We present results from multifrequency polarization-sensitive Very Large Array observations of the Seyfert-starburst composite galaxy NGC 3079. Our sensitive radio observations reveal a plethora of ...radio "filaments" comprising the radio lobes in this galaxy. We analyze the origin of these radio filaments in the context of existing Chandra X-ray and HST emission-line data. We do not find a one-to-one correlation of the radio filaments with the emission-line filaments. The northeastern lobe is highly polarized with polarization fractions ∼33% at 5 GHz. The magnetic fields are aligned with the linear extents of the optically thin filaments, as observed in our, as well as other, observations in the literature. Our rotation measure images show evidence for rotation measure inversion in the northeastern lobe. Our data best fit a model where the cosmic rays follow the magnetic field lines generated as a result of the dynamo mechanism. There could be additional effects like shock acceleration that might also be playing a role. We speculate that the peculiar radio lobe morphology is a result of an interplay between both the superwinds and the active galactic nucleus jet that are present in the galaxy. The jet, in fact, might be playing a major role in providing the relativistic electron population that is present in the radio lobes.
This paper presents the analysis of Chandra X-ray snapshot observations of a subsample of the extragalactic sources listed in the revised Third Cambridge radio catalog (3CR), previously lacking X-ray ...observations and thus observed during Chandra Cycle 15. This data set extends the current Chandra coverage of the 3CR extragalactic catalog up to redshift z = 1.0. Our sample includes 22 sources consisting of 1 compact steep spectrum source, 3 quasars (QSOs), and 18 FR II radio galaxies. As in our previous analyses, here we report the X-ray detections of radio cores and extended structures (i.e., knots, hotspots, and lobes) for all sources in the selected sample. We measured their X-ray intensities in three energy ranges, soft (0.5-1 keV), medium (1-2 keV), and hard (2-7 keV), and we also performed standard X-ray spectral analysis for brighter nuclei. All radio nuclei in our sample have an X-ray counterpart. We also discovered X-ray emission associated with the eastern knot of 3CR 154, with radio hotspots in 3CR 41, 3CR 54, and 3CR 225B, and with the southern lobe of 3CR 107. Extended X-ray radiation around the nuclei 3CR 293.1 and 3CR 323 on a scale of few tens of kiloparsecs was also found. X-ray extended emission, potentially arising from the hot gas in the intergalactic medium and/or due to the high-energy counterpart of lobes, is detected for 3CR 93, 3CR 154, 3CR 292, and 3CR 323 over a scale of a few hundred kiloparsecs. Finally, this work also presents an update on the state-of-the-art of Chandra and XMM-Newton observations for the entire 3CR sample.
Abstract
We present a case study of HE 0040-1105, an unobscured radio-quiet active galactic nucleus (AGN) at a high accretion rate of
λ
Edd
= 0.19 ± 0.04. This particular AGN hosts an ionized gas ...outflow with the largest spatial offset from its nucleus compared to all other AGNs in the Close AGN Reference Survey. By combining multiwavelength observations from the Very Large Telescope/MUSE, Hubble Space Telescope/Wide Field Camera 3, Very Large Array, and European VLBI Network, we probe the ionization conditions, gas kinematics, and radio emission from host galaxy scales to the central few parsecs. We detect four kinematically distinct components, one of which is a spatially unresolved AGN-driven outflow located within the central 500 pc, where it locally dominates the interstellar medium conditions. Its velocity is too low to escape the host galaxy’s gravitational potential, and may be re-accreted onto the central black hole via chaotic cold accretion. We detect compact radio emission in HE 0040-1105 within the region covered by the outflow, varying on a timescale of ∼20 yr. We show that neither AGN coronal emission nor star formation processes wholly explain the radio morphology/spectrum. The spatial alignment between the outflowing ionized gas and the radio continuum emission on 100 pc scales is consistent with a weak jet morphology rather than diffuse radio emission produced by AGN winds. >90% of the outflowing ionized gas emission originates from the central 100 pc, within which the ionizing luminosity of the outflow is comparable to the mechanical power of the radio jet. Although radio jets might primarily drive the outflow in HE 0040-1105, radiation pressure from the AGN may contribute to this process.
There is some limited evidence for the presence of viruses in herniated disc material including a previous case series that claimed to provide "unequivocal evidence of the presence of herpes virus ...DNA in intervertebral disc specimens of patients with lumbar disc herniation suggesting the potential role of herpes viruses as a contributing factor to the pathogenesis of degenerative disc disease". This study has not been replicated. The objective of our study was to determine if viruses were present in herniated disc fragments in participants with a prior history of back pain.
We recruited fifteen participants with a history of prior low-back pain prior to undergoing disc herniation surgery in the lumbar spine. Harvested disc samples were subject to next generation sequencing for detection of both RNA and DNA viral pathogens. Additionally, samples were analysed by a broadly reactive PCR targeting herpesviral DNA. Ethics approval was granted by the Human Research Ethics Committees of both Murdoch University, and St John of God Hospital, Western Australia.
