Veron Catalog Research Articles

J-PLUS: Support vector machine applied to STAR-GALAXY-QSO classification

Context.In modern astronomy, machine learning has proved to be efficient and effective in mining big data from the newest telescopes.Aims.In this study, we construct a supervised machine-learning algorithm to classify the objects in the Javalambre Photometric Local Universe Survey first data release (J-PLUS DR1).Methods.The sample set is featured with 12-waveband photometry and labeled with spectrum-based catalogs, including Sloan Digital Sky Survey spectroscopic data, the Large Sky Area Multi-Object Fiber Spectroscopic Telescope, and VERONCAT – the Veron Catalog of Quasars & AGN. The performance of the classifier is presented with the applications of blind test validations based on RAdial Velocity Extension, theKeplerInput Catalog, the Two Micron All Sky Survey Redshift Survey, and the UV-bright Quasar Survey. A new algorithm was applied to constrain the potential extrapolation that could decrease the performance of the machine-learning classifier.Results.The accuracies of the classifier are 96.5% in the blind test and 97.0% in training cross-validation. TheF1-scores for each class are presented to show the balance between the precision and the recall of the classifier. We also discuss different methods to constrain the potential extrapolation.

Study of radio properties of active galaxies

In this paper we investigate radio properties of active galaxies taken from Veron-Cetty & Veron (2010) catalogue. The galaxies are limited to magnitudes in the range of 12m-19m. We have cross-correlated the list with radio catalogues and selected those galaxies, which have data on 5 radio fluxes at different wavelengths. For all the objects we have built radio spectra and estimate radio spectral indices. As a result, we have αaverage±0.5036±0.0717.

Classification by Activity Type of a Sample of Active Galaxies with Radio Emission

This is a detailed spectral classification of 96 active galaxies from the Veron-Cetty and Veron catalog (2010, Version 13, VCV-13) of active galaxies and quasars. These objects were identified as radio sources using standard radio catalogs. Those galaxies which had radio sources in at least 6 different radio bands and had been identified spectrally in the SDSS catalog were selected. The types of activity of these were determined using their SDSS spectra. Three diagnostic diagrams and a direct study of the spectra were used for more certain classification. As a result, the classifications of 85% of the objects were changed. The radio sources in different radio bands make it possible to construct the spectral distribution of the energy in the radio range and to compare it with the optical activity types.

Morphology of Seyfert Galaxies

We probed the relation between properties of Seyfert nuclei and morphology of their host galaxies. We selected Seyfert galaxies from the Sloan Digital Sky Survey with redshifts less than 0.2 identified by the Ve ron Catalog (13th). We used the FracDev parameter from SDSS galaxy fitting models to represent the bulge fractions of the Seyfert host galaxies. We found that the host galaxies of Seyfert 1 and Seyfert 2 are dominated by large bulge fractions, and Seyfert 2 galaxies are more likely to be located in disk galaxies whereas most of the Seyfert 1 galaxies are located in bulge-dominant galaxies. These results indicate that the types of AGNs are related to their host galaxies and cannot be explained by the traditional unification model of Seyfert galaxies.

X-ray variability of Seyfert 1.8/1.9 galaxies

Seyfert 1.8/1.9 are sources showing weak broad H-alpha components in their optical spectra. We aim at testing whether Seyfert 1.8/1.9 have similar properties at UV and X-ray wavelengths to Seyfert 2. We use the 15 Seyfert 1.8/1.9 in the Veron Cetty and Veron catalogue with public data available from the Chandra and/or XMM-Newton archives at different dates, with timescales between observations ranging from days to years. Our results are homogeneously compared with a previous work using the same methodology applied to a sample of Seyfert 2 (Hernandez-Garcia et al. 2015). X-ray variability is found in all 15 nuclei over the aforementioned ranges of timescales. The main variability pattern is related to intrinsic changes in the sources, which are observed in ten nuclei. Changes in the column density are also frequent, as they are observed in six nuclei, and variations at soft energies, possibly related to scattered nuclear emission, are detected in six sources. X-ray intraday variations are detected in six out of the eight studied sources. Variations at UV frequencies are detected in seven out of nine sources. A comparison between the samples of Seyfert 1.8/1.9 and 2 shows that, even if the main variability pattern is due to intrinsic changes of the sources in the two families, these nuclei exhibit different variability properties in the UV and X-ray domains. In particular, variations in the broad X-ray band on short time-scales (days/weeks), and variations in the soft X-rays and UV on long time-scales (months/years) are detected in Seyfert 1.8/1.9 but not in Seyfert 2. Overall, we suggest that optically classified Seyfert 1.8/1.9 should be kept separated from Seyfert 2 galaxies in UV/X-ray studies of the obscured AGN population because their intrinsic properties might be different.

