- ID:
- ivo://CDS.VizieR/J/MNRAS/457/110
- Title:
- Northern XMM-XXL field AGN catalog
- Short Name:
- J/MNRAS/457/110
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This paper presents a survey of X-ray-selected active galactic nuclei (AGNs) with optical spectroscopic follow-up in a ~18deg^2^ area of the equatorial XMM-XXL north field. A sample of 8445 point-like X-ray sources detected by XMM-Newton above a limiting flux of F_0.5-10keV_>10^-15^erg/cm2/s was matched to optical (Sloan Digital Sky Survey, SDSS) and infrared (IR; WISE) counterparts. We followed up 3042 sources brighter than r=22.5mag with the SDSS Baryon Oscillation Spectroscopic Survey (BOSS) spectrograph. The spectra yielded a reliable redshift measurement for 2578 AGNs in the redshift range z=0.02-5.0, with 0.5-2keV luminosities ranging from 10^39^-10^46^erg/s. This is currently the largest published spectroscopic sample of X-ray-selected AGNs in a contiguous area. The BOSS spectra of AGN candidates show a distribution of optical line widths which is clearly bimodal, allowing an efficient separation between broad- and narrow-emission line AGNs. The former dominate our sample (70 per cent) due to the relatively bright X-ray flux limit and the optical BOSS magnitude limit. We classify the narrow-emission line objects (22 per cent of the full sample) using standard optical emission line diagnostics: the majority have line ratios indicating the dominant source of ionization is the AGN. A small number (8 per cent of the full sample) exhibit the typical narrow line ratios of star-forming galaxies, or only have absorption lines in their spectra. We term the latter two classes 'elusive' AGN, which would not be easy to identify correctly without their X-ray emission. We also compare X-ray (XMM-Newton), optical colour (SDSS) and and IR (WISE) AGN selections in this field. X-ray observations reveal, by far, the largest number of AGN. The overlap between the selections, which is a strong function of the imaging depth in a given band, is also remarkably small. We show using spectral stacking that a large fraction of the X-ray AGNs would not be selectable via optical or IR colours due to host galaxy contamination. A substantial fraction of AGN may therefore be missed by these longer wavelength selection methods.
Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/J/ApJ/819/27
- Title:
- OAO/MuSCAT light curves of HAT-P-14b
- Short Name:
- J/ApJ/819/27
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Multicolor Simultaneous Camera for studying Atmospheres of Transiting exoplanets (MuSCAT) is an optical three-band (g'_2_-, r'_2_- and z_s,2_-band) imager that was recently developed for the 188cm telescope at Okayama Astrophysical Observatory with the aim of validating and characterizing transiting planets. In a pilot observation with MuSCAT we observed a primary transit of HAT-P-14b, a high-surface gravity (g_p_=38ms^-2^) hot Jupiter around a bright (V=10) F-type star. From a 2.9hr observation we achieved the five-minute binned photometric precisions of 0.028%, 0.022%, and 0.024% in the g'_2_, r'_2_, and z_s,2_ bands, respectively, which provided the highest-quality photometric data for this planet. Combining these results with those of previous observations, we search for variations of transit timing and duration over five years as well as variations of planet-star radius ratio (Rp/Rs) with wavelengths, but can find no considerable variation in any parameters. On the other hand, using the transit-subtracted light curves we simulate the achievable measurement error of Rp/Rs with MuSCAT for various planetary sizes, assuming three types of host stars: HAT-P-14, the nearby K-dwarf HAT-P-11, and the nearby M-dwarf GJ1214. Comparing our results with the expected atmospheric scale heights, we find that MuSCAT is capable of probing the atmospheres of planets as small as a sub-Jupiter (Rp~6R_{earth}_) around HAT-P-14 in all bands, a Neptune (~4R_{earth}_) around HAT-P-11 in all bands, and a super-Earth (~2.5R_{earth}_) around GJ1214 in r'_2_ and z_s,2_ bands. These results promise that MuSCAT will produce fruitful scientific outcomes in the K2 and TESS era.
- ID:
- ivo://CDS.VizieR/J/AJ/134/2385
- Title:
- Occulting galaxy pairs in SDSS
- Short Name:
- J/AJ/134/2385
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A spiral galaxy partially overlapping a more distant elliptical offers a unique opportunity to measure the dust extinction in the foreground spiral. From the Sloan Digital Sky Survey (SDSS) DR4 spectroscopic sample, we selected 83 occulting galaxy pairs and measured disk opacity over the redshift range z=0.0-0.2 with the goal of determining the recent evolution of disk dust opacity. The enrichment of the ISM changes over the lifetime of a disk, and it is reasonable to expect the dust extinction properties of spiral disks as a whole to change over their lifetime. When they do, the change will affect our measurements of galaxies over the observable universe. From the SDSS pairs we conclude that spiral disks show evidence of extinction to ~2 effective radii.
