- ID:
- ivo://CDS.VizieR/J/MNRAS/344/283
- Title:
- 100-Mpc-scale structures of radio galaxies
- Short Name:
- J/MNRAS/344/283
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present unequivocal evidence for a huge (~80x100x100Mp^3^) superstructure at redshift z=0.27 in the three-dimensional distribution of radio galaxies from the Texas-Oxford NVSS Structure 08h region (TONS08) sample, confirming tentative evidence for such a structure from the 7C redshift survey (7CRS). A second, newly discovered superstructure is also found less securely at redshift 0.35 (of dimensions ~100x100x100Mpc^3^). We present full observational details on the TONS08 sample which was constructed to probe structures in the redshift range 0<z<0.5 by matching NVSS sources with objects in APM catalogues to obtain a sample of optically bright (E~R<=19.83), radio-faint (1.4GHz flux density S_1.4_>=3mJy) radio galaxies in the same 25deg^2^ area as part II of the 7CRS.
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Search Results
- ID:
- ivo://CDS.VizieR/J/ApJS/38/351
- Title:
- M31 planetary nebulae
- Short Name:
- J/ApJS/38/351
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Finding charts and equatorial coordinates are presented for 311 planetary nebulae and for nearby reference stars in the Andromeda galaxy (M31). The standard deviation of the coordinates relative to the AGK3 is smaller than 1.0". The standard deviation of the coordinates relative to the reference stars is smaller than 0.5".
- ID:
- ivo://CDS.VizieR/J/ApJ/775/92
- Title:
- MQS III: AGNs behind LMC and SMC
- Short Name:
- J/ApJ/775/92
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Magellanic Quasars Survey (MQS) has now increased the number of quasars known behind the Magellanic Clouds by almost an order of magnitude. All survey fields in the Large Magellanic Cloud (LMC) and 70% of those in the Small Magellanic Cloud (SMC) have been observed. The targets were selected from the third phase of the Optical Gravitational Lensing Experiment (OGLE-III) based on their optical variability, mid-IR, and/or X-ray properties. We spectroscopically confirmed 758 quasars (565 in the LMC and 193 in the SMC) behind the clouds, of which 94% (527 in the LMC and 186 in the SMC) are newly identified. The MQS quasars have long-term (12yr and growing for OGLE), high-cadence light curves, enabling unprecedented variability studies of quasars. The MQS quasars also provide a dense reference grid for measuring both the internal and bulk proper motions of the clouds, and 50 quasars are bright enough (I<~18mag) for absorption studies of the interstellar/intergalactic medium of the clouds.
504. Mrk421 in March 2010
- ID:
- ivo://CDS.VizieR/J/A+A/578/A22
- Title:
- Mrk421 in March 2010
- Short Name:
- J/A+A/578/A22
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A flare from the TeV blazar Mrk 421, occurring in March 2010, was observed for 13 consecutive days from radio to very high energy (VHE; E>100GeV) gamma-rays with MAGIC, VERITAS, Whipple, FermiLAT, MAXI, RXTE, Swift, GASP-WEBT, and several optical and radio telescopes. We model the day-scale SEDs with one-zone and two-zone synchrotron self-Compton (SSC) models, investigate the physical parameters, and evaluate whether the observed broadband SED variability can be associated to variations in the relativistic particle population. Flux variability was remarkable in the X-ray and VHE bands while it was minor or not significant in the other bands. The one-zone SSC model can describe reasonably well the SED of each day for the 13 consecutive days. This flaring activity is also very well described by a two-zone SSC model, where one zone is responsible for the quiescent emission while the other smaller zone, which is spatially separated from the first one, contributes to the daily-variable emission occurring in X-rays and VHE gamma-rays. Both the one-zone SSC and the two-zone SSC models can describe the daily SEDs via the variation of only four or five model parameters, under the hypothesis that the variability is associated mostly to the underlying particle population. This shows that the particle acceleration and cooling mechanism producing the radiating particles could be the main one responsible for the broadband SED variations during the flaring episodes in blazars. The two-zone SSC model provides a better agreement to the observed SED at the narrow peaks of the low- and high-energy bumps during the highest activity, although the reported one-zone SSC model could be further improved by the variation of the parameters related to the emitting region itself ({delta}, B and R), in addition to the parameters related to the particle population.
