabhan
Keyword(s):  
Galaxy Evolution ◽  
Large Scale ◽  
Neutral Hydrogen ◽  
Lyman Alpha ◽  
Intensity Mapping ◽  
Best Fitting ◽  
Hydrodynamical Simulations ◽  
Intermediate Redshift ◽  
Intermediate Redshifts ◽  
The Universe

AbstractThe evolution of neutral hydrogen (HI) across redshifts is a powerful probe of cosmology, large scale structure in the universe and the intergalactic medium. Using a data-driven halo model to describe the distribution of HI in the post-reionization universe (z ∼ 5 to 0), we obtain the best-fitting parameters from a rich sample of observational data: low redshift 21-cm emission line studies, intermediate redshift intensity mapping experiments, and higher redshift Damped Lyman Alpha (DLA) observations. Our model describes the abundance and clustering of neutral hydrogen across redshifts 0 - 5, and is useful for investigating different aspects of galaxy evolution and for comparison with hydrodynamical simulations. The framework can be applied for forecasting future observations with neutral hydrogen, and extended to the case of intensity mapping with molecular and other line transitions at intermediate redshifts.

scholarly journals The small-scale structure of the Magellanic stream as a foundation for galaxy evolution

2010 ◽  
pp. 1-10 ◽  
Author(s):  
S. Stanimirovic ◽  
J.S.III Gallagher ◽  
L. Nigra
Keyword(s):  
Galaxy Evolution ◽  
Large Scale ◽  
Critical Role ◽  
Neutral Hydrogen ◽  
Scale Structure ◽  
Small Scale ◽  
Small Scale Structure ◽  
Northern Portion ◽  
Cool Gas ◽  
Magellanic Stream

The Magellanic Stream (MS) is the nearest example of a gaseous trail formed by interacting galaxies. While the substantial gas masses in these kinds of circumgalactic structures are postulated to represent important sources of fuel for future star formation, the mechanisms whereby this material might be accreted back into galaxies remain unclear. Recent neutral hydrogen (HI) observations have demonstrated that the northern portion of the MS, which probably has been interacting with the Milky Way's hot gaseous halo for close to 1000 Myr, has a larger spatial extent than previously recognized, while also containing significant amounts of small-scale structure. After a brief consideration of the large-scale kinematics of the MS as traced by the recently-discovered extension of the MS, we explore the aging process of the MS gas through the operation of various hydrodynamic instabilities and interstellar turbulence. This in turn leads to consideration of processes whereby MS material survives as cool gas, and yet also evidently fails to form stars. Parallels between the MS and extragalactic tidal features are brie'y discussed with an emphasis on steps toward establishing what the MS reveals about the critical role of local processes in determining the evolution of these kinds of systems.

scholarly journals Establishing a new technique for discovering large-scale structure using the ORELSE survey

2019 ◽  
Vol 491 (4) ◽  
pp. 5524-5554 ◽  
Author(s):  
D Hung ◽  
B C Lemaux ◽  
R R Gal ◽  
A R Tomczak ◽  
L M Lubin ◽  
...  
Keyword(s):  
Galaxy Evolution ◽  
Large Scale ◽  
High Redshift ◽  
Voronoi Tessellation ◽  
New Technique ◽  
Wide Field ◽  
Large Scale Structures ◽  
A New Technique ◽  
Rich Data ◽  
Field Galaxy

ABSTRACT The Observations of Redshift Evolution in Large-Scale Environments (ORELSE) survey is an ongoing imaging and spectroscopic campaign initially designed to study the effects of environment on galaxy evolution in high-redshift (z ∼ 1) large-scale structures. We use its rich data in combination with a powerful new technique, Voronoi tessellation Monte Carlo (VMC) mapping, to search for serendipitous galaxy overdensities at 0.55 &lt; z &lt; 1.37 within 15 ORELSE fields, a combined spectroscopic footprint of ∼1.4 deg2. Through extensive tests with both observational data and our own mock galaxy catalogues, we optimize the method’s many free parameters to maximize its efficacy for general overdensity searches. Our overdensity search yielded 402 new overdensity candidates with precisely measured redshifts and an unprecedented sensitivity down to low total overdensity masses ($\mathcal {M}_{\mathrm{ tot}}\gtrsim5\times 10^{13}$ M⊙). Using the mock catalogues, we estimated the purity and completeness of our overdensity catalogue as a function of redshift, total mass, and spectroscopic redshift fraction, finding impressive levels of both 0.92/0.83 and 0.60/0.49 for purity/completeness at z = 0.8 and z = 1.2, respectively, for all overdensity masses at spectroscopic fractions of ∼20 per cent. With VMC mapping, we are able to measure precise systemic redshifts, provide an estimate of the total gravitating mass, and maintain high levels of purity and completeness at z ∼ 1 even with only moderate levels of spectroscopy. Other methods (e.g. red-sequence overdensities and hot medium reliant detections) begin to fail at similar redshifts, which attests to VMC mapping’s potential to be a powerful tool for current and future wide-field galaxy evolution surveys at z ∼ 1 and beyond.

scholarly journals The environments of radio-loud AGN from the LOFAR Two-Metre Sky Survey (LoTSS)

2019 ◽  
Vol 622 ◽  
pp. A10 ◽  
Author(s):  
J. H. Croston ◽  
M. J. Hardcastle ◽  
B. Mingo ◽  
P. N. Best ◽  
J. Sabater ◽  
...  
Keyword(s):  
Galaxy Evolution ◽  
Large Scale ◽  
Life Cycles ◽  
Sloan Digital Sky Survey ◽  
Host Galaxy ◽  
Imaging Data ◽  
Radio Luminosity ◽  
Sky Survey ◽  
Luminous Objects

