A GMBCG Galaxy Cluster Catalog of 55,424 Rich Clusters from SDSS DR7
TL;DR: In this paper, the authors presented a large catalog of optically selected galaxy clusters from the application of a new Gaussian Mixture Brightest Cluster Galaxy (GMBCG) algorithm to SDSS Data Release 7 data.
Abstract: We present a large catalog of optically selected galaxy clusters from the application of a new Gaussian Mixture Brightest Cluster Galaxy (GMBCG) algorithm to SDSS Data Release 7 data. The algorithm detects clusters by identifying the red sequence plus Brightest Cluster Galaxy (BCG) feature, which is unique for galaxy clusters and does not exist among field galaxies. Red sequence clustering in color space is detected using an Error Corrected Gaussian Mixture Model. We run GMBCG on 8240 square degrees of photometric data from SDSS DR7 to assemble the largest ever optical galaxy cluster catalog, consisting of over 55,000 rich clusters across the redshift range from 0.1 < z < 0.55. We present Monte Carlo tests of completeness and purity and perform cross-matching with X-ray clusters and with the maxBCG sample at low redshift. These tests indicate high completeness and purity across the full redshift range for clusters with 15 or more members.
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TL;DR: In this article , a catalog of 717 new head-tail (HT) radio sources is presented, among which 287 are narrow-angle tail (NAT) sources whose opening angle between the two lobes is less than 90°, and 430 are wide-angle tails (WATs) whose the opening angle is greater than 90 degrees.
Abstract: The head–tail (HT) morphology of radio galaxies is seen for a class of radio sources where the primary lobes are being bent in the intercluster weather due to strong interactions between the radio jets and their respective intracluster medium. A systematic search has been carried out for new HT radio galaxies from the Very Large Array Faint Images of the Radio Sky at Twenty-Centimeters survey database at 1400 MHz. Here, we present a catalog of 717 new HT sources, among which 287 are narrow-angle tail (NAT) sources whose opening angle between the two lobes is less than 90°, and 430 are wide-angle tail (WAT) whose the opening angle between the two lobes is greater than 90°. NAT radio sources are characterized by tails bent in a narrow “V”-like shape; the jet bending in the case of WAT radio galaxies are such that the WATs exhibit wide “C”-like morphologies. Optical counterparts are found for 359 HT sources. We report HT sources with luminosity ranges 1038 ≤ L 1.4 GHz ≤ 1045 erg s−1 and redshifts up to 2.01. The various physical properties of these HT sources are mentioned here. Some statistical studies have been done for this large number of newly discovered HT sources.
7 citations
TL;DR: In this article , the authors compare X-ray hydrostatic masses with masses estimated using the caustic method (based on galaxy velocities) in order to explore the systematic uncertainties of both methods and place new constraints on the level of hydrostatic bias.
Abstract: Context. Clusters of galaxies are powerful probes with which to study cosmology and astrophysics. However, for many applications, an accurate measurement of a cluster’s mass is essential. A systematic underestimate of hydrostatic masses from X-ray observations (the so-called hydrostatic bias) may be responsible for tension between the results of di ff erent cosmological measurements. Aims. We compare X-ray hydrostatic masses with masses estimated using the caustic method (based on galaxy velocities) in order to explore the systematic uncertainties of both methods and place new constraints on the level of hydrostatic bias. Methods. Hydrostatic and caustic mass profiles were determined independently for a sample of 44 clusters based on Chandra obser- vations of clusters from the Hectospec Cluster Survey. This is the largest systematic comparison of its kind. Masses were compared at a standardised radius ( R 500 ) using a model that includes possible bias and scatter in both mass estimates. The systematics a ff ecting both mass determination methods were explored in detail. Results. The hydrostatic masses were found to be systematically higher than caustic masses on average, and we found evidence that the caustic method increasingly underestimates the mass when fewer galaxies are used to measure the caustics. We limit our analysis to the 14 clusters with the best-sampled caustics where this bias is minimised ( ≥ 210 galaxies), and find that the average ratio of hydrostatic-to-caustic mass at R 500 is M 500 , X / M 500 , C = 1 . 12 + 0 . 11 − 0 . 10 . Conclusions. We interpret this result as a constraint on the level of hydrostatic bias, favouring small or zero levels of hydrostatic bias (less than 20% at the 3 σ level). However, we find that systematic uncertainties associated with both mass estimation methods remain at the 10 − 15% level, which would permit significantly larger levels of hydrostatic bias.
4 citations
TL;DR: In this paper , an early-type galaxy at z = 1.0153 ± 0.0006, strongly lensed by a cluster of galaxies at 0.353 − 0.001, is presented.