A Bayesian analysis of the 69 highest energy cosmic rays detected by the Pierre Auger Observatory

The origins of ultra-high energy cosmic rays (UHECRs) remain an open question. Several attempts have been made to cross-correlate the arrival directions of the UHECRs with catalogs of potential sources, but no definite conclusion has been reached. We report a Bayesian analysis of the 69 events from the Pierre Auger Observatory (PAO), that aims to determine the fraction of the UHECRs that originate from known AGNs in the Veron-Cety & Veron (VCV) catalog, as well as AGNs detected with the Swift Burst Alert Telescope (Swift-BAT), galaxies from the 2MASS Redshift Survey (2MRS), and an additional volume-limited sample of 17 nearby AGNs. The study makes use of a multi-level Bayesian model of UHECR injection, propagation and detection. We find that for reasonable ranges of prior parameters, the Bayes factors disfavour a purely isotropic model. For fiducial values of the model parameters, we report 68% credible intervals for the fraction of source originating UHECRs of 0.09+0.05-0.04, 0.25+0.09-0.08, 0.24+0.12-0.10, and 0.08+0.04-0.03 for the VCV, Swift-BAT and 2MRS catalogs, and the sample of 17 AGNs, respectively.

X-ray spectral variability of Seyfert 2 galaxies

Variability across the electromagnetic spectrum is a property of AGN that can help constraining the physical properties of these galaxies. This is the third of a serie of papers with the aim of studying the X-ray variability of different families of AGN. The main purpose of this work is to investigate the variability pattern in a sample of optically selected type 2 Seyfert galaxies. We use the 26 Seyferts in the Veron-Cetty and Veron catalogue with data available from Chandra and/or XMM-Newton public archives at different epochs, with timescales ranging from a few hours to years. All the spectra of the same source are simultaneously fitted and we let different parameters to vary in the model. Whenever possible, short-term variations and/or long-term UV flux variations are studied. We divide the sample in Compton-thick, Compton-thin, and changing-look candidates. Short-term variability at X-rays is not found. From the 25 analyzed sources, 11 show long-term variations; eight (out of 11) are Compton-thin, one (out of 12) is Compton-thick, and the two changing-look candidates are also variable. The main driver for the X-ray changes is related to the nuclear power (nine cases), while variations at soft energies or related with absorbers at hard X-rays are less common, and in many cases these variations are accompained with variations of the nuclear continuum. At UV frequencies nuclear variations are nor found. We report for the first time two changing-look candidates, MARK273 and NGC7319. A constant reflection component located far away from the nucleus plus a variable nuclear continuum are able to explain most of our results; the Compton-thick candidates are dominated by reflection, which supresses their continuum making them seem fainter, and not showing variations, while the Compton-thin and changing-look candidates show variations.

CORRELATIONS OF THE ARRIVAL DIRECTIONS OF ULTRA-HIGH ENERGY COSMIC RAYS WITH EXTRAGALACTIC OBJECTS AS OBSERVED BY THE TELESCOPE ARRAY EXPERIMENT

We search for correlations between positions of extragalactic objects and arrival directions of Ultra-High Energy Cosmic Rays (UHECRs) with primary energy $E \ge 40$ EeV as observed by the surface detector array of the Telescope Array (TA) experiment during the first 40 months of operation. We examined several public astronomical object catalogs, including the Veron-Cetty and Veron catalog of active galactic nuclei. We counted the number of TA events correlated with objects in each catalog as a function of three parameters: the maximum angular separation between a TA event and an object, the minimum energy of the events, and the maximum redshift of the objects. We determine combinations of these parameters which maximize the correlations, and calculate the chance probabilities of having the same levels of correlations from an isotropic distribution of UHECR arrival directions. No statistically significant correlations are found when penalties for scanning over the above parameters and for searching in several catalogs are taken into account.

