- ID:
- ivo://CDS.VizieR/J/ApJS/243/21
- Title:
- A complete sample of broad-line AGN from SDSS-DR7
- Short Name:
- J/ApJS/243/21
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A new, complete sample of 14584 broad-line active galactic nuclei (AGNs) at z<0.35 is presented, which are uncovered homogeneously from the complete database of galaxies and quasars observed spectroscopically in the Sloan Digital Sky Survey Seventh Data Release. The stellar continuum is properly removed for each spectrum with significant host absorption line features, and careful analyses of the emission line spectra, particularly in the H{alpha} and H{beta} wavebands, are carried out. The broad Balmer emission line, particularly H{alpha}, is used to indicate the presence of an AGN. The broad H{alpha} lines have luminosities in a range of 10^38.5^-10^44.3^erg/s, and line widths (FWHMs) of 500-34000km/s. The virial black hole masses, estimated from the broad-line measurements, span a range of 10^5.1^-10^10.3^M_{sun}_, and the Eddington ratios vary from -3.3 to 1.3 in logarithmic scale. Other quantities such as multiwavelength photometric properties and flags denoting peculiar line profiles are also included in this catalog. We describe the construction of this catalog and briefly discuss its properties. The catalog is publicly available online. This homogeneously selected AGN catalog, along with the accurately measured spectral parameters, provides the most updated, largest AGN sample data, which will enable further comprehensive investigations of the properties of the AGN population in the low-redshift universe.
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- ID:
- ivo://CDS.VizieR/J/ApJS/220/10
- Title:
- AEGIS-X Deep survey of EGS (AEGIS-XD)
- Short Name:
- J/ApJS/220/10
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of deep Chandra imaging of the central region of the Extended Groth Strip, the AEGIS-X Deep (AEGIS-XD) survey. When combined with previous Chandra observations of a wider area of the strip, AEGIS-X Wide (AEGIS-XW), these provide data to a nominal exposure depth of 800ks in the three central ACIS-I fields, a region of approximately 0.29deg^2^. This is currently the third deepest X-ray survey in existence; a factor ~2-3 shallower than the Chandra Deep Fields (CDFs), but over an area ~3 times greater than each CDF. We present a catalog of 937 point sources detected in the deep Chandra observations, along with identifications of our X-ray sources from deep ground-based, Spitzer, GALEX, and Hubble Space Telescope imaging. Using a likelihood ratio analysis, we associate multiband counterparts for 929/937 of our X-ray sources, with an estimated 95% reliability, making the identification completeness approximately 94% in a statistical sense. Reliable spectroscopic redshifts for 353 of our X-ray sources are available predominantly from Keck (DEEP2/3) and MMT Hectospec, so the current spectroscopic completeness is ~38%. For the remainder of the X-ray sources, we compute photometric redshifts based on multiband photometry in up to 35 bands from the UV to mid-IR. Particular attention is given to the fact that the vast majority the X-ray sources are active galactic nuclei and require hybrid templates. Our photometric redshifts have mean accuracy of {sigma}=0.04 and an outlier fraction of approximately 5%, reaching {sigma}=0.03 with less than 4% outliers in the area covered by CANDELS.
- ID:
- ivo://CDS.VizieR/J/AJ/146/87
- Title:
- AGN photometry. II. A catalog from the CFHTLS
- Short Name:
- J/AJ/146/87
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This is the second paper of the series Detecting Active Galactic Nuclei Using Multi-filter Imaging Data. In this paper we review shapelets, an image manipulation algorithm, which we employ to adjust the point-spread function (PSF) of galaxy images. This technique is used to ensure the image in each filter has the same and sharpest PSF, which is the preferred condition for detecting AGNs using multi-filter imaging data as we demonstrated in Paper I of this series. We apply shapelets on Canada-France-Hawaii Telescope Legacy Survey Wide Survey ugriz images. Photometric parameters such as effective radii, integrated fluxes within certain radii, and color gradients are measured on the shapelets-reconstructed images. These parameters are used by artificial neural networks (ANNs) which yield: photometric redshift with an rms of 0.026 and a regression R-value of 0.92; galaxy morphological types with an uncertainty less than 2 T types for z<=0.1; and identification of galaxies as AGNs with 70% confidence, star-forming/starburst (SF/SB) galaxies with 90% confidence, and passive galaxies with 70% confidence for z<=0.1. The incorporation of ANNs provides a more reliable technique for identifying AGN or SF/SB candidates, which could be very useful for large-scale multi-filter optical surveys that also include a modest set of spectroscopic data sufficient to train neural networks.
