The Multi-Epoch Nearby Cluster Survey: type Ia supernova rate measurement in z~0.1 clusters and the late-time delay time distribution

We describe the Multi-Epoch Nearby Cluster Survey (MENeaCS), designed to measure the cluster Type Ia supernova (SN Ia) rate in a sample of 57 X-ray selected galaxy clusters, with redshifts of 0.05 < z < 0.15. Utilizing our real time analysis pipeline, we spectroscopically confirmed twenty-three cluster SN Ia, four of which were intracluster events. Using our deep CFHT/Megacam imaging, we measured total stellar luminosities in each of our galaxy clusters, and we performed detailed supernova detection efficiency simulations. Bringing these ingredients together, we measure an overall cluster SN Ia rate within R_{200} (1 Mpc) of 0.042^{+0.012}_{-0.010}^{+0.010}_{-0.008} SNuM (0.049^{+0.016}_{-0.014}^{+0.005}_{-0.004} SNuM) and a SN Ia rate within red sequence galaxies of 0.041^{+0.015}_{-0.015}^{+0.005}_{-0.010} SNuM (0.041^{+0.019}_{-0.015}^{+0.005}_{-0.004} SNuM). The red sequence SN Ia rate is consistent with published rates in early type/elliptical galaxies in the `field'. Using our red sequence SN Ia rate, and other cluster SNe measurements in early type galaxies up to $z\sim1$, we derive the late time (>2 Gyr) delay time distribution (DTD) of SN Ia assuming a cluster early type galaxy star formation epoch of z_f=3. Assuming a power law form for the DTD, \Psi(t)\propto t^s, we find s=-1.62\pm0.54. This result is consistent with predictions for the double degenerate SN Ia progenitor scenario (s\sim-1), and is also in line with recent calculations for the double detonation explosion mechanism (s\sim-2). The most recent calculations of the single degenerate scenario delay time distribution predicts an order of magnitude drop off in SN Ia rate \sim 6-7 Gyr after stellar formation, and the observed cluster rates cannot rule this out.Comment: 35 pages, 14 figures, ApJ accepte

Intracluster supernovae in the Multi-epoch Nearby Cluster Survey

The Multi-Epoch Nearby Cluster Survey (MENeaCS) has discovered twenty-three cluster Type Ia supernovae (SNe) in the 58 X-ray selected galaxy clusters (0.05 < z < 0.15) surveyed. Four of our SN Ia events have no host galaxy on close inspection, and are likely intracluster SNe. Deep image stacks at the location of the candidate intracluster SNe put upper limits on the luminosities of faint hosts, with M_{r} > -13.0 mag and M_{g} > -12.5 mag in all cases. For such limits, the fraction of the cluster luminosity in faint dwarfs below our detection limit is <0.1%, assuming a standard cluster luminosity function. All four events occurred within ~600 kpc of the cluster center (projected), as defined by the position of the brightest cluster galaxy, and are more centrally concentrated than the cluster SN Ia population as a whole. After accounting for several observational biases that make intracluster SNe easier to discover and spectroscopically confirm, we calculate an intracluster stellar mass fraction of 0.16^{+0.13}_{-0.09} (68% CL) for all objects within R_{200}. If we assume that the intracluster stellar population is exclusively old, and the cluster galaxies themselves have a mix of stellar ages, we derive an upper limit on the intracluster stellar mass fraction of <0.47 (84% one-sided CL). When combined with the intragroup SNe results of McGee & Balogh, we confirm the declining intracluster stellar mass fraction as a function of halo mass reported by Gonzalez and collaborators. (Abridged)Comment: 24 pages, 8 figures, ApJ publishe

The Canadian Cluster Comparison Project: weak lensing masses and SZ scaling relations

The Canadian Cluster Comparison Project is a comprehensive multi-wavelength survey targeting 50 massive X-ray selected clusters of galaxies to examine baryonic tracers of cluster mass and to probe the cluster-to-cluster variation in the thermal properties of the hot intracluster medium. In this paper we present the weak lensing masses, based on the analysis of deep wide-field imaging data obtained using the Canada-France-Hawaii-Telescope. The final sample includes two additional clusters that were located in the field-of-view. We take these masses as our reference for the comparison of cluster properties at other wavelengths. In this paper we limit the comparison to published measurements of the Sunyaev-Zel'dovich effect. We find that this signal correlates well with the projected lensing mass, with an intrinsic scatter of 12\pm5% at ~r_2500, demonstrating it is an excellent proxy for cluster mass.Comment: 14 pages, 5 figures, submitted to MNRA

A Giant Metrewave Radio Telescope/Chandra view of IRAS 09104+4109: A type 2 QSO in a cooling flow