Radio Properties of AGN

AbstractTo study the radio properties of AGN, we cross-correlate and investigate Veron-Cetty & Veron catalog of QSOs and Active Galaxies (v.13, 2010) with a number of radio catalogs: NVSS, FIRST, GB6, 87GB, SUMSS, WISH, WENSS, and 7C. This catalog contains 168,940 objects with positional accuracy of mostly 1 arcsec, though many positions have larger errors. We use new cross-correlation software based on accuracy of each object independently. In this software we take into account errors for each source and take identifications with errors within 3 sigma. Altogether, we find ~16,000 AGN having radio detection in any of the listed catalogs. Using all data from radio catalogs, we derive a homogeneous sample of radio AGN. The sample allows accomplish several tasks, including study of the distribution of radio sources by activity types, differences in physical properties of radio-loud and radio-quiet AGN, luminosity functions for various types of radio AGN, study of the q parameter by AGN types and its evolution, etc.

Reclassification of the nearest quasar pair candidate: SDSS J15244+3032–RXS J15244+3032

We present optical spectroscopy of the nearest quasar pair listed in the 13th edition of the Veron-Cetty & Veron catalogue, i.e. the two quasars SDSS J15244+3032 and RXS J15244+3032 (redshift z~0.27, angular separation ~7 arcsec, and line-of-sight velocity difference ~1900 km/s). This system would be an optimal candidate to investigate the mutual interaction of the host galaxies with ground based optical imaging and spectroscopy. However, new optical data demonstrate that RXS J15244+3032 is indeed a star of spectral type G. This paper includes data gathered with the Asiago 1.82m telescope (Cima Ekar Observatory, Asiago, Italy).

Anisotropy studies with the Pierre Auger Observatory

Recent results from the Pierre Auger Observatory about anisotropies in the arrival directions of ultra-high energy cosmic rays are reported. In the EeV energy range, we present the results of a search for a large scale dipolar anisotropy pattern. In the same energy range, we show the results of a search for localized excesses of cosmic ray neutrons. For cosmic rays with energies above 20EeV, we discuss the results of the search for multiplets of aligned events. Finally, we present an update on the search for correlations between events with energy above 55EeV and the positions of active galactic nuclei from the Veron-Cetty and Veron catalog. The results of a study of the region around Centaurus A are also shown. In this article, we summarize recent results of the Pierre Auger Observatory on anisotropy searches. Anisotropies in the distribution of ultra-high energy cosmic rays (UHECR) are a key observable towards understanding their origin and identifying the transition region from galactic to extragalactic cosmic rays. In the energy range where galactic sources dominate the flux, models predict both a dipolar and a quadrupolar anisotropy, determined by the galactic magnetic fields and the source distribution of cosmic rays in the galaxy. If such an anisotropy can be detected, the transition to extragalactic cosmic rays should reveal itself by a change in the anisotropy pattern towards isotropy. Results on large-scale anisotropies are presented in section 2. Galactic neutrons in the EeV range live long enough to reach the Earth from the galactic center before decaying. If such neutrons are present they would point to their sources in the galactic disk. A search for neutron point sources is presented in section 3. At energies of tens of EeV, where cosmic rays are suspected to be of extragalactic origin, cosmic rays may be only weakly deflected by the extragalactic magnetic fields. This opens the possibility of identifying the extragalactic sources of UHECR from their arrival directions. In section 4 we present the 2011 update on the correlation of the highest energy events with the Veron-Cetty and Veron catalog of Active Galactic Nuclei (AGN). Centaurus A is a particularly promising candidate for being an UHECR source and is discussed separately. Finally, in section 5, we review an analysis searching for multiplets of particles from a common source, deflected in a coherent galactic or extragalactic magnetic field.

