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4971. Photometric properties of galaxies at z=4-6
ID:
ivo://CDS.VizieR/J/ApJ/704/548
Title:
Photometric properties of galaxies at z=4-6
Short Name:
J/ApJ/704/548
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present new information on galaxies in the vicinity of luminous radio galaxies (RGs) and quasars at z~4, 5, and 6. These fields were previously found to contain overdensities of Lyman Break Galaxies (LBGs) or spectroscopic Ly{alpha} emitters (LAEs), which were interpreted as evidence for clusters-in-formation ("protoclusters"). We use Hubble Space Telescope and Spitzer data to infer stellar masses from stellar synthesis models calibrated against the Millennium Run simulations, and contrast our results with large samples of LBGs in more average environments as probed by the Great Observatories Origins Deep Survey (GOODS).
4972. Photometric quasar candidates in Stripe 82
ID:
ivo://CDS.VizieR/J/A+A/611/A97
Title:
Photometric quasar candidates in Stripe 82
Short Name:
J/A+A/611/A97
Date:
21 Oct 2021
Publisher:
CDS
Description:
We have applied a convolutional neural network (CNN) to classify and detect quasars in the Sloan Digital Sky Survey Stripe 82 and also to predict the photometric redshifts of quasars. The network takes the variability of objects into account by converting light curves into images. The width of the images, noted w, corresponds to the five magnitudes ugriz and the height of the images, noted h, represents the date of the observation. The CNN provides good results since its precision is 0.988 for a recall of 0.90, compared to a precision of 0.985 for the same recall with a random forest classifier. Moreover 175 new quasar candidates are found with the CNN considering a fixed recall of 0.97. The combination of probabilities given by the CNN and the random forest makes good performance even better with a precision of 0.99 for a recall of 0.90. For the redshift predictions, the CNN presents excellent results which are higher than those obtained with a feature extraction step and different classifiers (a K-nearest-neighbors, a support vector machine, a random forest and a Gaussian process classifier). Indeed, the accuracy of the CNN within |{DELTA}z|<0.1 can reach 78.09%, within |{DELTA}z|<0.2 reaches 86.15%, within |{DELTA}z|<0.3 reaches 91.2% and the value of root mean square (rms) is 0.359. The performance of the KNN decreases for the three |{DELTA}z| regions, since within the accuracy of |{DELTA}z|<0.1, |{DELTA}z|<0.2, and |{DELTA}z|<0.3 is 73.72%, 82.46%, and 90.09% respectively, and the value of rms amounts to 0.395. So the CNN successfully reduces the dispersion and the catastrophic redshifts of quasars. This new method is very promising for the future of big databases such as the Large Synoptic Survey Telescope.
4973. Photometric redshift catalog from the RCS
ID:
ivo://CDS.VizieR/J/ApJS/158/161
Title:
Photometric redshift catalog from the RCS
Short Name:
J/ApJS/158/161
Date:
21 Oct 2021
Publisher:
CDS
Description:
The Red-Sequence Cluster Survey (RCS, Cat. <J/ApJS/157/1>) provides a large and deep photometric catalog of galaxies in the z' and R_c_ bands for 90{deg}^2^ of sky, and supplemental V and B data have been obtained for 33.6{deg}^2^. We compile a photometric redshift catalog from these four-band data by utilizing the empirical quadratic polynomial photometric redshift fitting technique in combination with CNOC2 and GOODS/HDF-N redshift data. The training set includes 4924 spectral redshifts. The resulting catalog contains more than one million galaxies with photometric redshifts <1.5 and R_c_<24, giving an rms scatter {sigma}({Delta}z)<0.06 within the redshift range 0.2<z<0.5 and {sigma}({Delta}z)<0.11 for galaxies at 0.0<z<1.5.
