- ID:
- ivo://CDS.VizieR/J/ApJS/230/9
- Title:
- Improved multi-band photometry from SERVS
- Short Name:
- J/ApJS/230/9
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We apply The Tractor image modeling code to improve upon existing multi-band photometry for the Spitzer Extragalactic Representative Volume Survey (SERVS). SERVS consists of post-cryogenic Spitzer observations at 3.6 and 4.5{mu}m over five well-studied deep fields spanning 18deg^2^. In concert with data from ground-based near-infrared (NIR) and optical surveys, SERVS aims to provide a census of the properties of massive galaxies out to z~5. To accomplish this, we are using The Tractor to perform "forced photometry." This technique employs prior measurements of source positions and surface brightness profiles from a high-resolution fiducial band from the VISTA Deep Extragalactic Observations survey to model and fit the fluxes at lower-resolution bands. We discuss our implementation of The Tractor over a square-degree test region within the XMM Large Scale Structure field with deep imaging in 12 NIR/optical bands. Our new multi-band source catalogs offer a number of advantages over traditional position-matched catalogs, including (G1) consistent source cross-identification between bands, (2) de-blending of sources that are clearly resolved in the fiducial band but blended in the lower resolution SERVS data, (3) a higher source detection fraction in each band, (4) a larger number of candidate galaxies in the redshift range 5<z<6, and (5) a statistically significant improvement in the photometric redshift accuracy as evidenced by the significant decrease in the fraction of outliers compared to spectroscopic redshifts. Thus, forced photometry using The Tractor offers a means of improving the accuracy of multi-band extragalactic surveys designed for galaxy evolution studies. We will extend our application of this technique to the full SERVS footprint in the future.
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- ID:
- ivo://CDS.VizieR/J/MNRAS/405/2302
- Title:
- Improved redshifts for SDSS quasar spectra
- Short Name:
- J/MNRAS/405/2302
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A systematic investigation of the relationship between different redshift estimation schemes for more than 91000 quasars in the Sloan Digital Sky Survey (SDSS) Data Release 6 is presented. The publicly available SDSS quasar redshifts are shown to possess systematic biases of {Delta}z/(1+z)>=0.002 (600km/s) over both small ({delta}z~=0.1) and large ({delta}z~=1) redshift intervals. Empirical relationships between redshifts based on (i) CaII H&K host galaxy absorption, (ii) quasar [OII] {lambda}{lambda}3728, (iii) [OIII] {lambda}{lambda} 4960, 5008 emission and (iv) cross-correlation (with a master-quasar template) that includes, at increasing quasar redshift, the prominent MgII {lambda}{lambda} 2799, CIII] {lambda}{lambda} 1908 and CIV {lambda}{lambda} 1549 emission lines are established as a function of quasar redshift and luminosity. New redshifts in the resulting catalogue possess systematic biases, a factor of ~=20 lower compared to the SDSS redshift values; systematic effects are reduced to the level of {Delta}z/(1+z) (30km/s) per unit redshift or <=2.5x10^-5^ per unit absolute magnitude. Redshift errors, including components due both to internal reproducibility and to the intrinsic quasar-to-quasar variation among the population, are available for all quasars in the catalogue. The improved redshifts and their associated errors have wide applicability in areas such as quasar absorption outflows, quasar clustering, quasar-galaxy clustering and proximity-effect determinations.
- ID:
- ivo://CDS.VizieR/J/A+A/646/A104
- Title:
- Improving the open cluster census. I.
- Short Name:
- J/A+A/646/A104
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The census of open clusters in the Milky Way is in a never-before seen state of flux. Recent works have reported hundreds of new open clusters thanks to the incredible astrometric quality of the Gaia satellite, but other works have also reported that many open clusters discovered in the pre Gaia era may be associations. We aim to conduct a comparison of clustering algorithms used to detect open clusters, attempting to statistically quantify their strengths and weaknesses by deriving the sensitivity, specificity, and precision of each as well as their true positive rate against a larger sample. We selected DBSCAN, HDBSCAN, and Gaussian mixture models for further study, owing to their speed and appropriateness for use with Gaia data. We developed a preprocessing pipeline for Gaia data and developed the algorithms further for the specific application to open clusters. We derived detection rates for all 1385 open clusters in the fields in our study as well as more detailed performance statistics for 100 of these open clusters. DBSCAN was sensitive to 50%-62% of the true positive open clusters in our sample, with generally very good specificity and precision. HDBSCAN traded precision for a higher sensitivity of up to 82%, especially across different distances and scales of open clusters. Gaussian mixture models were slow and only sensitive to 33% of open clusters in our sample, which tended to be larger objects. Additionally, we report on 41 new open cluster candidates detected by HDBSCAN, three of which are closer than 500pc. When used with additional post-processing to mitigate its false positives, we have found that HDBSCAN is the most sensitive and effective algorithm for recovering open clusters in Gaia data. Our results suggest that many more new and already reported open clusters have yet to be detected in Gaia data.