Unveiling the nucleus of NGC 7172

Aims. We present the results of near-infrared (NIR) H+K European Southern Observatory SINFONI integral field spectroscopy (IFS) of the Seyfert 2 galaxy NGC 7172. We investigate the central 800 pc, concentrating on excitation conditions, morphology, and stellar content. NGC 7172 was selected from a sample of the ten nearest Seyfert 2 galaxies from the Veron-Cetty & Veron catalogue. All objects were chosen as test cases for adaptive optics (AO) assisted observations that allow a detailed study (at high spatial and spectral resolution) of the nuclear and host environments. NGC 7172 has a prominent dustlane crossing the central galaxy region from east to west, which makes it an ideal candidate to investigate the effect of obscuration by strong galactic extinction on (active) galaxies and their classification. Methods. The NIR is less influenced by dust extinction than optical light and is sensitive to the mass-dominating stellar populations. SINFONI integral field spectroscopy combines NIR imaging and spectroscopy and provides us with the opportunity to analyze several emission and absorption lines to investigate the stellar populations and ionization mechanisms over the 4′′ × 4′′ field of view (FOV). Results. We present emission and absorption line measurements in the central 800 pc of NGC 7172. The detection of [Sivi] and broad Paα and Brγ components are clear signs of an accreting super-massive black hole hiding behind the prominent dustlane at visible wavelengths. Hot temperatures of about 1300 K are indicative of a dusty torus in the nuclear region. Narrow components of Paα and Brγ enable us to make an extinction measurement. Our measures of the molecular hydrogen lines, hydrogen recombination lines, and [Fe ii] indicate that the excitation of these lines is caused by an active galactic nucleus. The central region of the galactic disk is predominantly inhabited by gas, dust, and an old K-M type giant stellar population. The gaseous, molecular, and stellar velocity maps show a related disturbed disk structure and similar velocities. Conclusions. We find evidence of nuclear activity located behind the prominent dustlane crossing the central region of the galaxy. The nucleus of NGC 7172, which is optically classified as a Seyfert 2 nucleus without any trace of broad emission lines, is a Seyfert 1 nucleus either surrounded by a molecular dust torus or hidden behind the strong galactic extinction. Our observation provides support for the unified model scheme. However, an evolutionary scenario cannot be ruled out by our observation.

The second release of the Large Quasar Astrometric Catalog (LQAC-2)

Context. Since the first release of the LQAC (Large Quasar Astrometric Catalogue) a large number of quasars have been discovered through very dense observational surveys. As these objects constitute the cornerstones of modern astrometry by indicating quasi inertial directions, their spatial density and their astrometric quality must be studied in detail. Aims. Following the same procedure as in this first release of the LQAC, our aim is to compile all the quasars recorded until the present date, with the best determination of their equatorial coordinates in the ICRS, i.e. with respect to the newly established ICRF2 and with the maximum of information concerning their physical properties (redshift, photometry, absolute magnitudes). Methods. First of all we made a substantial review of the definitions and properties of quasars and AGN (active galactic nuclei), because the differenciation of these objects is unclear in the literature, even for specialists. Then we carried out the cross-identification between the nine catalogs of quasars chosen for their accuracy and their huge number of objects, including all the available data related to magnitudes, radiofluxes, and redshifts. Moreover, we computed the absolute magnitude of our extragalactic objects by taking the recent studies concerning the galactic absorption into account. In addition, substantial improvements were made with respect to the first release of the LQAC. First, an LQAC name is given for each object based on its equatorial coordinates with respect to the ICRS, following a procedure that creates no ambiguity in the identification. Second the equatorial coordinates of the objects were recomputed more accurately according to the algorithms used for the elaboration of the Large Quasar Reference Frame (LQRF). Third we introduce a morphological classification for the objects that in particular clearly defines if the object is point-like or extended.Results. Our final catalog, called LQAC-2, contains 187 504 quasars. This is roughly 65% more than the 113 666 quasars recorded in the first version of the LQAC and a little more than the number of quasars recorded in the updated version of the Veron-Cetty & Veron (2010, A&A, 518, A10) catalog, which was the densest compilation of quasars up to now. In addition to the quantitative and qualitative improvements brought by our compilation, we discuss the homogeneity of the data and carry out statistical analysis of the spatial density and the distance to the closest neighbor. Conclusions. The LQAC-2 will be useful for the astronomical community since it gives the most complete information available about the whole set of already recorded quasars, insisting on the precision and accuracy of their coordinates with respect to the ICRF-2.