4974. Photometric Redshift Catalog (SCUSS, SDSS, WISE)
ID:
ivo://CDS.VizieR/J/ApJ/862/12
Title:
Photometric Redshift Catalog (SCUSS, SDSS, WISE)
Short Name:
J/ApJ/862/12
Date:
21 Oct 2021
Publisher:
CDS
Description:
We publish a photometric redshift catalog based on imaging data of the South Galactic Cap u-band Sky Survey, Sloan Digital Sky Survey (SDSS), and Wide-field Infrared Survey Explorer (WISE). A total of 7 photometric bands are used, ranging from near ultraviolet to near infrared. A local linear regression method is adopted to estimate the photometric redshift with a dedicated spectroscopic training set. The photometric redshift catalog contains about 23.1 million galaxies classified by SDSS. Using the training set with redshift up to 0.8 and r-band magnitude down to 22mag, we achieve an average bias of {Delta}z_norm_=0.000228, standard deviation of {sigma}({Delta}z_norm_)=0.019, and 3{sigma} outlier rate of about 4.2%. The bias is less than 0.01 at z<0.6 and goes up to about 0.05 at z~0.8. Compared with SDSS photometric redshifts, our redshift estimations are more accurate and have less bias.
4975. Photometric redshifts in the EGOODS-North field
ID:
ivo://CDS.VizieR/J/ApJ/871/233
Title:
Photometric redshifts in the EGOODS-North field
Short Name:
J/ApJ/871/233
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present deep J- and H-band images in the extended Great Observatories Origins Deep Survey-North field covering an area of 0.22deg^2^. The observations were taken using WIRCam on the 3.6m Canada-France-Hawaii Telescope. Together with the reprocessed Ks-band image, the 5{sigma} limiting AB magnitudes (in 2" diameter apertures) are 24.7, 24.2, and 24.4 AB mag in the J, H, and Ks bands, respectively. We also release a multiband photometry and photometric redshift catalog containing 93598 sources. For non-X-ray sources, we obtained a photometric redshift accuracy {sigma}_NMAD_=0.036 with an outlier fraction {eta}=7.3%. For X-ray sources, which are mainly active galactic nuclei (AGNs), we cross-matched our catalog with the updated 2M-CDFN X-ray catalog from Xue+ (2016, J/ApJS/224/15) and found that 658 out of 683 X-ray sources have counterparts. GALEX UV data are included in the photometric redshift computation for the X-ray sources to give {sigma}_NMAD_=0.040 with {eta}=10.5%. Our approach yields more accurate photometric redshift estimates compared to previous works in this field. In particular, by adopting AGN-galaxy hybrid templates, our approach delivers photometric redshifts for the X-ray counterparts with fewer outliers compared to the 3D-Hubble Space Telescope catalog, which fit these sources with galaxy-only templates.
4976. Photometric redshifts in the Hawaii-HDF-N
ID:
ivo://CDS.VizieR/J/ApJS/215/27
Title:
Photometric redshifts in the Hawaii-HDF-N
Short Name:
J/ApJS/215/27
Date:
21 Oct 2021
Publisher:
CDS
Description:
We derive photometric redshifts (z_phot_) for sources in the entire (~0.4deg^2^) Hawaii-Hubble Deep Field-North (H-HDF-N) field with the EAzY code, based on point-spread-function-matched photometry of 15 broad bands from the ultraviolet (U band) to mid-infrared (IRAC 4.5{mu}m). Our catalog consists of a total of 131678 sources. We evaluate the z_phot_ quality by comparing z_phot_with spectroscopic redshifts (z_spec_) when available, and find a value of normalized median absolute deviation {sigma}_NMAD_=0.029 and an outlier fraction of 5.5% (outliers are defined as sources having |z_phot_-z_spec_|/(1+z_spec_)>0.15) for non-X-ray sources. More specifically, we obtain {sigma}_NMAD_=0.024 with 2.7% outliers for sources brighter than R=23mag, {sigma}_NMAD_=0.035 with 7.4% outliers for sources fainter than R=23mag, {sigma}_NMAD_=0.026 with 3.9% outliers for sources having z<1, and {sigma}_NMAD_=0.034 with 9.0% outliers for sources having z>1. Our z_phot_ quality shows an overall improvement over an earlier z_phot_ work that focused only on the central H-HDF-N area. We also classify each object as a star or galaxy through template spectral energy distribution fitting and complementary morphological parameterization, resulting in 4959 stars and 126719 galaxies. Furthermore, we match our catalog with the 2Ms Chandra Deep Field-North main X-ray catalog. For the 462 matched non-stellar X-ray sources (281 having z_spec_), we improve their z_phot_ quality by adding three additional active galactic nucleus templates, achieving {sigma}_NMAD_=0.035 and an outlier fraction of 12.5%.
