- ID:
- ivo://CDS.VizieR/J/ApJ/427/125
- Title:
- QSOs orientation modeling
- Short Name:
- J/ApJ/427/125
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We discuss the statistics of projection on the sky of a simple model for radio sources. The model has a core and two hot spots at unequal distance with an overall structure which is bent at the core. We examine the distributions or the observed sizes and bend angles in 114 quasars and 78 radio galaxies with z<2, from our own data. We find that the observations are well matched by this model with (a) a size distribution matching the observed one, (b) core-hotspot length differences between 0 and 45kpc, and (c) bend angles distributed between 0deg and ~25deg, where quasars are seen within 50deg of the source axis, and radio galaxies are seen at greater angles. We discuss the implications of these fits to unified models and source evolution.
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Search Results
- ID:
- ivo://CDS.VizieR/J/MNRAS/416/2437
- Title:
- Quantified H I morphology of WHISP sample
- Short Name:
- J/MNRAS/416/2437
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The morphology of the atomic hydrogen (HI) disc of a spiral galaxy is the first component to be disturbed by a gravitational interaction such as a merger between two galaxies. We use a simple parametrization of the morphology of HI column density maps of the Westerbork observations of neutral Hydrogen in Irregular and SPiral galaxies (WHISP) project to select those galaxies that are likely undergoing a significant interaction. Merging galaxies occupy a particular part of parameter space defined by Asymmetry (A), the relative contribution of the 20 per cent brightest pixels to the second-order moment of the column density map (M20) and the distribution of the second-order moment over all the pixels (GM). Based on their HI morphology, we find that 13 per cent of the WHISP galaxies are in an interaction (Concentration-M20) and only 7 per cent are based on close companions in the data cube. This apparent discrepancy can be attributed to the difference in visibility time-scales: mergers are identifiable as close pairs for 0.5 Gyr but are identifiable for ~1Gyr by their disturbed HI morphology. Expressed as volume merger rates, the two estimates agree very well: 7 and 6.8x10^-3^mergers/Gyr/Mpc^3^ for paired and morphologically disturbed HI discs, respectively.
- ID:
- ivo://CDS.VizieR/J/MNRAS/427/3159
- Title:
- Quantified HI morphology. VI. NUV/FUV
- Short Name:
- J/MNRAS/427/3159
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Extended ultraviolet (XUV) discs have been found in a substantial fraction of late-type - S0, spiral and irregular - galaxies. Similarly, most late-type spirals have an extended gas disc, observable in the 21-cm radio line (HI). The morphology of galaxies can be quantified well using a series of scale-invariant parameters; concentration-asymmetry-smoothness (CAS), Gini, M_20_, and G_M_ parameters. In this series of papers, we apply these to HI column density maps to identify mergers and interactions, lopsidedness and now XUV discs. In this paper, we compare the quantified morphology and effective radius (R_50_) of the Westerbork observations of neutral Hydrogen in Irregular and SPiral galaxies Project (WHISP) HI maps to those of far- and near-ultraviolet images obtained with GALEX, to explore how close the morphology and scales of HI and UV in these discs correlate. We find that XUV discs do not stand out by their effective radii in UV or HI. However, the concentration index in far-ultraviolet (FUV) appears to select some XUV discs. And known XUV discs can be identified via a criterion using asymmetry and M_20_; 80 per cent of XUV discs are included but with 55 per cent contamination. This translates into 61 candidate XUV disc out of our 266 galaxies, 23 per cent consistent with previous findings. Otherwise, the UV and HI morphology parameters do not appear closely related.
- ID:
- ivo://CDS.VizieR/J/A+A/319/757
- Title:
- Quasar and radio galaxies flux densities
- Short Name:
- J/A+A/319/757
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The tables described below contain the data used in the analysis. The data have been taken from various sources in the literature. The references to the data can be found in the paper. Table 1 contains the data of the 3C radio galaxy sample. Table 2 contains the data of the 3C quasar sample. Table 3 contains the data of the 4C quasar sample. The tables list the name of the object, its redshift, the value of the Q-parameter (ratio between the core and extended flux at 5 GHz observed frequency), and the flux densities at various frequencies.
- ID:
- ivo://CDS.VizieR/J/AJ/137/3884
- Title:
- Quasar candidates selected from the SDSS
- Short Name:
- J/AJ/137/3884
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We explore the multidimensional, multiwavelength selection of quasars from mid-infrared (MIR) plus optical data, specifically from Spitzer-Infrared Array Camera (IRAC) and the Sloan Digital Sky Survey (SDSS). Traditionally, quasar selection relies on cuts in two-dimensional color space despite the fact that most modern surveys (optical and IR) are done in more than three bandpasses. In this paper, we apply modern statistical techniques to combined Spitzer MIR and SDSS optical data, allowing up to eight-dimensional (8-D) color selection of quasars. Using a Bayesian selection method, we catalog 5546 quasar candidates to an 8.0{mu}m depth of 56{mu}Jy over an area of ~24{deg}^2^. Roughly 70% of these candidates are not identified by applying the same Bayesian algorithm to 4-color SDSS optical data alone. The 8-D optical+MIR selection on this data set recovers 97.7% of known type 1 quasars in this area and greatly improves the effectiveness of identifying 3.5<z<5 quasars which are challenging to identify (without considerable contamination) using MIR data alone.