Of the fifteen research participants, 8 were female. Mean age was 49.4 years (SD 14.5 yrs) with a range of 24-70 years. All participants had prior back pain with mean time since first ever attack being 8.8 years (SD 8.8 yrs). No samples contained significant DNA sequences relating to known human viral agents. Inconsequential retroviral sequences were commonly found and were a mixture of putative animal and human retroviral protein coding segments. All samples were negative for herpesvirus DNA when analysed by pan-herpesvirus PCR.
This study found no viral pathogens in any intervertebral disc fragments of patients who had previous back pain and underwent discectomy for disc herniation and thus it is unlikely that viruses are associated with disc herniation, however given the contradiction between key studies enhanced replication of this experiment is recommended.
We present sensitive, multifrequency Very Long Baseline Array (VLBA) images of the nuclear radio sources of NGC 1068. At 5 and 8.4 GHz, the radio continuum source S1, argued to mark the location of ...the hidden active nucleus, resolves into an elongated, similar to 0.8 pc source oriented nearly at right angles to the radio jet axis but more closely aligned to the distribution of the nuclear H sub(2)O maser spots. S1 is detected at 5 GHz but not at 1.4 GHz, indicating strong free-free absorption below 5 GHz, and it has a flat spectrum between 5 and 8.4 GHz. A 5-8.4 GHz spectral index map reveals an unresolved, inverted spectrum source at the center of the S1 structure that may mark the AGN proper. The average brightness temperature is too low for synchrotron self-absorption to impact the integrated spectrum significantly. In addition, a careful registration with the nuclear H sub(2)O masers argues that the S1 continuum source arises from the inner regions of the maser disk rather than a radio jet. The emission mechanism may be direct, thermal free-free emission from an X-ray-heated corona or wind arising from the molecular disk. We demonstrate that the hidden active nucleus is sufficiently luminous, to within the current estimates, to provide the requisite heating. The radio jet components C and S2 both show evidence for free-free absorption of a compact, steep-spectrum source. The free-free absorption might arise from a shock cocoon enveloping the compact radio sources. The presence of H sub(2)O masers specifically at component C supports the interpretation for the presence of a jet-ISM interaction. Component NE remains a steep-spectrum source on VLBA baselines and appears to be a local enhancement of the synchrotron emissivity of the radio jet. The reason for the enhancement is not clear; the region surrounding component NE is virtually devoid of narrow-line region filaments, and so there is no clear evidence for interaction with the surrounding ISM. Component NE might instead arise in an internal shock or perhaps in denser jet plasma that broke away from an earlier interaction with the circumnuclear ISM.
The aim of this paper is to present an analysis of newly acquired X-ray observations of 16 extragalactic radio sources listed in the Third Cambridge Revised (3CR) catalog and not previously observed ...by Chandra. Observations were performed during Chandra Cycle 17, extending X-ray coverage for the 3CR extragalactic catalog up to z = 1.5. Among the 16 targets, two lie at z < 0.5 (3CR 27 at z = 0.184 and 3CR 69 at z = 0.458); all of the remaining 14 have redshifts between 1.0 and 1.5. In the current sample, there are three compact steep spectrum (CSS) sources, three quasars, and an FR I radio galaxy, while the other nine are FR II radio galaxies. All radio sources have an X-ray counterpart. We measured nuclear X-ray fluxes as well as X-ray emission associated with radio jet knots, hotspots, or lobes in three energy bands: soft (0.5-1 keV), medium (1-2 keV), and hard (2-7 keV). We also performed standard X-ray spectral analysis for the four brightest nuclei. We discovered X-ray emission associated with the radio lobe of 3CR 124, a hotspot of the quasar 3CR 220.2, another hotspot of the radio galaxy 3CR 238, and the jet knot of 3CR 297. We also detected extended X-ray emission around the nuclear region of 3CR 124 and 3CR 297 on scales of several tens of kiloparsecs. Finally, we present an update on the X-ray observations performed with Chandra and XMM-Newton on the entire 3CR extragalactic catalog.
ABSTRACT
We present a new 400 ks Chandra X‐ray observation and a Giant Metrewave Radio Telescope (GMRT) radio observation at 325 MHz of the merging galaxy cluster Abell 2146. The Chandra observation ...reveals detailed structure associated with the major merger event including the Mach M= 2.1 ± 0.2 bow shock located ahead of the dense subcluster core and the first known example of an upstream shock (M= 1.6 ± 0.1). Surprisingly, the deep GMRT observation at 325 MHz does not detect any extended radio emission associated with either shock front. All other merging galaxy clusters with X‐ray‐detected shock fronts, including the Bullet cluster, Abell 520, Abell 754 and Abell 2744, and clusters with candidate shock fronts have detected radio relics or radio halo edges coincident with the shocks. We consider several possible factors which could affect the formation of radio relics, including the shock strength and the presence of a pre‐existing electron population, but do not find a favourable explanation for this result. We calculate a 3σ upper limit of 13 mJy on extended radio emission, which is significantly below the radio power expected by the observed Pradio–LX correlation for merging systems. The lack of an extended radio halo in Abell 2146 maybe due to the low cluster mass relative to the majority of merging galaxy clusters with detected radio haloes.
