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We use Wide-field Infrared Survey Explorer (WISE) data covering the entire region (~130 deg^2) of the A2199 supercluster at z=0.03 to study the mid-infrared (MIR) properties of supercluster galaxies. We identify a `MIR star-forming sequence in the WISE [3.4]-[12] color-12 mu m luminosity diagram, consisting of late-type, star-forming galaxies. At a fixed star formation rate (SFR), the MIR-detected galaxies at 22 mu m or 12 mu m tend to be more metal rich and to have higher surface brightness than those without MIR detection. Using these MIR-detected galaxies, we construct the IR luminosity function (LF) and investigate its environmental dependence. Both total IR (TIR) and 12 mu m LFs are dominated by late-type, star-forming galaxies. The contribution of active galactic nuclei (AGN)-host galaxies increases with both TIR and 12 mu m luminosities. The contribution of early-type galaxies to the 12 mu m LFs increases with decreasing luminosity. The faint-end slope of the TIR LFs does not change with environment, but the change of faint-end slope in the 12 mu m LFs with the environment is significant: there is a steeper faint-end slope in the cluster core than in the cluster outskirts. This steepening results primarily from the increasing contribution of early-type galaxies toward the cluster. These galaxies are passively evolving, and contain old stellar populations with weak MIR emission from the circumstellar dust around asymptotic giant branch stars.
We present the result of trawling through the WISE archive for data on classical and recurrent novae. The data show a variety of spectral energy distributions, including stellar photospheres, dust and probable line emission. During the mission WISE also detected some novae which erupted subsequent to the survey, providing information about the progenitor systems.
We present the results of data-mining the Wide-field Infrared Survey Explorer (WISE) archive for data on classical and recurrent novae. We find that the detections are consistent with dust emission, line emission, emission by a stellar photosphere, or a combination of these. Of the 36 novae detected in one or more WISE bands, 16 are detected in all four; thirty-one known novae are not detected by WISE. We also searched for WISE data on post-WISE novae, to gain information about nova progenitors. In this first paper we consider only the WISE data. In future papers we will provide a more detailed modelling of the WISE data, and discuss WISE data on post-WISE novae - including their variability - and will complement the WISE data with data from other IR surveys.
Using data from the Sloan Digital Sky Survey we assess the current dynamical state of the Corona Borealis Supercluster (CSC), a highly dense and compact supercluster at z = 0.07. The Fundamental Plane relation is used to determine redshift independent distances to six clusters in the densest region of the supercluster, with mean accuracy in the relative distance estimates of 4 per cent. Peculiar velocities determined from these distance estimates indicate that the clusters have broken from the Hubble Flow, suggesting that the CSC likely contains two regions that have reached turnaround and are currently undergoing gravitational collapse. These results provide the strongest observational evidence to date that the CSC is a bound system similar to the much more extensive Shapley Supercluster, which is the most extensive confirmed bound supercluster yet identified in the Universe. When compared with simulations of the CSC our results require substantially more mass than is contained within the clusters, possibly indicating a significant inter-cluster dark matter component. In order to facilitate comparison with studies for which spectroscopic data are not available, an alternative analysis of the dynamics is made using the Kormendy relation as a distance indicator. The results are generally consistent with those of the Fundamental Plane and suggest similar global dynamics, but we find that the relatively sparse sampling of the clusters makes the Kormendy relation less reliable overall and more susceptible to small systematic differences between the cluster samples.
We use the SDSS and WISE surveys to investigate the real nature of galaxies defined as LINERs in the BPT diagram. After establishing a mid-infrared colour W2-W3 = 2.5 as the optimal separator between galaxies with and without star formation, we investigate the loci of different galaxy classes in the W_{Ha} versus W2-W3 space. We find that: (1) A large fraction of LINER-like galaxies are emission-line retired galaxies, i.e galaxies which have stopped forming stars and are powered by hot low-mass evolved stars (HOLMES). Their W2-W3 colours show no sign of star formation and their Ha equivalent widths, W_{Ha}, are consistent with ionization by their old stellar populations. (2) Another important fraction have W2-W3 indicative of star formation. This includes objects located in the supposedly `pure AGN zone of the BPT diagram. (3) A smaller fraction of LINER-like galaxies have no trace of star formation from W2-W3 and a high W_{Ha}, pointing to the presence of an AGN. (4) Finally, a few LINERs tagged as retired by their W_{Ha} but with W2-W3 values indicative of star formation are late-type galaxies whose SDSS spectra cover only the old `retired bulge. This reinforces the view that LINER-like galaxies are a mixed bag of objects involving different physical phenomena and observational effects thrusted into the same locus of the BPT diagram.
We report a promising candidate for a distant supercluster at z $sim 1.1$ in the Dark Energy Survey Science Verification data. We examine smoothed semi-3D galaxy density maps in various photo-z slices. Among several overdense regions, in this work we report the most significant one as having a $3sigma$ overdensity at a redshift of $sim1.1$, over a $sim160$ Mpc scale, much larger than the regular cluster scale (several Mpc). The shape of the supercluster is not circular in the sky projection. Therefore, we regard the point of maximum overdensity as the center for quantitative measurements. Two different estimates suggest the mass of the supercluster to be $1.37substack{+1.31 -0.79} times 10^{17} M_{odot}$, more than one order more massive than regular galaxy clusters. Except for protosuperclusters found with emission-line galaxies, this could be the most distant supercluster to date defined by regular galaxies. A spectroscopic confirmation would make this a very interesting object for cosmology. We discuss the possible implications of such a massive structure for $Lambda$CDM cosmology.