- ID:
- ivo://CDS.VizieR/J/A+A/522/A29
- Title:
- OGLE2-TR-L9 g'r'i'z' light curves
- Short Name:
- J/A+A/522/A29
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Repeated observations of exoplanet transits allow us to refine the planetary parameters and probe them for any time dependent variations. In particular deviations of the period from a strictly linear ephemeris, transit timing variations (TTVs), can indicate the presence of additional bodies in the planetary system. Aims: Our goal was to reexamine the largely unstudied OGLE2-TR-L9 system with high cadence, multi-color photometry in order to refine the planetary parameters and probe the system for TTVs. From our analysis we find that the semi-major axis and the inclination differ from the previously published values. With the newly observed transits, we were able to refine the ephemeris to 2454492.80008(+/-0.00014) +2.48553417(+/-6.4)x10^-7^E. The newly derived parameters are a=0.0418(+/-0.0015)AU, r_p_=1.67(+/-0.05) R_j_, and inc=82.47{deg}(+/-0.12), differing significantly in a and inc from the previously published values. Within our data, we find indications for TTVs.
- ID:
- ivo://CDS.VizieR/J/ApJS/254/30
- Title:
- One-side head-tail (OHT) galaxies from FIRST & SDSS
- Short Name:
- J/ApJS/254/30
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- One-side head-tail (OHT) galaxies are radio galaxies with a peculiar shape. They usually appear in galaxy clusters, but they have never been cataloged systematically. We design an automatic procedure to search for them in the Faint Images of the Radio Sky at Twenty-Centimeters source catalog and compile a sample with 115 HT candidates. After cross-checking with the Sloan Digital Sky Survey photometric data and catalogs of galaxy clusters, we find that 69 of them are possible OHT galaxies. Most of them are close to the center of galaxy clusters. The lengths of their tails do not correlate with the projection distance to the center of the nearest galaxy clusters, but show weak anticorrelation with the cluster richness, and are inversely proportional to the radial velocity differences between clusters and host galaxies. Our catalog provides a unique sample to study this special type of radio galaxies.
- ID:
- ivo://CDS.VizieR/J/MNRAS/481/2458
- Title:
- On the nature of small galaxy systems
- Short Name:
- J/MNRAS/481/2458
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We aim at defining homogeneous selection criteria of small galaxy systems in order to build catalogues suitable to compare main properties of pairs, triplets, and groups with four or more members. To this end we use spectroscopic and photometric Sloan Digital Sky Survey (SDSS) data to identify systems with a low number of members. We study global properties of these systems and the properties of their member galaxies finding that galaxies in groups are systematically redder and with lower star formation activity indicators than galaxies in pairs which have a higher fraction of star-forming galaxies. Triplet galaxies present intermediate trends between pairs and groups. We also find an enhancement of star formation activity for galaxies in small systems with companions closer than 100kpc, irrespective of the number of members. We have tested these analyses on SDSS mock catalogues derived from the Millennium simulation, finding as conservative thresholds 76 per cent completeness and a contamination of 23 per cent in small galaxy systems, when considering an extreme case of incompleteness due to fiber collisions. Nevertheless, we also found that the results obtained are not likely affected by projection effects. Our studies suggest that an extra galaxy in a system modify the properties of the member galaxies. In pairs, galaxy-galaxy interactions increase gas density and trigger starbursts. However, repeated interactions in triplets and groups can generate gas stripping, turbulence, and shocks quenching the star formation in these systems.
- ID:
- ivo://CDS.VizieR/J/MNRAS/470/3937
- Title:
- 1876 open clusters multimembership catalog
- Short Name:
- J/MNRAS/470/3937
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The main objective of this work is to determine the cluster members of 1876 open clusters, using positions and proper motions of the astrometric fourth United States Naval Observatory (USNO) CCD Astrograph Catalog (UCAC4). For this purpose, we apply three different methods, all based on a Bayesian approach, but with different formulations: a purely parametric method, another completely non-parametric algorithm and a third, recently developed by Sampedro & Alfaro (2016MNRAS.457.3949S), using both formulations at different steps of the whole process. The first and second statistical moments of the members' phase-space subspace, obtained after applying the three methods, are compared for every cluster. Although, on average, the three methods yield similar results, there are also specific differences between them, as well as for some particular clusters. The comparison with other published catalogues shows good agreement. We have also estimated, for the first time, the mean proper motion for a sample of 18 clusters. The results are organized in a single catalogue formed by two main files, one with the most relevant information for each cluster, partially including that in UCAC4, and the other showing the individual membership probabilities for each star in the cluster area. The final catalogue, with an interface design that enables an easy interaction with the user, is available in electronic format at the Stellar Systems Group (SSG-IAA) web site (http://ssg.iaa.es/en/content/sampedro-cluster-catalog).