ABSTRACT We study the cluster environment for a sample of 21 radio loud active galactic nuclei from the 3CR catalog at , 12 radio galaxies (RGs) and nine quasars, with Hubble Space Telescope (HST) ...images in the optical and IR. We use two different approaches to determine cluster candidates. We identify the early-type galaxies (ETGs) in every field by modeling each of the sources within a 40″ radius of the targets with a Sèrsic profile. Using a simple passive evolution model, we derive the expected location of the ETGs on the red sequence (RS) in the color-magnitude diagram for each of the fields of our sources. For seven targets, the model coincides with the position of the ETGs. A second approach involves a search for over densities. We compare the object densities of the sample as a whole and individually against control fields taken from the GOODS-S region of 3D-HST survey. With this method we determine the fields of ten targets to be cluster candidates. Four cluster candidates are found by both methods. The two methods disagree in some cases, depending on the specific properties of each field. For the most distant RG in the 3CR catalog (3C 257 at z = 2.47), we identify a population of bluer ETGs that lie on the expected location of the RS model for that redshift. This appears to be the general behavior of ETGs in our fields and it is possibly a signature of the evolution of such galaxies. Our results are consistent with half of the z > 1 RGs being located in dense, rapidly evolving environments.
I review the radio to X‐ray properties of gigahertz peaked‐spectrum (GPS) and compact steep‐spectrum (CSS) sources, the current hypotheses for their origin, and their use to constrain the evolution ...of powerful radio galaxies. The GPS and CSS sources are compact, powerful radio sources with well‐defined peaks in their radio spectra (near 1 GHz in the GPS and near 100 MHz in the CSS). The GPS sources are entirely contained within the extent of the narrow‐line region (≲1 kpc), while the CSS sources are contained entirely within the host galaxy (≲15 kpc). The peaks in the spectra are probably due to synchrotron self‐absorption, though free‐free absorption through an inhomogeneous screen may also play a role. The turnover frequency varies with linear sizelas
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, suggesting a simple physical relationship between these parameters. The radio morphologies are strikingly like those of the large‐scale classical doubles, though some sources can have very distorted morphologies suggestive of interactions. Radio polarization tends to be low, and in some cases the Faraday rotation measures can be extremely large. The IR properties are consistent with stellar populations and active galactic nucleus (AGN) bolometric luminosity similar to that of the 3CR classical doubles. The optical host galaxy properties (absolute magnitude, Hubble diagram, evidence for interaction) are consistent with those of the 3CR classical doubles. CSS sources at all redshifts exhibit high surface brightness optical light (most likely emission‐line gas) that is aligned with the radio axis. The optical emission‐line properties suggest (1) interaction of the radio source with the emission‐line gas and (2) the presence of dust toward the emission‐line regions. X‐ray observations of high‐redshift GPS quasars and a couple of GPS galaxies suggest the presence of significant columns of gas toward the nuclei. Searches for cold gas in the host galaxies have revealed large amounts of molecular gas and smaller amounts of atomic gas in several sources, though probably not enough to confine the radio sources. The main competing models for the GPS and CSS sources are that (1) they are frustrated by interaction with dense gas in their environments and (2) they are young and evolving radio sources that will become large‐scale sources. Combining the bright GPS and CSS samples with the 3CR results in a sample spanning a range in source size of 105that can be used to study source evolution. The number density versus linear size relation is consistent with a picture in which the sources expand with constant velocity and the radio power drops with linear sizelaccording to
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. This strong evolution suggests that at least some of the GPS and CSS sources evolve to become lower luminosity FR 1 radio sources. The GPS and CSS sources are important probes of their host galaxies and will provide critical clues to the origin and evolution of powerful radio sources.
We present new Spitzer IRS spectroscopy of Cygnus A, one of the most luminous radio sources in the local universe. Data on the inner 20" are combined with new reductions of MIPS and IRAC photometry ...as well as data from the literature to form a radio through mid-infrared spectral energy distribution (SED). This SED is then modeled as a combination of torus reprocessed active galactic nucleus (AGN) radiation, dust enshrouded starburst, and a synchrotron jet. This combination of physically motivated components successfully reproduces the observed emission over almost 5 dex in frequency. The bolometric AGN luminosity is found to be 10 super(12) L sub(middot in circle) (90% of L sub(IR)), with a clumpy AGN-heated dust medium extending to ~130 pc from the supermassive black hole. Evidence is seen for a break or cutoff in the core synchrotron emission. The associated population of relativistic electrons could in principle be responsible for some of the observed X-ray emission though the synchrotron self-Compton mechanism. The SED requires a cool dust component, consistent with dust-reprocessed radiation from ongoing star formation. Star formation contributes at least 6 x 10 super(10) L sub(middot in circle) to the bolometric output of Cygnus A, corresponding to a star formation rate of ~10 M sub(middot in circle) yr super(-1).
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