- ID:
- ivo://CDS.VizieR/J/MNRAS/499/6053
- Title:
- Indiv. opt. variability of AGNs from MEXSAS2
- Short Name:
- J/MNRAS/499/6053
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- At present, most of the variability studies of active galactic nuclei (AGNs) are based on ensemble analyses. Nevertheless, it is interesting to provide estimates of the individual variability properties of each AGN, in order to relate them with intrinsic physical quantities. A useful dataset is provided by the Catalina Surveys Data Release 2 (CSDR2), which encompasses almost a decade of photometric measurements of ~500 million objects repeatedly observed hundreds of times.We aim to investigate the individual optical variability properties of 795 AGNs originally included in the Multi-Epoch XMMSerendipitous AGN Sample 2 (MEXSAS2). Our goals consist in: (i) searching for correlations between variability and AGN physical quantities; (ii) extending our knowledge of the variability features of MEXSAS2 from the X-ray to the optical.We use the structure function (SF) to analyse AGN flux variations. We model the SF as a power-law, SF(tau)=A(tau/tau_0)^gamma^, and we compute its variability parameters. We introduce the V-correction as a simple tool to correctly quantify the amount of variability in the rest frame of each source.We find a significant decrease of variability amplitude with increasing bolometric, optical and X-ray luminosity. We obtain the indication of an intrinsically weak positive correlation between variability amplitude and redshift, z. Variability amplitude also appears to be positively correlated with alpha_{ox}.The slope of the power-law SF, gamma, is weakly correlated with the bolometric luminosity L_{bol} and/or with the black hole mass M_{BH}. When comparing optical to X-ray variability properties, we find that X-ray variability amplitude is approximately the same for those AGNs with larger or smaller variability amplitude in the optical.On the contrary, AGNs with steeper SF in the optical do present steeper SF in the X-ray, and vice versa.
- ID:
- ivo://CDS.VizieR/J/ApJ/649/L9
- Title:
- INTEGRAL IBIS census of the sky beyond 100keV
- Short Name:
- J/ApJ/649/L9
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report on the first census of INTEGRAL IBIS detections (>~4{sigma} significance) above 100keV based on the Core Program and public open-time observations up to 2005 April. There are 49 sources detected in the 100-150keV band, of which 14 are also seen in the 150-300keV range. The low-energy sample is dominated by X-ray binary systems of both low and high mass but also includes 10 active galaxies.
- ID:
- ivo://CDS.VizieR/J/A+A/545/A27
- Title:
- INTEGRAL/IBIS 9-year Galactic hard X-ray survey
- Short Name:
- J/A+A/545/A27
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present sky images, sensitivity maps, and catalogs of detected sources in the three energy bands 17-60, 17-35, and 35-80keV in the Galactic plane at |b|<17.5 degrees. The total number of sources in the reference 17-60keV band includes 402 objects exceeding a 4.7{sigma} detection threshold on the nine-year time-averaged map. Among the identified sources with known and tentatively identified natures, 253 are Galactic objects (108 low-mass X-ray binaries, 82 high-mass X-ray binaries, 36 cataclysmic variables, and 27 are of other types), and 115 are extragalactic objects, including 112 active galactic nuclei (AGNs) and 3 galaxy clusters. The sample of Galactic sources with S/N>4.7 sigma has an identification completeness of ~92%, which is valuable for population studies. Since the survey is based on the nine-year sky maps, it is optimized for persistent sources and may be biased against finding transients.