A Bayesian analysis of the 27 highest energy cosmic rays detected by the Pierre Auger Observatory

It is possible that ultrahigh energy cosmic rays (UHECRs) are generated by active galactic nuclei (AGNs), but there is currently no conclusive evidence for this hypothesis. Several reports of correlations between the arrival directions of UHECRs and the positions of nearby AGNs have been made, the strongest detection coming from a sample of 27 UHECRs detected by the Pierre Auger Observatory (PAO). However, the PAO results were based on a statistical methodology that not only ignored some relevant information (most obviously the UHECR arrival energies, but also some of the information in the arrival directions), but also involved some problematic fine-tuning of the correlation parameters. Here we present a fully Bayesian analysis of the PAO data (collected before 2007 September), which makes use of more of the available information, and find that a fraction FAGN= 0.15+0.10−0.07 of the UHECRs originate from known AGNs in the Veron-Cetty and Veron (VCV) catalogue. The hypothesis that all the UHECRs come from VCV AGNs is ruled out, although there remains a small possibility that the PAO–AGN correlation is coincidental (FAGN= 0.15 is 200 times as probable as FAGN= 0.00).

On the arrival directions of the highest energy cosmic rays detected by the Pierre Auger Observatory

We report different analyses of the arrival directions of the highest energy cosmic rays detected by the Pierre Auger Observatory between 1 January 2004 and 31 December 2009. We update the measured fraction of arrival directions correlating with the positions of objects in the Veron-Cetty and Veron (VCV) catalog. We examine the arrival directions in relation to other populations of nearby extragalactic objects: galaxies in the 2 Microns All Sky Survey and active galactic nuclei in the Swift-BAT hard X-ray catalog. We also show the 2-point autocorrelation function and analyse the sky region with the largest excess compared to isotropic expectations.

Testing the correlations between ultrahigh energy cosmic rays and the Veron-Cetty and Veron catalogue of quasars and active galactic nuclei

We investigate several aspects of the correlations reported by the Pierre Auger Observatory between the highest energy ultra-high energy cosmic rays (UHECRs) and galaxies in the Veron-Cetty Veron (VCV) catalogue of active galactic nuclei (AGNs). First, we quantify the extent of the inhomogeneity and impurity of the VCV catalogue. Second, we determine how the correlation between the highest energy Auger UHECRs and VCV galaxies is modified when only AGNs satisfying optical spectral line ratios, i.e. a very pure sample, are used. Finally, we measure the correlation between the published Auger UHECRs and the distribution of nearby galaxies. We find that the correlation between the arrival directions of published Auger UHECRs and the VCV AGNs is much stronger than the correlation with the random sets of galaxies drawn from nearby large-scale structure. This suggests that the correlation of the UHECRs with AGNs is not solely due to AGNs tracing the large-scale distribution of matter. We also find that once we take into account the heavy oversampling of the VCV catalogue in the Virgo region, the lack of UHECRs from that region is not incompatible with UHECRs having AGN sources.

CORRELATIONS BETWEEN ULTRAHIGH ENERGY COSMIC RAYS AND INFRARED-LUMINOUS GALAXIES

We confirm the UHECR horizon established by the Pierre Auger Observatory using the heterogeneous Veron-Cetty Veron (VCV) catalog of AGNs, by performing a redshift-angle-IR luminosity scan using PSCz galaxies having infrared luminosity greater than 10^{10}L_sun. The strongest correlation -- for z < 0.016, psi = 2.1 deg, and L_ir > 10^{10.5}L_sun -- arises in fewer than 0.3% of scans with isotropic source directions. When we apply a penalty for using the UHECR energy threshold that was tuned to maximize the correlation with VCV, the significance degrades to 1.1%. Since the PSCz catalog is complete and volume-limited for these parameters, this suggests that the UHECR horizon discovered by the Pierre Auger Observatory is not an artifact of the incompleteness and other idiosyncrasies of the VCV catalog. The strength of the correlation between UHECRs and the nearby highest-IR-luminosity PSCz galaxies is stronger than in about 90% percent of trials with scrambled luminosity assignments for the PSCz galaxies. If confirmed by future data, this result would indicate that the sources of UHECRs are more strongly associated with luminous IR galaxies than with ordinary, lower IR luminosity galaxies.

