Abstract
The Very Large Array Sky Survey (VLASS) is observing the entire sky north of −40° in the
S
band (2 GHz <
ν
< 4 GHz), with the highest angular resolution (2.″5) of any all-sky radio continuum ...survey to date. VLASS will cover its entire footprint over three distinct epochs, the first of which has now been observed in full. Based on
Quick Look
images from this first epoch, we have created a catalog of 1.9 × 10
6
reliably detected radio components. Due to the limitations of the
Quick Look
images, component flux densities are underestimated by ∼15% at
S
peak
> 3 mJy beam
−1
and are often unreliable for fainter components. We use this catalog to perform statistical analyses of the
ν
∼ 3 GHz radio sky. Comparisons with the Faint Images of the Radio Sky at Twenty-Centimeters (FIRST) survey show the typical 1.4–3 GHz spectral index,
α
, to be ∼−0.71. The radio color–color distribution of point and extended components is explored by matching with FIRST and the LOFAR Two-meter Sky Survey. We present the VLASS source counts,
dN
/
dS
, which are found to be consistent with previous observations at 1.4 and 3 GHz. Resolution improvements over FIRST result in excess power in the VLASS two-point correlation function at angular scales ≲7″, and in 18% of active galactic nuclei associated with a single FIRST component being split into multicomponent sources by VLASS.
Prevalence of certain forms of psychopathology, such as autism and depression, differs between genders and understanding gender differences of the neurotypical brain may provide insights into risk ...and protective factors. In recent research, resting state functional magnetic resonance imaging (rfMRI) is widely used to map the inherent functional networks of the brain. Although previous studies have reported gender differences in rfMRI, the robustness of gender differences is not well characterized. In this study, we use a large data set to test whether rfMRI functional connectivity (FC) can be used to predict gender and identify FC features that are most predictive of gender. We utilized rfMRI data from 820 healthy controls from the Human Connectome Project. By applying a predefined functional template and partial least squares regression modeling, we achieved a gender prediction accuracy of 87% when multi‐run rfMRI was used. Permutation tests confirmed that gender prediction was reliable (
p<.001). Effects of motion, age, handedness, blood pressure, weight, and brain volume on gender prediction are discussed. Further, we found that FC features within the default mode (DMN), fronto‐parietal and sensorimotor networks contributed most to gender prediction. In the DMN, right fusiform gyrus and right ventromedial prefrontal cortex were important contributors. The above regions have been previously implicated in aspects of social functioning and this suggests potential gender differences in social cognition mediated by the DMN. Our findings demonstrate that gender can be reliably predicted using rfMRI data and highlight the importance of controlling for gender in brain imaging studies.
ABSTRACT We have detected in ALMA observations CO emission from the nucleus of the Seyfert galaxy NGC 1068. The low-velocity (up to 70 km s−1 relative to systemic) CO emission resolves into a 12 × 7 ...pc structure, roughly aligned with the nuclear radio source. Higher-velocity emission (up to 400 km s−1) is consistent with a bipolar outflow in a direction nearly perpendicular ( 80°) to the nuclear disk. The position-velocity diagram shows that in addition to the outflow, the velocity field may also contain rotation about the disk axis. These observations provide compelling evidence in support of the disk-wind scenario for the active galactic nucleus obscuring torus.
We present 1.4 pc resolution observations of 256 GHz nuclear radio continuum and HCN (J = 3 → 2) in the molecular torus of NGC 1068. The integrated radio continuum emission has a flat spectrum ...consistent with free-free emission and resolves into an X-shaped structure resembling an edge-brightened bicone. HCN is detected in absorption against the continuum, and the absorption spectrum shows a pronounced blue wing that suggests a high-velocity molecular outflow with speeds reaching 450 km s−1. Analysis of the off-nucleus emission line kinematics and morphology reveals two nested, rotating disk components. The inner disk, inside r ∼ 1.2 pc, has kinematics that are consistent with the nearly edge-on, geometrically thin H2O megamaser disk in Keplerian rotation around a central mass of 1.66 × 107 M . The outer disk, which extends to ∼7 pc radius, counter-rotates relative to the inner disk. The rotation curve of the outer disk is consistent with rotation around the same central mass as the megamaser disk but in the opposite sense. The morphology of the molecular gas is asymmetric around the nuclear continuum source. We speculate that the outer disk formed from more recently introduced molecular gas falling out of the host galaxy or from a captured dwarf satellite galaxy. In NGC 1068, we find direct evidence that the molecular torus consists of counter-rotating and misaligned disks on parsec scales.