- ID:
- ivo://CDS.VizieR/J/ApJS/183/295
- Title:
- A K-selected catalog of the ECDFS from MUSYC
- Short Name:
- J/ApJS/183/295
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a new, K-selected, optical-to-near infrared photometric catalog of the Extended Chandra Deep Field South (ECDFS), making it publicly available to the astronomical community. The data set is founded on publicly available imaging, supplemented by original z'JK imaging data collected as part of the MUltiwavelength Survey by Yale-Chile (MUSYC). The final photometric catalog consists of photometry derived from UU_38_BVRIz'JK imaging covering the full 1/2x1/2{deg} of the ECDFS, plus H-band photometry for approximately 80% of the field. The 5{sigma} flux limit for point sources is K^(AB)^_tot_=22.0. This is also the nominal completeness and reliability limit of the catalog: the empirical completeness for 21.75<K<22.00 is >~85%. We have verified the quality of the catalog through both internal consistency checks, and comparisons to other existing and publicly available catalogs. As well as the photometric catalog, we also present catalogs of photometric redshifts and rest-frame photometry derived from the 10-band photometry. We have collected robust spectroscopic redshift determinations from published sources for 1966 galaxies in the catalog. Based on these sources, we have achieved a (1{sigma}) photometric redshift accuracy of {Delta}z/(1+z)=0.036, with an outlier fraction of 7.8%. Most of these outliers are X-ray sources. Finally, we describe and release a utility for interpolating rest-frame photometry from observed spectral energy distributions, dubbed InterRest available via http://www.strw.leidenuniv.nl/~ent/InterRest
- ID:
- ivo://CDS.VizieR/J/ApJ/788/125
- Title:
- An ALMA survey of ECDFS submillimeter galaxies
- Short Name:
- J/ApJ/788/125
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the first photometric redshift distribution for a large sample of 870 {mu}m submillimeter galaxies (SMGs) with robust identifications based on observations with ALMA. In our analysis we consider 96 SMGs in the Extended Chandra Deep Field South, 77 of which have 4-19 band photometry. We model the SEDs for these 77 SMGs, deriving a median photometric redshift of z_phot_=2.3+/-0.1. The remaining 19 SMGs have insufficient photometry to derive photometric redshifts, but a stacking analysis of Herschel observations confirms they are not spurious. Assuming that these SMGs have an absolute H-band magnitude distribution comparable to that of a complete sample of z~1-2 SMGs, we demonstrate that they lie at slightly higher redshifts, raising the median redshift for SMGs to z_phot_=2.5+/-0.2. Critically we show that the proportion of galaxies undergoing an SMG-like phase at z>=3 is at most 35%+/-5% of the total population. We derive a median stellar mass of M_*_=(8+/-1)x10^10^ M_{sun}_, although there are systematic uncertainties of up to 5x for individual sources. Assuming that the star formation activity in SMGs has a timescale of ~100 Myr, we show that their descendants at z~0 would have a space density and M_H_ distribution that are in good agreement with those of local ellipticals. In addition, the inferred mass-weighted ages of the local ellipticals broadly agree with the look-back times of the SMG events. Taken together, these results are consistent with a simple model that identifies SMGs as events that form most of the stars seen in the majority of luminous elliptical galaxies at the present day.
- ID:
- ivo://CDS.VizieR/J/AJ/154/269
- Title:
- A new photo-z method for quasars in Stripe 82
- Short Name:
- J/AJ/154/269
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a new algorithm to estimate quasar photometric redshifts (photo-zs), by considering the asymmetries in the relative flux distributions of quasars. The relative flux models are built with multivariate Skew-t distributions in the multidimensional space of relative fluxes as a function of redshift and magnitude. For 151392 quasars in the SDSS, we achieve a photo-z accuracy, defined as the fraction of quasars with the difference between the photo-z z_p_ and the spectroscopic redshift z_s_, |{Delta}_z_|=|z_s_-z_p_|/(1+z_s_) within 0.1, of 74%. Combining the WISE W1 and W2 infrared data with the SDSS data, the photo-z accuracy is enhanced to 87%. Using the Pan-STARRS1 or DECaLS photometry with WISE W1 and W2 data, the photo-z accuracies are 79% and 72%, respectively. The prior probabilities as a function of magnitude for quasars, stars, and galaxies are calculated, respectively, based on (1) the quasar luminosity function, (2) the Milky Way synthetic simulation with the Besancon model, and (3) the Bayesian Galaxy Photometric Redshift estimation. The relative fluxes of stars are obtained with the Padova isochrones, and the relative fluxes of galaxies are modeled through galaxy templates. We test our classification method to select quasars using the DECaLS g, r, z, and WISE W1 and W2 photometry. The quasar selection completeness is higher than 70% for a wide redshift range 0.5<z<4.5, and a wide magnitude range 18<r<21.5 mag. Our photo-z regression and classification method has the potential to extend to future surveys. The photo-z code will be publicly available.