- ID:
- ivo://CDS.VizieR/J/AZh/78/675
- Title:
- Quasar-galaxy associations
- Short Name:
- J/AZh/78/675
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A new catalog of 8382 close quasar-galaxy pairs is presented. The catalog was composed using published catalogued quasars and active galactic nuclei containing 11358 objects, as well as the LEDA catalog of galaxies, which contains on the order of 100000 objects.
- ID:
- ivo://CDS.VizieR/J/AJ/123/578
- Title:
- Quasars in the Coma cluster
- Short Name:
- J/AJ/123/578
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This is the second paper of the series about our Multiwavelength Quasar Survey. We present the observational results for the X-ray candidates in the field of the Coma Cluster. Nine new X-ray active galactic nuclei are discovered.
- ID:
- ivo://CDS.VizieR/J/ApJ/801/45
- Title:
- Quasars properties and reverberation mapping
- Short Name:
- J/ApJ/801/45
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We explore the practical feasibility of active galactic nucleus (AGN) broadband reverberation mapping and present first results. We lay out and apply a rigorous approach for the stochastic reverberation mapping of unevenly sampled multi-broadband flux measurements, assuming that the broad-line region (BLR) line flux is contributing up to 15% in some bands, and is directly constrained by one spectroscopical epoch. The approach describes variations of the observed flux as the continuum, modeled as a stochastic Gaussian process, and emission line contribution, modeled as a scaled, smoothed, and delayed version of the continuum. This approach can be used not only to interpolate in time between measurements, but also to determine confidence limits on continuum-line emission delays. This approach is applied to Sloan Digital Sky Survey observations in Stripe 82 (S82), providing flux measurements that are precise to 2% at ~60 epochs over ~10 yr. The strong annual variations in the epoch sampling prove a serious limitation in practice. In addition, suitable redshift ranges must be identified where strong, broad emission lines contribute to one filter, but not to another. By generating and evaluating problem-specific mock data, we verify that S82-like data can constrain {tau}_delay_ for a simple transfer function model. In application to real data, we estimate {tau}_delay_ for 323 AGNs with 0.225<z<0.846, combining information for different objects through the ensemble-scaling relationships for BLR size and black hole mass. Our analysis tentatively indicates a 1.7 times larger BLR size of H{alpha} and Mg II compared to Kaspi et al. (2000ApJ...533..631K; 2007ApJ...659..997K) and Vestergaard (2002ApJ...571..733V; 2006ApJ...641..689V), but the seasonal data sampling casts doubt on the robustness of the inference.
- ID:
- ivo://CDS.VizieR/J/ApJ/703/1569
- Title:
- Radial distribution in SINGS galaxies. I.
- Short Name:
- J/ApJ/703/1569
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present ultraviolet through far-infrared (FIR) surface brightness profiles for the 75 galaxies in the Spitzer Infrared Nearby Galaxies Survey (SINGS). The imagery used to measure the profiles includes Galaxy Evolution Explorer UV data, optical images from Kitt Peak National Observatory, Cerro Tololo Inter-American Observatory, and Sloan Digital Sky Survey, near-IR data from Two Micron All Sky Survey, and mid- and FIR images from Spitzer. Along with the radial profiles, we also provide multi-wavelength asymptotic magnitudes and several nonparametric indicators of galaxy morphology: the concentration index (C42), the asymmetry (A), the Gini coefficient (G), and the normalized second-order moment of the brightest 20% of the galaxy's flux ({overline}M_20_). In this paper, the first of a series, we describe the technical aspects regarding the surface photometry, and present a basic analysis of the global and structural properties of the SINGS galaxies at different wavelengths.
- ID:
- ivo://CDS.VizieR/J/ApJ/701/1965
- Title:
- Radial dust properties of SINGS galaxies
- Short Name:
- J/ApJ/701/1965
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a detailed analysis of the radial distribution of dust properties in the SINGS sample, performed on a set of ultraviolet (UV), infrared (IR), and HI surface brightness profiles, combined with published molecular gas profiles and metallicity gradients. By applying physical dust models to our radial spectral energy distributions, we have derived radial profiles of the total dust mass surface density, the fraction of the total dust mass contributed by polycyclic aromatic hydrocarbons (PAHs), and the intensity of the radiation field heating the grains.