While static functional connectivity (sFC) of resting state fMRI (rfMRI) measures the average functional connectivity (FC) over the entire rfMRI scan, dynamic FC (dFC) captures the temporal ...variations of FC at shorter time windows. Although numerous studies have implemented dFC analyses, only a few studies have investigated the reliability of dFC and this limits the biological interpretation of dFC. Here, we used a large cohort (N = 820) of subjects and four rfMRI scans from the Human Connectome Project to systematically explore the relationship between sFC, dFC and their test-retest reliabilities through intra-class correlation (ICC). dFC ICC was explored through the sliding window approach with three dFC statistics (standard deviation, ALFF, and excursion). Excursion demonstrated the highest dFC ICC and the highest age prediction accuracy. dFC ICC was generally higher at window sizes less than 40 s. sFC and dFC were negatively correlated. Compared to sFC, dFC was less reliable. While sFC and sFC ICC were positively correlated, dFC and dFC ICC were negatively correlated, indicating that FC that was more dynamic was less reliable. Intra-network FCs in the frontal-parietal, default mode, sensorimotor and visual networks demonstrated high sFC and low dFC. Moreover, ICCs of both sFC and dFC in these regions were higher. The above results were consistent across two brain atlases and independent component analysis-based networks, multiple window sizes and all three dFC statistics. In summary, dFC is less reliable than sFC and additional experiments are required to better understand the neurophysiological relevance of dFC.
•Test-retest reliability of rfMRI dynamic functional connectivity (dFC) is examined.•Reliability of sliding window dFC is lower than that of static FC (sFC).•Connections that are more dynamic are less reliable.•A significant positive correlation exists between reliabilities of sFC and dFC.•Application & neurobiological interpretation of dFC requires further investigation.
Low success (<60%) in autism spectrum disorder (ASD) classification using brain morphometry from the large multi-site ABIDE dataset and inconsistent findings on brain morphometric abnormalities in ...ASD can be attributed to the ASD heterogeneity. In this study, we show that ASD brain morphometry is highly heterogeneous, and demonstrate that the heterogeneity can be mitigated and classification improved if autism severity (AS), verbal IQ (VIQ) and age are used with morphometric features. Morphometric features from structural MRIs (sMRIs) of 734 males (ASD: 361, controls: 373) of ABIDE were derived using FreeSurfer. Applying the Random Forest classifier, an AUC of 0.61 was achieved. Adding VIQ and age to morphometric features, AUC improved to 0.68. Sub-grouping the subjects by AS, VIQ and age improved the classification with the highest AUC of 0.8 in the moderate-AS sub-group (AS = 7-8). Matching subjects on age and/or VIQ in each sub-group further improved the classification with the highest AUC of 0.92 in the low AS sub-group (AS = 4-5). AUC decreased with AS and VIQ, and was the lowest in the mid-age sub-group (13-18 years). The important features were mainly from the frontal, temporal, ventricular, right hippocampal and left amygdala regions. However, they highly varied with AS, VIQ and age. The curvature and folding index features from frontal, temporal, lingual and insular regions were dominant in younger subjects suggesting their importance for early detection. When the experiments were repeated using the Gradient Boosting classifier similar results were obtained. Our findings suggest that identifying brain biomarkers in sub-groups of ASD can yield more robust and insightful results than searching across the whole spectrum. Further, it may allow identification of sub-group specific brain biomarkers that are optimized for early detection and monitoring, increasing the utility of sMRI as an important tool for early detection of ASD.
Abstract
Compact steep spectrum (CSS) radio sources are active galactic nuclei (AGN) that have radio jets propagating only on galactic scales, defined as having projected linear size (LS) of up to 20 ...kpc. CSS sources are generally hosted by massive early-type galaxies with little ongoing star formation; however, a small fraction are known to have enhanced star formation. Using archival data from the Faint Images of the Radio Sky at Twenty cm survey, the Very Large Array Sky Survey, and the Sloan Digital Sky Survey, we identify a volume-limited sample of 166 CSS sources at
z
< 0.2 with
L
1.4 GHz
> 10
24
W Hz
−1
. Comparing the star formation rates and linear sizes of these CSS sources, we find that the ≈14% of CSS sources with specific star formation rates above 0.01 Gyr
−1
all have LS < 10 kpc. We discuss the possible mechanisms driving this result, concluding that it is likely the excess star formation in these sources occurred in multiple bursts and ceased prior to the AGN jet being triggered.