- ID:
- ivo://CDS.VizieR/J/A+A/655/A89
- Title:
- Mrk421 multi-instrument observations in 2017
- Short Name:
- J/A+A/655/A89
- Date:
- 21 Mar 2022 08:46:33
- Publisher:
- CDS
- Description:
- We present a detailed characterisation and theoretical interpretation of the broadband emission of the paradigmatic TeV blazar Mrk 421, with a special focus on the multi-band flux correlations. The dataset has been collected through an extensive multi-wavelength campaign organised between 2016 December and 2017 June. The instruments involved are MAGIC, FACT, Fermi-LAT, Swift, GASP-WEBT, OVRO, Medicina, and Metsahovi. Additionally, four deep exposures (several hours long) with simultaneous MAGIC and NuSTAR observations allowed a precise measurement of the falling segments of the two spectral components. The very-high-energy (VHE; E>100GeV) gamma rays and X-rays are positively correlated at zero time lag, but the strength and characteristics of the correlation change substantially across the various energy bands probed. The VHE versus X-ray fluxes follow different patterns, partly due to substantial changes in the Compton dominance for a few days without a simultaneous increase in the X-ray flux (i.e. orphan gamma-ray activity). Studying the broadband spectral energy distribution (SED) during the days including NuSTAR observations, we show that these changes can be explained within a one-zone leptonic model with a blob that increases its size over time. The peak frequency of the synchrotron bump varies by two orders of magnitude throughout the campaign. Our multi-band correlation study also hints at an anti-correlation between UV-optical and X-ray at a significance higher than 3{sigma}. A VHE flare observed on MJD~57788 (2017 February 4) shows gamma-ray variability on multi-hour timescales, with a factor ten increase in the TeV flux but only a moderate increase in the keV flux. The related broadband SED is better described by a two-zone leptonic scenario rather than by a one-zone scenario. We find that the flare can be produced by the appearance of a compact second blob populated by high energetic electrons spanning a narrow range of Lorentz factors, from {gamma}'_min_=2x10^4^ to {gamma}'_max_=6x10^5^.
506. Mrk 926 spectra
- ID:
- ivo://CDS.VizieR/J/A+A/657/A122
- Title:
- Mrk 926 spectra
- Short Name:
- J/A+A/657/A122
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- Mrk926 is known to be a highly-variable AGN. Furthermore, it is known to show very broad-line profiles. We intended to study the continuum and line profile variations of this object with high temporal resolution in order to determine its broad-line region (BLR) structure, and to derive its black hole (BH) mass. We carried out a high-cadence spectroscopic variability campaign of Mrk926 with the 10m HET telescope, aided by photometric V-band data taken with the C18 telescope at the Wise Observatory, over a period of about five months. We extracted spectroscopic continuum and line light curves, and computed cross-correlation functions (CCFs) as well as velocity-resolved CCFs with respect to the combined spectroscopic and photometric V-band light curve. The continuum luminosity of Mrk926 showed a drastic decrease during our campaign. The luminosity dropped to less than 50% of its original luminosity within 2.5 months only. Furthermore, the spectra of Mrk926 show complex and very broad Balmer line profiles including outer Balmer satellites ranging from +/-5000 to +/-13000km/s. The integrated H{alpha}, H{beta} and HeI_5876_ line light curves are delayed relative to the continuum light curve. The Ha and Hb lines show two velocity-delay structures in the central part of their line profile (within +/-5000km/s) at ~10 and ~57 light-days, and at ~5 and ~48 light-days, respectively. These structures might be interpreted as the upper and lower half of an ellipse in the velocity-delay plane, that might be the signature of a line-emitting ring, inclined by ~50{deg} to the line of sight, orbiting the black hole at radii R of 33.5 and 26.5 light-days. We determined continuum luminosities log({lambda}*L_({lambda})_/erg/s) of 43.68 to 44.13 which are in good agreement with the established R_(BLR)-L_(AGN) relation. Adopting delays of 33.5 and 26.5 days for Ha and Hb, respectively, we derive a black hole mass of 1.1+/-0.2*10^8^M_{sun}_ which indicates a low Eddington ratio decreasing from 8 to 3 percent during our campaign. The Balmer satellite components show a higher correlation coefficient with respect to the continuum than the central line profile, and their response to the continuum variations is of the order of only 3-5 days. We attribute this to the central line segment and the Balmer satellites having different, spatially distinct regions of origin.
