Despite decades of study, it remains unclear whether there are distinct radio-loud and radio-quiet populations of quasi-stellar objects (QSOs). Early studies were limited by inhomogeneous QSO ...samples, inadequate sensitivity to probe the radio-quiet population, and degeneracy between redshift and luminosity for flux-density-limited samples. Our new 6 GHz Expanded Very Large Array (EVLA) observations allow us for the first time to obtain nearly complete (97%) radio detections in a volume-limited color-selected sample of 179 QSOs more luminous than Mi = --23 from the Sloan Digital Sky Survey (SDSS) Data Release Seven in the narrow redshift range 0.2 < z < 0.3. The dramatic improvement in radio continuum sensitivity made possible with the new EVLA allows us, in 35 minutes of integration, to detect sources as faint as 20 Delta *mJy, or log L 6 GHz(W Hz--1) 21.5 at z = 0.25, well below the radio luminosity, log L 6(W Hz--1) 22.5, that separates star-forming galaxies from radio-loud active galactic nuclei (AGNs) driven by accretion onto a supermassive black hole. We calculate the radio luminosity function (RLF) for these QSOs using three constraints: (1) EVLA 6 GHz observations for log L 6(W Hz--1) < 23.5, (2) NRAO-VLA Sky Survey observations for log L 6(W Hz--1) > 23.5, and (3) the total number of SDSS QSOs in our volume-limited sample. We show that the RLF can be explained as a superposition of two populations, dominated by AGNs at the bright end and star formation in the QSO host galaxies at the faint end.
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.
Abstract
We present analysis of a homogeneous, optically selected, volume-limited (0.2 <
z
< 0.3) sample of 128 radio-quiet quasi-stellar objects (QSOs) recently observed at 6 GHz with the Very Large ...Array (VLA) in A configuration (∼0.″33 resolution). We compare these new results to earlier (2010–2011) 6 GHz observations with the VLA in C configuration (∼3.″5). While all of these radio-quiet QSOs (RQQs) were unresolved on a 3.″5 scale (∼14 kpc at
z
= 0.25), we resolve notable complex subgalactic structures in about half of the RQQs at 0.″33 resolution (∼1.3 kpc at
z
= 0.25). By comparison of flux density measurements between the two sets of observations, we demonstrate that significant sub-galactic-scale radio structure is present in at least 70% of the RQQ population and that the central component accounts for an average of ≈65% of the total detected radio power. One RQQ, J0935+4819, shows striking symmetric, double-lobed morphology and appears to be the first identified example of a radio-
quiet
QSO with FR II type morphology on ∼arcsec scale (projected size of ≳6 kpc). In addition to revealing RQQ subgalactic morphology, we employ counterparts from legacy (FIRST at 1.4 GHz) and recent (VLA Sky Survey at 3 GHz) VLA surveys to investigate radio spectral indices and potential variability over decades-long timescales for a subset of the RQQs and for the cores of radio-intermediate and radio-loud sources in the parent sample of 178 QSOs. These results support the growing notion that the RQQ population is not a monolithic phenomenon but instead consists of a mixture of mainly starburst-powered and jet-powered galaxies.
We have performed a search over 3440 deg2 of Epoch 1 (2017-2019) of the Very Large Array Sky Survey to identify unobscured quasars in the optical (0.2 < z < 3.2) and obscured active galactic nuclei ...(AGNs) in the infrared that have brightened dramatically in the radio over the past one to two decades. These sources would have been previously classified as "radio-quiet" quasars based on upper limits from the Faint Images of the Radio Sky at Twenty cm survey (1993-2011), but they are now consistent with "radio-loud" quasars ( ). A quasi-simultaneous, multiband (∼1-18 GHz) follow-up study of 14 sources with the VLA has revealed compact sources (<0 1 or <1 kpc) with peaked radio spectral shapes. The high-amplitude variability over decadal timescales at 1.5 GHz (100% to >2500%) but roughly steady fluxes over a few months at 3 GHz are inconsistent with extrinsic variability due to propagation effects, thus favoring an intrinsic origin. We conclude that our sources are powerful quasars hosting compact/young jets. This challenges the generally accepted idea that "radio-loudness" is a property of the quasar/AGN population that remains fixed on human timescales. Our study suggests that frequent episodes of short-lived AGN jets that do not necessarily grow to large scales may be common at high redshift. We speculate that intermittent but powerful jets on subgalactic scales could interact with the interstellar medium, possibly driving feedback capable of influencing galaxy evolution.