- ID:
- ivo://CDS.VizieR/J/A+A/640/A9
- Title:
- Open star cluster Coma Berenices multi-photometry
- Short Name:
- J/A+A/640/A9
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We mainly aim to search for the lithium depletion boundary (LDB) among the sub-stellar population of the open star cluster Coma Berenices. Since the number of brown dwarf candidates in Coma Ber available in the literature is scarce, we carried out a search for additional candidates photometrically using colour-magnitude diagrams combining optical and infrared photometry from the latest public releases of the following large-scale surveys: the United Kingdom InfraRed Telescope Infrared Deep Sky Survey (UKIRT/UKIDSS), the Panoramic Survey Telescope and Rapid Response System (Pan-STARRS), the Sloan Digital Sky Survey (SDSS), and AllWISE. We checked astrometric consistency with cluster membership using Gaia DR2. A search for Li in three new and five previously known brown dwarf candidate cluster members was performed via spectroscopic observations using the OSIRIS instrument at the 10.4m Gran Telescopio de Canarias (GTC). A couple dozen new photometric candidate brown dwarfs located inside the tidal radius of Coma Ber are reported, but none of these are significantly fainter and cooler than previously known members. No LiI resonance doublet at 6707.8{AA} was detected in any of eight Coma Ber targets in the magnitude range J=15-19 and G=20-23 observed with the GTC. Spectral types and radial velocities were derived from the GTC spectra. These values confirm the cluster membership of four L2-L2.5 dwarfs, two of which are new in the literature. The large Li depletion factors found among the four bona fide sub-stellar members in Coma Ber implies that the LDB must be located at spectral type later than L2.5 in this cluster. Using the latest evolutionary models for brown dwarfs, a lower limit of 550Myr on the cluster age is set. This constraint has been combined with other dating methods to obtain an updated age estimate of 780+/-230Myr for the Coma Ber open cluster. Identification of significantly cooler sub-stellar cluster members in Coma Ber awaits the advent of the Euclid wide survey, which should reach a depth of about J=23; this superb sensitivity will make it possible to determine the precise location of the sub-stellar LDB in this cluster and to carry out a complete census of its sub-stellar population.
- ID:
- ivo://CDS.VizieR/J/ApJ/848/L29
- Title:
- Opt. follow-up of GW170817 counterpart
- Short Name:
- J/ApJ/848/L29
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of prompt optical follow-up of the electromagnetic counterpart of the gravitational-wave event GW170817 by the Transient Optical Robotic Observatory of the South Collaboration. We detected highly significant dimming in the light curves of the counterpart ({Delta}g=0.17+/-0.03mag, {Delta}r=0.14+/-0.02mag, {Delta}i=0.10+/-0.03mag) over the course of only 80 minutes of observations obtained ~35hr after the trigger with the T80-South telescope. A second epoch of observations, obtained ~59hr after the event with the EABA 1.5m telescope, confirms the fast fading nature of the transient. The observed colors of the counterpart suggest that this event was a "blue kilonova" relatively free of lanthanides.
- ID:
- ivo://CDS.VizieR/J/AJ/144/16
- Title:
- Optical and HI properties of galaxies in voids
- Short Name:
- J/AJ/144/16
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have carefully selected a sample of 60 galaxies that reside in the deepest underdensities of geometrically identified voids within the Sloan Digital Sky Survey. HI imaging of 55 galaxies with the Westerbork Synthesis Radio Telescope reveals morphological and kinematic signatures of ongoing interactions and gas accretion. We probe a total volume of 485Mpc^3^ within the voids, with an angular resolution of 8kpc at an average distance of 85Mpc. We reach column density sensitivities of 5x10^19^/cm^-2^, corresponding to an HI mass limit of 3x10^8^M_{sun}_. We detect HI in 41 galaxies, with total masses ranging from 1.7x10^8^ to 5.5x10^9^M_{sun}_. The upper limits on the 14 non-detections are not inconsistent with their luminosities, given their expected HI mass-to-light ratios. We find that the void galaxies are generally gas-rich, low-luminosity, blue disk galaxies, with optical and HI properties that are not unusual for their luminosity and morphology. The sample spans a range of absolute magnitudes (-16.1>M_r_>-20.4) and colors (0.06<g-r<0.87), and includes disk and irregular galaxies. We also identify three as early-type galaxies, all of which are not detected in HI. All galaxies have stellar masses less than 3x10^10^M_{sun}_, and many have kinematic and morphological signs of ongoing gas accretion, suggesting that the void galaxy population is still in the process of assembling. The small-scale clustering in the void, within 600kpc and 200km/s, is similar to that in higher density regions, and we identify 18 HI-rich neighboring galaxies in the voids. Most are within 100kpc and 100km/s of the targeted galaxy, and we find no significant population of HI-rich low-luminosity galaxies filling the voids, contrary to what is predicted by simulations.