- ID:
- ivo://CDS.VizieR/J/ApJ/758/129
- Title:
- 4Ms Chandra Deep Field South 6-8keV galaxies
- Short Name:
- J/ApJ/758/129
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using the 4Ms Chandra Deep Field-South (CDF-S) survey, we have identified a sample of 6845 X-ray-undetected galaxies that dominates the unresolved {approx}20%-25% of the 6-8keV cosmic X-ray background (XRB). This sample was constructed by applying mass and color cuts to sources from a parent catalog based on GOODS-South Hubble Space Telescope z-band imaging of the central 6' radius area of the 4Ms CDF-S. The stacked 6-8keV detection is significant at the 3.9{sigma} level, but the stacked emission was not detected in the 4-6keV band, which indicates the existence of an underlying population of highly obscured active galactic nuclei (AGNs). Further examinations of these 6845 galaxies indicate that the galaxies on the top of the blue cloud and with redshifts of 1<~z<~3, magnitudes of 25<~z_850_<~28, and stellar masses of 2x10^8^<~M_{sstarf}_/M_{sun}_<~2x10^9^ make the majority contributions to the unresolved 6-8keV XRB. Such a population is seemingly surprising given that the majority of the X-ray-detected AGNs reside in massive (>~10^10^M_{sun}_) galaxies. We discuss constraints upon this underlying AGN population, supporting evidence for relatively low mass galaxies hosting highly obscured AGNs, and prospects for further boosting the stacked signal.
- ID:
- ivo://CDS.VizieR/J/ApJ/831/145
- Title:
- 6Ms Chandra long-term analyses of AGNs
- Short Name:
- J/ApJ/831/145
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We perform long-term (~15 years, observed-frame) X-ray variability analyses of the 68 brightest radio-quiet active galactic nuclei (AGNs) in the 6Ms Chandra Deep Field-South survey; the majority are in the redshift range of 0.6-3.1, providing access to penetrating rest-frame X-rays up to ~10-30keV. Of the 68 sources, 24 are optical spectral type I AGNs, and the rest (44) are type II AGNs. The timescales probed in this work are among the longest for X-ray variability studies of distant AGNs. Photometric analyses reveal widespread photon flux variability: 90% of AGNs are variable above a 95% confidence level, including many X-ray obscured AGNs and several optically classified type II quasars. We characterize the intrinsic X-ray luminosity (L_X_) and absorption (N_H_) variability via spectral fitting. Most (74%) sources show L_X_ variability; the variability amplitudes are generally smaller for quasars. A Compton-thick candidate AGN shows variability of its high-energy X-ray flux, indicating the size of reflecting material to be <~0.3pc. L_X_ variability is also detected in a broad absorption line quasar. The N_H_ variability amplitude for our sample appears to rise as time separation increases. About 16% of sources show N_H_ variability. One source transitions from an X-ray unobscured to obscured state, while its optical classification remains type I; this behavior indicates the X-ray eclipsing material is not large enough to obscure the whole broad-line region.