A search for extragalactic sources of Ultrahigh-Energy Cosmic Rays

Possible extragalactic sources of cosmic rays at energies above 4 × 10 19 eV detected with the Yakutsk array are sought. Correlation of the shower arrival directions with objects from Veron's catalog that are located closer than 100 Mpc from the Earth confirms the observations at the Pierre Auger observatory, as well as the Greisen-Zatsepin-Kuzmin effect on ultrahigh-energy cosmic rays. The detailed analysis of the data reveals the classes of objects belonging to the active galactic nuclei that are probable sources of ultrahigh-energy cosmic rays.

GALAXIES CORRELATING WITH ULTRA-HIGH ENERGY COSMIC RAYS

The Pierre Auger Observatory reports that 20 of the 27 highest energy cosmic rays have arrival directions within 3.2 deg of a nearby galaxy in the Veron-Cetty & Veron Catalog of Quasars and Active Galactic Nuclei (12th Ed.), with ~5 of the correlations expected by chance. In this paper we examine the correlated galaxies to gain insight into the possible UHECR sources. We find that 14 of the 21 correlated VCV galaxies are AGNs and we determine their bolometric luminosities. The remaining 7 are primarily star-forming galaxies. The bolometric luminosities of the correlated AGNs are all greater than 5 x 10^{42} erg/s, which may explain the absence of UHECRs from the Virgo region in spite of the large number of VCV galaxies in Virgo, since most of the VCV galaxies in the Virgo region are low luminosity AGNs. Interestingly, the bolometric luminosities of most of the AGNs are significantly lower than required to satisfy the minimum condition for UHECR acceleration in a continuous jet. If a UHECR-AGN correlation is substantiated with further statistics, our results lend support to the recently proposed ``giant AGN flare" mechanism for UHECR acceleration.

Ultra-high energy cosmic rays detected by the Pierre Auger observatory

(abridged) The Pierre Auger Collaboration has reported 27 Ultra-High Energy Cosmic Ray Events (UHECRs) with energies above 56 EeV and well determined arrival directions as of 2007 August 31. They find that the arrival directions are not isotropic, but instead appear correlated with the positions of nearby AGNs. Our aim was to determine the sources of these UHECRs by comparing their arrival directions with more comprehensive source catalogs. Four (eight) of the 27 UHECRs with energy >56EeV detected by the Pierre Auger Observatory have arrival directions within 1.5deg (3.5deg) of the extended (>180kpc) radio structures of nearby radiogalaxies or the single nearby BLLac with extended radio structure. Conversely the radio structures of three (six) of all ten nearest extended radiogalaxies are within 1.5deg (3.5deg) of a UHECR; three of the remaining four radiogalaxies are in directions with lower exposure times. This correlation between nearby extended radiogalaxies and a subset of UHECRs is significant at the 99.9% level. This is the first direct observational proof that radio galaxies are a significant source of UHECRs. For the remaining ~20 UHECRs, an isotropic distribution cannot be ruled out at high significance. The correlation found by the Auger Collaboration between the 27 UHECRs and AGNs in the Veron-Cetty & Veron catalog at D < 71Mpc has a much lower significance when one considers only the ~20 UHECRs not `matched' to nearby extended radiogalaxies. No correlation is seen between UHECRs and supernovae, supernova remnants, nearby galaxies, or nearby groups and clusters of galaxies. The primary difference between the UHECR detections at the Pierre Auger Observatory and previous experiments may thus be that the Southern Hemisphere is more privileged with respect to nearby extended radiogalaxies.