An understanding of the relationship between radio-loud active galaxies and their large-scale environments is essential for realistic modelling of radio-galaxy evolution and environmental impact, for understanding AGN triggering and life cycles, and for calibrating galaxy feedback in cosmological models. We use the LOFAR Two-Metre Sky Survey (LoTSS) Data Release 1 catalogues to investigate this relationship. We cross-matched a sample of 8745 radio-loud AGN with 0.08 <  z <  0.4, selected from LoTSS, with two Sloan Digital Sky Survey (SDSS) cluster catalogues, and find that only 10 percent of LoTSS AGN in this redshift range have a high-probability association, so that the majority of low-redshift AGN (including a substantial fraction of the most radio-luminous objects) must inhabit haloes with M <  1014 M⊙. We find that the probability of a cluster association, and the richness of the associated cluster, is correlated with AGN radio luminosity, and we also find that, for the cluster population, the number of associated AGN and the radio luminosity of the brightest associated AGN is richness-dependent. We demonstrate that these relations are not driven solely by host-galaxy stellar mass, supporting models in which large-scale environment is influential in driving AGN jet activity in the local Universe. At the lowest radio luminosities we find that the minority of objects with a cluster association are located at larger mean cluster-centre distances than more luminous AGN, an effect that appears to be driven primarily by host-galaxy mass. Finally, we also find that FRI radio galaxies inhabit systematically richer environments than FRIIs, consistent with previous work. The work presented here demonstrates the potential of LoTSS for AGN environmental studies. In future, the full northern-sky LoTSS catalogue, together with the use of deeper optical/IR imaging data and spectroscopic follow-up with WEAVE-LOFAR, will provide opportunities to extend this type of work to much larger samples and higher redshifts.

scholarly journals Detecting the neutral IGM in filaments with the SKA

2019 ◽  
Vol 490 (1) ◽  
pp. 1415-1424 ◽  
Author(s):  
Robin Kooistra ◽  
Marta B Silva ◽  
Saleem Zaroubi ◽  
Marc A W Verheijen ◽  
Elmo Tempel ◽  
...  
Keyword(s):  
Large Scale ◽  
Direct Detection ◽  
Neutral Hydrogen ◽  
Integration Time ◽  
Radio Telescopes ◽  
Signal To Noise ◽  
Galaxy Surveys ◽  
Recent Developments ◽  
Formation And Evolution ◽  
Square Kilometer Array

ABSTRACTThe intergalactic medium (IGM) plays an important role in the formation and evolution of galaxies. Recent developments in upcoming radio telescopes are starting to open up the possibility of making a first direct detection of the 21 cm signal of neutral hydrogen (H i) from the warm gas of the IGM in large-scale filaments. The cosmological hydrodynamical EAGLE simulation is used to estimate the typical IGM filament signal. Assuming the same average signal for all filaments, a prediction is made for the detectability of such a signal with the upcoming mid-frequency array of the Square Kilometer Array (SKA1-mid) or the future upgrade to SKA2. The signal to noise (S/N) then only depends on the size and orientation of each filament. With filament spines inferred from existing galaxy surveys as a proxy for typical real filaments, we find hundreds of filaments in the region of the sky accessible to the SKA that can be detected. Once the various phases of the SKA telescope become operational, their own surveys will be able to find the galaxies required to infer the position of even more filaments within the survey area. We find that in 120 h, SKA1-mid/SKA2 will detect H i emission from the strongest filaments in the field with an S/N of the order of 10 to ∼150 for the most pessimistic model considered here. Some of the brighter filaments can be detected with an integration time of a few minutes with SKA1-mid and a few seconds with SKA2. Therefore, SKA2 will be capable of not only detecting but also mapping a large part of the IGM in these filaments.

scholarly journals Mapping brain structural differences and neuroreceptor correlates in Parkinson’s disease visual hallucinations: a mega-analysis

2021 ◽  
Author(s):  
Miriam Vignando ◽  
Dominic ffytche ◽  
Simon Lewis ◽  
Phil Hyu Lee ◽  
Seok Chung ◽  
...  
Keyword(s):  
Parkinson’S Disease ◽  
Parkinson's Disease ◽  
Empirical Bayes ◽  
Large Scale ◽  
Visual Hallucinations ◽  
Imaging Data ◽  
Control Networks ◽  
Density Maps ◽  
Cortical Regions ◽  
Cortical Involvement

Abstract Parkinson’s psychosis (PDP) describes a spectrum of symptoms that may arise in Parkinson’s disease (PD) including visual hallucinations (VH). Imaging studies investigating the neural correlates of PDP have been inconsistent in their findings, due to differences in study design and limitations of scale. Here we use empirical Bayes harmonisation to pool together structural imaging data from multiple research groups into a large-scale mega-analysis, allowing us to apply new methodological approaches to identify cortical regions and networks involved in VH and their relation to receptor binding. Differences of cortical thickness and surface area show a wider cortical involvement underlying VH than previously recognised, including primary visual cortex and its surrounds, and the hippocampus, independent of its role in cognitive decline. Structural covariance analyses point to a strong involvement of the attentional control networks in PD-VH, while associations with receptor density maps suggest neurotransmitter loss may drive the cortical changes.

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