- ID:
- ivo://CDS.VizieR/J/A+A/484/119
- Title:
- Multi-epoch VLBI survey of CJF sources
- Short Name:
- J/A+A/484/119
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This is the second in a series of papers presenting VLBI observations of the 293 Caltech-Jodrell Bank Flat-spectrum (hereafter CJF) sources and their analysis. We obtain a consistent motion dataset large enough to allow the systematic properties of the population to be studied. We present detailed kinematic analysis of the complete flux-density limited CJF survey. We computed 2-D kinematic models based on the optimal model-fitting parameters of multi-epoch VLBA observations. This allows us to calculate not only radial, but also orthogonal motions, and thus to study curvature and acceleration. Statistical tests of the motions measured and their reliability were performed. A correlation analysis between the derived apparent motions, luminosities, spectral indices, and core dominance and the resulting consequences is described. With at least one velocity in each of the 237 sources, this sample is much larger than any available before, so it allows a meaning ful statistical investigation of apparent motions and any possible correlations with other parameters in AGN jets. The main results to emerge are as follows: * In general motions are not consistent with a single uniform velocity applicable to all components along a jet. * We find a slight trend towards a positive outward acceleration and also adduce some evidence for greater acceleration in the innermost regions. * We find a lack of fast components at physical distances less than a few pc from the reference feature. * Only ~4% of the components from galaxies and <2% of those from quasars undergo large bends i.e. within 15{deg} of +/-90{deg}. * The distribution of radial velocities shows a broad distribution of velocities (apparent velocities up to 30c). Fifteen percent of the best-sampled jet components exhibit low velocities that may need to be explained in a different manner to the fast motions. * Some negative superluminal motions are seen, and in 15 cases (6%) these are definitely significant. * We find a strong correlation between the 5 GHz luminosity and the apparent velocity. * The CJF galaxies, on average, show slower apparent jet-component velocities than the quasars. * The mean velocity in the VLBA 2cm survey (Kellermann et al. 2004) is substantially higher than in the CJF survey, the ratio could be roughly a factor of 1.5-2. This supports the observed trend toward increasing apparent velocity with in creasing observing frequency. This AGN survey provides the basis for any statistical analysis of jet and jet-component properties.
- ID:
- ivo://CDS.VizieR/J/ApJ/851/33
- Title:
- Multi-wavelength analysis of CGRaBS blazars
- Short Name:
- J/ApJ/851/33
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of a multi-frequency, time-averaged analysis of blazars included in the Candidate Gamma-ray Blazar Survey catalog. Our sample consists of 324 {gamma}-ray detected ({gamma}-ray loud) and 191 {gamma}-ray undetected ({gamma}-ray quiet) blazars; we consider all the data up to 2016 April 1. We find that both the {gamma}-ray loud and {gamma}-ray quiet blazar populations occupy similar regions in the WISE color-color diagram, and {gamma}-ray loud sources are brighter in the radio and X-ray bands. A simple one-zone synchrotron inverse-Compton emission model is applied to derive the physical properties of both populations. We find that the central black hole mass and accretion disk luminosity (L_disk_) computed from the modeling of the optical-UV emission with a Shakura-Sunyaev disk reasonably matches that estimated from the optical spectroscopic emission-line information. A significantly larger Doppler boosting in the {gamma}-ray loud blazars is noted, and their jets are more radiatively efficient. On the other hand, the {gamma}-ray quiet objects are more MeV-peaked and thus could be potential targets for next-generation MeV missions. Our results confirm earlier findings about the accretion-jet connection in blazars; however, many of the {gamma}-ray quiet blazars tend to deviate from the recent claim that the jet power exceeds L_disk_ in blazars. A broadband study, considering a larger set of {gamma}-ray quiet objects and also including BL Lacs, will be needed to confirm/reject this hypothesis as well as to verify the evolution of the powerful high-redshift blazars into their low-power nearby counterparts.
