A large number of luminous infrared galaxies in the massive cluster Cl 0024+ 1654 (original) (raw)
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An Infrared Survey of Brightest Cluster Galaxies. I.
The Astrophysical …, 2008
We report on an imaging survey with the Spitzer Space Telescope of 62 brightest cluster galaxies with optical line emission. These galaxies are located in the cores of X-ray luminous clusters selected from the ROSAT All-Sky Survey. We find that about half of these sources have a sign of excess infrared emission; 22 objects out of 62 are detected at 70 m, 18 have 8/5.8 m flux ratios above 1.0 and 28 have 24/8 m flux ratios above 1.0. Altogether 35 of 62 objects in our survey exhibit at least one of these signs of infrared excess. Four galaxies with infrared excesses have a 4.5/3.6 m flux ratio indicating the presence of hot dust, and/or an unresolved nucleus at 8 m. Three of these have high measured [O iii](5007 8)/H flux ratios suggesting that these four, Abell 1068, Abell 2146, Zwicky 2089, and R0821+07, host dusty active galactic nuclei (AGNs). Nine objects (including the four hosting dusty AGNs) have infrared luminosities greater than 10 11 L and so can be classified as luminous infrared galaxies (LIRGs). Excluding the four systems hosting dusty AGNs, the excess mid-infrared emission in the remaining brightest cluster galaxies is likely related to star formation.
The Astrophysical …, 2008
presented an imaging survey with the Spitzer Space Telescope of 62 brightest cluster galaxies with optical line emission located in the cores of X-ray luminous clusters. They found that at least half of these sources have signs of excess infrared emission. Here we discuss the nature of the IR emission and its implications for cool core clusters. The strength of the mid-IR excess emission correlates with the luminosity of the optical emission lines. Excluding the four systems dominated by an AGN, the excess mid-infrared emission in the remaining brightest cluster galaxies is likely related to star formation. The mass of molecular gas (estimated from CO observations) is correlated with the IR luminosity as found for normal star forming galaxies. The gas depletion time scale is about 1 Gyr. The physical extent of the infrared excess is consistent with that of the optical emission line nebulae. This supports the hypothesis that the star formation occurs in molecular gas associated with the emission line nebulae and with evidence that the emission line nebulae are mainly powered by ongoing star
Clusters of galaxies in the mid-infrared
2004
We describe the results of observations of galaxy clusters conducted with ISOCAM on-board the Infrared Space Observatory. Our research is aimed at understanding the processes driving galaxy evolution in dense environments, free from the bias of dust extinction. The results reveal quite a complex picture: the star-formation activity of cluster galaxies does not show a simple evolution with redshift, but also depends on the dynamical status and evolutionary history of the clusters.
A panoramic mid-infrared survey of two distant clusters
2006
We present panoramic Spitzer MIPS 24-µm observations covering ∼9×9 Mpc (25 ′ × 25 ′ ) fields around two massive clusters, Cl 0024+16 and MS 0451−03, at z = 0.39 and z = 0.55 respectively, reaching a 5-σ flux limit of ∼ 200µJy. Our observations cover a very wide range of environments within these clusters, from high-density regions around the cores out to the turn-around radius. Cross-correlating the mid-infrared catalogs with deep optical and near-infrared imaging of these fields, we investigate the optical/near-infrared colors of the mid-infrared sources. We find excesses of mid-infrared sources with optical/near-infrared colors expected of cluster members in the two clusters and test this selection using spectroscopically confirmed 24µm members. The much more significant excess is associated with Cl 0024+16, whereas MS 0451−03 has comparatively few mid-infrared sources. The mid-infrared galaxy population in Cl 0024+16 appears to be associated with dusty star-forming galaxies (typically redder than the general cluster population by up to A V ∼ 1-2 mags) rather than emission from dusty tori around active galactic nuclei (AGN) in early-type hosts. We compare the star-formation rates derived from the total infrared (8-1000µm) luminosities for the mid-infrared sources in Cl 0024+16 with those estimated from a published Hα survey, finding rates > ∼ 5× than those found from Hα, indicating significant obscured activity in the cluster population. Compared to previous mid-infrared surveys of clusters from z ∼ 0-0.5, we find evidence for strong evolution of the level of dust-obscured star-formation in dense environments to z = 0.5, analogous to the rise in fraction of optically-selected star-forming galaxies seen in clusters and the field out to similar redshifts. However, there are clearly significant cluster-to-cluster variations in the populations of mid-infrared sources, probably reflecting differences in the intracluster media and recent dynamical evolution of these systems.
ISO Far-Infrared Observations of Rich Galaxy Clusters. I. Abell 2670
Astronomy and …, 1999
As part of an investigation of far-infrared emission from rich galaxy clusters the central part of Abell 2670 has been mapped with ISO at 60 µm, 100 µm, 135 µm, and 200 µm using the PHT-C camera. Point sources detected in the field have infrared fluxes comparable to normal spirals at the cluster distance. Probable optical counterparts are cluster galaxies with various characteristics such as blue colour, Hα emission, or double nuclei. One source is extended which could possibly be emission from intracluster dust in debris from spiral galaxies.