Abstract: We present COOL J1323+0343, an early-type galaxy at z = 1.0153 ± 0.0006, strongly lensed by a cluster of galaxies at z = 0.353 ± 0.001. This object was originally imaged by DECaLS and noted as a gravitational lens by COOL-LAMPS, a collaboration initiated to find strong-lensing systems in recent public optical imaging data, and confirmed with follow-up data. With ground-based grzH imaging and optical spectroscopy from the Las Campanas Observatory and the Nordic Optical Telescope, we derive a stellar mass, metallicity, and star formation history from stellar-population synthesis modeling. The lens modeling implies a total magnification, summed over the three images in the arc, of μ ∼ 113. The stellar mass in the source plane is M * ∼ 10.64 M ⊙ and the 1σ upper limit on the star formation rate (SFR) in the source plane is SFR ∼ 3.75 × 10−2 M ⊙ yr−1 (log sSFR = −12.1 yr−1) in the youngest two age bins (0–100 Myr), closest to the epoch of observation. Our measurements place COOL J1323+0343 below the characteristic mass of the stellar mass function, making it an especially compelling target that could help clarify how intermediate-mass quiescent galaxies evolve. We reconstruct COOL J1323+0343 in the source plane and fit its light profile. This object is below the expected size evolution of an early-type galaxy at this mass with an effective radius r e ∼ 0.5 kpc. This extraordinarily magnified and bright lensed early-type galaxy offers an exciting opportunity to study the morphology and star formation history of an intermediate-mass early-type galaxy in detail at z ∼ 1.
4 citations
TL;DR: In this paper , the authors extend their previous work on estimating photoz and detecting galaxy clusters to the latest data releases of the DESI imaging surveys, Dark Energy Survey (DES) and Hyper Suprime-Cam Subaru Strategic Program (HSC-SSP) imaging surveys and make corresponding catalogs publicly available for more extensive scientific applications.
Abstract: Photometric redshift (photoz) is a fundamental parameter for multi-wavelength photometric surveys, while galaxy clusters are important cosmological probes and ideal objects for exploring the dense environmental impact on galaxy evolution. We extend our previous work on estimating photoz and detecting galaxy clusters to the latest data releases of the Dark Energy Spectroscopic Instrument (DESI) imaging surveys, Dark Energy Survey (DES) and Hyper Suprime-Cam Subaru Strategic Program (HSC-SSP) imaging surveys and make corresponding catalogs publicly available for more extensive scientific applications. The photoz catalogs include accurate measurements of photoz and stellar mass for about 320, 293 and 134 million galaxies with r < 23, i < 24 and i < 25 in DESI DR9, DES DR2 and HSC-SSP PDR3 data, respectively. The photoz accuracy is about 0.017, 0.024 and 0.029 and the general redshift coverage is z < 1, z < 1.2 and z < 1.6, respectively for those three surveys. The uncertainty of the logarithmic stellar mass that is inferred from stellar population synthesis fitting is about 0.2 dex. With the above photoz catalogs, galaxy clusters are detected using a fast cluster-finding algorithm. A total of 532,810, 86,963 and 36,566 galaxy clusters with the number of members larger than 10 is discovered for DESI, DES and HSC-SSP, respectively. Their photoz accuracy is at the level of 0.01. The total mass of our clusters is also estimated by using the calibration relations between the optical richness and the mass measurement from X-ray and radio observations. The photoz and cluster catalogs are available at ScienceDB (https://www.doi.org/10.11922/sciencedb.o00069.00003) and PaperData Repository (https://doi.org/10.12149/101089).
2 citations
TL;DR: In this article , a sample of radio-galaxies and AGN was selected by cross-matching the low radio frequency sources from VLA First with spectroscopically confirmed sources from wide field surveys including SDSS DR14 ugriz and DES DR2 grzY in optical, WISE in infrared, and the Galaxy And Mass Assembly (GAMA) spectroscopic survey.
Abstract: There exists a well known relation between the mass of the supermassive black hole (SMBH) in the center of galaxies and their bulge mass or central velocity dispersion. This suggests a co-evolution between SMBH and their galaxy hosts. Our aim is to study this relation specifically for radio loud galaxies, and as a function of redshift $z$. We selected a sample of radio-galaxies and AGN by cross-matching the low radio frequency sources from VLA FIRST with spectroscopically confirmed sources from wide field surveys including SDSS DR14 ugriz and DES DR2 grzY in optical, WISE in infrared, and the Galaxy And Mass Assembly (GAMA) spectroscopic survey. Keeping only high signal to noise (S/N) sources in WISE magnitudes, and those with broad emission lines, we selected a sub sample of 42 radio sources, all with infrared-to-optical counterparts, for which we characterized the stellar, star formation, and black hole properties. We estimated the central SMBH mass, the stellar mass $M_\star$, the Eddington ratio $\eta$ and the jet power, $Q_{\rm jet}$. The relation between SMBH mass, $M_\star$, $\eta$ and $z$ are put into context by comparing them with scaling relations ($M_{\rm BH}$--$M_{\star}$, $M_{\rm BH}/M_\star$--$z$, $M_{\rm BH}$--$Q_{\rm jet}$ and $Q_{\rm jet}$--$\eta$) from the literature. An evolutionary scenario where radio-mode AGN feedback (or the cluster environments) regulate the accretion onto the SMBHs and the stellar mass assembly of the radio sources is discussed, which may explain the observed phenomenology, and in particular the presence of radio sources with high $M_{\rm BH}/M_\star$ ratios. This pilot study represents a benchmark for future ones using wide field surveys such as Euclid and the Vera Rubin telescope.
2 citations