4977. Photometric redshifts of emission-line galaxies
ID:
ivo://CDS.VizieR/J/AJ/157/99
Title:
Photometric redshifts of emission-line galaxies
Short Name:
J/AJ/157/99
Date:
21 Oct 2021
Publisher:
CDS
Description:
Broadband photometric redshifts are routinely obtained for galaxies to estimate their distances. While effective for many uses, the common resolution in z of 0.01-0.02 is too coarse for detailed large-scale structure mapping, particularly in low-density volumes where the galaxy distribution is least understood. To map galaxies in these low-density volumes, and noting that the percentage of galaxies having emission tends to rise as number density decreases, we have designed a filter system to photometrically measure the redshifts of galaxies with emission. The system consists of two "ramp" filters that cover a common wavelength range with transmission curves sloping from blue to red and from red to blue respectively. This causes the intensity of the image through either filter to be a function of the wavelength of the emission line. A third filter with a bandpass to the side is used to measure and remove the continuum. We have obtained a set of such filters that are tuned for isolating H{alpha} in the redshift range of 3000-9000 km/s. Simulated photometry, applied to spectra of 197 emission-line galaxies from the SDSS, shows the accuracy of the method to be between 250 and 620 km/s, depending on line strength. Actual photometry of a sample of 16 active galaxies measured their redshifts with an accuracy of 573 km/s. This is approximately an order of magnitude more accurate than broadband photometric redshifts. We discuss the errors inherent in this method and present ways to modify the filter set to further improve accuracy.
4978. Photometric redshifts of the 2Ms CDF-S
ID:
ivo://CDS.VizieR/J/ApJS/187/560
Title:
Photometric redshifts of the 2Ms CDF-S
Short Name:
J/ApJS/187/560
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present reliable multiwavelength identifications and high-quality photometric redshifts for the 462 X-ray sources in the ~2Ms Chandra Deep Field-South (CDF-S) survey (Cat. J/ApJS/179/19). Source identifications are carried out using deep optical-to-radio multiwavelength catalogs, and are then combined to create lists of primary and secondary counterparts for the X-ray sources. We identified reliable counterparts for 442 (95.7%) of the X-ray sources, with an expected false-match probability of ~6.2%; we also selected four additional likely counterparts. The majority of the other 16 X-ray sources appear to be off-nuclear sources, sources associated with galaxy groups and clusters, high-redshift active galactic nuclei (AGNs), or spurious X-ray sources. A likelihood-ratio method is used for source matching, which effectively reduces the false-match probability at faint magnitudes compared to a simple error-circle matching method. We construct a master photometric catalog for the identified X-ray sources including up to 42 bands of UV-to-infrared data, and then calculate their photometric redshifts (photo-z's). The typical photo-z accuracy is ~6%-7%.
4979. Photometric scaling for L/S0 galaxies
ID:
ivo://CDS.VizieR/J/MNRAS/405/1089
Title:
Photometric scaling for L/S0 galaxies
Short Name:
J/MNRAS/405/1089
Date:
21 Oct 2021
Publisher:
CDS
Description:
Photometric scaling relations are studied for S0 galaxies and compared with those obtained for spirals. New two-dimensional multi-component decompositions are presented for 122 early-type disc galaxies, using deep Ks-band images. Combining them with our previous decompositions, the final sample consists of 175 galaxies (Near-Infrared Survey of S0s, NIRS0S: 117 S0s + 22 S0/a and 36 Sa galaxies). As a comparison sample we use the Ohio State University Bright Spiral Galaxy Survey (OSUBSGS) of nearly 200 spirals, for which similar multi-component decompositions have previously been made by us.
4980. Photometric search for transients in galaxy clusters
ID:
ivo://CDS.VizieR/J/AJ/135/1917
Title:
Photometric search for transients in galaxy clusters
Short Name:
J/AJ/135/1917
Date:
21 Oct 2021
Publisher:
CDS
Description:
We have begun a program to search for supernovae and other transients in the fields of galaxy clusters with the 2.3m Bok Telescope on Kitt Peak. We present our automated photometric methods for data reduction, efficiency characterization, and initial spectroscopy. With this program, we aim to ultimately identify ~25-35 cluster Type Ia supernovae (SNe Ia) (~10 of which will be intracluster, hostless events) and constrain the SN Ia rate associated with old, passive stellar populations. With these measurements we will constrain the relative contribution of hostless and hosted SNe Ia to the metal enrichment of the intracluster medium.