Abstract While supermassive black holes are ubiquitous features of galactic nuclei, only a small minority are observed during episodes of luminous accretion. The physical mechanism(s) driving the ...onset of fueling and ignition in these active galactic nuclei (AGN) are still largely unknown for many galaxies and AGN-selection criteria. Attention has focused on AGN triggering by means of major galaxy mergers gravitationally funneling gas toward the galactic center, with evidence both for and against this scenario. However, several recent studies have found that radio-loud AGN overwhelmingly reside in ongoing or recent major galaxy mergers. In this study, we test the hypothesis that major galaxy mergers are important triggers for radio-loud AGN activity in powerful quasars during cosmic noon (1 ≲ z ≲ 2). To this end, we compare Hubble Space Telescope WFC3/IR observations of the z > 1 3CR radio-loud broad-lined quasars to three matched radio-quiet quasar control samples. We find strong evidence for major-merger activity in nearly all radio-loud AGN, in contrast to the much lower merger fraction in the radio-quiet AGN. These results suggest major galaxy mergers are key ingredients in launching powerful radio jets. Given many of our radio-loud quasars are blue, our results present a possible challenge to the “blowout” paradigm of galaxy evolution models in which blue quasars are the quiescent end result following a period of red quasar feedback initiated by a galaxy merger. Finally, we find a tight correlation between black hole mass and host galaxy luminosity for these different high-redshift AGN samples that is inconsistent with those observed for local elliptical galaxies.
Abstract
Active galactic nuclei (AGNs) can often be identified in radio images as two lobes, sometimes connected to a core by a radio jet. This multicomponent morphology unfortunately creates ...difficulties for source finders, leading to components that are (a) separate parts of a wider whole, and (b) offset from the multiwavelength cross identification of the host galaxy. In this work we define an algorithm, DRAGN
hunter
, for identifying double radio sources associated with AGNs (DRAGNs) from component catalog data in the first epoch
Quick Look
images of the high-resolution (≈3″ beam size) Very Large Array Sky Survey (VLASS). We use DRAGN
hunter
to construct a catalog of >17,000 DRAGNs in VLASS for which contamination from spurious sources is estimated at ≈11%. A “high-fidelity” sample consisting of 90% of our catalog is identified for which contamination is <3%. Host galaxies are found for ≈13,000 DRAGNs as well as for an additional 234,000 single-component radio sources. Using these data, we explore the properties of our DRAGNs, finding them to be typically consistent with Fanaroff–Riley class II sources and to allow us to report the discovery of 31 new giant radio galaxies identified using VLASS.
Abstract With two central galaxies engaged in a major merger and a remarkable chain of 19 young stellar superclusters wound around them in projection, the galaxy cluster SDSS J1531+3414 ( z = 0.335) ...offers an excellent laboratory to study the interplay between mergers, active galactic nucleus (AGN) feedback, and star formation. New Chandra X-ray imaging reveals rapidly cooling hot ( T ∼ 10 6 K) intracluster gas, with two “wings” forming a concave density discontinuity near the edge of the cool core. LOFAR 144 MHz observations uncover diffuse radio emission strikingly aligned with the “wings,” suggesting that the “wings” are actually the opening to a giant X-ray supercavity. The steep radio emission is likely an ancient relic of one of the most energetic AGN outbursts observed, with 4 pV > 10 61 erg. To the north of the supercavity, GMOS detects warm ( T ∼ 10 4 K) ionized gas that enshrouds the stellar superclusters but is redshifted up to +800 km s −1 with respect to the southern central galaxy. The Atacama Large Millimeter/submillimeter Array detects a similarly redshifted ∼10 10 M ⊙ reservoir of cold ( T ∼ 10 2 K) molecular gas, but it is offset from the young stars by ∼1–3 kpc. We propose that the multiphase gas originated from low-entropy gas entrained by the X-ray supercavity, attribute the offset between the young stars and the molecular gas to turbulent intracluster gas motions, and suggest that tidal interactions stimulated the “beads-on-a-string” star formation morphology.
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