We used the 1.4 GHz NVSS to study radio sources in two color-selected QSO samples: a volume-limited sample of 1313 QSOs defined by M sub(i) < -23 in the redshift range 0.2 < z < 0.45 and a ...magnitude-limited sample of 2471 QSOs with m sub(r) < or =, slant 18.5 and 1.8 < z < 2.5. About 10% were detected above the 2.4 mJy NVSS catalog limit and are powered primarily by active galactic nuclei (AGNs). The space density of the low-redshift QSOs evolves as rho is proportional to (1 + z)6. In both redshift ranges the flux-density distributions and luminosity functions of QSOs stronger than 2.4 mJy are power laws, with no features to suggest more than one kind of radio source. Extrapolating the power laws to lower luminosities predicts the remaining QSOs should be extremely radio quiet, but they are not. Most were detected statistically on the NVSS images with median peak flux densities S sub(p)(mJy beam super(-1)) approximate 0.3 and 0.05 in the low- and high-redshift samples, corresponding to spectral luminosities logL sub(1.4GHz)(W Hz super(-1)) approximate 22.7 and 24.1, respectively. We suggest that the faint radio sources are powered by star formation at rates M ~ 20 M sub(middot in circle) yr super(-1) in the moderate luminosity (median left angle bracketM sub(i)right angle bracket approximate -23.4) low-redshift QSOs and M ~ 500 M sub(middot in circle) yr super(-1) in the very luminous (left angle bracketM sub(i)right angle bracket approximate -27.5) high-redshift QSOs. Such luminous starbursts left angle bracketlog(L sub(IR)/L sub(middot in circle))right angle bracket ~ 11.2 and 12.6, respectively are consistent with "quasar mode" accretion in which cold gas flows fuel both AGN and starburst.
We present new subarcsecond-resolution Karl G. Jansky Very Large Array (VLA) imaging at 10 GHz of 155 ultraluminous (Lbol ∼ 1011.7-1014.2 L ) and heavily obscured quasars with redshifts z ∼ 0.4-3. ...The sample was selected to have extremely red mid-infrared-optical color ratios based on data from the Wide-Field Infrared Survey Explorer (WISE) along with a detection of bright, unresolved radio emission from the NRAO VLA Sky Survey (NVSS) or Faint Images of the Radio Sky at Twenty cm Survey. Our high-resolution VLA observations have revealed that the majority of the sources in our sample (93 out of 155) are compact on angular scales <0 2 (≤1.7 kpc at z ∼ 2). The radio luminosities, linear extents, and lobe pressures of our sources are similar to young radio active galactic nuclei (e.g., gigahertz-peaked spectrum GPS and compact steep-spectrum CSS sources), but their space density is considerably lower. Application of a simple adiabatic lobe expansion model suggests relatively young dynamical ages (∼104-7 yr), relatively high ambient ISM densities (∼1-104 cm−3), and modest lobe expansion speeds (∼30-10,000 km s−1). Thus, we find our sources to be consistent with a population of newly triggered, young jets caught in a unique evolutionary stage in which they still reside within the dense gas reservoirs of their hosts. Based on their radio luminosity function and dynamical ages, we estimate that only ∼20% of classical large-scale FR I/II radio galaxies could have evolved directly from these objects. We speculate that the WISE-NVSS sources might first become GPS or CSS sources, of which some might ultimately evolve into larger radio galaxies.
Abstract
We present radio spectra spanning 0.1–10 GHz for the sample of heavily obscured luminous quasars with extremely red mid-infrared-optical colors and compact radio emission. The spectra are ...constructed from targeted 10 GHz observations and archival radio survey data that together yield 6–11 flux-density measurements for each object. Our primary result is that most (62%) of the sample have peaked or curved radio spectra and many (37%) could be classified as Gigahertz-Peaked Spectrum (GPS) sources. This indicates compact emission regions likely arising from recently triggered radio jets. Assuming synchrotron self-absorption (SSA) generates the peaks, we infer compact source sizes (3–100 pc) with strong magnetic fields (6–100 mG) and young ages (30–10
4
yr). Conversely, free-free absorption (FFA) could also create peaks due to the high column densities associated with the deeply embedded nature of the sample. However, we find no correlations between the existence or frequency of the peaks and any parameters of the MIR emission. The high-frequency spectral indices are steep (
α
≈ −1) and correlate, weakly, with the ratio of MIR photon energy density to magnetic energy density, suggesting that the spectral steepening could arise from inverse Compton scattering off the intense MIR photon field. This study provides a foundation for combining multifrequency and mixed-resolution radio survey data for understanding the impact of young radio jets on the ISM and star-formation rates of their host galaxies.
faGithub
Background
Proprotein convertase subtilisin/kexin type 9 (PCSK9) is a key regulator of low‐density lipoprotein cholesterol and cardiovascular disease risk, and is an emerging therapeutic target.
...Objective
We compared serum PCSK9 levels in young adults, with and without type 2 diabetes.
Subjects and methods
Cross‐sectional analysis was conducted in a cohort, aged 15 to 26 years, in Cincinnati, OH, from 2005 to 2010. Serum PCSK9 levels were measured in 94 youth with type 2 diabetes, 93 obese control subjects, and 99 lean control subjects. Correlative analyses were conducted to determine significant covariates of PCSK9 by group and sex, and multivariate linear regression models were used to study the independent determinants of PCSK9.
Results
In females, PCSK9 levels were significantly increased in the obese and type 2 diabetes subjects relative to the lean controls (P < .01). Moreover, PCSK9 was positively correlated with multiple metabolic parameters in females: body mass index, systolic blood pressure, fasting glucose, fasting insulin, and C‐reactive protein levels (P ≤ .02). In males, PCSK9 levels were decreased overall compared with females (P = .03), and did not differ between the lean, obese, or type 2 diabetes groups.
Conclusions
Obesity and type 2 diabetes were associated with significantly higher levels of PCSK9 in young women, but not in young men. These data suggest that sex could modify the effects of obesity and diabetes on PCSK9 in young adults.
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