- ID:
- ivo://CDS.VizieR/J/AJ/153/107
- Title:
- Australian Dark Energy Survey (OzDES) quasar catalog
- Short Name:
- J/AJ/153/107
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a study of quasar selection using the supernova fields of the Dark Energy Survey (DES). We used a quasar catalog from an overlapping portion of the SDSS Stripe 82 region to quantify the completeness and efficiency of selection methods involving color, probabilistic modeling, variability, and combinations of color/probabilistic modeling with variability. In all cases, we considered only objects that appear as point sources in the DES images. We examine color selection methods based on the Wide-field Infrared Survey Explorer (WISE) (Wright et al. 2010AJ....140.1868W) mid-IR W1-W2 color, a mixture of WISE and DES colors (g-i and i-W1), and a mixture of Vista Hemisphere Survey (McMahon et al. 2013Msngr.154...35M) and DES colors (g-i and i-K). For probabilistic quasar selection, we used XDQSO, an algorithm that employs an empirical multi-wavelength flux model of quasars to assign quasar probabilities. Our variability selection uses the multi-band {chi}^2^-probability that sources are constant in the DES Year 1 griz-band light curves. The completeness and efficiency are calculated relative to an underlying sample of point sources that are detected in the required selection bands and pass our data quality and photometric error cuts. We conduct our analyses at two magnitude limits, i<19.8 mag and i<22 mag. For the subset of sources with W1 and W2 detections, the W1-W2 color or XDQSOz method combined with variability gives the highest completenesses of >85% for both i-band magnitude limits and efficiencies of >80% to the bright limit and >60% to the faint limit; however, the giW1 and giW1+variability methods give the highest quasar surface densities. The XDQSOz method and combinations of W1W2/giW1/XDQSOz with variability are among the better selection methods when both high completeness and high efficiency are desired. We also present the OzDES Quasar Catalog of 1263 spectroscopically confirmed quasars from three years of OzDES observation in the 30 deg^2^ of the DES supernova fields. The catalog includes quasars with redshifts up to z~4 and brighter than i=22 mag, although the catalog is not complete up to this magnitude limit.
- ID:
- ivo://CDS.VizieR/J/ApJS/216/20
- Title:
- Blanco Cosmology Survey (BCS) new reduction
- Short Name:
- J/ApJS/216/20
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Blanco Cosmology Survey is a four-band (griz) optical-imaging survey of ~80deg^2^ of the southern sky. The survey consists of two fields centered approximately at (RA,DE)=(23h,-55{deg}) and (5h30m,-53{deg}) with imaging sufficient for the detection of L_*_ galaxies at redshift z<=1. In this paper, we present our reduction of the survey data and describe a new technique for the separation of stars and galaxies. We search the calibrated source catalogs for galaxy clusters at z<=0.75 by identifying spatial over-densities of red-sequence galaxies and report the coordinates, redshifts, and optical richnesses, {lambda}, for 764 galaxy clusters at z<=0.75. This sample, >85% of which are new discoveries, has a median redshift of z=0.52 and median richness {lambda}(0.4L_*_)=16.4.
- ID:
- ivo://CDS.VizieR/J/ApJ/742/48
- Title:
- Blanco survey of the lens BCS J2352-5452
- Short Name:
- J/ApJ/742/48
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report on the serendipitous discovery in the Blanco Cosmology Survey (BCS) imaging data of a z=0.9057 galaxy that is being strongly lensed by a massive galaxy cluster at a redshift of z=0.3838. The lens (BCS J2352-5452) was discovered while examining i- and z-band images being acquired in 2006 October during a BCS observing run. Follow-up spectroscopic observations with the Gemini Multi-Object Spectrograph instrument on the Gemini-South 8m telescope confirmed the lensing nature of this system. Using weak-plus-strong lensing, velocity dispersion, cluster richness N_200_, and fitting to a Navarro-Frenk-White (NFW) cluster mass density profile, we have made three independent estimates of the mass M_200_ which are all very consistent with each other. The combination of the results from the three methods gives M_200_=(5.1+/-1.3)x10^14^M_{sun}_, which is fully consistent with the individual measurements. The final NFW concentration c_200_ from the combined fit is c_200_=5.4^+1.4^_-1.1_. We have compared our measurements of M_200_ and c_200_ with predictions for (1) clusters from {Lambda}CDM simulations, (2) lensing-selected clusters from simulations, and (3) a real sample of cluster lenses.
- ID:
- ivo://CDS.VizieR/J/ApJ/867/131
- Title:
- Blazar candidates behind the Magellanic Clouds
- Short Name:
- J/ApJ/867/131
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the identification of blazar candidates behind the Magellanic Clouds. The objects were selected from the Magellanic Quasars Survey (MQS), which targeted the entire Large Magellanic Cloud (LMC) and 70% of the Small Magellanic Cloud (SMC). Among the 758 MQS quasars and 898 of the unidentified (featureless spectra) objects, we identified a sample of 44 blazar candidates, including 27 flat-spectrum radio quasars and 17 BL Lacertae objects, respectively. All the blazar candidates from our sample were identified with respect to their radio, optical, and midinfrared properties. The newly selected blazar candidates possess the long-term, multicolor photometric data from the Optical Gravitational Lensing Experiment, multicolor midinfrared observations, and archival radio data for one frequency at least. In addition, for nine of them, the radio polarization data are available. With such data, these objects can be used to study the physics behind the blazar variability detected in the optical and midinfrared bands, as a tool to investigate magnetic field geometry of the LMC and SMC, and as an exemplary sample of point-like sources most likely detectable in the {gamma}-ray range with the newly emerging Cherenkov Telescope Array.