- ID:
- ivo://CDS.VizieR/J/MNRAS/470/512
- Title:
- INTEGRAL 14-year Galactic hard X-ray sources
- Short Name:
- J/MNRAS/470/512
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The International Gamma-Ray Astrophysics Laboratory (INTEGRAL) continues to successfully work in orbit after its launch in 2002. The mission provides the deepest ever survey of hard X-ray sources throughout the Galaxy at energies above 20keV. We report on a catalogue of new hard X-ray source candidates based on the latest sky maps comprising 14yr of data acquired with the IBIS telescope onboard INTEGRAL in the Galactic Plane (|b|<17.5{deg}). The current catalogue includes in total 72 hard X-ray sources detected at S/N>4.7{sigma} and not known to previous INTEGRAL surveys. Among them, 31 objects have also been detected in the on-going all-sky survey by the BAT telescope of the Swift observatory. For 26 sources on the list, we suggest possible identifications: 21 active galactic nuclei, two cataclysmic variables, two isolated pulsars or pulsar wind nebulae and one supernova remnant; 46 sources from the catalogue remain unclassified.
- ID:
- ivo://CDS.VizieR/J/MNRAS/448/3766
- Title:
- INTEGRAL 11-year hard X-ray survey
- Short Name:
- J/MNRAS/448/3766
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of an all-sky survey, performed with data acquired by the Imager on-Board the INTEGRAL Satellite (IBIS) telescope on board the INTErnational Gamma-Ray Astrophysics Laboratory (INTEGRAL) observatory over 11 years of operation, at energies above 100 keV. The catalogue of detected sources includes 132 objects. The statistical sample detected on the time-averaged 100-150 keV map at a significance above 5{sigma} contains 88 sources: 28 active galactic nuclei (AGNs), 38 low-mass X-ray binaries (LMXBs), 10 high-mass X-ray binaries (HMXBs) and 12 rotation-powered young X-ray pulsars. The catalogue also includes 15 persistent sources, which were registered at significance 4{sigma}<=S/N<5{sigma}, where S/N is the signal-to-noise ratio, but at the same time were firmly detected (>=12{sigma}) in the lower 17-60keV energy band. All registered sources are known X-ray emitters, which means that the catalogue has 100 percent purity in this respect. Additionally, 29 catalogued sources were detected significantly in different time slices of the survey. In the context of the survey, we present a hardness ratio for Galactic and extragalactic sources, an LMXB longitudinal asymmetry and a number-flux relation for non-blazar AGNs. At higher energies, in the 150-300keV energy band, 25 sources have been detected with S/N>=5{sigma}, including seven AGNs, 13 LMXBs, three HMXBs and two rotation-powered pulsars. Among LMXBs and HMXBs, we identified 12 black hole candidates (BHCs) and four neutron star (NS) binaries.
- ID:
- ivo://CDS.VizieR/J/AJ/77/405
- Title:
- Intense radio sources at 1400MHz (BDFL sample)
- Short Name:
- J/AJ/77/405
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Accurate flux densities, precise positions of unresolved sources, and structures of resolved sources have been derived from full-beam and interferometric observations of intense sources at 1400 MHz. Results are given for 424 sources in the area of sky -5{deg}<{delta}<+70{deg}, |b|>5 whose 1400-MHz integrated flux densities S_1400_ exceed 1.70Jy [1 Jy (flux unit) = 10^-26^w/m^2^/Hz]. The 234 sources with S_1400_>=2.00Jy, equivalent diameters <10arcmin, and |b|>20{deg} form a 98+/-2% complete sample comparable in number to the 178-MHz Revised Third Cambridge Catalogue in this 4.30-sr area of sky, but selected at 1400MHz. This sample is suitable for statistical studies of the properties of extragalactic radio sources. To facilitate its use, and that of other samples which may be drawn from these data, references to other studies of the positions, fine and extended structure, polarization, and variability of the sources have been assembled in the principal table of this paper (Table 2). A comparison is made with other 1400-MHz flux-density data (Sec. 3), and the spectral content of the complete sample is discussed (Sec. 4).
- ID:
- ivo://CDS.VizieR/J/A+AS/92/625
- Title:
- Ionized nebulae in M31
- Short Name:
- J/A+AS/92/625
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Deep CCD imagery in H{alpha} and [SII] is presented of the major spiral arms of M31 with particular attention given to the data reduction and the analysis of the [SII]/H{alpha} flux ratios. A diffuse ionized gas noted in the images is analyzed which shows higher [SII]/H{alpha} ratios, and 967 discrete nebulae are listed with gray-scale images, finding charts, and absolute fluxes. The differential H-alpha luminosity function is found to have a slope of -0.95 for brighter objects and flattens out below a critical level. The curve is shown to correspond to the point at which single-star ionization accounts for the H{alpha} luminosities and is consistent with previous observations. The catalog of objects and fluxes is the largest existing sample of this type, and the unresolved objects in the sample are considered to be planetary nebulae.