LoCuSS: luminous infrared galaxies in the merging cluster Abell 1758 at z = 0.28
Monthly Notices of the Royal Astronomical Society, 2009
We present the first galaxy evolution results from the Local Cluster Substructure Survey (Lo-CuSS), a multi-wavelength survey of 100 X-ray selected galaxy clusters at 0.15 z 0.3. Lo-CuSS combines far-UV through far-IR observations of cluster galaxies with gravitational lensing analysis and X-ray data to investigate the interplay between the hierarchical assembly of clusters and the evolution of cluster galaxies. Here we present new panoramic Spitzer/MIPS 24µm observations of the merging cluster Abell 1758 at z=0.279 spanning 6.5×6.5 Mpc and reaching a 90% completeness limit of S 24µm =400µJy. We estimate a global cluster star-formation rate of SFR 24µm =910±320 M ⊙ yr −1 within R<3 Mpc of the cluster centre, originating from 42 galaxies with L 8−1000µm >5×10 10 L ⊙. The obscured activity in A 1758 is therefore comparable with that in Cl 0024+1654, the most active cluster previously studied at 24µm. The obscured galaxies faithfully trace the cluster potential as revealed by the weak-lensing mass map of the cluster, including numerous mass peaks at R∼2-3 Mpcthat are likely associated with infalling galaxy groups and filamentary structures. However the core (R ∼ <500 kpc) of A 1758N is ∼2× more active in the infrared than that of A 1758S, likely reflecting differences in the recent dynamical history of the two clusters. The 24µm results from A 1758 therefore suggest that dust-obscured cluster galaxies are common in merging clusters and suggests that obscured activity in clusters is triggered by both the details of cluster-cluster mergers and processes that operate at larger radii including those within in-falling groups. Our ongoing far-UV through far-IR observations of a large sample of clusters should allow us to disentangle the different physical processes responsible for triggering obscured star formation in clusters.
A wide-field spectroscopic survey of the cluster of galaxies Cl0024+1654
Astronomy and Astrophysics, 2001
We present the catalogue of a wide-field CFHT/WHT spectroscopic survey of the lensing cluster Cl0024+1654 at z = 0.395. This catalogue contains 618 new spectra, of which 581 have identified redshifts. Adding redshifts available from the literature, the final catalogue contains data for 687 objects with redshifts identified for 650 of them. 295 galaxies have redshifts in the range 0.37 < z < 0.41, i. e. are cluster members or lie in the immediate neighbourhood of the cluster. The area covered by the survey is 21×25 arcmin 2 in size, corresponding to 4 × 4.8 h −2 Mpc 2 at the cluster redshift. The survey is 45% complete down to V = 22 over the whole field covered; within 3 arcmin of the cluster centre the completeness exceeds 80% at the same magnitude. A detailed completeness analysis is presented. The catalogue gives astrometric position, redshift, V magnitude and V −I colour, as well as the equivalent widths for a number of lines. Apart from the cluster Cl0024+1654 itself, three other structures are identified in redshift space: a group of galaxies at z = 0.38, just in front of Cl0024+1654 and probably interacting with it, a close pair of groups of galaxies at z ∼ 0.495 and an overdensity of galaxies at z ∼ 0.18 with no obvious centre. The spectroscopic catalogue will be used to trace the three-dimensional structure of the cluster Cl0024+1654 as well as study the physical properties of the galaxies in the cluster and in its environment.
Astronomy and Astrophysics, 2005
The massive cluster of galaxies Abell 2219 (z = 0.228) with two spectacular gravitational lensing arcs was observed at 14.3 µm (hereafter 15 µm) with the Infrared Space Observatory and results were published by Barvainis et al. (1999). These observations have been reanalyzed using a method specifically designed for the detection of faint sources that had been applied to other clusters. Five new sources were detected and the resulting cumulative total of ten sources all have optical counterparts. The mid-infrared sources are identified with three cluster members, three foreground galaxies, an Extremely Red Object, a star and two galaxies of unknown redshift. The spectral energy distributions (SEDs) of the galaxies are fit with models from a selection, using the program GRASIL. Best-fits are obtained, in general, with models of galaxies with ongoing star formation. Infrared luminosities and star formation rates are obtained for six sources: the cluster members and the foreground galaxies. For the three cluster members the infrared luminosities derived from the model SEDs are between ∼5.7 × 10 10 L and 1.4 × 10 11 L , corresponding to infrared star formation rates between 10 and 24 M yr −1. The two cluster galaxies that have optical classifications are in the Butcher-Oemler region of the color-magnitude diagramme. The three foreground galaxies have infrared luminosities between 1.5 × 10 10 L and 9.4 × 10 10 L yielding infrared star formation rates between 3 and 16 M yr −1. Two of the foreground galaxies are located in two foreground galaxy enhancements (Boschin et al. 2004). Including Abell 2219, six distant clusters of galaxies have been mapped with ISOCAM and luminous infrared galaxies (LIRGs) have been found in three of them. The presence of LIRGs in Abell 2219 strengthens the association between luminous infrared galaxies in clusters and recent or ongoing cluster merger activity.