IRAS 09104+4109 is a rare example of a dust enshrouded type 2 QSO in the centre of a cool-core galaxy cluster. Previous observations of this z=0.44 system showed that as well as powering the hyper-luminous infrared emission of the cluster-central galaxy, the QSO is associated with a double-lobed radio source. However, the steep radio spectral index and misalignment between the jets and ionised optical emission suggested that the orientation of the QSO had recently changed. We use a combination of new, multi-band Giant Metrewave Radio Telescope observations and archival radio data to confirm that the jets are no longer powered by the QSO, and estimate their age to be 120-160 Myr. This is in agreement with the ~70-200 Myr age previously estimated for star-formation in the galaxy. Previously unpublished Very Long Baseline Array data reveal a 200 pc scale double radio source in the galaxy core which is more closely aligned with the current QSO axis and may represent a more recent period of jet activity. These results suggest that the realignment of the QSO, the cessation of jet activity, and the onset of rapid star-formation may have been caused by a gas-rich galaxy merger. A Chandra X-ray observation confirms the presence of cavities associated with the radio jets, and we estimate the energy required to inflate them to be ~7.7x10^60 erg. The mechanical power of the jets is sufficient to balance radiative cooling in the cluster, provided they are efficiently coupled to the intra-cluster medium (ICM). We find no evidence of direct radiative heating and conclude that the QSO either lacks the radiative luminosity to heat the ICM, or that it requires longer than 100-200 Myr to significantly impact its environment. [Abridged]Comment: 23 pages, 18 figures and 7 tables. Accepted for publication in MNRA

Star formation, starbursts and quenching across the Coma supercluster

We analyse Spitzer MIPS 24micron observations, and SDSS (DR7) optical broadband photometry and spectra, to investigate the star formation (SF) properties of galaxies residing in the Coma supercluster region. We find that SF in dwarf galaxies is quenched only in the high density environment at the centre of clusters and groups, but passively-evolving massive galaxies are found in all environments, indicating that massive galaxies can become passive via internal processes. We find AGN activity is suppressed in the cluster cores. We present evidence for a strong dependence of the mechanism(s) responsible for quenching SF in dwarf galaxies on the cluster potential. We find a significant increase in the mean EW of Halpha among star-forming dwarf galaxies in the infall regions of the Coma cluster and the core of Abell 1367 with respect to the overall supercluster population, indicative of the infalling dwarf galaxies undergoing a starburst phase. We identify these starburst galaxies as the precursors of the post-starburst k+A galaxies. We find that 11.4% of all dwarf (z mag > 15) galaxies in the Coma cluster and 4.8% in the Abell 1367 have k+A like spectra, while this fraction is just 2.1% when averaged over the entire supercluster region. We show that in the centre of the Coma cluster, the (24-z) colour of galaxies is correlated with their optical (g-r) colour and Halpha emission. By analysing the projected phase space distribution of galaxies detected at 24micron in Coma, we find that the (optically) red 24 micron detected galaxies follow the general distribution of `all' the spectroscopic members, but their (optically) blue counterparts show interesting features, indicative of recent infall.Comment: 17 pages, 14 figures, accepted for publicaton in MNRA

Resurrecting the Red from the Dead: Optical Properties of BCGs in X-ray Luminous Clusters

We present measurements of surface brightness and colour profiles for the brightest cluster galaxies (BCGs) in a sample of 48 X-ray luminous galaxy clusters. These data were obtained as part of the Canadian Cluster Comparison Project (CCCP). The Kormendy relation of our BCGs is steeper than that of the local ellipticals, suggesting differences in the assembly history of these types of systems. We also find that while most BCGs show monotonic colour gradients consistent with a decrease in metallicity with radius, 25% of the BCGs show colour profiles that turn bluer towards the centre (blue-cores). We interpret this bluing trend as evidence for recent star formation. The excess blue light leads to a typical offset from the red sequence of 0.5 to 1.0 mag in (g'-r'), thus affecting optical cluster studies that may reject the BCG based on colour. All of the blue-core BCGs are located within ~10 kpc of the peak in the cluster X-ray emission. Furthermore, virtually all of the BCGs with recent star formation are in clusters that lie above the Lx-Tx relation. Based on photometry alone, these findings suggest that central star formation is a ubiquitous feature of BCGs in dynamically relaxed cool-core clusters. This implies that while AGNs and other heating mechanisms are effective at tempering cooling, they do not full compensate for the energy lost via radiation.Comment: 20 pages, 11 figures, 3 tables. Accepted to MNRAS Updated text in Introduction and Conclusion Section